PROGNOSTIC-SIGNIFICANCE OF ELECTRICAL ALTERNANS VERSUS SIGNAL-AVERAGED ELECTROCARDIOGRAPHY IN PREDICTING THE OUTCOME OF ELECTROPHYSIOLOGICAL TESTING AND ARRHYTHMIA-FREE SURVIVAL

Objective-To investigate the accuracy of signal averaged electrocardio graphy (SAECG) and measurement of microvolt level T wave alternans as predictors of susceptibility to ventricular arrhythmias. Design-Analys is of new data from a previously published prospective investigation. Setting-Electrophysiology laboratory of a major referral hospital. Pat ients and interventions-43 patients, not on class I or class III antia rrhythmic drug treatment, undergoing invasive electrophysiological tes ting had SAECG and T wave alternans measurements. The SAECG was consid ered positive in the presence of one (SAECG-I) or two (SAECG-II) of th ree standard criteria. T wave alternans was considered positive if the alternans ratio exceeded 3.0. Main outcome measures-Inducibility of s ustained ventricular tachycardia or fibrillation during electrophysiol ogical testing, and 20 month arrhythmia-free survival. Results-The acc uracy of T wave alternans in predicting the outcome of electrophysiolo gical testing was 84% (p < 0.0001). Neither SAECG-I (accuracy 60%; p < 0.29) nor SAECG-II (accuracy 71%; p < 0.10) was a statistically signi ficant predictor of electrophysiological testing. SAECG, T wave altern ans, electrophysiological testing, and follow up data were available i n 36 patients while not on class I or III antiarrhythmic agents. The a ccuracy of T wave alternans in predicting the outcome of arrhythmia-fr ee survival was 86% (p < 0.030). Neither SAECG-I (accuracy 65%; p < 0. 21) nor SAECG-II (accuracy 71%; p < 0.48) was a statistically signific ant predictor of arrhythmia-free survival. Conclusions-T wave alternan s was a highly significant predictor of the outcome of electrophysiolo gical testing and arrhythmia-free survival, while SAECG was not a stat istically significant predictor. Although these results need to be con firmed in prospective clinical studies, they suggest that T wave alter nans may serve as a non-invasive probe for screening high risk populat ions for malignant ventricular arrhythmias.