Is it possible to rule out extensive anterior myocardial infarction in the absence of abnormal Q waves in lead I and aVL? Effect of infero-apical extension of infarction over apex.

To determine whether abnormal Q wave in lead I or aVL may be of use to estimate the size of an extensive anterior myocardial infarction, electrocardiographic and left ventriculographic findings were analyzed in 45 patients with old extensive anterior infarction. All 45 patients had a significant narrowing in the proximal segment of left anterior descending coronary artery (LAD) and severe asynergy in anterolateral segment. The patients were divided into two groups; Group I consisted of 35 cases with less involvement of the inferoapical segment and Group II of 10 cases with remarkable extension of the anterolateral infarction into the inferoapical segment due to occlusion of very long LAD supplying the anterior half of posterior interventricular groove. There were no statistical differences in the extent of anterolateral asynergy, number of abnormal Q waves in precordial leads and left ventricular ejection fraction between the two groups. While abnormal Q wave in lead I or aVL was present in 28 cases (80%) of Group I, it was observed in only 3 cases (30%) of Group II (p less than 0.01). Thus, we can't rule out extensive anterior myocardial infarction even if abnormal Q waves are absent in lead I or aVL, in which abnormal Q waves may be cancelled by loss of electromotive force of inferoapical segment due to extension of the anterior infarction over the apex in cases with extraordinarily long LAD.