A 35-year-old woman with rheumatic mitral stenosis and a 28-year-old man with mitral regurgitation both present with cardiac murmurs. Which feature best distinguishes the murmur of mitral stenosis from that of mitral regurgitation?

Question

Accepted Answer

C. Presence of an opening snap and diastolic timing of the murmur. ## Distinguishing Mitral Stenosis from Mitral Regurgitation

### Key Auscultatory Features

| Feature | Mitral Stenosis | Mitral Regurgitation |
|---------|-----------------|----------------------|
| **Murmur Timing** | Diastolic (mid-to-late) | Systolic (holosystolic) |
| **Opening Snap** | Present (pathognomonic) | Absent |
| **Character** | Low-pitched, rumbling | High-pitched, blowing |
| **Radiation** | Localized to apex | Radiates to axilla/back |
| **Valsalva Response** | Unchanged or louder | Decreases |

**Key Point:** The opening snap (OS) is a hallmark of mitral stenosis and occurs in early diastole when the stenotic mitral valve abruptly halts its opening. This snap, followed by a diastolic rumble, is pathognomonic for MS and is the single best discriminator.

**High-Yield:** The opening snap occurs earlier in diastole (closer to A~2~) when stenosis is severe and LA pressure is high. This timing helps grade severity.

**Clinical Pearl:** In mitral regurgitation, the systolic murmur begins immediately after S~1~ (holosystolic) and obscures A~2~. There is no opening snap because the valve leaflets are already abnormal and do not snap shut.

### Mechanism of Opening Snap

The opening snap represents the abrupt deceleration of the stenotic mitral valve leaflets as they reach their maximum opening excursion. This occurs because:
1. The narrowed orifice limits leaflet excursion
2. Elevated LA pressure forces rapid valve opening
3. The rigid, thickened leaflets decelerate suddenly

**Warning:** Do not confuse the opening snap with S~3~ (ventricular gallop). The OS is earlier, sharper, and occurs in the setting of MS, not heart failure.

### Why This Discriminates Best

The presence of an opening snap combined with diastolic timing is virtually pathognomonic for mitral stenosis. Mitral regurgitation never produces an opening snap and has systolic timing — these two features together make option 1 the single best discriminator.

[cite:Harrison 21e Ch 236]

Answer

A. Loudness of the murmur and presence of a thrill

Answer

B. Timing in the cardiac cycle and response to Valsalva maneuver

Answer

D. Location of maximum intensity and radiation to the axilla

A 35-year-old woman with rheumatic mitral stenosis and a 28-year-old man with mitral regurgitation both present with cardiac murmurs. Which feature best distinguishes the murmur of mitral stenosis from that of mitral regurgitation?

Explanation

Practice similar questions