A 52-year-old man with uncontrolled hypertension presents with acute chest pain and dyspnea. Cardiac biomarkers are elevated. Histological examination of the myocardium shows coagulation necrosis with loss of nuclei and striations, but the cell membrane remains intact. Which of the following is the most common cause of this pattern of irreversible myocardial injury?

Explanation

## Most Common Cause of Irreversible Myocardial Injury **Key Point:** Ischemia due to coronary artery occlusion (acute myocardial infarction) is the most common cause of irreversible myocardial injury and coagulation necrosis in clinical practice. ### Pathophysiology of Ischemic Injury When myocardial blood flow is interrupted: 1. ATP depletion occurs within minutes 2. Na^+^/K^+^ ATPase fails → intracellular Na^+^ and Ca^2+^ accumulate 3. Mitochondrial dysfunction prevents energy recovery 4. Irreversible injury develops after 20–40 minutes of complete ischemia 5. Coagulation necrosis results from protein denaturation in the acidic, ischemic environment ### Histological Features of Coagulation Necrosis | Feature | Characteristic | |---------|----------------| | **Cell outline** | Preserved (cell membrane initially intact) | | **Nucleus** | Pyknotic, then karyorrhexis, then lost | | **Cytoplasm** | Eosinophilic, hyperchromatic | | **Striations** | Lost (in myocardium) | | **Timeline** | Becomes evident 4–12 hours post-infarction | **Clinical Pearl:** The intact cell membrane in early coagulation necrosis distinguishes it from liquefactive necrosis (seen in infections and CNS) where the membrane ruptures early. ### Epidemiology in India Coronary artery disease and acute MI are the leading causes of death in urban Indian populations, making ischemic injury the most frequently encountered irreversible injury pattern in autopsy and clinical practice. **High-Yield:** Ischemia is the **single most common** cause of irreversible cell injury globally and in India. It accounts for >90% of acute myocardial necrosis cases.