TOF with pulmonary stenosis encompasses a wide spectrum of morphologic subsets that vary primarily in details of RV outflow obstruction, VSD, and aortic overriding. All four major components of TOF—RV outflow tract obstruction, VSD, overriding aorta, and RV hypertrophy—are linked embryologically. Van Praagh has advanced the concept of TOF being the result of a “monology.” The concept is that a small-volume subpulmonary infundibulum is the basic anomaly, resulting in pulmonary outflow tract obstruction (stenosis or atresia). There is a VSD because the small-volume infundibulum cannot fill the space above the trabecula septomarginalis (septal band; TSM) and the ventricular septum. The infundibular septum is malaligned anterosuperiorly above the right ventricle (compared with normal) because of failure of normal expansile growth of the infundibulum. Failure of normal expansile growth of the infundibulum means that the infundibular outflow tract floor—the infundibular septum—fails to expand in a rightward, posterior, and inferior direction, thereby helping to close the interventricular foramen. Failure of this normal morphogenetic movement of the infundibular septum results in aortic overriding. Because the infundibular septum is abnormally anterosuperiorly malaligned above the right ventricle, so too is the aortic valve, which is attached to what should be the left ventricular (LV) outflow tract surface of the infundibular septum. RV hypertrophy is a secondary response to resulting RV afterload.

Thus, Van Praagh posits that embryologically, TOF is a conotruncal malformation in which conotruncal septation is complete, but the infundibular septum is displaced. This anterior displacement is responsible for all of the morphologic characteristics of TOF: crowding of the RV outflow tract and obstruction, overriding of the aorta, anterior malalignment VSD, and RV hypertrophy.

Anderson, in contrast, argues that the “monology” concept is an oversimplification. His studies suggest two morphologic abnormalities that he considers pathognomonic for the lesion. (1) There is anterocephalad deviation of the outlet septum, but for obstruction of the RV outflow tract to occur, there must additionally be (2) an associated malformation of the septoparietal trabeculations, the muscular bars that reinforce the parietal wall of the right ventricle. The squeeze produced between the malaligned outlet septum and the abnormally arranged septoparietal trabeculations identify the morphologic entity of TOF.

Like the pulmonary valve and anulus, the pulmonary trunk is nearly always smaller than normal, and smaller than the aorta. Reduction is most marked when there is diffuse RV outflow hypoplasia. Then, the pulmonary trunk is less than half the aortic diameter and is short (see Fig. 34.6 ), directed sharply posterior to its bifurcation. It is thus largely hidden from view at operation by the prominent aorta, which also displaces the origin of the trunk leftward and posteriorly.

When the pulmonary valve is markedly tethered, the pulmonary trunk is also tethered or corseted at its commissural attachments (see Fig. 34.6 ), and it may be very angulated or kinked at this point. This is the usual mechanism of supravalvar narrowing, and it is not associated with wall thickening. Rarely, however, there may be a discrete supravalvar narrowing beyond commissural level with diffuse wall thickening.

The left pulmonary artery (LPA) is usually a direct continuation of the pulmonary trunk, with the right pulmonary artery (RPA) arising almost at right angles and close to it, but this pattern varies ( Fig. 34.7 ). Uncommonly, the distal pulmonary trunk and origin of the RPA and LPA are moderately or severely narrowed (bifurcation stenosis), and in this situation the bifurcation may have a Y shape. A Y-shaped bifurcation is more common when the ductus arteriosus is absent (see “ Aortic Arch and Ductus Arteriosus ” later in this section).

Cineangiograms after right ventricular injection showing stenoses at origins of pulmonary arteries in tetralogy of Fallot with pulmonary stenosis. (A) Stenosis at origin of left pulmonary artery (LPA) in region of ductus arteriosus, which is closed at its aortic end. (B) Stenosis at origin of LPA. This arrangement is unusual in that the LPA comes off at right angles. (C) Bifurcation stenosis. Note that, as usual, the right pulmonary artery comes off at right angles to pulmonary trunk. (D) Severe narrowing of distal pulmonary trunk. Note that first portion of LPA appears to be a continuation of pulmonary trunk.

Anomalies of the RPA and LPA are common in TOF with pulmonary atresia but uncommon in TOF with pulmonary stenosis, although any of the anomalies present in pulmonary atresia may occur in patients with pulmonary stenosis ( Table 34.2 ). Fellows and colleagues found pulmonary artery anomalies in 30% of infants having TOF with pulmonary stenosis presenting in the first year of life. In particular, proximal LPA stenosis or hypoplasia, or both, can occur when certain configurations of the ductus arteriosus are present (see “ Aortic Arch and Ductus Arteriosus ” later in this section).

Pulmonary arteries and veins beyond the hilar positions are about normal in size in most patients. ^, Intraacinar arteries are smaller than normal, and their media are thinner. In addition, lung volume, alveolar size, and total alveolar number tend to be reduced. ^,

Hypoplasia of the RV outflow tract and pulmonary arteries in patients having TOF with pulmonary stenosis is most marked centrally in the RV infundibulum and pulmonary trunk. On average, the RPA and LPA and their branches are not abnormally small. This does not deny the occasional existence of severe narrowing at the origin of the LPA or RPA (see Fig. 34.7 ). Elzenga and colleagues found juxtaductal proximal stenoses of the LPA in 10% of patients having TOF with pulmonary stenosis. There is great variability in these dimensions, however, making their careful prerepair study important.

The nearly infinitely variable spectrum of RV outflow tract obstruction in TOF can be conveniently categorized in a way that is surgically useful because it relates to difficulty in obtaining good relief of the pulmonary stenosis and therefore to surgical techniques and mortality ( Box 34.1 ). This supplements earlier discussion of patterns of the infundibular portion of the obstruction. It might be inferred that transanular patching to relieve outflow tract obstruction would be more frequently required in those with anulus stenosis or diffuse hypoplasia, but a blanket rule is probably inappropriate.

A transanular patch may later produce severe stenosis at the origin of the LPA or, less commonly, of the RPA. Important stenosis or kinking of an RPA or LPA may also be produced by an imprecise shunting operation (see “ Technique of Shunting Operations ” later in this section). The distal pulmonary artery may then become relatively hypoplastic because of poor pulmonary blood flow ( Q ˙ P).

Patients virtually always have increased collateral pulmonary arterial blood flow, primarily from true bronchial arteries. Occasionally (less than 5% of patients), large aortopulmonary (AP) collateral arteries are present. This fact makes it very important to ensure that the left heart is promptly and adequately vented when the heart is arrested at repair, to avoid deleterious ventricular distension and flooding of the pulmonary vasculature.

In classic TOF, the VSD is juxtaaortic and usually lies adjacent to or involves the membranous septum (conoventricular and perimembranous). It differs from the usual isolated VSD, however, in that it is associated with anterior malalignment of the infundibular septum (see Fig. 34.2 ) and is virtually always large and nonrestrictive. Anterior displacement (malalignment) of the infundibular septum relative to the crest of the ventricular septum creates the VSD rather than a deficiency of tissue. The infundibular septum may or may not be deficient or hypoplastic (see next paragraph), but deficiency of tissue is not necessary for the VSD to be present

The defect is more U-shaped than circular and is bounded superiorly and anteriorly by the free edge of the infundibular septum (see Fig. 34.4 ). The septum may support part or most of the right aortic cusp, depending on the degree of aorta overriding the RV (see Fig. 34.1 ). Because of the anterior and leftward deviation of the parietal end (parietal extension) of the infundibular septum, the posterosuperior angle of the defect extends higher than that of the usual isolated conoventricular VSD (see Fig. 34.2 A) and can be more difficult to expose surgically, particularly if the parietal band is not fully mobilized (transected). When the infundibular septum is hypoplastic, the defect is larger and extends closer to the pulmonary valve; when the infundibular septum is absent, the VSD becomes juxtapulmonary (and juxtaarterial).

Posterosuperiorly, the VSD is bounded by muscle (the ventriculoinfundibular fold) adjacent to the rightward edge of the noncoronary aortic cusp ( Fig. 34.8 ). This cusp may override considerably onto the right ventricle ( Fig. 34.9 ); then, the LV-aortic junction adjacent to the noncoronary cusp forms this boundary.

Specimen of tetralogy of Fallot demonstrating ventricular septal defect (VSD) and position of bundle of His. A narrow muscular bridge separates VSD from anterior tricuspid leaflet and tricuspid anulus. Right ventricle has been opened and the incision carried across infundibular septum and right coronary cusp (RC) out into the ascending aorta, as shown in Fig. 34.1 . Narrow muscular bridge separating VSD from tricuspid valve is the continuity between right posterior division of trabecula septomarginalis and ventriculoinfundibular fold (VI) . VI joins the undersurface of the parietal end of infundibular septum. Sutures can be passed safely into this ridge along dashed line (or, alternatively, in base of tricuspid leaflet), but the margin for error is small because the course of the bundle of His (dotted line) is not far removed. Note marked RV overriding of RC. IS, Infundibular septum; NC, noncoronary cusp; RP, right posterior division of trabecula septomarginalis (septal band); RV, right ventricle; T, anterior tricuspid leaflet.

Specimen of tetralogy of Fallot with right ventricle and pulmonary trunk opened with an anterior incision and infundibular septum divided to expose ventricular septal defect. Accessory prominent muscular trabeculations are present in front of septal attachment of infundibular septum (arrows) , contributing to stenosis. Pulmonary valve is bicuspid and tethered, with mild cusp thickening. Marked overriding of aorta is visible, involving rightward margin of noncoronary cusp. Ao, Aorta; IS, infundibular septum; N, noncoronary cusp; PT, pulmonary trunk; PV, pulmonary valve; TSM, trabecula septomarginalis; TV, tricuspid valve; VSD, ventricular septal defect.

The posterior margin is variable. It is related to the base of the tricuspid anteroseptal leaflet commissure and to the right fibrous trigone (central fibrous body) at the nadir of the noncoronary aortic cusp. There is tricuspid-aortic-mitral fibrous continuity at this margin, and the membranous septum is absent—characteristics of a true perimembranous VSD. In some hearts the VSD extends inferiorly beneath the tricuspid septal leaflet more than usual, described as “inlet extension” of the VSD. When there is marked clockwise rotation of the overriding aortic root, the right trigone may form the posteroinferior angle of the defect, and the bundle of His (which perforates at this point) is exposed along the edge of the defect ( Fig. 34.10 ). Occasionally the posterior margin may be formed by a remnant of fibrous tissue (membranous septum) projecting upward from the right trigone region. This tissue, also called the membranous flap , does not contain conduction tissue, and it can receive some of the sutures used to secure the VSD patch. Suzuki and colleagues found such a flap in about half of 158 TOF hearts. Kurosawa and Imai found at least a remnant in all 68 of their surgical cases. In at least 20% of hearts, the posterior margin is formed by a muscular ridge of variable size that separates the right trigone from the base of the anterior tricuspid leaflet. This ridge is formed by the right posterior division of the TSM as it becomes continuous with the ventriculoinfundibular fold ( Fig. 34.11 ; see also Fig. 34.8 ). It displaces the right trigone and therefore the bundle of His away from the defect edge.

Two specimens of tetralogy of Fallot with perimembranous ventricular septal defect (VSD), opened as in Fig. 34.8 . There is tricuspid-aortic-mitral fibrous continuity at the posterior margin (leftward in the photograph) of the VSD. (A) Right fibrous trigone at nadir of noncoronary aortic cusp has been perforated by a pin passed from right atrial side at point of penetration of bundle of His; bundle extends from this point forward and slightly leftward along margin of VSD (dotted line). White arrow points to this area. VSD patch suture line must pass into base of septal tricuspid leaflet (dashed line) and not along lower VSD margin. (B) Position of right fibrous trigone when there is important clockwise rotation of aortic root and right ventricular overriding of noncoronary and right aortic cusps. Bundle position is shown by dotted line and position of VSD suture line (passing into base of anterior tricuspid leaflet) by dashed line. IS, Infundibular septum; NC, noncoronary cusp; T, tricuspid valve.

In this heart with tetralogy of Fallot, posterior muscular bridge is bulky and entirely hides right trigone that lies several millimeters caudal and leftward of margin of ventricular septal defect. His bundle will not be damaged by sutures passed into ridge along dashed line. IS, Infundibular septum; NC, noncoronary cusp; T, tricuspid valve.

The inferior margin of the VSD is formed by the TSM as it cradles the VSD between its limbs. The papillary muscle of the conus (or corresponding chordae only) arises from the right posterior division of the TSM at the anteroinferior angle of the defect. Anomalous tricuspid chordal attachments to other margins of the defect are rare, in contrast to the situation in isolated perimembranous VSD.

The anterior margin of the VSD is formed by the leftward anterior division of the TSM as it becomes continuous with the inferior margin of the infundibular septum. When the TSM is poorly developed, the defect extends further anteriorly, and the VSD is described as having “anterior extension.”

When the infundibular septum is extremely diminutive or absent, the VSD is juxtaarterial and is described as having “outlet extension.” Posteriorly, this type of VSD is commonly separated from the tricuspid anulus by a 2- to 5-mm strip of muscle, but it may extend to the anulus. Aortic and pulmonary valve anuli are contiguous over about one-third of their circumferences, being separated at this point by only a thin fibrous ridge where the infundibular septum would have been, if present (see Fig. 34.3 ). The two valves are often side by side, with the aorta more than usually dextroposed. TOF with this type of VSD is morphologically similar to double outlet right ventricle with a doubly committed (juxtaarterial) VSD (see Chapter 45 ), with the important distinction that in TOF, fibrous continuity is maintained between the aortic valve and the central fibrous body, whereas in double outlet right ventricle there is infundibular muscle beneath the aortic valve, and thus there is fibrous discontinuity between the aortic valve and central fibrous body.

In 3% to 15% of patients (see Table 34.2 ), one or more additional VSDs coexist with the typical juxtaaortic one ( Fig. 34.12 ). Usually the additional VSD is muscular, and multiple muscular defects sometimes occur. It may also be in the inlet septum, either as an inlet septal VSD or a muscular defect (see “ Inlet Septal Ventricular Septal Defect ” under Morphology in Section I of Chapter 33 ).

Cineangiograms of tetralogy of Fallot, pulmonary stenosis, and multiple ventricular septal defects (VSD). Note large trabecular VSD near apex as well as usual conoventricular VSD. (A) Systolic frame. (B) Diastolic frame.

The sinus and atrioventricular nodes are in their normal locations (see “ Conduction System ” in Chapter 1 ), and the bundle of His follows the same general course as in patients with isolated perimembranous VSDs (see “ Location in Septum and Relationship to Conduction System ” under Morphology in Section I of Chapter 33 ). Thus, the His bundle emerges through the right fibrous trigone at the base of the noncoronary cusp of the aortic valve and courses forward toward the papillary muscle of the conus along the inferior VSD margin or slightly to the left side of the defect edge. ^, In hearts showing marked clockwise rotation of the aortic root with RV overriding, the right trigone (and along with it the penetrating portion of the His bundle) is carried more rightward and superiorly and directly onto VSD margins (see Fig. 34.10 ).

By contrast, the bundle of His does not lie on the VSD margin when a muscle ridge is present (see Figs. 34.8 and 34.11 ), because the ridge projects superiorly above the right fibrous trigone; when the ridge is bulky, sutures can be safely placed into it.

The aorta is biventricular in origin and more anteriorly placed than normal, often almost obscuring the smaller pulmonary trunk from view at operation. These changes are due to RV overriding, rotation, and enlargement of the aortic root. The proportion of aorta lying above the RV varies between 30% and 90%. Generally, about 50% of the aortic orifice is over the right ventricle.

Aortic overriding is associated with a variable degree of clockwise rotation of the aortic root (as viewed from below). This rotation moves the base of the noncoronary cusp rightward and superiorly onto the posterosuperior margin of the VSD and away from the base of the anterior mitral leaflet so that in extreme cases it may no longer be continuous with this structure. This cusp may then lie in part just beneath the extension of the infundibular septum. Rightward rotation of the left aortic cusp results in more of it becoming continuous with the anterior mitral leaflet. Simultaneously, the superiorly positioned right cusp moves to the left, and in extreme examples it may be just beneath the uppermost extension of the left anterior division of the TSM at the anterosuperior VSD margin. An important point is that, despite the degree of aortic rotation, continuity of some portion of the aortic anulus and the anterior mitral leaflet is always maintained. As a result, the VSD is always related to the aorta in TOF. The VSD may also be equally related to the pulmonary valve when the infundibular septum is absent (see “ Ventricular Septal Defect ” in this section).

Degree of overriding and clockwise rotation of the aortic root relates to degree of underdevelopment of the RV outflow tract and to deviation (malalignment) of the infundibular septum. When these are minimal, as seen with isolated low-lying infundibular stenosis, the aorta is minimally affected; when there is diffuse RV outflow tract hypoplasia in association with a small, markedly deviated infundibular septum and posterior and leftward movement of the pulmonary trunk origin, the aorta is markedly rotated and dextroposed.

In patients with severe TOF, the aortic root is larger than normal, even in infants. Occasionally in adults, it is greatly dilated. This may result in aortic valve regurgitation.

The ductus arteriosus is absent in about 30% of patients born with TOF. This does not mean a closed ductus (ligamentum arteriosum) but rather complete absence of any ductal structure. Absence of the ductus or ligamentum is about twice as common when there is a right, rather than left, aortic arch. The pulmonary artery bifurcation often takes on a Y-shaped configuration, also described as the “staghorn” or “seagull” configuration, in this setting. In the other 70% of patients in whom a ductal structure is present, it is patent at birth and closes over a normal time course unless pharmacologically maintained with PGE ₁ for therapeutic reasons (cyanosis). The configuration of the ductus can vary from normal (an extension of the pulmonary trunk, creating an arch that somewhat parallels the aortic arch and inserts into the distal aortic isthmus) to abnormal, approximating the ductus orientation seen in pulmonary atresia (arising from the LPA and inserting more proximally into the aortic arch, without forming an arch). When the RV outflow tract obstruction is mild or moderate, the ductal configuration is more normal, reflecting ductal flow from the pulmonary trunk to aorta during fetal life, and more like that in pulmonary atresia when the RV outflow tract obstruction is severe, reflecting ductal flow from aorta to pulmonary trunk during fetal life. When the ductus originates from the LPA, the short proximal segment of LPA between the pulmonary trunk and ductus may be hypoplastic, and the LPA at the ductus insertion may become stenotic or even occluded when the ductus closes (so-called LPA coarctation). Rarely, there is physical discontinuity between the LPA and pulmonary trunk, with the isolated LPA arising from the ductus or ligamentum ( Fig. 34.13 ).

Cineangiogram of tetralogy of Fallot and absence of central portion of left pulmonary artery (LPA). (A) Right ventricular injection shows lack of connection between pulmonary trunk and LPA. (B) Later phase shows that hilar portion of LPA originates from ductus arteriosus.

A left aortic arch is present in about 75% of patients. In these, arch branching pattern is usually normal.

A right aortic arch is present in about 25% of patients. In 90% of these, there is mirror-image branching of the arch. Should a patent ductus arteriosus be present, it usually arises from the brachiocephalic or proximal left subclavian artery and joins the LPA. Rarely, there may be a right-sided ductus arteriosus to the RPA, usually arising from the upper descending thoracic aorta. In about 10% of patients, there is an aberrant left subclavian artery, analogous to the aberrant right subclavian artery of dysphagia lusoria in left aortic arch (see “ Right Aortic Arch with Aberrant Left Subclavian Artery ” in Section I of Chapter 39 ). In right aortic arch with aberrant left subclavian artery, the subclavian artery may arise directly from the descending aorta or from an aortic diverticulum. Thus, a ductus arteriosus may arise from the aortic diverticulum and pass to the left behind the esophagus to join the LPA.

Rarely, the left subclavian artery is sequestered or isolated from its aortic arch origin but remains connected to the LPA by a patent ductus arteriosus. Often in these circumstances, there is vertebral steal, and on angiography the subclavian artery fills with contrast from the vertebral artery.

External dimensions of the sinus (inflow) portion of the right ventricle are larger than normal due to hypertrophy, so the interventricular groove is displaced leftward, and the left ventricle lies more posteriorly than usual (clockwise rotation of ventricles). The RV sinus may be clearly separated from the infundibulum during systole by a transverse depression representing the site of maximal infundibular stenosis inferior to an infundibular chamber. RV wall thickness equals that of the left ventricle and is therefore never excessive unless the large VSD is made restrictive by a fibrous flap valve on its right side (see Section IV ). Normal trabeculations are, however, bulky and prominent. Right ventricle end-diastolic volume may be reduced and ejection fraction mildly depressed, typically in older children without TOF repair, possibly the result of chronic hypoxia. Rarely (1.5% of cases), the sinus portion of the right ventricle and tricuspid valve are underdeveloped (see Table 34.2 ).

The left ventricle is usually normal in wall thickness but variable in volume. In patients with severe forms of TOF with severe cyanosis, left ventricle end-diastolic volume is normal or somewhat small, ^, but wall thickness remains normal. Uncommonly, the left ventricle and mitral valve are truly hypoplastic, and rarely this may be so severe (end-diastolic volume <30 mL · m ⁻² ) as to contraindicate primary repair. ^,

The physiologic contributors to LV size are complex. The small pulmonary and thus left atrial blood flow tend to result in a small left atrium ^, and left ventricle. However, the right ventricle ejects blood into the left ventricle as well as the aorta, and this tends to increase LV size. Mild or moderate degrees of LV hypoplasia may result from these physiologic factors, but true hypoplasia is of morphologic rather than functional origin.

LV systolic function is normal at birth but may become mildly reduced in older patients who have not undergone repair, particularly in severely cyanotic patients, presumably because of chronic hypoxia.

As in other cyanotic conditions, the coronary arteries become dilated and tortuous in children and adults. A large conal branch of the right coronary artery (RCA) usually courses obliquely across the free wall of the right ventricle, and the presence of this vessel should be noted at the time of surgical repair.

The left anterior descending coronary artery (LAD) arises anomalously from the RCA in about 5% of patients ( Table 34.3 ). ^, The entire LAD may originate from the RCA and cross the anterior wall of the infundibulum a variable distance from the pulmonary valve, or only the distal part of the LAD may arise anomalously, in this case usually from the large conal branch of the RCA.

Rarely, the RCA originates from the left coronary artery, and equally uncommonly there is anomalous origin of the left coronary artery from the pulmonary trunk (see Section II of Chapter 38 ).

Major associated cardiac anomalies are relatively uncommon (see Table 34.2 ). Patent ductus arteriosus, multiple VSDs , and complete atrioventricular septal defect are most often seen.

Rarely, the RPA or LPA arises anomalously from the ascending aorta (see Chapter 42 ). This complicates the pathophysiology and repair, because the lung supplied by the pulmonary artery arising from the aorta usually has overcirculation, and the other usually has restricted flow due to the intracardiac anatomy.

Infrequently, aortic valve regurgitation coexists. This may be from typical cusp prolapse in TOF with subarterial VSD (see Section II in Chapter 33 ). A bicuspid aortic valve occurs rarely in TOF and may result in aortic regurgitation. ^, Occasionally, ill patients with TOF in the second decade of life or older develop aortic regurgitation from endocarditis. ^, Massive dilation of the aortic root from anuloaortic ectasia may result in aortic valve regurgitation, particularly in patients with large natural or surgically created systemic–pulmonary arterial shunts.

Most infants undergoing repair of TOF have a patent foramen ovale (PFO); when all ages are considered, a true atrial septal defect is found at operation in about 10%. Other minor associated cardiac anomalies are listed in Table 34.3 .

The hallmark clinical sign of TOF is cyanosis. The severity of cyanosis and its variability depend on the specific morphology of the RV outflow tract. Infants with diffuse RV outflow hypoplasia, severe infundibular plus valvar plus anular stenosis, or severe infundibular plus valvar stenosis (see Box 34.1 ) are deeply cyanotic from birth and do not develop heart failure. They are breathless on feeding or other exertion. Hypoxic spells are rare, the cyanosis being constant and gradually worsening. It is seldom lessened by propranolol.

This situation contrasts with that in infants having dominant infundibular stenosis, in which onset of cyanosis is delayed and hypoxic (cyanotic) spells due to infundibular spasm may occur. These spells are often prevented or lessened in frequency by propranolol. Characteristically, they become less frequent with age, presumably because stenosis becomes fixed as a result of acquired endocardial fibrosis and thickening.

In up to 10% of patients who require surgical relief in infancy, presentation is initially as a large VSD with pulmonary plethora and sometimes heart failure at age 2 to 3 months, followed by gradually increasing cyanosis, frequently with cyanotic spells, at about age 6 months. In this group, stenosis is purely infundibular.

A minority of patients are acyanotic at rest and only mildly cyanotic during exercise because pulmonary stenosis is mild and right-to-left shunting minimal. In some the shunt is predominantly left to right. These individuals may remain acyanotic without spells and present at any age within the first or second decades of life with gradually increasing cyanosis and breathlessness as stenosis slowly increases in severity.

In patients with severe cyanosis and polycythemia, cerebral thrombosis may precipitate hemiplegia at any age (particularly in association with dehydration), or hemiplegia may follow paradoxical embolism or a brain abscess. The latter is heralded by fever, headache, and sometimes seizures. Massive hemoptysis may occur in older patients who are severely cyanotic, presumably from rupture of bronchial collateral vessels.

Cyanosis is always accompanied by effort dyspnea that is sometimes the dominant symptom, and as the child begins to walk (frequently much later than for a healthy child), cyanosis is often accompanied by squatting, which lessens its severity. There may be increased occurrence of respiratory infection but not to the same extent as in patients with large isolated VSD; failure to thrive is also less striking.

Cyanosis of variable degree is generally evident. Deeply cyanotic infants are often obese (in contrast to infants with isolated VSD). Severe symmetric clubbing of the fingers and toes is often present in children and adults but not in infants. Older patients may also have marked acne of the face and anterior chest. Jugular venous pressure is normal. The heart is not enlarged and is relatively quiet with an unimpressive RV lift. In those few patients with increased pulmonay blood flow, the lift may be more marked than usual.

A precordial systolic thrill is rare. There is a moderately intense midsystolic pulmonary (ejection) murmur maximal in the second and third left intercostal spaces that becomes less prominent or even disappears when the stenosis is severe. When there is still a reasonable blood flow in the presence of moderate pulmonary stenosis, the systolic murmur is well heard posteriorly and in the axilla. In the presence of important cyanosis and decrease pulmonary blood flow the second heart sound is single, but in acyanotic patients it may be finely split with a low-intensity pulmonary component. Splitting is also present in moderately cyanotic patients with only a mildly reduced pulmonary blood flow when there are important pulmonary artery origin stenoses.

Signs of heart failure with venous pressure elevation and liver enlargement occur in patients with a systemic-to–pulmonary arterial shunt that is too large or in a neonate on PGE ₁ to maintain ductal patency. Heart failure may also appear in untreated severely cyanotic adults in the fourth or fifth decade of life, presumably secondary to myocardial fibrosis or in association with systemic hypertension or aortic regurgitation.

Neonates or young infants who have severe TOF with pulmonary stenosis usually present with marked reduction of arterial oxygen pressure (Pao ₂ ) and saturation (Sao ₂ ) and sometimes with metabolic acidosis. Polycythemia is rarely present, and, in fact, such infants are often anemic.

In older infants and children, red blood cell count and hematocrit are usually elevated, and degree of elevation is correlated with degree of arterial desaturation and thus with severity of the pulmonary stenosis. In older patients, hematocrit may reach 90%.

Most cyanotic patients have depressed platelet count and prolongation of most coagulation tests.

Chest radiographs in children usually show the typical boot-shaped heart of TOF. In neonates and young infants the heart may be strikingly small, with an absent pulmonary artery segment along the left upper cardiac border and oligemic lung fields. In older patients, there may be a prominence of the left upper cardiac border caused by a large infundibular chamber. Large AP collaterals may alter the pulmonary blood flow pattern in one or both lungs. Plethora of one lung and oligemia of the other suggest anomalous origin of a pulmonary artery from the ascending aorta (see Chapter 42 ).

If there is a right aortic arch, posterior indentation of the shadow of the barium-filled esophagus results from an aberrant left or right subclavian artery.

Rib notching of the upper ipsilateral ribs may develop in the presence of a long-standing classic Blalock-Taussig (BTT) shunt, secondary to development of a rich collateral blood flow to the arm. This situation is rarely encountered in the current era because the classic B-T shunt is not commonly performed. Presumably, the same pathophysiology could develop after a modified B-T shunt if the subclavian artery were severely stenotic or occluded. Rarely, collaterals from the pleura to the lung may be sufficiently large, especially after poudrage or pleural stripping procedures, to result in bilateral rib notching in the lower half of the thorax. Patients in the second or third decade of life may show progressive kyphoscoliosis.

Electrocardiography (ECG) shows moderate RV hypertrophy consistent with RV pressure that is equal to but not greater than systematic pressure (in contrast to flap valve VSD). Occasionally, there is minimal RV hypertrophy, and in these circumstances, RV underdevelopment should be suspected, although it may not be present. Left precordial leads are characterized by absent Q waves and low-voltage R waves. Occasionally the frontal plane vectorcardiographic pattern characteristic of atrioventricular septal defect is found in patients with typical TOF.

Echocardiography is considered the definitive diagnostic procedure of choice in neonates and infants. ^, The VSD, atrial septal status, aortic overriding, narrowing of the RV infundibulum, pulmonary valve, pulmonary trunk and bifurcation into the branch pulmonary arteries, and the ductus arteriosus, if present, can usually be seen with ECG ( Fig. 34.14 ). Also, in experienced hands, two-dimensional (2D) echocardiography with Doppler color-flow interrogation has the same sensitivity and specificity for multiple VSDs in TOF as does cineangiography. However, morphologic details of distal pulmonary artery branches as they approach the hilum may not be reliably visualized. Additional imaging is indicated when important abnormalities of the branch pulmonary arteries are identified, such as hypoplasia, discontinuity, or stenosis, and when abnormal arterial signals on Doppler interrogation are identified in the central and posterior mediastinum, suggestive of major AP collaterals.

Echocardiograms of tetralogy of Fallot. (A) Subxiphoid view. Narrowed right ventricular (RV) outflow tract due to infundibular hypertrophy (arrow) and anterior malalignment of infundibular septum. (B) Parasternal short-axis view. Narrowed RV outflow tract due to infundibular hypertrophy (thin arrow). Pulmonary anulus and area distal to it are narrowed as well (thick arrow). (C) Sagittal view from subxiphoid position. Overriding aorta is demonstrated. (D) Parasternal long-axis view. Aorta is overriding interventricular septum and ventricular septal defect is imaged. Ao, Aorta; AV, aortic valve; IVS, interventricular septum; LPA, left pulmonary artery; LV, left ventricle; PT, pulmonary trunk; RA, right atrium; RPA, right pulmonary artery; RVOT, right ventricular outflow tract.

Color Doppler imaging can also provide important physiologic information. Accurate estimates of the severity of obstruction across the RV outflow tract, as well as the site of obstruction (infundibular, valvar, supravalvar), can be obtained. Flow characteristics across the VSD and LV outflow tract can be used to confirm that pressures in the right ventricle and left ventricle are equal. Systolic function of the ventricles and competency of the inlet valves are also easily assessed, and flow patterns across the inlet valves in diastole can provide important information about ventricular diastolic function. In most cases the coronary artery pattern can be characterized, and anomalous patterns, such as the LAD arising from the RCA, can be identified.

Newer modalities of echocardiography, such as 3D echocardiogram, tissue Doppler, and strain rate imaging, hold further promise as noninvasive tools for improved morphologic and functional evaluation. Echocardiography can effectively diagnose TOF in the fetus and can be helpful in planning early surgical intervention and parental counseling.

In patients who have undergone operation for TOF, whether palliative procedures or definitive repair, and in unoperated TOF patients presenting well beyond infancy, echocardiography is an important part of the diagnostic workup; however, it is not definitive. Characterizing pulmonary vascular resistance (Rp), if needed, requires cardiac catheterization. Imaging the distal pulmonary arteries used to also require cardiac catheterization and angiography, but, in the current era, this can be accomplished by MRI or computed tomography.

Preoperative cardiac catheterization and angiography, although not routinely required when expertly interpreted echocardiography is available, precisely portray the hemodynamic state and morphology, particularly that of the distal pulmonary arteries. Peak pressure in the RV cavity (Prv) is similar to that in the left (Plv), and pulmonary artery pressure (Ppa) is below normal. A systolic pressure gradient is demonstrable at infundibular and valvar levels when both zones are stenotic but rarely at a more peripheral site. When proximal stenoses are severe, however, it may be impossible to enter the pulmonary trunk with a catheter.

There is right-to-left shunting at ventricular level and decreased pulmonary blood flow, the severity of which reflects severity of stenosis. In acyanotic patients, there is minimal right-to-left shunting at rest or even a slight increase in pulmonary blood flow, but in most patients, right-to-left shunting occurs on exercise. In severely cyanotic patients, Ppa and Rp are not elevated preoperatively, even in the presence of important peripheral pulmonary artery stenosis or thrombosis, because of low pulmonay blood flow. Ppa may be elevated when there is a large pulmonary blood flow and an increase in Rp.

Biplane cineangiography demonstrates all the morphologic features of the malformation as well as morphology and dimensions of the right ventricle–pulmonary trunk junction, pulmonary trunk, and RPA and LPA and their branches. Oblique and angled views ^, are used. Configuration of the RV sinus and infundibulum and degree and morphology of the RV outflow tract obstruction are studied. Morphology of the pulmonary valve and any tethering or narrowing of the pulmonary trunk at the level of the commissural attachments of the valve or beyond are noted. Bifurcation of the pulmonary trunk and origins of the LPA and RPA are studied with particular care because the surgeon cannot accurately assess presence or severity of stenoses in this area during operation. The sitting-up position (cranially tilted frontal view) generally offers the best view, although oblique views also usually demonstrate origins of both pulmonary arteries. Presence, size, and morphology of various portions of the RPA and LPA are studied with care.

With proper profiling of the ventricular septum, the typical large VSD and overlying dextroposed aorta are identified (see Fig. 34.12 ). Additional VSDs, if present, are identified as well.

Coronary arterial anatomy can usually be seen following LV injection. Particular search is made for anomalous origin of the LAD from the RCA and for the rare but surgically important associated origin of the left coronary artery from the pulmonary trunk.

Follow-through frames are examined for evidence of large AP collateral arteries, and injection is made into the thoracic aorta and/or selectively into the collateral arteries if these are present. When the true LPA or RPA is not visualized following these injections, which must include late filming and sometimes also digital subtraction techniques, a pulmonary vein wedge injection is made to fill (retrogradely) the pulmonary arterial tree ( Fig. 34.15 ). ^, When all techniques including this one fail to outline a central or hilar portion of a pulmonary artery, it can be safely assumed to be absent.

Pulmonary vein wedge injection in tetralogy of Fallot and absent central portion of left pulmonary artery demonstrating a left hilar pulmonary artery and its normal continuation. The artery was not visualized by right ventricular or aortic injection.

Any major associated cardiac anomalies are identified by the study. Previous palliative shunts or transanular patches are visualized, the former by selective injections if necessary. Any iatrogenic pulmonary arterial problems are defined in detail.

Computed tomographic angiography (CTA) is used selectively in TOF, both in neonates and infants, as a preoperative diagnostic test and in patients after palliative surgery or reparative surgery. It can define the branch and peripheral pulmonary arteries accurately and has replaced conventional angiography for many clinical indications ( Fig. 34.16 ). The chief advantage is that it requires only peripheral intravenous access for contrast injection, thereby removing the risk of catheter-induced complications. Furthermore, CT images are 3D and amenable to image postprocessing ( Fig. 34.17 ), whereas images from conventional angiography are projectional and overlapping vessels can be difficult to interpret. Conventional angiography has better spatial resolution, and selective branch injections may reveal flow dynamics in collateral branches better than CTA.

(A) Short-axis computed tomographic angiography of a 2-week-old boy with tetralogy of Fallot shows aorta overriding ventricular septum. Right ventricle (RV) and left ventricle (LV) communicate through a malaligned ventricular septal defect (VSD) . Because the VSD is unrestrictive, RV pressure equalizes with LV pressure, promoting hypertrophy. (B) Oblique image of the same 2-week-old boy shows a small pulmonary trunk compared with aorta. Both the RV outflow track and pulmonary valve are small. Therefore, the pulmonary stenosis found in a tetralogy of Fallot has supravalvar, valvar, and subvalvar components. Ao, Aorta; PT, pulmonary trunk; RVOT, right ventricular outflow tract.

Volume-rendered computed tomographic angiography image of a 3-year-old girl with tetralogy of Fallot. Pulmonary trunk and right and left pulmonary arteries are small. Left anterior descending coronary artery abnormally arises from right coronary artery and cuts across (arrows) right ventricular outflow tract (RVOT) . Disruption of left anterior descending coronary artery during RVOT augmentation can cause left ventricular infarction. L, Left; R, right; T, pulmonary trunk.

At the present time, when echocardiography is not sufficient to allay concerns about peripheral pulmonary artery abnormalities, CTA may be indicated to clarify the morphology, instead of cardiac catheterization. The decision to use conventional versus CTA is partly based on institutional expertise and preference; however, if hemodynamic information is required, or if major AP collaterals are suspected, catheterization is necessary.

In neonates and infants with suspected branch pulmonary artery abnormalities on echocardiography, in whom there is usually little concern about abnormal Rp, CTA is an excellent method for defining pulmonary artery stenoses and arborization abnormalities. In patients with systemic to pulmonary artery shunts, in whom concerns about Rp abnormalities are not present, CTA can define the morphologic details of the peripheral pulmonary arteries, systemic-pulmonary collateral vessels, and their pulmonary distributions. Cardiac-gated CTA can also reveal unanticipated coronary artery anomalies associated with TOF (see Fig. 34.17 ). In postrepair TOF patients with residual RV outflow tract abnormalities, CT can accurately characterize the morphology from the infundibulum to the peripheral pulmonary arteries and help detect native stenosis and conduit stenosis ( Fig. 34.18 ) and aneurysm or pseudoaneurysm ( Fig. 34.19 ).

Volume-rendered computed tomographic angiography image of a 2-year-old boy who had a complete repair for tetralogy of Fallot with a right ventricle–to–pulmonary trunk conduit (arrow) and branch pulmonary artery reconstruction. Patient has outgrown original conduit and has proximal right pulmonary artery stenosis and requires pulmonary arterial reconstruction and conduit replacement.

Computed tomographic angiography oblique image of a 2-year-old girl shows rupture of pulmonary conduit at its distal anastomosis, forming a large pseudoaneurysm. A, Aneurysm; PA, pulmonary conduit.

Magnetic resonance imaging (MRI) is also used selectively in TOF. ^, Generally speaking, CTA has higher spatial resolution than MRI, and therefore CT is preferred when finely detailed peripheral pulmonary vascular morphologic information is required. MRI can accurately define the anatomy of the RV outflow tract and branch pulmonary arteries ( Figs. 34.20 and 34.21 ). MRI has the advantage that it does not use ionization radiation and is a good choice in larger patients and when repeated studies are anticipated. In neonates and infants, preoperative echocardiography is usually adequate, and MRI is rarely indicated.

Axial image of central pulmonary arteries from contrast-enhanced magnetic resonance angiography of a 10-year-old boy who had a repaired tetralogy of Fallot showing a focal stenosis at origin of right pulmonary artery (arrow).

Bright-blood, steady-state free-precession magnetic resonance oblique image of a 6-year-old girl showing large rupture at outflow tract region of right ventricle that forms a pseudoaneurysm. Neck of aneurysm is below pulmonary valve (arrow). A, Aneurysm; RV, right ventricle.

The major indication for MRI is in postrepair TOF patients with chronic pulmonary regurgitation. ^, RV volume, pulmonary valve regurgitant fraction, coexisting pulmonary stenosis(es), differential pulmonary blood flow, and tricuspid valve regurgitant fraction can all be assessed quantitatively ( Fig. 34.22 ). Serial examinations can accurately define trends in the values of these variables over time, and these trends can be helpful in determining the timing of reoperation. RV end-diastolic volume greater than 150 mL · m ⁻² in children has been identified as a threshold above which the right ventricle is likely not to normalize its volume even after placement of a pulmonary valve prosthesis. ^,

Right ventricular outflow tract cardiovascular magnetic resonance study of a patient with repaired tetralogy of Fallot with important late pulmonary regurgitation. (A) Cine image. Red dotted line illustrates through-plane in which a non–breath-hold phase encoded velocity map was acquired. (B) Flow curve obtained from same patient. Through integrating areas containing forward and reverse flow, a pulmonary regurgitation fraction of 34% was calculated.

(From Shinebourne EA, Babu-Narayan SV, Carvalho JS. Tetralogy of Fallot: from fetus to adult. Heart . 2006;92:1353-1359.)

When pacemakers or defibrillators are present, MRI is generally contraindicated, unless newer MRI compatible pacemaker systems have been implanted . ^, Under these conditions, CTA can be an excellent alternative.

Twenty-five percent of surgically untreated infants die in the first year of life but uncommonly in the first month ( Fig. 34.23 A and B). These are the patients with the most severe obstruction to pulmonary blood flow. Forty percent are dead by age 3, 70% by age 10, and 95% by age 40. Instantaneous risk of death (hazard function) is greatest in the first year of life ( Fig. 34.23 C). Risk then stays constant until about age 25, when it begins again to increase.

Natural history of surgically untreated patients having tetralogy of Fallot with pulmonary stenosis or pulmonary atresia. (A) Survival to age 60 years. Smooth lines represent survival of each group, and dashed lines enclose 70% confidence limits. (B) Survival to age 10 years (expanded time scale). (C) Hazard function according to age.

(From Bertranou EG, Blackstone EH, Hazelrig JB, Turner ME, Kirklin JW. Life expectancy without surgery in tetralogy of Fallot. Am J Cardiol . 1978;42:458.)

Hypoxic spells in the first few years of life are related to hyperactivity of the infundibulum. This and contraction of the infundibular septum and its parietal extension earlier in systole than in normal subjects produce variable and sometimes severe episodes of RV outflow tract obstruction and symptoms. Any sudden reduction of systemic vascular resistance also may precipitate a hypoxic spell.

About 25% of patients are acyanotic at birth and become cyanotic in the ensuing weeks, months, or years as pulmonary stenosis increases. ^, Progression of arterial desaturation, cyanosis, and polycythemia is variable and is furthered not only by increasing pulmonary stenosis but also by widespread tendency to thrombosis of the smaller pulmonary arteries, with progressive reduction in Q ˙ p. ^, As part of this same tendency, death may result from cerebral thromboses or abscesses.

In those few patients surviving into the fourth and fifth decades of life, death is commonly from chronic heart failure due to secondary cardiomyopathy that results from RV pressure overload and chronic hypoxia and polycythemia.

In severely cyanotic and polycythemic patients, diffuse pulmonary arterial thrombosis can occur. This is initially visible only microscopically, but rarely it progresses to occlusion of a lobar pulmonary artery or even an entire RPA or LPA. Usually, Rp is not importantly increased by this process, but rarely the thrombosis is so widespread and severe as to be a cause of immediate and sometimes fatal pulmonary hypertension and RV failure following repair.

Pulmonary vascular disease rarely develops in surgically untreated patients. It may develop following too large a systemic to pulmonary arterial shunt (see “ Interim Results After Classic Shunting Operations ” later in this section). When a surgical shunt appears to be the cause, it is possible that preexistent pulmonary arterial thrombosis has compounded the problem.

Offspring of a parent who has TOF are more likely to have the anomaly than offspring of parents without congenital heart disease. It is estimated that about 0.1% of live births have TOF under the latter circumstances and about 1.5% under the former.

As a general principle, visible-to-the-eye RV coronary artery branches should be preserved whenever possible. Occasionally visible branches must be transected to achieve acceptable RV outflow obstruction relief. This should be rarely necessary in the transatrial–transpulmonary repair technique, in which the incision across the anulus onto the infundibulum is of very limited length but is more likely to be necessary in the transventricular approach, in which the ventricular incision encompasses at least the length of the infundibulum and extends onto the free RV wall.

Before transecting a branch, its course should be fully examined. Those that traverse the body of the right ventricle, and even those smaller branches that supply muscle farther down on the RV infundibulum than the lower margin of the infundibular incision, should be preserved. When necessary, small transverse infundibular branches, with distal perfusion that stays above the lower margin of the infundibular incision, can be sacrificed.

When an anomalous LAD arises from the RCA, ^{, , ,} special attention to RV outflow tract management is necessary to avoid potentially fatal damage to the anomalous vessel. Key factors to consider are the exact course of the coronary artery, its proximity to the anterior pulmonary valve anulus, and morphology of the infundibulum. In most cases with low infundibular obstruction and a well-developed distal infundibular chamber, the obstruction can be best addressed transatrially without endangering the anomalous LAD; usually, the anomalous LAD courses obliquely across the infundibulum toward the interventricular groove, deviating laterally from the position of the pulmonary anulus. Thus, the VSD being closed transatrially, if needed, a “mini” transanular incision of only a few millimeters can be performed, stopping short of the LAD. This, in combination with transatrial and transpulmonary muscular resection in the infundibulum may well be sufficient for adequate relief of right ventricular outflow tract obstruction (RVOTO). ^, On the other hand, when severe diffuse infundibular hypoplasia is present and the obstruction can be addressed only by placing a conduit from the right ventricle to the pulmonary trunk, the RV-conduit anastomosis should be placed proximal to the coronary vessel. A valveless conduit constructed in part from a main pulmonary artery down-turned flap may be considered in small patients to obviate use of a prosthetic tube.

Tchervenkov and associates published their experience with a series of 20 consecutive neonates and infants with anomalous coronaries across the obstructed RVOT undergoing primary repair. There were no early or late deaths and only two reoperations during a follow-up of 5.2 years. They were able to reconstruct the RVOT without a conduit in 18 patients using a variety of techniques, such as main pulmonary artery translocation, transanular repair under a mobilized LAD and displaced ventriculotomy with subcoronary suture lines.

More recently, Benjaout and associates reported their experience with 14 children with a median age of 50.3 months, undergoing repair using the technique of RVOT enlargement under a mobilized anomalous LAD without coronary injury, with only one patient receiving a conduit.

Occasionally the anomalous LAD is intramyocardial. This should be suspected when the left aortic sinus gives rise to an isolated circumflex coronary artery.

To guide the decision regarding the surgical management in TOF patients with anomalous LAD origin from the RCA, the AATS Expert Consensus Document on the Management of Infants and Neonates with TOF states that :

“When a transanular repair would otherwise be necessary, in the presence of an anomalous coronary artery crossing the RVOT, either a coronary artery sparing ventricular incision or an RV to pulmonary artery conduit may be reasonable approaches based on institutional expertise (Class: IIb, LOE: C-EO).”

In children and adults, the VSD is closed with a filamentous polyester or occasionally a PTFE patch; in neonates and infants, glutaraldehyde-treated pericardium works well. The patch is trimmed to be slightly larger than the VSD.

In the transatrial approach, exposure is facilitated by stay sutures and two curved retractors through the tricuspid anulus, one pulled in the direction of the infundibulum and the other gently elevating the anterior tricuspid anulus.

In the transventricular approach, the VSD is exposed through the right ventriculotomy by the assistant using two small, curved retractors, one beneath each side of the infundibular septum, which are pulled gently upward and apart. A third retractor is positioned in the lower margin of the ventriculotomy for gentle inferior traction. Appropriately placed stay sutures on the lateral edges of the ventriculotomy reduces the need for multiple retractors.

Sequencing of the suturing depends on whether the repair is from the right atrium or RV and is similar to that used for isolated VSD (see Figs. 34.26 through 34.29 ; see also Chapter 33 ). For example, through the right ventricle it is usual to begin the continuous suture at the base of the tricuspid septal leaflet at the posterior-inferior aspect of the VSD.

Via the right atrial approach, the suture is often begun anterior to the insertion of the medial papillary muscle (muscle of Lancisi), if a running technique is used. In the interrupted suture technique, the first suture is usually placed through the tricuspid anulus near the border between the VSD and the tricuspid anulus, thereby also retracting the commissure between the anterior and septal tricuspid leaflets. Successive sutures are then placed first cephalad, until the ventricular infundibular fold is reached, taking care for the needle to penetrate the aortic anulus for secure hold but avoid damaging the aortic valve cusps. The latter are readily visible due to the aortic override. The remaining sutures are then placed counterclockwise, each suture facilitating exposure and placement of the next one.

Careful attention to the tricuspid valve during VSD closure is essential, particularly in small infants. Tethering of the septal leaflet and distortion of chordal structures during VSD closure is sometimes inevitable. Valve competency should be tested routinely after VSD closure. If regurgitation is present, tricuspid valve repair should be performed. Partial closure of the anterior septal leaflet commissure is usually effective in restoring tricuspid valve competency when septal leaflet tethering is present. A competent tricuspid valve is critical to achieving excellent outcome, especially if a transanular patch is used.

The question of whether to use a transanular patch arises in many cases, and this decision is now known to have far-reaching implications for long-term outcome. Multiple publications continue to emphasize the detrimental effects of large transanular incisions. ^{, ,} A transanular patch creates obligatory pulmonary regurgitation, and when this is long-standing and severe, important RV dysfunction will inevitably occur (see “ Results ” later in this section). The techniques to mitigate the degree of pulmonary regurgitation are discussed in the next section.

Degree of narrowing of the anulus can be expressed quantitatively by a z-value—that is, the number of standard deviations (usually smaller) from normal, based on body surface area (see Appendix figure ). It must be emphasized that the z-value is used only as a guideline in the context of various efforts and protocols to preserve pulmonary valve function as much as possible. The pulmonary valve cusp configuration—number, thickness, and fusion—will also influence the eventual gradient across the RV outflow tract after repair, and because of these variables, different gradients may result despite similar z-values.

Preoperative imaging, usually by echocardiography and occasionally by cineangiography, is used to estimate the diameter of the pulmonary anulus, and this information is used to assess the likelihood of whether a transanular patch will be necessary. In extreme cases (of both large and small anuli), this measurement can be highly predictive of whether or not a transanular patch will be needed. When the z-value has been determined from echocardiography, corrected and transformed cineangiographic measurements, or MRI or CTA to be larger than −3, the surgeon’s bias should be that a transanular patch is probably unnecessary ( Fig. 34.24 ); when it is −3 or smaller, a patch is probably required. This is based on the high probability under the circumstances of a z-value > −3 that the postrepair P _RV/LV will be less than about 0.7, and on the anticipated increased need for insertion of a pulmonary valve late postoperatively when a transanular patch has been placed. In less extreme cases (z-values between −2 and −4), intraoperative information will be used to decide when to place a transanular patch. When the patient has TOF with subarterial or doubly committed VSD, the “Asian” variant of TOF, the surgeon’s bias is that there is a three in four chance a transanular patch will be necessary.

Of note, the surgeon’s bias should also be that even with a transanular patch, when the z-value of the anulus is less than −7 (<10% of cases), postrepair ratio of peak pressure in the right ventricle to that in the left ventricle (P _RV/LV ) may be 1 or higher, even with a properly placed transanular patch ( Fig. 34.25 ). It can be inferred from the findings outlined in Fig. 34.24 that the extremely small pulmonary valve anulus may in some cases be associated with diffuse hypoplasia of the distal pulmonary arteries. Thus, when a very small anulus is noted, preoperative evaluation of the distal pulmonary vasculature and Rp should be undertaken. If distal hypoplasia, elevated Rp, or both are observed, a reparative operation should be avoided (at least temporarily) in favor of a palliative procedure.

Reassessment after closing the VSD is accomplished by estimating the diameter of the anulus with a Hegar dilator that passes snugly but not tightly through it in the relaxed heart. This provides one more precise estimate in borderline situations. This diameter is transformed to a z-value as described in Chapter 1 ; generally, this finding is similar to that obtained from the cineangiogram (but slightly smaller when the body surface area of the patient is less than 0.7 m ² and slightly larger in patients with a body surface area greater than about 0.7 m ² ). Generally, as discussed above, a transanular patch should not be placed when the z-value is larger than −3. Otherwise, the incision is carried across the anulus, limiting the extent of this incision to a few millimeters, just enough to achieve the desired size. In practice, in most cases the diameter to be achieved should be one that admits a Hegar dilator sized at mean normal diameter plus 2 or 3 mm. After this, the transanular patch is inserted ( Fig. 34.31 ). Although some advocate excision of the valve leaflets in this situation, they may well be preserved, as they may be useful to limit regurgitation, especially in combination with additional valve function preservation maneuvers, such as leaflet augmentation or placement of a monocusp valve (see below). If the situation is borderline, the lesser risk lies with inserting a transanular patch.

Use of transanular patch in repair of tetralogy of Fallot with pulmonary stenosis. (A) Entire incision is made initially when a transanular patch is clearly indicated; otherwise, only a partial incision is made (inset). Note that incision extends beyond narrowest portion of pulmonary trunk, but only a short distance onto right ventricle. Pulmonary valve is excised completely and ventricular septal defect (VSD) repaired. (B) A double-velour woven polyester (or polytetrafluoroethylene or pericardium) patch is trimmed to appropriate size and shape. When a polyester tube is used, it is elongated slightly by traction and cut to the correct length. It is then cut in half longitudinally and the ends trimmed. Note that distal end remains essentially square, with only corners trimmed off. When inserted, it forms a roof that is convex in all directions (inset).

When a transanular patch is used, a major consideration is the distal extent of the incision in the pulmonary trunk, because this must be into an area of distinctly greater diameter than that of the anulus, which is usually the narrowest area ( Fig. 34.32 ). Otherwise, a transanular patch relieves only the small component of the high resistance produced by the length of the narrowing, and the gradient will persist essentially unchanged and be at the junction of the patch and distal pulmonary trunk. In some patients, the distal pulmonary trunk is narrower than the anulus, especially when enlarged by TAP; in these cases, the incision is extended into the LPA, which usually continues in the same general direction as the pulmonary trunk and is usually proportionally larger than the distal pulmonary trunk. If the origin of the LPA is proportionally no larger than the distal pulmonary trunk, the incision and patch reconstruction should be carried into the midportion of the LPA, which is nearly always wider than the origin. Care must be taken to not damage the left phrenic nerve or left superior pulmonary vein. In neonates with a patent ductus, especially if they are on PGE ₁ , it is difficult to assess the proximal LPA, and patching that extends beyond the ductus onto the distal LPA should be performed.

Scattergram illustrating relation between diameters of right ventricular–pulmonary trunk junction and those of distal portion of pulmonary trunk in patients having tetralogy of Fallot with pulmonary stenosis. In some patients with an anular z-value of −4 or smaller, the distal pulmonary trunk is narrower than the anulus. PT, Pulmonary trunk; RV, right ventricular.

(From Shimazaki Y, Blackstone EH, Kirklin JW, Jonas RA, Mandell V, Colvin EV. The dimensions of the right ventricular outflow tract and pulmonary arteries in tetralogy of Fallot and pulmonary stenosis. J Thorac Cardiovasc Surg . 1992;103:692.)

The transanular patch should be of untreated or glutaraldehyde-treated autologous pericardium. Processed xenopericardium, or PTFE can also be used in older children. Material cut from a conduit of collagen-impregnated polyester could be used in older patients (encountered infrequently today), in whom this material provides the benefit of precise sizing of the patch, ^, and when properly trimmed, its convexity is ensured, as is a relatively “square cut” of its distal end (see Fig. 34.31 B). Glutaraldehyde-treated pericardium has similar advantages. In cases where a polyester tube is used, one is selected whose diameter corresponds to a z-value of 0 to +2. However, synthetic patches should be avoided in smaller patients and whenever the patch is to extend to the LPA. In neonates and young infants, autologous, preferably untreated, pericardium should be used exclusively.

Regarding patch sizing, avoid too large a transanular patch, which may completely abolish any RVOTO, but increase postoperative pulmonary regurgitation. ^,

When the time comes for inserting the patch and the distal end of the incision is on the pulmonary trunk, the polyester tube is stretched slightly and cut to the length of the incision, cutting both ends squarely (see Fig. 34.31 ). The corrugated (crimped) nature of the tube provides sufficient length that it is convex longitudinally; the curve makes it a convex “roof” transversely. The tube is then cut longitudinally so that about three-fifths of the circumference remains as the roof. Only the corners are trimmed at the distal end, leaving it very broad, while the proximal (RV) end is tapered. It is then sewn into place with a continuous 5-0 polypropylene suture (see Fig. 34.31 B).

When the incision has been carried onto the LPA, a slightly different technique is used, in the belief that the result is more apt to be geometrically correct. For this, a rectangular piece of pericardium is cut about 1.5 times wider than the apparent diameter of the LPA and about 1.5 times longer than the incision in the LPA. It is sewn into place with continuous 6-0 polypropylene sutures placed slightly farther apart in the patch than in the wall of the LPA. A polyester tube may be used for the remainder of the reconstruction.

Alternatively, fresh or glutaraldehyde-treated autologous pericardium can be used for both the transanular patch and the extension onto the LPA. Its length can be determined by measuring length of the incision from the right ventricle to the pulmonary artery, and its maximum width is determined visually by holding the edges of the incision open at valve level and judging the size of the roof required to create a new pulmonary anulus whose diameter is no larger than three-fourths the diameter of the ascending aorta. Alternatively, in infants, an 8-, 9-, or 10-mm Hegar dilator can be placed through the divided anulus, and the width of the patch required to complete the roof over it measured. Both ends are cut almost transversely to create a blunt patch, particularly distally, and the patch is positioned using continuous 6-0 or 7-0 polypropylene sutures commencing at the distal end of the incision ( Fig. 34.33 ). The suture is placed using a running over-and-over technique, placing the first two or three throws along each side before pulling the pericardial patch into position as the suture is tightened. Suturing is continued down each side to the anulus level, then the remainder of the right ventriculotomy is closed by incorporating the pericardial patch into it with continuous sutures. Deep bites of muscle are taken down each side and at the angle.

Repair of tetralogy of Fallot in neonates. (A) A transanular right ventricular–pulmonary trunk incision is almost always used, keeping ventricular portion as cephalad as practicable. (B) Pulmonary valve is incised fully to arterial wall and, if grossly distorted, resected fully. Parietal and septal extensions of the trabecula septomarginalis are incised at their origins from the infundibular septum, but resection of muscle is kept to a minimum. Ventricular septal defect (VSD) is closed as for the right ventricular approach (see Fig. 34.27 ). Often, pericardium is used for VSD patch. (C) Transanular incision is closed with a pericardial patch large enough to attain a mildly convex contour in all directions. LPA, Left pulmonary artery; SVC, superior vena cava.

During repair, a PFO (present in about two-thirds of patients ^, ) should generally be closed in older infants and children. Rarely, a persistent atrial communication can be the source of paradoxical cerebral emboli late postoperatively. If a true atrial septal defect is not closed, there may be left-to-right shunting at atrial level. In neonates and infants, if a transanular patch is placed or if important pulmonary regurgitation is present, a PFO may be left unclosed to allow decompression of any right atrial hypertension caused by acute RV dysfunction. ^, Some arterial desaturation may be present in the first few postoperative days, but it then disappears as the right ventricle remodels to accommodate the physiology of a high-volume, low-pressure circulation, as opposed to the preoperative physiology of a low-volume, high-pressure circulation. In fact, evidence of arterial desaturation is essentially proof that important RV dysfunction is present. A preexisting PFO should be narrowed to a diameter of 3 to 4 mm. This is accomplished by suturing a portion of the free edge of the septum primum to the left side of the limbus (where it would naturally attach if spontaneous closure had occurred) using several 5-0 polypropylene mattress sutures ( Fig. 34.34 ). This will preserve a functioning, but somewhat smaller, PFO. If the pulmonary valve is competent in neonates and infants after repair, important RV failure is unlikely, and the PFO can be closed at repair. It should be pointed out, however, that objective evidence of the benefit this approach is lacking, so leaving a residual communication at atrial level remains a matter of individual surgeon judgement or of institutional policy.

Technique of partial closure of patent foramen ovale (PFO) in patients undergoing infant tetralogy of Fallot repair. Using a standard right atriotomy, the limbus and free edge of the septum primum are identified. A single pledgeted mattress suture of 5-0 polypropylene is placed through edge of septum primum, with pledget positioned on left atrial surface of septum primum. Suture is then brought through limbus from left atrial side to right atrial side and is firmly tied. This reduces size of the PFO opening but maintains its natural position and competence. Inset shows procedure from close up enface and profile perspectives. IVC, Inferior vena cava; RV, right ventricle; SVC, superior vena cava; TV, tricuspid valve.

If a true atrial septal defect is present, it should be closed using a patch. If right heart decompression is deemed desirable as a precaution for RV failure, the ASD can be closed leaving a small open flap that overlaps the edge of the limbus, to function like a PFO. The resulting cyanosis of atrial right to left shunting is well tolerated postoperatively, because chronic cyanosis is typically present preoperatively. Although leaving a small atrial communication under these conditions is quite prevalent and seems prudent, some studies demonstrate no benefit.

After usual intraoperative preparations (see “ Preparation for Cardiopulmonary Bypass ” in Section III of Chapter 2 ), a median sternotomy is performed. Prompt control of major bleeding from collaterals is accomplished with electrocautery. The usual dissections are made (see “ General Plan and Details of Repair Common to All Approaches ” earlier in this section) and purse-string sutures and tapes placed. A polyester tube (see “ Decision and Technique for Transanular Patching ” earlier in this section) may be selected, and pericardium may be removed and treated with glutaraldehyde.

CPB is established, and the patient’s core temperature is cooled to 24°C to 32°C using direct or indirect vena caval cannulation (see “ Preparation for Cardiopulmonary Bypass ” in Section III of Chapter 2 ). The colder end of the spectrum should be considered in older, very cyanotic patients who may have developed substantial acquired systemic to pulmonary artery collaterals. Two venous cannulae are needed. The cardioplegic catheter (or needle) is secured into the ascending aorta. An efficient system for venting the left heart is essential for precise repair of TOF, because of the potential for high collateral flow return to the left atrium. The left atrial suction line may be inserted through the base of the right superior pulmonary vein through a purse-string suture and advanced across the mitral valve to vent the left ventricle. Alternatively, a left atrial vent catheter may be placed via a pursestring placed around the tip of the left atrial appendage, and this site can be used postrepair for monitoring left atrial pressure, if desired. Another popular method is to vent the left atrium with a pump suction placed via a preexisting or surgically created atrial communication after cardioplegic arrest and opening of the right atrium. The aorta is clamped and cold cardioplegic solution injected (see “ Cold Cardioplegia, Controlled Aortic Root Reperfusion, and [When Needed] Warm Cardioplegic Induction ” in Chapter 3 ). Efflux from the coronary sinus is aspirated and discarded or allowed to escape from the right atrium.

The right ventricle is opened through a vertical (longitudinal) incision, sparing large conal and anterior branches of the RCA that cross the right ventricle. If it is expected that the pulmonary valve will be adequate, the incision is made in the midportion of the RV infundibulum and extended nearly to, but not into, the pulmonary valve superiorly and just into the sinus portion of the right ventricle. Two pledgeted stay sutures placed through each side of the incision are placed on traction for exposure. Alternatively, this can be achieved manually using handheld retractors.

Infundibular dissection is performed (see “ General Plan and Details of Repair Common to All Approaches ” earlier in this section and Figs. 34.26 and 34.27 A to C). The pulmonary valve is examined, and if it is stenotic, a valvotomy is performed through a pulmonary arteriotomy (see Fig. 34.30 A). Diameter of the valve anulus is estimated with Hegar dilators. If a transanular patch is considered necessary (see “ Decision and Technique for Transanular Patching ” earlier in this section), the infundibular incision is carried across the anulus before performing the infundibular dissection, paying attention to the position of the pulmonary valve commissures (see Fig. 34.31 ).

After the RV outflow tract is addressed, the VSD is closed using a patch (see Fig. 34.27 D to F) . If the decision earlier in the operation has been not to use a transanular patch, measurements with Hegar dilators are repeated from the right ventricle after VSD closure. If no further narrowing has resulted, the pulmonary arteriotomy and infundibular incision are closed with patches (see Fig. 34.30 B). Similarly, if a transanular incision has been used, it is closed with a patch of appropriate diameter (see “ Decision and Technique for Transanular Patching ” under Technical Details of Repair earlier in this section). The right atrium is opened (if not done at the beginning of the cardioplegic arrest period) and the atrial septum examined. If an atrial septal defect or PFO is present, it is managed as described in “Management of the Atrial Septum” under Technical Details of Repair earlier in this section), usually by direct suture closure. The right atriotomy is closed.

Rewarming and myocardial reperfusion (see Chapter 3 ) can be commenced at any point after VSD closure. Thus, by preference, the RV outflow tract patches can be placed either with the aortic clamp in place or with rewarming and myocardial reperfusion initiated. Separation from CPB is performed in the usual way (see “ Completing Cardiopulmonary Bypass ” in Section III of Chapter 2 ).

This procedure is identical to repair through the right ventricle up to the point that CPB is established. Aortic cannulation is standard. Bicaval venous cannulation is required. After commencing CPB, cooling is initiated. Once the desired core temperature is achieved (generally 28°C to 32°C nasopharyngeally), the caval tapes are snugged, the aorta is clamped, cardioplegia is administered, a right atriotomy is carried from the base of the appendage well inferiorly, a little anterior to the inferior vena cava cannula site, and the left heart is promptly vented (unless a superior pulmonary vein or left atrial appendage vent was previously placed) with a coronary suction placed into the left atrium through a preexisting PFO or an incision made in the fossa ovalis of an intact atrial septum. Prompt decompression of the left heart after cardioplegic arrest is essential to prevent LV distension, as the frequently abundant collateral flow to the lungs and consequent left heart return may distend the now arrested ventricle. The right atrium, atrial septum, tricuspid valve, VSD, and RV outflow tract are examined (see Fig. 34.29 A). The sequence of steps for transatrial–transpulmonary repair differ depending on whether a continuous suture or an interrupted suture technique is used for VSD closure.

With properly placed 6-0 polypropylene traction sutures on the septal and anterior leaflets of the tricuspid valve, the edges of the VSD can usually be visualized, although with more difficulty in TOF than in isolated VSD because of the leftward and anterior displacement of the infundibular septum and its parietal extension. Alternatively, manual retraction by the surgical assistant using delicate instruments can achieve similar, or superior, exposure. The pathway from sinus to outflow portion of the right ventricle is examined. The obstructive nature of the prominent parietal extension of the infundibular septum (see Figs. 34.28 and 34.29 B) is particularly well appreciated from this approach, and the os infundibulum is easily visualized. The pulmonary valve may not be immediately visible because of the presence of obstructing muscle bundles but can be well seen once the division and resection of the obstructing muscle is completed (see later, interrupted suture technique). The VSD is repaired by sewing into place a patch (preferably polyester velour or, in neonates and small infants, autologous glutaraldehyde-treated pericardium).

When the continuous polypropylene technique is used ( Fig. 34.29 B to D), the VSD is closed before mobilizing and resecting the parietal band (as illustrated in Fig. 34.29 ). Often this allows better visualization of the borders of the VSD and, importantly, defines the limit of parietal extension to be resected (see Fig. 34.29 B). The VSD patch protects the aortic valve and crista during subsequent relief of outflow stenosis. Care should be taken not to cut or loosen the continuous patch suture anteriorly when resecting the parietal band. If needed, several interrupted sutures should be placed on this portion of the rim of the VSD patch.

RV outflow tract obstruction is then addressed, following VSD closure. The parietal extension is deeply incised 2 to 4 mm beyond its origin (toward the free wall) from the infundibular septum and 4 to 5 mm above the aortic cusps, which are visualized as the cut is made (see Fig. 34.29 E). The parietal extension is then dissected away from the ventricular-infundibular fold (inner curvature of the right ventricle) and from the anterior free wall of the right ventricle and excised. The free wall of the right ventricle is palpated occasionally from outside during this dissection to avoid perforating it. Any hypertrophied and obstructive trabeculae along the left side of the outflow tract are incised and removed together with the fibrous margins of the infundibulum.

Following RVOT resection, the infundibular chamber is examined and its width measured with Hegar dilators to determine whether it needs to be widened by a full-length infundibular patch. Generally speaking, in such an extremely rare case, for example, in the cases of tetralogy type double outlet right ventricle, the atrial approach should not have been considered. This is because in TOF, the VSD is always easier to expose and close through a ventriculotomy than through an atriotomy. Thus, if a full infundibulotomy (ventriculotomy) extending by necessity to the RV free wall is required to address a long, extensively hypoplastic infundibulum, the VSD should be closed through this ventriculotomy. It makes little sense to close the VSD through the right atrium if an extensive infundibular incision extending onto the RV free wall, amounting to a full ventriculotomy, is required.

When the interrupted suture technique is used for VSD closure, the infundibular resection, pulmonary valvotomy, and any enlargement of the pulmonary valve anulus deemed necessary are typically all performed prior to VSD closure , as this facilitates gentle retraction needed to place successive sutures.

Following VSD closure, the pulmonary valve is then examined and the diameter of the anulus is estimated by passing a Hegar dilator antegrade across the RV outflow tract. If a pulmonary valvotomy is needed, it is usually done through a longitudinal incision in the pulmonary trunk (see Fig. 34.30 ). After valvotomy, the RV outflow diameter is again estimated by sizing the pulmonary valve orifice with Hegar dilators. Occasionally, a few additional obstructing muscle bundles unappreciated from the transatrial perspective are visualized via the transpulmonary approach and are divided or resected.

If a transanular patch is considered necessary (see “ Decision and Technique for Transanular Patching ” earlier in this section), the infundibular incision is carried across the anulus before performing the infundibular dissection, paying attention to the position of the pulmonary valve commissures (see Fig. 34.31 ). Typically, in the transatrial–transpulmonary approach, any TAP needed extends for only a few millimeters onto the RV infundibulum free wall (which explains the term “mini-transanular patch”, to distinguish this from a full transanular patch used to repair an incision across the entire length of the infundibulum). The pulmonary arteriotomy is then closed, usually with a pericardial patch, which also serves as the “mini-TAP” if needed.

In all cases, attention is given to ensuring competence of the tricuspid valve, whose function may be affected by the underlying VSD patch in the area of the anteroseptal commissure. Any leaflet tissue and/or chordae encroached upon by the patch are unfurled, and, occasionally, partial closure of the anteroseptal commissure with a few interrupted fine Prolene sutures (“anteroseptal commissuroplasty”) secures excellent tricuspid valve function.

Management of an atrial septal defect or PFO and the remainder of the operation proceed as described for repair through the right ventricle. Typically, as the transatrial repair does not use a large ventriculotomy, RV function is least affected, and no interatrial communication is left.

Although the transatrial approach can be applied effectively even in neonates, to avoid retraction of the tricuspid anulus in the small and fragile neonatal heart, neonatal repair is usually accomplished via the transventricular approach. A median sternotomy is performed and the heart exposed. A subtotal thymectomy is performed, paying careful attention to the phrenic nerves. If the echocardiogram (or, rarely today, a cineangiogram) indicates that a transanular patch is required, and in borderline cases, the front of the pericardium is removed from where it joins the diaphragm to its most superior reflection from the aorta. This secures a piece of pericardium at least 6 cm long and 3 cm wide, tapering at both ends. The pericardium is stretched with its epicardial surface downward onto a gauze moistened in saline or on a cardboard and is set aside for later use, preferably without glutaraldehyde pretreatment. Dissection of the pulmonary trunk, RPA, LPA, and ductus arteriosus or ligamentum arteriosum is easily and rapidly achieved.

CPB is established using aortic cannulation and, preferably, bicaval cannulation; however, single venous cannulation of the right atrium can be used. Standard continuous CPB with cooling to 28°C to 32°C and cardioplegic cardiac arrest is preferred. The left heart is vented in standard fashion, typically through the right upper pulmonary vein, or other method according to surgeon’s preference. Alternatively to bicaval cannulation, hypothermic circulatory arrest can be used and, rarely, may still be preferred by some. The ductus arteriosus, if present, is doubly ligated using two 5-0 polypropylene sutures and divided. The suture used to ligate the pulmonary artery end of the ductus should be placed precisely, as distal to the pulmonary artery origin of the ductus as is feasible, to avoid constriction of the LPA branch or obstruction of the LPA lumen by extrusion of bulky ductal tissue. If a ligamentum is present, it should also be ligated and divided to avoid tethering of the LPA origin, which can cause late kinking and LPA obstruction, especially if pulmonary regurgitation and RV outflow tract dilation develop. When imaging studies indicate that a transanular patch is not required and when dissection of the pulmonary trunk confirms that it is of adequate diameter, a vertical incision is made into the right ventricle (see Fig. 34.27 ). The infundibular stenosis is completely relieved. This often involves simple transection of the parietal and septal extensions of the TSM, rather than resection (similar to that shown in Fig. 34.33 B). The pulmonary valve is examined from below and any stenosis relieved in the manner already described. The VSD is closed through the infundibular incision (similar to that shown in Fig. 34.27 ).

The tricuspid valve is retracted and the atrial septum exposed, looking retrograde from the right ventricle into the right atrium. If a PFO is present, it may be possible to close or modify it from this approach. Usually, the right atrium is opened and the PFO is managed through this approach. Or, if there is a more extensive atrial septal defect, the defect is closed using a pericardial patch with continuous polypropylene suture. If a residual atrial communication is desired, it is managed as described in Fig. 34.34 . The right atrium is closed. The ventriculotomy is then closed with a pericardial patch using a continuous suture.

When a transanular patch is indicated, the incision is carried across the anulus and out along the pulmonary trunk almost to the origin of the LPA, and a transanular pericardial patch is placed after VSD closure (see Fig. 34.33 A). Should there be LPA origin stenosis, the incision passes beyond this to reach the normal-diameter LPA ( Fig. 34.35 ). If a transanular patch is used in neonates and young infants, many prefer to leave the PFO open.

Repair when incision for transanular patch has been carried onto left pulmonary artery (LPA) . (A) Dashed line indicates extent of incision. (B) Pericardial patch is sewn into place to enlarge LPA. Note that it is cut in rectangular shape to permit maximum convexity after insertion. At first, distal suturing of patch is done “at a distance.” (C) Completed patch attains a rounded convex contour. RAA, Right atrial appendage; RPA, right pulmonary artery.

In this situation, there is usually sufficient hypoplasia of the pulmonary anulus and trunk that a transanular patch is also required (see “ Morphology ” earlier in this section). Repair is usually accomplished in exactly the manner described for situations in which the incision for placing a transanular patch must be extended onto the LPA (see “ Decision and Technique for Transanular Patching ” earlier in this section and see Fig. 34.35 ). In those uncommon instances in which a transanular patch is not needed, an incision is made across the stenosis in the origin of the LPA. A rectangular patch of pericardium is trimmed and sewn into place as described.

When there is virtual or total occlusion of the LPA origin, patch graft enlargement is not satisfactory. Instead, after locating the patent portion of the LPA beyond the zone of occlusion by dissecting along the chord of tissue that still connects it to the pulmonary trunk bifurcation, the patent LPA is opened longitudinally on its anterior surface for a short distance. The opened end is then sutured to the adjacent leftward edge of the pulmonary trunk with a running fine polypropylene suture to create a new posterior wall. The anterior wall is next created by a pericardial patch positioned as for reconstruction of a zone of stenosis (see earlier text). When the LPA is totally disconnected from the pulmonary trunk or is too small for this reconstruction, repair entails locating the LPA close to or adjacent to the lung hilum (usually by intrapleural dissection) and disconnecting it from any vessel, usually the ductus arteriosus, that supplies it. It is then usually possible to anastomose the LPA end to side to the leftward edge of the distal pulmonary trunk (mobilizing the trunk completely so that it will swing more easily to the left). Typically, this anastomosis is augmented anteriorly with autologous pericardium.

This situation occurs uncommonly without associated LPA stenosis. In contrast to the LPA, the RPA is usually not an extension of the pulmonary trunk but comes off its side at a right angle. This makes the simple type of repair used for origin stenosis of the LPA less satisfactory, although it can be used when stenosis is not too severe.

Operation proceeds as usual until the VSD has been repaired. Then a small longitudinal incision is made in the pulmonary trunk to visualize the RPA orifice ( Fig. 34.36 A). The origin of the RPA is excised from the pulmonary trunk. Lateral incisions are made to enlarge the orifice in the side of the pulmonary trunk ( Fig. 34.36 B). The RPA is incised from its narrow orifice back into its wide portion. A rectangular piece of pericardium is trimmed and sewn to the RPA to make a markedly enlarged proximal RPA ( Fig. 34.36 C). The proximal end of the reconstructed RPA is then sutured to the enlarged orifice in the side of the pulmonary trunk using continuous 6-0 or 7-0 polypropylene sutures, while taking care to avoid any purse-string effect ( Fig. 34.36 D). Alternatively, the posterior edge of the opened RPA is sutured to the back wall of the opened pulmonary trunk; the rectangular piece of pericardium is then sewn to the remaining opening to widen it further.

One type of repair of stenosis at origin of right pulmonary artery (RPA) . Initially, a small incision is made in pulmonary trunk through which stenotic orifice of RPA can be viewed from within. (A) Ascending aorta has been mobilized to expose origin of RPA. Proposed incision for disconnecting RPA from pulmonary trunk is shown. (B) RPA has been disconnected from pulmonary trunk. Resulting orifice in RPA can be enlarged as shown, but enlargement by incision is preferable. An incision is made down anterior aspect of RPA. (C) RPA is enlarged with a pericardial patch. (D) Enlarged RPA is reattached to enlarged aperture in pulmonary trunk. (At times, it may be easier to suture posterior wall of RPA to posterior aspect of pulmonary trunk orifice before making pericardial enlargement of RPA). LPA, Left pulmonary artery; SVC, superior vena cava.

Transection of the ascending aorta to improve exposure may be used but is rarely necessary.

This condition requires appropriate reconstruction based on proper understanding of the morphology, although few papers discuss details of this repair. Both the LPA and RPA ostia are usually stenosed to a similar degree and over a short distance (<15 mm), and the distal pulmonary trunk is often similarly narrowed. The pulmonary trunk may be short, making the bifurcation proximal and more Y-shaped than usual.

In patients 5 years of age or older, replacement of the pulmonary valve, trunk, bifurcation, and proximal RPA and LPA with a pulmonary allograft ( Fig. 34.37 ) ^, has been advocated. However, this is a much less desirable operation, especially in infants, because the allograft will certainly be outgrown soon and require much earlier replacement than when used in older children. Therefore, although allograft replacement provides a good hemodynamic result in this complex situation, careful repair taking full advantage of all native tissue available is much preferable. Complete mobilization of the aorta, pulmonary trunk, RPA, and LPA is required, preferably before CPB. The vertical ventriculotomy is carried across the anulus into the pulmonary trunk and extended to the bifurcation. A second incision is made on the anterior aspect of the branch pulmonary arteries, extending from the normal diameter of the distal LPA, across the stenotic region of the LPA, onto the RPA, and extending across the stenotic region of the RPA to the distal normal-diameter RPA. Thus, the two incisions described create a T shape. Autologous pericardial tissue or allograft pulmonary artery tissue is used to patch-augment the pulmonary trunk and branch pulmonary arteries. Two patches are best used, the first to patch the branch pulmonary arteries and the second as the transanular patch, which extends distally to the first patch. Figure 34.38 illustrates the two patch technique, and with bifurcational stenosis, the left branch pulmonary artery patch is extended across into the RPA.

Repair of severe pulmonary trunk and bifurcation stenosis using a pulmonary valve allograft and its bifurcation. (A) Dissection must be complete. For this, entire ascending aorta is completely freed from its posterior connections and from pulmonary trunk and its bifurcation. (B) Superior vena cava is completely mobilized and right and left pulmonary arteries (RPA and LPA) dissected at least to the point where the first branch is visualized; that is, beyond the immediately prebranching level. (C) Ascending aorta may be divided, but often the procedure can be performed without this step. Distal anastomoses are made first, taking care to transect the LPA and RPA beyond the narrow areas and to leave some redundancy in allograft bifurcation. (D) Completion of the proximal anastomosis, often with a polyester (or pericardial) hood as shown. If transected, aorta is brought together end to end. Importantly, however, if aorta is enlarged and compresses the underlying allograft bifurcation or RPA, a short segment of polyester or polytetrafluoroethylene tube should be interposed between the two ends of the aorta. SVC, Superior vena cava.

Repair of left pulmonary artery (LPA) stenosis in tetralogy of Fallot using two-patch technique. (A) Typical right ventricular (RV) outflow tract hypoplasia and LPA stenosis present at ductus arteriosus or ligamentum arteriosum. (B) Separate RV outflow tract patches and LPA patches are placed using a running monofilament suturing technique. This technique is useful when the angle of take-off of the LPA makes a single patch difficult to position correctly. PA, Pulmonary artery; RPA, right pulmonary artery.

In hearts in which there is a large coronary artery crossing the RV outflow tract close to the pulmonary anulus (usually an anomalously arising LAD from the RCA, but sometimes the entire left coronary artery coming from the RCA), relief of pulmonary stenosis must neither divide nor compromise flow through this vessel. Because such a vessel is occasionally buried in muscle or fat and is not apparent on surface inspection at operation, preoperative imaging must be of sufficient quality to exclude this anomaly. When there is uncertainty, the site of the usual course of the first part of the LAD is investigated during operation, and if the LAD is not there, it arises anomalously. When anomalous LAD origin is present, the technique of repair depends on morphology of the RV outflow obstruction. When the pulmonary anulus is of adequate diameter, repair is best accomplished via the right atrium. Any valvar stenosis is relieved via the pulmonary trunk.

Even when there is a small pulmonary anulus and proximal pulmonary trunk, the usual transatrial–transpulmonary approach already described may be safely employed. In many if not most cases, the anomalous LAD does not “hug” the pulmonary valve anulus but rather courses obliquely away from it as it courses towards the interventricular groove. This may allow performance of a “mini” transanular incision (5–7 mm) stopping well short of the anomalous artery, which therefore remains undamaged and safe. The mini-TAP may be sufficient to relieve the obstruction adequately, and this can be confirmed with Hegar dilators in the relaxed heart and by pressure measurements after separation from CPB. If, despite these maneuvers, significant obstruction persists, then an allograft valved conduit can be used to connect the right ventricle to the pulmonary trunk. The native RV outflow is allowed to function in parallel with the implanted conduit. As an alternative to a prosthetic tube conduit, a turned-down flap of main pulmonary artery has been used to form the back wall of a theoretically growing tube connection. Other techniques have been used avoiding a conduit, such as main pulmonary artery translocation, transanular repair under a mobilized LAD, and displaced ventriculotomy with subcoronary suture lines.

The AATS relevant recommendations on anomalous coronary artery are the following :

When a transanular repair would otherwise be necessary, in the presence of an anomalous coronary artery crossing the RVOT, either a coronary artery sparing ventricular incision or an RV to pulmonary artery conduit may be reasonable approaches based on institutional expertise (Class: iIb, LOE: C-EO) .

If the left coronary artery is inadvertently damaged by the right ventriculotomy, an attempt should be made to repair the coronary immediately, either primarily with fine sutures or by placing a small suitable patch. Alternatively, the left internal thoracic artery can be taken down (see “ Internal Thoracic Artery ” under Technique of Operation in Chapter 9 ) and anastomosed to the distal left coronary artery. This procedure, which should arise extremely rarely if ever, can be life saving.

Systemic-to–pulmonary artery shunts will have been created either through a thoracotomy (left or right) or a median sternotomy, and will consist of either a native systemic artery–pulmonary artery anastomosis (classic B-T shunt, rarely if ever used today, except perhaps for palliation of very low body weight neonates), or, most commonly, of an interposition PTFE graft between a systemic and a pulmonary artery. In the modern era, PTFE shunts are used much more commonly than classic B-T shunts, and a median sternotomy approach has gained favor. However, variation in preferred shunt technique still exists, and older patients may be encountered with shunts placed using techniques rarely used today, such as the Waterston or Potts shunt.

In many centers, median sternotomy has replaced lateral thoracotomy for primary systemic–pulmonary arterial shunts in neonates. Generally, a PTFE tube graft is used, connecting the brachiocephalic artery or brachiocephalic-subclavian junction to the RPA or LPA. In patients with a left aortic arch, the shunt is placed on the right side; with a right arch, it is on the left. In some patients, a central shunt utilizing a short PTFE tube graft may be used between the ascending aorta and either the main pulmonary artery or one of the main branch pulmonary arteries ( Fig. 34.39 ). At complete repair, access to a shunt placed via sternotomy is much better than that for all other types of shunts, with the graft positioned intrapericardially and centrally. Right-sided shunts are positioned medial to the superior vena cava and apposed to the lateral aspect of the ascending aorta, and on the left, just leftward of the ascending aorta. The shunt can and should be dissected prior to institution of CPB in most cases, the only exception being deeply cyanotic patients with a very small shunt. Interruption of the shunt is accomplished as CPB is initiated by either ligation or by placement of appropriately sized hemostasis clips securely across the tube graft at the systemic and pulmonary ends. The graft should be divided to avoid progressive distortion of the branch pulmonary artery due to somatic growth.

Composite diagram illustrating various positions of the usual systemic–pulmonary arterial shunts for augmenting pulmonary blood flow. (A) Classic right Blalock-Taussig subclavian–pulmonary artery shunt with left (normal) aortic arch. (B) Usual polytetrafluoroethylene (PTFE) interposition tube graft, shown between right pulmonary artery and brachiocephalic artery bifurcation. (C) Left-sided PTFE interposition tube graft, shown between left pulmonary artery and left subclavian artery. (D) Central shunt utilizing short PTFE tube between ascending aorta and pulmonary trunk. LPA, Left pulmonary artery; RPA, right pulmonary artery.

Median sternotomy in an older patient with TOF and a classic B-T shunt is usually accompanied by profuse bleeding from arteries in front of and behind the sternum that have developed as part of the collateralization that follows subclavian artery ligation. While this bleeding is being controlled, rapid volume replacement should not be made with banked blood. This is because this low-calcium-content and low-pH blood passes directly across the VSD into the aorta and coronary arteries. If this cold, unmodified banked blood is infused rapidly, the heart may slow and even develop asystole. Warmed calcium-enriched blood may be used.

When an interposition PTFE shunt has been placed via right thoracotomy, typically in patients with a left aortic arch, the shunt is easily identified, ligated, and divided at the time of complete repair via median sternotomy, as it lies readily accessible between the ascending aorta and the superior vena cava.

Left thoracotomy has often been used for shunt placement in neonates or small infants with a left aortic arch. Typically, a left PTFE tube graft has been used between the left subclavian artery and LPA. After sternotomy is performed, hemostasis secured, and sternal retractor inserted, and when the patient’s condition is good, initial dissection is made. Because the graft lies deeply in the left chest, the approach is not beneath the thymus gland but over it, directly into the left pleural space. The few adhesions between the mediastinal pleura and lung are divided with the electrocautery. The PTFE tube graft is somewhat rigid and easily palpated. A small incision is made directly over it and carried down to it. At times a plane of dissection between the graft wall and surrounding tissue is easily established; if so, this dissection is carried out. Otherwise, the pericardium is opened and CPB established. The lungs are collapsed, and a plane of dissection is easily established around the graft. The shunt is ligated or clipped at each end and divided. Remainder of the operation is carried out as usual.

When a classic right B-T shunt is present in a patient with a left aortic arch, the pericardium is opened, and as the assistant elevates and retracts the ascending aorta to the left, the RPA is visualized coming from beneath the aorta. The superior vena cava is dissected off it and gently retracted rightward (in a few cases, exposure of the subclavian artery may be easier with the superior vena cava retracted to the left). Possible distortions of the RPA by the shunt are known from preoperative imaging studies, and these are kept in mind as dissection proceeds. Course of the right subclavian artery coming down to the RPA usually can be suspected from observation and palpation of a continuous thrill. The entire circumference of the subclavian artery may be freed along a short length by sharp or cautery dissection well superior to the anastomosis, and two heavy ligatures placed loosely around it. The artery is then temporarily occluded, and if vessel identification has been correct, the continuous thrill disappears, systolic and diastolic systemic arterial pressures increase, and pulse pressure narrows. If these things do not occur, the RPA has been misidentified as the subclavian artery or the shunt is small. The heart is cannulated, CPB is begun, ligatures around the subclavian artery are tied, and the operation proceeds as usual. An alternative preferred method is closure with hemostasis clips, in which case temporary ligatures are not placed.

When a classic left B-T shunt is present in a patient with a left or right aortic arch, the subclavian artery is approached from outside the pericardium. For this, the upper left pericardial stay sutures are placed on strong traction to the patient’s right. Level of the LPA is noted before this maneuver; just cephalad (superior) to this level, the thymus gland and left phrenic nerve are dissected from the pericardium, sharply and over a limited area, because excessive dissection in this region can result in major bleeding that is difficult to control. Low power cautery dissection is used, always mindful of the phrenic nerve , from which safe distance must be assured to avoid injuring it. A narrow retractor is slipped under the thymus, and the region of the subclavian artery is located by gentle palpation and cautery dissection beneath the thymus gland. The subclavian artery is dissected out as described for the right side, and the same tests are made for accuracy of identification. Operation then proceeds as described earlier.

If the left subclavian artery cannot be located by going over the thymus gland and phrenic nerve, an alternative method is used in patients with a right aortic arch. The brachiocephalic artery is identified beneath the brachiocephalic vein and traced distally to the point at which it bifurcates into left subclavian and left common carotid arteries. After identifying the left subclavian artery positively by the maneuvers described and by the fact that the anesthesiologist can feel the left common carotid (or left superficial temporal) pulse when the vessel is temporarily occluded, the operation proceeds as described.

These shunts are of historical interest only; they are not used in current practice. In previous years, occasional older patients were seen for evaluation and repair who received the shunt many years before. Nearly all such patients have been repaired or have died; thus, it is rare to encounter such a patient currently. TOF repair after Waterston or Potts ^, shunt can be performed using well-described techniques, including those in the first through third editions of this book.

Fig. 34.39 is a composite illustration of various positions used for systemic–pulmonary arterial shunts for augmenting pulmonary blood flow. General anesthesia with endotracheal intubation and controlled ventilation is used. Monitoring with an intraarterial catheter placed in an artery that will not serve as the systemic source of the shunt is established. Reliable intravenous access is obtained, either centrally or peripherally. Continuous pulse oximetry is utilized. Details of each type of shunt follow.

Classic right blalock-taussig shunt.

This is the original shunt described; however, it is typically not the first choice in modern practice. This is because it has the disadvantages of both sacrificing direct circulation to the right arm and delivering unpredictable flow to the pulmonary arteries. The artery can vary in size initially and can dilate over time. It may have some advantage in extremely small infants.

With the patient in left lateral decubitus position, a right lateral thoracic incision is made ( Fig. 34.40 A, inset). The thorax is entered through either the top of the bed of the nonresected fourth rib or the third interspace. A rib spreader is positioned and gradually opened (see Fig. 34.40 A).

Classic right Blalock-Taussig shunt (left aortic arch). (A) Right lateral thoracotomy is made in third or fourth intercostal space (inset). Right pulmonary artery (RPA) and its branches are mobilized and azygos vein ligated and transected. (B) Right subclavian artery is completely dissected, mobilized, and ligated just proximal or distal to its first branch. It is then divided as shown by dashed line and brought out from beneath the vagus nerve. (C) Subclavian artery has been divided and appropriate occluding devices placed on RPA . Incision in RPA is made on its very superior aspect. (D) Anastomosis is made using interrupted or continuous 7-0 polypropylene sutures, starting posteriorly from within vessels. Inset shows completion of anastomosis. SVC, Superior vena cava.

The first step in dissection is to securely identify the right superior pulmonary vein as it courses obliquely downward (medially and inferiorly) toward the heart to pierce the pericardium posterior to the phrenic nerve. The vein partially overlies the RPA; however, the RPA, in contrast to the vein, follows a straight course medially. With the lung retracted toward the surgeon, the periarterial sheath over the RPA is incised. Usually, the superior branch of the RPA is first freed, in the process of which the main RPA (lying in a slightly different plane of dissection) can be easily overlooked. To find it, the superior surface of the right superior pulmonary vein is cleared, and it and the superior vena cava are elevated ( Fig. 34.40 A). Dissection is carried centrally until the proximal RPA is identified as a single vessel, proximal to its first branch. With lateral traction on a loop of heavy suture placed around it, the RPA is dissected in the periarterial tissue plane as far centrally as possible. The loop is then removed so that the RPA does not inadvertently become obstructed during the next phase of the operation.

The lung is packed off and retracted inferiorly. An incision is made in the mediastinal pleura over the azygos vein and carried superiorly to the top of the chest, parallel and posterior to the phrenic nerve. The azygos vein is divided between ligatures, and the soft tissue and right paratracheal lymph nodes are divided to provide a free pathway for the turned-down right subclavian artery. Any small veins overlying it are ligated and divided. Vagus and recurrent laryngeal nerves are identified, and the periarterial plane over the right subclavian artery is incised. By grasping only the adventitia of the often delicate subclavian artery, dissection is carried distally in the periarterial plane until the origins of internal thoracic and vertebral arteries are identified. These vessels are divided between ligatures, taking care that the proximal ligature is placed 1 to 2 mm away from the subclavian artery ( Fig. 34.40 B). Anomalies in branching of the subclavian artery are frequent. The vagus nerve is gently retracted laterally, and the periarterial plane over the subclavian artery medially is opened and dissected. The subclavian artery is divided between ligatures placed beyond the first two large branches, and a right-angled clamp is passed beneath the vagus nerve from its medial aspect superior to the recurrent laryngeal nerve ( Fig. 34.40 C). The subclavian artery beyond the ligature is grasped with the clamp and pulled out from under the vagus nerve. Holding the artery beyond the ligature, dissection is carried centrally in the periarterial plane until the distal portion of the brachiocephalic artery and nearly the entire right common carotid artery are liberated. As dissection proceeds, a small artery is occasionally found arising from the origin of the subclavian from the brachiocephalic artery; this must be ligated and divided. The only thing limiting the turned-down length of the subclavian artery is the common carotid artery. Any obstructing bands in the paratracheal soft tissue are divided so that there is nothing in the pathway of the relocated right subclavian artery.

A light, straight arterial clamp with a handle long enough to allow easy holding by the first assistant is placed across the subclavian artery about 8 mm proximal to the point of final transection. The artery is cut squarely across, just proximal to its first branch. (Rarely the first branch comes off very proximally and the subclavian artery is unusually large beyond it. In such instances, the artery can be transected beyond this branch). Double-looped elastic ligatures are placed around the upper branch and distal main RPA, snugged, and weighted laterally with heavy Kocher clamps. An appropriate-sized Baumgartner clamp is placed across the very proximal RPA, with the surgeon passing a right-angled clamp beneath the artery for lateral retraction as the first assistant tightens the clamp. A longitudinal incision is made in the very superior surface of the RPA (so that when the occluding devices are removed, there will be no torsion of the RPA).

Anastomosis is made with continuous or interrupted double-armed 7-0 polypropylene or polyester sutures, the continuous suture placed from within the respective arteries posteriorly ( Fig. 34.40 D). The first assistant holds the two clamps such that the vessels are in perfect apposition and without tension during the anastomosis. Before placing the last few sutures, the lumina are examined and any tiny thrombi or debris irrigated away. After completing the anastomosis, in rather rapid succession the two doubly looped elastic ligatures are cut and removed, the clamp on the subclavian artery removed, and the proximal RPA clamp removed. Packing is placed lightly around the anastomosis, any unusual bleeding is controlled digitally, the lung is partially reexpanded, and 5 minutes are allowed to pass. During this time, a palpable continuous thrill should be present in the RPA. When the packs are removed, the field is usually dry. Rarely, an additional adventitial suture is needed.

A small chest catheter is brought out from the posterior gutter through about the seventh intercostal space and attached to gentle suction. The chest wall is closed and the lungs are well inflated before the ribs are brought together with absorbable suture. The wound is closed in layers with continuous fine polyglycolic acid sutures, and the skin approximated with a continuous subcuticular suture.

Interposition shunt between left subclavian and left pulmonary artery.

This is a commonly performed procedure. It can be performed classically through a left thoracotomy or through a median sternotomy. The procedure performed through a thoracotomy is described.

Thoracotomy is as described for the classic B-T shunt, except on the left side. The LPA is identified and dissected out. The mediastinal pleura is opened over the left subclavian artery and contiguous portion of the aortic arch, and the periarterial sheath over these structures is opened. The subclavian artery is not mobilized.

The diameter of the graft is chosen based on the patient’s weight and other factors. In normal-sized neonates or in the case of a very small LPA, a 3.5- or 4-mm PTFE tube graft is used, despite a possible small reduction in patency (see “ Size ” under Special Situations and Controversies, Systemic–Pulmonary Arterial Shunt, in Section IV of Chapter 52 for discussion of criteria for selecting size of the PTFE tube graft). Before any occluding devices are placed, the proper length of the tube graft is determined. For this, the lung is partially inflated to bring the LPA into its usual position. When the anastomosis is completed, the graft should lie without tension and without redundancy (and thus potential kinking) between the proximal half of the subclavian artery and the superior surface of the LPA. The end of the graft that will be anastomosed to the subclavian artery is beveled ( Fig. 34.41 ), the graft is placed in a temporary position, and the other end is cut square at the point that will make the length to the LPA correct.

Left polytetrafluoroethylene (PTFE) interposition shunt (left aortic arch). (A) Exposure and sites of incision (dashed lines) in pulmonary and subclavian arteries. (B) PTFE graft has been trimmed for insertion. End-to-side anastomosis is made between graft and left subclavian artery. First portion of suture line is made by sewing from within, as shown. (C) Distal anastomosis is made in a similar fashion. Direction of suturing (from medial to lateral) at both anastomoses minimizes possibility of tearing delicate subclavian or pulmonary artery. Note that clamp remains on subclavian artery until anastomosis is completed. LPA, Left pulmonary artery; PTFE, polytetrafluoroethylene.

A delicate side-biting clamp is placed deeply on the subclavian artery so that its handle lies inferiorly, and the clamp occludes the artery both proximally and distally. A longitudinal incision is made in the excluded portion of the delicate subclavian artery, and an adventitial stay suture is placed on the anterior lip. The proximal anastomosis is made with a continuous 6-0 or 7-0 polypropylene suture. The clamp on the subclavian artery is not loosened or removed at this time (see variation in detail under “ Systemic–Pulmonary Arterial Shunt ” under Technique of Operation in Section IV of Chapter 52 ). Elastic ligatures are looped twice around the upper branch and main LPA and snugged, and heavy Kocher clamps are placed on each for lateral traction. A C-shaped clamp is placed very proximally on the LPA, taking care not to compromise the ductus arteriosus. A longitudinal incision is made in the superior surface of the LPA, making this a little shorter than half the circumference of the PTFE tube graft. The distal anastomosis is made with continuous 6-0 or 7-0 polypropylene suture.

In quick succession, the doubly looped ligatures are cut and removed, the clamp on the subclavian artery is opened and carefully removed from the field, and the LPA clamp is opened and removed. A light pack is placed about each anastomosis, with light digital pressure if needed. A continuous thrill should be present in the LPA. Other evidences of patency include registration of an immediate increase in oxygen saturation (pulse oximeter) and an immediate increase in systolic and diastolic blood pressure when the shunt is briefly occluded with forceps. Five minutes are allowed to pass.

Remainder of the procedure is completed as described for the classic B-T shunt.

The interposition operation as an isolated procedure in patients with left aortic arch can be performed through a right thoracotomy. The PTFE tube graft is anastomosed proximally to the junction of the right subclavian and brachiocephalic arteries, which is in the cupola of the chest. This operation is more difficult than that on the left side. In comparison with the classic B-T anastomosis, the PTFE interposition shunt is a more reliable resistor and is easier to close later.

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