title: Microvolt T-wave alternans during exercise and pacing are not comparable.
abstract: OBJECTIVE
  The absence of microvolt T-wave alternans (MTWA) identifies a group of patients who are at low risk for ventricular arrhythmia or sudden cardiac death. However, in exercised assessed MTWA, 20-40% of all test results are indeterminate. We hypothesised that MTWA during pacing would yield less indeterminate results.
  
  
  RESULTS
  Thirty patients with ischaemic cardiomyopathy and prior dual chamber implantable cardioverter defibrillator implantation were enrolled. All patients underwent sequential MTWA testing using an exercise (E), atrial-paced (A), and atrioventricular-paced (AV) protocol. The number of indeterminate tests was lower during pacing (A: 17%; AV: 3%) compared with exercise (37%) (E vs. A: P = 0.015, E vs. AV: P = <0.001). When positive and indeterminate test results were grouped as non-negative, the concordance rates between E and A, E and AV, and A and AV were 60% (kappa = 0.17), 57% (kappa = 0.058), and 70% (kappa = 0.348), respectively. If indeterminate results were excluded, agreements were 60% (kappa = 0.19), 50% (kappa = 0.129) and 67% (kappa = 0.33), respectively.
  
  
  CONCLUSIONS
  Indeterminate test results are less common during pacing. However, there is a low concordance rate between test results using different protocols. This necessitates further study to determine the predictive value of each method in high risk patients with ischaemic cardiomyopathy.
authors.affiliation: Department of Cardiology, Thoraxcentrum Twente, Medisch Spectrum Twente, Haaksbergerstraat 55, 7513 ER Enschede, The Netherlands.
authors.forename: Karin
authors.initials: K
authors.lastname: Kraaier
authors.forename: Patrick M J
authors.initials: PM
authors.lastname: Verhorst
authors.forename: Job
authors.initials: J
authors.lastname: van der Palen
authors.forename: Pascal F H M
authors.initials: PF
authors.lastname: van Dessel
authors.forename: Arthur A M
authors.initials: AA
authors.lastname: Wilde
authors.forename: Marcoen F
authors.initials: MF
authors.lastname: Scholten
mesh_terms: D002304:Cardiac Pacing, Artificial / Q000379:methods*; D009202:Cardiomyopathies / Q000150:complications / Q000175:diagnosis*; D004562:Electrocardiography / Q000379:methods*; D005080:Exercise Test / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D017202:Myocardial Ischemia / Q000150:complications / Q000175:diagnosis*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity