The left heart-aorta complex is made up of several related structures:

• •

  LV inflow: mitral valve

• •

  Left ventricle as the pump

• •

  Left ventricular outflow tract (LVOT)

• •

  Aortic valve

• •

  Ascending aorta

• •

  Aortic arch

The combination of obstruction and hypoplasia of these structures may impair the ability of the left heart to adequately maintain the systemic circulation, which may be ductal dependent.

Atresia is the congenital absence or closure of a normal body orifice or tubular organ. It is derived from the Greek and Latin, where “a” means without and “tresis” is the word for perforation. Thus, aortic valvar atresia can be defined as either absence or closure of the orifice of the aortic root.

Stenosis is a narrowing or a stricture of a duct or a canal. Aortic stenosis encompasses the supravalvar, valvar, or subvalvar regions. More specifically, aortic valvar stenosis is a narrowing of the orifice of the aortic valve due to fusion of the leaflets causing obstruction of blood flow.

Hypoplasia is the incomplete development or underdevelopment of an organ or tissue. A hypoplastic aortic valve can cause obstruction to blood flow because of its inadequate size.

Obstruction is the act of blocking or clogging, or the state of being blocked or clogged. Obstruction to blood flow may be caused by atresia, stenosis, or hypoplasia of a given structure.

It is particularly important to differentiate the meaning of “stenosis” and “hypoplasia.” Although atresia and stenosis are mutually exclusive terms, hypoplasia may be present with both atresia and stenosis or can exist in isolation. Hypoplasia implies that the organ or tissue is less than its normal size. The terms “aortic stenosis” and “left ventricular outflow tract obstruction,” for example, are not synonymous, although they have been used interchangeably in the past. In the setting of obstruction to the left ventricular outflow tract, the obstruction to the flow of blood may be caused by either aortic atresia, aortic stenosis, or by hypoplasia of the aortic valve.

Syndrome is a group of signs and symptoms that occur together and characterize a particular abnormality.

Complex is a whole being made up of interrelated parts.

After several years of debate, the International Society for Nomenclature of Paediatric and Congenital Heart Disease (ISNPCHD) agreed on the following definition of HLHS:

Hypoplastic left heart syndrome is a spectrum of congenital cardiovascular malformations with normally aligned great arteries without a common atrioventricular junction, characterized by underdevelopment of the left heart with significant hypoplasia of the left ventricle including atresia, stenosis, or hypoplasia of the aortic or mitral valve, or both valves, and hypoplasia of the ascending aorta and aortic arch.

We prefer to use the term Hypoplastic Left Heart Syndrome , rather than Hypoplastic Left Heart Physiology (the term used in the fourth edition) for the following reasons. Hypoplastic Left Heart Syndrome is a spectrum of cardiac phenotypes, with both anatomic and physiologic characteristics. It is the most widely used term by the community of professionals dealing with congenital heart disease. For example, in a recent Medline PubMed search, the term Hypoplastic Left Heart Syndrome provided 4518 results, whereas the term Hypoplastic Left Heart Physiology provided 1772 results with almost all having the term of “ Hypoplastic Left Heart Syndrome ” in the title.

According to the ISNPCHD, certain cardiac phenotypes are considered part of the HLHS spectrum. At the severe end of the spectrum is aortic and mitral atresia with a virtually nonexistent left ventricle. At the mild end of the spectrum is hypoplasia of the aortic and mitral valve with associated hypoplasia of the left ventricle, without intrinsic valvar stenosis or atresia. Although most of the patients are only amenable to a pathway of single ventricle palliation, a minority may be amenable to biventricular repair. Each individual patient has a specific anatomic cardiac phenotype, while the physiology may be variable over time.

Main anatomic cardiac phenotypes of HLHS:

• •

  Aortic Atresia, Mitral Atresia

• •

  Aortic Atresia, Mitral Stenosis

• •

  Aortic Stenosis, Mitral Atresia

• •

  Aortic Stenosis, Mitral Stenosis

• •

  Aortic Stenosis with Left Ventricular (LV) Hypoplasia

• •

  Hypoplastic Left Heart Complex (Hypoplasia of the Left Heart without Intrinsic Valve Stenosis)

The overwhelming majority of the various anatomic cardiac phenotypes that are part of HLHS together represent a special example of univentricular atrioventricular connection (see Chapter 52 ). Because of the special clinical and surgical importance of this group of malformations, this subject is discussed separately from other forms of Functional Single Ventricle.

The history of attempted reconstructive procedures for HLHS dates back to 1970 when Cayler and colleagues described an anastomosis between right pulmonary artery (RPA) and ascending aorta with placement of bilateral PA bands. Other variations in neonatal reconstructive procedures designed to allow survival without the use of prostaglandins to maintain ductal patency were described by Doty and colleagues in 1977, Norwood and colleagues in 1980, Levitsky and colleagues in 1980, Behrendt and colleagues in 1981, and others.

Even though some of these reports noted short-term successes, there is no documentation of long-term survival. In 1983, Norwood and colleagues described for the first time neonatal palliative surgery leading to a subsequent successful Fontan procedure. Following this report and subsequent reports that systematically documented long-term survival of patients with HLHS, it has become widely accepted that several principles of the first stage palliation described by Norwood are critical to achieving long-term survival. These are:

• •

  Establishment of permanent unobstructed communication between the right ventricle and the systemic circulation and avoiding pulmonary valve (neoaortic valve) distortion

• •

  Balanced pulmonary and systemic blood flow

• •

  Ensuring an unobstructed interatrial communication

Many of the procedures described before implementation of the Norwood procedure failed to address one or more of these issues critical for long-term survival.

Allograft heart transplantation for HLHS dates back to 1985, when Bailey performed the first successful cases as primary therapy in neonates. Since then, Bailey and colleagues and a number of other groups have considered transplantation as one option for treatment, along with reconstructive surgery.

In 1998, Tchervenkov and associates reported their early experience with biventricular repair for a favorable subset of patients with HLHS and introduced the term HLHC to describe these patients.

The hybrid approach was first developed in 1993 in response to poor outcomes following the Norwood procedure. The hybrid procedure combines surgical placement of bilateral branch PA bands, placement of a stent in the ductus arteriosus, and catheter-based atrial septostomy, avoiding cardiopulmonary bypass (CPB). Initially, it was not widely embraced because of poor interim outcomes; however, more recently it has been used by some programs as an alternative to the Norwood procedure in high-risk patients, and variations of the hybrid procedure have been used as a bridge to transplantation. ^,

Currently, it is unclear whether the etiology of HLHS is similar in all cases. There are genetic factors involved, although these are multiple, complex, and poorly understood at the present time. Available evidence suggests that a number of primary morphologic etiologies may lead to the end result of HLHS. Primary morphologic abnormalities at the aortic valve level, mitral valve level, LV myocardial level, or atrial septal level (intact atrial septum) could all in theory lead ultimately to hypoplasia of the entire left side of the heart as gestation progresses.

Fetal echocardiography has yielded much information regarding progression of HLHS. In some cases, critical aortic stenosis with documented forward flow on early fetal echocardiograms progresses to aortic atresia before birth. In such cases, the left ventricle shows evidence of progressive dysfunction and hypoplasia as stenosis proceeds to atresia. Echocardiographic evidence of fetal LV dilated cardiomyopathy progressing to HLHS has been reported. ^, Controversy remains as to whether a closed foramen ovale in utero is a cause or a result of HLHS.

In HLHS, the heart is enlarged to about twice normal weight for age. Its shape is determined by the large right and small left heart chambers ( Fig. 51.1 A). Beyond this, morphologic details vary widely. Several morphologic subtypes of HLHS can be defined based on status of the left heart valves:

• •

  Aortic and mitral atresia

• •

  Aortic atresia with mitral stenosis

• •

  Aortic stenosis with mitral atresia

• •

  Aortic and mitral stenosis

• •

  Aortic Stenosis with LV Hypoplasia

• •

  Hypoplastic Left Heart Complex (Hypoplasia of the Left Heart without Intrinsic Valve Stenosis)

Autopsy specimen of aortic atresia and hypoplastic left heart syndrome from a 4-day-old neonate. (A) Globular external shape of heart results from massive right ventricular (RV) hypertrophy and enlargement. Pulmonary trunk (PT) is large and ascending aorta (AscAo) small. Left ventricle (LV) is small and displaced posteriorly and does not reach cardiac apex. Arrow points to left anterior descending coronary artery. (B) Interior of left atrium (LA) and partly opened LV. Septum primum ( SP ; fossa ovalis) is thickened and protrudes into right atrium (RA) . Mitral valve (MV) is hypoplastic and stenotic, and LV wall is grossly thickened. (C) Interior of fully opened LV. Its cavity is small, and there is marked endocardial fibroelastosis (EFE) , which also involves rudimentary papillary muscles (PM) of small MV. LAA, Left atrial appendage; PVs, pulmonary veins.

Of these, aortic stenosis with mitral atresia is the least common subtype, representing approximately 5% of cases; aortic and mitral atresia is the most common, representing approximately two-thirds of cases. Within these subtypes, the status of the atrial septum, size of the LV cavity and muscle mass, ascending aorta and aortic arch, and ductus arteriosus are also important.

Aortic valve and ascending aorta.

In aortic atresia, the aortic valve is totally absent. Diminutive aortic sinuses of Valsalva are frequently present, giving origin to relatively normally positioned right and left coronary arteries that have a normal distribution pattern. The ascending aorta is narrow, sometimes as small as 1.5 mm in diameter. The portion of the aorta between the atretic valve and brachiocephalic artery serves only as a conduit for coronary blood flow ( Fig. 51.2 ).

Lateral cineangiogram obtained after pressure injection of contrast medium into a brachial artery cannula in a neonate with hypoplastic left heart syndrome. Size of blind ascending aorta, which supplies large coronary arteries, and larger aortic arch and its branches are displayed. Pulmonary trunk (PT) is faintly outlined by contrast medium reaching it through the ductus arteriosus.

At and beyond the brachiocephalic artery, the aortic arch gradually widens and is joined beyond the origin of the left subclavian artery by a large patent ductus arteriosus (PDA). The ductus carries blood from the right ventricle into the descending aorta and retrograde to the brachiocephalic and coronary arteries. A localized aortic coarctation exists in approximately 80% of cases and is usually juxtaductal in location (see Chapter 40 ). Prevalence of coarctation is highest in patients with the most severe hypoplasia of the ascending aorta. In some cases, there may be only mild infolding of the aortic media on the wall opposite the ductal insertion site, or there may be no aortic coarctation whatsoever.

When a patent but hypoplastic aortic valve is present, there may be a variable but still reduced amount of forward flow across the aortic valve. The ascending aorta and arch tend to be larger than in aortic atresia, with the diameter of the ascending aorta ranging from 2 to 6 mm. Aortic coarctation is common.

Left ventricle and mitral valve.

The left ventricle is severely hypoplastic in 95% of cases of aortic atresia. In this setting, the ventricular septum is intact. ^, The mitral valve is either atretic (about one-third of patients) or patent but severely hypoplastic (about two-thirds of patients) (see Fig. 51.1 B and C). When the mitral valve is patent in association with aortic atresia, there may be LV–coronary connections ( Fig. 51.3 ) similar to those present in the right ventricle in cases of pulmonary atresia with intact ventricular septum. It is postulated that these connections serve to decompress the LV chamber. Localized thickening of coronary arteries occurs adjacent to these connections, and there is also a variable degree of endocardial thickening (endocardial fibroelastosis).

Postmortem coronary angiogram obtained by cannulating and injecting contrast medium into a coronary artery ostium in a heart with aortic atresia and hypoplastic left heart syndrome. Small left ventricular (LV) cavity filled rapidly as contrast medium reached it through numerous coronary-LV connections. These form a prominent network within the thickened LV myocardium (arrows) .

Rarely, there is focal calcification and scarring limited to the ventricular subendocardium. The hypoplastic left ventricle shows myocardial fiber disarray qualitatively similar to that present in hypertrophic obstructive cardiomyopathy and in the right ventricle in pulmonary atresia with intact ventricular septum.

In approximately 5% of cases of aortic atresia, the LV cavity is near normal size in association with a large VSD. In such cases, there may be mitral valve atresia or a normal mitral valve. In cases of a normal mitral valve, the malformation is not considered part of the HLHS but a related malformation. Such patients can undergo two-ventricle repair.

When aortic stenosis rather than atresia is present, the left ventricle tends to be larger than the typically minute, slit-like left ventricle of aortic atresia. Its size may vary widely from extremely hypoplastic with hypertrophic muscle and severe endocardial fibroelastosis to a dilated, thin-walled, poorly functioning chamber. The mitral valve is almost always hypoplastic and may be atretic when severe aortic stenosis is present.

Perinatal preoperative management is critical to successful outcome. This may include prenatal transport of the mother and fetus to a cardiac center following fetal diagnosis. ^, Circulatory collapse is usually the result of closure of the ductus arteriosus in the setting of undiagnosed HLHS. This may occur when the infant is still in hospital following birth or after discharge home. If prenatal diagnosis is made and mother and fetus are transferred to an appropriate facility where the infant will undergo surgery, circulatory collapse is all but eliminated. Late diagnosis of HLHS with ductal closure can result in an extremely sick baby who might be best managed with bilateral PA bands and prostaglandin E ₁ (PGE ₁ ) therapy.

After diagnosis, the infant is resuscitated, and PGE ₁ therapy is initiated. Depending on details of the physiologic status of the infant and stability of the infant at initial diagnosis, subsequent preoperative management may vary from essentially no further intervention on the one hand to maximal intervention on the other. The typical patient, however, shows signs of pulmonary overcirculation, and preoperative management is aimed at reversing or at least controlling this to preserve end-organ and myocardial function.

Supportive therapy in the perinatal and neonatal periods can substantially alter natural history. Judicious use of inotropic support, PGE ₁ therapy, nutritional supplementation, and ventilation with 17% or 19% oxygen along with supplemental CO ₂ administration may delay the typical physiologic decompensation for a number of weeks ( Fig. 51.7 ). When indicated, mechanical ventilation can add an extra measure of support. In many cases, the respiratory depression side effect of PGE ₁ therapy may warrant mechanical ventilation.

Survival of neonates with hypoplastic left heart syndrome with optimal medical treatment. Format of figure is as in Fig. 51.6 . Although estimates represent survival before transplantation, similar survival is achieved with optimal medical treatment prior to reconstruction.

(Modified from Jacobs ML, Blackstone EH, Bailey LL. Intermediate survival in neonates with aortic atresia. J Thorac Cardiovasc Surg . 1998;116:417.)

These maneuvers are aimed at achieving a balance of pulmonary and systemic blood flow and maintaining unobstructed and adequate systemic perfusion. Because flow into the pulmonary circuit is unobstructed, Rp at the microvascular level will determine pulmonary blood flow. Any maneuver that causes dilation of the pulmonary microvasculature will result in excessive pulmonary blood flow. Specifically, avoiding supplemental inspired oxygen is critical to the overall strategy; 21% oxygen or even lower Fi o ₂ helps maintain tone in the pulmonary microvasculature. If this maneuver is not adequate, controlled ventilation through an endotracheal tube achieves moderate elevation of Pa co ₂ , causing acidosis, which further constricts pulmonary microvasculature. PGE _l maintains ductal patency, ensuring unobstructed blood flow to the systemic circulation.

Inotropic agents can be used to enhance cardiac output (CO) in the setting of moderate pulmonary overcirculation, but this strategy must be undertaken cautiously because these agents also affect systemic and pulmonary vascular resistances and may unpredictably alter Q ˙ p/ Q ˙ s . Epinephrine and high-dose dopamine, which profoundly increase systemic vascular resistance, should be avoided. Low- to moderate-dose dopamine and dobutamine should be considered the first-line inotropic agents when supplemental cardiac output is considered necessary.

All these maneuvers are used to create optimal preoperative cardiopulmonary status. Assessing cardiopulmonary status is somewhat indirect. Currently, Q ˙ p and Q ˙ s cannot be easily directly measured in the cardiac intensive care unit (ICU). Indirect measures of adequate systemic output include normal peripheral perfusion, adequate urine output, and absence of metabolic acidosis. Evidence of a reasonable balance of Q ˙ p and Q ˙ s includes a Pa o ₂ of about 40 mmHg (Torr) and a systemic diastolic blood pressure greater than 30 mmHg. Even these ideal values do not guarantee that the expected blood flow values in fact do exist. For example, Pa o ₂ can be influenced by other factors: hemoglobin level, metabolic state, temperature, and presence of sepsis to name a few. Furthermore, the inevitable reduction in Rp that occurs over time commonly thwarts all efforts to maintain systemic output and balanced Q ˙ p and Q ˙ s . If this occurs, operation should be scheduled immediately.

For the typical neonate diagnosed early after birth and in whom circulatory collapse has not occurred, the ideal time for surgical intervention is about age 2 to 5 days. In this window of time, the infant completes the profound physiologic changes from fetal life to independent life, yet consequences of a continuously increasing pulmonary blood flow have not yet taken their toll. If circulatory collapse does occur and end-organ damage results, a longer time before operation is often necessary to allow end-organ recovery.

Although not always advisable, ideally, normal function of renal, hepatic, neurologic, gastrointestinal, and cardiopulmonary systems should be documented following resuscitation prior to proceeding with operation. It is not uncommon for organ systems to recover fairly rapidly but then plateau short of complete recovery. Further delay of operation at that point is usually detrimental.

Although mild obstruction of flow across the atrial septum is typical at the time of Doppler color flow interrogation during diagnostic echocardiography, severe obstruction at the atrial septum may occur, resulting in a clinical presentation similar to that found with obstructive TAPVC (see Chapter 30 ), with deep cyanosis, pulmonary edema, and eventual hemodynamic instability. This presentation evolves rapidly immediately after birth and must be addressed within hours. Such patients are best managed with percutaneous interventional techniques to create an adequate atrial septal opening, followed by several days of stabilization before proceeding with operation. Management as described earlier continues during transport to the operating room and during surgery until CPB is instituted. The operation can be performed using continuous CPB by way of antegrade cerebral perfusion or using hypothermic circulatory arrest, according to choice of the operating surgeon. Both techniques are described in text that follows.

Neurologic development following operations for HLHS is below normal. Although impaired neurologic development is multifactorial, there is little question that circulatory arrest is contributory. Antegrade cerebral perfusion provides the advantage of continuous blood flow and oxygenation to the brain; however, it is possible that this technique also introduces new risks. It is unlikely that techniques of reconstruction that avoid circulatory arrest will result in dramatic changes in short-term survival, because factors related to hypothermia, CPB itself, and myocardial ischemia are not avoided. Long-term benefits related to neurologic development may exist but are yet to be proven.

There are two major approaches to the conduct of the Norwood operation, one using continuous antegrade cerebral perfusion and one using deep hypothermic circulatory arrest. Excellent results have been achieved using both approaches and a consensus is emerging that the choice of technique is one that is best left to experience and preference of the operating surgeon and team, although one should be preferentially employed at a given institution so that maximal experience with a given technique is achieved. Within the category of selective cerebral perfusion, some centers advocate for beating heart arch reconstruction and others for continuous antegrade cerebral perfusion. Several techniques for accomplishing the Norwood procedure using continuous perfusion have been described. ^, Fig. 51.8 describes in detail the various surgical steps with that technique. ^,

Norwood procedure using continuous antegrade cerebral perfusion. (A) A 6F or 8F arterial cannula is placed directly into base of brachiocephalic artery for systemic perfusion. Venous cannulation is through the venae cavae. Because of small diameter of the brachiocephalic artery, accuracy is required during this cannulation. Specifically, cannula must not be positioned so deep into the lumen that inflow obstruction occurs because tip of cannula is against back wall of artery. Alternatively, to avoid direct cannulation, a PTFE shunt is sutured to brachiocephalic artery and cannulated by arterial cannula. (B) During core cooling on cardiopulmonary bypass, pulmonary trunk is transected above sinutubular junction. Distal pulmonary trunk is closed primarily with a running monofilament absorbable 7-0 suture. Alternatively, the distal pulmonary trunk is closed with a pulmonary homograft patch. Once target core temperature is reached, aorta is clamped just proximal to brachiocephalic artery, and cardioplegia is introduced into ascending aorta. (C) Proximal ascending aorta is then incised down to proximal aorta marking suture, and the side-to-side connection between proximal pulmonary trunk and ascending aorta is accomplished with interrupted 7-0 monofilament suture in standard fashion, paying careful attention to previously placed marking sutures on proximal aorta and proximal pulmonary trunk. (D) Small neurovascular clips are placed individually at the bases of brachiocephalic, left carotid, and left subclavian arteries. Additionally, not shown in figure, a clamp is placed on descending aorta beyond ductus arteriosus. Previously created proximal ascending aortic incision is then extended distally around the arch beyond the ductal insertion site, approximately 10 mm onto descending aorta. Aorta is then reconstructed with an allograft patch, beginning distally at end of aortic incision on descending aorta, with posterior suture line followed by anterior suture line, and completing the reconstruction by suturing proximal end of patch around the cut edge of proximal pulmonary trunk. Once aortic reconstruction is completed, vascular clamps are removed, full body perfusion reestablished, and rewarming commenced. (E) Completed aortic arch reconstruction. To complete the procedure using a systemic-to-pulmonary shunt, an appropriately sized tube of expanded polytetrafluoroethylene (PTFE) is chosen and connected from systemic circulation into pulmonary circulation. Brachiocephalic artery and its branches and right pulmonary artery must be controlled with side-biting vascular clamps. (F) Completed aortic arch reconstruction. To complete the procedure using a right ventricle-to-pulmonary artery conduit, an appropriately sized tube of PTFE, or, as shown, composite of PTFE and valved allograft, is used. Prior to placing the conduit, the composite graft is constructed during the initial cooling phase of cardiopulmonary bypass. An aortic or pulmonary allograft valved conduit, either 6- or 7-mm diameter (or a 9- or 10-mm diameter allograft reduced to a bicuspid conduit) is connected end to end to a 3-cm length of PTFE graft. Valved conduit is placed distally within the composite, as shown. A 5- to 6-mm diameter core of infundibular free-wall myocardium is removed from right ventricle just below pulmonary valve. It is critical to remove a uniform full-thickness core of tissue rather than just incise the hypertrophied right ventricle; this prevents stenosis at the inlet to the conduit. Great care should be taken not to injure pulmonary valve or chordae of tricuspid valve (infundibular incision and tissue core removal can, if preferred, be performed before reperfusion of myocardium is initiated; this may provide more controlled conditions). Distal aspect of allograft conduit is connected end to side into transverse pulmonary artery centrally, either near the suture line that closed the distal pulmonary artery stoma created by previous pulmonary trunk transection, or into the patch used to close distal pulmonary artery stoma. This is accomplished with a running suture technique using 7-0 nonabsorbable monofilament suture. Pulmonary arteries are allowed to assume their natural position, and the PTFE proximal portion of the composite is tailored to appropriate length and beveled in preparation for proximal anastomosis of PTFE component to infundibulotomy site. (G) Proximal anastomosis of conduit to infundibulotomy is performed with a running stitch using 6-0 nonabsorbable monofilament suture.

After median sternotomy, the thymus is subtotally removed and the anterior pericardium opened widely. Aortic arch vessels are dissected well above the brachiocephalic vein. The small aorta is separated from the pulmonary trunk and right PA, and the ductus arteriosus, aortic arch, and proximal descending thoracic aorta are dissected and mobilized.

The brachiocephalic artery is isolated, and a 3- or 3.5-mm polytetrafluoroethylene (Gore-Tex) graft is cut on a bevel and sewn to the brachiocephalic artery using fine polypropylene suture. Hemostasis is obtained at this site, after which heparin is administered. The graft is cannulated with an 8F arterial cannula. A purse-string suture is placed in the right atrial appendage, and the right atrium is cannulated with an appropriately sized metal tipped angled venous cannula. CPB is instituted, and the patient is cooled to 18°C. ( Fig. 51.8 A). The ductus arteriosus is isolated with a lubricated silk tie and tourniquet, and the tourniquet is cinched down. The aortic arch, bilateral branch PAs, and the distal aorta are mobilized. The recurrent laryngeal nerve is retracted with a coated malleable retractor, and three full levels of intercostals are identified and divided with electrocautery taking care to avoid injury to the recurrent laryngeal nerve. Once the arch is completely dissected and mobilized, the main PA is transected 1 to 2 mm proximal to the bifurcation of the right and left PA ( Fig. 51.8 B and C). If a right ventricle to PA conduit is planned, the pulmonary valve is inspected, and the optimal implantation site for the proximal right ventricle to PA conduit is selected and marked with stay stitches on the right ventricle. The distal main PA is closed primarily or preferably with a pulmonary homograft patch. The tourniquet on the PDA is released to demonstrate hemostasis at the patch of the PA, and the PDA is ligated. The bilateral branch PAs are mobilized. When the patient reaches 18°C, tourniquets are cinched on the head vessels, a clamp is placed on the distal arch, circulatory arrest is initiated, and cardioplegia is administered down the aortic cannula. In cases where the ascending aorta is of acceptable size to safely place a cardioplegia needle, a purse-string stitch and cardioplegia needle are placed in the ascending aorta and antegrade cardioplegia is administered. The right atrial cannula is clamped and removed, and the right atrial appendage is opened further toward the belly of the right atrium, allowing full exposure of the atrial septum. The atrial septum is resected completely under direct vision. The right atrial cannula is replaced, and selective cerebral perfusion is instituted at 18°C.

If a coarctation ridge is present, the coarctation segment is completely resected. If there is no coarctation ridge, the back wall of the aorta is left intact. The cut on the undersurface of the aortic arch is extended proximally into the ascending aorta to the level of the transected main PA. A vertical incision is made in the pulmonary root just to the left of the posterior commissure if the ascending aorta is 1 to 2 mm. This generally allows for an optimal lie of the ascending aorta to neoaortic root. 8-0 Prolene is used in either an interrupted or running manner to construct the proximal neoaortic anastomosis. In cases where the native aorta is larger, the neoaortic anastomosis is positioned above the top of the commissures. The aortic arch and ascending aorta are reconstructed with a pulmonary homograft patch ( Fig. 51.8 D). Once complete, the arch can be assessed by insufflation of saline through the RV incision across the neoaortic valve. Then the systemic pulmonary shunt is completed during rewarming ( Fig. 51.8 E).

If a right ventricle to PA conduit is used the proximal anastomosis is constructed using the dunk technique ( Fig. 51.8 F and G). Two 5-0 polypropylene stay sutures are placed opposite each other including endocardium to support the opening to facilitate easy and atraumatic dunking of the previously prepared 5- or 6-mm ringed Gore-Tex graft. In general, the graft is 5 cm long, and three rings of the graft are dunked. This ensures that the first ring is inside the ventricle, eliminating proximal stenosis, and two rings are positioned in the wall of the right ventricle. Two purse strings may be used to stabilize the proximal connection, and simple sutures are used to further anchor the proximal anastomosis as needed. Clamps are then removed, and perfusion is reestablished to the head, heart, and body. The proximal anastomosis is left open briefly to de-air with the head in Trendelenburg position. Rewarming continues as the distal anastomosis is constructed to the homograft patch in the main PA, with either a primary anastomosis or with a dunk technique as well. CPB is gradually discontinued, followed by modified ultra filtration. Intraoperative transesophageal echocardiogram (TEE) is obtained and may be supplemented with epicardial echocardiographic evaluation to further visualize the distal anastomosis, the bilateral branch PAs, the proximal anastomosis, and the reconstructed arch. Heparin is reversed with Protamine, and the patient is decannulated.

The majority of patients (512) in the Single Ventricle Reconstruction (SVR) trial underwent a period of deep hypothermic circulatory arrest (DHCA), an established method for repair. Exposure is excellent, but time is more critical, and circulatory arrest times in excess of 40 minutes are associated with a greater risk of major complications as was identified in the Boston Circulatory Arrest Trial. Also, outcomes with selective cerebral perfusion have not demonstrated conclusive superiority over DHCA. The heart is exposed by median sternotomy, removal of most of the thymus gland, and opening of the pericardium. If the patient is unstable because of increased pulmonary blood flow, the right PA can be exposed immediately and clamped to reduce overall pulmonary blood flow and maintain systemic circulation until CPB is established.

The patient is prepared for CPB by placing a purse-string suture on the pulmonary trunk just distal to the pulmonary valve. A second purse-string suture is placed around the tip of the right atrial appendage. At that point, if the patient is physiologically stable, the pulmonary trunk is separated from the ascending aorta using either scissors or electrocautery. The ductus arteriosus, aortic arch, and arch vessels are then mobilized using scissors or electrocautery all the way to the first set of intercostal vessels on the descending aorta. Temporary snares are placed around all brachiocephalic arteries.

If the patient becomes physiologically unstable, CPB can be initiated at any time and the great vessel dissection performed with its support. CPB is established using an arterial cannula in the pulmonary trunk and a single venous cannula in the right atrial appendage ( Fig. 51.9 A). At initiation of CPB, the branch PAs are temporarily occluded with clamps or snares to eliminate pulmonary blood flow.

Norwood procedure using hypothermic circulatory arrest. (A) Arterial cannula is placed into pulmonary trunk through a purse-string suture, and the single venous cannula is placed into right atrial appendage. Dashed line on proximal pulmonary trunk shows intended transection site, and dashed line on ascending aorta and aortic arch shows site and extent of intended aortic incision. Marking sutures are placed on pulmonary trunk and ascending aorta precisely where the two dashed lines in this figure converge. After these two marking sutures are placed, aorta and pulmonary trunk should be allowed to assume their natural positions. Under these conditions, examining the two marking sutures with the vessels in their distended state should reveal that these two sutures are touching each other, without even the slightest amount of circumferential or longitudinal offset. As soon as cardiopulmonary bypass (CPB) is instituted, left and right pulmonary arteries must be controlled with either snares or small vascular clamps (not shown in this figure). (B) After target core temperature is reached, circulatory arrest is instituted and myocardial protection addressed; ductus arteriosus is ligated and transected as shown. It is common practice to temporarily occlude brachiocephalic, left carotid, and left subclavian arteries with snares or small vascular clamps before opening the aorta. Either at this point or following arch reconstruction, atrial septum must be resected. A limited right atriotomy is made and the septum primum identified and resected with scissors. Septum primum should be resected completely, but care taken not to overextend the resection into thickened portion of limbus or conduction area. Right atriotomy is then closed with a running monofilament suture. Dashed lines signify point of pulmonary trunk transection and extent of ascending arch and descending aortic incision. Note that the descending aortic incision extends approximately 5 to 10 mm beyond the ductal insertion site. (C) Pulmonary trunk has been transected. There is often very little distance between top of pulmonary valve commissures and origin of right pulmonary artery. During pulmonary trunk transection, care should be taken not to injure the commissure of the pulmonary valve or extend incision into orifice of right pulmonary artery. Once transection is completed, the stoma in the distal pulmonary trunk is closed transversely as shown with a running 7-0 absorbable monofilament suture. Incision in aorta is also shown. Proximal extent of this incision is terminated precisely at previously placed marking suture. (D) Before beginning arch augmentation, allograft patch is tailored to the size of the infant. Patch is roughly triangular in shape; base of triangle will ultimately be sutured to circumference of proximal pulmonary trunk, so width of base should roughly equal circumference of pulmonary trunk. Other two free edges of patch will be anastomosed to posterior and anterior free edges of incised aorta. The edge of the patch that will be sutured to posterior aspect of incised aorta should be shorter than edge that will be sutured to anterior free edge of aorta. If this is not the case, or if entire patch is too long, kinking of reconstruction can result. Also, apical half of the triangularly shaped patch should not be too broad. Patch is sewn into place beginning at most distal aspect of aortic incision, well beyond ductal insertion site. A running 7-0 monofilament nonabsorbable suture is used and posterior suture line is developed first, extending roughly to area opposite brachiocephalic artery origin. Following this, anterior suture line is developed in like fashion. (E) Distal aspect of patch suture line is completed. Attention is then turned to proximal aspect of aortic incision and to proximal pulmonary trunk. Interrupted 7-0 monofilament nonabsorbable sutures are placed to connect proximal ascending aorta to proximal pulmonary trunk. First suture in this series of five to seven interrupted sutures should be placed precisely at the points of the two previously placed marking sutures. Once this is completed, proximal end of patch is connected to circumference of proximal pulmonary trunk. Prior to final sutures being placed, a probe that can comfortably pass into proximal aorta to the level of coronary arteries is used to confirm patency and appropriate alignment of proximal aorta. (F) Completed aortic arch reconstruction. To complete procedure using a systemic-to-pulmonary shunt, an appropriately sized tube of expanded polytetrafluoroethylene (PTFE) is chosen and connected from systemic circulation into pulmonary circulation. If shunt is placed during circulatory arrest, vascular clamps generally are not necessary. However, if shunt is placed after reestablishing CPB, brachiocephalic artery and its branches and right pulmonary artery must be controlled with side-biting vascular clamps. (G) Completed aortic arch reconstruction. To complete procedure using a right ventricular–to–pulmonary artery conduit, an appropriately sized PTFE tube or, as shown, composite of PTFE and valved allograft is used. Before placing conduit, composite graft is constructed during initial cooling phase of CPB. An aortic or pulmonary allograft valved conduit, either 6- or 7-mm diameter (or a 9- or 10-mm diameter allograft reduced to a bicuspid conduit) is connected end to end to a 3-cm length of PTFE graft. Valved conduit is placed distally within the composite, as shown. Next part of procedure can be performed either under circulatory arrest or after perfusion has been reestablished. A 5- to 6-mm diameter core of infundibular free-wall myocardium is removed from right ventricle just below pulmonary valve. To prevent stenosis at the inlet to the conduit, it is critical to actually remove a uniform full-thickness core of tissue rather than just incise the hypertrophied right ventricle. Great care should be taken not to injure pulmonary valve or tricuspid valve chordae. Distal aspect of allograft conduit is connected end to side into transverse pulmonary artery centrally, either near suture line that closed the distal pulmonary artery stoma created by previous pulmonary trunk transaction, or into the patch used to close distal pulmonary artery stoma. This is accomplished with a running suture technique using 7-0 nonabsorbable monofilament suture. Pulmonary arteries are allowed to assume their natural position, and PTFE proximal portion of composite is tailored to appropriate length and beveled in preparation for proximal anastomosis of PTFE component to right ventriculotomy site. (H) Proximal anastomosis of conduit to infundibulotomy is performed with a running stitch using 6-0 nonabsorbable monofilament suture.

After initiating CPB, while the pulmonary trunk and aorta are still distended with blood, 7-0 monofilament sutures are placed on adjacent portions of the pulmonary trunk and ascending aorta to mark the point of eventual pulmonary trunk-to-aorta anastomosis. Positions of these marking sutures are chosen with great care because they will determine the correct orientation of, and incisions in, the aorta and pulmonary trunk necessary for creating a functional anastomosis; alignment of this anastomosis is critical for unobstructed coronary blood flow in aortic atresia. The first marking suture is placed in the adventitia of the pulmonary trunk 1 to 2 mm above the sinutubular junction and circumferentially exactly where the small ascending aorta lies against it. The second suture on the aortic adventitia is placed so that its position coincides exactly with the pulmonary trunk suture (see Fig. 51.9 A).

When the nasopharyngeal or tympanic membrane temperature reaches 16°C to 18°C after cooling with CPB for an appropriate period (see Section IV of Chapter 2 ), the snares around the brachiocephalic vessels are tightened and circulatory arrest established. Snares around the left and right PA are removed, and cannulae are removed from the pulmonary trunk and right atrial appendage after draining as much blood volume from the patient into the pump-oxygenator as possible.

Management of myocardial protection is variable. Some experienced centers use no specific cardioplegia and rely on profound hypothermia as the only form of myocardial management. Other experienced institutions use cardioplegia, which can be supplied in several ways. Cannulation of the ascending aorta can be achieved with an appropriately small needle and cardioplegia delivered directly into the aortic root. Alternatively, the cardioplegia system can be connected to the arterial cannula in the pulmonary trunk, and cardioplegia delivered into this cannula after circulatory arrest has been established while the brachiocephalic vessel snares and PA branch snares are still in place. The only additional maneuver before proceeding with cardioplegia delivery using this method is to clamp the descending aorta distal to the ductal insertion site. The cardioplegic solution is delivered through the arterial cannula into the pulmonary trunk through the ductus and retrograde around the arch to the coronary arteries. All other peripheral runoff through this circuit must be reliably eliminated.

After myocardial protection has been addressed and circulatory arrest established, the ductus arteriosus is ligated distal to the origin of the left PA. A small atriotomy is made, and through it the entire septum primum is removed to create an unrestrictive interatrial communication. To avoid conduction problems, care is taken not to extend the resection beyond the septum primum. The atriotomy is closed ( Fig. 51.9 B).

The pulmonary trunk is divided transversely as proximally as possible without risking damage to the pulmonary valve, leaving the previously placed marking suture proximal to the transection. As the transection is made, particular care is taken to avoid the orifice of the right PA. The distal end of the divided pulmonary trunk is then closed with a patch (typically autologous pericardium or PA allograft) using continuous 7-0 polypropylene. Alternatively, the distal pulmonary trunk may be closed primarily in transverse fashion ( Fig. 51.9 C ). Direct closure has the advantages of time efficiency and less bulk and in experienced hands has shown no greater tendency to result in pulmonary trunk stenosis than the patch technique.

The ductus is transected just beyond the previously placed ligature. Redundant ductal tissue is cut away from the distal aorta, leaving a small cuff of ductal tissue at the level of the aortic isthmus. A 5- to 10-mm incision is made from the ductal orifice into the descending aorta to the level of the first set of intercostal vessels (see Fig. 51.9 C). A proximal incision is made beginning at the ductal orifice and moving retrograde toward the aortic valve. This incision proceeds along the undersurface of the aortic arch and extends down the hypoplastic ascending aorta to within several millimeters of the atretic or hypoplastic aortic valve, terminating at the same level as the transected pulmonary trunk at the point of the previously placed marking suture (see Fig. 51.9 C).

The aorta is then augmented throughout its length from the level of the aortic valve around the arch, to the first set of intercostal vessels, using a patch of pulmonary or aortic allograft tissue ( Fig. 51.9 D). The patch is tailored to provide adequate but not excessive widening of the aorta. Suturing begins at the distal end of the incision beyond the isthmus on the upper descending aorta and progresses retrograde until the proximity of the brachiocephalic artery is reached. The posterior suture line is developed first, using a running technique and 6-0 or 7-0 nonabsorbable monofilament suture, followed by the anterior suture line.

At this point, the allograft augmentation of the arch is temporarily set aside, and the proximal end of the divided pulmonary trunk is anastomosed side to side to the incised hypoplastic aorta ( Fig. 51.9 E). This portion of the anastomosis is typically performed with five to seven interrupted 6-0 or 7-0 monofilament nonabsorbable sutures. The first of these connects the end of the aortic incision to the cut edge of the pulmonary trunk exactly where the previously placed marking suture was positioned. On each side of this interrupted suture, two to three other interrupted sutures are placed, attaching first the posterior and then the anterior edge of the longitudinally incised aorta to the circumference of the proximal pulmonary trunk. Care should be taken with small aortas (<3 mm diameter) not to connect them to too broad a segment of pulmonary trunk circumference, because this can stretch the aortic tissue and flatten and obstruct the orifice leading to the coronaries.

Finally, the allograft patch suture line progresses from the level of the brachiocephalic artery down to the aortic-to-pulmonary anastomosis and around the remaining free edge of the proximal pulmonary trunk ( Fig. 51.9 F). This completes the right ventricular-to-systemic arterial outflow reconstruction.

The last step in the operation is creating a source of pulmonary blood flow. At the choice of the operating surgeon, this can be achieved using either a restrictive systemic arterial–to–pulmonary arterial shunt or a restrictive right ventricle–to–pulmonary arterial conduit. If a shunt is chosen, typically an interposition graft is sewn into place from the junction of the brachiocephalic and right subclavian arteries on the systemic side to the proximal portion of the right PA (see Fig. 51.9 F). Both anastomoses are performed using end graft–to–side artery connections with running 7-0 monofilament or polytetrafluoroethylene (PTFE) suture. Variation in positioning of the PTFE shunt must be considered, based on individual patient characteristics, to achieve an appropriate balance of pulmonary and systemic blood flow.

In patients weighing less than 3 kg and in those demonstrating very low Rp preoperatively, it may be necessary to perform the systemic pulmonary arterial shunt anastomosis at a more distal site on the right subclavian artery. In most cases, a 3.5-mm diameter PTFE tube graft is used for the shunt procedure; a larger diameter is rarely necessary. Often in patients weighing less than 3 kg and most frequently in patients weighing less than 2.5 kg, a 3.0-mm diameter graft should be considered, although risk of shunt thrombosis may increase with a smaller-diameter shunt. If circulatory arrest is prolonged, or by surgeon preference, the shunt may be placed after reestablishing flow on CPB.

If a RV-PA conduit is chosen, a PTFE graft of appropriate diameter is selected. Alternatively, a composite graft consisting of a proximally positioned PTFE tube and a distally positioned small (6- to 7-mm diameter) allograft pulmonary or aortic valve can be used ( Fig. 51.9 G and H). Regardless of whether a simple conduit or composite conduit is chosen, the diameter of the PTFE tube determines the resistance to flow into the PAs. Typically, a 4-mm diameter graft is used for patients weighing less than 3 kg, a 5-mm diameter graft for those between 3 and 4 kg, and a 6-mm diameter graft for those greater than 4 kg.

An incision is made in the infundibular portion of the right ventricle, just below the pulmonary valve. A 5- to 6-mm diameter circular full-thickness resection of infundibular muscle is then made. It is extremely important that the caliber of the resulting hole in the infundibulum is maintained transmurally to prevent premature stenosis at this level postoperatively. Using a running 7-0 monofilament suture, the graft is first sewn end to side to the pulmonary trunk, either to the PA directly, adjacent to the suture line that previously closed the distal pulmonary trunk, or to the center of the patch that was used to close the distal pulmonary trunk. The graft is then positioned to the left of the reconstructed aorta and tailored in length to reach the infundibulotomy. The proximal end of the graft is carefully beveled to the appropriate angle to ensure a smooth course around the large, reconstructed aorta.

The anastomosis is performed using a running 6-0 monofilament suture. The right atrial and systemic arterial cannulae are reinserted, CPB is reestablished, and rewarming begun. If a systemic-to-pulmonary shunt has been placed, it is occluded with a vascular clamp during the rewarming phase of CPB. When the patient’s tympanic membrane or nasopharyngeal temperature reaches 25°C to 30°C, perfusate ionized calcium concentration is measured and calcium chloride added to bring the ionized calcium concentration to a normal level. Separation from CPB is accomplished and decannulation achieved. Details of post-CPB management follow.