How does the Valsalva maneuver affect the murmur associated with Mitral Valve Prolapse (MVP)?

Effect of Valsalva Maneuver on MVP Murmur

During the Valsalva maneuver, the murmur associated with Mitral Valve Prolapse (MVP) becomes longer and often louder, which is a distinctive characteristic that helps differentiate it from most other cardiac murmurs. 1

Characteristics of MVP Murmur

MVP is characterized by:

• A midsystolic click (high-pitched sound of short duration)
• Often followed by a late systolic murmur
• The murmur is usually medium to high-pitched
• Loudest at the cardiac apex
• Sometimes has a musical or honking quality 1

Dynamic Auscultation and Valsalva Effect

The MVP murmur demonstrates distinctive behavior during dynamic auscultation:

Valsalva Maneuver Effect:

• Most cardiac murmurs decrease in length and intensity during Valsalva
• MVP murmur is an exception - it becomes longer and often louder 1
• This occurs because Valsalva decreases left ventricular end-diastolic volume
• With reduced ventricular filling, MVP occurs earlier in systole
• The click-murmur complex moves closer to the first heart sound
• After release of Valsalva, the murmur returns toward baseline 1

Other Postural Maneuvers:

• Standing: MVP murmur lengthens and often intensifies (similar to Valsalva effect)
• Squatting: MVP murmur usually softens and may disappear
• Passive leg raising: Similar effect as squatting - murmur softens 1

Physiological Mechanism

The dynamic changes in MVP murmur are related to left ventricular volume:

• Maneuvers that decrease LV volume (Valsalva, standing) cause earlier and more pronounced prolapse
• This happens because with reduced filling, the mitral apparatus becomes relatively redundant earlier in systole
• Decreased ventricular size allows earlier and greater prolapse of the mitral leaflets 2
• Conversely, maneuvers that increase LV volume (squatting, leg raising) delay prolapse and reduce murmur intensity

Clinical Significance

The distinctive response to Valsalva is diagnostically important:

• Helps differentiate MVP from other cardiac murmurs
• Only MVP and hypertrophic cardiomyopathy (HCM) murmurs increase with Valsalva
• HCM murmur becomes louder but doesn't change timing
• MVP murmur becomes both longer and often louder 1

Diagnostic Implications

This distinctive auscultatory response to Valsalva:

• Serves as a bedside diagnostic tool
• Helps confirm clinical suspicion of MVP before echocardiographic confirmation
• May reveal MVP murmurs that are otherwise difficult to detect in the supine position
• Should prompt consideration of echocardiography for definitive diagnosis 1

The presence of a late systolic murmur (rather than just an isolated click) may indicate a higher risk for complications including progressive mitral regurgitation, which has implications for morbidity and mortality 3.