title: Electrical alternans during rest and exercise as predictors of vulnerability to ventricular arrhythmias.
abstract: This investigation was performed to evaluate the feasibility of detecting repolarization alternans with the heart rate elevated with a bicycle 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 animal and human investigations using atrial or ventricular pacing have demonstrated that T-wave alternans is a marker of vulnerability to ventricular arrhythmias. Using a spectral analysis technique incorporating noise reduction signal-processing software, we evaluated electrical alternans at rest and with the heart rate elevated during a bicycle exercise protocol. In this study we defined optimal criteria for electrical alternans to separate patients from those without inducible arrhythmias. 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 fibrillation at electrophysiologic evaluation. In 27 patients alternans recorded at rest and with exercise had a sensitivity of 89%, specificity of 75%, and overall clinical accuracy of 80% (p <0.003). In this patient population the signal-averaged electrocardiogram was not a significant predictor of arrhythmia vulnerability. This is the first study to report that repolarization alternans can be detected with heart rate elevated with a bicycle exercise protocol. Alternans measured using this technique is an accurate predictor of arrhythmia inducibility.
authors.affiliation: Department of Medicine, New England Medical Center Hospital, Tufts University School of Medicine, Boston, Massachusetts 02111, USA.
authors.forename: N A
authors.initials: NA
authors.lastname: Estes
authors.forename: G
authors.initials: G
authors.lastname: Michaud
authors.forename: D P
authors.initials: DP
authors.lastname: Zipes
authors.forename: N
authors.initials: N
authors.lastname: El-Sherif
authors.forename: F J
authors.initials: FJ
authors.lastname: Venditti
authors.forename: D S
authors.initials: DS
authors.lastname: Rosenbaum
authors.forename: P
authors.initials: P
authors.lastname: Albrecht
authors.forename: P J
authors.initials: PJ
authors.lastname: Wang
authors.forename: R J
authors.initials: RJ
authors.lastname: Cohen
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001145:Arrhythmias, Cardiac / Q000175:diagnosis* / Q000209:etiology / Q000503:physiopathology; D002304:Cardiac Pacing, Artificial; D002311:Cardiomyopathy, Dilated / Q000503:physiopathology; D003327:Coronary Disease / Q000503:physiopathology; D004562:Electrocardiography; D015444:Exercise; D005240:Feasibility Studies; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D012815:Signal Processing, Computer-Assisted