#2010 Association between blood flow (Qa) monitored over time by ultrasound and the risk of thrombosis in autologous and prosthetic AV accesses

Abstract Background and Aims The use of arteriovenous (AV) access for hemodialysis is hampered by the risk of thrombosis. This study aims to investigate the association between repeated ultrasound measurement of blood flow (Qa) and its percentage variation with thrombosis risk, in distal and proximal autologous AV fistulae (dAVF and pAVF) and AV grafts (AVG). Method This retrospective cohort study included all AV accesses created through the multidisciplinary AV access team in our centers in Milan (IT), between 2013 and 2024. Accesses with a post-operative Qa measurement within 30 days from creation were included and followed up until the first thrombosis, study end, or patient death. Qa was measured as the product of the cross-sectional area and the time-averaged mean velocity in the brachial artery. The associations of interest were studied by time-dependent Cox models, adjusted for patient's age, sex, and comorbidities, using splines for non-linear effects. Results A total of 224 AV accesses (88 dAVF, 88 pAVF, and 48 AVG) were created in 197 patients. At first post-operative visit, median Qa was 935, 1260, and 1665 ml/min, respectively for dAVF, pAVF, and AVG. Thereafter, Qa increased in all access types in the first 3–6 months, and then kept on slowly increasing only in pAVF. During a median follow up of 1.05 [0.24, 2.34] years, 70 AV access thrombosis occurred. In dAVF, we found a significant L-shaped association between longitudinal Qa and thrombosis risk. For dAVF with Qa < 1500 ml/min, the risk of thrombosis increased by 34% every 100 ml/min decrease in Qa (aHR 1.34, 95% CI 1.11–1.62, p 0.002). In pAVF, longitudinal Qa showed an inverse linear association with thrombosis risk (aHR 1.14, 95% CI 1.05–1.23, p 0.002, for every 100 ml/min decrease in Qa) (Fig. 1). In AVG, Qa was not associated with thrombosis. The percentage change in Qa was not linked with thrombotic events in any type of access (Fig. 2). Conclusion In our cohort, longitudinal Qa was associated with thrombosis risk in dAVF and pAVF, but not in AVG. Its percentage variation did not seem associated with increased thrombosis risk in any access type. Qa surveillance by ultrasound may be a useful tool to identify dAVF and pAVF at higher risk of thrombosis and allow a closer monitoring or preventive interventions.