Pulmonary stenosis: causes, symptoms, diagnosis, treatment

Pulmonary stenosis is a narrowing of the right ventricular outflow tract that obstructs blood flow from the right ventricle to the pulmonary artery during systole.

Pulmonic stenosis is most often congenital and occurs primarily in children. Pulmonic stenosis may be valvular or directly subvalvular, located in the outflow tract (subvalvular). Rarer causes include Noonan syndrome (a familial syndrome similar to Turner syndrome but without the chromosomal defect) and carcinoid syndrome in adults.

Many children have no clinical symptoms for many years and do not seek medical attention until adulthood. When symptoms do occur, they resemble those of aortic stenosis (syncope, angina, dyspnea). Visible and palpable signs reflect right ventricular (RV) hypertrophy and include visible jugular venous distension (due to increased atrial contraction in response to RV hypertrophy), right ventricular precordial protrusion (cardiac hump), and a systolic thrill to the left of the sternum in the second intercostal space. On auscultation, the first heart sound (S1) is normal, the second heart sound (S2) is split and prolonged due to prolonged pulmonary ejection [the pulmonary component of S3 (P) is delayed]. With right ventricular failure and hypertrophy, the third and fourth heart sounds (S3 and S4) are sometimes heard in the fourth intercostal space to the left of the sternum. The click in congenital pulmonic stenosis is thought to result from abnormal ventricular wall tension. The click occurs in early systole (very close to S2) and is not affected by hemodynamic changes. A coarse crescendo-decrescendo ejection murmur is best heard to the left of the sternum in the second (valvular stenosis) or fourth (subvalvular pulmonic stenosis) intercostal space with a stethoscope and diaphragm when the patient leans forward. Unlike the murmur of aortic stenosis, the murmur of pulmonic stenosis does not radiate, and the crescendo component of the murmur lengthens as the stenosis progresses. The murmur becomes louder with the Valsalva maneuver and with inspiration; the patient must stand up for the phenomenon to be more audible.

Diagnosis is made by Doppler echocardiography, which may characterize the stenosis as minimal (peak gradient < 40 mmHg), moderate (41-79 mmHg), or severe (>80 mmHg). ECG findings always contribute to a partial assessment. They may be normal or reflect right ventricular hypertrophy or right bundle branch block. Right heart catheterization is indicated only when two levels of obstruction (valvular and subvalvular) are suspected, when clinical and echocardiographic findings differ, or before surgery.

The prognosis without treatment is generally good and improves with adequate medical intervention. Treatment involves balloon valvuloplasty, which is prescribed to patients with manifestations of pulmonary stenosis and to patients without clinical symptoms, with normal systolic function and a peak gradient > 40-50 mm Hg.

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