A 58-year-old man with hypertension presents to the emergency department with acute onset substernal chest pain radiating to the left arm for 2 hours. His blood pressure is 145/92 mmHg, heart rate 98/min. On examination, he has an S4 gallop. A 12-lead ECG shows ST elevation in leads II, III, and aVF with reciprocal ST depression in I and aVL. Which investigation is most appropriate to confirm acute myocardial infarction and guide immediate reperfusion therapy?

Question

Accepted Answer

A. Coronary angiography. ## Diagnosis and Management of STEMI ### Clinical Context This patient presents with classic acute STEMI features: - Acute chest pain with typical radiation - ST elevation in inferior leads (II, III, aVF) → **inferior wall STEMI** - Reciprocal changes in lateral leads - Hemodynamic signs of acute MI (S4 gallop suggests ventricular dysfunction) ### Investigation of Choice: Coronary Angiography **Key Point:** In a patient with ECG-confirmed STEMI (ST elevation ≥1 mm in two contiguous leads), coronary angiography is the **gold standard** and **definitive diagnostic and therapeutic procedure**. It is both diagnostic AND therapeutic. ### Why Coronary Angiography? 1. **Diagnostic confirmation:** Visualizes the culprit coronary artery and identifies the exact site of occlusion 2. **Therapeutic intervention:** Enables immediate primary percutaneous coronary intervention (PCI) — the preferred reperfusion strategy in STEMI 3. **Risk stratification:** Identifies extent of disease, collaterals, and complications (mechanical) 4. **Time-sensitive:** Should be performed within 90 minutes of first medical contact (door-to-balloon time) ### Role of Other Investigations | Investigation | Role in STEMI | Timing | |---|---|---| | **Troponin (cTnI/cTnT)** | Confirms myocardial necrosis; rises after 3–4 hours | Supportive, not for diagnosis | | **Chest X-ray** | Assesses pulmonary edema, cardiomegaly, complications | Adjunctive; does NOT guide therapy | | **Echocardiography** | Evaluates wall motion abnormalities, complications (VSD, papillary muscle rupture) | Post-PCI or if complications suspected | | **Coronary angiography** | **Gold standard:** identifies culprit vessel, enables PCI | **Immediate** (within 90 min) | ### High-Yield: STEMI Diagnosis Algorithm ```mermaid flowchart TD A[Acute chest pain + ECG changes]:::outcome --> B{ST elevation ≥1 mm
in 2 contiguous leads?}:::decision B -->|Yes| C[STEMI diagnosed]:::outcome C --> D{PCI-capable
hospital?}:::decision D -->|Yes| E[Coronary angiography
+ Primary PCI
within 90 min]:::action D -->|No| F[Thrombolysis
+ Transfer for angiography]:::action E --> G[Reperfusion achieved]:::outcome B -->|No| H[NSTEMI or unstable angina
Risk stratify]:::outcome ``` **Clinical Pearl:** Do NOT delay coronary angiography while awaiting troponin results. ECG + clinical presentation are sufficient to diagnose STEMI and proceed to the catheterization laboratory. Troponin is confirmatory but not required for immediate decision-making. **Warning:** Chest X-ray and echocardiography are NOT diagnostic for acute MI and should NOT delay transfer to the catheterization laboratory. They are adjunctive investigations performed after reperfusion therapy. [cite:Harrison 21e Ch 297] ![STEMI Diagnosis and Management diagram](https://mmcphlazjonnzmdysowq.supabase.co/storage/v1/object/public/blog-images/explanation/3591.webp)

Answer

B. Echocardiography

Answer

C. Cardiac troponin I (cTnI) or high-sensitivity troponin

Answer

D. Chest X-ray

Explanation

Diagnosis and Management of STEMI

Clinical Context

Investigation of Choice: Coronary Angiography

Why Coronary Angiography?

Role of Other Investigations

High-Yield: STEMI Diagnosis Algorithm

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Investigation	Role in STEMI	Timing
Troponin (cTnI/cTnT)	Confirms myocardial necrosis; rises after 3–4 hours	Supportive, not for diagnosis
Chest X-ray	Assesses pulmonary edema, cardiomegaly, complications	Adjunctive; does NOT guide therapy
Echocardiography	Evaluates wall motion abnormalities, complications (VSD, papillary muscle rupture)	Post-PCI or if complications suspected
Coronary angiography	Gold standard: identifies culprit vessel, enables PCI	Immediate (within 90 min)