CHARACTERISTICS OF SINUS RHYTHM ELECTROGRAMS AT SITES OF ABLATION OF VENTRICULAR-TACHYCARDIA RELATIVE TO ALL OTHER SITES - A NONCONTACT MAPPING STUDY OF THE ENTIRE LEFT-VENTRICLE

Introduction: Regions of the diseased ventricle that activate abnormal ly during sinus rhythm (SR) may be the areas of slow and disorganized conduction that form the diastolic pathway through which reentry may o ccur during ventricular tachycardia (VT). Methods and Results: We exam ined features of electrograms recorded during SR that might indicate a site suitable for ablation of VT using a noncontact mapping system, w hich enables reconstruction of > 3,000 electrograms. Preablation SR el ectrogram characteristics at sites of successful radiofrequency ablati on (RFA) were examined in 13 patients with 53 VTs, Timing of onset, la teness of activity, electrogram duration, and number of baseline cross ing events of reconstructed electrograms at the sites of successful RF A were compared with the electrograms of latest onset, latest activity , longest duration, and most baseline crossing events of all ventricul ar sites. Onset of activation at sites of successful RFA were 26.9 +/- 25.2 msec (mean +/- SD) earlier than (and 2.9 +/- 1.7 cm away from) t he site of latest onset of SR activation. Electrogram duration at site s of successful RFA was 83% +/- 14.6% of (and 4.3 +/- 1.8 cm away from ) the longest electrogram. The baseline crossing events at sites of su ccessful RFA were 53% +/- 22% of (and 4.9 +/- 1.9 cm away from) the mo st fractionated electrogram. The latest activity at sites of successfu l RFA was 21.6 +/- 24.8 msec earlier than (and 4.3 +/- 1.6 cm away fro m) the site of latest activity. Conclusion: Although the site of lates t onset of endocardial activation during SR proved to be the most sens itive indicator, the characteristics of SR electrograms did not useful ly predict successful ablation sites.