Antibradycardia pacing in patients with reduced ejection fraction: is CRT really the best option?

Introduction Cardiac resynchronization therapy (CRT) is recommended for patients with LVEV < 40% regardless of NYHA class who have an indication for ventricular pacing and high-degree AV block. The response of these patients when compared to patients with a formal indication for CRT remains uncertain. Objectives To characterize patients undergoing CRT based on requirement of antibradycardia pacing (Required vs Not Required) and evaluate differences in LV remodeling, outcomes and survival between these groups. Methods A retrospective analysis between 2020-2023 included 95 patients who underwent CRT-P/CRT-D implantation. Data included demographics, cardiovascular risk factors, etiology, medical therapy, echocardiographic and electrocardiographic parameters, and documented arrhythmias. Outcomes analyzed comprised hospitalization for heart failure, myocardial infarction, stroke or death. Results The study included 74 patients, of whom 21 (28.4%) had indication for antibradycardia pacing. The mean age was 69.5±10.4 years, and 75.8% were male. Patients requiring antibradycardia pacing had higher prevalence of hypertension (85.7% vs 60.4%, p=0.036) and atrial fibri lation (52.4% vs 24.5%, p=0.021), and patients without indication for pacing were more smokers (14.3% vs 45.3%, p=0.013) and had higher prevalence of use od beta-blockers and mineralocorticoids receptors antagonists. Patients requiring antybradycardia pacing had higher LVEF at baseline (39.1% vs 32.8%, p= 0.013) but less LVEF improvement after CRT implantation (LVEF pre 39.1% and LVEF pos 39.4%, p=0.954) and less LV remodeling (TDV pre 201ml and TDV pos 167m, p=0.132), when compared to patients without need for pacing (LVEF pre 32.8% and LVEF pos 39.4%, p=0.031) and (TDV pre 193ml and TDV pos 151ml, p=0.106). No significant differences in composite outcomes or survival were observed between the groups over 35-months folow-up. Conclusion Patients with non-preserved LVEF with indication for antibradycardia pacing exhibited less pronounced reverse remodeling (lower LVEF end TDV improvement) folowing CRT implantation, compared to patients with formal indication for resynchronization, although without differences in hard outcomes. The results of the study highlight the possibility of new pacing strategies in these patients, like conduction system pacing.