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Characterization of cardiac repolarization response to heart rate changes provoked by a tilt test

Abstract:

In pbkp_redicting the risk of suffering from ventricular arrhythmias, the dynamics of QT and T-peak-to-T-end (Tpe) intervals after changes in heart rate (HR) provide richer information than their values themselves. In this study, QT/RR and Tpe/RR dynamics were investigated. Electrocardiogram (ECG) recordings of healthy subjects were analyzed during a head-up tilt test. ECGs were delineated using multi-lead (ML) and single-lead (SL) techniques and the QT and Tpe intervals series were obtained. QT/RR and Tpe/RR dynamics were modeled using a nonlinear system, from which the time constant of adaptation t90 was derived. QT/RR dynamics is similar using SL or ML delineation, with adaptation times being: tSL90[s] = 49.7 +/-29.0, tML90 [s] = 47.1 +/- 20.1. The Tpe interval responded more abruptly to HR when calculated using SL as compared to ML. Consequently, Tpe/RR dynamics were characterized by different adaptation time constants depending on whether SL or ML was used: tSL90 [s] = 25.6 +/- 37.3, t SL90 [s] = 56.4 +/- 48.3. QT dynamics can be invariantly characterized using either SL or ML delineation, while Tpe dynamics are highly sensitive to the delineation method. Differences arise from the way SL and ML delineation are affected by T-wave loop rotation. Care should be taken when electrophysiological interpretation is provided to measurements obtained from one or the other delineation methods. © 2012 CCAL.