Repolarization variability in 24-hour Holter ECG

Repolarization variability (RV) is associated with an increased risk of arrhythmic events. RV is usually measured in short ECG recordings, which do not allow the detection of its potential circadian characteristics and the identification of the time when an arrhythmic event is likely to occur. The aim of the authors' work was to develop and test a computer algorithm to measure RV in 24-hour Holter ECG recordings, and to look for associations between heart rare and RV in 12 patients showing isolated ectopic beats. From each 24-hour ECG, the authors selected and analyzed 48 128-beat ECG segments, one every 30 minutes. RV was measured analyzing the changes in the T-wave morphology. A RV index, that represents the mean value of the deviations of each consecutive T wave from a template, was computed for each ECG segment. The 48 RV indexes relative to an ECG finally provided information about the circadian trends of the RV signal.