pulmonic stenosis

Pulmonic stenosis (PS) results from obstruction to blood flow from the right ventricle (RV) to the pulmonary artery, most commonly due to valvular abnormalities (fused or dysplastic leaflets) but can also be subvalvular (infundibular) or supravalvular. It is predominantly a congenital lesion, accounting for ~8-10% of congenital heart defects, and is a key component of Tetralogy of Fallot (along with VSD, overriding aorta, and RV hypertrophy). It is strongly associated with Noonan syndrome and congenital rubella syndrome. Acquired causes include carcinoid heart disease (right-sided valvular lesions due to serotonin exposure) and rheumatic fever (though this more commonly affects left-sided valves).

Pathophysiology: The stenotic valve increases resistance to RV outflow, leading to increased RV systolic pressure and compensatory RV hypertrophy (concentric). Over time, this can progress to RV failure if severe and untreated. In neonates with critical PS, right-to-left shunting through a patent foramen ovale may cause cyanosis (duct-dependent pulmonary circulation).

Clinical presentation: Most patients with mild-to-moderate PS are asymptomatic and diagnosed incidentally. Severe PS can present with exertional dyspnea, fatigue, syncope, or right heart failure symptoms (peripheral edema, hepatomegaly, jugular venous distension). On exam: a systolic ejection murmur at the left upper sternal border (2nd left intercostal space) that increases with inspiration, often preceded by an ejection click that decreases with inspiration (unique among right-sided murmurs). A widely split S2 due to delayed pulmonic valve closure may be present. Severe cases show a right ventricular heave and prominent 'a' wave in JVP due to reduced RV compliance.

Diagnosis: Echocardiography is the gold standard, assessing valve morphology, pressure gradient across the valve, and RV size/function. ECG may show right axis deviation and RV hypertrophy. Chest X-ray can show post-stenotic dilation of the main pulmonary artery.

Management: Balloon valvuloplasty is first-line for isolated valvular PS with significant gradient (>50 mmHg peak or symptomatic). Surgical valvotomy or valve replacement is reserved for dysplastic valves or failed balloon intervention. Mild PS is typically monitored with serial echocardiograms.

Key associations for boards: Noonan syndrome (most common syndromic association), congenital rubella syndrome, Tetralogy of Fallot, carcinoid syndrome (right-sided valve lesions—pulmonic stenosis and tricuspid regurgitation), Williams syndrome (supravalvular pulmonic stenosis along with supravalvular aortic stenosis).