Grom Andreas, Faber Thomas S, Brunner Michael, Bode Christoph, Zehender Manfred
Universitätsklinikum Freiburg, Abteilung Innere Medizin III, Hugstetterstrasse 55, D-79106 Freiburg, Germany.
Europace. 2005 Mar;7(2):113-21. doi: 10.1016/j.eupc.2005.01.001.
Onset and termination of atrial fibrillation are often associated with abrupt changes in heart rate. Presence and time-course of delayed adaptation of the QT/QTc interval are unknown, but a temporary "mismatch" between rate and the QT interval may enhance the risk of proarrhythmia.
In a prospective two-part study, time-course of adaptation of ventricular repolarization after abrupt changes in heart rate was assessed during termination of Holter ECG-documented atrial fibrillation episodes (Group 1, 32 patients) and subsequently in 20 patients with sick sinus syndrome and cardiac pacing initiating abrupt bi-directional changes in paced heart rate (Group 2).
Conversion of atrial fibrillation showed a 32+/-21 bpm fall in heart rate (P<0.05). Restoration of the QTc interval afterwards was delayed by < or =1 min in 27%, by 1-2 min in 21%, by 2-5 min in 11% and by >5 min in 41% of the cases. Atrial pacing simulating a 30 bpm fall/increase in atrial rate demonstrated that a subsequent transient rate-QT mismatch is a physiological phenomenon (fall of 100 to 70 bpm: initially 90% of the proper QTc interval, compared with 94% after conversion of atrial fibrillation). The restoration curve of QTc adaptation showed an initially fast and subsequently slower time component, with interindividual variation. Clinical parameters, baseline heart rate or the direction of rate changes were not predictive.
Delayed adaptation of ventricular repolarization following atrial fibrillation onset and termination is common, requiring minutes for restoring the QT/QTc steady state. Clinical parameters fail to predict patients with a long-lasting rate-QT mismatch. It may carry a significant arrhythmogenic risk particularly in patients on QT altering medication.
房颤的发作和终止常与心率的突然变化有关。QT/QTc间期延迟适应的存在情况和时间进程尚不清楚，但心率与QT间期之间暂时的“不匹配”可能会增加心律失常的风险。
在一项前瞻性的两部分研究中，在动态心电图记录的房颤发作终止期间（第1组，32例患者）评估心率突然变化后心室复极的适应时间进程，随后在20例病态窦房结综合征且心脏起搏导致起搏心率突然双向变化的患者中进行评估（第2组）。
房颤转复时心率下降32±21次/分（P<0.05）。之后，27%的病例QTc间期恢复延迟≤1分钟，21%延迟1 - 2分钟，11%延迟2 - 5分钟，41%延迟>5分钟。模拟心房率下降/增加30次/分的心房起搏表明，随后的短暂心率 - QT不匹配是一种生理现象（心率从100次/分降至70次/分：最初为正常QTc间期的90%，房颤转复后为94%）。QTc适应的恢复曲线显示出最初快速随后缓慢的时间成分，存在个体差异。临床参数、基础心率或心率变化方向均无预测价值。
房颤发作和终止后心室复极延迟适应很常见，恢复QT/QTc稳态需要数分钟。临床参数无法预测存在长期心率 - QT不匹配的患者。这可能尤其在服用改变QT的药物的患者中带来显著的致心律失常风险。
