A 58-year-old man with hypertension presents to the emergency department with acute onset chest pain radiating to the left arm. His blood pressure is 165/95 mmHg and heart rate is 92/min. A 12-lead ECG shows ST-segment elevation in leads II, III, and aVF with reciprocal ST-segment depression in leads I and aVL. Which investigation is most appropriate to confirm the diagnosis and guide immediate management?

Explanation

## Investigation of Choice for Acute ST-Elevation MI (STEMI) ### Clinical Context The patient presents with classic features of acute inferior wall STEMI: - Acute chest pain with typical radiation - Hemodynamic instability (elevated BP, tachycardia) - Diagnostic ECG changes: ST elevation in inferior leads (II, III, aVF) with reciprocal changes ### Why Coronary Angiography is the Answer **Key Point:** Coronary angiography is the gold standard investigation AND the definitive therapeutic intervention for acute STEMI. It serves dual purposes: diagnostic confirmation and immediate revascularization (primary PCI). **High-Yield:** In a patient with STEMI, the goal is **reperfusion within 90 minutes of first medical contact**. Coronary angiography with primary percutaneous coronary intervention (PCI) is the preferred reperfusion strategy when performed at a PCI-capable center. ### Diagnostic Hierarchy in Acute MI | Investigation | Role | Timing | Limitation | |---|---|---|---| | **12-lead ECG** | Initial diagnostic tool; identifies location & type of MI | Immediate | May be normal in early stages; not therapeutic | | **Cardiac biomarkers** (Troponin) | Confirms myocardial necrosis; prognostic value | Serial (0, 3, 6 hrs) | Delayed rise; not used to delay reperfusion | | **Coronary angiography** | Gold standard; identifies culprit vessel; enables PCI | Urgent (door-to-balloon <90 min) | Invasive; requires expertise | | **Echocardiography** | Assesses wall motion, ejection fraction, complications | After stabilization | Not diagnostic for acute MI; delayed | | **Chest X-ray** | Rules out alternative diagnoses (pneumothorax, aortic dissection) | Initial | Non-specific for MI | ### Management Algorithm for STEMI ```mermaid flowchart TD A["Acute Chest Pain + ST Elevation on ECG"]:::outcome --> B{"PCI-capable hospital?"}:::decision B -->|"Yes"| C["Activate cath lab"]:::action B -->|"No"| D["Administer fibrinolytic + Aspirin + P2Y12 inhibitor"]:::action C --> E["Coronary angiography + Primary PCI"]:::action D --> F["Transfer for rescue PCI if failed fibrinolysis"]:::action E --> G["Reperfusion achieved"]:::outcome F --> G ``` **Clinical Pearl:** Troponin elevation confirms myocardial injury but does NOT change acute management. Waiting for troponin results delays life-saving reperfusion. In STEMI, the ECG diagnosis is sufficient to proceed to angiography. **Mnemonic for STEMI Reperfusion:** **DOOR-TO-BALLOON** = <90 minutes is the target for primary PCI. Coronary angiography is the pathway to achieve this. ### Why Other Options Are Incorrect - **Troponin & serial ECGs:** Useful for confirming MI and risk stratification, but they do NOT guide acute reperfusion therapy. Waiting for troponin results is contraindicated in STEMI. - **Echocardiography:** Valuable for assessing complications (wall motion abnormality, cardiogenic shock, mechanical complications) but is NOT diagnostic for acute MI and should not delay angiography. - **Chest X-ray:** May identify alternative diagnoses but is NOT diagnostic for MI and does not guide acute management. [cite:Harrison 21e Ch 297]