Modified moving average analysis of T-wave alternans to predict ventricular fibrillation with high accuracy

Abstract

moving average analysis of T-wave alternans to predict ven-tricular fibrillation with high accuracy. J Appl Physiol 92: 541–549, 2002; 10.1152/japplphysiol.00592.2001.—T-wave alternans is a marker of cardiac electrical instability with the potential for arrhythmia risk stratification. The modified moving average method was developed to measure alternans in settings with artifacts, noise, and nonstationary data. Algorithms were developed and performance characteristics were validated with simulated electrocardiograms (ECGs). Experimental laboratory ECGs with dynamically changing alternans values were analyzed. Alternans values estimated by modified moving average analysis correlated strongly with input alternans values (r2 0.9999). Rapidly changing alter-nans levels and phase reversals did not perturb the measure-ment. When heart rate was increased from 60 to 180 beats/ min, with T-wave alternans apex moving from 237 to 103 ms after the R wave, the measured alternans peak varied 5% from input value. Simulated 50- to 1,000-V motion artifact spikes typical of treadmill ECGs produced inaccuracies 2%. Alternans values in experimental laboratory study using standard electrodes tracked vulnerability to myocardial is-chemia-induced ventricular fibrillation with 100 % sensitivity and specificity at a cut point of 0.75 mV. Modified moving average analysis is a robust method that precisely measures T-wave alternans in settings with artifacts, noise, and non-stationary data typical of clinical ECGs and yields an accu-rate estimate of risk for ventricular fibrillation. risk assessment; sudden cardiac death; ventricular arrhy-thmias; ambulatory electrocardiogram; exercise treadmill testing A SUBSTANTIAL BODY OF CLINICAL and experimental evi-dence indicates that T-wave alternans, a beat-to-beat fluctuation in the amplitude of that waveform, is fun-damentally linked to vulnerability to ventricular fibril