Cardiovascular is the highest-yield system on Step 1 — approximately 20–25% of your exam. Master this section and you've earned a quarter of your score.
Heart Sounds: The Clinical Correlates
| Heart sound | Timing | Associated with |
|---|---|---|
| S3 (ventricular gallop) | Early diastole | Normal in children/athletes; in adults: dilated cardiomyopathy, heart failure |
| S4 (atrial gallop) | Late diastole (pre-systole) | Hypertensive heart disease, hypertrophic cardiomyopathy, MI |
| Friction rub | Throughout cycle | Pericarditis — scratchy sound, changes with position |
| Opening snap | Early diastole | Mitral stenosis — high-pitched, followed by rumbling diastolic murmur |
| Systolic click | Mid-systole | Mitral valve prolapse |
Murmurs: The High-Yield Distinctions
| Valve lesion | Timing | Key features | Maneuver effect |
|---|---|---|---|
| Aortic stenosis | Systolic (crescendo-decrescendo) | Radiates to neck, pulsus parvus et tardus | Increases with squatting |
| Mitral regurgitation | Holosystolic | Radiates to axilla, blowing quality | Increases with squatting/handgrip |
| Mitral stenosis | Diastolic (rumble) | Opening snap, best at apex | Increases in left lateral decubitus |
| Aortic regurgitation | Diastolic (blowing) | Bounding pulse, wide pulse pressure | Increases with sitting forward |
| MVP | Late systolic + click | Click moves earlier with standing | Click earlier with Valsalva/standing |
| HOCM | Systolic | Increases with Valsalva/standing | Decreases with squatting/handgrip |
MI: Time Course of Findings
| Time after MI | Gross findings | Micro findings | Complications |
|---|---|---|---|
| 0–4 hours | None (normal gross) | None visible yet | Arrhythmia (most common early cause of death) |
| 4–24 hours | Dark mottling | Coagulative necrosis, neutrophil infiltration begins | Arrhythmia, cardiogenic shock |
| 1–3 days | Pallor | Neutrophil infiltration peak | Fibrinous pericarditis |
| 3–14 days | Yellow-tan (softest point) | Macrophages replacing neutrophils | Free wall rupture, papillary muscle rupture, VSD |
| 2 weeks–2 months | Gray-white fibrosis | Granulation tissue → fibrosis | Dressler's syndrome (weeks 2–10) |
Congenital Heart Disease: The High-Yield Cases
Left-to-right shunts (acyanotic initially)
- VSD: Most common CHD. Harsh holosystolic murmur at lower left sternal border.
- ASD: Fixed split S2. Ostium secundum most common type.
- PDA: Continuous machine-like murmur. Indomethacin closes; PGE1 maintains. Associated with congenital rubella.
Right-to-left shunts (cyanotic from birth — "5 Ts")
- Tetralogy of Fallot: VSD + RV outflow obstruction + overriding aorta + RVH. Boot-shaped heart. Tet spells relieved by squatting.
- Transposition of great arteries: Aorta from RV, PA from LV. Requires mixing to survive — PDA or ASD.
- Truncus arteriosus, Total anomalous pulmonary venous return, Tricuspid atresia
Step 1 cardiology strategy: Master the murmur maneuvers — they appear on 3–5 questions per exam. Key rule: anything that decreases venous return (standing, Valsalva) worsens HOCM and MVP (click moves earlier). Anything that increases venous return (squatting, lying down, handgrip) improves HOCM and MVP, worsens AS and MR.
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