Electrocardiographic assessment of posterior cardiac infarction

Abstract

In a consecutive series of one hundred patients with posterior cardiac infarction assessed according to severity of the attack, 22 per cent were slight, 21 per cent moderate, and 57 per cent severe. This was in contrast to anterior cardiac infarction where this incidence was 42.2 per cent, 22.6 per cent, and 35.2 per cent, respectively. Greater gravity in posterior infarction can be explained by the frequency of arrhythmias and by the tendency of some slight posterior infarctions to become severe, a development exceptional in slight anterior infarction. In slight posterior cardiac infarction, the following electrocardiographic patterns were shown: absent pathologic Q waves in more than one-half the cases; R-T and T changes of the subacute type, for example, bowed R-T with isoelectric take-off and deep inversion of T; and electrocardiographic restoration in about one-fourth of the cases. The severe cases, in contrast, exhibited pathologic Q waves in almost every instance; an acute pattern, for example, high R-T take-off and monophasic T wave in the great majority, and arrhthmias were found in more than one-third of the cases. In the moderate group, the incidence of these signs was transitional, except that no arrhythmias were observed. There was no mortality in the slight and moderate group during the first two months. The mortality in the severe group of treated and untreated cases was 33 per cent. The diagnostic difficulties in slight posterior cardiac infarction were solved by effort test, Leads III R and aV FR. Recent bipolar leads advised for posterior infarction proved disappointing. No diagnostic problems have arisen in the moderate and severe cases. The absence of secondary T-wave changes in anterior chest leads proved an important point in the diagnosis of posteroanterior cardiac infarction. In five patients, slight cardiac infarction was followed by increasingly severe angina; two of these developed severe posterior cardiac infarction within a fort-night and one of them died. Early anticoagulant treatment appeared to delay the severe attack by months in one patient, while in the other two it seemed to prevent it. All the five showed electrocardiographic signs suggesting posterior subendocardial infarction, consisting in sagging or flat R-T depression in Leads II, III, and aV F. Effort test caused temporary extension of ischemia and transformed these dubious records into unequivocal ones. This result was considered an important indication for prompt anticoagulant treatment.