Inferior-septal myocardial infarction misdiagnosed as anterior-septal myocardial infarction: electrocardiographic, scintigraphic, and angiographic correlations.

Objective: To explore the infarct sites in patients with inferior wall acute myocardial infarction (AMI) concomitant with ST segment elevation in leads V1-V3 and leads V3R-V5R.
Methods: Five patients diagnosed as inferior, right ventricular, and anteroseptal walls AMI at admission were enrolled. Electrocardiographic data and results of isotope 99mTc-methoxyisobutylisonitrile (MIBI) myocardial perfusion imaging and coronary angiography (CAG) were analyzed.
Results: Electrocardiogram showed that ST segment significantly elevated in standard leads II, III, aVF, and leads V1-V3, V3R-V5R in all five patients. The magnitude of ST segment elevation was maximal in lead V1 and decreased gradually from lead V1 to V3 and from lead V1 to V3R-V5R. There was isotope 99mTc-MIBI myocardial perfusion imaging defect in inferior and basal inferior-septal walls. CAG showed that right coronary artery was infarct-related artery.
Conclusions: The diagnostic criteria for basal inferior-septal wall AMI can be formulated as follows: (1) ST segment elevates > or = 2 mm in lead V1 in the clinical setting of inferior wall AMI; (2) the magnitude of ST segment elevation is the tallest in lead V1 and decreases gradually from lead V1 to V3 and from lead V1 to V3R-V5R. With two conditions above, the basal inferior-septal wall AMI should be diagnosed.