title: Long-term reproducibility of microvolt T-wave alternans in patients after cardioverter-defibrillator implantation.
abstract: BACKGROUND
  Microvolt T-wave alternans (MTWA) is a promising method for noninvasive assessment of arrhythmic risk. Recent studies have shown good immediate reproducibility of T-wave alternans. Little is known about it during the long term. The aim of the study was to prospectively evaluate the long-term reproducibility of MTWA in a group of patients after ICD implantation.
  
  
  METHODS
  The study group consisted of 22 patients: 21 male and 1 female, aged 63.0 +/- 7.6 years. Nineteen of them had a history of myocardial infarction and 3 had non-ischemic cardiomyopathy. Ejection fraction was 34.7 +/- 10.0. T-wave alternans was measured during treadmill tests and additionally in 6 patients during implantation cardioverter-defibrillator device pacing. We received 30 reports of MTWA available for analysis. The second test was performed after 11.8 +/- 3.3 months (range 7-16) using the same protocol.
  
  
  RESULTS
  Of the 30 tests, 12 were positive, 2 negative and 9 indeterminate in both tests. The results were concordant in 23 tests (76.66%) (Kappa 0.602). Of the initial positive tests, only one became negative in the second test and 4 became indeterminate. Of the initial negative tests, none became positive and none became indeterminate. Of the initial indeterminate tests, one became positive and one negative. At the same time, there were no significant differences between QRS, QTc and ejection fraction between the first and second tests. Only the heart rate in the second test was greater than in the first.
  
  
  CONCLUSIONS
  The results suggest that microvolt T-wave alternans measurement is stable over a long period. It is probably not worth examining the status of MTWA after several months, at least if patients are in the chronic stage of their disease. (Cardiol J 2007; 14: 561-567).
authors.forename: Robert
authors.initials: R
authors.lastname: Wierzbowski
authors.forename: Dariusz
authors.initials: D
authors.lastname: Michałkiewicz
authors.forename: Karol
authors.initials: K
authors.lastname: Makowski
authors.forename: Paweł
authors.initials: P
authors.lastname: Smurzyński
authors.forename: Robert
authors.initials: R
authors.lastname: Ryczek
authors.forename: Andrzej
authors.initials: A
authors.lastname: Cwetsch
authors.forename: Marian
authors.initials: M
authors.lastname: Cholewa