Complications of Myocardial Infarction: High-Yield
Complications following a myocardial infarction (MI) are highly time-dependent. Mastering this timeline is a fundamental board examination requirement.
1. Chronological Complication Timeline
| Timeframe | Primary Complication(s) |
|---|---|
| 0–24 Hours | Arrhythmias (ventricular fibrillation, tachycardia), Heart failure, Cardiogenic shock. |
| 1–3 Days | Post-infarction fibrinous pericarditis (presents with friction rub/pleuritic chest pain). |
| 3–14 Days | Free wall rupture (tamponade), Interventricular septal rupture, Papillary muscle rupture (acute mitral regurgitation). |
| 2 Weeks–Months | Ventricular aneurysm (risk of mural thrombus/emboli), Dressler syndrome (autoimmune pericarditis). |
2. High-Yield Clinical Associations
- Free Wall Rupture: Occurs 3–7 days post-MI as macrophages clear necrotic tissue, causing the wall to become thin and soft. Leads to rapid cardiac tamponade and death.
- Papillary Muscle Rupture: Most commonly involves the posteromedial papillary muscle because it has a single blood supply (from the Posterior Descending Artery). Leads to sudden, severe mitral regurgitation.
- Dressler Syndrome: An autoimmune, inflammation-based pericarditis occurring weeks after MI. Treated with aspirin or NSAIDs.
- Ventricular Aneurysm: A late complication resulting from wall thinning and stretching of the scar tissue. Increases risk for ventricular thrombus formation due to stasis.
3. Must-Know Pathology
Pathology Note: While fibrinous pericarditis (1–3 days) is an early, localized inflammatory response to underlying necrosis, Dressler syndrome is a systemic, delayed autoimmune reaction against cardiac antigens.