What is the Austin Flint murmur (mid-diastolic rumble)?

From the Guidelines

The Austin Flint murmur is a low-pitched, rumbling diastolic murmur that occurs in severe, chronic aortic regurgitation (AR) and is typically heard at the left ventricular (LV) apex.

Characteristics of the Austin Flint Murmur

• It is a mid-diastolic or presystolic murmur that may be mistaken for the murmur of mitral stenosis (MS) [ 1, [ 1 ].
• The murmur is thought to be caused by the regurgitant jet from the aortic valve interfering with the normal closure of the mitral valve, leading to a relative mitral stenosis [ 1 ].
• The Austin Flint murmur is often associated with other signs of severe AR, such as a wide pulse pressure, a displaced LV impulse, and characteristic peripheral findings [ 1 ].

Diagnosis and Differentiation

• The diagnosis of the Austin Flint murmur can be made on the basis of physical examination and echocardiography [ 1 ].
• Echocardiography can help to confirm the diagnosis of AR, assess the severity of the regurgitation, and evaluate LV function [ 1 ].
• The Austin Flint murmur can be distinguished from the murmur of MS by the presence of other signs of AR and by the response to pharmacological interventions, such as amyl nitrite inhalation [ 1 ].

Clinical Significance

• The Austin Flint murmur is a significant finding in patients with severe AR, as it indicates a high likelihood of significant regurgitation and potential LV dysfunction [ 1 ].
• Patients with the Austin Flint murmur should undergo further evaluation and management to prevent complications, such as heart failure and arrhythmias [ 1 ].

From the Research

Definition and Characteristics of the Austin Flint Murmur

• The Austin Flint murmur is a mid-diastolic rumble associated with significant aortic regurgitation 2, 3, 4, 5.
• It is typically heard at the apex and is thought to be caused by the aortic regurgitation jet abutting the left ventricular endocardium, resulting in the generation of a low-pitched diastolic rumbling sound 3.
• The murmur is not recordable in the left atrium and has a maximum intensity in the left ventricular inflow tract 2.

Mechanism of the Austin Flint Murmur

• The precise mechanism of the murmur remains unclear, but studies suggest that it is related to the interaction between the aortic regurgitation jet and the mitral valve 4, 5.
• The direction of the aortic regurgitation jet is unrelated to the presence of the Austin Flint murmur, but the severity of aortic regurgitation is greater in patients with the murmur 4.
• The murmur is not caused by diastolic mitral regurgitation or functional mitral stenosis, but rather by the aortic regurgitation jet distorting the shape of the anterior mitral leaflet as it opens and closes during diastole 5.

Clinical Significance of the Austin Flint Murmur

• The Austin Flint murmur is an important clinical finding in patients with aortic regurgitation and can be a useful diagnostic tool in the assessment of patients with suspected aortic dissection 6.
• The presence of the murmur is associated with a greater frequency of localized anterior mitral leaflet distortion and Doppler striations overlying the aortic insufficiency jet 5.
• The murmur can be heard in conjunction with other murmurs, such as systolic murmurs and continuous murmurs, and can be an important clue to the diagnosis of aortic dissection 6.