Residency · Residency · Interventional Radiology

Dialysis Graft and Fistula Thrombosis: Declot Procedures

Introduction

Thrombosis of arteriovenous grafts (AVGs) and arteriovenous fistulae (AVFs) is a leading cause of dialysis access dysfunction and accounts for significant morbidity, catheter placement, and healthcare utilization. Percutaneous declot procedures performed by interventional radiologists restore access patency and reduce the need for new access creation or temporary catheter dependence.

Epidemiology and Pathophysiology

AVG thrombosis rates: 0.5-2.0 events per patient-year; AVF thrombosis rates are significantly lower. The most common underlying cause is venous outflow stenosis (80-90% of cases). Progressive stenosis reduces flow, promoting stasis and thrombus formation. Additional contributing factors: hypotension (during or after dialysis), excessive compression post-dialysis, hypercoagulable states, dehydration. Early declot (within 48 hours of thrombosis) yields the highest success rates.

Clinical Assessment

Absent thrill and bruit on physical examination indicate thrombosis. Palpation may reveal a firm, non-compressible cord along the graft or fistula. Failure to cannulate or poor dialysis flows should prompt urgent evaluation. Duplex ultrasound confirms thrombosis and identifies underlying stenosis. Evaluate for central venous stenosis if arm or facial swelling is present.

Declot Techniques

Pharmacomechanical Thrombolysis

Combination of thrombolytic agents and mechanical disruption. Infuse tissue plasminogen activator (tPA) or alteplase (2-4 mg) directly into the thrombus. Allow dwell time (15-30 minutes) or use pulse-spray technique for faster lysis. Follow with balloon maceration and aspiration of residual thrombus. Particularly effective for AVFs with organized thrombus.

Mechanical Thrombectomy

Preferred for AVGs due to typically soft, fresh thrombus. Percutaneous thrombectomy devices: Arrow-Trerotola, AngioJet, ClotTriever. The Arrow-Trerotola PTD uses a rotating basket to fragment thrombus mechanically. AngioJet: rheolytic thrombectomy using Bernoulli effect to aspirate fragmented clot. Balloon sweep technique: inflate angioplasty balloon and sweep thrombus toward the venous anastomosis for aspiration.

Surgical Thrombectomy

Open surgical approach with Fogarty balloon catheter thrombectomy. Often combined with patch angioplasty or revision of the venous anastomosis. Generally reserved when percutaneous methods fail or are not available.

Procedural Steps: Percutaneous Declot

Access and Setup

Position the arm on an arm board; prep and drape the access. Access the graft/fistula with a micropuncture set at two sites: one directed toward the arterial anastomosis, one toward the venous outflow. Perform initial fistulography to confirm thrombosis extent and identify underlying stenosis. Administer heparin (3000-5000 units) systemically.

Thrombus Removal

Clear the venous limb first using thrombectomy device or pharmacomechanical technique. Address the arterial plug (organized thrombus at the arterial anastomosis) using Fogarty balloon, aspiration catheter, or pulse-spray thrombolysis. Perform angiography to confirm thrombus clearance and assess flow.

Treating the Underlying Stenosis

Identify and treat underlying venous outflow stenosis with angioplasty (high-pressure balloon). Consider stent graft placement for recurrent or elastic stenoses at the venous anastomosis of AVGs. Evaluate the entire outflow including central veins; treat any significant stenoses.

Completion

Confirm adequate flow with completion angiography: no residual stenosis > 30%, brisk flow to central veins. Confirm return of thrill on palpation. Coordinate with dialysis unit for same-day or next-day use.

Complications

Pulmonary embolism: small thrombus fragments commonly embolize to the lungs; usually clinically insignificant. Vessel rupture: from aggressive angioplasty; manage with prolonged balloon inflation or covered stent. Arterial embolization: dislodged arterial plug can embolize distally; retrieve with aspiration or surgical embolectomy. Access site bleeding: manage with manual compression. Re-thrombosis: early re-thrombosis suggests untreated stenosis or inadequate thrombus removal.

Outcomes and Surveillance

Technical success rate: 85-95% for AVGs; 70-85% for AVFs. Primary patency at 3 months: approximately 40-60% for AVGs; higher for AVFs. Assisted primary patency improves with scheduled surveillance and re-intervention. KDOQI recommends monitoring with access flow measurements and clinical examination. Declining flow rates or elevated venous pressures should prompt fistulography before thrombosis occurs.

Key Clinical Pearls

Venous outflow stenosis is the underlying cause of thrombosis in 80-90% of cases; always treat it during declot. Early intervention within 48 hours of thrombosis yields the best outcomes. The arterial plug is often the most challenging component; use focused techniques to clear it completely. Small pulmonary emboli during declot are common and usually clinically silent. Post-declot surveillance with regular flow monitoring is essential to prevent recurrent thrombosis.

References

1. Vesely TM, Siegel JB. Use of the Peripheral Cutting Balloon to Treat Hemodialysis-Related Stenoses. Journal of Vascular and Interventional Radiology. 2005;16(12):1593-1603.
2. Trerotola SO, Stavropoulos SW, Shlansky-Goldberg R, et al. Hemodialysis-Related Venous Stenosis: Treatment with Ultrahigh-Pressure Angioplasty Balloons. Radiology. 2004;231(1):259-262.
3. National Kidney Foundation. KDOQI Clinical Practice Guideline for Vascular Access: 2019 Update. American Journal of Kidney Diseases. 2020;75(4 Suppl 2):S1-S164.
4. Beathard GA. Mechanical versus Pharmacomechanical Thrombolysis for the Treatment of Thrombosed Dialysis Access Grafts. Kidney International. 1994;45(5):1401-1406.

For the intern

When the dialysis unit calls at 3am about a thrombosed access, confirm the diagnosis (absent thrill, firm cord) and ensure the patient is stable. Check if the patient has dialysis scheduled soon—if they need dialysis within 24 hours or are symptomatic (chest pain, severe fluid overload), the declot is urgent and should be scheduled first-thing in the morning or notify the IR attending immediately. If dialysis isn't urgently needed and the patient is stable, this can wait until regular business hours, but don't delay beyond 48 hours as success rates drop significantly. Document the time of thrombosis and ensure adequate IV access is available.

Common pitfalls

• Forgetting to treat the underlying stenosis: Clearing the clot without addressing the venous outflow stenosis (present in 80-90% of cases) leads to immediate re-thrombosis. Always perform completion angiography and angioplasty.
• Inadequate arterial plug removal: The organized thrombus at the arterial anastomosis is often resistant to standard techniques. If you don't completely clear it, the access will fail immediately.
• Premature celebration: Just because flow is restored doesn't mean you're done. Confirm there's no residual stenosis >30% and verify a palpable thrill before ending the procedure.
• Neglecting central veins: Always image the central venous outflow. Central stenosis causes recurrent thrombosis and arm swelling but is easily missed if you don't look for it.

Make it stick

Imagine you’re on call, the pager buzzes at 2 AM. It's the dialysis unit: "Mr. Jones' fistula clotted!" Your heart rate jumps. This isn't just about restoring blood flow; it's about restoring a patient's lifeline. These access points are meticulously created, often through multiple surgeries, and their failure can mean urgent catheter placement, prolonged hospital stays, and immense stress for the patient. Your role in quickly and effectively "declotting" these lifelines is critical, directly impacting their quality of life and ensuring they can continue their essential dialysis treatments without interruption.

If you remember one thing

Always remember that venous outflow stenosis is almost always the underlying cause of thrombosis, so thoroughly treat it after clearing the clot to prevent immediate re-thrombosis. Early intervention (within 48 hours) is paramount for successful outcomes, so act swiftly.

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