A young man with severe aortic regurgitation has a soft mid-diastolic rumble at the apex, raising the question of an Austin Flint murmur versus coexistent rheumatic mitral stenosis. Which bedside manoeuvre best separates the two?

• A Handgrip: the true mitral stenosis murmur disappears entirely
• B Amyl nitrite inhalation: the Austin Flint murmur becomes louder while a true mitral stenosis murmur softens
• C Squatting: the Austin Flint murmur disappears entirely
• D Amyl nitrite inhalation: the Austin Flint murmur softens while a true mitral stenosis murmur becomes louder ✓

Explanation

Amyl nitrite is a potent arterial vasodilator. It lowers systemic vascular resistance, reducing the regurgitant volume in aortic regurgitation and therefore softening the Austin Flint murmur, which is produced by the AR jet fluttering the anterior mitral leaflet. Simultaneously the reflex tachycardia and raised cardiac output increase transmitral flow, so a true rheumatic mitral stenosis murmur becomes louder. This opposite response is the classical discriminating test taught in cardiology texts.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.