Diastolic Murmurs - Aortic Regurgitation

     You are listening to a typical murmur caused by aortic valve regurgitation. Aortic regurgitation is mostly seen in males, with a 3:1 ratio as compared to females. In 2/3 of cases, the regurgitation is secondary to rheumatic heart disease, and may have a component of aortic stenosis. Aortic regurgitation may also be primarily congenital or associated with syphilis infection, Marfan syndrome, or valvular deterioration due to infective endocarditis.

     The murmur of aortic regurgitation is complex. The left ventricle is typically dilated secondary to extreme volume overload, as it must handle both the forward flow delivered from the left atria as well as the regurgitant flow from the aorta. This large volume of blood is ejected rapidly during systole, and an early mid-systolic flow murmur is frequently audible over the right upper sternal border with radiation into the neck.

     The most notable aspect of the murmur is the diastolic sound produced as the blood flows retrograde back into the left ventricle. This murmur is usually characterized as blowing, decrescendo, and heard best in the third left intercostal space. In severe regurgitation, it may be holodiastolic. It radiates widely along the left sternal border.

     Finally, a third murmur, known as an Austin Flint murmur, may be detected. This is a soft, rumbling, low-pitched, late diastolic murmur which is heard best at the apex. It is thought to be due to a functional mitral valve stenosis, as the backflow of blood from the aorta presses on the anterior leaflet of the mitral valve, slightly occluding the flow from the atria. The atrial kick just before systole accentuates this flow, producing the Austin Flint murmur.

     Any maneuver which increases systemic vascular resistance will increase the murmur of aortic regurgitation, as it will tend to favor backflow into the ventricle. This includes handgrip and isometric excercise.