Overall, in most patients with pulmonary stenosis and intact ventricular septum, the anatomic defect is confined to the pulmonary valve, with a near normal right ventricle, tricuspid valve, main pulmonary artery, and branch pulmonary arteries. In the classic form, the valve is dome shaped with a narrow central opening and preserved valve motion. The pulmonary valve leaflets may be tricuspid, bicuspid, unicuspid, or dysplastic in nature. Regardless of the structure, the leaflets are often thickened with varying degrees of fibrosis with underdeveloped commissures. The pulmonary valve is commonly a uniform fibrous cone with a circular, central, and stenotic orifice and two or three ridges on its pulmonary arterial side ( Fig. 36.1 ). These ridges radiate from the central orifice to the periphery and outline two or three cusps that correspond to pulmonary sinuses of Valsalva, which are usually well formed. The valvar diaphragm is considerably thicker than normal cusp tissue, particularly around the ostium, but it is mobile. Thickening is produced by an increase in myxomatous tissue.

Specimen from a neonate with congenital valvar pulmonary stenosis and intact ventricular septum viewed through open, dilated pulmonary trunk. Fibrous cone with its central, very stenotic orifice; well-formed sinuses of Valsalva; and potential three-cusp valve structure are typical. Moderate right ventricular hypoplasia coexists (see Fig. 36.3 ).

Obstruction may be due to thickened, shortened, and rigid cusp tissue with little or no commissural fusion, known as pulmonary valvar dysplasia . This was described in 1969 by Koretzky, Edwards, and colleagues and further characterized by Stamm, Anderson, and colleagues. The dysplastic subtype occurs in approximately 20% of all patients with pulmonary stenosis. Unlike other anatomic variants, dysplastic pulmonary valves are associated with hypoplasia of the pulmonary anulus, narrow infundibulum, and hypoplasia main pulmonary artery. This tricuspid valve structure consists of thickened cusps composed of myxomatous tissue with little or no fusion. The right ventricular–pulmonary trunk junction (anulus) may be narrowed and the pulmonary trunk wall pulled inward or tethered at the site of commissural cusp attachment. The valve is often bicuspid. Although this condition may cause critical pulmonary stenosis in neonates, stenosis is typically moderate, a finding that is characteristic of Noonan syndrome. ^,

Although it has been reported that in about 50% of neonates with critical pulmonary stenosis, right and left pulmonary arteries appear to be moderately or severely hypoplastic when imaged, at least one study suggests that this is uncommon unless RV cavity size is severely reduced. ^, As a rule, the appearance of pulmonary arterial hypoplasia is probably secondary to low pulmonary blood flow, because the pulmonary arteries are usually normal in size within a few years in those who survive interventional treatment. Patients with rubella syndrome have a greater incidence of branch pulmonary stenosis associated with pulmonary valvar stenosis.

Rarely, the RV cavity is severely reduced in size. More commonly, mild or moderate reduction is present ( Fig. 36.2 ). Reduction in cavity size relates in part to the amount of concentric RV hypertrophy produced by the RV outflow tract (RVOT) obstruction ( Fig. 36.3 ).

Cumulative frequency distribution of right ventricular (RV) cavity size in neonates with congenital pulmonary stenosis or atresia and intact ventricular septum. Zero represents normal RV cavity size, −5 represents severe RV hypoplasia, and +5 represents massive RV enlargement. The figure is based on data for 247 neonates. Only data for 82 patients with pulmonary stenosis and 136 with pulmonary atresia permitted an estimate of RV cavity size. PA, Pulmonary atresia; PS, pulmonary stenosis; RV, right ventricular.

(From Hanley FL, Sade RM, Freedom RM, Blackstone EH, Kirklin JW. Outcomes in critically ill neonates with pulmonary stenosis and intact ventricular septum: a multiinstitutional study. Congenital Heart Surgeons Society. J Am Coll Cardiol . 1993;22:183.)

Specimen from a neonate with pulmonary stenosis and intact ventricular septum and moderate right ventricular (RV) hypoplasia. (Same specimen as in Fig. 36.1 .) (A) External dimensions of RV are moderately reduced, with displacement of left anterior descending coronary artery (arrow) toward the right. (B) Opened RV shows almost complete obliteration of apical half of sinus portion of cavity by closely packed muscular trabeculations. These have had to be divided, along with the free wall, to display the potential cavity. Some dysplasia of tricuspid valve is apparent, with cusp thickening and shortening and abnormally attached and thickened sparse chordae. (C) Somewhat stenotic tricuspid valve viewed from right atrial aspect. Its circumference was 32 mm, as was the mitral anular circumference. This heart is similar in some respects to those with pulmonary atresia and intact ventricular septum (see “ Morphology ” in Section IV). A, Heavily trabeculated apical portion of cavity; Ao, aorta; FO, foramen ovale; IVC, inferior vena cava; LV, left ventricle; PT, pulmonary trunk; RA, right atrium; RV, right ventricle; TV, tricuspid valve.

Histologic appearance of the right ventricle varies. Concentric RV hypertrophy is characterized by increased muscle cell size and diffuse fibrosis. The former is greater in the fibers near the endocardial surface; in some areas, muscle fibers can be seen to be disintegrating. Fibrosis is diffuse or patchy, but papillary muscles are the most severely affected. Fibrosis increases pari passu with hypertrophy and probably results from imbalance in the myocardial oxygen supply/demand ratio. Fibrosis of both endocardium and trabeculations is a marked feature when the right ventricle is hypoplastic, contributing to poor compliance.

Neonates with critical pulmonary stenosis occasionally have severely enlarged right ventricles. This may represent coexisting important cardiomyopathy or (rarely) tricuspid valve disease. Prognosis is poor with or without valvotomy.

About 50% of neonates have normal tricuspid valve dimensions (within 2 standard deviations of the mean value for normal persons of the same size; see “ Dimensions of Normal Cardiac and Great Artery Pathways ” in Chapter 1 ; see also Chapter 26 ). In the others, diameter is smaller than normal; in less than 10% the tricuspid valve is severely hypoplastic ( Fig. 36.4 ). When it is markedly hypoplastic, it is apt to be grossly abnormal as well, with abnormal chordal attachments and fused cusps. Otherwise, the cusps and chordae usually are normal.

Cumulative frequency distribution of diameter of tricuspid valve, expressed as z-value, in neonates with congenital pulmonary stenosis (blue curve) or atresia (red curve) and intact ventricular septum. The z-value of zero represents mean normal value, −2 represents 2 standard deviations (SD) below mean normal size, and +2 represents 2 SD above mean normal size. Figure is based on data for 247 neonates. Only data for 44 patients with pulmonary stenosis and 77 with pulmonary atresia permitted an estimate of tricuspid valve size. PA, Pulmonary atresia; PS, pulmonary stenosis.

(From Hanley FL, Sade RM, Freedom RM, Blackstone EH, Kirklin JW. Outcomes in critically ill neonates with pulmonary stenosis and intact ventricular septum: a multiinstitutional study. Congenital Heart Surgeons Society. J Am Coll Cardiol . 1993;22:183.)

About 10% of neonates with critical pulmonary stenosis have RV sinusoids, but only 2% have RV coronary arterial fistulae. RV-dependent coronary circulation in critical valvar pulmonary stenosis is rare.

The right atrium is usually large. There is generally at least a patent foramen ovale, and right-to-left shunting across it is a major contributor to arterial desaturation exhibited by many of these neonates.

RV cavity size and tricuspid valve dimension are not highly correlated in this condition, but mild to moderate hypoplasia is the rule in both locations. This is in contrast to pulmonary atresia and intact ventricular septum (see Section IV ), suggesting that reduction in RV cavity size in critical pulmonary stenosis is secondary to RV hypertrophy and thickening from outflow obstruction, rather than from genetic or developmentally induced hypoplasia. This is in harmony with the hypothesis that critical pulmonary stenosis develops relatively late in fetal life, in contrast to some types of pulmonary atresia.

Unlike pulmonary atresia, in which associated cardiac defects may developmentally occur independent from the valve disease, most of the cardiac defects associated with pulmonary stenosis are the result of the physiologic impact of the valvular stenosis. Poststenotic dilation of the main pulmonary artery is frequent and more prominent in children that present at a later age. RV hypertrophy is secondary to the pressure load created by distal obstruction. Significant tricuspid regurgitation may occur because of anular dilation and chordal stretching from the pressure load within the right ventricle.

Ebstein malformation, which occurs in about 5% of patients with pulmonary atresia and intact ventricular septum, occurs in about 1% of those with critical pulmonary stenosis.

The first description of balloon dilation of the pulmonary valve was by Kan and colleagues in 1982 utilizing radial forces of a balloon positioned across a stenotic pulmonary valve. Currently, balloon valvuloplasty has replaced surgical intervention as the initial treatment for moderate to severe pulmonary valve stenosis. The procedure’s safety and excellent outcomes has made this the “gold standard” for treatment of this disease. The procedure is associated with less regurgitation than surgery with similar incidence of restenosis. ^,

The procedure is generally performed via percutaneous access through the femoral vein. A pressure catheter is guided into the right ventricle for initial assessment of the pressure and anatomy, to include an angiogram of the right ventricle and RVOT. In most instances, the RV pressure is suprasystemic prior to balloon valvuloplasty. RV-to-systemic pressure ratios of 1.3 to 1.5 are common. Gradients across the pulmonary valve are difficult to interpret because there is frequently trivial forward flow across the valve and the pulmonary artery pressure is elevated in the neonate with a large PDA. Balloon valvuloplasty results in an immediate drop in the RV pressure, but the RV-to-systemic pressure ratio generally remains around 0.75 to 0.85. Complications associated with this procedure are rare. ^,

Transient bradycardia, premature ventricular beats, and a brief drop in systemic blood pressure are common. Other complications reported are blood loss requiring transfusion, complete right bundle branch block, permanent or transient heart block, stroke, and cardiac arrest. In about a quarter of patients, opening the pulmonary valve obstruction unmasks severe RV infundibular obstruction. This will generally improve with time and rarely needs to be addressed surgically.

When percutaneous balloon valvotomy has been unsuccessful, open pulmonary valvotomy using CPB is recommended. The surgical procedures of closed pulmonary valvotomy and open valvotomy with simple inflow stasis have also given good results; however, they are not currently recommended in most circumstances. ^, Operation may be performed using one or two venous cannulae and CPB with mild (32°C–34°C) hypothermia as described in Chapter 2 . A single venous cannula may be used when a patent foramen ovale is present and two venous cannulae are chosen when an atrial septal defect (ASD) will be closed.

Before establishing CPB, the ductus arteriosus is dissected and ligated immediately after initiating CPB. After establishing CPB and hypothermia, the aorta is clamped and cold cardioplegia administered (see Chapter 3 ). Alternatively, operation may be done on the beating heart, without aortic clamping.

If two venous cannulae are used and an ASD is to be closed, a small-caliber vent can be placed into the left side of the heart through a purse-string suture in the right pulmonary vein. Alternatively, the right atrium is opened through a small oblique incision, and a pump sump-sucker is placed across the foramen ovale and into the left atrium.

The pulmonary trunk is opened through a vertical incision, and fine stay sutures are placed on the edge of the incision for exposure. Two or three fused commissures can usually be seen, and these are opened with a scalpel, extending the incisions to the RV–pulmonary trunk junction. Because regurgitation is of less concern than residual narrowing, the incisions may be tailored to some extent to ensure that the valve has a wide opening. Portions of the valve are excised only when other methods fail to achieve a wide opening. Less commonly, the valve is dysplastic with three fully formed commissures and markedly thickened, even bulky, cusps. In this case, cusp debulking by partial resection of tissue is necessary to relieve obstruction. Rarely in neonates is there a need to resect RV infundibular muscle. The pulmonary trunk is closed with one row of continuous 7-0 polypropylene suture. Usually, operation requires less than 15 minutes, and the aortic clamp, if used, is simply removed and de-airing accomplished. The remainder of the operation is completed in the usual manner.

If a patent foramen ovale is present, it is usually left open because the right ventricle is very hypertrophied and noncompliant. The patient will benefit from allowing right-to-left atrial shunting until the right ventricle remodels. If an ASD coexists, the decision is more complex because it is likely the patient will eventually develop significant left-to-right shunting through it once RV remodeling is complete. If there is concern that RV size and hypertrophy will result in perioperative RV failure, the ASD should be left open; it can be addressed at a later time once the right ventricle has remodeled. If the right ventricle is judged to be adequate, the ASD should be closed. Regardless of the initial decision, the physiology should be assessed carefully in the operating room following separation from CPB, and surgical readjustments (either opening or closing the ASD) made as necessary. Remainder of the operation is completed in the usual manner.

A concomitant systemic–pulmonary artery shunt may be added if Pao ₂ is severely reduced (<30 mmHg) after discontinuing CPB. The neonate usually comes to the operating room well resuscitated by prostaglandin E ₁ (PGE ₁ ).

Consideration should be given to placing a fine polyvinyl catheter into the right ventricle, inserted through the right atrium across the tricuspid valve. It is used perioperatively to monitor RV pressure and typically is removed 48 hours later in the intensive care unit. Measurements in the operating room after repair are not as informative and cannot serve as a guide to concomitant infundibular resection.

Transesophageal echocardiography should be used routinely to assess the outflow tract after separation from CPB, paying particular attention to gradients at the valvar and infundibular level, degree of pulmonary and tricuspid valve regurgitation, RV function, and presence and degree of interatrial shunting.

Although the likelihood of needing a transanular patch (TAP) is greater when the RV cavity is small, the decision to place one at the initial surgical procedure is generally best made during operation. When surgery is performed as a secondary procedure, the decision is usually made preoperatively. The operation proceeds as described earlier for open pulmonary valvotomy. The interior of the RV infundibulum is inspected by looking through the pulmonary valve orifice. If it appears to be narrowed and if the diameter of the opened pulmonary valve (and thus presumably the “anulus”) has a z-value of −3 or less (see discussion of z-value in “ Standardization of Dimensions ” under Dimensions of Normal Cardiac and Great Artery Pathways in Chapter 1 ; see also Chapter 26 ), and particularly when the RV cavity is very small, a TAP is probably indicated.

Incision in the pulmonary trunk is carried across the anulus and down to the junction of the sinus and infundibular portions of the right ventricle. The pulmonary valve cusps may be excised if severely dysplastic. Conservative resection of hypertrophied muscular trabeculae in the infundibulum may be accomplished, but this is often impractical in neonates. An enlarging patch is fashioned from glutaraldehyde-treated or untreated autologous pericardium and sewn into place with continuous 6-0 or 7-0 polypropylene sutures (see “ Decision and Technique for Transanular Patching ” in Section I of Chapter 34 ). Remainder of the procedure, including placing the polyvinyl catheter, is as described in the preceding text. A systemic–pulmonary artery shunt is added only if Pao ₂ is severely reduced after discontinuing CPB.

If a systemic–pulmonary artery shunt is required as an isolated procedure (see “ Special Features of Postoperative Care ” later), a polytetrafluoroethylene (PTFE) interposition aortopulmonary shunt is made using a 3.5- or 4-mm tube via a median sternotomy. Whether shunting is an isolated procedure or concomitant to valvotomy or transanular patching, the PTFE tube is placed between the brachiocephalic trunk–right subclavian artery junction and the right pulmonary artery (see “ Technique of Operation ” in Section I of Chapter 34 ).

About 75% of neonates successfully undergoing pulmonary valvotomy require no further procedure for at least 4 years. About 10% remain hypoxic and require a systemic–pulmonary artery shunt. In a few, repeat balloon valvotomy is needed. About 10% of those not initially receiving a TAP will need one at some point. Rarely (<2%), a two-ventricle system cannot be attained, and a superior cavopulmonary anastomosis or Fontan-type operation is ultimately required. Similarly, Rao reported a 25% incidence of reintervention following initial balloon valvotomy.

Occasionally, closure of an ASD is required as the right ventricle remodels and important left-to-right shunting develops in patients in whom the ASD was purposefully left open at the time of the neonatal procedure. The long-term implications of severe pulmonary regurgitation, primarily in those patients who received a TAP, remain unclear. In patients who fail to develop adequate Sao ₂ (>85% at rest) and right atrial pressure (<12–15 mmHg at rest) with the atrial septum and any systemic–pulmonary artery shunt temporarily closed, a superior cavopulmonary anastomosis can be considered to reduce the workload of the right ventricle, allowing closure of the ASD and systemic–pulmonary shunt. Occasionally, a Fontan-type operation is ultimately indicated.

Limited information is available concerning residual gradients. In about 90%, any important residual gradient has disappeared or been overcome by repeat percutaneous valvotomy within 6 to 12 months of the initial procedure. Ultimately, the RV–pulmonary trunk gradient is usually about 20 mmHg. ^, In unusual cases in which the gradient remains above about 50 mmHg, transanular patching is warranted. The mechanism by which percutaneous balloon valvotomy effects its good results is generally the ideal one of commissural splitting; tearing of pulmonary valve tissue is uncommon. The exception may be the dysplastic pulmonary valve, in which commissural fusion is not the dominant problem causing obstruction. Although Stamm, Anderson, and colleagues emphasize that balloon valvotomy is ineffective, based on morphologic characteristics of dysplastic valves, reports vary as to effectiveness of this procedure in this setting.

Although some neonates initially have at least moderate reduction in RV cavity size, late after pulmonary valvotomy the RV cavity is normal or only mildly reduced in size in 90%. In only about 10% does an important degree of infundibular obstruction, cavity narrowing, or both persist. Following balloon valvotomy, pulmonary anulus and RV chamber size increase, cusp mobility improves, and cusp thickening resolves in the majority of cases studied by echocardiography 6 months to 8 years after intervention.

Whereas most patients have tricuspid regurgitation initially (in some cases, severe), more than 80% have no regurgitation late after valvotomy. However, in a few patients, moderate or severe regurgitation persists, and it is likely that the tricuspid valve is somewhat dysplastic in these patients. Pulmonary regurgitation following balloon valvotomy occurs with increasing frequency and severity over time in 41% to 88% of patients. ^, Need for surgical insertion of a pulmonary bioprosthesis for progressive valve regurgitation is unusual but reported.

When presentation is outside the neonatal period, the degree of pulmonary valve pathology tends to be lesser. The spectrum can range from mild fusion of the valve leaflets to severe stenosis. In more severe forms, there is less clear separation of the thickened and immobile leaflets. The pulmonary valve is usually better developed in infants and children presenting with severe stenosis than it is in infants. ^, In those presenting as infants, the anulus is often narrow, and the valve appearance is less differentiated into clear cusps.

In adults, the valve may become calcified, particularly when there has been preexisting infective endocarditis. In older patients, a variable amount of infundibular hypertrophy results in secondary infundibular stenosis. Occasionally, infundibular stenosis alone accounts for RVOT obstruction ( Table 36.1 ).

Poststenotic dilation of the pulmonary trunk (see Fig. 36.5 ) is characteristic of this malformation and is present in about 70% of infants and children with this lesion. ^, Rarely, dilated segments of pulmonary artery may cause compression of the airways. The left pulmonary artery may be involved as well.

In older patients, in contrast to neonates, important hypoplasia of the right ventricle is uncommon, although marked thickening of the ventricular wall is often seen. When this thickening involves the infundibular septum and free wall of the right ventricle, severe subvalvar obstruction gradually develops. This has been anecdotally referred to as the “suicidal right ventricle” when the severely hypertrophied and obstructed right ventricle develops severe and sudden dynamic outflow tract obstruction with hemodynamic collapse following valvotomy. In occasional cases, a low-lying and large moderator band or so-called anomalous muscle bands contribute to infundibular obstruction. In about 10% to 20% of patients, these are the only sites of obstruction, the valve being either normal or (rarely) bicuspid, but not stenotic.

In infants and children, the tricuspid valve is usually morphologically normal. However, mild regurgitation or, in the case of RV failure, moderate or severe regurgitation may develop.

The right atrial wall is hypertrophied secondary to increased right atrial pressure. In about one fourth of infants and adults, the atrial septum is intact. However, in most the foramen ovale is patent, or there is a small ostium secundum ASD; right-to-left shunting results in cyanosis. ^, When a left-to-right shunt is present, there is usually a large ASD and only mild or moderate pulmonary stenosis.

Alterations in the left ventricle (e.g., myocardial infarction, myocardial dysplasia, obstructive changes in the coronary arteries, abnormal media of the ascending aorta) have been shown occasionally to coexist with pulmonary stenosis and intact ventricular septum. ^, Muscular subaortic stenosis of the variety seen in hypertrophic obstructive cardiomyopathy may coexist. A combination of muscular subaortic and subpulmonary obstruction may be associated with abnormal facies and is a possible variant of Noonan syndrome. Important valvar pulmonary stenosis in infants and children can adversely affect left ventricular (LV) function. This is largely the result of RV hypertension that displaces the septum toward the left and alters LV geometry. Cardiac output and LV function are adversely affected, but the abnormalities revert to normal after correction of the RV outflow obstruction.

Pulmonary stenosis and intact ventricular septum occur frequently in Noonan syndrome, which is characterized by small stature, hypertelorism, mild mental retardation, cardiac malformations (most commonly pulmonary stenosis), and at times ptosis, undescended testes, and skeletal malformations. ^, It is also associated with intrauterine rubella.

Infants may be symptomatic but usually have less severe symptoms than neonates. After the first year, patients often present because of a murmur only, produced by mild or moderate stenosis. In the second, third, and fourth decades, presentation may be with chronic RV failure. In all, 30% to 40% of patients are asymptomatic when first examined. ^, When symptoms occur, the earliest is often effort dyspnea, which results from inability to increase pulmonary (and thus systemic) blood flow with exercise because of the relatively fixed resistance of the pulmonary valve. ^,

Cyanosis appears when, in the presence of an interatrial communication, the right ventricle becomes less compliant than the left ventricle or its pressure becomes severely elevated. With a normally developed right ventricle, this occurs only when its pressure is suprasystemic and is associated with ECG evidence of considerable RV hypertrophy. When cyanosis is marked in older patients, polycythemia becomes severe, and all the complications associated with this condition can develop (see “ Clinical Presentation ” under Clinical Features and Diagnostic Criteria in Section I of Chapter 34 ). However, these patients rarely squat for symptomatic relief as do those with tetralogy of Fallot. ^,

Effort-related precordial pain is not uncommon and is presumably due to RV angina. Sudden death can occur in cyanotic and acyanotic children and in young adults. ^,

Patients in the second and third decades of life with severe and long-neglected pulmonary stenosis and intact ventricular septum show development of right heart failure with elevated jugular venous pressure, hepatomegaly, and ascites, which eventually leads to death.

Except in young infants with severe heart failure, a systolic murmur (best heard in the second left interspace) is present, often with a thrill. Peak intensity of the murmur occurs later in systole in those with severe rather than mild stenosis. The pulmonary component of the second sound may be normal, decreased, or inaudible, whereas the aortic component is usually obscured by the murmur. The tighter the pulmonary stenosis, the longer the RV ejection time and the greater the delay in pulmonary valve closure. ^,

In severe stenosis, an ejection click is absent because the dome of the pulmonary valve is pushed upward into the pulmonary trunk by the vigorous right atrial contraction before ventricular systole occurs. In some patients with mild stenosis, the abnormality of cusp movement may be insufficient to produce a click, although in other patients it may be prominent, the sound being magnified by a dilated pulmonary trunk.

The hypertrophied right ventricle can often be appreciated as an RV heave palpable to the left of the sternum. The jugular venous “a” wave increases in amplitude as pulmonary stenosis increases in severity and is made more obvious by a noncompliant right ventricle. In older children, diagnosis of associated RV hypoplasia is suspected when signs of pulmonary stenosis are combined with heart failure and cyanosis in the absence of severe RV hypertrophy on the ECG. Thus, in contrast to pulmonary stenosis with a normally developed right ventricle, cyanosis may occur when its pressure is less than systemic and the ECG is unremarkable. ^,

Right atrial enlargement from moderate or severe pulmonary stenosis is reflected in prominent P waves in the ECG. When pulmonary stenosis is mild or moderate, the R-wave height in V ₁ is less than 10 mm, or there is a pattern of incomplete right bundle branch block. When it is severe, the R or R′ in V ₁ becomes greater than 10 mm and corresponding in its height to degree of RV hypertension.

In children and adults, as well as neonates, two-dimensional echocardiography can provide near-certain diagnosis. The thickened, immobile, or domed pulmonary valve can be imaged, along with poststenotic enlargement of the pulmonary trunk and RV thickening. Severity of stenosis can be estimated by Doppler evaluation of the flow across the pulmonary valve in systole, and this can be confirmed by similar evaluation of the velocity of flow in the tricuspid valve regurgitant jet, if present. Echocardiography can also be used to diagnose restrictive RV physiology by demonstrating forward flow across the pulmonary valve in late diastole. This physiology can be present in up to 42% of adults with moderate or severe stenosis and correlates with increased symptoms.

Unlike in the neonatal population, the measurement of pressure gradients may be more accurate, with few confounding variables. Classification of the degree of stenosis is based on pressure gradients across the RVOT, usually obtained by Doppler echocardiogram evaluation. Generally, a pressure gradient across the pulmonary valve below 40 mmHg is considered mild, gradients of 40 to 80 mmHg moderate, and gradients greater than 80 mmHg severe. The degree of stenosis may also be classified by the RV systolic blood pressure. The stenosis may be considered mild when the RV systolic pressure is less than half systemic arterial blood pressure, moderate when it is above half but less then systemic systolic blood pressure, and severe when it is greater than systemic systolic blood pressure.

Techniques and findings are the same as those described in Section II.

Patients who survive the neonatal period to present later in infancy have a wide variation in degree of pulmonary valve narrowing. About 40% (CL 32%–47%) have mild obstruction, 47% (CL 39%–54%) moderate, and only 14% (CL 9%–20%) severe. However, these percentages probably underestimate the proportion of patients in this age group with severe obstruction. Nugent and colleagues found that 58% (CL 51%–64%) of an unselected group of infants presenting in the first 2 years ( n = 81) with this entity had severe RV outflow obstruction. Even in early life, and probably more so as time passes, infundibular (muscular) narrowing adds to RV output resistance.

When RV outflow obstruction is severe in infants and young children, heart failure, cyanosis, or both are common (more so than in older patients who have developed the same degree of obstruction). ^, Prognosis of this group is poor. Levine and Blumenthal found that 56% of patients with heart failure died during follow-up.

Even when obstruction is moderate in this young age group, an important proportion have heart failure, with its same poor prognostic implication. It is probable that a degree of RV hypoplasia is often implicated in heart failure under these circumstances. According to Mody’s study of 17 patients with moderate RVOT obstruction in the first year, 53% (CL 38%–68%) experienced progression to a severe lesion in the next several years (average 4.5 years). Similar conclusions can be drawn from the data of Wennevold and Jacobsen and Danilowicz and colleagues. ^,

Even in asymptomatic infants with mild stenosis, Anand and Mehta reported rapid progression requiring intervention within 6 months in 15%. Experience of others, however, contradicts this, indicating that progression of mild pulmonary stenosis (gradient of <40 mmHg) in infants is rare and is similar to the natural history of mild pulmonary stenosis diagnosed in older children. ^,

Patients with isolated pulmonary stenosis that produces mild RV outflow obstruction (peak pressure gradient between RV and pulmonary trunk ≤25 mmHg or RV peak pressure ≤50 mmHg) have a predicted probability of survival equal to that of an age-gender-ethnicity–matched general population. These patients rarely experience progression of pulmonary stenosis and therefore rarely require interventional therapy. ^, Recent studies by Rowland and colleagues and Gielen and colleagues corroborate earlier findings. ^,

Patients with moderately severe obstruction (peak pressure gradient between right ventricle and pulmonary trunk >25 mmHg but <50 mmHg, or RV peak pressure >50 mmHg but <80 mmHg) sometimes experience progression in severity of their RV outflow obstruction. Without progression, as best as can be gleaned from currently available information, predicted probability of survival for at least 25 years is excellent.

Patients with severe pulmonary stenosis are susceptible to eventual development of chronic heart failure (and thus premature death), the tendency being greater the older the patient. Secondary changes in the severely stenotic valve probably make it more obstructive as time passes, with the outflow tract becoming more hypertrophied and stenotic and the right ventricle becoming thicker, more fibrotic, less contractile, and less compliant. In women with severe pulmonary stenosis who are in New York Heart Association functional class I or II, pregnancy is not associated with an increase in fetal or maternal complications, in contrast to similar disease of the mitral or aortic valve.

RV hypoplasia seems to affect natural history unfavorably. However, some patients with hypoplasia do not die in infancy but present later in life, usually with progressive cyanosis from a right-to-left shunt at atrial level. Left untreated, progressive right heart failure develops and causes death.

In infants, children, and adults, as in neonates, percutaneous balloon valvotomy is the treatment of choice for valvar pulmonary stenosis. If this is not successful, or is not indicated, open surgical valvotomy using CPB is performed. Balloon valvotomy is ineffective in most cases of dysplastic pulmonary valve, and when the valve anulus is hypoplastic (z-value < −3). The surgical technique is described in Section I. When transanular patching is necessary, the technique is also that described in Section I.

The general aspects of operation described in Section II are applicable to pulmonary valvotomy in infants and adults. After the pulmonary trunk is opened through a vertical incision, valvotomy is performed ( Fig. 36.6 ). When edges of the cusps are bulky and obstructive, and particularly when the valve is bicuspid, partial or complete valvectomy may be necessary, because a taut bicuspid valve cannot open properly even after incision of the two fused commissures. RV, LV, and pulmonary artery pressures are measured at this point, but they are of little value in decision making (see “ Special Features of Postoperative Care ” later). A polyvinyl catheter is placed to measure RV pressure. It can usually be advanced forward from the right atrium through the tricuspid valve. Pressure measurements made the following morning may indicate the need for return to the operating room for relief of infundibular or anular stenosis.

Pulmonary valvotomy through pulmonary trunk during cardiopulmonary bypass. (A) Overview showing vertical incisions in pulmonary trunk and high right ventricle (RV). (B) View of funnel-like stenosis of pulmonary valve. (C) Commissures are incised sharply with a knife. As this is done, the surgeon and an assistant must carefully stabilize the cusp on either side to avoid inaccuracy in making the incision. If necessary, thickened valve tissue around the orifice may be resected, or a cusp may be partially detached. However, this is done only if the opening is otherwise unacceptable, because some degree of regurgitation results. When infundibular dissection and resection are also required, RV is opened through a vertical incision in the infundibulum. After performing the dissection and resection, vertical ventriculotomy is closed with a small oval patch of polytetrafluoroethylene or pericardium inserted with continuous polypropylene suture.

When an infundibular resection is indicated ( Fig. 36.7 ), a vertical infundibular incision is preferred. After resection, the incision is closed using an oval-shaped patch of PTFE or pericardium. In a few patients, a TAP is required because of a small pulmonary valve anulus. Patients requiring this often have dysplastic pulmonary valves. Cineangiogram or echocardiogram may suggest need for the TAP, but the final decision is usually made in the operating room. At the time of valvotomy through the pulmonary arteriotomy, the anulus is sized with Hegar dilators. If it is small (z-value of −3 or less), the arteriotomy is carried across the anulus and down the infundibular free wall. If there is doubt about the need for transanular patching, the pulmonary arteriotomy is left open and a vertical incision made in the infundibulum.

Infundibular resection for pulmonary stenosis with intact ventricular septum. In contrast to the situation in tetralogy of Fallot, this is a resection of muscle from the entire circumference of the severely hypertrophied outflow tract. (A) Approach is through a vertical incision that will be closed with a polytetrafluoroethylene (PTFE), polyester, or pericardial patch as in tetralogy of Fallot. (B) Working from below upward, muscle is cored out with a knife up to valve level. More muscle can be excised from recesses in front of either end of the infundibular septum than elsewhere. Excision is often also necessary from the walls (anterior, medial, and lateral) for a short distance below ventriculotomy. (C) Both the pulmonary trunk incision and ventriculotomy are closed with small oval patches of PTFE, polyester, or pericardium. RV, Right ventricle.

After muscle resection has been accomplished, the anulus is again sized by Hegar dilators passed through the valve from below. If it is too small, the two incisions are joined by cutting across the anulus, and a TAP is inserted (see “ Decision and Technique for Transanular Patching ” under Technique of Operation in Section I of Chapter 34 ). Delon and colleagues have described a reconstructive operation for patients with dysplastic pulmonary valve with hypoplastic anulus that preserves valve function. However, the experience involves only two patients, and follow-up is limited.

In the occasional patient with stenosis of the pulmonary trunk or branches that cannot or has not been treated adequately by balloon dilation and stenting, the narrowed pulmonary branch is dissected to a point beyond the stenosis and an enlarging repair made (see “ Technique of Operation ” in Section I of Chapter 34 ). Preliminary dissection of these branches is best made during CPB cooling. These stenoses must be identified in detail at preoperative cardiac catheterization.

Immediate relief of the gradient usually is obtained, and it is rare for adequate initial relief of obstruction to be temporary. On average, a peak RV pressure of 128 mmHg before valvotomy is reduced to 51 mmHg shortly after valvotomy. Completeness of relief of pulmonary stenosis can be determined only by late postoperative studies because of the usual, but not invariable, tendency for RV peak pressure to decrease over time after valvotomy. ^, This decline is believed to be due primarily to regression of RV hypertrophy and lessening of infundibular narrowing. ^{, , ,} It is known, however, that adequate isolated pulmonary valvotomy does not invariably provide excellent relief of pulmonary stenosis, even in infants. Roos-Hesselink and colleagues report a low but definable incidence of restenosis. In 64 patients with follow-up ranging from 22 to 33 years, the reintervention rate was 15%. Two patients required reoperation for recurrent RVOT obstruction at 2 and 3 years after initial surgery, and two required subsequent balloon dilation at 16 and 18 years postoperatively, respectively. Additionally, six other patients required surgical reintervention, ranging from 16 to 24 years postoperatively, for severe pulmonary regurgitation. Five of these six had a TAP placed at initial operation. Moderate to severe pulmonary regurgitation was present at late follow-up in 37% of patients.

Earing and colleagues, on the other hand, reported more concerning long-term reintervention. In 53 patients with a mean follow-up of 33 years, reintervention for recurrent pulmonary stenosis was similarly low, but 21 patients (40%) required pulmonary valve replacement for severe regurgitation. This may reflect the extremely long follow-up, because other authors have recognized the progressive increase in symptomatic pulmonary regurgitation the longer the follow-up; however, equally important is that this cohort of patients underwent their original surgery in a different era. To this point, in this study, closed pulmonary valvotomy was importantly associated with need for late reoperation.

Hemodynamic results after percutaneous balloon valvotomy are similar to those just described (see Results in Section II). Fawzy and colleagues report a reduction in pulmonary valve gradient from 105 mmHg to 34 mmHg in their series of 90 patients (mean age 24 years). The infundibular gradient was large immediately following the procedure in 43 patients, all of whom underwent later recatheterization. The gradient decreased from 42 mmHg following the initial procedure to 13 mmHg at repeat study. Other reports document similar results.

Gudausky and Beekman summarize results from five large studies reported between 1994 and 2003. A total of 866 non-neonatal cases were included. Restenosis occurred in 20%, with 7% requiring repeat balloon valvotomy and 7% requiring surgery. Severe pulmonary insufficiency was present in 1%. Freedom from either surgical or balloon reintervention at 5 and 10 years after intervention, reported by Rao and colleagues, was 88% and 84%, respectively ( Fig. 36.8 ).

Actuarial reintervention-free rates after balloon dilation of pulmonary valve. At 1, 2, 5, and 10 years, these were 94%, 89%, 88%, and 84%, respectively.

(From Rao PS, Galal O, Patnana M, Buck SH, Wilson AD. Results of three to 10 year follow up of balloon dilatation of the pulmonary valve. Heart . 1998;80:591).

Peterson and colleagues studied comparative outcomes between surgical and balloon valvotomy. Between 1969 and 2000, 62 patients underwent surgery and 108 balloon valvotomy. Both techniques were effective, but there were differences at 10-year follow-up. Surgery reduced the gradient across the pulmonary valve more effectively than balloon valvotomy and had lower rates of restenosis and overall reintervention. Balloon valvotomy had a lower rate of moderate pulmonary regurgitation, which did not appear to influence reintervention rates in the two groups. Nevertheless, balloon valvotomy is today the procedure of choice because of its lower cost, shorter hospital stay, lower degree of invasiveness, and effectiveness. Based on the study of Earing and colleagues, it can be inferred that the reintervention rate in the surgery group studied by Peterson and colleagues will continue to rise with longer follow-up as symptoms from pulmonary regurgitation develop.

Cyanosis may persist late postoperatively when the foramen ovale or ASD is not closed, even when stenosis has been relieved, as a result of impaired RV compliance. This can occur occasionally with a normally developed, severely hypertrophied right ventricle, presumably secondary to diffuse fibrosis, but it is the rule in the hypoplastic right ventricle. Data from Freed and colleagues suggest that the reversed atrial shunt may lessen as an infant or young child grows and as the right ventricle increases in size, and later closure of the ASD thus may not be required. This favorable sequence cannot be expected in patients with hypoplastic right ventricle, and it is well known that important hypoxia can occur from a right-to-left shunt through a small atrial communication.

The sinus portion of the right ventricle enlarges and becomes normal in size in most patients. The infundibulum enlarges in many patients, but as in tetralogy of Fallot (see Chapter 34 ) a narrow pulmonary anulus may fail to enlarge as the child grows. The apparent size of the pulmonary arteries increases, and in most patients, they become normal sized. Tricuspid regurgitation, even when severe preoperatively, is usually absent or mild late postoperatively.

Most patients have an excellent late functional result. Stone and colleagues have shown that during exercise, children who have undergone pulmonary valvotomy have a normal relationship between cardiac output and oxygen consumption, no increase in RV end-diastolic pressure (preoperatively it increased), and less increase than preoperatively in RV peak systolic pressure.

The late result in patients with a hypoplastic right ventricle is inferior to that in patients with a normally developed ventricle. Late mortality is higher, there may be a reversed shunt through an unclosed atrial communication, and there may be residual infundibular obstruction. There may also be persistent or recurrent right heart failure despite complete relief of stenosis. Although there are no techniques proven to be beneficial in managing the hypoplastic right ventricle, several options are available in selected cases. Late heart failure may be prevented in this group, particularly in those who are young, by a complete valvotomy combined with enlargement of the RV cavity by excision of trabeculations. This may be particularly helpful if extensive endocardial fibrosis is present. In patients with persistent RV failure, volume unloading by creating a bidirectional superior cavopulmonary anastomosis may be beneficial.

When the right ventricle is severely hypoplastic, symptoms and signs are substantially altered. Important symptoms are not necessarily present in infancy, but when they appear they tend to progress rapidly. Classically, there is a markedly prominent a wave and reversed (expiratory) splitting of the second heart sound. Pulmonary stenosis with hypoplastic right ventricle is associated with less than the expected degree of RV hypertrophy, and in severe hypoplasia, LV forces are dominant despite severe stenosis. ^, Balloon valvotomy may not be as effective in this group because of (1) frequent presence of organic infundibular obstruction, (2) necessity of closing the atrial communication to abolish the otherwise persistent right-to-left shunt, and (3) probable benefits of enlarging the RV cavity by excising muscle from its sinus portion. Taking all these factors into consideration, a surgical approach may be required. However, when severe heart failure is present, prognosis is still poor with any approach. In this setting, reducing volume load on the right ventricle by performing a superior cavopulmonary anastomosis may be of benefit.

The rarest form of pulmonary stenosis and intact ventricular septum is supravalvar pulmonary stenosis. It has been called hourglass pulmonary stenosis and is characterized by narrowing of the sinutubular junction, similar to that seen in supravalvar aortic stenosis. This lesion, like pulmonary valve dysplasia, does not respond to balloon dilation ; surgery is required. Various technical approaches have been described, all similar to those described for supravalvar aortic stenosis (see Section III of Chapter 50 ). The technique of repair can involve patching from the main pulmonary artery across the sinutubular junction into the sinus of Valsalva. Alternatively, repair using only native pulmonary artery tissue has been described.

The nature of the structure at the junction of the RV and pulmonary trunk is arguable. Van Praagh and colleagues imply that fibrous components are pulmonary valve remnants. Others point out that in many cases there is only poorly structured imperforate fibrous tissue overlying muscular atresia. ^{, ,} In any event, commissural ridges may be prominent and converge to meet in the center of the “valve,” an appearance similar to that in pulmonary valve stenosis. In some patients, commissural ridges are present only in the periphery, the center being a smooth fibrous membrane. In the combined UK-Ireland multicenter study of 183 patients, 75% had membranous atresia and 25% muscular atresia. Of greater importance is the nature of the structures immediately below the RV–pulmonary trunk junction (see “ Right Ventricle ” and “ Tricuspid Valve ” in text that follows).

The pulmonary trunk is usually nearly normal in size but uncommonly is severely hypoplastic. ^{, ,} Rarely, the pulmonary trunk is represented only by a fibrous cord.

Right and left pulmonary arteries are usually normal in diameter or slightly hypoplastic. ^, Uncommonly, they are moderately or severely hypoplastic, usually in patients with severely reduced RV cavity size. Rarely, there are major arborization abnormalities of the native pulmonary arteries in association with large aortopulmonary collaterals. Four such patients have been encountered by F.L. Hanley and colleagues (personal communication, February 2012).

Size of the RV cavity is variable. In about 5% of patients, it is enlarged. Ebstein malformation and severe tricuspid regurgitation may coexist with the latter. ^{, ,} Many individuals with this combination die in fetal life. Rarely, the RV wall may be very thin ( Uhl anomaly or parchment right ventricle ) and the cavity nontrabeculated adjacent to the tricuspid valve and heavily trabeculated in its apical half.

Much more frequently, cavity size is reduced, severely so in about 60% of patients ( Table 36.2 ). This appears to be the result of massive wall hypertrophy extending into the ventricular cavity. Often, this completely obliterates the infundibular cavity, and the atresia can be termed muscular in such cases. At times, the apical-trabecular cavity is completely obliterated; in the most extreme cases, both portions are obliterated. Although these cavities are obliterated, the respective portions of the right ventricle are not absent. Cavity obliteration can be localized by echocardiography as well as by anatomic studies. Cavity obliteration has been further characterized in the UK-Ireland multicenter study. All three components of the right ventricle (inlet, trabecular, and infundibular) were present in all cases, but with different degrees of cavity obliteration from muscular ingrowth. A “unipartite” ventricle due to muscular obliteration of the infundibular and trabecular components was present in 8%. A “bipartite” ventricle due to muscular obliteration of the trabecular component alone was present in 34%. There were no cases of muscular obliteration of the infundibulum alone. A “tripartite” ventricle was present in the remaining 58%.

There is associated diffuse fibrosis of the hypertrophied muscle and, especially when the RV cavity is small, a modest degree of RV endocardial fibroelastosis. ^{, , ,} Bulkley and colleagues found typical myocardial fiber disarray in 69% of the RV free wall and in 73% of the ventricular septum in this condition. The potential for impaired LV as well as RV dysfunction is evident.

Coronary sinusoids, or dilated portions of the coronary microcirculation, can be detected by cineangiography in about half of patients ^, ( Table 36.3 ). In some cases, fistulous connections between the RV cavity and these sinusoids form multiple small communications into branches of left or right coronary arteries. ^{, , ,} Occasionally they converge into a single large vessel that empties into the left anterior descending or right coronary artery. In many cases, the fistulae are minor. In the multicenter UK-Ireland study, 58% of patients had completely normal coronary circulation, 15% had minor filling of the coronary arteries with RV injection at catheterization, and about 25% had major fistulae, with about one third of these having no coronary connection to the aorta.

Prevalence of RV–coronary arterial fistulae is inversely related to dimensions of the tricuspid valve (and hence of the RV cavity) ( Fig. 36.9 ) and amount of tricuspid regurgitation. It is also directly related to RV systolic pressure. ^{, ,} However, the milieu for development of fistulae may be a consequence of genetically or developmentally induced myocardial abnormalities. Immunohistochemical studies demonstrate abnormal density and orientation of capillaries and myocyte disarray in the presence of fistulae.

Nomogram of a regression equation (univariable) expressing the relation between dimensions of the tricuspid valve expressed as z-value (see “ Dimensions of Normal Cardiac and Great Artery Pathways ” in Chapter 1 ) and probability of the presence of right ventricular–coronary artery fistulae in pulmonary atresia with intact ventricular septum. RV, Right ventricle.

(From Hanley FL, Sade RM, Blackstone EH, Kirklin JW, Freedom RM, Nanda NC. Outcomes in neonatal pulmonary atresia with intact ventricular septum. A multiinstitutional study. J Thorac Cardiovasc Surg . 1993;105:406.)

Desaturated RV blood, although vital in the presence of proximal coronary obstructions, compromises myocardial oxygen supply in regions to which it is distributed by these fistulae. This may account in part for the myocardial abnormalities described later in this chapter. ^{, ,} Complexity of oxygen delivery to the myocardium is evidenced by the fact that the left anterior descending artery (or any coronary artery) may fill through these fistulae from the right ventricle in systole, and from the aorta in the normal manner during diastole. There results a spectrum of percentages of LV myocardium dependent on the right ventricle for coronary perfusion, albeit desaturated; the percentage depends on location and severity of proximal coronary artery stenoses as well as on the fistulae. At some critical point, sufficient myocardium is in jeopardy of developing such severe ischemia when RV hypertension is relieved that RV decompression becomes contraindicated as a surgical option. In an analysis by Giglia and colleagues of 16 patients with coronary angiography and subsequent RV surgical decompression, 7 of 7 (100%; CL 77%–100%) with no coronary stenosis survived, 4 of 6 (67%; CL 39%–88%) with stenosis in one major coronary survived, and 0 of 3 (0%; CL 0%–46%) with stenosis in two major coronaries survived.

When less severe coronary abnormalities are present in association with fistulae, regional LV wall motion abnormalities are commonly identifiable before RV decompression, and they increase after decompression; however, severe global LV dysfunction is unusual.

In about 10% of patients (20% of those with RV–coronary fistulae), coronary circulation or some critical part of it is derived entirely or nearly so from the right ventricle in the manner described, defining RV-dependent coronary circulation . This may occur because of development of arterial obstructions in the left main or right coronary arteries, or both, or in the proximal portion of the left anterior descending artery (R.M. Freedom, personal communication, 1991). No correlates of RV dependence are known beyond those for RV–coronary artery fistulae. Proximal coronary arterial occlusions etiologic to the dependence may develop in fetal life; some develop or progress after birth.

RV-dependent coronary circulation is a major consideration in planning therapy (see Indications for Operation later in this chapter). The difficulty is in deciding how much myocardium at risk is considered too much, triggering the management decision to avoid decompressing the hypertensive right ventricle. To address this difficulty, Calder and colleagues identified coronary abnormalities in 116 patients. They determined that presence of coronary fistulae alone did not correlate with mortality. The presence and extent of coronary interruptions, and the amount of LV myocardium that was RV dependent (determined with a 15-point scoring system), did correlate with mortality.

The problem, however, is even more complex than solely determining the amount of myocardium at risk, because even a small amount of extremely ischemic myocardium may be the source of a life-threatening dysrhythmia. Recently, LV coronary abnormalities unrelated to the presence of fistulae, sinusoids, or coronary interruptions have been discovered. Hwang and colleagues showed that patients with PA/IVS, regardless of the presence of fistulae, have decreased density of intramyocardial arterioles relative to normal and hypertrophied hearts.

The tricuspid valve is usually abnormal in this malformation. ^{, ,} Occasionally the abnormality is simply small size, but usually the leaflets are thickened and the chordae abnormal in number and attachment. Local agenesis and incomplete leaflet separation occur. The importance of these abnormalities has been emphasized by Davignon and colleagues and by Paul and Lev. ^,

In about 10% of neonates, z-value of the tricuspid valve is less than −5, and in 50% it is −2.2 or less ( Fig. 36.10 ). (See Chapter 26 for a nomogram for estimating the z-value of the tricuspid valve). Dimensions of the tricuspid valve are well correlated with those of the RV cavity, in contrast to dimensions in neonates with critical pulmonary stenosis, in whom they are not correlated. ^{, , , ,}

Relationship between diameter of the tricuspid valve (by echocardiography), expressed as z-value, and size of the right ventricular cavity (grade estimated subjectively from echocardiographic and cineangiographic studies) in patients with pulmonary atresia and intact ventricular septum ( n = 71).

(From Hanley FL, Sade RM, Blackstone EH, Kirklin JW, Freedom RM, Nanda NC. Outcomes in neonatal pulmonary atresia with intact ventricular septum. A multiinstitutional study. J Thorac Cardiovasc Surg . 1993;105:406.)

In uncommon cases in which dimensions of the tricuspid valve are large, its leaflets usually show features of Ebstein malformation, with enlargement of the anterior leaflet and downward displacement onto the ventricle of the origin of a dysplastic septal leaflet. The posterior leaflet may or may not be abnormal. These valves are usually severely regurgitant. Another pathologic lesion of the tricuspid valve has been recognized in patients with dilated right ventricle and severe tricuspid regurgitation—that of unguarded tricuspid orifice, in which the inferior (mural) leaflet is absent rather than displaced.

The right atrium is enlarged, and it is more enlarged when there is severe tricuspid regurgitation. An interatrial communication is present in all cases, usually a patent foramen ovale of adequate size. However, shortly after birth, the foramen becomes restrictive in some patients. The eustachian valve is frequently prominent.

The left atrium is usually hypertrophied and somewhat enlarged, and the mitral orifice is usually larger than normal. The LV shows some hypertrophy and endocardial fibroelastosis. A convex bulging of the interventricular septum into the LV cavity has been noted, with some speculating that this might produce subaortic obstruction. Clinical and postmortem studies have demonstrated evidence of LV myocardial ischemia in virtually all patients ^, ; perhaps related to this, LV compliance is depressed in many.

The aorta usually has adult morphology without isthmic narrowing and is usually left sided.

The ductus arteriosus is patent at birth but has the usual tendency to close. Orientation of the ductus is typical for pulmonary atresia of all forms, with an obtuse proximal and acute distal angle at its aortic attachment. Usually the bronchial arteries are normal, and important aortopulmonary collateral arteries are absent.

Other than Ebstein malformation, coexisting cardiac anomalies are uncommon.

Fetal distress is usually not evident except in those with a large right ventricle. Delivery is typically uncomplicated and at term. The babies are generally well developed ( Fig. 36.11 ) and are likely initially to appear healthy except for cyanosis. ^, Cyanosis is usually obvious on the first day and becomes rapidly more severe as the ductus closes and there is respiratory distress and progressing metabolic acidosis. ^, In the New England series, 81% of babies presented during the first week of life; in a more recent study, 94% presented in the first 3 days ( Fig. 36.12 ).

Cumulative frequency distribution of birth weight of neonates with pulmonary atresia or stenosis with intact ventricular septum. BW, Birth weight; Max, maximum; Min, minimum; PA, pulmonary atresia; PS, pulmonary stenosis.

(From Hanley FL, Sade RM, Blackstone EH, Kirklin JW, Freedom RM, Nanda NC. Outcomes in neonatal pulmonary atresia with intact ventricular septum. A multiinstitutional study. J Thorac Cardiovasc Surg . 1993;105:406.)

Cumulative frequency distribution of age at entry into the hospital of an inception cohort of neonates with pulmonary atresia or stenosis and intact ventricular septum. PA, Pulmonary atresia; PS, pulmonary stenosis.

(From Hanley FL, Sade RM, Blackstone EH, Kirklin JW, Freedom RM, Nanda NC. Outcomes in neonatal pulmonary atresia with intact ventricular septum. A multiinstitutional study. J Thorac Cardiovasc Surg . 1993;105:406.)

Absence of an RV impulse in a cyanotic infant with a palpable left ventricle should arouse suspicion of PA/IVS, tricuspid atresia, Ebstein malformation, or critical pulmonary stenosis with hypoplastic RV. ^, Typically, no murmur or a systolic murmur of tricuspid regurgitation is heard, sometimes with a thrill. ^{, ,} Despite presence of a PDA, a continuous murmur is seldom heard. ^, The second heart sound is single.

Classic findings on chest radiography include clear lung fields with diminished (or normal) vascular markings and a flat or concave pulmonary trunk segment. Heart size is variable and may be large, even when the RV cavity is small.

P waves can be normal at birth, but evidence of right atrial enlargement develops quickly, and within a few weeks, prominent right atrial P waves are uniformly present. ^{, , ,} Mean QRS axis in the frontal plane is usually normal or shows a rightward deviation, and the RV hypertrophy pattern usually present in the neonate is absent. ^, However, ECG evidence of RV hypertrophy may be present even though the RV cavity is small, precluding its use to predict RV cavity size.

Two-dimensional echocardiography is diagnostic ( Fig. 36.13 ). Goals of echocardiography include confirmation of PA/IVS and presence/absence of pulmonary valve leaflets, determination of RV morphology and associated RV and tricuspid valve anomalies, evaluation of RV inflow and outflow dimensions, confirmation of coronary anatomy and presence of coronary dilation and fistulous connections from the right ventricle, evaluation of branch pulmonary artery size and continuity, and status of pulmonary blood flow from the ductus arteriosus. Dimensions of the tricuspid valve, RV cavity size, and nature of the outflow obstruction (membranous or muscular) can be determined with confidence. Of importance is the fact that RV–coronary artery fistulae can be identified accurately by two-dimensional echocardiography with pulsed Doppler color flow ultrasound imaging ^, ( Fig. 36.14 ). However, echocardiographic evaluation is limited: fistula size, extent of fistula formation, and presence of proximal coronary arterial stenosis cannot as yet be accurately delineated.

Intracardiac findings in pulmonary atresia and intact ventricular septum. (A) Apical four-chamber view revealing hypoplastic and massively hypertrophied right ventricular (RV) cavity. Note ventricular septum bulging into left ventricle (LV), indicating severe RV hypertension. Tricuspid valve (TV) anulus is small, about 50% of the diameter of the mitral valve (MV) anulus. A large atrial septal defect is present. (B) Apical four-chamber view with color Doppler in systole, showing severe tricuspid valve regurgitation. Right atrium (RA) is markedly enlarged. LA, Left atrium; SEP, ventricular septum.

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