Fragmented QRS complex as a predictor of appropriate shocks in patients undergoing cardiac resynchronization therapy and defibrillator. A chronicle of a shock foretold?

Abstract Introduction Cardiac resynchronization therapy (CRT) has demonstrated to reduce mortality and hospitalization for heart failure in patients with heart failure with reduced ejection fraction (HFrEF) in specific subgroups of patients Moreover, adding an implantable cardioverter defibrillator (ICD) to CRT (CRT-D) has demonstrated to reduce the risk of sudden cardiac death in specific subgroups of patients. However, patients undergoing CRT-D are a very heterogeneous group. In the recent years, several clinical findings, such as fragmentation of the QRS complex (fQRS), have been reported as potential prognostic factors in various cardiac diseases. Nevertheless, the evidence to support the prognostic significance of fQRS in patients undergoing CRT-D remains to be scarce. Purpose The objective of this study is to evaluate if the presence of pre-implantation fQRS predicts appropriate ICD shocks in patients undergoing CRT-D implantation. Methods Consecutive patients undergoing CRT-D implantation were prospectively included from October 2009 to December 2022. Demographic, clinical, electrocardiographic and echocardiographic variables as well as appropriate ICD shock events were collected from electronic clinical records and telephone interview. Fragmentation of the QRS complex was defined by the presence of different RSR′ patterns including an additional R-wave (R′), notching of the R-wave and S-wave or the presence of more than 1R′ in two contiguous leads corresponding to a main coronary artery territory. Results A total of 180 patients were included. Mean age at the device implantation was 69.9 years (standard deviation, SD ±9.6 years), 80.6% were male, 63.8% presented hypertension and 40.0% were diabetic. The aetiology of the LV systolic dysfunction was non-ischaemic in 45.6% of the patients and ischaemic in 54.6%. 43.9% had prior history of acute myocardial infarction, while myocardial scar was described in 45.6% of the patients. Pre-implantation fQRS was found in 61.7% of the patients. Mean LVEF at baseline was 23.6%. The median follow-up time was 34.8 months. At the end of the follow-up, 30.5% patients died. 9.8% of the patients presented appropriate ICD shocks (9.2% in patients with pre-implantation fQRS and 0.6% in patients without pre-implantation fQRS). A multivariate survival analysis using Cox regression showed that presence of pre-implantation fQRS complex was a powerful independent predictor for appropriate ICD shocks (HR 8.36; 95% CI 1.08–64.32). Kaplan-Meier curves for appropriate shocks regarding pre-implantation fQRS status are presented in Figure 1. Conclusions According to our results, pre-implantation fQRS seems to be a strong independent predictor for appropriate ICD shocks after CRT-D implantation. Therefore, these patients could benefit from a more rigorous follow-up as they present higher risk of an arrhythmic event. However, further research is needed to confirm these findings.Figure 1.Kaplan-Meier curves