title: Post-exercise assessment of cardiac repolarization alternans in patients with coronary artery disease using the modified moving average method.
abstract: OBJECTIVE
  We sought to evaluate the utility of T-wave alternans (TWA) assessment in the immediate post-exercise period to identify and validate cutpoints for the modified moving average (MMA) assessment method.
  
  
  BACKGROUND
  The presence of TWA is associated with an increased risk of cardiovascular death (CVD). The immediate post-exercise period, where increased physiologic stress and minimal surface artifact coexist, appears ideal to implement the MMA method.
  
  
  METHODS
  A test (n = 322) and validation cohort (n = 681) provided 1,003 patients with coronary artery disease (CAD). We assessed TWA immediately after exercise. The outcomes, CVD and mortality, were adjudicated independent of the TWA results.
  
  
  RESULTS
  During 48 months of follow-up 85 deaths, 54 categorized as CVD (64%), were observed. A linear relationship between the magnitude of TWA and the risk of CVD was identified. As a continuous measure TWA voltage was equivalent to ejection fraction in predicting the risk of CVD. To facilitate clinical application, a sensitive, modest predictive accuracy (20 microV) and a specific, greater predictive accuracy MMA cutpoint (60 microV) were identified and validated. Each cutpoint was associated with a 2.5-fold greater risk of CVD, independent of other important variables, including ejection fraction.
  
  
  CONCLUSIONS
  Post-exercise assessment of TWA using the MMA method is a strong, independent predictor of risk in patients with CAD. The 20-microV cutpoint (87% sensitivity) appears to be most suitable in higher-risk patients, whereas the 60-microV cutpoint (95% specificity) appears more appropriate when TWA is used as a single screening test in those at lower risk. (Assessment of Noninvasive Methods to Identify Patients at Risk of Serious Arrhythmias After a Heart Attack; NCT00399503).
authors.affiliation: Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, Alberta, Canada.
authors.forename: Michael P
authors.initials: MP
authors.lastname: Slawnych
authors.forename: Tuomo
authors.initials: T
authors.lastname: Nieminen
authors.forename: Mika
authors.initials: M
authors.lastname: Kähönen
authors.forename: Katherine M
authors.initials: KM
authors.lastname: Kavanagh
authors.forename: Terho
authors.initials: T
authors.lastname: Lehtimäki
authors.forename: Darlene
authors.initials: D
authors.lastname: Ramadan
authors.forename: Jari
authors.initials: J
authors.lastname: Viik
authors.forename: Sandeep G
authors.initials: SG
authors.lastname: Aggarwal
authors.forename: Rami
authors.initials: R
authors.lastname: Lehtinen
authors.forename: Linda
authors.initials: L
authors.lastname: Ellis
authors.forename: Kjell
authors.initials: K
authors.lastname: Nikus
authors.forename: Derek V
authors.initials: DV
authors.lastname: Exner