Maximizing QRS duration reduction in contemporary cardiac resynchronization therapy is feasible and shorter QRS duration is associated with better clinical outcome

Abstract
Background We aimed to evaluate if optimization by maximizing QRS duration (QRSd) reduction is feasible in an all-comer
cardiac resynchronization therapy (CRT) population, and if reduced, QRSd is associated with a better clinical outcome.
Methods Patients with LBBB receiving CRT implants during the period 2015–2020 were retrospectively evaluated. Implants
from 2015–2017 were designated as controls. Starting from 2018, an active 12-lead electrogram-based optimization of QRSd
reduction was implemented (intervention group). QRSd reduction was evaluated in a structured way at various device AV
and VV settings, aiming to maximize the reduction. The primary endpoint was a composite of heart failure hospitalization
or death from any cause.
Results A total of 254 patients were followed for up to 6 years (median 2.9 [1.8–4.1]), during which 82 patients (32%) reached
the primary endpoint; 53 deaths (21%) and 58 (23%) heart failure hospitalizations. Median QRS duration pre-implant was
162 ms [150–174] and post-implant 146ms [132–160]. Mean reduction in QRS duration was progressively larger for each
year during the intervention period, ranging from − 9.5ms in the control group to − 24 in the year 2020 (p = 0.005). QRS
reduction > 14 ms (median value) was associated with a lower risk of death or heart failure hospitalization (adjusted HR
0.54 [0.29–0.98] (p = 0.04).
Conclusions Implementing a general strategy of CRT device optimization by aiming for shorter QRS duration is feasible
in a structured clinical setting and results in larger reductions in QRS duration post-implant. In patients with a larger QRS
reduction, compared to those with a smaller QRS reduction, there is an association with a better clinical outcome.