CAN WE DIFFERENTIATE BY THE ADMISSION ELECTROCARDIOGRAM BETWEEN ANTERIOR WALL ACUTE MYOCARDIAL-INFARCTION DUE TO A LEFT ANTERIOR DESCENDINGARTERY-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 t he various electrocardiographic (ECG) leads in predicting the location of the left anterior descending (LAD) coronary artery obstruction rel ative to the origin of the first septal branch in patients with anteri or wall acute myocardial infarction (AAMI). Patients admitted to the c oronary care unit with AAMI who underwent coronary angiography within 31 days of hospitalization were evaluated. The admission 12-lead ECG w as evaluated for ST segment amplitudes in every lead at 0.08 s after t he J point. The coronary angiogram was evaluated for the site and seve rity of luminal narrowing of the coronary arteries. The site of the cu lprit lesion in the LAD artery was determined relative to the origin o f the first septal branch. A total of 111 consecutive patients were in cluded. In 4 patients no lesion was identified in the LAD artery. Of t he remaining 107 patients, 38 had a LAD lesion proximal to the origin of the first septal branch. No statistically significant differences w ere observed in ST amplitude in the precordial and lateral leads betwe en the two groups. The magnitude of ST depression in the inferior lead s 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 l eads II, III and aVF, respectively, p < 0.0001). An ST depression of m ore than 1 mm in leads II, III and aVF has a predictive value for a pr eseptal lesion of 62% (p < 0.000005), 67% (p < 0.000004), and 74% (p < 0.000001), respectively, while most of the patients without ST depres sion 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 ante roseptal 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 o r ST elevation in the inferior leads is suggestive of a distal occlusi ve lesion in the LAD artery.