Prevalence and severity of circumflex coronary artery disease in electrocardiographic posterior myocardial infarction.

To determine the coronary anatomy responsible for electrocardiographic posterior myocardial infarction, the prevalence and severity of disease in the right coronary and left circumflex coronary arteries were compared in 21 patients with electrocardiographic posterior infarction (17 of whom had associated inferior infarction) and 23 patients with isolated electrocardiographic inferior infarction. Significant circumflex coronary artery disease (greater than or equal to 75% stenosis) was more prevalent in patients with posterior or inferoposterior infarction (17 of 21) than in those with isolated inferior infarction (11 of 23) (p less than 0.02). Significant right coronary artery disease was less prevalent in patients with posterior or inferoposterior infarction (16 of 21) than in those with isolated inferior infarction (23 of 23) (p less than 0.05). Among the 21 patients with posterior or inferoposterior infarction, disease was more severe in the circumflex coronary artery in 10 and the right coronary artery in 5 and was of equal severity in 6. Among the 23 patients with isolated inferior infarction, the more diseased artery was the right coronary artery in 21 and the circumflex artery in 2 (p less than 0.001 by chi-square analysis). Variant patterns of coronary artery dominance accounted for only 4 of the 17 patients with inferoposterior infarction. These data suggest that the likely substratum for electrocardiographic posterior or inferoposterior infarction is severe circumflex coronary artery disease, usually in association with significant right coronary artery disease. The pattern of tall, wide R waves in leads V1 or V2 (RV1,2) in patients with inferior infarction is highly predictive of at least two vessel coronary artery disease.