Complications of MI

MI Complications - Timeline of Trouble

• Acute (0-48 hours)

  • Arrhythmias (esp. V-fib): #1 cause of early death.
  • Cardiogenic shock.
  • Acute congestive heart failure.

• Subacute (3-14 days)

  • Free wall rupture → Cardiac tamponade.
  • Papillary muscle rupture → Acute severe mitral regurgitation.
  • Interventricular septal rupture → VSD.
  • Fibrinous pericarditis.

• Chronic (>2 weeks)

  • Dressler syndrome (autoimmune pericarditis).
  • True ventricular aneurysm → Mural thrombus.
  • Chronic heart failure.

⭐ A new, harsh holosystolic murmur 5-7 days post-MI strongly suggests a ventricular septal rupture, typically heard best at the left sternal border.

Electrical Instability - Faulty Wiring Fiascos

• Arrhythmias are the most common cause of death in the first 48 hours post-MI.
• Ventricular Fibrillation (VFib):
  • Most frequent cause of sudden cardiac death, especially in the first 24 hours.
  • Requires immediate defibrillation.
• Ventricular Tachycardia (VTach):
  • Can be sustained or non-sustained; may lead to VFib.
  • Treat with amiodarone or synchronized cardioversion if hemodynamically unstable.
• AV Block:
  • Commonly associated with inferior wall MIs (RCA occlusion).
  • Often transient; treat symptomatic bradycardia with atropine or temporary pacing.

⭐ Post-inferior MI, new-onset heart block (especially complete heart block) is a major concern due to ischemia of the AV node, which is typically supplied by the RCA.

Mechanical Ruptures - Structural Catastrophes

*Occur subacutely (3-14 days) post-MI as macrophages degrade structural collagen, leading to catastrophic failure. Presents with sudden, severe hypotension and shock.

📌 Mnemonic: Remember the timeline: Inflammation (1-3 days) → Softening/Rupture (3-14 days) → Scarring (>2 weeks).

Pump & Pericardial Problems - Powerless & Pained

• Cardiogenic Shock (Killip IV): Severe LV dysfunction causing hypotension (SBP <90 mmHg), ↓ cardiac index (<2.2 L/min/m²), and pulmonary congestion (PCWP >18 mmHg).

• Pericardial Inflammation: Two distinct forms based on timing.

-   **Early Post-Infarction Pericarditis:** Occurs **1-3** days post-MI. Treat with high-dose Aspirin.
-   **Dressler Syndrome:** Autoimmune-mediated, weeks to months later. Treat with NSAIDs/Colchicine.

⭐ The friction rub in early pericarditis is often transient; in Dressler's, it's more persistent.

Chronic Remodeling - Scars and Stretches

• True Ventricular Aneurysm: A late complication, occurring >2 weeks to months post-MI. The infarcted wall is replaced by a thin, non-contractile fibrous scar that bulges paradoxically during systole.
  • Key Feature: Persistent ST-segment elevation in the leads of the prior infarction.
  • Major Risks: Formation of a mural thrombus leading to systemic embolization, and progressive heart failure.

⭐ Unlike a pseudoaneurysm, a true ventricular aneurysm has a low risk of rupture because it is composed of fibrous scar tissue.

High‑Yield Points - ⚡ Biggest Takeaways

• Ventricular fibrillation is the most common cause of death within 24 hours post-MI.
• Papillary muscle rupture (2-7 days) causes acute, severe mitral regurgitation.
• Ventricular free wall rupture (5-14 days) leads to cardiac tamponade and sudden death.
• Interventricular septal rupture (3-5 days) creates a VSD with a new holosystolic murmur.
• Ventricular aneurysm (weeks later) causes persistent ST elevation and risk of mural thrombus.
• Dressler syndrome is an autoimmune pericarditis occurring weeks to months post-MI.