Mechanisms of Austin Flint murmur

Mechanisms of Austin Flint murmur

Mechanisms of Austin Flint murmur in aortic regurgitation – following are the proposed mechanisms for the mid diastolic murmur in mitral area in severe aortic regurgitation:

1. Fluttering of the anterior mitral leaflet due to the regurgitant jet impinging on it
2. Jet can produce relative narrowing of the mitral orifice
3. Elevation of left ventricular diastolic pressure causes the mitral valve to float back to a partially closed position
4. Diastolic mitral regurgitation due to elevated left ventricular diastolic pressure [1]

The fluttering of anterior mitral leaflet and early closure due the aortic regurgitation jet has been demonstrated in a case report by cine magnetic resonance imaging [2]. Severity of aortic regurgitation was demonstrated to be more in those with Austin Flint murmur than those without the murmur [3].

A Doppler echo study did not support mechanisms 2 and 4 described above, while supporting mechanism 1 [4].

References

1. Brandão AP, Lipton MJ. Mitral diastolic regurgitation and the Austin Flint murmur. Arq Bras Cardiol. 1970 Oct;23(5):319-26.
   
2. Weir RA, Dargie HJ. Images in clinical medicine. Austin flint murmur. N Engl J Med. 2008 Sep 4;359(10):e11.
3. Emi S, Fukuda N, Oki T, Iuchi A, Tabata T, Kiyoshige K, Fujimoto T, Manabe K, Ito S. Genesis of the Austin Flint murmur: relation to mitral inflow and aortic regurgitant flow dynamics. J Am Coll Cardiol. 1993 May;21(6):1399-405.
4. Rahko PS. Doppler and echocardiographic characteristics of patients having an Austin Flint murmur. Circulation. 1991 Jun;83(6):1940-50.