211 CRT responders. Nychtamer dynamicity of Ventricular Repolarization during Biventricular Pacing, vs, Unichamber Pacing

Abstract

The dynamic analysis of cardiac signals may reveal cardiovascular system abnormalities. In pts with fixed heart rate, the dynamic behavior of the repolarization phase (QT interval) is mainly related to the sympathovagal balance. Aim of the study was to evaluate the QT changes in two dimensions (space and time), in continuously paced pts with heart failure (HF), under biventricular pacing (BiV, LV pacing first), RV apex pacing and epicardial LV pacing. 22 pts with drug refractory HF, chronic AF, iatrogenic C.AV. block (due to RFAVJ ablation) and responders to CRT were evaluated at 6 mos post-implant, with a 24h Holter monitoring under BiV pacing, RV apex and LV pacing, at a fixed rate of 70 bpm. A chrono-spatial analysis (Frank leads, XYZ) of the repolarization interval was performed, during day (7h-22h) and night (23h-6h) time. Under BiV pacing, the spike-T(end) interval is characterized by a dynamic circadian behavior, with higher values during the night (440±35ms) compared to the day time period (395±40ms, P<0.05). On the contrary, RV apex (425±50ms, vs 395± 60ms, P=NS), and LV pacing (415±82ms, vs 390±55ms, P=NS) abolishes the circadian behavior of the repolarization. In CRT responders, the repolarization phase maintains the nychtamer dynamic behavior. On the contrary, it is disappeared under RV apex or LV free wall pacing. The amelioration of the sympathovagal balance in CRT responders is a possible explanation.