Austin flint murmur
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Austin Flint murmur aortic regurgitation diagram
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I have enough detail. Let me pull the Harrison's continued paragraph on the mechanism (line 1315+) for completeness.
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"Austin Flint murmur" aortic regurgitation
Austin Flint Murmur
What it is: A soft, low-pitched, rumbling mid-to-late diastolic murmur heard at the cardiac apex in patients with severe (usually chronic) aortic regurgitation (AR). It can mimic the diastolic murmur of mitral stenosis, but it is not caused by true mitral valve obstruction.
Mechanism:
The regurgitant jet from the incompetent aortic valve strikes the anterior leaflet of the mitral valve during diastole, displacing it and creating turbulence at the mitral orifice. This produces functional (relative) mitral stenosis and the resulting rumble, without any anatomic narrowing of the mitral valve (Harrison's Principles of Internal Medicine, 22E, p. 2088; Fuster and Hurst's The Heart, 15th ed., p. 2052-2057). On echocardiography this correlates with rapid, high-frequency diastolic fluttering of the anterior mitral leaflet from the impact of the regurgitant jet.
Clinical features:
- Best heard at the apex, low-pitched and rumbling
- Occurs in chronic, severe AR specifically
- Sensitivity is highly variable (reported 0-100% across studies) - Symptom to Diagnosis: An Evidence-Based Guide, 4th ed.
- Must be distinguished from mitral stenosis: handgrip isometric exercise (increases afterload) tends to intensify the Austin Flint murmur (and AR murmurs generally), while amyl nitrite (decreases afterload) can help differentiate it from true mitral stenosis rumble
- Other AR-associated exam findings that often accompany it: wide pulse pressure, water-hammer (Corrigan's) pulse, Quincke's capillary pulsations, Traube's "pistol-shot" sign over the femoral arteries, Duroziez's sign, and the classic decrescendo early diastolic murmur of AR heard best at the left 3rd intercostal space (Erb's point) with the patient sitting forward in expiration.
Diagnostic workup: Echocardiography is the test of choice whenever a diastolic murmur is heard, and is mandatory in any patient with a dilated aortic root, to confirm AR severity and characterize the mechanism.
Recent evidence note: A 2022 imaging study (PMID: 35373249, Eur Heart J Cardiovasc Imaging) used 2D/3D echocardiography to further clarify the mechanistic basis of the Austin Flint murmur, generally supporting the classic teral-leaflet-impingement mechanism described above rather than contradicting it - so the textbook explanation remains current.
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