Investigation of Circadian Rhythm in T-wave Variability and Other Electrocardiographic Parameters Using Ambulatory Electrocardiographic Monitoring

Recently, T-wave variability (TWV) has been notified by Dr. Zareba et al., as attractive marker of repolarization abnormalities. Differing from T-wave alternans which merely observes alternative beat-to beat changes of the amplitude of T-waves, TWV reflects morphological changes of the entire component aspect of ST-T waves by dividing ST-T segment into 40 ms duration for each beat. This method was useful for identifying the high risk patients in myocardial ischemia or dilated cardiomyopathy, however until now there are still few reports about the utility. TWV was measured by the ambulatory monitoring, and therefore a clinical significance might be a great role to capture the repolarization changes during sleep at night. We investigated the longitudinal fluctuations of TWV in the two kinds of disease to stratify risks for fatal arrhythmia. One is Brugada syndrome and the other is sleep apnia syndrome. We used high-resolution ambulatory ECG (2.5 µV, 1000 Hz) manufactured by the Ela Medical company for 24-hours continuously. The data of TWV were analyzed and other electrocardiographic parameters including late potentials (LP), heart rate variability (HRV), heart rate turbulence (HRT), and QT/RR slope were also analyzed using same data. In this symposium, we will report the results of these analyses.