Bit · Cardio
Cardiac Murmurs by Location and Timing
Every murmur on Step 1 maps to a location, a timing, and a manoeuvre. This is the cheat sheet.
Mechanism
A murmur tells you three things: where it's loudest, when in the cycle, and how it responds to manoeuvres:
- Systolic murmurs — heard between S1 and S2. Aortic stenosis, mitral regurgitation, mitral valve prolapse, tricuspid regurgitation, VSD, HOCM, pulmonic stenosis, flow murmurs.
- Diastolic murmurs — heard between S2 and S1. Aortic regurgitation, mitral stenosis, pulmonic regurgitation, tricuspid stenosis. ALWAYS pathological.
- Continuous murmurs — PDA (machine-like), AV fistula, ruptured sinus of Valsalva, mammary souffle of pregnancy.
Differentiator Table
| Murmur | Timing | Best heard | Quality | Distinguishing features |
|---|---|---|---|---|
| Aortic stenosis | Crescendo-decrescendo systolic | Right 2nd ICS, radiates to carotids | Harsh, mid-systolic | Pulsus parvus et tardus; ↓ with Valsalva (vs HOCM ↑) |
| Mitral regurgitation | Holosystolic | Apex, radiates to axilla | Blowing | ↑ with handgrip (↑ afterload) |
| Tricuspid regurgitation | Holosystolic | Left lower sternal border | Blowing | ↑ with inspiration (Carvallo sign) |
| VSD | Holosystolic | Left lower sternal border | Harsh | No radiation to axilla; ↑ with handgrip |
| Mitral valve prolapse | Mid-systolic click + late systolic | Apex | Click then murmur | ↑ with Valsalva (smaller LV → earlier prolapse) |
| HOCM | Crescendo-decrescendo systolic | Left lower sternal border | Harsh | ↑ with Valsalva, ↑ with standing (vs AS opposite) |
| Aortic regurgitation | Early decrescendo diastolic | Left sternal border, sitting forward | High-pitched, blowing | Wide pulse pressure; water-hammer, Quincke, Duroziez, head-bobbing |
| Mitral stenosis | Mid-diastolic with opening snap | Apex, left lateral decubitus | Low-pitched rumble | Loud S1; rheumatic origin; opening snap |
| PDA | Continuous (machine-like) | Left infraclavicular | 'Machinery' | Wide pulse pressure |
The Pivot
Three questions to localize any murmur:
- Systolic or diastolic? If diastolic — always pathological.
- Where is it loudest? Aortic area (R 2nd ICS) → AS or AR. Apex → MS or MR. LLSB → VSD, HOCM, TR.
- Manoeuvre response? ↑ with Valsalva → HOCM or MVP. ↓ with Valsalva → AS, MR. ↑ with inspiration → right-sided (Carvallo).
NBME-Style Stem
A 32-year-old woman is found to have a mid-systolic click followed by a late systolic murmur at the apex. The click moves earlier in systole and the murmur becomes longer when she stands up suddenly. Which of the following is the most likely diagnosis?
Concept Anchor
A murmur is a story in three parts: when, where, and how it changes. Timing names the valve, location names the side, and manoeuvres separate the lookalikes.