The ECG in ACS — the territory, the mimics and the equivalents

Territories: Inferior (II, III, aVF — the RCA or the circumflex; check V4R for the RV infarct). Anterior (V1-V4 — the LAD). Lateral (I, aVL, V5-V6 — the circumflex). Posterior (the ST depression V1-V3 with the tall R waves — confirm with V7-V9). The right ventricular infarct (V4R ST elevation — in up to half of inferior LVMIs (Kinch); the RV is volume-dependent — avoid vasodilators and diuretics (Goldstein)). STEMI equivalents: LBBB: apply Sgarbossa (concordant STE ≥1 mm; concordant STD ≥1 mm in V1–V3; discordant STE ≥5 mm). Smith-modified replaces 5 mm with ST/S ≤ −0.25. New LBBB alone is not a STEMI equivalent. The isolated posterior MI (the ST depression V1-V3 with the posterior lead elevation). The hyperacute T waves (the early sign, before the ST elevation develops). Mimics: The early repolarisation (the diffuse ST elevation with the concave morphology, the J-point elevation, the T-wave inversion in the lead aVR, the most in V4), the pericarditis (the diffuse ST elevation, the PR depression, the PR elevation in aVR), the Brugada (the coved ST elevation V1-V3, the RBBB pattern), the LVH (the strain pattern, the voltage criteria), the hyperkalaemia (the peaked T waves, the wide QRS), the pacing (the paced rhythm obscures the ST analysis). The key: the STEMI produces the regional ST elevation (the territory), the convex ST elevation, and the reciprocal ST depression. The mimics produce the diffuse ST elevation, the concave ST elevation, and the absence of the reciprocal changes.