Body surface electrocardiographic mapping in inferior myocardial infarction. Manifestation of left and right ventricular involvement

Abstract

To determine the depolarization and repolarization time-integral patterns in patients with first acute inferior myocardial infarction, we acquired body surface potential maps in 28 men and eight women, ages 36-76 years, a mean of 76 hours after the onset of symptoms. Based on technetium-99m pyrophosphate myocardial scans, patients were divided into two groups. Group I included 22 patients with scintigraphic activity limited to the left ventricle who were considered to have exclusive left ventricular infarction, and group 2 included 14 patients with scintigraphic activity involving the right ventricle in addition to the left ventricle, considered to have both left and right ventricular infarction. Isointegral plots of the first 50% of the QRS complex (Q zone) were characterized by negative areas over the inferior torso with concomitant extension of positive areas to the superior precordium. Group 2 patients had greater leftward and superior extention of the negative inferior distributions than group 1 patients. Subtraction of the mean Q-zone map of group 1 patients from that of group 2 patients confirmed a mean area of difference over the right anterior-inferior torso. The average Q-zone integral value within this area of difference was 5.9 ± 7.2 μV.sec (±SD) for group 1 patients compared with 1.7 ± 5.2 μV.sec for group 2 patients (p<0.05). ST-segment isointegral maps revealed positive inferior distributions in all subjects; however, 29 patients also had abnormal negative ST-segment distributions over the precordium. The area of negative precordial values in group 2 patients extended further rightward and inferiorly compared with group 1 patients. There were two large areas of difference seen on subtraction: one over the precordium, in which the mean ST-segment integral value for group 1 patients was -0.6 ± 3.8 μV.sec, compared with -3.2 ± 3.2 μV.sec for group 2 patients (p<0.025), and another over the inferior torso, where the mean value for group 1 was 1.2 ± 1.6 μV.sec, compared with 3.3 ± 3.5 μV.sec for group 2 (p<0.05). Thus, in acute inferior infarction, there is a characteristic distribution of negative Q-zone and positive ST-segment time integrals over the inferior torso and a reciprocal development of positive Q-zone and negative STsegment integrals over the anterior-superior torso. Patients with right ventricular involvement, however, have spatial and quantitative abnormalities of both depolarization and repolarization that distinguish them from patients with infarction limited to the left ventricle.