A case of myocardial infarction showing extensive precordial ST elevation induced by second diagonal branch occlusion

We observed a case of acute myocardial infarction induced by second diagonal branch occlusion. Electrocardiogram (ECG) on admission showed ST elevation in leads I, aVL and V2-6. Since emergency coronary angiography disclosed complete occlusion of the second diagonal branch, intra-coronary thrombolysis (ICT) was performed, superselectively. Transient coronary reperfusion was obtained, however, reocclusion occurred after several minutes. Rescue percutaneous transluminal coronary angioplasty (PTCA) was then performed immediately and blood flow was improved to TIMI grade 2. During these processes, the ST-segment on the ECG changed in leads I, aVL and V2-6 always corresponding to the blood flow of the second diagonal branch. We have not seen a report hitherto in which occlusion of only the second diagonal branch could be a cause of extensive anterior infarction-like ECG changes. Although the mechanism of ECG changes in this patient cannot be clearly explained by conventional concepts, we report this case because it is considered to be very rare.