A 58-year-old man from Delhi presents to the emergency department with acute onset chest pain radiating to the left arm for 2 hours. He is diaphoretic and anxious. Vital signs: BP 128/82 mmHg, HR 92 bpm, RR 18/min. On examination, he has no murmurs or crackles. His ECG shows ST-segment elevation in leads II, III, and aVF with reciprocal ST depression in leads I and aVL. Troponin I is elevated at 2.8 ng/mL. What is the most likely diagnosis?

Explanation

## Clinical Presentation and ECG Correlation **Key Point:** ST-segment elevation in the inferior leads (II, III, aVF) with reciprocal ST depression in the lateral leads (I, aVL) is pathognomonic for inferior wall STEMI. ### Anatomical Basis The inferior wall of the left ventricle is supplied by the right coronary artery (RCA) in approximately 80% of the population. Acute occlusion of the RCA causes: - ST elevation in leads II, III, and aVF - Reciprocal ST depression in leads I and aVL - Possible involvement of the right ventricle (check lead V4R) ### ECG Findings in Inferior STEMI | Feature | Inferior STEMI | Anterior STEMI | |---------|---|---| | **ST elevation leads** | II, III, aVF | V1–V4 (anterior) or V1–V6 (extensive) | | **Reciprocal changes** | I, aVL | None or minimal | | **Coronary artery** | RCA (80%), LCx (20%) | LAD | | **Complications** | RV infarction, bradycardia, AV block | Cardiogenic shock, heart failure | **Clinical Pearl:** Inferior STEMI frequently presents with bradycardia and hypotension due to increased vagal tone and possible RV involvement. Always check lead V4R for right ventricular infarction, which contraindicates nitrates and requires fluid resuscitation. **High-Yield:** The combination of: 1. Acute chest pain radiating to the left arm 2. ST elevation in II, III, aVF 3. Reciprocal ST depression in I, aVL 4. Elevated troponin ...confirms acute inferior wall STEMI requiring emergent reperfusion therapy (primary PCI or thrombolysis). ### Management Algorithm ```mermaid flowchart TD A[Inferior STEMI confirmed]:::outcome --> B{Time since onset?}:::decision B -->|< 12 hours| C[PCI-capable hospital?]:::decision C -->|Yes| D[Primary PCI within 90 min]:::action C -->|No| E[Thrombolysis + transfer]:::action B -->|> 12 hours, stable| F[Medical management]:::action D --> G[Check V4R for RV infarction]:::action G -->|RV involved| H[Fluid resuscitation, avoid nitrates]:::action G -->|RV not involved| I[Standard therapy: aspirin, P2Y12 inhibitor, anticoagulation]:::action ``` **Mnemonic: INFERIOR STEMI = RCA Occlusion** - **I**nferior leads (II, III, aVF) show ST elevation - **N**o ST elevation in anterior leads - **F**requent bradycardia and hypotension - **E**xamine V4R for RV involvement - **R**ight coronary artery is the culprit - **I**mmediately reperfuse (PCI or thrombolysis) - **O**ften complicated by conduction abnormalities - **R**eciprocal ST depression in I, aVL