Valve leakiness or regurgitation due to incompetence, as in aortic insufficiency, produces a diastolic murmur beginning loudly at S2 and waning as ventricular relaxation and filling occur (a decrescendo sound).
Diastolic murmurs are also produced by constricted ventricular inflow valves, such as the mitral valve. Here the sound begins loudly with a snap at the start of rapid filling, then wanes somewhat thereafter and ends at S1.
Patent ductus arteriosus produces a murmur which is continuous during the cardiac cycle, but is somewhat louder around S2. Knowledge of murmurs is of enormous diagnostic value to the cardiologist and internist.
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