In the absence of right ventricular hypertrophy or bundle-branch block, a prominent R wave in V1 or V2 is considered to reflect a lateral myocardial infarction. We investigated the differences in infarct location and size between patients with prominent R wave in V1 and those with prominent R wave in V2.

We studied 50 patients with a previous first infarction involving left ventricular inferior and/or lateral wall at myocardial scintigraphy

A prominent R wave in V1 was present in 8 patients (16%), in V2 in 23 (46%). At myocardial scintigraphy, the infarction involved the inferior wall in 11 patients (22%), the lateral wall in 6 (12%), and both walls in 33 patients (66%). The sensitivity of a prominent R wave in V1 in detecting a lateral infarction was low (17.9%), while the specificity was high (90.9%). The sensitivity and specificity of a prominent R wave in V2 were 46.2% and 54.5%, respectively. In patients with a prominent R wave in V1, infarct size and lateral extent were greater than in patients without this pattern (P<0.005 and<0.01 respectively). In patients with a prominent R wave in V2, infarct size, lateral extent were not different from patients without this pattern.

Only a prominent R wave in V1 is a specific sign of large lateral infarction.