Echocardiography in Pediatric and Adult Congenital Heart Disease, 2nd Ed.

13. Abnormalities of Right Ventricular Outflow

VALVAR PULMONARY STENOSIS

Background

Clinical Presentation

In the vast majority of cases, stenosis of the pulmonary valve represents a primary, congenital abnormality. In children, acquired pulmonary valve stenosis is very rare, and typically would occur as a sequela of rheumatic carditis. Regardless of etiology, the clinical presentation of valvar pulmonary stenosis can be variable. In most cases, however, patients are asymptomatic in the face of mild or even moderate pulmonary valve stenosis. With more severe degrees of pulmonary stenosis, symptoms may vary from mild dyspnea and fatigue with exertion to cyanosis and/or overt symptoms of right heart failure. In most cases, the symptoms arise from the decreased ability of the right ventricle to provide cardiac output across the stenotic valve. Signs of heart failure such as low output, hepatomegaly, and edema can be seen in the setting of high central venous pressure due to right ventricular failure in patients with severe pulmonary valve obstruction. Hypoxemia and cyanosis are classic findings in infants with critical pulmonary valve stenosis. Rarely, patients with pulmonary valve stenosis may present with syncope on exertion due to limited right heart output in the face of a severely stenotic valve. As most patients with valvar pulmonary stenosis are asymptomatic, presentation frequently occurs with auscultation of a systolic murmur. A murmur of valvar pulmonary stenosis is typically a systolic ejection murmur, heard best at the upper left sternal border. The murmur often radiates into the lung fields, being frequently more prominent in the left posterior lung field than the right. A murmur is often accompanied by a variable systolic ejection click. Electrocardiographic findings typically feature variable degrees of right axis deviation and the presence of right ventricular hypertrophy.

Anatomy and Physiology

The pulmonary valve is typically thickened and doming with restricted movement in systole. The valve is often bicuspid. In children and young adults, the pulmonary valve annulus size is typically within a normal range and the pulmonary root, sinotubular junction, and main pulmonary artery segments are also often normal in size. Post stenotic dilation of the main pulmonary artery can often be noted. In neonates and young infants, severe pulmonary valve stenosis, along a spectrum of critical pulmonary stenosis, can also be associated with a small pulmonary valve annulus and pulmonary artery segment. In some cases, a very thickened, dysplastic, myxomatous pulmonary valve can be associated with severe stenosis and hypoplasia of the main pulmonary artery segment.

Physiologically, contraction of the right ventricle against a fixed obstruction results in right ventricular systolic hypertension. As a result, variable degrees of right ventricular hypertrophy will develop relative to the degree of outflow tract obstruction. As RV hypertrophy progresses, diastolic dysfunction can develop. Impairment of right ventricular relaxation occurs relatively early during the process of hypertrophy; as the RV thickens it becomes less compliant. RV filling pressures can increase and right atrial pressure may be elevated.

Complications

In mild to moderate pulmonary stenosis, patient symptoms and cardiovascular sequelae may be minimal. In the more severe forms of pulmonary stenosis, chronic right ventricular pressure overload may result in biventricular systolic dysfunction with the development of signs and symptoms of right heart failure. Subsequent dilation of the right ventricle in the face of pressure overload can result in development of tricuspid regurgitation. Chronic right ventricular diastolic dysfunction can result in significant elevations of right heart filling pressures with right atrial dilation. In addition, when atrial level shunts are present, elevation of right atrial pressures can produce right-to-left shunting at the atrial level, producing hypoxemia and cyanosis.

Principles of Echocardiographic Anatomy and Imaging

Two-Dimensional Echocardiographic Anatomy and Hemodynamics

Two-dimensional imaging of the pulmonic valve can be performed in a number of imaging planes. In the parasternal window, the pulmonary valve can be visualized in the long axis by sweeping the plane of sound to the left and anterior from the standard view. In the parasternal short axis, the RV outflow tract and pulmonary valve are typically imaged by sweeping the plane of sound superiorly toward the base of the heart. In the apical four-chamber view, it is often possible to sweep the plane of sound anteriorly to image the subvalvar infundibulum and pulmonary valve, particularly in infants and younger children. The pulmonary valve can also be imaged in the subcostal window in both the coronal and sagittal planes.

Figure 13.1. Parasternal short-axis view of the right ventricular outflow tract. The pulmonary valve (open arrow) domes in systole. Note the anterior, leftward orientation of the stenotic outflow jet, with swirling of flow (white arrow) seen within the dilated main pulmonary artery (MPA). Ao, aorta; RVOT, right ventricular outflow tract.

On initial inspection, the stenotic pulmonary valve leaflets will appear to be variably thickened. The valve typically domes during systole due to incomplete leaflet opening (Videos 13.1 and 13.2). The pulmonary artery root and main pulmonary artery segment are typically normal in size. In many cases, there can be post stenotic dilation of the main pulmonary artery segment (Fig. 13.1, Video 13.1). The degree of post stenotic dilation in the main pulmonary artery segment does not typically correlate with the degree of pulmonary stenosis and therefore can be seen even in the setting of mild to moderate pulmonary valve stenosis. The subvalvar infundibulum is typically widely patent and normal in caliber, although with significant right ventricular hypertrophy, mild narrowing of the infundibulum may result (Fig. 13.2, Video 13.2).

Careful inspection of the supravalvar portion of the main pulmonary artery in the area of the sinotubular junction should be performed specifically to look for evidence of supravalvar narrowing (Fig. 13.3, Video 13.3). The supravalvar area is typically well seen in the parasternal long- and short-axis windows, but can also be visualized in subcostal windows and on anterior sweeps in the apical window. As the stenotic pulmonary valve typically domes at the level of the sinotubular junction, coexistent supravalvar pulmonary stenosis may be missed on 2D imaging unless this area is examined carefully. Although the pulmonary valve annulus is usually normal in size, it is often useful to measure the pulmonary valve annulus by 2D imaging. Comparison of the annulus dimension to the sinotubular junction will reveal whether the supravalvar area is significantly smaller than the annulus dimension (see Fig. 13.3); the sizes of the two areas are normally about equal. The pulmonary valve annulus is typically measured in either parasternal long- or short-axis views, although the annulus can also sometimes be adequately measured in subcostal views. Although isolated subvalvar pulmonary stenosis is rare, discrete fibromuscular narrowing of the proximal infundibulum (Fig. 13.4) should be distinguished by both 2D and Doppler echo from valvar pulmonary stenosis.

Figure 13.2. Parasternal short-axis view of the right ventricular outflow tract. The pulmonary valve domes in systole, and the annulus dimension is slightly small (open arrow). The infundibulum (inf) is hypertrophied, and appears slightly narrowed in systole. Note that the stenotic flow jet in the main pulmonary artery (MPA) is directed posteriorly in this example.

Figure 13.3. Supravalvar pulmonary stenosis. Parasternal long-axis view of the main pulmonary artery (MPA). There is discrete narrowing of the sinotubular junction (open arrow), which is significantly smaller in comparison to the pulmonary valve annulus (white arrows). AAo, ascending aorta.

Hemodynamic assessment is centered on direct estimation of the pressure gradient across the stenotic pulmonary valve, and the sequelae of valve stenosis. Doppler interrogation of the flow across the stenotic pulmonary valve is performed by pulsed-wave and continuous-wave Doppler (Fig. 13.5A). In our experience, accurate alignment of the Doppler interrogation beam with the flow jet is best obtained in either the parasternal short axis or subcostal windows. In the short axis, it will often be evident that the flow jet across the pulmonary valve is often directed more anteriorly than is typical. This somewhat atypical location for the flow jet will often correlate to the area of post stenotic dilation seen in the main pulmonary artery (see Fig. 13.1). The angle of Doppler interrogation should therefore be modified in this instance to better align with the anteriorly directed flow jet. The peak gradient across the stenotic pulmonary valve can be estimated using the modified Bernoulli equation. Color flow Doppler imaging can also allow localization of the gradient to the leaflet tips and also identify any preexisting pulmonary regurgitation due to the anatomic valve abnormality.

Figure 13.4. Subcostal sagittal view demonstrating a discrete subpulmonary membrane (white arrows) in the proximal right ventricular (RV) outflow tract (white arrows). Note the position of the membrane relative to the pulmonary valve annulus (open arrow). LV, left ventricle.

Variable degrees of right ventricular hypertension will result due to the pulmonary valve obstruction. RV pressure should be estimated, when possible, by measuring tricuspid regurgitant jet velocities using continuous-wave Doppler. Using the peak tricuspid regurgitant jet velocity, the right ventricular to right atrial systolic gradient can be estimated by the modified Bernoulli equation, and by adding an assumed central venous pressure one can solve for estimated right ventricular pressure. Estimates of central venous pressure between 6 and 10 mm Hg are typically used in most labs to perform this quantitation. In the absence of tricuspid regurgitation, indirect evidence of right ventricular hypertension should be assessed. Right ventricular hypertrophy can be quantified as right ventricular anterior wall thickness (by either M-mode or 2D imaging); however, the degree of right ventricular hypertrophy does not correlate well to the gradient across the pulmonary valve, particularly postintervention. Flattening of the interventricular septum can be seen when right ventricular pressure equals the pressure in the left ventricle; when right ventricular pressure is suprasystemic, the interventricular septum will bow leftward into the left ventricle (Fig. 13.6).

Figure 13.5. Doppler evaluation of pulmonary stenosis. A: The continuous- wave Doppler profile is consistent with fixed obstruction across a stenotic pulmonary valve. The peak instantaneous gradient across the valve in this example = 4(4.25 m/s)2 = 72 mm Hg. B: The continuous-wave Doppler flow profile is consistent with a dynamic obstruction, and predicts a peak instantaneous gradient of ∼70 mm Hg.

Variations on Classic Anatomy

Critical pulmonary stenosis In this group of patients the pulmonary valve typically consists of a thickened, domed, and often dysplastic pulmonary valve (Videos 13.4 and 13.5). In addition, the pulmonary valve annulus is often variably hypoplastic. The degree of pulmonary valvar stenosis is typically severe. The subvalvar infundibulum is often short and muscle-bound due to prominent right ventricular hypertrophy. In addition, the right ventricle is often globally hypertrophied with reduced cavitary size. Critical pulmonary stenosis typically presents in the newborn period with hypoxemia and cyanosis due to the severity of the right ventricular outflow tract obstruction with resultant elevated right heart pressures and right to left shunting at the foramen ovale.

Figure 13.6. Parasternal short-axis image of the right (RV) and left (LV) ventricles. Note that the interventricular septum bows into the LV in late systole, consistent with suprasystemic RV systolic pressure.

Critical pulmonary stenosis belongs to a spectrum of anatomy which includes severe valvar pulmonary stenosis with normal right ventricular size to pulmonary valve atresia with intact ventricular septum and severe right ventricular hypoplasia. Patients with this condition can have variable degrees of pulmonary valve, right ventricular cavity, and tricuspid valve hypoplasia (Fig. 13.7). It is therefore important on a 2-dimensional echocardiographic evaluation to quantify tricuspid valve annular dimension, pulmonary valve annular dimension, and evaluate the degree of RV hypoplasia.

Figure 13.7. Apical 4-chamber view in an infant with critical pulmonary stenosis. Note the mild hypoplasia of the right ventricle (RV), which is not apex-forming (white arrow). The tricuspid valve leaflets are also thickened, with incomplete leaflet coaptation. LA, left atrium; LV, left ventricle; RA, right atrium.

Figure 13.8. Apical 4-chamber view in an infant with critical pulmonary valve stenosis. Note multiple areas of increased echogenicity (arrows) involving the right ventricular endocardium, moderator band, and tricuspid valve apparatus, consistent with endocardial sclerosis. LA, left atrium; LV, left ventricle; RA, right atrium.

In addition to tricuspid valve annular hypoplasia, abnormalities of tricuspid anatomy and function can also be seen. On 2D imaging, severe pulmonary stenosis can be associated with echogenic areas of endocardial sclerosis which may involve the tricuspid valve papillary muscles (Fig. 13.8). The tricuspid valve function can be abnormal with significant degrees of tricuspid regurgitation (Fig. 13.9). The regurgitation may be due in part to anatomic abnormalities involving the tricuspid valve chordal apparatus and papillary muscle function, as well as due to super systemic right ventricular pressure secondary to severe RV outflow tract obstruction. In addition to assessing the severity of tricuspid regurgitation, RV pressure estimates can be obtained using the tricuspid regurgitant jet velocity by applying the Bernoulli equation (see Fig. 13.9).

Additional physiologic information that should be obtained would include the presence or absence of a ductus arteriosus, a pattern of shunting across the foramen ovale (typically right to left), and the presence or absence of a gradient across the pulmonary valve. In a sick neonate, the presence of a widely patent ductus arteriosus and the presence of elevated pulmonary vascular resistance may result in an observed pulmonary valve gradient that is relatively low, and not reflective of the degree of anatomic stenosis (Fig. 13.10). Therefore, demonstration of suprasystemic RV pressure either by tricuspid regurgitant jet velocity (see Fig. 13.9), or 2D evidence of the interventricular septum bowing prominently into the left ventricle in the parasternal short-axis scan (see Fig. 13.6), can often be the most useful physiologic evidence of severity of the pulmonary valve stenosis. In the setting of pulmonary valve atresia, the degree of RV hypoplasia, tricuspid valve hypoplasia, and associated anomalies becomes much higher.

Dysplastic pulmonary valve Occasionally, pulmonary valve stenosis can be associated with severe dysplasia of the pulmonary valve leaflets. This is most typically seen in association with Noonan syndrome. In these patients, the pulmonary valve leaflets are typically very thickened and myxomatous (Fig. 13.11, Video 13.4). Often, it is very difficult to demonstrate normal valve motion on 2D imaging. In addition to the pulmonary valve abnormality, the pulmonary valve annulus is often hypoplastic and the MPA segment beyond the pulmonary valve is also often quite small. Overall, the frequency of pulmonary valve stenosis in Noonan syndrome is approximately 25%, with pulmonary valve dysplasia occurring in approximately 7% of cases (Burch, 1993). Therapeutically, these valves typically do not respond well to balloon valvuloplasty. This is due both to the annular hypoplasia as well as the severe thickening and dysplasia of the pulmonic valve leaflets.

Figure 13.9. Color flow Doppler evaluation of tricuspid valve regurgitation in an infant with critical pulmonary valve stenosis. There is moderate tricuspid regurgitation. Continuous-wave Doppler evaluation of the regurgitant jet velocity (4.85 m/s) predicts a right ventricular pressure-right atrial gradient of 4(4.85)2 = 94 mm Hg. The estimated right ventricular pressure is therefore 94 mm Hg + central venous pressure, or approximately 100–104 mm Hg.

Figure 13.10. Subcostal coronal image of the right ventricle (RV) in a neonate with critical pulmonary valve stenosis. A: The RV is markedly hypertrophied. The pulmonary valve is thickened and doming (open arrow). B: A narrow jet of transvalvar antegrade flow is demonstrated. Note the lack of color flow aliasing; the flow velocity is low due to the presence of a large patent ductus arteriosus (not pictured).

Figure 13.11. Dysplastic pulmonary valve (open arrow) seen on anterior sweep from standard apical window. The valve leaflets are thickened and myxomatous. Note also the poststenotic dilation of the main pulmonary artery (MPA). RVOT, right ventricular outflow tract.

Common Associated Lesions/Findings

Common lesions associated with valvar pulmonary stenosis are summarized in Table 13.1.

Interventional and Postinterventional Imaging

Cardiac catheterization with balloon valvuloplasty is the treatment of choice when the pulmonary valve annulus is adequate in size and there are no concerns regarding right ventricular or tricuspid valve hypoplasia. Following balloon valvuloplasty, echocardiographic evaluation should be performed to assess for residual pulmonary stenosis gradient, post valvuloplasty regurgitation, and to evaluate right ventricular function and pressure. Occasionally, postintervention subpulmonary stenosis can be observed. In this setting–the so called “suicide right ventricle”–a typical dynamic pattern of obstruction can be observed (see Fig. 13.5B).

Isolated surgical pulmonary valvuloplasty is seldom performed in the current era. However, when the pulmonary valve annulus is hypoplastic, pulmonary valvotomy with a transannular RV outflow tract patch is typically performed to increase the size of the RV outflow tract and relieve valvar obstruction. Following transannular patching, it is typical to see moderate or greater degrees of pulmonary regurgitation, unless the transannular patching was quite limited or the surgical technique included some form of pulmonic valve prosthesis. In the setting of significant pulmonary regurgitation, it is important to follow RV size and function by serial echocardiographic study. Long-standing, significant pulmonary regurgitation can be associated with significant right ventricular dilation and dysfunction.

In the setting of severe pulmonary stenosis or atresia with a hypoplastic right ventricle, single ventricular palliation may be undertaken. Postoperative evaluation of the hypoplastic right ventricle and single ventricular surgical palliation will be discussed in the section on pulmonary atresia with intact septum.

SUBVALVAR PULMONARY STENOSIS

Background

Clinical Presentation

The clinical presentation in patients with subvalvar pulmonary stenosis and intact ventricular septum closely resembles that of isolated valvar pulmonary stenosis. Anomalous muscle bundles in the right ventricular infundibulum, i.e. “double-chambered right ventricle,” are often seen in association with a ventricular septal defect. In this setting, the ventricular septal defect may produce the most prominent clinical findings. As with isolated valvar pulmonary stenosis, when the degree of subvalvar obstruction is mild to moderate, most patients will be asymptomatic. When obstruction is severe and/or long standing, right ventricular hypertrophy and failure may result, with the accompanying clinical findings of right heart failure. On physical examination, the murmur of subvalvar stenosis is typically a long, pansystolic crescendo-decrescendo murmur which is heard at the upper left sternal border. The murmur is often heard lower down the sternal border than is typical in isolated valvar stenosis. Subvalvar pulmonary stenosis is often associated with a palpable thrill along the left sternal border. The pulmonary component of the second heart sound may be more normal than expected—in comparison to valvar pulmonary stenosis—for the degree of murmur on auscultation. A systolic ejection click should not be appreciated. Electrocardiographic findings typically feature variable degrees of right axis deviation and findings of right ventricular hypertrophy, although this will not allow one to distinguish between subvalvar or valvar pulmonary stenosis.

Anatomy and Physiology

The most common form of subvalvar pulmonary stenosis consists of hypertrophied anomalous muscle bundles narrowing the proximal right ventricular infundibulum. This malformation is also known as “double-chambered right ventricle.” Pathologically, the two “chambers” in double chamber right ventricle consist of the right ventricular sinus and inflow portions, which are upstream of the obstructive muscle bundles, and the RV infundibulum and apical trabecular right ventricle, which lay downstream of the obstructive bundles. The muscular bundles themselves appear to consist, most frequently, of hypertrophied septoparietal muscle bands which course anteriorly from the septal band on the ventricular septum to the right ventricular free wall. Some reports have suggested that the muscular obstruction is due abnormal, anterosuperior positioning of the moderator band. It is likely that the nature of the muscular obstruction can vary, and that no single mechanism accounts for all cases. One consistent finding in double-chambered right ventricle is that the downstream chamber includes both the RV infundibulum as well as some portion of the apical trabecular RV. Double-chambered RV is seen frequently in association with a ventricular septal defect, the vast majority of which are perimembranous in location, although muscular and outlet defects have been described. The ventricular septal defect may shunt into either the higher pressure “upstream” RV chamber, or the lower pressure “downstream” chamber, so this should be carefully distinguished by Doppler examination.

Primary fibromuscular infundibular stenoses can also produce subpulmonary obstruction. However, these types of obstruction are significantly rarer than double-chambered right ventricle. In one type, a discreet fibromuscular band separates the main right ventricular cavity from the infundibular chamber. Alternatively, there can be infundibular narrowing due to prominent muscular hypertrophy of the infundibular wall, producing either short or long segment subpulmonary stenosis.

Regardless of the anatomic type of subvalvar stenosis, the physiology is similar. The obstruction will produce elevated pressure in the upstream portion of the right ventricle. As these lesions often consist of a muscular narrowing, there can be a dynamic component with progressive obstruction during ventricular contraction. These findings can be exaggerated during exercise. Right ventricular hypertension is accompanied by a variable degree of compensatory hypertrophy as in other forms of RV outflow tract obstruction.

Complications

Complications relating to right ventricular outflow tract obstruction are indistinguishable from those described for valvar pulmonary stenosis. In mild to moderate outflow tract obstruction, patient symptoms and cardiovascular sequelae may be minimal. When severe, chronic right ventricular pressure overload may result in ventricular systolic dysfunction with the development of signs and symptoms of right heart failure. Right ventricular diastolic dysfunction can result in significant elevations of right heart filling pressures with right atrial dilation.

Principles of Echocardiographic Anatomy and Imaging

Two-Dimensional Echocardiographic Anatomy and Hemodynamics

Subpulmonary obstruction is often most clearly demonstrated in subcostal coronal and sagittal images, particularly in infants and young children. However, subcostal imaging often becomes technically difficult in older children, adolescents, and adults. In the subcostal window, imaging of the right ventricular sinus and the right ventricular outflow tract can be used to demonstrate both double-chambered right ventricle (Fig. 13.12AB) as well as the more uncommon subpulmonary ridge or membrane (Figs. 13.13 and 13.14). In double-chambered right ventricle, prominent muscle bundles can be seen traversing the proximal RV outflow tract obliquely on coronal or sagittal imaging (see Fig. 13.12A; Videos 13.6 and 13.7). Color flow Doppler imaging in this area will demonstrate turbulent flow originating at the level of the right ventricular muscle bundles (Fig. 13.15, Videos 13.8 and 13.9)

In the subcostal sagittal view, 2D imaging will again demonstrate the RV muscle bundles in the proximal infundibulum, coursing from the anterior RV free wall to the interventricular septal surface (see Fig. 13.12B, Video 13.7). Imaging of the right ventricular outflow tract in the parasternal long- and short-axis views can often be used to demonstrate subpulmonary obstruction. In double-chambered RV, the parasternal window can also be used to screen for a perimembranous ventricular septal defect often associated with subpulmonary obstruction. In the apical window, particularly in infants and young children, the plane of sound can be swept anterior into the right ventricular outflow tract, and both 2D and color flow Doppler utilized to diagnose and localize subpulmonary stenosis.

Figure 13.12. Subcostal imaging in double-chambered right ventricle (RV). A: Coronal image demonstrating oblique muscle bundles (open arrows) between the body of the RV and the infundibulum (inf). B: Sagittal image demonstrating muscle bundle (open arrow). LV, left ventricle.

Figure 13.13. Subcostal sagittal image demonstrating discrete membranous obstruction (white arrows) in the proximal right ventricular (RV) outflow tract. Note the position of the membrane relative to the pulmonary valve annulus (open arrow). LV, left ventricle.

Figure 13.14. Color flow Doppler evaluation of the subpulmonary membrane seen in Figure 13. Note the discrete acceleration at the level of the membrane (A). B: The peak gradient across the membrane is 20 mm Hg.

As double-chambered right ventricle often occurs in the setting of a perimembranous-outlet ventricular septal defect, care must be taken during 2-dimensional imaging to distinguish double-chambered right ventricle with VSD from an anteriorly deviated conal septum in the setting of a tetralogy of Fallot. In cases where the pulmonary valve annulus and distal infundibulum are fairly normal in size, “mild tetralogy” can sometimes be difficult to discern from a double-chambered right ventricle. Lack of aortic valve override of the VSD, normal aortic root size, and prominent hypertrophied RV muscle bundles on the anterior free wall contributing to the obstruction should help distinguish double-chambered right ventricle from tetralogy of Fallot.

Hemodynamic evaluation should focus on the assessment of stenosis severity and estimation of RV pressure. Doppler interrogation of the flow across the RV outflow tract is performed by pulsed-wave and/or continuous-wave Doppler. In our experience, accurate alignment of the Doppler line of insonation with the subvalvar flow jet is best obtained in either the subcostal or apical windows. The pattern of flow should also be noted, to distinguish between dynamic and fixed obstruction (see Fig. 13.5). The peak gradient across the RV outflow tract can be estimated using the modified Bernoulli equation.

Figure 13.15. Color flow Doppler evaluation of the right ventricular outflow tract in double-chambered right ventricle. Note the midcavitary flow acceleration (open arrow) produced by the right ventricular muscle bundles.

Variable degrees of right ventricular hypertension will result due to the subpulmonary obstruction. RV pressure should be estimated, when possible, by measuring tricuspid regurgitant jet velocities using continuous-wave Doppler. Using the peak tricuspid regurgitant jet velocity, the right ventricular to right atrial systolic gradient can be estimated by the modified Bernoulli equation, and by adding an assumed central venous pressure one can solve for estimated right ventricular pressure. In the absence of tricuspid regurgitation, indirect evidence of right ventricular hypertension should be assessed. Right ventricular hypertrophy can be quantified as right ventricular anterior wall thickness (by either M-mode or 2D imaging); however, the degree of right ventricular hypertrophy does not correlate well to the gradient across the area of stenosis. Flattening of the interventricular septum can be seen when right ventricular pressure equals the pressure in the left ventricle; when right ventricular pressure is suprasystemic, the interventricular septum will bow leftward into the left ventricle (see Fig. 13.6).

Variations on Classic Anatomy

Hypertrophic cardiomyopathy can occasionally result in subpulmonary obstruction due to septal hypertrophy impinging on the RV outflow tract. This can also be the case in infiltrative diseases of the myocardium, such as glycogen storage diseases. Intracardiac tumors such as rhabdomyoma, particularly when large, can produce subpulmonary obstruction.

Common Associated Lesions/Findings

Common lesions associated with subvalvar pulmonary stenosis are summarized in Table 13.2.

Interventional and Postinterventional Imaging

Following surgical resection of a subpulmonary membrane or RV muscle bundles, the echocardiographic evaluation should focus on assessment of residual RV outflow tract obstruction. When there has been significant RV hypertrophy in association with obstruction, there can often be some degree of dynamic RV outflow tract obstruction (see Fig. 13.5) despite an adequate surgical resection. Postintervention RV pressure estimates can also be used to quantify success of the intervention. Occasionally, aggressive resection of RV muscle bundles can produce coronary-RV cameral fistulae, which can be demonstrated by color flow Doppler imaging along the interventricular septum in the region of muscle resection.

SUPRAVALVAR PULMONARY STENOSIS

Background

Clinical Presentation

The clinical presentation of supravalvar pulmonary stenosis is similar to that of valvar pulmonary stenosis and is dependent on the severity of the pulmonary arterial obstruction. As with valvar pulmonary stenosis, patients with mild to moderate degrees of unilateral or bilateral pulmonary artery stenosis are typically asymptomatic. With more severe degrees of arterial stenosis, symptoms may include dyspnea on exertion, exercise intolerance, fatigability, and evidence of right ventricular failure. On examination, auscultatory findings may help differentiate pulmonary arterial stenoses from valvar pulmonic stenosis. A systolic ejection click, typically a feature of valvar pulmonary stenosis, is absent. The second heart sound is typically split, and the pulmonary component may be loud, particularly in the setting of multiple severe branch pulmonary arterial obstructions. With severe peripheral obstruction, prominent systolic or continuous murmurs may be heard over the lung fields and in the back. The electrocardiogram typically features the same findings as in valvar pulmonary stenosis.

Anatomy and Physiology

Supravalvar pulmonary stenosis can occur in numerous forms, ranging from isolated supravalvar narrowing of the main pulmonary artery to diffuse distal branch pulmonary arterial stenoses. The various patterns of peripheral pulmonary artery stenosis have been classified angiographically (Gay et.al., 1963). In approximately two thirds of cases, pulmonary artery stenoses are localized to the main pulmonary artery trunk, the pulmonary artery bifurcation or the proximal right and left branch pulmonary artery. Peripheral and main pulmonary artery stenoses are commonly seen in association with other types of congenital heart disease, notably tetralogy of Fallot (particularly with pulmonary atresia), and in pulmonary stenosis associated with ventricular septal defect. It has been our experience that discrete stenosis of the proximal left pulmonary artery is more common in the setting of a reverse-oriented (tortuous) ductus arteriosus seen in conjunction with conotruncal defects featuring pulmonary outflow tract stenosis. Peripheral pulmonary artery stenoses can also be seen in association with supravalvar aortic stenosis typically seen in Williams syndrome. They may also be seen in association with Noonan syndrome, Alagille syndrome, and in congenital Rubella syndrome. In these settings, diffuse pulmonary artery hypoplasia is usually the case. In addition to congenital causes of branch pulmonary aortic stenosis, acquired pulmonary artery stenosis can also exist. For example, branch pulmonary artery stenosis can occur following a surgical Waterston shunt (right pulmonary artery to ascending aortic anastomosis), Pott’s shunting (left pulmonary artery to descending aortic anastomosis), unifocalization procedures for pulmonary atresia with VSD, LPA re-implantation following pulmonary sling repair, and in transposition of the great arteries following the Lecompte maneuver.

As with valvar pulmonary stenosis, physiologic sequelae stem from right ventricular hypertension that results from contraction of the right ventricle against a fixed downstream obstruction. The degree of right ventricular hypertrophy that results will develop relative to the degree of outflow tract obstruction and RV hypertension. Diastolic dysfunction, increased right ventricular filling pressures, and right ventricular failure can ultimately result as the severity of the lesion increases.

Complications

Sequelae of supravalvar pulmonary stenosis are the same as those for valvar pulmonary stenosis. In mild to moderate stenosis, patient symptoms and cardiovascular sequelae may be minimal. The more severe forms of stenosis, chronic right ventricular pressure overload may result in ventricular systolic dysfunction and right heart failure. Dilation of the right ventricle in the face of pressure overload can result in development of tricuspid regurgitation. Chronic right ventricular diastolic dysfunction can result in significant elevations of right heart filling pressures with right atrial dilation. When an atrial level shunt is present, elevation of right atrial pressures can produce right to left interatrial shunting, producing hypoxemia and cyanosis.

Principles of Echocardiographic Anatomy and Imaging

Two-Dimensional Echocardiographic Anatomy and Hemodynamics

Two-dimensional imaging of the main and branch pulmonary arteries can be performed in a number of imaging planes; the approach to examination of the normal main and branch pulmonary arteries is discussed in detail in Chapter 2.

Careful inspection of the supravalvar portion of the main pulmonary artery in the area of the sinotubular junction should be performed specifically to look for evidence of supravalvar narrowing. The supravalvar area is typically well seen in the parasternal long- and short-axis windows (Figs. 13.16 and 13.17, Video 13.3), but can also be visualized in subcostal windows and on anterior sweeps from the apical window. Comparison of the pulmonary valve annulus to the sinotubular junction dimension will reveal whether the supravalvar area is significantly smaller than the annulus dimension; the sizes of the two areas are normally about equal.

Figure 13.16. Supravalvar pulmonary stenosis. Parasternal long-axis image of the pulmonary valve and main pulmonary artery (MPA). Note the narrowed caliber of the supravalvar ridge (open arrow) relative to the size of the pulmonary valve annulus (white arrows). AAo, ascending aorta.

Figure 13.17. Parasternal short-axis imaging of supravalvar pulmonary stenosis. On 2D imaging (left), there is discrete supravalvar narrowing. This area is substantially smaller than the pulmonary valve annulus (white arrows). On color flow Doppler imaging (right), there is a discrete flow acceleration at the supravalvar ridge (open arrow). Ao, aorta; lpa, left pulmonary artery; rpa, right pulmonary artery.

Figure 13.18. Parasternal short-axis imaging of proximal left (L) pulmonary artery stenosis (open arrow). Note the discrete reduction in vessel lumen in comparison to the size of the proximal right (R) pulmonary artery. Ao, aorta; MPA, main pulmonary artery.

Examination of the branch pulmonary arteries should be focused on identification of branch pulmonary artery narrowing. This may occur as either a discrete, focal narrowing (Fig. 13.18), or as diffuse hypoplasia of either branch pulmonary artery (Fig. 13.19, Video 13.10). Two-dimensional measurements of both proximal and more distal pulmonary artery dimensions can be compared to published normal values. These measurements are usually best made in either suprasternal notch short-axis (particularly for the right pulmonary artery) or high parasternal short-axis images. When 2D imaging of the branch pulmonary arteries is difficult, color flow Doppler can be used to improve visualization of the arteries, and identify stenoses (Figs. 13.19 and 13.20, Video 13.10). Some investigators have demonstrated that color flow Doppler imaging can be used to quantify branch pulmonary artery size, and have shown good correlation with angiographic study (Hiraishi et.al., 1994). Magnetic resonance imaging may be necessary when echocardiographic imaging is inadequate to demonstrate branch pulmonary artery anatomy, particularly if more distal stenoses are suspected.

Figure 13.19. Color Doppler demonstration of proximal right pulmonary artery hypoplasia (open arrow). Parasternal short-axis view at the base of the heart demonstrating ascending aorta (Ao), main pulmonary artery (MPA), and proximal stenosis of the right pulmonary artery.

Figure 13.20. High left parasternal short-axis image demonstrating diffuse left pulmonary artery hypoplasia (open arrow) by 2D (left) and color flow Doppler (right) imaging. MPA, main pulmonary artery; rpa, right pulmonary artery.

Pressure gradient estimates in branch pulmonary artery stenosis generally correlate poorly to catheter-derived measurements. Therefore, hemodynamic assessment should be centered on estimation of right ventricular pressure in this setting. Pressure gradients across discrete supravalvar pulmonary stenosis are more reliably estimated. Doppler interrogation of the flow across the area of narrowing is performed by pulsed-wave and continuous-wave Doppler, with the minimum possible angle of insonation during Doppler interrogation. Although absolute pressure gradient estimation in branch pulmonary artery stenosis can be limited, a characteristic “sawtooth” flow pattern—with continuous forward flow during diastole—can be seen when obstruction is significant, particularly in the setting of discrete stenoses (Fig. 13.21).

RV pressure should be estimated, when possible, by measuring tricuspid regurgitant jet velocities using continuous-wave Doppler. In the absence of tricuspid regurgitation, indirect evidence of right ventricular hypertension should be assessed. Right ventricular hypertrophy can be quantified as right ventricular anterior wall thickness (by either M-mode or 2D imaging); however, the degree of right ventricular hypertrophy does not correlate well to the gradient across the supravalvar stenosis. Flattening of the interventricular septum can be seen when right ventricular pressure equals the pressure in the left ventricle; when right ventricular pressure is suprasystemic, the interventricular septum will bow leftward into the left ventricle.

Common Associated Lesions/Findings

Common lesions associated with supravalvar obstructive lesions are summarized in Table 13.3.

Interventional and Postinterventional Imaging

When supravalvar pulmonary stenosis involves the main pulmonary artery, surgical patch arterioplasty is usually performed. With branch pulmonary artery stenosis, surgical patching techniques may be employed for proximal pulmonary artery stenosis, as well. However, when there are more distal, or multiple stenoses, catheter-based techniques are usually the therapy of choice. Catheter-based techniques include balloon angioplasty (either in the catheterization lab or intraoperative setting) or use of balloon-expandable endovascular stents. More recently “cutting” balloons have been employed to dilate difficult stenoses.

Figure 13.21. Continuous-wave Doppler evaluation of proximal left pulmonary artery stenosis in Figure 20. There is a high peak velocity (2.9 m/s) with a continuous diastolic flow gradient producing a “sawtooth” flow pattern.

Following intervention, echocardiographic imaging is used to assess efficacy of the intervention, as well as to screen for sequelae. Postintervention estimation of right ventricular pressure is the surest means of documenting a clinically effective intervention, either by direct estimation by tricuspid regurgitation velocity, or by indirect means. As in the preintervention setting, estimates of pressure gradients are generally unreliable. 2D imaging is used to document improvements in vessel caliber, as well as to rule out the presence of pulmonary artery aneurysms related to the intervention. Patency of stented pulmonary arteries may be demonstrated by 2D imaging, but due to interference with sound waves by the stent itself, color flow Doppler is often required to confirm patency. Occasionally, contraction of the vessel along suture lines (postpatch angioplasty) will result in narrowing of the vessel lumen in the mid to long term, despite adequate relief of the stenosis in the short term.

PULMONARY REGURGITATION

Background

Clinical Presentation

In children and young adults, trivial to mild degrees of pulmonary regurgitation on routine echocardiography are relatively common, occurring in approximately 75% percent of subjects. The observation that pulmonary regurgitation is more common in children than adults may be related to higher sensitivity due to higher echocardiographic image resolution in the young. Hemodynamically significant, primary pulmonary regurgitation is very uncommon in the pediatric age range. More commonly, significant pulmonary regurgitation is seen following intervention for right ventricular outflow tract obstruction or valvar pulmonary stenosis, e.g., following tetralogy of Fallot repair/right ventricular outflow tract patching or pulmonary valvotomy. Given these considerations, the clinical presentation of pulmonary regurgitation in the pediatric age range often consists of pulmonary regurgitation noted as an incidental finding on echocardiography performed for other indications. When more significant, pulmonary regurgitation can present as a diastolic decrescendo murmur heard best at the left upper and midsternal border. Much less commonly, pulmonary regurgitation can present with symptoms related to RV volume overload and right heart failure. This is much more common in a setting of long-standing pulmonary regurgitation, particularly following RV outflow tract palliative surgery such as tetralogy of Fallot repair. When symptomatic, patients typically develop exercise intolerance and, in severe cases, can present with symptoms of right heart failure, such as hepatomegaly, peripheral edema, and shortness-of-breath.

Anatomy and Physiology

The regurgitant pulmonary valve is often seen in conjunction with a stenotic valve. The valve therefore may feature variable degrees of thickening and doming in systole with cusp fusion, or less commonly, a bicuspid pulmonic valve. Prolapse of the pulmonic valve or incomplete leaflet coaptation may be seen. The degree of pulmonary regurgitation will determine the degree of right ventricular volume overload. Pulmonary regurgitation will be impacted by multiple factors. The size of the pulmonary regurgitant orifice will have a direct impact on lesion severity. The diastolic compliance of the right ventricle will impact right ventricular diastolic pressure, and thus the magnitude of the pressure gradient favoring pulmonary artery to right ventricular regurgitant flow across the pulmonary valve. Pulmonary arterial impedance will influence the propensity for forward versus reverse flow in the pulmonary artery. High impedance, e.g., anatomic pulmonary artery stenoses or high pulmonary vascular resistance, will favor retrograde flow through the regurgitant pulmonary valve.

Complications

The primary sequela of pulmonary regurgitation is right ventricular volume overload. In mild to moderate pulmonary regurgitation, the degree of right ventricular volume overload is often modest, and often well tolerated. As the degree of regurgitation becomes more severe, right ventricular volume overload increases, and the risk of developing right ventricular dysfunction increases. Right ventricular dysfunction may progress even more rapidly in the setting of severe regurgitation and residual pulmonary stenosis, although this is a much more common scenario in lesions such as repaired tetralogy of Fallot.

Principles of Echocardiographic Anatomy and Imaging

Two-Dimensional Echocardiographic Anatomy and Hemodynamics

Imaging planes and sweeps for imaging the pulmonary valve are outlined in the discussion of pulmonary valve stenosis. The regurgitant pulmonary valve is often seen in association with stenosis, so careful assessment for both is necessary. In the setting of primary pulmonary regurgitation, 2D imaging should be focused on the presence of valve leaflet prolapse or incomplete leaflet coaptation. The pulmonary valve annulus and main pulmonary artery can be dilated, particularly in the setting of connective tissue disease. 2D measurement of the pulmonary valve annulus, sinotubular junction, and main pulmonary artery should be performed and compared to normal values. These measurements, particularly of the annulus, may be important not only in identifying pathologic enlargement, but also in planning valve replacement surgery, should it become necessary. Imaging of the right and left branch pulmonary arteries should also be performed to rule out stenoses that may exacerbate the degree of regurgitation. Severe, long-standing pulmonary regurgitation may be associated with significant tricuspid regurgitation related to right ventricular and tricuspid annular dilation; thus, color flow Doppler evaluation of tricuspid regurgitation should also be performed.

In theory, the techniques described for aortic regurgitation could be used to quantify the severity of pulmonic regurgitation. However, there are multiple reasons why these techniques have not been used clinically in the pediatric population. Any method requiring 2-dimensional estimation of RV volumes would be limited by the significant difficulty in reliably estimating RV volumes by cross-sectional echocardiography. In addition, hemodynamically significant, isolated pulmonary regurgitation occurs quite rarely. Significant pulmonary regurgitation is a significant issue following transannular RV outflow tract patching in postoperative tetralogy of Fallot; however, reliable measurement of the surgically altered RV outflow tract and transected pulmonary valve annulus makes reliable estimation of transpulmonary flows difficult. For all these reasons, severity of pulmonary regurgitation is largely assessed by semiquantitative assessment of RV dimensions (assessing the degree of volume loading of the right ventricle), qualitative impressions of the size of the regurgitant jet by color flow Doppler imaging, and by color or pulsed-wave Doppler assessment of retrograde flow in the branch pulmonary arteries. In general, the presence of significant flow reversals in the distal portions of the branch pulmonary arteries is consistent with 3–4+ pulmonary regurgitation. Recently, reappraisal of Doppler methods characterizing the profile of the pulmonary regurgitant spectral display has suggested that the short duration of the pulmonary regurgitant flow relative to the total diastolic time may be associated with greater degrees of pulmonary regurgitation as seen by angiography and as estimated by magnetic resonance imaging methods (Lei, 1995; Li, 2004).

Although not related to the assessment of pulmonary regurgitant volume, it is useful to note that the pulmonary regurgitant spectral display can be utilized to estimate pulmonary artery end-diastolic pressure. By using an assumed right ventricular end-diastolic pressure, the pulmonary artery end-diastolic pressure (PAPed ) can be estimated by measuring the peak end-diastolic gradient between pulmonary artery and right ventricle (Fig. 13.22):

PAPed = ΔPPA-RV + 10mm Hg, where

ΔPPA-RV = estimated pressure gradient between pulmonary artery and right ventricle in end-diastole, and 10 mm Hg represents an assumed right ventricular end-diastolic pressure. In addition, quantitation of the peak diastolic gradient between pulmonary artery and right ventricle has been shown to correlate well with mean pulmonary artery pressure at catheterization (Masuyama et al., 1986).

Color flow Doppler imaging can be useful in demonstrating the width of the pulmonary regurgitant jet and reversal of flow in the main and branch pulmonary arteries. Reversal of flow in the main pulmonary artery due to valvar regurgitation should be distinguished from “swirling” of flow in the main pulmonary artery (see Figs. 13.1 and 13.2) as well as flow into the pulmonary artery from a patent ductus arteriosus, both of which can produce flow in the same direction as regurgitation. In both cases, flow from distal to proximal main pulmonary artery will occur in systole, occurring in later systole in the case of swirling MPA flow, and typically during both systole and diastole in the case of a patent ductus arteriosus.

Figure 13.22. Continuous-wave Doppler evaluation of pulmonary regurgitation. The end-diastolic velocity (open arrow) is high, and predicts an end-diastolic gradient of 44 mm Hg between pulmonary artery and right ventricle, consistent with high pulmonary artery diastolic pressure.

Variations on Classic Anatomy

As previously discussed, isolated pulmonary regurgitation is rare, and is most frequently seen in children following repair of tetralogy of Fallot, or in the setting of tetralogy of Fallot with absent pulmonary valve. Isolated dysplasia of the pulmonary valve can rarely present predominantly as regurgitation. Variants of pulmonary valve dysplasia/absent pulmonary valve can be seen in the setting of intact ventricular septum, often in conjunction with tricuspid valve anomalies such as membranous atresia or Ebstein malformation.

Common Associated Lesions/Findings

Common lesions associated with pulmonary regurgitation are summarized in Table 13.4.

Interventional and Postinterventional Imaging

Pulmonary regurgitation is commonly seen following valvotomy for pulmonary valve stenosis. Alternatively, when the pulmonary valve annulus is hypoplastic, pulmonary valvotomy with a transannular RV outflow tract patch, e.g., in tetralogy of Fallot, is typically performed. In either case, it is typical to see moderate or greater degrees of pulmonary regurgitation. In the setting of significant pulmonary regurgitation, it is important to follow RV size and function by serial echocardiographic study. Long-standing, significant pulmonary regurgitation can be associated with significant right ventricular dilation and dysfunction.

Intervention for pulmonary regurgitation itself most frequently consists of surgical valve replacement with a bioprosthesis, such as a pulmonary homograft or porcine xenograft. Although not widely available, particularly in the United States, stent-mounted valves can now be placed in the pulmonary position. Echocardiographic evaluation in these settings should be focused on ongoing valve competence and/or the development of graft valve stenosis, which can often be the result of calcification. Surgical implantation of valved conduits can also be associated with distal main or branch pulmonary artery distortion/obstruction; imaging of the distal and branch pulmonary arteries should be performed in this setting.

PULMONARY ATRESIA WITH INTACT VENTRICULAR SEPTUM

Background

Clinical Presentation

Pulmonary atresia with intact ventricular septum (PA/IVS) is a rare form of complex congenital heart disease, occurring in approximately 0.0045–0.085 per 1000 live births. It is characterized by complete obstruction to right ventricular outflow, an intact ventricular septum, and variable degrees of hypoplasia of the tricuspid valve and right ventricle.

Typically, these infants are cyanotic at birth. The clinical examination usually reveals a single second heart sound, and there is frequently a systolic murmur (from tricuspid regurgitation). The electrocardiogram characteristically shows left ventricular dominance with diminished right ventricular forces and left ventricular hypertrophy. On chest x-ray, the lung fields are oligemic with a normal heart size (unless there is severe tricuspid regurgitation resulting in right atrial enlargement).

In the current era, a number of these infants are detected prenatally. Investigators have examined a variety of echo-derived measures in the fetus which help to predict outcome. These have included such measures as fetal tricuspid valve annulus z-score, the RV/LV length ratio, the tricuspid valve/mitral valve ratio, tricuspid valve inflow duration, and the presence of RV sinusoids. Fetal detection allows for prenatal counseling and ensures the institution of prostaglandin infusion for stabilization at the time of delivery.

Anatomy and Physiology

The hallmark of PA/IVS is an atretic pulmonary valve; however, in reality, it reflects a wide spectrum of morphological abnormalities which variably affect the tricuspid valve, the RV, the right ventricular outflow tract, the branch pulmonary arteries and the coronary arteries.

The United Kingdom and Ireland Collaborative Study of PA/IVS (Daubeney, 2002) is a population-based study describing 183 infants born with PA/IVS, and provides helpful data regarding the prevalence of the various abnormalities. Eight percent had significant RV dilation, and this was associated with moderate to severe tricuspid regurgitation in all cases, with a very thin-walled RV in half of them; in the remainder, the RV was normal-sized or hypoplastic, associated with significant myocardial hypertrophy. In most cases the RV was tripartite (consisting of the inlet, trabecular, and outlet portions), however, bipartite ventricles and unipartite ventricles did occur, with a frequency of 34% and 8%, respectively. The median tricuspid valve z-score was −5.2. Ebstein malformation coexisted in 18/183 cases. Pulmonary atresia was valvar/membranous in 75% and muscular/infundibular in 25%. The branch pulmonary arteries were typically confluent and normal-sized.

Coronary artery abnormalities have been well described in PA/IVS, and they significantly impact outcomes. Ventriculocoronary arterial connections, stenotic or interrupted coronaries, and abnormalities of coronary origin or distribution have been described. Myocardial sinusoids (distinguished from ventriculocoronary fistulas since they traverse a capillary bed) can also occur. Daubeney (2002) found normal coronary arteries in 54%, and fistulous connections between the RV and the coronaries in 46%. Ten cases (8%) were felt to have truly RV-dependent coronary circulation, with associated coronary stenosis, interruption, or severe ectasia.

Complications

The critical decision point for neonates with PA/IVS is deciding who is suitable for a biventricular versus a univentricular repair. In general, a biventricular repair is favored when the RV is tripartite, the tricuspid valve z-score is adequate (>−2.4) and the pulmonary valve obstruction is membranous, since this allows for membrane perforation and dilation in the cardiac catheterization laboratory. However, this RV decompression does place the neonate at risk for myocardial ischemia in the setting of RV-dependent coronary artery circulation. However, even in neonates where a univentricular approach is favored, they can also develop coronary insufficiency due to the presence of these underlying coronary abnormalities. The role and timing of catheterization remains somewhat contentious; however, most clinicians support the practice of obtaining an early catheterization to detect the presence of coronary stenoses or interruptions (which cannot be clearly delineated by echocardiography alone).

Principles of Echocardiographic Anatomy and Imaging

Two-Dimensional Echocardiographic Anatomy and Hemodynamics

The first objective when imaging a new patient with PA/IVS is to confirm anatomical pulmonary atresia, and establish whether it is membranous (suitable for perforation and balloon dilation) or muscular (unsuitable for catheter intervention). Imaging of the RV outflow tract in the parasternal long-axis, parasternal short-axis, and subcostal views is most helpful. Careful anterior sweeps in the subcostal coronal view usually clearly demonstrate the morphological type of atresia. The RV cavity usually narrows and ends before seeing the pulmonary trunk in muscular atresia (Fig. 13.23), whereas the membranous type can often mimic normal valve function (Fig. 13.24). It is imperative to use color and pulsed-wave Doppler to differentiate whether the valve/membrane is perforate or not.

The second main objective is to evaluate whether the anatomy and physiology is consistent with biventricular or univentricular repair. This involves evaluating the size of the right ventricle and whether it is tripartite, bipartite, or unipartite (Fig. 13.25, Video 13.11). RV volume calculations are typically inaccurate; however, unipartite morphology has been shown to be an independent risk factor for death in these patients (Daubeney, 2005). The subcostal coronal and sagittal views are helpful for evaluating whether the RV has an inlet, outlet, and/or trabecular portion. Careful evaluation of the tricuspid valve with 2D and color Doppler should be done to evaluate its morphology and function. In addition, a careful measurement of the tricuspid valve annulus should be done in the apical four-chamber view, and the z-score calculated. The relative dimensions of both tricuspid and mitral valve annuli should be compared, since Minich et al. showed that a tricuspid/mitral ratio >0.5 was a good predictor of biventricular repair (Minich, 2000).

Figure 13.23. Parasternal short-axis image in a patient with pulmonary atresia with intact ventricular septum. There is an atretic pulmonary valve (open arrow), as well as muscular atresia of the right ventricular outflow tract (asterisk) between the tricuspid valve (white arrow) and pulmonary valve. Ao, aorta; LA, left atrium; MPA, main pulmonary artery; RA, right atrium.

Figure 13.24. Membranous pulmonary atresia. The right ventricular outflow tract (RVOT) is patent, but the pulmonary valve (open arrow) is imperforate. Ao, aorta; MPA, main pulmonary artery.

Figure 13.25. Pulmonary atresia with intact ventricular septum. Apical 4-chamber view demonstrating severe hypoplasia of the right ventricular cavity (asterisk). The tricuspid valve annulus (white arrows) is also hypoplastic. LA, left atrium; LV, left ventricle; RA, right atrium.

The third main objective is to assess the coronary arteries and detect the presence of significant ventriculocoronary arterial connections (Video 13.12), which result in RV-dependent coronary circulation. These fistulous connections are usually not seen directly; however, the presence of dilated, tortuous proximal coronary arteries suggests their presence (Figs. 13.26 and 13.27, Videos 13.13 and 13.14). Coronary sinusoids (which traverse a capillary bed) can be seen using low-scale color Doppler (Fig. 13.28). However, their presence does not necessarily confirm or negate the presence of RV-dependent coronary circulation. The determination of RV-dependence typically requires angiography to assess for potential RV steal, for stenoses, or for potential isolation of distal coronary artery flow with RV decompression. Satou et al. showed that a TV z-score ≤−2.5 predicted the presence of coronary artery fistulae with a high degree of sensitivity. Imaging in the standard coronary artery planes (especially short-axis) helps to delineate these abnormalities.

The final objectives are to evaluate the confluence and size of the branch pulmonary arteries (usually confluent and normal-sized) from right parasternal images; delineate the size and course of the PDA (usually from suprasternal notch long axis and right parasternal axis); measure the ASD size and gradient from subcostal views; and obtain an RV pressure estimate from TR jet velocity in the apical four-chamber view.

Figure 13.26. Coronary artery abnormalities in pulmonary atresia with intact ventricular septum. Parasternal short-axis demonstrating dilation of the proximal right coronary artery (open arrow) on 2D imaging (left). Color flow Doppler imaging (right) demonstrates retrograde filling of the right coronary artery (open arrow), with flow coursing toward the aortic root (Ao).

Figure 13.27. Parasternal short-axis image of the aortic root (Ao) and dilated left coronary artery (open arrow) in an infant with pulmonary atresia, intact ventricular septum, and right ventricular-dependent coronary artery circulation. Color flow Doppler imaging reveals that the dilated left coronary artery fills retrograde.

Figure 13.28. Apical 4-chamber view of the posterior right ventricle and left ventricle (LV) at the level of the coronary sinus (open arrow). Multiple coronary sinusoidal channels within the right ventricular myocardium (white arrows) are demonstrated by color flow Doppler imaging. RA, right atrium.

Common Associated Lesions/Findings

Major associated findings are outlined in Table 13.5. In the series reported by Daubeney et al., the most common associated findings in PA/IVS were Ebstein malformation of the tricuspid valve (9.8%) (Fig. 13.29); hypoplastic pulmonary arteries (8.7%); LV and LV outflow tract abnormalities, including LV non-compaction, bicuspid aortic valve and dysplastic mitral valve (8.2%), tiny VSD (6.5%), and left superior vena cava (2.7%).

Interventional and Postinterventional Imaging

If a pulmonary valvotomy alone is performed, then the following postinterventional aspects are important to delineate when imaging: tricuspid regurgitant velocity for RV pressure estimate; transpulmonary flow velocity for RV obstruction; RV size and volume; transtricuspid valve velocity, annulus, and z-score; and direction of atrial level shunting. If a shunt is placed, the following aspects are important to assess post-intervention: shunt flow; LV and left atrial sizes; tricuspid regurgitant velocity for RV pressure; and pulmonary artery size in preparation for bidirectional Glenn operation. As an alternative to aortopulmonary shunting, some centers may stent the ductus arteriosus (Fig. 13.30). Occasionally the decision is made to have a “one-and-a-half” ventricle repair. This is when a bidirectional Glenn operation is performed together with either closed or open relief of RV outflow tract obstruction. Despite numerous advances in diagnosis and management, patients with PA/IVS continue to have relatively high rates of morbidity and mortality even into adulthood (John et al. 2012).

Figure 13.29. Apical 4-chamber view in an infant with pulmonary atresia with intact ventricular septum. A: The tricuspid valve septal leaflet tissue is absent (white arrows), suggesting a severe variant of Ebstein anomaly. The right ventricular (RV) cavity is also hypoplastic. B: Color flow Doppler imaging demonstrates severe, laminar tricuspid regurgitation (open arrow). LA, left atrium; LV, left ventricle; RA, right atrium.

Figure 13.30. Parasternal short-axis image in an infant with pulmonary atresia with intact ventricular septum. A stent (open arrow) has been placed across the ductus arteriosus to create a stable source of pulmonary blood flow. Patency of the ductus and stent can be confirmed by color flow Doppler (open arrow, right). MPA, main pulmonary artery.

POTENTIAL ROLES FOR ALTERNATIVE IMAGING MODALITIES IN RIGHT VENTRICULAR OUTFLOW TRACT ABNORMALITIES

The primary reasons to consider alternative imaging modalities in the assessment of right ventricular outflow tract abnormalities are related to limitations to either echocardiographic image quality or limited ability to obtain desired physiologic information echocardiographically. In right ventricular outflow tract abnormalities, the most frequent indications for alternative imaging are assessment of right ventricular size and function, quantitation of right ventricular pressure, estimation of pulmonary regurgitant fraction, and imaging of the branch pulmonary arteries.

Right Ventricular Size and Function

Quantitative estimation of right ventricular size and function by echocardiography has been a long-standing challenge. The irregular shape of the right ventricle, particularly in the setting of pathologic anatomy, limits reliability of estimates of RV volume based on geometric models. In addition, imaging of the right ventricle in older patients, or in patients following multiple surgical procedures, is often limited by marginal acoustic windows. For these reasons, alternative imaging modalities for assessment of right ventricular size and function should be considered. In the current era, magnetic resonance imaging is gaining increasing application as a means of quantifying RV size and function, primarily by estimation of right ventricular volumes and ejection fraction. Particularly in older patients, MRI imaging can be performed without sedation, and can produce excellent image quality with simple breath holding and gating to the heart rate. Alternatively, catheterization and angiography can be performed to evaluate RV size and function, particularly when physiologic information is also being obtained. Catheterization has the obvious limitations of being relatively invasive, as well as exposing the patient to fluoroscopy and intravenous contrast. Estimates of RV size and volume on angiography are again limited by the geometric models used to estimate RV volume on biplane images.

Physiologic Measures

Determination of right ventricular pressure in the setting of right ventricular outflow tract obstruction is important in determining both lesion severity and indication for intervention. Often, the RV pressure cannot be estimated echocardiographically due to an inadequate tricuspid regurgitant jet Doppler profile. Other indirect measures of RV pressure overload, such as hypertrophy or interventricular septal position, are inadequately sensitive to discriminate significant right ventricular hypertension. Hemodynamic assessment during catheterization is the most reliable means of determining right ventricular pressure, i.e., by direct catheter measurement. Catheterization has the additional advantage of facilitating RV angiography as well as angiography of the branch pulmonary arteries should there be questions regarding RV size, function, or branch pulmonary artery anatomy.

Estimation of pulmonary regurgitant volume by 2D and Doppler methods is problematic. Regurgitant flows are quite readily obtained by phase contrast magnetic resonance imaging. This technique allows estimation of both forward and regurgitant pulmonary artery flow. Pulmonary regurgitant fraction can then be derived. Flow into the individual branch pulmonary arteries can also be determined using this technique.

Imaging of Pulmonary Artery Anatomy

There are several alternative modalities with which to image the main and branch pulmonary arteries. In addition to angiography during catheterization, both magnetic resonance imaging and computed tomography can be used to evaluate the branch pulmonary arteries. Both techniques allow for tomographic imaging of the pulmonary arteries in a myriad of imaging planes. In addition, processing of both MR and CT images will allow for 3D image reconstruction, which can supplement anatomic characterization of pulmonary artery anatomy.

Acknowledgment

The authors would like to thank Stacy Meredith, RDCS, for her assistance in preparing images and figures for use in this chapter.

SUGGESTED READING

Valvar Pulmonary Stenosis

Burch M, Sharland M, Shinebourne E, Smith G, Patton M, McKenna W. Cardiologic abnormalities in Noonan syndrome: phenotypic diagnosis and echocardiographic assessment of 118 patients. J Am Coll Cardiol. 1993;22:1189–1192.

Lima OC, Sahn DJ, Valdes-Cruz LM, Goldberg SJ, Barron JV, Allen HD, Grenadier E. Noninvasive prediction of transvalvular pressure gradient in patients with pulmonary stenosis by quantitative two-dimensional echocardiographic Doppler studies. Circulation. 1983;67:866–871.

Trowitzsch E, Colan SD, Sanders SP. Two-dimensional echocardiographic evaluation of right ventricular size and function in newborns with severe right ventricular outflow tract obstruction. J Am Coll Cardiol. 1985;6:388–393.

Weyman AE, Hurwitz RA, Girod DA, Dillon JC, Feigenbaum H, Green D. Cross-sectional echocardiographic visualization of the stenotic pulmonary valve. Circulation. 1977;56:769–774.

Subvalvar Pulmonary Stenosis

Alva C, Ho SY, Lincoln CR, Rigby ML, Wright A, Anderson RH. The nature of the obstructive muscular bundles in double-chambered right ventricle. J Thorac Cardiovasc Surg. 1999;117: 1180–1189.

Hubail Z, Ramaciotti C. Spatial relationship between the ventricular septal defect and the anomalous muscle bundle in a double-chambered right ventricle. Congenit Heart Dis. 2007;2:421–423.

Wong PC, Sanders SP, Jonas RA, Colan SD, Parness IA, Geva T, Van Praagh R, Spevak PJ. Pulmonary valve-moderator band distance and association with development of double-chambered right ventricle. Am J Cardiol. 1991;68:1681–1686.

Supravalvar Pulmonary Stenosis

Frank DU, Minich LL, Shaddy RE, Tani LY. Is Doppler an accurate predictor of catheterization gradients for postoperative branch pulmonary stenosis? J Am Soc Echocardiogr. 2002;15:1140–1144.

Gay BB Jr., French RH, Shuford WH, Rogers JV Jr. The roentgenologic features of single and multiple coarctations of the pulmonary artery and branches. Am J Roentgenol Radium Ther Nucl Med. 1963;90:599–613.

Hiraishi S, Misawa H, Hirota H, Agata Y, Horiguchi Y, Fujino N, Yi LH, Yashiro K, Nakae S, Kawada M. Noninvasive quantitative evaluation of the morphology of the major pulmonary artery branches in cyanotic congenital heart disease. Angiocardiographic and echocardiographic correlative study. Circulation. 1994;89: 1306–1316.

Kim YM, Yoo SJ, Choi JY, Kim SH, Bae EJ, Lee YT. Natural course of supravalvar aortic stenosis and peripheral pulmonary arterial stenosis in Williams’ syndrome. Cardiol Young. 1999;9:37–41.

Rein AJ, Preminger TJ, Perry SB, Lock JE, Sanders SP. Generalized arteriopathy in Williams’ syndrome: an intravascular ultrasound study. J Am Coll Cardiol. 1993;21:1727–1730.

Pulmonary Regurgitation

Lei MH, Chen JJ, Ko YL, Cheng JJ, Kuan P, Lien WP. Reappraisal of quantitative evaluation of pulmonary regurgitation and estimation of pulmonary artery pressure by continuous-wave Doppler echocardiography. Cardiology. 1995;86:249–256.

Li W, Davlouros PA, Kilner PJ, Pennell DJ, Gibson D, Henein MY, Gatzoulis MA. Doppler echocardiographic assessment of pulmonary regurgitation in adults with repaired tetralogy of Fallot: comparison with cardiovascular magnetic resonance imaging. Am Heart J.2004;147:165–172.

Masuyama T, Kodama K, Kitabatake A, Sato H, Nanto S, Inoue M. Continuous-wave Doppler echocardiographic detection of pulmonary regurgitation and its application to noninvasive estimation of pulmonary artery pressure. Circulation. 1986;74:484–492.

Puchalski MD, Askovich B, Sower CT, Williams RV, Minich LL, Tani LY. Pulmonary regurgitation: determining severity by echocardiography and magnetic resonance imaging. Congenit Heart Dis. 2008;3:168–175.

Pulmonary Atresia with Intact Ventricular Septum

Daubeney PEF, Delany DJ, Anderson RH, Sandor GGS, Slavik Z, Keeton BR, Webber SA. Pulmonary atresia with intact ventricular septum: range of morphology in a population-based study. J Am Coll Cardiol. 2002;39:1670–1679.

Daubeney PEF, Wang D, Delany DJ, Keeton BR, Anderson RH, Slavik Z, Flather M, Webber SA. Pulmonary atresia with intact ventricular septum: predictors of early and medium-term outcome in a population-based study. J Thorac Cardiovasc Surg. 2005;130:1071–1078.

John AS, Warnes CA. Clinical outcomes of adult survivors of pulmonary atresia with intact ventricular septum. Int J Cardiol. 2012 Nov 1;161(1):13–17.

Minich LL, Tani LY, Ritter S, Williams RV, Shaddy RE, Hawkins JA. Usefulness of the preoperative tricuspid/mitral valve ratio for predicting outcome in pulmonary atresia with intact ventricular septum. Am J Cardiol. 2000;85:1325–1328.

Roman KS, Fouron JC, Nii M, Smallhorn JF, Chaturvedi R, Jaeggi ET. Determinants of outcome in fetal pulmonary valve stenosis or atresia with intact ventricular septum. Am J Cardiol. 2007;99:699–703.

Salvin JW, McElhinney DB, Colan SD, Gauvreau K, Del Nido P, Jenkins KJ, Lock JE, Tworetzky W. Fetal tricuspid valve size and growth as predictors of outcome in pulmonary atresia with intact ventricular septum. Pediatrics. 2006;118:e415–e420.

Satou GM, Perry SB, Gauvreau K, Geva T. Echocardiographic predictors of coronary artery pathology in pulmonary atresia with intact ventricular septum. Am J Cardio l. 2000;85:1319–1324.

Zuberbuhler JR, Anderson RH. Morphologic variations in pulmonary atresia with intact ventricular septum. Br Heart J. 1979;41:281–288.

Alternative Imaging Modalities in Right Ventricular Outflow Tract Obstruction

Greenberg SB, Crisci KL, Koenig P, Robinson B, Anisman P, Russo P. Magnetic resonance imaging compared with echocardiography in the evaluation of pulmonary artery abnormalities in children with tetralogy of Fallot following palliative and corrective surgery. Pediatr Radiol. 1997;27:932–935.

Questions

1.In pulmonary atresia with intact ventricular septum, the branch pulmonary arteries are typically:

A.Dilated and tortuous

B.Discontinuous

C.Severely hypoplastic

D.Continuous and normal-sized

E.Absent

2.In pulmonary atresia with intact ventricular septum, the tricuspid valve:

A.most often has normal morphology.

B.is usually Ebsteinoid.

C.most often has abnormal size and morphology.

D.typically has a dilated annulus in the setting of RV hypoplasia.

E.is usually never regurgitant.

3.In pulmonary atresia with intact ventricular septum, the most common indirect echocardiographic indication of the presence of right ventricle to coronary artery direct fistulous connections are:

A.an atretic proximal right coronary artery.

B.a dilated proximal right coronary artery.

C.a normal-sized tripartite right ventricle.

D.a low-velocity, color-flow Doppler signal at the apex.

E.an absent left-anterior descending coronary artery.

4.What is the most helpful echocardiogram-derived predictor of the potential for successful biventricular repair versus univentricular repair in pulmonary atresia with intact ventricular septum?

A.The tricuspid annulus Z-score

B.The mitral annulus Z-score

C.The presence of discontinuous branch pulmonary arteries

D.The presence of a reverse-oriented patent ductus arteriosus

E.The presence of right ventricular dysfunction

5.In pulmonary atresia with intact ventricular septum, the presence of RV-dependent coronary circulation is usually definitively diagnosed when:

A.low-velocity color Doppler flow signals are seen at the RV apex.

B.angiography shows coronary artery stenosis, potential for RV steal, and potential isolation of distal coronary artery flow.

C.the tricuspid annulus Z-score is greater than -2.

D.the right ventricle is noted to be dilated.

E.there is right ventricular dysfunction.

6.In a double-chambered right ventricle, all of the following are EXPECTED findings, EXCEPT:

A.dynamic outflow tract gradient on Doppler analysis.

B.prominent muscle bundles traversing the right ventricle between sinus and infundibular portions.

C.a ventricular septal defect.

D.fixed obstruction as evidenced by Doppler evaluation of right ventricular outflow tract.

E.elevated right ventricular pressure.

7.What is the LEAST likely diagnosis in the figure below?

A.Idiopathic pulmonary hypertension

B.Isolated large ventricular septal defect

C.Critical/severe pulmonary valve stenosis

D.Congenital diaphragmatic hernia with severe pulmonary hypertension

E.Persistent, severe pulmonary hypertension of the newborn

8.Diffuse hypoplasia of the branch pulmonary arteries is commonly seen in all of the following conditions, EXCEPT:

A.William’s syndrome

B.Allagile syndrome

C.Tetralogy of Fallot with absent pulmonary valve

D.Pulmonary atresia with ventricular septal defect

E.Congenital diaphragmatic hernia

9.In which of the following is cyanosis LEAST likely to be a presenting symptom?:

A.Pulmonary atresia with intact ventricular septum

B.Tetralogy of Fallot with diffuse branch pulmonary artery hypoplasia

C.Severe valvar pulmonic stenosis with atrial septal defect

D.Critical valvar pulmonic stenosis in the newborn

E.Moderate valvar pulmonic stenosis

10.All of the following are commonly associated with valvar pulmonary stenosis EXCEPT:

A.Post-stenotic dilation of the main pulmonary artery

B.Dysplastic pulmonary valve

C.Right ventricular dilation

D.Tricuspid regurgitation

E.Right-ventricular hypertrophy

Answers

1.Answer: D. Unlike pulmonary atresia with VSD, the branch pulmonary arteries in PA-IVS are usually a normal size and continuous.

2.Answer: C. Almost invariably, the tricuspid valve is abnormal in PA-IVS, demonstrating a continuum of abnormalities ranging from extreme stenosis to profound regurgitation.

3.Answer: B. When there are direct right ventricular-to-coronary artery fistulous connections, typically the proximal right coronary artery is dilated (and there may be reverse filling noted). Most often these connections occur in the setting of a severely hypoplastic right ventricle (unipartite or bipartite).

4.Answer: A. Most studies have shown that the tricuspid annulus Z-score is the most accurate predictor of success for a biventricular repair versus single-ventricle palliation in PA-IVS.

5.Answer: B. Angiography is really only the definitive way to diagnose RV-dependent coronary artery circulation in PA-IVS. A tricuspid valve Z-score of less than -2.5 is suggestive of it, but not definitive.

6.Answer: D. The pattern of obstruction in double-chambered RV is typically dynamic. Ventricular septal defects are seen very commonly in association with the lesion. The RV outflow tract obstruction should also result in elevated right-ventricular pressure.

7.Answer: B. This parasternal short-axis view demonstrates RV enlargement, with bowing of the ventricular septum into the left ventricle (LV) consistent with suprasystemic right ventricular pressure. In an isolated large VSD, it would not be expected to manifest suprasystemic right-ventricular pressure, as pressure would equalize across the large ventricular septal defect.

8.Answer: C. In Tetralogy of Fallot with absent pulmonary valve, the branch pulmonary arteries are variably, but often severely, dilated. Pulmonary artery hypoplasia is often seen in Williams and Allagile syndromes. Pulmonary atresia with VSD is often associated with severely hypoplastic central pulmonary arteries. Congenital diaphragmatic hernia is usually associated, especially when severe, with unilateral lung hypoplasia and a small pulmonary artery on the ipsilateral side to the hypoplastic lung.

9.Answer: E. The clinical presentation of moderate pulmonary valve stenosis is typically mild, with the most common clinical finding consisting of a systolic murmur in an asymptomatic patient. Pulmonary atresia, Tetralogy of Fallot with diffuse pulmonary artery hypoplasia, severe valvar pulmonic stenosis, and critical pulmonary stenosis in the newborn (by definition) typically present with significant right-to-left shunting producing cyanosis and hypoxemia.

10.Answer: C. Right-ventricular dilation is not typically associated with valvar pulmonary stenosis, unless severe right-ventricular dysfunction has resulted. Post-stenotic dilation of the main pulmonary artery, dysplastic pulmonary valve, and RV hypertrophy are relatively common in more severe pulmonic stenosis. Tricuspid regurgitation can also occur as a consequence of RV pressure overload.