CAN WE DIFFERENTIATE BY THE ADMISSION ELECTROCARDIOGRAM BETWEEN ANTERIOR WALL ACUTE MYOCARDIAL-INFARCTION DUE TO A LEFT ANTERIOR DESCENDING ARTERY-OCCLUSION PROXIMAL TO THE ORIGIN OF THE FIRST SEPTAL BRANCH AND A POSTSEPTAL OCCLUSION

The objective of this study was to assess the value of ST changes in the various electrocardiographic (ECG) leads in predicting the location of the left anterior descending (LAD) coronary artery obstruction relative to the origin of the first septal branch in patients with anterior wall acute myocardial infarction (AAMI). Patients admitted to the coronary care unit with AAMI who underwent coronary angiography within 31 days of hospitalization were evaluated. The admission 12-lead ECG was evaluated for ST segment amplitudes in every lead at 0.08 s after the J point. The coronary angiogram was evaluated for the site and severity of luminal narrowing of the coronary arteries. The site of the culprit lesion in the LAD artery was determined relative to the origin of the first septal branch. A total of 111 consecutive patients were included. In 4 patients no lesion was identified in the LAD artery. Of the remaining 107 patients, 38 had a LAD lesion proximal to the origin of the first septal branch. No statistically significant differences were observed in ST amplitude in the precordial and lateral leads between the two groups. The magnitude of ST depression in the inferior leads is higher in patients with a preseptal lesion than in patients with a distal lesion (-1.05 +/- 0.87 vs. -0.20 +/- 0.82 mm, -1.61 +/- 1.28 vs. -0.44 +/- 0.96 mm, and -1.47 +/- 1.13 vs. -0.33 +/- 0.83 mm, for leads II, III and aVF, respectively, p < 0.0001). An ST depression of more than 1 mm in leads II, III and aVF has a predictive value for a preseptal lesion of 62% (p < 0.000005), 67% (p < 0.000004), and 74% (p < 0.000001), respectively, while most of the patients without ST depression in the inferior leads have a distal LAD artery lesion (82, 86 and 87% in leads II, III and aVF, respectively). ST elevation in the anteroseptal leads (V1 and V2) in the admission ECG does not differentiate between patients with an LAD artery occlusion proximal and distal to the origin of the first septal branch. The finding of isoelectric ST or ST elevation in the inferior leads is suggestive of a distal occlusive lesion in the LAD artery.