Physiological Basis of Murmur Changes with Valsalva
Valsalva Maneuver Effect on Preload
Key Point
Valsalva maneuver (straining phase) decreases venous return to the heart, reducing left ventricular preload and end-diastolic volume.
Mitral Regurgitation Murmur Physiology
In mitral regurgitation (MR), the intensity and duration of the murmur depend directly on:
Why Valsalva Decreases MR Murmur
- 1.
Decreased venous return → ↓ LV preload → ↓ LV end-diastolic volume
- 2.
Reduced regurgitant volume across the incompetent mitral valve
- 3.
Murmur intensity decreases proportionally
Contrast with Other Maneuvers
| Maneuver | LV Preload | LV Afterload | MR Murmur | Mechanism |
|---|
| Valsalva | ↓ | ↓ | ↓ | ↓ regurgitant volume |
| Hand grip | ↔ | ↑ | ↑ | ↑ afterload → ↑ regurgitant jet |
| Squatting | ↑ | ↑ | ↑ | ↑ preload + afterload |
| Standing | ↓ | ↓ | ↓ | ↓ preload |
Clinical Pearl
Hand grip increases afterload, which paradoxically increases the MR murmur because higher LV pressure drives more blood retrograde into the LA. This is a key bedside maneuver for confirming MR.
High-YieldNEET PG
The murmur of MR is holosystolic (pansystolic) because regurgitation occurs throughout systole whenever LV pressure exceeds LA pressure. It radiates to the axilla because the regurgitant jet is directed posteriorly toward the pulmonary veins.
Why the Correct Answer
Valsalva reduces preload → ↓ LV volume → ↓ regurgitant volume → ↓ murmur intensity. This is the primary mechanism.
