How do you differentiate STEMI from NSTEMI on a 12-lead ECG?

1 Answer

Key ECG Differences Between STEMI and NSTEMI: STEMI: - ST elevation ≥1 mm in ≥2 contiguous limb leads OR ≥2 mm in ≥2 contiguous precordial leads - New LBBB can be STEMI-equivalent - Posterior STEMI: ST depression in V1-V3 + tall R waves (mirror image) - Hyperacute T waves (earliest sign) - Evolves to Q waves and T wave inversion NSTEMI/UACS: - ST depression ≥0.5-1 mm (horizontal or downsloping) - T wave inversion without ST elevation - Normal ECG does NOT rule out NSTEMI (need serial troponins) - No significant Q wave formation Clinical Decision: - STEMI: Activate cath lab IMMEDIATELY (door-to-balloon <90 min) - NSTEMI: Start anticoagulation, antiplatelets; risk-stratify with TIMI/GRACE score - High-risk NSTEMI (ongoing ischemia, hemodynamic instability): early invasive strategy within 2 hours Remember: Wellens syndrome (biphasic/deep T inversions V2-V3) indicates critical LAD stenosis and requires urgent cath even without ST elevation.