Adaptation of ventricular repolarization duration and dispersion during changes in heart rate induced by atrial stimulation

Abstract

Background The duration of ventricular repolarization (VR) and its spatial and temporal heterogeneity are central elements in arrhythmogenesis. We studied the adaptation of VR duration and dispersion and their relationship in healthy human subjects during atrial pacing. Methods Patients 20‐50 years of age who were scheduled for ablation of supraventricular tachycardia without preexcitation but otherwise healthy were eligible. Vectorcardiography recordings with Frank leads were used for data collection. Incremental atrial pacing from a coronary sinus electrode was performed by decrements of 10ms/cycle from just above sinus rate, and then kept at a fixed heart rate (HR) just below the Wenckebach rate for ≥5min and then stopped. VR duration was measured as QT and VR dispersion as T area, T amplitude and ventricular gradient. The primary measure (T90 End) was the time to reach 90% change from baseline to the steady state value during and after pacing. Results A complete study protocol was accomplished in 9 individuals (6 women). VR duration displayed a monophasic adaptation during HR acceleration lasting on average 20s. The median (Q1‐Q3) T90 End for QT was 85s (51‐104), a delay by a factor >4. All dispersion measures displayed a tri‐phasic response pattern during HR acceleration and T90 End was 3‐5 times shorter than for VR duration. Conclusions Even during close to “physiological” conditions, complex and differing response patterns in VR duration and dispersion measures followed changes in HR. Extended knowledge about these responses in disease conditions might assist in risk evaluation and finding therapeutic alternatives.

Automatic identification of a stable QRST complex for non-invasive evaluation of human cardiac electrophysiology

“…The time-limiting step of the recording phase was defined by the hysteresis of the ventricular repolarization adaptation to a change in heart rate which is minimum 3 min [ 18 , 21 ]. A 5 min resting period with closed eyes during silence therefore preceded a recording period ≥5min.…”

“…facilitated by a web-based QT calculator [ 26 , 31 ], the tangent method has been favored by others [ 32 ]. The tangent method is more suitable than the threshold method for studying ventricular repolarization changes on a beat-to-beat level during rapid heart rate increase according to our own experience [ 16 – 18 ]. We therefore decided on the tangent method for the entirely automatic VCG analysis of saQRST complexes so that the same automatic method could be used for analyses of beat-to-beat and steady-state signal-averaged cardiac cycles.…”

“…The methodology followed the basic principles applied in our previous studies [16][17][18]. The protocol stipulated 5 minutes of supine rest with closed eyes and no conversation to allow heart rate stabilization and heart rate adaptation of ventricular repolarization before the VCG recording period of �5 min (preferably 8-10 min).…”

“…The analysis software was developed from the CoroNet platform (Ortivus AB, Danderyd, Sweden) but using the tangent method for defining the end of the T wave which we have applied in beat-to-beat analyses of ventricular repolarization dynamics [16][17][18].…”

Accelerated QT adaptation following atropine‐induced heart rate increase in LQT1 patients versus healthy controls: A sign of disturbed hysteresis

“…Although atrial and ventricular pacing result in similar dynamics in QT hysteresis, ventricular pacing induces potentially confounding repolarization changes related to ventricular activation‐induced short‐term cardiac memory, at least when ventricular pacing lasts 8 minutes or more (Axelsson et al, 2021 ; Rosen & Bergfeldt, 2015 ). Incremental atrial pacing is presumably most physiological and was applied in one of our previous studies on patients with supraventricular tachycardia but otherwise healthy undergoing heart catheterization for ablation therapy (Axelsson et al, 2020 ). Difficulties with keeping 1:1 atrio‐ventricular conduction at a fixed atrio‐ventricular conduction interval and HR turned out to be a problem in that study.…”