THERAPY AND PREVENTION VENTRICULAR TACHYCARDIA 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 guV; 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 < .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. Circulation 70, No. 4, 632-637, 1984. THERE IS substantial evidence that ventricular tachycardia (VT), particularly when associated with coronary artery disease, involves reentrant mechanisms. '1 Reentry requires unidirectional block and conduction delay sufficient to give the previously refractory tissue time to recover excitability. Several workers have directly recorded delayed ventricular activation in humans and animals with VT, which is believed to be the substrate of the arrhythmia.i' Signal-averaging techniques have been used to detect low-level activity at the end of the QRS complex from the body surface in patients with VT.9 '3 By endocardial and epicardial mapping techniques, it has been demonstrated that these signals, called "late potentials," correspond to areas of slow or delayed activation in the ventricular myocardium.9'4 ' Late potentials appear to be sensiFrom the Clinical Electrophysiology Laboratory, Hospital of the University of Pennsylvania, Cardiovascular Section, and Cardiothoracic Surgery Section, Departments of Medicine and Surgery, University of Pennsylvania School of Medicine, Philadelphia. Supported in part by grants HL 24278, HL 27925, and HL 22315 from the NHLBI; grants from the American Heart Association, Southeastern Pennsylvania Chapter, Philadelphia; The Fannie E. Ripple Foundation, Morristown, NJ; and Arrhythmia Research Technology. Address for correspondence: Michael B. Simson, M.D., Gates 945, Cardiovascular Section, Hospital of the University of Pennsylvania, 3400 Spruce St., Philadelphia, PA 19104. Received May 27, 1983; revision accepted May 24, 1984. Dr. Simson is the Samuel Bellet Associate Professor of Medicine in Cardiology. 632 tive and specific for identifying patients with recurrent sustained VT.'0o 12. 13 Endocardial resection performed in association with left ventricular aneurysmectomy and guided by activation mapping during VT has been successful in controlling medically refractory VT associated with coronary artery disease. 16, 1' The methods for evaluating the effectiveness of endocardial resection include Holter monitoring and invasive catheter electrophysiologic testing. This study was undertaken to analyze changes in body surface late potentials after surgery that is known to successfully control VT and to ascertain whether this noninvasive marker could predict postoperative control of VT by endocardial resection.