Does left anterior descending coronary artery acute occlusion proximal to the first septal perforator counteract ST elevation in leads V5 and V6?

The mechanisms of the so-called extensive anterior acute myocardial infarction including ST-segment elevation in leads V(1) (ST upward arrow(V1)) through V(6) (ST upward arrow(V6)) are not clear. This report is focused on the electrocardiographic (ECG) changes in 2 cases with anterior AMI. In case 1, the ECG showed complete right bundle-branch block, left anterior fascicular block, and ST upward arrow(V2) through ST upward arrow(V6) on admission, but 5 minutes later, after the disappearance of complete right bundle-branch block and left anterior fascicular block, a striking ST depression in V6 (ST downward arrow(V6)) and ST upward arrow(V1) occurred. In case 2, the ECG showed ST upward arrow(V1) through ST upward arrow(V6). The physiopathologic mechanisms of these ECG findings are discussed.