title: Outcomes in pacemaker-dependent patients upgraded from conventional pacemakers to cardiac resynchronization therapy-defibrillators.
abstract: BACKGROUND
  Pacemaker-dependent patients with left ventricular dysfunction benefit from upgrade to cardiac resynchronization therapy (CRT). Those at low risk for ventricular tachyarrhythmias may benefit similarly from upgrade to a CRT-defibrillator or CRT-pacemaker.
  
  
  OBJECTIVE
  To determine whether coronary artery disease (CAD), because of associated scar that supports reentry, predicts higher risk of appropriate shocks in pacemaker-dependent patients upgraded to a CRT-defibrillator.
  
  
  METHODS
  We grouped 157 pacemaker-dependent patients with left ventricular ejection fraction (LVEF) ≤35%, no prior sustained ventricular arrhythmias, and conventional pacemakers upgraded to CRT-defibrillators according to the presence (n = 75) or absence (n = 82) of significant CAD. Overall survival, risk of appropriate shocks and antitachycardia pacing, complications related to high-power system components, and LVEF and end-systolic volume changes were contrasted between groups.
  
  
  RESULTS
  Patients with CAD had more comorbidities and exhibited increased mortality during a follow-up of 59 ± 30 months (hazard ratio 2.55; 95% confidence interval 1.49-4.36; P = .001). Of 12 patients with appropriate shocks, 11 had CAD. Time to first shock, antitachycardia pacing, and tachyarrhythmia therapy were significantly shorter in patients with CAD (P < .01). The risk of an appropriate shock in patients without CAD was 1 per 362 person-years compared with 1 shock per 26 person-years in patients with CAD. Complications specific to high-energy device components necessitated another procedure in 32 (20%) patients. LVEF improvement and end-systolic volume reduction were similar between groups.
  
  
  CONCLUSIONS
  Among pacemaker-dependent patients with no prior ventricular arrhythmias upgraded from a pacemaker to a CRT-defibrillator, patients without significant CAD have fewer comorbidities, longer survival, and low risk of appropriate shocks than do patients with CAD. CRT-pacemakers may be appropriate in such patients without CAD.
authors.affiliation: University of Pittsburgh Heart and Vascular Institute, Pittsburgh, Pennsylvania. Electronic address: adelsteinec@upmc.edu.
authors.forename: Evan
authors.initials: E
authors.lastname: Adelstein
authors.affiliation: University of Pittsburgh Heart and Vascular Institute, Pittsburgh, Pennsylvania.
authors.forename: David
authors.initials: D
authors.lastname: Schwartzman
authors.affiliation: University of Pittsburgh Heart and Vascular Institute, Pittsburgh, Pennsylvania.
authors.forename: Raveen
authors.initials: R
authors.lastname: Bazaz
authors.affiliation: University of Pittsburgh Heart and Vascular Institute, Pittsburgh, Pennsylvania.
authors.forename: Sandeep
authors.initials: S
authors.lastname: Jain
authors.affiliation: University of Pittsburgh Heart and Vascular Institute, Pittsburgh, Pennsylvania.
authors.forename: John
authors.initials: J
authors.lastname: Gorcsan
authors.affiliation: University of Pittsburgh Heart and Vascular Institute, Pittsburgh, Pennsylvania.
authors.forename: Samir
authors.initials: S
authors.lastname: Saba
mesh_terms: D000368:Aged; D001281:Atrial Fibrillation / Q000453:epidemiology / Q000401:mortality / Q000628:therapy*; D058406:Cardiac Resynchronization Therapy; D015897:Comorbidity; D003324:Coronary Artery Disease / Q000453:epidemiology; D017147:Defibrillators, Implantable; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010138:Pacemaker, Artificial; D018487:Ventricular Dysfunction, Left
keywords: Cardiac resynchronization therapy; Coronary artery disease; Implantable cardioverter-defibrillators; Pacemakers