Body surface late potentials: effects of endocardial resection in patients with ventricular tachycardia.

We studied 37 patients undergoing endocardial resection for medically refractory ventricular tachycardia (VT). Each was studied before and after surgery by programmed ventricular stimulation and signal-averaged electrocardiography. Low-amplitude late potentials were identified preoperatively in 76% of patients. In the 24 patients without postoperative VT the effect of surgery was to shorten the filtered QRS duration (137 +/- 27 to 121 +/- 26 msec; p = .003), increase the voltage in the last 40 msec of the filtered QRS (16.5 +/- 16.1 to 39.0 +/- 29.4 microV; p = .003), and decrease the incidence of late potentials (71% to 33%; p = .03). The filtered QRS complex was unchanged in 13 patients whose VT persisted after surgery. No preoperative variable predicted which patients would not have inducible VT after surgery. However, loss of a late potential after surgery in nine of 10 patients was associated with absence of inducible VT (p less than .02). Loss of a late potential was not necessary for surgical success. Eight of 18 patients with a persistent late potential did not have inducible VT. The signal-averaged electrocardiogram predicted a successful outcome after endocardial resection if the late potential was no longer present.