The Austin Flint Murmur Versus the Mitral Stenosis Murmur

1. What is the Austin Flint murmur [4]?

ANS: It is an apical diastolic rumble imitating the murmur of organic MS but is due to an aortic regurgitation (AR) stream that prevents the mitral valve from opening fully.

2. What is the most plausible theory explaining the mechanical cause of the Austin Flint murmur?

ANS: The AR stream may impinge on the undersurface of the anterior leaflet of the mitral valve and push it up, creating a relative MS. Support for this theory is found in the following:

a. A yellow plaque (jet lesion) occurs on the septal surface of the anterior mitral leaflet of some patients with the Austin Flint murmur [5].

b. When an Austin Flint murmur is present, the amplitude of opening of the mitral anterior leaflet is reduced on echocardiograms.

Note: Echocardiograms often show fluttering of the anterior mitral leaflet in patients with Austin Flint murmurs. This was once thought to be the cause of the murmur, but some patients with the fluttering leaflets have no Austin Flint murmur, and some with the Austin Flint murmur have no flutter.

Austin Flint Murmur

Jet lesion often seen here

The aortic regurgitant (AR) stream holds the anterior leaflet up into a semiclosed position. This accounts for the mitral diastolic rumble mimicking mitral stenosis and for the attenuated opening snap in patients with both mitral stenosis und aortic regurgitation.

Jet lesion often seen here

The aortic regurgitant (AR) stream holds the anterior leaflet up into a semiclosed position. This accounts for the mitral diastolic rumble mimicking mitral stenosis and for the attenuated opening snap in patients with both mitral stenosis und aortic regurgitation.

3. What suggests that the apical diastolic murmur in severe AR is at least sometimes due to transmission of the low-frequency components of the AR murmur to the apex?

ANS: It sometimes starts with the S2, i.e., before the mitral valve has had a chance to open, and persists at end of diastole even when mitral inflow has ceased (by Doppler) when LV pressure has exceeded left atrial pressure.

4. Is there a presystolic crescendo in the Austin Flint murmur?

ANS Rarely. The presystolic accentuation of the Austin Flint murmur even when present is often a subtle finding and does not have a marked crescendo to the Sj.

Note: Austin Flint called the murmur "presystolic." But he also wrote that the classical pandiastolic murmur of pure mitral stenosis was also "presystolic"

Austin Flint Murmur

Phonocardiograms and LV pressure tracing from a 45-year-old man with marked orthopnea who had an Austin Flint murmur due to severe AR resulting from a previous infective endocarditis. Note that the diastolic rumble at the apex begins even before the S3 was recorded externally. Note also the absence of a presystolic crescendo and the soft Mj.

Phonocardiograms and LV pressure tracing from a 45-year-old man with marked orthopnea who had an Austin Flint murmur due to severe AR resulting from a previous infective endocarditis. Note that the diastolic rumble at the apex begins even before the S3 was recorded externally. Note also the absence of a presystolic crescendo and the soft Mj.

5. How can you differentiate an Austin Flint murmur from the murmur of MS by auscultation?

ANS: a. If there is no OS, the chances that MS is present are diminished. But remember that AR can attenuate or eliminate an OS.

b. If there is no obvious presystolic crescendo to the Sj, it is more likely to be an Austin Flint murmur.

c. Amyl nitrite will produce a louder MS murmur after about 20 s, whereas an Austin Flint murmur immediately becomes softer or even disappears. The reason for this is that in AR there are two outlets for aortic blood during diastole, one outlet backward into the LV, the other forward into the peripheral arteries. Amyl nitrite lowers peripheral resistance, thus increasing the peripheral runoff, and therefore decreasing the amount of AR.

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Your heart pumps blood throughout your body using a network of tubing called arteries and capillaries which return the blood back to your heart via your veins. Blood pressure is the force of the blood pushing against the walls of your arteries as your heart beats.Learn more...

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