Monthly access flow monitoring with increased prophylactic angioplasty did not improve fistula patency

Abstract

Regular access monitoring is recommended to detect and treat access stenosis in order to prevent access thrombosis and failure. In 1999, we instituted monthly access blood flow monitoring using the ultrasound dilution technique (UDT). In a sequential observational trial, 222 patients were studied for the impact of UDT monitoring on patency of their first arteriovenous autogenous fistula. Group 1, the historic group (before 1999), had 146 arteriovenous fistulas (50.7% upper arm), followed for 259 access-years. Group 2, the UDT-monitored group, had 76 arteriovenous fistulas (60.5% upper arm), followed for 123 access-years. Decision to refer for angiography was based on clinical criteria for group 1, and clinical criteria plus results of UDT flow monitoring in group 2. Cumulative patency was longer (P < 0.01) and the thrombosis rate was lower (P < 0.05) in group 2. However, the improvement occurred prior to initiation of UDT flow monitoring. Comparing outcomes in group 2 patients whose fistula survived to start flow monitoring with group 1 patients whose fistula survived at least 160 days (the median time to starting UDT monitoring in group 2), there was a sevenfold increase in angioplasty procedures (0.67 vs. 0.09 per access-year) but no improvement in the thrombosis rate or cumulative fistula patency. UDT monitoring increased the rate of angioplasty procedures and thereby shortened primary unassisted patency, but did not decrease the thrombosis rate or improve cumulative fistula patency.