Pulmonary Stenosis Murmur
The characteristic murmur of pulmonary stenosis is a midsystolic (systolic ejection) crescendo-decrescendo murmur best heard at the left upper sternal border (pulmonic area) that increases with inspiration. 1
Murmur Characteristics
The pulmonary stenosis murmur has several defining features:
- Timing: Midsystolic ejection murmur that starts shortly after S1 and ends before S2
- Configuration: Crescendo-decrescendo (diamond-shaped) pattern 1
- Location: Best heard at the pulmonic area (left upper sternal border, second left intercostal space) and left sternal border 1
- Intensity: Varies with stenosis severity—the intensity depends on the velocity of blood flow across the narrowed valve 1
Key Distinguishing Features
Respiratory variation is a critical diagnostic clue: As a right-sided murmur, it increases with inspiration and decreases with expiration 2, 3, 4. This occurs because inspiration increases venous return to the right heart, augmenting flow across the stenotic pulmonary valve.
Associated Physical Findings
The murmur of pulmonary stenosis is often accompanied by an ejection sound (click) heard only in the pulmonic area and left sternal border during expiration 1, 3, 2. This ejection sound distinguishes pulmonic valve stenosis from aortic stenosis, where the ejection sound is heard during both inspiration and expiration 1, 3.
Dynamic Auscultation
The murmur becomes louder with exercise (both isotonic and isometric), as increased cardiac output augments flow across the stenotic valve 2, 3, 4. After a premature ventricular beat or during long cycle lengths in atrial fibrillation, the murmur increases in intensity, consistent with its origin at a stenotic semilunar valve 3, 4.
Clinical Context
The murmur intensity correlates with stenosis severity, though severe stenosis with very low cardiac output may paradoxically produce a softer murmur. In valvular pulmonary stenosis, the maximum intensity is localized in the pulmonary artery above the valve and transmits to both pulmonary arteries 5. This differs from infundibular stenosis, where maximum intensity is in the right ventricular outflow tract 5.
Important caveat: Echocardiography is often necessary to distinguish a prominent benign midsystolic murmur from true valvular stenosis, particularly when the murmur is grade 3 or higher 1, 2.