Vulnerability to ventricular arrhythmia: Assessment by mapping of body surface potential

It is now well established that the vulnerability of the ventricular myocardium to repetitive dysrhythm increases in the presence of greater than normal disparity of local recovery times. Local recovery is reflected in the electrocardiographic waveform as an area of the venticular deflection (QRST time integral), and thus disparate ventricular recovery may be manifested in the body surface distribution of this quality. To assess this possibility, we obtained simultaneous 120-lead electrocardiograms from both the anterior and posterior torso in 140 subjects (ages 8 to 75) grouped as follows: group A, 97 normal subjects; group B, 16 patients resuscitated from ventricular fibrillation or sustained ventricular tachycardia; and group C, 27 patients 6 to 12 months after myocardial infarction but without clinically significant arrhythmia. In each subject, the QRST integral was evaluated for each lead and isointegral contour maps were plotted. A score was assigned to each map, based on the number of extrema; each maximum or minimum scored one point, with the exception of simultaneously occurring anterior and posterior minima in the right shoulder (frequently occurring in normal subjects), which scored together only one point. All but one group A subject had dipolar QRST integral maps (mean ± SD score 2.11 ± 0.2). Conversely, 10 of 16 (62.5%) group B patients had scores of 3 or more (mean 3.16 ± 1.08; p<<.01 vs group A). Group C patients had intermediate values, with eight of 27 (29.6%) scoring 3 or more (mean 2.46 ± 83); this was less than in group B (p<.01), but more (p<.05) than in group A. Thus, patients with repetitive ventricular arrhythmia tend to have multipolar distributions on QRST integral maps, possibly refecting dispersion of underlying properties of ventricular recovery. These results suggest that body surface potential mapping may provide a noninvasive means to detect substrate for life-threatening arrhythmias.