Effect of excision of ventricular myocardium on delayed potentials detected by the signal-averaged electrocardiogram in patients with ventricular tachycardia.

The ability of surgical excision of electrically abnormal ventricular myocardium to either abolish delayed potentials or modify their timing was investigated in 21 patients with spontaneous ventricular tachycardia (VT) late after myocardial infarction. This study also examined whether modification of delayed potentials after surgery was associated with loss of ability to induce VT or improvement in left ventricular function. Signal averaging of the electrocardiogram (ECG), programmed stimulation and radionuclide ventriculography were performed preoperatively and were repeated 10 to 14 days postoperatively. At preoperative investigation, all patients had delayed potentials on the signal-averaged ECG and inducible VT at programmed stimulation. In 7 patients (33%), delayed potentials were abolished by surgery, exceeding the baseline variability of 8.5% for detection of delayed potentials. VT was no longer inducible postoperatively in 16 patients (76%), including the 7 in whom delayed potentials were no longer detectable. In the patients in whom VT was no longer inducible, mean ventricular activation time decreased from 178 ms preoperatively to 151 ms postoperatively (standard error of the mean difference = 6 ms, p less than 0.001). In the 5 patients with inducible VT postoperatively, no significant change in mean ventricular activation time was seen, 181 vs 171 ms (standard error of mean difference = 9 ms). Reductions in ventricular activation time were not associated with an improvement in left ventricular ejection fraction unless aneurysmectomy was performed in addition to excision of electrically abnormal myocardium. Thus, the signal-averaged ECG may have a role in assessing the efficacy of antiarrhythmic surgery.(ABSTRACT TRUNCATED AT 250 WORDS)