Optimizing ambulatory ECG monitoring of T-wave alternans for arrhythmia risk assessment.

Considerable scientific data support the potential value of T-wave alternans (TWA) as an index of vulnerability to ventricular fibrillation. This chapter summarizes our state of knowledge regarding the use of routine ambulatory ECGs to evaluate TWA and discusses recent methodologic approaches designed to optimize AECG-based TWA analysis for arrhythmia risk stratification. Newer methods, including the nonspectral technique of Modified Moving Average analysis, appear promising in detecting TWA during the changing conditions associated with daily activities. The Modified Moving Average approach does not require specialized electrodes and is not encumbered by the need to achieve target heart rates, as is the case for conventional spectral-based methods. Guidelines are provided for evaluating latent cardiac electrical instability using AECG-based TWA testing. These recent developments make possible the TWA analysis of ambulatory ECGs not only in prospective trials but also in vast stores of archival data.