Pulmonary Stenosis

Pulmonary stenosis is most often congenital and affects predominantly children; stenosis may be valvular or just below the valve in the outflow tract (infundibular); commonly it is a component of tetralogy of Fallot. Supravalvular stenosis may also occur, sometimes in combination with valvar stenosis, as a tethered valve/supravalve complex, or as isolated supravalvar narrowing (as in Williams or Alagille syndromes).

Less common causes are:

• Noonan syndrome (a genetic syndrome involving the Ras/mitogen-activated protein kinase pathway)

• Carcinoid syndrome (in adults)

Many children with pulmonary stenosis remain asymptomatic for years and do not develop overt symptoms until adulthood, although abnormalities can sometimes be detected on exercise testing before symptoms appear. Even in adulthood, many patients remain asymptomatic. When symptoms of pulmonary stenosis develop, they resemble those of aortic stenosis (exercise intolerance, syncope, angina, dyspnea).

Visible and palpable signs reflect the effects of right ventricular (RV) hypertrophy and include a prominent jugular venous a wave (due to forceful atrial contraction against a hypertrophied RV), an RV precordial lift or heave, and a left parasternal systolic thrill at the second intercostal space.

Auscultation

• Widened second heart sound (S2) and delayed pulmonic component of S2 (P2)

• Harsh crescendo-decrescendo ejection murmur

On auscultation, the first heart sound (S1) is normal and the splitting S2 is widened (but not fixed) because prolonged pulmonary ejection causes a delay in P2. As severity of PS worsens, P2 becomes softer in volume. A click in congenital PS is thought to result from abnormal ventricular wall tension. The click occurs early in systole (very near S1) and may be louder in inspiration. A harsh crescendo-decrescendo ejection murmur is audible and is heard best at the left parasternal second (valvular stenosis) or fourth (infundibular stenosis) intercostal space with the diaphragm of the stethoscope when the patient leans forward. In RV failure and hypertrophy, the third and fourth heart sounds (S3 and S4) are rarely audible at the left parasternal fourth intercostal space.

Unlike the aortic stenosis murmur, a pulmonary stenosis murmur does not radiate, and the crescendo component lengthens as stenosis progresses. The murmur grows louder immediately with Valsalva release and with inspiration; the patient may need to be standing for this effect to be heard.

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Pulmonary Stenosis Murmur

• Echocardiography

Diagnosis of pulmonary stenosis is confirmed by Doppler echocardiography, which can characterize the severity as (1):

• Mild: Peak gradient < 36 mm Hg or peak velocity < 3 m/second

• Moderate: Peak gradient 36 to 64 mm Hg or peak velocity 3 to 4 m/second

• Severe: Peak gradient > 64 mm Hg or peak velocity > 4 m/second

ECG may be normal or show RV hypertrophy or right bundle branch block.

Right heart catheterization is indicated when 2 levels of obstruction are suspected (valvular and infundibular), when direct measurement of right ventricular or other pressures is needed, when clinical and echocardiographic findings differ, or before intervention is performed.

Cardiac MRI may be useful if there is a need for quantification of right ventricle size or function, or the degree of concomitant pulmonary insufficiency.

Phonocardiographic Characteristics of Heart Murmurs

• Balloon valvuloplasty

• Sometimes surgical valvuloplasty or valve replacement

Prognosis of pulmonary stenosis without treatment is generally good and improves with appropriate intervention. Mild pulmonary valve stenosis in children may improve and even resolve spontaneously.

The first-line treatment of pulmonary stenosis is balloon valvuloplasty, which is indicated for patients with symptoms and moderate or severe valvular stenosis and for asymptomatic patients with severe stenosis.

Surgical valvuloplasty may be performed when there is another indication for cardiac surgery if the patient is otherwise not a candidate for a transcatheter approach. Pulmonary valve replacement may be necessary if there is significant pulmonary regurgitation (PR), pulmonary valve dysplasia, and/or hypoplasia of the pulmonary valve annulus (1). A valved or unvalved right ventricle to pulmonary artery conduit is used when the anatomy precludes use of the native valve.

When surgical valve replacement is necessary, bioprosthetic valves are preferred due to the high rates of thrombosis of right-sided mechanical heart valves; anticoagulation is temporarily required (see Anticoagulation for patients with a prosthetic cardiac valve or native valve disease).

Percutaneous (transcatheter) pulmonary valve replacement is offered at many congenital heart centers to reduce the number of open heart procedures, especially for those who have had or are expected to have multiple pulmonary valve interventions. The ability to use this technique depends upon patient size and the suitability of the pulmonary valve annulus or "landing zone."