Signal-averaged isoharmonic body surface maps of patients with ischemic cardiomyopathy

Signal-Averaged Body Surface Maps. Introduction: Prevention of sudden arrhy thmic cardiac death depends on accurate identification of individuals at hi gh risk. Previous studies of signals recorded directly from arrhythmogenic tissue suggested that the predictive value of the signal-averaged ECG could be enhanced by expanded temporal, spectral, and spatial analysis. Accordin gly, we performed a prospective study of 192-lead signal-averaged body surf ace maps from 43 patients with ischemic cardiomyopathy referred for electro physiologic study. Three groups were included: 15 patients with clinical ve ntricular tachycardia (VT), 12 patients with inducible VT, and 16 patients with non-VT. Methods and Results: The patients were well matched with regard to age, gen der, infarct location, ejection fraction (28% +/- 9%), QRS duration, and in cidence of nonsustained VT (96%). Isoharmonic maps of the entire cardiac cy cle were constructed for each patient. The peaks of the 1-7 Hz isoharmonic maps distinguished patients with clinical VT from non-VT and inducible VT p atients (1,152 +/- 273, 852 +/- 283, and 808 +/- 272, respectively; P = 0.0 03). After prospective observation for 22 +/- 16 months, the combined endpo int of spontaneous sustained VT, ventricular fibrillation, appropriate defi brillator therapy, and death was predicted by inducibility of VT (relative risk 3.8, P = 0.008) and by the signal-averaged isoharmonic body surface ma p (relative risk 3.1, P = 0.02), Conclusion: These results confirm the diagnostic utility of signal-averaged isoharmonic body surface maps in a rigorously defined patient population.