Definition and Morphology
Pulmonary valvular stenosis is usually an isolated congenital anomaly and occurs in 7% to 12% of patients with congenital heart disease. It can sometimes be associated with other congenital heart defects such as atrial septal defect or peripheral pulmonary artery stenosis. It is the most common form of right-sided obstruction and results from the fusion of the valve leaflets. The pulmonary valve appears conical or dome-shaped with a narrow opening at its apex; the leaflets are fused, and in adults calcification may be present. The number of leaflets may vary from one to four. The valve is sometimes called dysplastic when the leaflets are very thick, but there is no fusion of the cusps, generally a component of Noonan syndrome. Pulmonary valve stenosis is rarely due to rheumatic inflammation, carcinoid involvement, compressive tumors, or infective endocarditis. Pulmonary stenosis may be associated with various genetic or chromosomal disorders, the most common being the RASopathies (Noonan, Leopard, and Costello syndromes), but also Williams and Alagille syndromes. Mutations in GATA4 have been associated with pulmonary valve stenosis. The functional consequence of pulmonary stenosis is obstruction of the ejection of blood from the right ventricle leading to an increase in right ventricular pressure. Right ventricular output is maintained by the development of right ventricular hypertrophy, which may sustain a large pressure gradient across the pulmonary valve for many years without symptoms, the development of right ventricular dilation, or a reduction in cardiac output.
Early Presentation and Management
Severe pulmonary stenosis in neonates is frequently associated with a hypoplastic right ventricular cavity and may be fatal without rapid intervention. The main clinical symptom is cyanosis due to right-to-left shunting through a patent foramen ovale caused by increased right-sided pressures. The diagnosis of severe pulmonary valvular stenosis can be made by echocardiography in fetal life or in the neonatal unit. Balloon dilation of the pulmonary valve is the procedure of choice to relieve the obstruction. Pulmonary valvotomy or systemic-to-pulmonary arterial shunt may be necessary if there is underdevelopment of the right ventricle, the pulmonary valve annulus, or the pulmonary artery branches.
Clinical presentation in childhood depends on the severity of the obstruction and the degree of hypoplasia of the right ventricle. Most children are asymptomatic, and pulmonary stenosis is often discovered during routine examination. When symptoms are present, children experience exertional symptoms: dyspnea, fatigue, mild cyanosis, chest pain, or syncope. Mild pulmonary stenosis has a favorable course. Relief of the obstruction is indicated for children with moderate to severe stenosis, even in the absence of symptoms.
Late Outcome
Survival and Functional Status
Pulmonary valve stenosis is generally better tolerated than aortic stenosis and is associated with a more benign course. Today, survival into adolescence and adulthood is the rule. Hayes et al., in the Second Natural History Study of Congenital Heart Defects, reported a probability of survival similar to that of the general population among 592 patients with different degrees of obstruction who were managed either medically or surgically and observed for more than 15 years. In that series, adults with a transpulmonary valve gradient of less than 25 mm Hg were asymptomatic and had no significant progression of the obstruction with time. For those with a peak systolic gradient between 25 and 49 mm Hg at initial heart catheterization, there was approximately a 20% chance of eventually needing an intervention, whereas most patients with a peak systolic gradient greater than 50 mm Hg ultimately required an intervention. Children with severe pulmonary stenosis will usually have had a valvotomy (surgical or balloon). Kopecky and colleagues reported a normal life expectancy over a 20- to 30-year period for 191 hospital survivors who underwent repair at age 21 years or younger between 1956 and 1967. Most patients, operated on or not, are thus asymptomatic and in New York Heart Association functional class I to II when they reach adulthood.
Late Complications
Obstruction to the ejection of blood from the right ventricle leads to an increase in right-sided pressures and to secondary right ventricular hypertrophy. The right ventricular hypertrophy may be particularly noticeable in the infundibular region, producing dynamic narrowing of the outflow tract and contributing to an increase in the degree of obstruction. With time, such patients may present with decreased exercise tolerance, dyspnea, and signs of right ventricular failure. Right ventricular failure is the most common mode of death in unoperated patients with moderate to severe obstruction. Supraventricular arrhythmias (atrial fibrillation or flutter) may precipitate symptoms of right ventricular failure. Bacterial endocarditis is a rare complication. Complications after pulmonary valvotomy (surgical or balloon) include pulmonary regurgitation with right ventricular dilation, residual valvular or infundibular obstruction, supraventricular or ventricular arrhythmias, and sudden death.
Outpatient Assessment
Unrepaired Adult
Pulmonary stenosis may be found during a routine examination because adults with mild to moderate obstruction are asymptomatic. Some patients are referred because of enlarged pulmonary arteries detected on chest radiography or because a murmur was heard. Moderate to severe obstruction can be associated with:
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Right ventricular hypertrophy
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Symptoms such as decreased exercise tolerance, dyspnea, fatigue, syncope, chest pain, and palpitations
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Mild cyanosis and clubbing in patients with severe obstruction, due to right-to-left shunting through a patent foramen ovale or an atrial septal defect
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An increased risk of paradoxic emboli
Physical Examination
Physical examination includes assessment of:
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A prominent jugular wave due to a forceful right atrial contraction, which is essential to fill the hypertrophied, noncompliant right ventricle
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A right ventricular lift
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A systolic thrill along the left sternal border
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A soft and delayed pulmonary component of the second heart sound due to prolonged ejection time and further delayed splitting with increasing obstruction
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A fourth heart sound that may be present
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A systolic ejection click at the upper left sternal edge (produced by sudden opening of the valve) that is louder during expiration (may not be present in severe obstruction, when the cusps remain immobile)
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A harsh, crescendo-decrescendo systolic ejection murmur heard best at the upper left sternal border, which radiates to the back and may be augmented by inspiration. With increasing obstruction, the murmur lengthens and peaks later in systole
Physical signs suggestive of severe obstruction are summarized in Box 45.1 .
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Cyanosis and clubbing
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Widely split S 2
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Reduced or absent P 2
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Short S 1 -ejection click interval
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Long systolic ejection murmur
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Peak of murmur late in systole
Electrocardiography
There may be right-axis deviation, right ventricular hypertrophy, and right atrial enlargement with moderate to severe pulmonary stenosis. The electrocardiogram is usually normal in the presence of mild obstruction.
Chest Radiography
The most striking feature is a prominent main pulmonary artery due to dilation of the pulmonary trunk and left pulmonary artery ( Fig. 45.1 ). The physics and the direction of the jet dispersion may be the reason for the asymmetric dilation of the left and right pulmonary arteries, although such dilation may occur in patients with mild pulmonary stenosis.
Heart size and pulmonary vascular markings are normal in patients with mild to moderate obstruction. In patients with severe stenosis, right atrial and ventricular enlargement and decreased pulmonary vascular markings may be seen. Pulmonary valve calcification may occasionally be present.
Echocardiography
Echocardiography is the diagnostic method of choice. It allows for visualization of the valve anatomy and evaluation of the hemodynamic repercussions of the obstruction ( Fig. 45.2 ). The valve is more difficult to visualize in adults than in children but may appear thickened with a dome-shaped deformity in systole. Nishimura et al. studied the morphology of the pulmonary valve by echocardiography in 325 patients with various degrees of stenosis and detected doming in 31%, leaflet thickening in 24%, and calcification in 1% to 2%. When possible, the pulmonary valve annulus should be measured as it may be needed to guide balloon dilatation.
