Are the T-wave alternans amplitude 'zones' related to T-wave amplitude 'zones' in ECG ambulatory recordings?

摘要

The contribution by Burattini et al. published ahead of print in the Journal, dealt with an identification of four "zones" of amplitude/duration of T-wave alternans (TWA) in 200 patients with coronary artery diseased and 176 healthy subjects. The four "zones" or "subzones" as the authors called them were formed by considering low and high amplitude of the TWA signal, of short or long duration, with magnitude of the TWA defined as the product of amplitude and duration of TWA signals, from ambulatory ECG tracings. This is a methodological study, which did not set out to evaluate the performance of the authors' method in predicting clinical events or ICD-based therapeutic shocks. Nevertheless, it is of interest that the study used thresholds from healthy subjects to determine what should be considered abnormal or normal in the patients with coronary artery disease. This should be commended and should be emulated by other workers who may also elect to study healthy subjects along with their target pathological populations, instead of relying on muV thresholds established previously (e.g., >1.9 muV), or decided upon based on the best negative predictive performance of arrhythmic events. The amplitude of TWA is viewed with increasing frequency as an important aspect in the assessment of TWA in patients, and this applies both to the time domain analysis (e.g., modified moving average) and the frequency domain spectral analytic method, in-spite the customary employment of the >1.9 muV threshold.