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 electrocardiography (SAECG) and measurement of microvolt level T wave alternans as predictors of susceptibility to ventricular arrhythmias.


METHODS
Analysis of new data from a previously published prospective investigation.


METHODS
Electrophysiology laboratory of a major referral hospital.


METHODS
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.


METHODS
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.
Armoundas
A A
AA
Harvard University-Massachusetts Institute of Technology, Division of Health Sciences and Technology, Cambridge, USA.
Rosenbaum
D S
DS
Ruskin
J N
JN
Garan
H
H
Cohen
R J
RJ
D001145:Arrhythmias, Cardiac / Q000175:diagnosis*; D016009:Chi-Square Distribution; D004198:Disease Susceptibility; D018572:Disease-Free Survival; D004562:Electrocardiography; D004594:Electrophysiology; D006801:Humans; D011237:Predictive Value of Tests; D011379:Prognosis; D012008:Recurrence; D012189:Retrospective Studies; D012815:Signal Processing, Computer-Assisted