The classic example of a semilunar insufficiency murmur is aortic regurgitation. The murmur of aortic insufficiency is caused by turbulence of blood regurgitating through an incompetent aortic valve from the aorta to the left ventricle. This produces a high-pitched decrescendo murmur, which begins with the second heart sound (S2), lasts through some or all of diastole and declines in intensity as the aortic pressure falls. It tends to equilibrate with the left ventricular pressure. Large volume aortic valve regurgitation is accompanied by a wide aortic pulse pressure and with a rapid rising and collapsing systemic pulse.
If aortic regurgitation is severe, a third heart sound will be heard at the apex along with a low-pitched, vibratory mid-diastolic rumbling murmur. Referred to as the Austin Flint rumble, this murmur is due to competing jets of blood entering the ventricle from the regurgitant aortic valve and from the left atrium. The murmur may have presystolic accentuation, and may mimic the murmur of mitral stenosis.
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Updated March 2009