Large R Waves in V2-3 as STEMI Equivalents

Pathophysiology and ECG Findings

The American College of Cardiology notes that posterior myocardial infarction (PMI) occurs due to occlusion of the left circumflex coronary artery or right coronary artery, affecting the posterior wall of the left ventricle, and in posterior MI, the ECG shows characteristic findings in the anterior precordial leads (V1-V3) that are actually reciprocal changes to what would be ST elevation if leads were placed on the posterior chest wall 2
The American College of Cardiology states that these reciprocal changes include horizontal ST-segment depression in leads V1-V3 3
The American College of Cardiology recommends that dominant R waves (R/S ratio >1) in V2, and abnormally increased R wave amplitude and width (>30 ms) in leads V1 and V2 are indicative of posterior MI 1, 3
The American College of Cardiology notes that upright T waves in anterior leads when they should be inverted are also a characteristic finding in posterior MI 3

The American College of Cardiology recommends that when posterior MI is suspected based on large R waves in V1-V2 and ST depression in V1-V3, additional posterior leads should be recorded, with posterior leads placed at V7, V8, and V9 1, 2, 3
The American College of Cardiology states that diagnostic criteria for posterior MI in these leads is ST-segment elevation ≥0.5 mm in at least one of leads V7-V9 3

The American College of Cardiology notes that right ventricular hypertrophy, right bundle branch block, Wolff-Parkinson-White syndrome, and normal variant in some individuals can cause prominent R waves in V1-V2 1, 3, 4

The American College of Cardiology recommends that when a patient presents with chest pain and shows dominant R waves in V2-V3 with ST depression in V1-V3, posterior leads should be immediately recorded, and if posterior leads show ST elevation ≥0.5 mm, the patient should receive the same emergent reperfusion therapy as traditional STEMI patients 2, 3