ELECTRICAL ALTERNANS DURING REST AND EXERCISE AS PREDICTORS OF VULNERABILITY TO VENTRICULAR ARRHYTHMIAS

This investigation was performed to evaluate the feasibility of defect ing repolarization alternans with the heart rate elevated with a bicyc le exercise protocol. Sensitive spectral signal-processing techniques are able to detect beat-to-beat alternation of the amplitude of the T wave, which is not visible on standard electrocardiogram. Previous ani mal and human investigations using atrial or ventricular pacing have d emonstrated that T-wave alternans is a marker of vulnerability to vent ricular arrhythmias, Using a spectral analysis technique incorporating noise reduction signal-processing software, we evaluated electrical a lternans at rest and with the heart rate elevated during a bicycle exe rcise protocol, In this study we defined optimal criteria for electric al alternans to separate patients from those without inducible arrhyth mias, Alternans and signal-averaged electrocardiographic results were compared with the results of vulnerability to ventricular arrhythmias as defined by induction of sustained ventricular tachycardia or fibril lation st electrophysiologic evaluation. In 27 patients alternans reco rded at rest and with exercise had a sensitivity of 89%, specificity o f 75%, and overall clinical accuracy of 80% (p < 0.003). In this patie nt population the signal-averaged electrocardiogram was not a signific ant predictor of arrhythmia vulnerability. This is the first study to report that repolarization alternans can be detected with heart rate e levated with a bicycle exercise protocol, Alternans measured using thi s technique is an accurate predictor of arrhythmia inducibility. (C) 1 997 by Excerpta Medica, Inc.