How to manage a clot in an arteriovenous (AV) fistula in hemodialysis patients?

Management of AV Fistula Thrombosis in Hemodialysis Patients

Endovascular intervention with mechanical thrombectomy and/or pharmacologic thrombolysis combined with balloon angioplasty is the first-line treatment for thrombosed AV fistulas, and should be performed within 24-48 hours of diagnosis to maximize success. 1

Immediate Assessment and Diagnosis

When thrombosis is suspected (absent pulse and thrill on physical examination), confirm the diagnosis through:

• Physical examination showing loss of the continuous thrill and bruit that should normally be present along the fistula 1
• Fluoroscopy fistulography as the primary diagnostic and therapeutic modality, which allows simultaneous identification of underlying stenosis (present in 90% of thrombosis cases) and immediate intervention 1

First-Line Treatment: Endovascular Intervention

The Society of Interventional Radiology guidelines establish endovascular management as superior to open surgery for first-line therapy of dialysis access thrombosis. 1

Endovascular Techniques Include:

• Mechanical thrombectomy (suction thrombectomy, balloon thrombectomy, or clot maceration) 1
• Pharmacologic thrombolysis using tissue plasminogen activator (TPA) or alteplase 1
• Balloon angioplasty to treat the underlying stenosis (critical step—failure to address stenosis results in rapid re-thrombosis) 1
• Stent placement if needed for elastic recoil after angioplasty 1

Expected Outcomes:

• Clinical success rate: 75-94% 1
• 6-month primary patency: 18-39% 1
• 6-month secondary patency: 62-80% 1

Critical Timing

Intervention must occur within 24-48 hours of thrombosis diagnosis whenever achievable. 1 Delays beyond this window necessitate temporary catheter placement, which increases infection risk and mortality. The placement of more than one temporary femoral catheter while awaiting thrombosis correction is unwarranted. 1

When to Escalate to Surgery

Surgical consultation for access revision or creation of a new fistula is indicated when: 1

• Endovascular treatment fails clinically
• Thrombosis recurs >2 times within a single month 1
• Recurrent correctable stenosis is identified in the circuit 1
• Aneurysms or pseudoaneurysms are present, which contain chronic intraluminal thrombus difficult to access endovascularly 1

For complex cases with aneurysmal regions, surgical thrombectomy with manual "milking" of thrombus from the access lumen achieves complete clot extraction in 95% of cases. 1

Addressing Underlying Causes

Since 90% of access thromboses are secondary to anatomic stenosis, fistulography must be performed rapidly to identify and correct the stenosis. 1 Failure to address underlying stenosis results in rapid re-thrombosis. 1

Other precipitating factors to evaluate: 1

• Hypotension post-hemodialysis
• Hypercoagulable states (consider thrombophilia testing in recurrent cases) 1
• Decreased cardiac output
• Access site infection 1

Temporary Access Management

If endovascular declotting fails, place a tunneled cuffed dialysis catheter for interim hemodialysis access (acceptable for <3 months duration). 1 Place the catheter in the extremity opposite to the one anticipated for AV access revision to preserve vasculature. 1

For urgent situations where AV access is expected to be ready short-term, a tunneled cuffed femoral catheter is acceptable until the AV access is usable, preserving upper extremity vasculature. 1

Special Considerations for Native AV Fistulas

Thrombosis of native AV fistulas is more difficult to treat than AV graft thrombosis, with neither percutaneous nor surgical techniques offering consistently good results. 1 Each institution should attempt resolution with their preferred technique, but expectations for success should be tempered compared to graft thrombectomy. 1

Common Pitfalls to Avoid

• Delaying intervention beyond 48 hours, which decreases success rates and necessitates temporary catheter placement 1, 2
• Failing to identify and treat underlying stenosis during thrombectomy, leading to immediate re-thrombosis 1
• Applying vigorous suction or excessive pressure during catheter manipulation, which can damage the vascular wall or expel clot into circulation 3
• Placing multiple temporary catheters while awaiting definitive treatment, increasing infection risk 1
• Ignoring hypercoagulable workup in patients with recurrent thrombosis (>2 episodes per month) 1