A Change of Heart: The Effect of High Flow Arteriovenous Fistulas on Cardiovascular Outcomes - a Systematic Review and Synthesis without Meta-analysis (SWiM)

Background: Although arteriovenous fistulas (AVF) are widely accepted as the gold standard form of dialysis access for hemodialysis patients, high AVF flow may impose significant hemodynamic stress, potentially contributing to adverse cardiovascular events, including heart failure (HF). Understanding this relationship is crucial for improving patient care. Aim: To describe the relationship between AVF flow and cardiac outcomes. Methods: A comprehensive search of the PubMed, EMBASE, and Cochrane databases was used to identify observational studies and randomized controlled trials reporting an effect of AVF flow on cardiac outcomes (clinical, echocardiographic, and biomarker). Due to study heterogeneity, meta-analysis was not feasible. Synthesis without meta-analysis (SWiM) was performed using vote counting of direction of effect as the primary outcome. Results: Higher AVF flow rates were consistently associated with increased incidence of HF and worsening HF symptoms. Cardiac imaging revealed left ventricular dilation and reduced left ventricular ejection fraction in patients with high-flow AVFs. Elevated biomarkers, such as natriuretic peptides, corroborated the adverse cardiovascular effects of high AVF flow. Conclusions: This systematic review and synthesis without meta-analysis showed a positive relationship between AVF flow and clinical, echocardiographic, and biomarker cardiovascular outcomes, but an inverse relationship between AVF flow and mortality. The methodological heterogeneity of studies highlights the need for well-designed prospective research with standardised definitions of high flow AVFs and measures for reporting of cardiovascular outcomes.