A 52-year-old man from Delhi presents with acute chest pain radiating to the left arm for 3 hours. He is diaphoretic and anxious. ECG shows ST elevation in leads II, III, aVF. Troponin I is markedly elevated at 4.2 ng/mL. He receives thrombolytic therapy 4 hours after symptom onset. On day 3, cardiac biopsy shows coagulative necrosis with loss of striations, hypereosinophilia, and dense neutrophilic infiltration. Which of the following best explains the histological appearance observed?

Explanation

## Histological Features in Acute Myocardial Infarction The clinical scenario describes acute ST-elevation myocardial infarction (STEMI) with subsequent reperfusion therapy. The histological findings on day 3 are classic for **coagulative necrosis**, the predominant form of cell death in acute MI. ### Key Distinguishing Features | Feature | Necrosis (Coagulative) | Apoptosis | |---------|------------------------|----------| | **Cell membrane integrity** | Lost early; rupture | Preserved initially; blebbing | | **Nuclear changes** | Pyknosis → karyorrhexis | Pyknosis → fragmentation into apoptotic bodies | | **Protein denaturation** | Marked; hypereosinophilia | Minimal | | **Inflammation** | Dense, acute (neutrophils) | Minimal or absent | | **Striations (muscle)** | Lost | Preserved until late | | **Organelles** | Swollen, disrupted | Condensed, intact initially | **Key Point:** Coagulative necrosis is the hallmark of acute MI because cardiac myocytes are highly metabolically dependent. Ischemia causes ATP depletion → loss of Na^+^/K^+^ ATPase → cell swelling (oncotic necrosis) → protein denaturation → hypereosinophilia. **High-Yield:** The dense neutrophilic infiltration on day 3 is a secondary response to necrotic cell death and tissue damage. This is a hallmark of necrosis, NOT apoptosis (which triggers minimal inflammation). **Clinical Pearl:** Reperfusion after thrombolysis can paradoxically accelerate necrotic cell death in the ischemic zone through reperfusion injury, but the morphology remains coagulative necrosis. ### Why Necrosis and Not Apoptosis? Apoptosis is an **energy-dependent** process requiring ATP for caspase activation and membrane blebbing. In acute ischemia, ATP is depleted within minutes, making apoptosis impossible. Necrosis is the inevitable outcome of severe, acute ischemia. [cite:Robbins 10e Ch 1]