Crescendo-Decrescendo Murmur: Causes and Clinical Significance

Pathophysiological Mechanism

The murmur starts shortly after S1 when ventricular pressure rises sufficiently to open the semilunar valve, as noted by the American College of Cardiology 1
As ejection increases, the murmur intensifies (crescendo phase), and as ejection declines, it diminishes (decrescendo phase), according to the American College of Cardiology 1
This creates the characteristic "diamond-shaped" or "ejection" pattern on phonocardiography, as described in the Journal of the American College of Cardiology 2

Aortic stenosis is the most frequent pathological cause requiring valve replacement in adults, with incidence increasing with age, as reported by the American College of Cardiology 1
The murmur is loud, heard best at the right upper sternal border (2nd right intercostal space), and radiates to the carotids bilaterally, as noted by the American College of Cardiology 3 and the Journal of the American College of Cardiology 1, 2
Associated findings include soft or absent A2, reversed splitting of S2 in severe cases, and left ventricular hypertrophy on palpation, according to the American College of Cardiology 1, 2

Physical examination findings that suggest significant aortic stenosis include grade ≥3/6 intensity, as recommended by the American College of Cardiology 1
Dynamic auscultation patterns, such as systolic murmurs increasing in intensity after ventricular premature beats or during long cycle lengths in atrial fibrillation, can be diagnostic, as described in the Journal of the American College of Cardiology 3

Echocardiography is the gold standard for confirming the cause and should be performed in patients with suspected significant heart disease based on murmur characteristics, including those with grade ≥3/6 murmurs, as recommended by the American College of Cardiology 1 and the American Heart Association, as published in Circulation 4