Long-term mortality in cardiac resynchronization therapy upgrade procedures compared with de novo implantations - a nationwide cohort study
Authors: Bjerre H L , Frausing M H J P , Johansen J B , Riahi S , Philbert B T , Haarbo J , Nielsen J C , Kronborg M B 
Published: May 2023

Abstract

Funding Acknowledgements
Type of funding sources: Private grant(s) and/or Sponsorship. Main funding source(s): Danish Cardiovascular Academy

Background
Patients with an implanted pacemaker (PM) or implantable cardioverter-defibrillator (ICD) who develop heart failure (HF) and have frequent right ventricular (RV) pacing, may be upgraded to a Cardiac Resynchronization Therapy (CRT) device. Such upgrades constitute approximately one fourth of CRT implantations. Limited research has been devoted to long-term outcomes after upgrade implantations and diverging results have been reported.

Purpose
We aimed to investigate long-term mortality in patients undergoing upgrade to CRT after previous PM or ICD implantation and patients undergoing CRT de novo implantation.

Methods
This was a nationwide register-based cohort study. The patient cohort was identified via the Danish Pacemaker and ICD Registry and consisted of consecutive Danish patients undergoing a CRT de novo implantation or an upgrade to CRT, from 01.01.2000 to 31.08.2018. Upgrade from a CRT pacemaker to a CRT defibrillator, and simple device replacement procedures were not included. Data were cross-linked with the Danish Patient Registry via the unique central person registration number. The endpoint was total mortality. Unadjusted- and adjusted Cox proportional hazard regression was used to assess the association between the procedure type (upgrade or de novo), baseline characteristics and total mortality.

Results
We identified 8,880 patients of whom 6,685 (75.3%) underwent de novo CRT implantation and 2,195 (24.7%) underwent upgrade to CRT from a previous PM or ICD. The median (IQR) follow-up time was 3.9 years (5.3) and 4.6 years (4.3) for upgrade and de novo implantations respectively. At baseline, patients who underwent upgrade to CRT were older (median 71.9 vs. 69.3 years) and more likely to have ischemic heart disease (66.8% vs. 57.1%), atrial fibrillation or atrial flutter (57.5% vs. 33.4%) and chronic kidney disease (10.3% vs. 7.2%) compared to patients who had de novo implantation. The proportion of males was larger among patients who underwent upgrade to CRT compared to de novo implantation (84.1% vs. 74.9%). Upgrade implantations were associated with higher minimally adjusted (age and sex) total mortality (HR 1.13, [95% CI 1.05;1.21], p&lt;0.001) compared to de novo implantations. There was no difference in total mortality between upgrade and de novo implantations after adjusting for age, sex, diabetes, hypertension, chronic ischemic heart disease, atrial fibrillation or atrial flutter, chronic obstructive pulmonary disease, and chronic kidney disease (HR 1.03, [95% CI 0.96;1.10], p=0.46).

Conclusion
There are major differences in co-morbidities among patients undergoing upgrade to CRT and patients undergoing CRT de novo implantation. When adjusting for these differences, there was no difference in total mortality between the two populations. This suggests that CRT is equally beneficial in both de novo and upgrade implantations.