Introduction: It remains unclear whether the upgrade cardiac resynchronization therapy (CRT) would show better outcomes than the de-novo CRT. We compared the efficacy of CRT between the de-novo and upgrade groups, especially focused on the effect of upgrade CRT in patients with pacing-induced cardiomyopathy (PiCM).
Methods: The PiCM was defined by the new-onset dilated cardiomyopathy following pacemaker implantation in patients with baseline normal ejection fraction (>50%). Electrico-mechanical reverse remodeling and clinical outcomes were compared among the de-novo (n=62), PiCM upgrade (n=7), and non-PiCM upgrade (n=8) CRT groups.
Results: There were no significant differences between the non-PiCM upgrade and de-novo CRT groups regarding percent decrease in QRS duration and left ventricular end-systolic volume (LVESV) at 6 month follow-up. However, the PiCM upgrade group showed a significantly greater electrico-mechanical reverse remodeling compared to the de-novo CRT or non-PiCM upgrade groups. The rate of super-responder (percent decrease in LVESV>30%) was significantly higher in the PiCM upgrade than the other CRT groups. The group factor of the PiCM upgrade was identified as an independent predictor of super-responder in multivariate analysis (odds ratio, 9.36; 95%CI, 1.01-86.33; p=0.049). During the median follow-up of 15.8 months, composite clinical outcome including cardiac death, heart transplantation, and heart failure-related rehospitalization tends to be better in the PiCM upgrade than the other CRT groups (p=0.157).
Conclusions: The upgrade CRT, especially for the patients with PiCM showed a better performance in terms of electrico-mechanical reverse remodeling and composite clinical outcomes, compared to de-novo CRT or upgrade CRT for non-PiCM patients.