What is the description of an Aortic Regurgitation (AR) murmur?

Aortic Regurgitation Murmur Description

An aortic regurgitation (AR) murmur is characterized as a high-pitched, decrescendo diastolic murmur that begins immediately after S2, consistent with the rapid decline in volume or rate of regurgitation during diastole. 1

Key Characteristics of AR Murmur

• The murmur begins with or shortly after the second heart sound (S2), when left ventricular pressure drops sufficiently below aortic pressure 1
• It is typically high-pitched and decrescendo in nature, reflecting the gradually decreasing pressure gradient between the aorta and left ventricle during diastole 1
• The murmur is best heard at the left sternal border with the patient leaning forward and in held expiration 1
• In severe chronic AR, a low-pitched, rumbling diastolic murmur (Austin-Flint murmur) may also be present at the left ventricular apex; this can be either middiastolic or presystolic 1
• An opening snap is absent in isolated AR, which helps differentiate it from mitral stenosis 1

Dynamic Auscultation Findings

The AR murmur demonstrates specific responses to various maneuvers that can aid in diagnosis:

• The murmur increases with handgrip exercise 1
• Transient external compression of both arms by bilateral cuff inflation to 20 mm Hg greater than peak systolic pressure augments the murmur of AR 1
• During the initial relative hypotension after amyl nitrite inhalation, the AR murmur decreases 1
• With standing, the murmur typically diminishes, while with brisk squatting, it becomes louder 1
• Left-sided murmurs like AR are usually louder during expiration rather than inspiration 1

Associated Findings

• AR is often accompanied by systolic hypertension and wide pulse pressure, which account for peripheral physical findings such as bounding pulses 2, 3
• Interestingly, a systolic murmur is a common auscultatory finding in patients with moderate or milder AR, which can sometimes lead to missed diagnoses if careful attention is not paid to diastole 4, 3
• In severe chronic AR, the Austin-Flint murmur can sometimes be confused with mitral stenosis; however, amyl nitrite inhalation can help distinguish between them (the Austin-Flint murmur decreases while true mitral stenosis murmur increases during the tachycardia phase) 1

Clinical Pearls and Pitfalls

• The AR murmur may be missed if auscultation is not performed with the patient leaning forward and during held expiration 1, 3
• Don't be misled by the presence of a systolic murmur in AR patients; many patients with AR have associated systolic murmurs that may draw attention away from the softer diastolic component 4, 3
• The absence of an opening snap helps differentiate AR from mitral stenosis 1
• In acute AR, the murmur may be shorter and less impressive than in chronic AR due to rapid equilibration of aortic and left ventricular pressures, despite the condition being more hemodynamically severe 2, 5
• Always assess for the Austin-Flint murmur at the apex in patients with suspected AR, as its presence suggests more severe regurgitation 1