Impact of QRS complex fragmentation on all-cause mortality before and after cardiac resynchronization therapy
Authors: Rodriguez-Lopez C , De Miguel Garcia L , Garcia Talavera C S , Cortes Garcia M , Balaguer German J , Romero Otero J M , Venegas Rodriguez A M , Acena A , Pello Lazaro A M , Lazaro Rivera C , Diaz Cortegana F , Calero Bravo L , Aguilera Agudo C , Tunon Fernandez J , Rubio Campal J M 
Published: October 2024

Abstract

Introduction
Cardiac resynchronization therapy (CRT) have demonstrated to reduce all-cause mortality in selected patients with HFrEF. However, there is still a high rate of non-responders, so risk stratification is crucial. Fragmentation of the QRS complex (QRSf) has been suggested as a valuable prognostic factor in different cardiac diseases, but the evidence in patients undergoing CRT is controversial and limited.

Purpose
To evaluate if changes in QRSf status before and after CRT implantation has a prognostic role in patients undergoing CRT in terms all-cause mortality.

Methods
Consecutive patients undergoing CRT were prospectively included from October 2009 to December 2022. Demographic clinical, electrocardiographic and echocardiographic variables were recorded. Prospective follow-up variables were collected from electronic clinical records and telephone interview. QRSf complex was defined by the presence of different RSR′ patterns including additional R-waves (R′) and notches of the R-wave and S-wave in two contiguous leads corresponding to a main coronary artery territory in a 12-lead electrocardiogram performed before and after CRT.

Results
A total of 244 patients (mean age 71.8 ± 9.8 years, 79.5% male) were included. The etiology of LV systolic disfunction was ischemic in 50.0%. Mean LVEF before implantation was 25 ± 9%. A CRT-D was implanted in 176 patients (72.2%). The mean width of the paced QRS was 141 ± 23 ms. At baseline, 150 patients had a QRSf. After CRT implantation, 69 (28.4%) patients experimented a change in QRSf status: 29 patients (11.9%) without prior QRSf developed QRSf, whereas 40 patients (16.5%) resolved QRSf after CRT. Median follow-up time was 36.0 months (interquartile range 18.2-75.7). During the follow-up period, 90 patients died. In the multivariate Cox regression survival analysis, the presence of QRSf before the implantation with or without paced QRSf after CRT were independently associated with all-cause mortality (HR 4.43; 95% CI 1.53-12.80 and HR 3.69; 95% CI 1.16-11.80 respectively). Those without QRSf prior implantation who developed QRSf after CRT did not present significantly higher risk of all-cause mortality. Univariate and multivariate Cox regression analyses for all-cause mortality are presented in Table 1. Figure 1 presents Kaplan-Meier curves for all-cause mortality according to QRSf status before and after CRT implantation.

Conclusions
According to our results, preimplantation QRSf is an independent predictor of all-cause mortality regardless the resolution or maintenance of QRSf after CRT in patients with HFrEF undergoing CRT. Therefore, patients with QRSf before CRT implantation regardless the paced QRSf status, should be followed more strictly because they are at higher mortality risk.Table 1.Cox Regression Analyses