STEMI: ST-Elevation Myocardial Infarction - Pathophysiology, ECG & Treatment

STEMI = complete thrombotic occlusion of a major coronary artery → transmural myocardial necrosis.

ECG Criteria

• ST elevation ≥1 mm (2 mm in V2-V3 men) in ≥2 contiguous leads
• Reciprocal ST depression often present
• New LBBB (per Sgarbossa criteria)

Pathophysiology

Plaque rupture → thrombus → zero flow → myocyte death wavefront (subendocardial → epicardial) over 3-6 hours.

Reperfusion Therapy (Time = Muscle)

• Primary PCI (Preferred): Door-to-balloon ≤90 min; stent placement
• Fibrinolysis: If PCI >120 min; door-to-needle ≤30 min (tenecteplase, alteplase)

Adjuncts

• Dual antiplatelet (aspirin + P2Y12 inhibitor)
• Anticoagulation (heparin/enoxaparin/bivalirudin)
• High-intensity statin, beta-blocker, ACEi/ARB, SGLT2i

Early reperfusion limits infarct size, preserves LV function, reduces mortality.