Supplementary Material for: Association between blood flow measured within 30 days from AV access creation and thrombosis risk

Introduction: Arteriovenous (AV) hemodialysis accesses are hampered by the risk of thrombosis. Due to lack of evidence, current guidelines do not suggest routine assessment of AV access blood flow (Qa) for surveillance. This study aims to analyze the association between post-operative Qa and thrombosis risk, in distal and proximal autologous AV fistulae (dAVF, and pAVF), and AV grafts (AVG).
Methods: This retrospective cohort study included all AV accesses created in San Paolo Hospital (Milan, IT) between 2013 and 2022, with a post-operative Qa measurement available within 30 days from creation. Thrombosis-free survival curves were plotted using the Kaplan-Meier method. The association between Qa and thrombosis risk was studied by multivariate Cox proportional hazard models. Non-linearity was assessed using natural splines.
Results: A total of 218 AV accesses (92 dAVF, 76 pAVF, and 50 AVG) were created in 191 patients. During a median follow-up time of 1.35 years, 66 AV access thrombosis occurred. In dAVF, Qa showed a significant non-linear association with thrombosis risk, with nadir at Qa of 1289 ml/min and an exponential risk increase for Qa <800 ml/min. In dAVF with a Qa<1289 ml/min, there was a 43% increase in the risk of thrombosis every 100 ml/min decrease in Qa (aHR 1.43 [1.11-1.83], p 0.005). In pAVF and AVG, Qa was not associated with thrombosis risk.
Conclusion: Post-operative Qa shows a non-linear association with thrombosis risk in dAVF, suggesting that this may be a useful tool to identify high-risk dAVF allowing closer surveillance or preventive interventions.