title: Is CRT pro-arrhythmic? A comparative analysis of the occurrence of ventricular arrhythmias between patients implanted with CRTs and ICDs.
abstract: Aim and Hypothesis: Despite the proven symptomatic and mortality benefit of cardiac resynchronization therapy (CRT), there is anecdotal evidence it may be pro-arrhythmic in some patients. We aimed to identify if there were significant differences in the incidence of ventricular arrhythmias (VAs) in patients undergoing CRT-D and implantable cardioverter-defibrillators (ICD) implantation for primary prevention indication. We hypothesized that CRT is unlikely to be pro-arrhythmic based on the positive mortality and morbidity data from large randomized trials.
  
  
  RESULTS
  A retrospective analysis of device therapies for VA in a primary prevention device cohort was performed. Patients with ischemic (IHD) and non-ischemic (DCM) cardiomyopathy and ICD or CRT+ICD devices (CRT-D) implanted between 2005 and 2007 without prior history of sustained VA were included for analysis. VA episodes were identified from stored electrograms and defined as sustained (VT/VF) if therapy [anti-tachycardia pacing (ATP) or shocks] was delivered or non-sustained (NSVT) if not. Of a total of 180 patients, 117 (68% male) were in the CRT-D group, 42% IHD, ejection fraction (EF) 24.5 ± 8.2% and mean follow-up 23.9 ± 9.8 months. 63 patients (84% male) were in the ICD group, 60% IHD, EF 27.7 ± 7.2% and mean follow-up 24.6 ± 10.8 months. Overall, there was no significant difference in the incidence of VA (35.0 vs. 38.1%, p = 0.74), sustained VT (21.3 vs. 28.5%, p = 0.36) or NSVT (12.8 vs. 9.5%, p = 0.63) and no significant difference in type of therapy received for VT/VF: ATP (68 vs. 66.6%, p = 0.73) and shocks (32 vs. 33.3%, p = 0.71) between the CRT-D and ICD groups, respectively.
  
  
  CONCLUSIONS
  In patients with cardiomyopathy receiving CRT-D and ICDs for primary prophylaxis, there was no significant difference in the incidence of VA. From this single center retrospective analysis, there is no evidence to support cardiac resynchronization causing pro-arrhythmia.
authors.affiliation: Department of Cardiac Electrophysiology, The Heart Hospital, Institute of Cardiovascular Sciences, University College London UK.
authors.forename: A B
authors.initials: AB
authors.lastname: Gopalamurugan
authors.affiliation: Department of Cardiac Electrophysiology, The Heart Hospital, Institute of Cardiovascular Sciences, University College London UK.
authors.forename: G
authors.initials: G
authors.lastname: Ganesha Babu
authors.affiliation: Department of Cardiac Electrophysiology, The Heart Hospital, Institute of Cardiovascular Sciences, University College London UK.
authors.forename: Dominic P
authors.initials: DP
authors.lastname: Rogers
authors.affiliation: Department of Cardiac Electrophysiology, The Heart Hospital, Institute of Cardiovascular Sciences, University College London UK.
authors.forename: Adam L
authors.initials: AL
authors.lastname: Simpson
authors.affiliation: Department of Cardiac Electrophysiology, The Heart Hospital, Institute of Cardiovascular Sciences, University College London UK.
authors.forename: Syed Y
authors.initials: SY
authors.lastname: Ahsan
authors.affiliation: Department of Cardiac Electrophysiology, The Heart Hospital, Institute of Cardiovascular Sciences, University College London UK.
authors.forename: Pier D
authors.initials: PD
authors.lastname: Lambiase
authors.affiliation: Department of Cardiac Electrophysiology, The Heart Hospital, Institute of Cardiovascular Sciences, University College London UK.
authors.forename: Anthony W
authors.initials: AW
authors.lastname: Chow
authors.affiliation: Department of Cardiac Electrophysiology, The Heart Hospital, Institute of Cardiovascular Sciences, University College London UK.
authors.forename: Martin D
authors.initials: MD
authors.lastname: Lowe
authors.affiliation: Department of Cardiac Electrophysiology, The Heart Hospital, Institute of Cardiovascular Sciences, University College London UK.
authors.forename: Edward
authors.initials: E
authors.lastname: Rowland
authors.affiliation: Department of Cardiac Electrophysiology, The Heart Hospital, Institute of Cardiovascular Sciences, University College London UK.
authors.forename: Oliver R
authors.initials: OR
authors.lastname: Segal
keywords: ICD; cardiac resynchronization therapy; heart failure; ventricular arrhythmia