Extramiana Fabrice, Maison-Blanche Pierre, Denjoy Isabelle, De Jode Patrick, Messali Anne, Labbé Jean-Philippe, Leenhardt Antoine
University Paris Diderot, Paris, France.
Ann Noninvasive Electrocardiol. 2013 Jul;18(4):399-408. doi: 10.1111/anec.12048. Epub 2013 May 3.
In the long QT syndrome (LQTS) the effects of beta-blocker treatment on prevention of cardiac events differs according to the genotype. We aimed to assess the effect of beta-blocker treatment on QT/QTc duration in Type 1 LQTS (LQT1) and Type 2 LQTS (LQT2) patients.
24-hour digital Holter ECG were recorded before and after beta-blocking therapy initiation in LQT1 (n = 30) and LQT2 patients (n = 16). QT duration was measured on consecutive 1-minute averaged QRS-T complexes leading to up to 1440 edited QT-RR pairs for each recording. We computed subject- and treatment-specific log/log QT/RR relationships which were used to correct the QT intervals. The QT duration was also evaluated at predefined heart rates and after correction using Bazett and Fridericia coefficients.
At baseline, individual QT/RR coefficients were higher in LQT2 than in LQT1 patients (0.53 ± 0.10 vs. 0.40 ± 0.11, P < 0.001) and QT1000 was longer in LQT2 than in LQT1 patients (521 ± 38 vs. 481 ± 39 ms, P < 0.01). Beta-blockers significantly prolonged the mean RR interval (from 827 ± 161 to 939 ± 197 ms, P < 0.0001). The individual QT/RR coefficients were not significantly modified by beta-blockers. Beta-blocker treatment was associated with a prolongation of the QT1000 interval (from 481 ± 39 to 498 ± 43 ms, P < 0.01) in LQT1 patients but with a shortening in LQT2 patients (from 521 ± 38 to 503 ± 32 ms, P < 0.01).
The effect of beta-adrenergic blockade on QTc duration is different in LQT1 and LQT2 patients. Our data suggest that, in LQT1 patients, the well-known positive effect of beta-blockade might be associated with a prolongation of QTc duration. The mechanisms of beta-blockade protection may be different in LQT1 and in LQT2 patients.
在长QT综合征（LQTS）中，β受体阻滞剂治疗对预防心脏事件的效果因基因型而异。我们旨在评估β受体阻滞剂治疗对1型长QT综合征（LQT1）和2型长QT综合征（LQT2）患者QT/QTc间期的影响。
在LQT1患者（n = 30）和LQT2患者（n = 16）开始β受体阻滞剂治疗前后记录24小时动态心电图。在连续的1分钟平均QRS-T复合波上测量QT间期，每个记录最多可得到1440个编辑后的QT-RR对。我们计算了个体和治疗特异性的对数/对数QT/RR关系，用于校正QT间期。还在预定义的心率下以及使用Bazett和Fridericia系数校正后评估QT间期。
基线时，LQT2患者的个体QT/RR系数高于LQT1患者（0.53±0.10对0.40±0.11，P<0.001），LQT2患者的QT1000长于LQT1患者（521±38对481±39毫秒，P<0.01）。β受体阻滞剂显著延长了平均RR间期（从827±161毫秒延长至939±197毫秒，P<0.0001）。β受体阻滞剂对个体QT/RR系数无显著影响。β受体阻滞剂治疗使LQT1患者的QT1000间期延长（从481±39毫秒延长至498±43毫秒，P<0.01），而使LQT2患者的QT1000间期缩短（从521±38毫秒缩短至503±32毫秒，P<0.01）。
β肾上腺素能阻滞剂对LQT1和LQT2患者QTc间期的影响不同。我们的数据表明，在LQT1患者中，β受体阻滞剂众所周知的积极作用可能与QTc间期延长有关。β受体阻滞剂的保护机制在LQT1和LQT2患者中可能不同。
