Tpeak – Tend and Tpeak – Tend/QT Ratio as Markers of Ventricular Arrhythmia Risk in Cardiac Resynchronization Therapy Patients
There are no conflicts of interest to report for any author.
Address for reprints: Sam Hanon, M.D., Beth Israel Medical Center, Baird Hall - 5th Floor, 1st Avenue at 16th Street, New York, NY 10003. Fax: 212-420-4222; e-mail: email@example.com
Cardiac resynchronization therapy (CRT) increases transmural dispersion of repolarization (TDR) and can be pro-arrhythmic. However, overall arrhythmia risk was not increased in large-scale CRT clinical trials. Increased TDR as measured by Tpeak –Tend (TpTe) was associated with arrhythmia risk in CRT in a single-center study. This study investigates whether QT interval, TpTe, and TpTe/QT ratio are associated with ventricular arrhythmias in patients with CRT-defibrillator (CRT–D).
Post-CRT–D implant electrocardiograms of 128 patients (age 71.3 years ± 10.3) with at least 2 months of follow-up at our institution's device clinic (mean follow-up of 28.5 months ± 17) were analyzed for QT interval, TpTe, and TpTe/QT ratio. Incidence of ventricular arrhythmias was determined based on routine and directed device interrogations.
Appropriate implantable cardioverter-defibrillator therapy for sustained ventricular tachycardia or ventricular fibrillation was delivered in 18 patients (14%), and nonsustained ventricular tachycardia (NSVT) was detected but did not require therapy in 58 patients (45%). Patients who received appropriate defibrillator therapy had increased TpTe/QT ratio (0.24 ± 0.03 ms vs 0.20 ± 0.04, P = 0.0002) and increased TpTe (105.56 ± 20.36 vs 87.82 ± 22.32 ms, P = 0.002), and patients with NSVT had increased TpTe/QT ratio (0.22 ± 0.04 vs 0.20 ± 0.04, P = 0.016). Increased QT interval was not associated with risk of ventricular arrhythmia. The relative risk for appropriate defibrillator therapy of TpTe /QT ratio ≥ 0.25 was 3.24 (P = 0.016).
Increased TpTe and increased TpTe/QT ratio are associated with increased incidence of ventricular arrhythmias in CRT–D. The utility of TpTe interval and TpTe/QT ratio as potentially modifiable risk factors for ventricular arrhythmias in CRT requires further study.
(PACE 2013; 36:103–108)