STEMI - ST elevation in contiguous leads localized to the infarct territory (anterior, inferior, lateral). The two real ECG images above show anterior and anterolateral STEMI patterns from actual patient cases.

NSTEMI/Unstable Angina - ST depression, T inversions, or a normal ECG. The third ECG shows STE in aVR + widespread depression indicating left main disease.

Atrial Fibrillation - Absent P waves + irregularly irregular RR intervals. Risk of stroke is 5x baseline; CHA₂DS₂-VASc guides anticoagulation.

Heart Failure - ECG shows LVH, LBBB, or low voltage; LBBB with QRS ≥150 ms triggers consideration for CRT.

Dilated Cardiomyopathy - LBBB, AF, PVCs, poor R-wave progression. EF typically <25% at end stage; titin mutations are the most common genetic cause.

Hypertrophic Cardiomyopathy - Deep narrow septal Q waves in lateral/inferior leads, LVH voltage, giant T inversions in apical variant. Leading cause of sudden death in young athletes.

ARVC - The epsilon wave (small post-QRS deflection in V1-V3) is pathognomonic. VT has LBBB morphology (right ventricular origin).

Ventricular Fibrillation - Completely chaotic tracing, no QRS. Torsades de Pointes is the polymorphic VT variant associated with long QT (drug-induced or congenital).

WPW Syndrome - Short PR + delta wave + wide QRS. Never give verapamil or digoxin. Ablation is curative.

Aortic Stenosis - LVH with lateral strain pattern (ST depression + T inversions in V4-V6) is the hallmark ECG finding. The clinical triad of angina, syncope, and dyspnea marks progressive severity.