A diastolic rumble at the apex that is accentuated in the left lateral decubitus position is most characteristic of which lesion?

• A. Aortic stenosis
• B. Mitral stenosis
• C. Mitral regurgitation
• D. Tricuspid stenosis

Answer: (B)

The key idea is that a diastolic murmur heard at the apex that becomes louder in the left lateral decubitus position is classic for mitral stenosis. When the mitral valve is narrowed, blood flows from the left atrium into the left ventricle during diastole in a turbulent, low-frequency way, producing a mid‑diastolic rumble. The murmur is often accompanied by presystolic accentuation as the atrium contracts late in diastole, pushing more blood across the stenotic valve.

The left lateral decubitus position brings the left atrium closer to the chest wall and increases venous return, making low-pitched, diastolic sounds at the apex more audible. The murmur is best heard with the bell at the apex, and sometimes an opening snap after S2 can be heard, which further supports mitral stenosis.

Other lesions produce different timing and locations for murmurs—for example, a systolic murmur at the right upper sternal border points to aortic stenosis, and a holosystolic murmur at the apex radiating to the axilla points to mitral regurgitation—so the described diastolic apex rumble in this position most fits mitral stenosis.