title: Microvolt-level T-wave alternans determination using the spectral method in patients with QT prolongation: value of adjusting the T-wave window.
abstract: BACKGROUND
  Microvolt-level T-wave alternans (MTWA) measured by the spectral method is a useful risk predictor for sudden cardiac death because of its high negative predictive value. MTWA analysis software selects a segment of the ECG that encompasses the T-wave in most individuals, but may miss the T-wave end in patients with QT prolongation.
  
  
  OBJECTIVE
  (1) In patients with QT prolongation, adjustment of the T-wave window will increase the sensitivity of MTWA detection. (2) The extent of T-wave window adjustment needed will correspond to the degree of QT prolongation.
  
  
  METHODS
  Using data from long-QT syndrome patients, including QTc <0.45 s (normal), 0.45-0.49 s (moderate prolongation), and ≥ 0.50s (severe prolongation), MTWA analysis was performed before and after T-wave window adjustment.
  
  
  RESULTS
  Of 119 patients, 74% required T-wave window adjustment. There was a stronger association between the magnitude of the T-wave offset and the unadjusted QT than between the magnitude of the T-wave offset and QTc (Spearman correlation coefficient 0.690 vs. 0.485 respectively, P<.05). Of 99 initially negative MTWA results, 4 became non-negative after adjustment of the T-wave window (P<.05). All 8 initially positive studies and 12 initially indeterminate studies remained positive and indeterminate, respectively.
  
  
  CONCLUSIONS
  T-wave window adjustment can enable detection of abnormal MTWA that otherwise would be classified as "negative" or "normal." Newly developed T-wave window adjustment software may further improve the negative predictive value of MTWA testing and should be validated in a structural heart disease population.
authors.affiliation: Heart and Vascular Research Center, MetroHealth Campus of Case Western Reserve University, Cleveland, OH 44109-1998, USA. ekaufman@metrohealth.org
authors.forename: Elizabeth S
authors.initials: ES
authors.lastname: Kaufman
authors.forename: Steven A
authors.initials: SA
authors.lastname: Lewis
authors.forename: Peter
authors.initials: P
authors.lastname: Leo
authors.forename: Ganesh
authors.initials: G
authors.lastname: Aswath
authors.forename: Ohad
authors.initials: O
authors.lastname: Ziv
authors.forename: Lahn
authors.initials: L
authors.lastname: Fendelander
mesh_terms: D000328:Adult; D000465:Algorithms; D003936:Diagnosis, Computer-Assisted / Q000379:methods*; D004562:Electrocardiography / Q000379:methods*; D005260:Female; D006801:Humans; D008133:Long QT Syndrome / Q000175:diagnosis*; D008297:Male; D010363:Pattern Recognition, Automated / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity