Ambulatory Electrocardiogram‐Based Tracking of T Wave Alternans in Postmyocardial Infarction Patients to Assess Risk of Cardiac Arrest or Arrhythmic Death

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Abstract
Introduction: 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. Methods and 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). Conclusion: 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. (J Cardiovasc Electrophysiol, Vol. 14, pp. 705‐711, July 2003)