Can an Arteriovenous Fistula Clot?
Yes, arteriovenous fistulas can and do clot (thrombose), representing one of the primary causes of vascular access failure in hemodialysis patients. 1, 2
Mechanism and Frequency of AV Fistula Thrombosis
Thrombosis occurs less frequently in AVFs compared to arteriovenous grafts, but remains a significant complication as the number of AVFs has increased in clinical practice. 3
The primary precipitator of thrombosis is stenosis that develops secondary to neointimal hyperplasia, which increases pressure within the access and decreases blood flow. 1
If hemodynamically significant stenosis is left untreated, it will result in thrombosis of the access. 1
Up to 85% of AVF thrombosis cases have an underlying stenosis that must be identified and corrected to prevent rapid re-thrombosis. 2
Clinical Classification
AVF thrombosis falls under the category of "thrombotic flow-related complications or dysfunction," which includes events exclusively related to thrombus formation that causes a clinically important decrease in intra-access flow and threatens the required access patency needed to achieve requisite hemodialysis. 1, 4
Common Sites of Stenosis Leading to Thrombosis
The juxta-anastomotic region in AVFs represents a high-propensity site for stenosis formation (analogous to the vein-graft anastomosis in grafts). 1
Stenotic lesions can occur at any point within the access system, including central veins and feeding arteries, and can provoke access dysfunction regardless of location. 1
Clinical Detection
Heralding signs of impending thrombosis include changes in the access thrill or bruit, prolonged bleeding after decannulation post-dialysis, or arm swelling. 1
As high as 90% of accesses with abnormal physical examinations will have an underlying clinically significant finding on imaging. 1
Regular monitoring through physical examination and surveillance using device-based methods to assess blood access flow rate, access recirculation, and dialysis venous pressure helps detect stenosis before thrombosis occurs. 1
Treatment Urgency
Thrombosed fistulae should be treated as soon as possible after detection to increase the likelihood of successful restoration and avoid temporary catheter placement. 2
AVF function may be successfully reestablished up to one week after thrombosis occurs, but early intervention maximizes success rates. 2
Thrombectomy of a fistula should be attempted as early as possible after thrombosis is detected, but can be successful even after several days. 1
Key Pitfall to Avoid
Failure to identify and treat the underlying stenosis will result in rapid repeat thrombosis after successful thrombectomy, making identification of the causative lesion through fistulography mandatory. 2