Tabatabaei Peyman, Keikhavani Ala, Haghjoo Majid, Fazelifar Amirfarjam, Emkanjoo Zahra, Zeighami Mahbobeh, Bakhshandeh Hooman, Ghadrdoost Behshid, Alizadeh Abolfath
Cardiac Electrophysiology Research Center, Rajaie Cardiovascular Medical and Research Center, Iran University of Medical Sciences, Tehran, IR Iran.
Department of Cardiology, Ziaeian General Hospital, International Campus Medical School, Tehran University of Medical Sciences, Tehran, IR Iran.
Res Cardiovasc Med. 2016 Mar 5;5(2):e31528. doi: 10.5812/cardiovascmed.31528. eCollection 2016 May.
Prolongation of the QT interval is considered a risk factor for cardiac adverse events and mortality. Left bundle branch block (LBBB) lengthens the QT interval. The corrected QT interval (QTc) is most likely overestimated because its prolongation is caused by increases in depolarization duration and not in repolarization.
In this study, we aimed to apply corrected JT interval (JTc) as an appropriate measure of ventricular repolarization for predicting QTc in a formula.
The study population consisted of 101 patients with sinus rhythm (SR) and narrow QRS complexes (< 120 milliseconds). All patients underwent electrophysiology studies or ablation. A diagnostic catheter was positioned in the right ventricular apex (RVA) to induce LBBB at two different cycle lengths (CLs; 600 and 700 mv). The intrinsic QRS complex, QT time, and JT time were measured during SR and subsequent RVA pacing. The JTc was derived simply by subtracting the QRS duration from the QTc.
Stimulation from the RVA increased the QTc from 456.20 ± 38.63 ms to 530.67 ± 47.73 ms at a CL of 600 (P < 0.0001) and to 502.32 ± 47.26 ms at 700 CL (P < 0.0001). JTc showed no significant changes with stimulation from the RVA (102.97 ± 11.35 ms vs. 103.59 ± 10.67 ms, P = 0.24). There was no significant correlation between JTc and QRS complex duration. A significant correlation was seen between QRS and QTc at both CLs. The ROC curve indicated that sensitivity of 80% and specificity of 67% were obtained with JTc duration of 92.6 ms.
Right ventricular pacing increases the QT interval without increasing the JT interval. Our results confirm that JTc, as an index of repolarization, is independent of ventricular depolarization. Therefore, it can be applied for predicting QTc in patients with LBBB.
QT间期延长被认为是心脏不良事件和死亡的危险因素。左束支传导阻滞（LBBB）会延长QT间期。校正QT间期（QTc）很可能被高估，因为其延长是由去极化持续时间增加而非复极化增加所致。
在本研究中，我们旨在应用校正JT间期（JTc）作为心室复极化的合适指标，以通过公式预测QTc。
研究人群包括101例窦性心律（SR）且QRS波群时限狭窄（<120毫秒）的患者。所有患者均接受了电生理研究或消融治疗。将诊断导管置于右心室尖部（RVA），以两种不同的周期长度（CLs；600和700毫秒）诱发LBBB。在窦性心律及随后的RVA起搏期间测量固有QRS波群、QT时间和JT时间。JTc通过简单地从QTc中减去QRS时限得出。
在CL为600时，来自RVA的刺激使QTc从456.20±38.63毫秒增加到530.67±47.
