Atrial Fibrillation and HFrEF: Cause, Consequence, or Both?

Background/Objectives: Atrial fibrillation (AF) and heart failure with reduced ejection fraction (HFrEF) frequently coexist and are linked by shared risk factors and pathophysiological mechanisms. Their association is consistently related to worse clinical outcomes. This narrative review summarizes current evidence regarding the epidemiology, pathophysiology, management strategies, and prognosis of patients with AF and HFrEF. Methods: This is a narrative review based on published randomized trials, registries, and observational studies evaluating the interaction between AF and HFrEF, with a focus on therapeutic strategies including rate and rhythm control, catheter ablation, stroke prevention, and guideline-directed medical therapy. Results: AF and HFrEF have a bidirectional relationship, with each condition promoting the development and progression of the other. AF contributes to hemodynamic impairment and adverse remodeling, while HFrEF promotes atrial structural and electrical changes. Management remains complex. Rate control is commonly achieved with beta-blockers and digoxin, while rhythm control is limited by the safety profile of antiarrhythmic drugs. Catheter ablation has shown improvements in left ventricular function and, in selected patients, reductions in hospitalizations and mortality, although results are not consistent across all trials. Guideline-directed medical therapy improves outcomes in HFrEF, but its interaction with AF varies across drug classes. Stroke risk is significantly increased, requiring appropriate anticoagulation. Patients with AF and HFrEF have an increased risk of mortality, hospitalization, and adverse clinical events compared with those with either condition alone, although the extent to which these outcomes are attributable to AF itself, HF severity, or the associated comorbidity burden remains uncertain. Conclusions: The coexistence of AF and HFrEF identifies a high-risk population with complex management and unfavorable outcomes. While advances in rhythm control and heart failure therapies have improved selected outcomes, optimal treatment strategies and their impact on long-term prognosis remain incompletely defined.