A 58-year-old man presents to the emergency department with acute chest pain radiating to the left arm for 2 hours. His ECG shows ST elevation in leads II, III, and aVF. Serial troponin I measured at 0 and 3 hours are both negative. Which investigation is most appropriate to confirm acute myocardial infarction at this stage?

## Investigation of Choice for Acute STEMI Confirmation ### Clinical Context The patient has: - Acute chest pain with classic radiation - ECG evidence of ST elevation (diagnostic of STEMI) - Negative troponin at 0 and 3 hours (early presentation, before troponin rise) ### Why Coronary Angiography is Correct **Key Point:** In acute STEMI with ECG changes, coronary angiography is the investigation of choice because it: 1. Provides definitive diagnosis of coronary occlusion 2. Enables immediate therapeutic intervention (primary PCI) 3. Identifies the culprit vessel and extent of disease 4. Does not delay reperfusion therapy **High-Yield:** STEMI diagnosis is based on **clinical presentation + ECG changes**, NOT on troponin levels. Troponin elevation confirms myocardial necrosis but is not required to initiate reperfusion therapy. ### Why Other Options Are Suboptimal | Investigation | Limitation in Acute STEMI | | --- | --- | | Repeat troponin at 6 hrs | Delays definitive diagnosis and reperfusion; troponin rises 3–4 hrs after symptom onset but is a marker, not a diagnostic requirement | | Cardiac MRI with gadolinium | Excellent for characterizing infarction but time-consuming; contraindicated in acute unstable patients; not used for acute diagnosis | | Myocardial perfusion imaging | Useful for risk stratification post-MI, not for acute diagnosis; requires stable patient; delays reperfusion | **Clinical Pearl:** The "golden window" for reperfusion in STEMI is within 12 hours of symptom onset (ideally <90 minutes for PCI). Coronary angiography with PCI is the standard of care and should not be delayed by waiting for biomarker results. ### Diagnostic Algorithm ```mermaid flowchart TD A[Acute chest pain + ST elevation on ECG]:::outcome --> B{STEMI diagnosis made?}:::decision B -->|Yes| C[Coronary angiography + PCI]:::action B -->|No| D[Risk stratify with troponin/other markers]:::action C --> E[Reperfusion achieved]:::outcome D --> F[Serial troponin, further imaging]:::action ```