Clinical outcomes after upgrading from pacemakers to cardiac resynchronization therapy.

BACKGROUND AND AIMS Right ventricular pacing may lead to heart failure (HF). Upgrades from pacemakers to cardiac resynchronization therapy (CRT) were excluded from most randomized, controlled trials. We sought to determine the long-term outcomes of upgrading from pacemakers to CRT with (CRT-D) or without (CRT-P) defibrillation in patients with no history of sustained ventricular arrhythmias. METHODS AND RESULTS In this observational study, clinical events were quantified in relation to the type of implant (de novo or upgrade) and device type at upgrade (CRT-P or CRT-D). Patients underwent CRT implantation (n = 1,545; 1,314 [85%] de novo implants and 231 [15%] upgrades) over a median of 4.6 years [interquartile range: 2.4 - 7.0]). In analyses of crude event rates, upgrades had a higher total mortality (adjusted hazard ratio [aHR]: 1.33; 95% confidence interval [CI] 0.10-1.61), a higher total mortality or HF hospitalization (aHR: 1.26; 95% CI 1.05-1.51), but similar mortality or hospitalization for major adverse cardiac events (MACEs, aHR: 1.15; 95% CI 0.96-1.38). No group differences emerged in any of these endpoints after propensity score matching. After inverse probability weighting in upgrades, total mortality (HR: 0.55; 95% CI 0.36-0.73), total mortality or HF hospitalization (HR: 0.56; 95% CI 0.34-0.79) and total mortality or hospitalization for MACEs (HR: 0.61; 95% CI 0.40-0.82) were lower after CRT-D than after CRT-P. CONCLUSION Upgrading from pacemakers to CRT was associated with a similar long-term risk of mortality and morbidity to de novo CRT. After upgrade, CRT-D was CRT-D was associated with lower mortality than CRT-P. This article is protected by copyright. All rights reserved.