Department of Molecular and Clinical Medicine, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
Department of Cardiology, Region Västra Götaland, Sahlgrenska University Hospital, Gothenburg Sweden.
Am J Physiol Heart Circ Physiol. 2021 Jan 1;320(1):H381-H392. doi: 10.1152/ajpheart.00542.2020. Epub 2020 Nov 8.
Adequate adaptation of ventricular repolarization (VR) duration to changes in heart rate (HR) is important for cardiac electromechanical function and electrical stability. We studied the QT and QT adaptation in response to abrupt start and stop of atrial and ventricular pacing on two occasions with an interval of at least 1 mo in 25 study subjects with permanent pacemakers. Frank vectorcardiography was used for data collection. Atrial or ventricular pacing was performed for 8 min aiming at a cycle length (CL) of 500 ms. We measured the immediate response (IR), the time constant (τ) of the exponential phase, and T90 End, the time to reach 90% change of QT and QT from baseline to steady state during and after pacing. During atrial pacing, the CL decreased on average 45% from mean (SD) 944 (120) to 518 (46) ms and QT decreased on average 18% from 388 (20) to 318 (17) ms. For QT, T90 End was 103 (24) s and 126 (15) s after start versus stop of atrial pacing; a difference of 24 (27) s ( = 0.006). The response pattern was similar for τ but IR did not differ significantly between pacing start and stop. The response pattern was similar for QT and also for QT and QT following ventricular pacing start and stop. The coefficients of variation for repeated measures were 7%-21% for T90 End and τ. In conclusion, the adaptation of VR duration was significantly more rapid following increasing than decreasing HR and intraindividually a relatively reproducible process. We studied the duration of ventricular repolarization (VR) adaptation and its hysteresis, following increasing and decreasing heart rate by abrupt start and stop of 8-min atrial or ventricular pacing in study subjects with permanent pacemakers and repeated the protocol with ≥1 mo interval, a novel approach. VR adaptation was significantly longer following decreasing than increasing heart rate corroborating previous observations. Furthermore, VR adaptation was intraindividually a reproducible and, hence, robust phenomenon, a novel finding.
心室复极（VR）持续时间对心率（HR）变化的充分适应对于心脏机电功能和电稳定性非常重要。我们在 25 名接受永久性起搏器治疗的研究对象中，至少间隔 1 个月，两次研究了心房和心室起搏突然开始和停止时 QT 和 QT 适应情况。使用 Frank 向量心电图进行数据采集。心房或心室起搏进行 8 分钟，目标是周长（CL）为 500ms。我们测量了即刻反应（IR）、指数相的时间常数（τ）以及 T90End，即在起搏期间和之后达到 QT 和 QT 从基线到稳定状态的 90%变化所需的时间。在心房起搏期间，CL 平均下降 45%，从平均值（SD）944（120）降至 518（46）ms，QT 平均下降 18%，从 388（20）降至 318（17）ms。对于 QT，T90End 在心房起搏开始和停止后分别为 103（24）s 和 126（15）s；相差 24（27）s（=0.006）。对于 τ，反应模式相似，但 IR 在起搏开始和停止之间没有显著差异。对于心室起搏开始和停止后 QT 和 QT 的反应模式相似。T90End 和 τ 的重复测量的变异系数为 7%-21%。总之，VR 持续时间的适应在 HR 增加时明显快于 HR 减少时，个体间是一个相对可重复的过程。我们通过在接受永久性起搏器治疗的研究对象中突然开始和停止 8 分钟的心房或心室起搏，研究了心率增加和减少时 VR 持续时间的适应及其滞后，并在至少间隔 1 个月的情况下重复了该方案，这是一种新方法。VR 适应在 HR 减少时明显长于 HR 增加时，这与之前的观察结果一致。此外，VR 适应在个体间是可重复的，因此是一种稳健的现象，这是一个新发现。
