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Pulmonic Stenosis

by Guy P. Armstrong, MD

Pulmonic stenosis (PS) is narrowing of the pulmonary outflow tract causing obstruction of blood flow from the right ventricle to the pulmonary artery during systole. Most cases are congenital; many remain asymptomatic until adulthood. Signs include a crescendo-decrescendo ejection murmur. Diagnosis is by echocardiography. Symptomatic patients and those with large gradients require balloon valvuloplasty.

Etiology

PS is most often congenital and affects predominantly children; stenosis may be valvular or just below the valve in the outflow tract (infundibular). It commonly is a component of tetralogy of Fallot (see Tetralogy of Fallot). Less common causes are Noonan syndrome (a familial syndrome similar to Turner syndrome but with no chromosomal defect) and carcinoid syndrome in adults.

Symptoms and Signs

Many children remain asymptomatic for years and do not present to a physician until adulthood. Even then many patients remain asymptomatic. When symptoms develop, they resemble those of aortic stenosis (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 2nd intercostal space.

On auscultation, the 1st heart sound (S 1 ) is normal and the normal splitting of the 2nd heart sound (S 2 ) is widened because of prolonged pulmonic ejection (P 2 , the pulmonic component of S 2 , is delayed). In RV failure and hypertrophy, the 3rd and 4th heart sounds (S 3 and S 4 ) are rarely audible at the left parasternal 4th intercostal space. A click in congenital PS is thought to result from abnormal ventricular wall tension. The click occurs early in systole (very near S 1 ) and is not affected by hemodynamic changes. A harsh crescendo-decrescendo ejection murmur is audible and is heard best at the left parasternal 2nd (valvular stenosis) or 4th (infundibular stenosis) intercostal space with the diaphragm of the stethoscope when the patient leans forward. Unlike the aortic stenosis murmur, a PS 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.

Diagnosis

  • Echocardiography

Diagnosis is confirmed by Doppler echocardiography, which can characterize the severity as

  • Mild: Peak gradient < 36 mm Hg

  • Moderate: Peak gradient 36 to 64 mm Hg

  • Severe: Peak gradient > 64 mm Hg

ECG may be normal or show RV hypertrophy or right bundle branch block. Right heart catheterization is indicated only when 2 levels of obstruction are suspected (valvular and infundibular), when clinical and echocardiographic findings differ, or before intervention is done.

Treatment

  • Sometimes balloon valvuloplasty

Prognosis without treatment is generally good and improves with appropriate intervention. Treatment is balloon valvuloplasty, indicated for symptomatic patients and asymptomatic patients with normal systolic function and a peak gradient > 40 to 50 mm Hg. Percutaneous valve replacement may be offered at highly selected congenital heart centers, especially for younger patients or those with multiple previous procedures, in order to reduce the number of open heart procedures. When surgical replacement is necessary, bioprosthetic valves are preferred due to the high rates of thrombosis of right-sided mechanical heart valves.

Key Points

  • Pulmonic stenosis is usually congenital, but symptoms (eg, syncope, angina, dyspnea) usually do not appear until adulthood.

  • Heart sounds include increased splitting of S 2 and a harsh crescendo-decrescendo ejection murmur heard best at the left parasternal 2nd or 4th intercostal space when the patient leans forward; the murmur grows louder immediately with Valsalva release and with inspiration.

  • Balloon valvuloplasty is done for symptomatic patients and asymptomatic patients with normal systolic function and a peak gradient > 40 to 50 mm Hg.

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