title: Ability of ambulatory ECG-based T-wave alternans to modify risk assessment of cardiac events: a systematic review.
abstract: BACKGROUND
  Exercise-based spectral T-wave alternans (TWA) has been proposed as a noninvasive tool-identifying patients at risk of sudden cardiac death (SCD) and cardiac mortality. Prior studies have indicated that ambulatory electrocardiogram (AECG)-based TWA is an important alternative platform to exercise for risk stratification of cardiac events. This study sought to review data regarding 24-hour AECG-based TWA and to discuss its potential role in risk stratification of fatal cardiac events across a series of patient risk profiles.
  
  
  METHODS
  Prospective clinical studies of the predictive value of AECG-based TWA obtained with daily activity published between January 1990 and November 2014 were retrieved. Major endpoints included composite endpoint of SCD, cardiac mortality, and severe arrhythmic events.
  
  
  RESULTS
  Data were accumulated from 5 studies involving a total of 1,588 patients, including 317 positive and 1,271 negative TWA results. Compared with the negative group, positive group showed increased rates of SCD (hazard ratio [HR]: 7.49, 95% confidence interval [CI]: 2.65 to 21.15), cardiac mortality (HR: 4.75, 95% CI: 0.42 to 53.55), and composite endpoint (SCD, cardiac mortality, and severe arrhythmic events, HR: 5.94, 95% CI: 1.80 to 19.63). For the 4 studies evaluating TWA measured using the modified moving average method, the HR associated with a positive versus negative TWA result was 9.51 (95% CI: 4.99 to 18.11) for the composite endpoint.
  
  
  CONCLUSIONS
  The positive group of AECG-based TWA has a nearly six-fold risk of severe outcomes compared with the negative group. Therefore, AECG-based TWA provides an accurate means of predicting fatal cardiac events.
authors.forename: Xiao-Qing
authors.initials: XQ
authors.lastname: Quan
authors.forename: Hong-Lian
authors.initials: HL
authors.lastname: Zhou
authors.forename: Lei
authors.initials: L
authors.lastname: Ruan
authors.forename: Jia-Gao
authors.initials: JG
authors.lastname: Lv
authors.forename: Ji-Hua
authors.initials: JH
authors.lastname: Yao
authors.forename: Feng
authors.initials: F
authors.lastname: Yao
authors.forename: Kui
authors.initials: K
authors.lastname: Huang
authors.affiliation: Department of Geriatrics, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China. ctzhang@tjh.tjmu.edu.cn.
authors.forename: Cun-Tai
authors.initials: CT
authors.lastname: Zhang
mesh_terms: D016757:Death, Sudden, Cardiac; D015716:Electrocardiography, Ambulatory; D006801:Humans; D009203:Myocardial Infarction / Q000401:mortality*; D018570:Risk Assessment / Q000379:methods*