DIAGNOSTIC METHODS VENTRICULAR TACHYCARDIA Intraoperative endocardial mapping during sinus rhythm: relationship to site of origin of ventricular tachycardia

Mapping-guided endocardial resection has proved to be an effective therapy for recurrent sustained ventricular tachycardia. However, some patients cannot be mapped during ventricular tachycardia, so that guidance from findings during normal sinus rhythm would be highly desirable. We examined the frequency, timing, and duration of several abnormal types of electrograms recorded endocardially during sinus rhythm and related these findings to activation mapping during sustained ventricular tachycardia. Thirteen patients with extensive myocardial infarction complicated by recurrent sustained ventricular tachycardia were studied intraoperatively during sinus rhythm and induced ventricular tachycardia with a standardized mapping scheme involving the entire endocardial surface. Fractionated electrograms (multicomponent with amplitude <1 mV and duration >50 msec) were recorded in all patients. This type of electrogram could be recorded at up to 36% of mapped sites. Split electrograms (two components separated by isoelectric period) were also frequently seen but involved only a mean of 5.8% of mapped sites. Late electrograms (inscribed entirely after the QRS complex) were only recorded in four of 13 patients at a mean of 5% of mapped sites. The location of these electrograms was related to an arbitrary 8 cm2 zone around the earliest site of endocardial activation recorded during ventricular tachycardia. The longest fractionated electrogram was closely related to nine of 22 morphologies of induced ventricular tachycardia, split electrograms were related to seven of 16 morphologies, and late clectrograms to two of four morphologies. We have concluded that extremely abnormal electrograms recorded endocardially during sinus rhythm are widespread in patients with extensive myocardial infarction complicated by ventricular tachycardia. These electrograms may be associated with, but are not specific for, sites of origin of ventricular tachycardia. Surgical procedures based on sinus rhythm mapping of these electrogram types would likely result in more extensive surgical excision than those guided by endocardial activation during ventricular tachycardia. Circulation 70, No. 6, 957-965, 1984. PREOPERATIVE and intraoperative mapping of endocardial activation of ventricular tachycardia has been used to guide subendocardial resection in patients with refractory ventricular tachycardia.' In some patients, however, tachycardias cannot be mapped as a result of such factors as cycle length of tachycardia, hemodynamic embarrassment, changing morphology From the Clinical Electrophysiology Laboratory, Cardiovascular Section, Department of Medicine, and the Cardiothoracic Surgery Section, Department of Surgery, Hospital of the University of Pennsylvania, Philadelphia. Supported in part by grants from the American Heart Association, Southeastern Pennsylvania Chapter, Philadelphia, grant Nos. HL00361 and HL24278 from the National Heart, Lung, and Blood Institute, Bethesda, and a grant from the Fannie E. Ripple Foundation, Morristown, NJ. Address for correspondence: Mark E. Josephson, M.D., Cardiovascular Section, 658 Ravdin Bldg., Hospital of the University of Pennsylvania, 3400 Spruce St., Philadelphia, PA 19104. Received June 4, 1984; revision accepted Aug. 13, 1984. of tachycardia, or failure to induce tachycardia. Fractionated and other abnormal electrograms recorded from the endocardium have been noted in patients with ventricular tachycardia>7 and have been suggested as markers for the substrate of reentry. If these abnormal electrograms were reliably associated with the site of earliest endocardial activation during ventricular tachycardia, mapping during sinus rhythm could be used to guide surgical therapy. In the present study we evaluated the characteristics of abnormal endocardial electrograms measured in sinus rhythm during surgery for refractory ventricular tachycardia, and related the findings to the earliest site of endocardial activation during induced ventricular tachycardia. Methods The clinical characteristics of the study population are listed in table 1. There were eight men and five women with a mean Vol. 70, No. 6, December 1984 957 by gest on A ril 3, 2017 http://ciajournals.org/ D ow nladed from