A 62-year-old man with a long history of hypertension is found to have a late systolic murmur that increases with Valsalva maneuver. Which feature best distinguishes this from a holosystolic murmur of mitral regurgitation?

Explanation

## Distinguishing Mitral Valve Prolapse from Mitral Regurgitation **Key Point:** The midsystolic click is the hallmark of mitral valve prolapse (MVP) and distinguishes it from holosystolic mitral regurgitation. The click represents the sudden tensioning of the chordae tendinae when the leaflet prolapses into the left atrium. ### Pathophysiology of the Midsystolic Click The click occurs when: 1. Left ventricular pressure exceeds left atrial pressure (mid-to-late systole) 2. The redundant mitral leaflet(s) suddenly prolapse into the atrium 3. The chordae tendinae abruptly tense, creating a high-frequency sound 4. A late systolic murmur follows if mitral regurgitation develops ### Comparison Table: MVP vs Holosystolic MR | Feature | Mitral Valve Prolapse (MVP) | Holosystolic Mitral Regurgitation | | --- | --- | --- | | **Timing of murmur** | Late systolic (after click) | Holosystolic (S1 to S2) | | **Midsystolic click** | Present (pathognomonic) | Absent | | **Valsalva response** | Click & murmur move earlier (increase) | Murmur decreases | | **Leg raising response** | Click & murmur move later (decrease) | Murmur increases | | **Etiology** | Myxomatous degeneration, connective tissue disorder | Rheumatic, ischemic, endocarditis, dilated cardiomyopathy | | **Radiation** | Apex, may not radiate | Apex to axilla | | **Associated findings** | Palpitations, syncope (rare) | Signs of heart failure, AF | **High-Yield:** The midsystolic click is: - Heard best with the diaphragm at the apex - High-pitched and crisp - Moves earlier (toward S1) with Valsalva or standing (decreased preload) - Moves later (toward S2) with leg raising or squatting (increased preload) - Absent in holosystolic MR, making it the single best discriminator **Mnemonic:** **MVP-CLICK** = Myxomatous Valve Prolapse—Click is the Landmark Indicator of Cardiac Kinetics ### Hemodynamic Basis of Valsalva Response ```mermaid flowchart TD A[Valsalva maneuver]:::action --> B[Decreased venous return]:::outcome B --> C[Decreased LV volume]:::outcome C --> D{MVP vs MR?}:::decision D -->|MVP| E[Prolapse occurs earlier in systole]:::outcome D -->|MR| F[Less blood to eject → murmur softer]:::outcome E --> G[Click & murmur move toward S1]:::outcome F --> G ``` **Clinical Pearl:** In a hypertensive patient with a late systolic murmur that *increases* with Valsalva (click moves earlier, murmur louder), think MVP. In contrast, holosystolic MR murmur *decreases* with Valsalva. ### Why Other Options Fail - **Absence of radiation to axilla:** MVP murmurs may not radiate widely, but this is not a reliable discriminator—some MVP murmurs do radiate, and some MR murmurs are localized. - **Decreased intensity with leg raising:** This is actually a feature of MVP (increased preload delays prolapse, moving the click and murmur later). Holosystolic MR murmur *increases* with leg raising. This is a valid discriminator but less specific than the click itself. - **Occurrence only in the fourth intercostal space:** Both MVP and MR are best heard at the apex (5th intercostal space, midclavicular line). This option is anatomically incorrect and not a discriminator. [cite:Harrison 21e Ch 237]