title: Ambulatory electrocardiogram-based tracking of T wave alternans in postmyocardial infarction patients to assess risk of cardiac arrest or arrhythmic death.
abstract: BACKGROUND
  This is the first study to assess T wave alternans (TWA) analyzed from routine ambulatory electrocardiograms (AECGs) to identify postmyocardial infarction (post-MI) patients at increased risk for arrhythmic events.
  
  
  RESULTS
  The new method of modified moving average (MMA) analysis was used to measure TWA magnitude in 24-hour AECGs from ATRAMI, a prospective study of 1,284 post-MI patients. Using a nested case-control approach, we defined cases as patients who experienced cardiac arrest due to documented ventricular fibrillation or arrhythmic death during the follow-up period of 21 +/- 8 months. We analyzed 15 cases and 29 controls matched for sex, age, site of MI, left ventricular ejection fraction, thrombolysis, and beta-blockade therapy. TWA was reported as the maximum 15-second value at three predetermined times associated with cardiovascular stress: maximum heart rate, 8:00 A.M., and maximum ST segment deviation. TWA increased significantly from baseline in both leads at each time point (P <<0.01) in cases and controls. TWA in V5 increased more in cases than controls during peak heart rate (P = 0.005) and at 8:00 A.M. (P = 0.02). A 4- to 7-fold higher odds of life-threatening arrhythmias was predicted by TWA level above the 75th percentile during maximum heart rate in leads V1 (odds ratio [OR] 4.2, 95% confidence interval [CI]: 1.1-16.3, P = 0.04) and V5 (OR 7.9, 95% CI: 1.9-33.1, P = 0.005). TWA at 8:00 A.M. also predicted risk in leads V1 (OR = 5.0, 95% CI: 1.2-20.5, P = 0.02) and V5 (OR = 4.2, 95% CI: 1.1-16.3, P = 0.04).
  
  
  CONCLUSIONS
  TWA measurement from routine 24-hour AECGs is a promising approach for risk stratification for cardiac arrest and arrhythmic death in relatively low-risk post-MI patients.
authors.affiliation: Beth Israel Deaconess Medical Center and Harvard Medical School, One Autumn Street, W/KN-521, Boston, MA 02215, USA. rverrier@bidmc.harvard.edu
authors.forename: Richard L
authors.initials: RL
authors.lastname: Verrier
authors.forename: Bruce D
authors.initials: BD
authors.lastname: Nearing
authors.forename: Maria Teresa
authors.initials: MT
authors.lastname: La Rovere
authors.forename: Gian Domenico
authors.initials: GD
authors.lastname: Pinna
authors.forename: Murray A
authors.initials: MA
authors.lastname: Mittleman
authors.forename: J Thomas
authors.initials: JT
authors.lastname: Bigger
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Schwartz
mesh_terms: D000465:Algorithms; D001145:Arrhythmias, Cardiac / Q000175:diagnosis* / Q000453:epidemiology / Q000209:etiology / Q000517:prevention & control; D016757:Death, Sudden, Cardiac / Q000453:epidemiology / Q000517:prevention & control; D003936:Diagnosis, Computer-Assisted / Q000379:methods*; D015716:Electrocardiography, Ambulatory / Q000379:methods* / Q000706:statistics & numerical data; D005060:Europe / Q000453:epidemiology; D005260:Female; D006323:Heart Arrest / Q000175:diagnosis* / Q000453:epidemiology / Q000209:etiology / Q000517:prevention & control; D006801:Humans; D007564:Japan / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000150:complications / Q000175:diagnosis* / Q000453:epidemiology; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D018570:Risk Assessment / Q000379:methods; D012307:Risk Factors; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted; D014481:United States / Q000453:epidemiology