title: Tpeak - Tend and Tpeak - Tend /QT ratio as markers of ventricular arrhythmia risk in cardiac resynchronization therapy patients.
abstract: BACKGROUND
  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 T(peak ) -T(end) (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).
  
  
  METHODS
  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.
  
  
  RESULTS
  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 T(p) T(e) /QT ratio ≥ 0.25 was 3.24 (P = 0.016).
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Medicine, Beth Israel Medical Center, University Hospital and Manhattan Campus for the Albert Einstein College of Medicine, New York, NY, USA.
authors.forename: Chirag
authors.initials: C
authors.lastname: Barbhaiya
authors.forename: Jose Ricardo F
authors.initials: JR
authors.lastname: Po
authors.forename: Sam
authors.initials: S
authors.lastname: Hanon
authors.forename: Paul
authors.initials: P
authors.lastname: Schweitzer
mesh_terms: D000368:Aged; D015415:Biomarkers; D058406:Cardiac Resynchronization Therapy / Q000706:statistics & numerical data*; D015897:Comorbidity; D004562:Electrocardiography / Q000379:methods* / Q000706:statistics & numerical data*; D005260:Female; D006333:Heart Failure / Q000175:diagnosis / Q000453:epidemiology / Q000517:prevention & control; D006801:Humans; D015994:Incidence; D008297:Male; D009518:New York / Q000453:epidemiology; D011379:Prognosis; D015203:Reproducibility of Results; D012307:Risk Factors; D012680:Sensitivity and Specificity; D017180:Tachycardia, Ventricular / Q000175:diagnosis / Q000453:epidemiology* / Q000517:prevention & control*; D016896:Treatment Outcome; D014693:Ventricular Fibrillation / Q000175:diagnosis / Q000453:epidemiology* / Q000517:prevention & control*
chemical_list: D015415:Biomarkers