Outcomes in pacemaker-dependent patients upgraded from conventional pacemakers to cardiac resynchronization therapy-defibrillators

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.