Austin Flint murmur

**Definition:** A low-pitched, rumbling mid-to-late diastolic (sometimes presystolic) murmur heard best at the apex (left ventricular area) in severe chronic aortic regurgitation (AR). It is often accompanied by the early decrescendo diastolic murmur of AR at the left sternal border.

**Pathophysiology:** - The AR jet is directed posteriorly toward the anterior mitral leaflet during diastole. - The jet causes the leaflet to vibrate and partially close or flutter. This produces functional (relative) mitral stenosis. - Rapid LV filling from regurgitant volume raises LV diastolic pressure. This can cause early closure of the mitral valve. - The mitral valve itself is structurally normal.

**Clinical features of severe AR:** - Wide pulse pressure with a low diastolic pressure. - Bounding "water-hammer" (Corrigan) pulses. - Other signs: de Musset sign (head bobbing), Quincke pulses (nailbed capillary pulsations), Traube sign (pistol-shot femoral sounds), Duroziez sign (femoral to-and-fro murmur), and Müller sign (pulsating uvula). - Hyperdynamic, laterally displaced apical impulse (volume overload and eccentric LV hypertrophy). - Causes: **chronic** (bicuspid aortic valve, rheumatic heart disease, aortic root dilation, Marfan, syphilitic aortitis, ankylosing spondylitis) and **acute** (infective endocarditis, aortic dissection, trauma).

**Distinguishing from true mitral stenosis (MS):** - True MS has an **opening snap** after S2 and a loud S1. - Austin Flint has **no opening snap** and a normal or soft S1 (because of premature mitral closure). - Austin Flint **decreases** with vasodilators such as amyl nitrite. These reduce afterload and regurgitant flow. True MS murmur **increases** with amyl nitrite because reflex tachycardia increases flow. - Austin Flint **increases** with maneuvers that raise afterload, such as handgrip or squatting. The AR murmur also increases with handgrip.

**Other murmurs to remember in AR:** - Early decrescendo diastolic murmur, best heard with the patient sitting forward and in expiration. - Systolic flow murmur from increased stroke volume across the aortic valve (relative aortic stenosis).

**Management:** Treat the underlying AR. Vasodilators (nifedipine, ACE inhibitors) are used for chronic AR, and surgical aortic valve replacement is indicated for symptomatic severe AR or LV dysfunction/dilation. Acute severe AR needs urgent surgery. Beta-blockers are avoided in acute AR because they block compensatory tachycardia.

**Eponym:** Named after Austin Flint (1812–1886), an American physician.

**High-yield pearl:** Apical diastolic rumble + wide pulse pressure + no opening snap = Austin Flint murmur from severe AR.