Prognostic significance of electrical alternans versus signal averaged electrocardiography in predicting the outcome of electrophysiological testing and arrhythmia-free survival
- aHarvard University –Massachusetts Institute of Technology Division of Health Sciences and Technology, Cambridge, Massachusetts, USA, bDepartments of Medicine and Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio, USA, cThe Cardiac Unit, Massachusetts General Hospital, Boston, Massachusetts, USA
- Dr R J Cohen, Massachusetts Institute of Technology, E25-335, 77 Massachusetts Avenue, Cambridge, MA 02139, USA. email:rjcohen{at}mit.edu
- Accepted 30 March 1998
Abstract
Objective To investigate the accuracy of signal averaged electrocardiography (SAECG) and measurement of microvolt level T wave alternans as predictors of susceptibility to ventricular arrhythmias.
Design Analysis of new data from a previously published prospective investigation.
Setting Electrophysiology laboratory of a major referral hospital.
Patients and interventions 43 patients, not on class I or class III antiarrhythmic drug treatment, undergoing invasive electrophysiological testing had SAECG and T wave alternans measurements. The SAECG was considered positive in the presence of one (SAECG-I) or two (SAECG-II) of three standard criteria. T wave alternans was considered positive if the alternans ratio exceeded 3.0.
Main outcome measures Inducibility of sustained ventricular tachycardia or fibrillation during electrophysiological testing, and 20 month arrhythmia-free survival.
Results The accuracy of T wave alternans in predicting the outcome of electrophysiological 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 significant predictor of electrophysiological testing. SAECG, T wave alternans, electrophysiological testing, and follow up data were available in 36 patients while not on class I or III antiarrhythmic agents. The accuracy of T wave alternans in predicting the outcome of arrhythmia-free 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 significant predictor of arrhythmia-free survival.
Conclusions—T wave alternans was a highly significant predictor of the outcome of electrophysiological testing and arrhythmia-free survival, while SAECG was not a statistically significant predictor. Although these results need to be confirmed in prospective clinical studies, they suggest that T wave alternans may serve as a non-invasive probe for screening high risk populations for malignant ventricular arrhythmias.
