The Electrocardiogram in Myocardial Infarction : PART II. ANTERIOR INFARCTION

Abstract

In the previous report, the author describeda generalisation of findings obtained by comparing the electrocardiographic patterns with the postmortem findings of 35 autopsied cases. In this communication, the findings in the unipolar precordial leads and in the standard and goldberger limb leads have been analyzed and correlated with the postmortem findings of 21 cases with anterior infarction in this series of 35 cases. Of 21 cases of anterior infarction, 2 had recently developed and 19 had healed infarctions at autopsy, nut in 9 of the latter group electrocardiograms were taken also during the acute stage. To avoid the errors derived from the difference of extent and location of infarction, the author divided the ventricular wall into the six portions, as shown in the previous communication, each infarction being precisely described according to the pathologic findings; for example, the infarction involved the anterior free wall and the anteroseptal portion of the left ventricle, and the half of the interventricular septum, or the infarction involved the anterior free wall and the lateral wall of the left ventricle etc. The correlation between the pathologic findings and the electrocardiographic patterns was discussed after analysis of these data was made. 1. In 15 cases, the infarctions involved the apical one-third to full length of the anterior free wall and the anteroseptal portion of the left ventricle, and the interventricular septum. In 14 of them, the electrocardiographic pattern showed an abnormal Q wave in one or more of Leads V_1 to V_4. In 9 of these 14 cases, an abnormal QS or QR(S) pattern accompanied by abnormal elevation of the RS-T segment was present in two or more leads of Lead V_1 through V_4. In addition 7 of these 9 cases showed an inversion of T wave at least in one of these leads in which the RS-T segment was found to be elevated abnormally. Another 2 cases of the 14 cases in which abnormal Q waves were noted, had right bundle branch block, characterized by the presence of an abnormal Q wave in place of the customary initial R wave, and the depression of RS-T segment and/or the inversion of T wave. In another 2 cases of them, the amplitude of the initial R wave in Leads V_1, V_2 and V_3 decreased as the electrode was moved from right to left, and finally an abnormal QS or QR complex was recorded in Lead V_4 or V_3. The electrocardiogram of the last case in this group displayed an abnormal elevation of the RS-T segment in Leads V_1, V_E, V_<3R> and V_<4R>, and occasionally displayed a qrS complex in Lead V_2. 2. In one case in which the infarct involved the subepicardial one-fourth to two-thirds of the anterior free wall and the subendocardial two-thirds of the anteroseptal portion of the left ventricle and the left side of the anterior small portion of the inter-ventricular septem, the amplitude of the initial R wave in Leads V_1, V_2 and V_3 showed abnormal decrease as the electrode was moved from right to left, and its QRS pattern was accompanied by the marked elevation of the RS-T segment and a inverted T wave. 3. Interpretation of the abnormal QS or QR pattern in Leads V_1 and V_2 in regards to the differentiation of myocardial infarction from non-infarction cases, was discussed in detail. In myocardial infarction, the abnormal Q wave in Leads V_1 and V_2 is indivative of the infarction of the interventricular septem, not of the infarction of the anterior wall. 4. In 2 cases of the infarction involving the free anterior wall and the anteroseptal portion of the left ventricle, and the interventricular septem, an abnormal qrS complex was recorded in Leads V_1, V_2 and V_3, or in V_2. 5. In an apical infarction, confined to the one-fifth of the anterior free wall and the anteroseptal portion of the left ventricle, and the interventricular septum, abnormal reduction of the initial R wave in Lead V_3 and a biphasic T wace in Lead V_4 were