Electrocardiographic tall R waves in the right precordial leads: vectorcardiographic and electrocardiographic distinction of posterior myocardial infarction from prominent anterior forces in normal subjects.

Electrocardiographic tall R waves in the right precordial leads may be present in patients with posterior wall myocardial infarction, right ventricular hypertrophy, various conduction disturbances, some forms of cardiomyopathy, and in clinically otherwise normal subjects with prominent anterior forces. Since clinical uncertainty most often arises in distinguishing possible prior posterior myocardial infarction from the unusual normal variant, we compared VCGs and ECGs in 19 subjects with posterior infarction with tracings from 11 subjects with no evidence of cardiac disease who had prominent anterior forces on routine examination. By VCG, the infarction group was characterized by smaller maximum posterior voltage in the horizontal plane, more anteriorly oriented T loop direction, more prolonged anterior QRS forces, more leftward frontal plane QRS maximum vector, and associated evidence of diaphragmatic infarction. By standard ECG, the infarction group was characterized by isoelectric or upright T waves in precordial lead V1, a more leftward frontal plane axis, and associated diaphragmatic infarction. Criteria for distinguishing between posterior wall myocardial infarction and prominent anterior forces in otherwise clinically normal subjects are suggested. These require prospective validation in an independent test population.