A patient had an acute inferior, transmural myocardial infarction 4 days ago. A new murmur raises the suspicion of mitral regurgitation due to papillary muscle rupture. Which of the following murmur descriptions describes this condition?

• A. A grade III/VI diastolic murmur heard best at the apex without radiation.
• B. A grade IV/VI systolic ejection murmur heard best at the base with radiation to the left clavicle.
• C. A grade II/VI systolic murmur heard best at the apex preceded by a click and without radiation.
• D. A grade IV/VI systolic murmur heard best at the apex with radiation to the left axilla.

Answer: (D)

The scenario tests understanding of acute mitral regurgitation from papillary muscle rupture after a myocardial infarction. When the papillary muscle ruptures, the mitral valve fails to coapt during systole, causing a large amount of blood to regurgitate from the left ventricle into the left atrium. This produces a holosystolic murmur that is typically high-pitched and harsh, best heard at the apex, and it radiates to the left axilla due to the direction of the regurgitant jet toward the atrium and into the axillary region. In this setting—an inferior wall MI about a few days old—a new, loud systolic murmur at the apex with radiation to the axilla fits acute MR from papillary muscle rupture, often described as a high-grade (loud) murmur because of the large regurgitant volume. The other patterns don’t fit: a diastolic murmur at the apex suggests mitral stenosis or another diastolic lesion; a systolic ejection murmur at the base radiating to the clavicle points toward aortic pathology; and a systolic murmur at the apex preceded by a click is characteristic of mitral valve prolapse, not papillary muscle rupture–induced MR.