Characteristic Features of Mitral Regurgitation Murmur
The murmur of mitral regurgitation is typically holosystolic, best heard at the apex, and radiates to the axilla, with the specific radiation pattern providing clues to the underlying leaflet pathology. 1, 2
Primary vs. Secondary Mitral Regurgitation Murmurs
Primary (Organic) MR Murmur Characteristics:
- Timing: Holosystolic (begins with S1 and continues to S2)
- Location: Best heard at the apex
- Radiation pattern:
- Anterior leaflet flail: Radiates to the axilla and left infrascapular area
- Posterior leaflet flail: Radiates anteriorly (can be confused with systolic ejection murmurs) 1
- Intensity: Usually grade 3/6 or louder
- Associated findings: Often accompanied by S3 gallop (diastolic filling complex) in severe MR 1
Secondary (Functional) MR Murmur Characteristics:
- Timing: Holosystolic
- Location: Best heard at the apex
- Radiation: Typically radiates to the axilla
- Associated findings: S3 gallop may be present but is harder to interpret as it may be due to underlying LV dysfunction 1
Special Variants of MR Murmurs
Late Systolic Murmur:
- Occurs in mitral valve prolapse
- Starts well after ejection and ends before or at S2
- Often preceded by a midsystolic click
- High-pitched at the LV apex 1
Silent Mitral Regurgitation:
- Rare but clinically significant variant
- Absence of the characteristic holosystolic murmur despite significant regurgitation
- More common in acute severe MR where a soft murmur may be missed 3, 4
- Should be suspected when there is hemodynamic deterioration in appropriate clinical settings 4
Response to Maneuvers
| Maneuver | Effect on MR Murmur |
|---|---|
| Respiration | Louder during expiration (left-sided) [2] |
| Valsalva | Usually decreases in intensity (except MVP which becomes longer/louder) [2] |
| Handgrip | Increases in intensity [2] |
| Standing | Usually diminishes (except MVP which may become louder) [2] |
| Squatting | Usually becomes louder (except MVP which may soften) [2] |
Clinical Pearls and Pitfalls
If the murmur of primary MR is not audible after listening in multiple positions or with dynamic maneuvers, or is limited to late systole only, the degree of MR is likely not severe 1
The presence of a diastolic filling complex (S3 plus short diastolic murmur) in primary MR usually indicates significant regurgitant volume and severe MR 1
Atrial fibrillation or other arrhythmias may make auscultation more challenging, particularly when the heart rate is rapid 1
In acute severe MR, the murmur may be soft or absent due to rapid equalization of left atrial and ventricular pressures, leading to potential diagnostic delays 4
Echocardiography is essential for definitive diagnosis, but physical examination findings should be used to establish pre-test probability and interpret imaging results appropriately 1
Discrepancies between physical examination and echocardiographic findings should prompt careful review of actual images rather than relying solely on the report 1