Critical medicine topic-CMT 013

MITRAL VALVE PROLAPSE (MVP):

EFFECT OF HEMODYNAMIC MANEUVERS ON

THE CLICK AND MURMUR

 

Introduction

The auscultatory findings of Mitral Valve Prolapse (MVP) depend primarily on the left ventricular (LV) volume. During systole, the mitral valve leaflets prolapse into the left atrium when the LV cavity becomes sufficiently small that the leaflets lose their normal coaptation. This produces the characteristic mid-systolic click, followed by a late systolic murmur due to mitral regurgitation (MR). Any maneuver that alters LV volume changes the timing and intensity of these auscultatory findings.

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Mechanism

• During systole, progressive ventricular contraction reduces LV volume.
• When LV volume falls below a critical level, the mitral valve leaflets prolapse into the left atrium.
• At this point:
• A mid-systolic click is produced.
• A late systolic murmur begins due to mitral regurgitation.

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Maneuvers that Decrease LV Volume

These maneuvers cause the valve to prolapse earlier during systole.

Examples

• Straining phase of the Valsalva maneuver
• Sudden standing
• Early inhalation of amyl nitrite

Effects

• LV volume decreases.
• Mitral valve prolapses earlier.
• Click moves closer to S1.
• Murmur begins earlier.
• Murmur becomes longer because MR lasts for a greater portion of systole.

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Maneuvers that Increase LV Volume

These maneuvers delay prolapse by increasing ventricular filling.

Examples

• Squatting
• Leg raising
• Sudden change from standing to supine/prone
• Isometric handgrip
• Propranolol (slows heart rate, increasing diastolic filling)

Effects

• LV volume increases.
• Prolapse occurs later.
• Click moves toward S2.
• Murmur becomes shorter and softer.
• In some patients, the murmur may disappear completely.

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Effect on Mitral Regurgitation

When prolapse is delayed:

• Severity of mitral regurgitation decreases.
• Murmur duration shortens.
• Murmur intensity decreases.

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Special Note: Effect of Amyl Nitrite

Amyl nitrite produces a characteristic biphasic response.

Immediate Effect

• Peripheral vasodilation lowers LV volume.
• Click occurs earlier.
• Click usually becomes softer.
• Murmur initially becomes softer.

After About 15 Seconds

• Reflex sympathetic activation raises blood pressure.
• Mitral regurgitation increases.
• Murmur becomes louder despite the earlier click.

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Summary Table

Maneuver	LV Volume	Click	Murmur
Valsalva (strain)	↓	Earlier (toward S1)	Earlier, longer
Standing	↓	Earlier	Earlier, longer
Amyl nitrite (early)	↓	Earlier	Initially softer
Squatting	↑	Later (toward S2)	Shorter, softer
Leg raising	↑	Later	Softer
Supine/Prone position	↑	Later	Softer
Handgrip	↑	Later	Shorter, less intense
Propranolol	↑	Later	Less intense

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Clinical Pearls

• Smaller LV → Earlier click and longer murmur.
• Larger LV → Later click and shorter murmur.
• MVP is one of the few cardiac conditions in which the timing of the murmur changes dramatically with bedside maneuvers.
• Recognition of these dynamic changes helps distinguish MVP from other systolic murmurs during clinical examination.

Examination Mnemonic

"Small LV = Soon Click"

• Small LV (Valsalva, Standing) → Soon click, longer murmur.
• Large LV (Squatting, Leg raise, Handgrip, Propranolol) → Late click, shorter and softer murmur.

DR.C.GANESAN M.D.,

PROFESSOR OF MEDICINE