A 52-year-old man with a history of hypertension presents to the emergency department with acute onset chest pain radiating to the left arm and diaphoresis. His ECG shows ST elevation in leads II, III, and aVF. His blood pressure is 145/92 mmHg, heart rate 98/min, and respiratory rate 20/min. Troponin I is elevated at 2.8 ng/mL (normal <0.04). What is the most appropriate immediate next step in management?

Explanation

## Clinical Context: Acute ST-Elevation Myocardial Infarction (STEMI) This patient presents with classic features of acute inferior wall STEMI: - ST elevation in inferior leads (II, III, aVF) - Elevated cardiac biomarker (troponin I) - Acute chest pain with diaphoresis - Hemodynamically relatively stable (BP 145/92, HR 98) ## Pathophysiology of the Cardiac Cycle in STEMI **Key Point:** During acute coronary occlusion, the affected myocardial segment loses contractility during systole, leading to dyskinesis. The remaining viable myocardium compensates, but this creates a mismatch in ventricular wall motion and reduces overall cardiac output. Reperfusion must occur as soon as possible to restore normal systolic function and prevent irreversible necrosis. ## Management Algorithm for STEMI ```mermaid flowchart TD A["Acute STEMI diagnosed<br/>ST elevation + elevated troponin"]:::outcome --> B{"PCI-capable<br/>hospital?"}:::decision B -->|Yes| C["Dual antiplatelet therapy<br/>Aspirin 300 mg<br/>P2Y12 inhibitor loading dose"]:::action C --> D["Primary PCI<br/>within 90 minutes"]:::action B -->|No| E["Consider thrombolysis<br/>if <12 hrs from onset<br/>and no contraindications"]:::action E --> F["Transfer for angiography<br/>after thrombolysis"]:::action D --> G["Reperfusion achieved<br/>Restore coronary flow"]:::outcome F --> H{"Reperfusion<br/>successful?"}:::decision H -->|No| I["Rescue PCI"]:::urgent H -->|Yes| J["Continue medical therapy"]:::action ``` ## Rationale for Correct Answer **High-Yield:** The current standard of care for STEMI in a PCI-capable center is **primary percutaneous coronary intervention (PCI) within 90 minutes of first medical contact**. This is superior to thrombolysis in reducing mortality, reinfarction, and stroke. **Clinical Pearl:** Dual antiplatelet therapy (aspirin + P2Y12 inhibitor) must be initiated immediately, even before angiography. This prevents stent thrombosis and improves outcomes. The P2Y12 inhibitor options include: - Clopidogrel 600 mg loading dose - Prasugrel 60 mg loading dose (preferred in acute coronary syndromes) - Ticagrelor 180 mg loading dose (preferred in STEMI) **Key Point:** Time is myocardium. Every minute of delay increases infarct size and mortality. The "door-to-balloon time" should be ≤90 minutes for primary PCI. ## Additional Supportive Measures While arranging PCI: - Anticoagulation with unfractionated heparin or enoxaparin - Beta-blockers (if not contraindicated) - ACE inhibitors - Statins - Oxygen if SpO₂ <90% - Analgesia with morphine [cite:Harrison 21e Ch 297]