# 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.

![Clinical assessment of thrombosed dialysis access](images/thrombosed-access-assessment.png)

## 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

| Device | Mechanism | Best For | Key Feature |
|--------|-----------|----------|-------------|
| Arrow-Trerotola PTD | Rotating basket fragmentation | AVG, soft thrombus | Rapid mechanical disruption |
| AngioJet | Rheolytic (Bernoulli effect) | AVG/AVF | Simultaneous aspiration |
| Balloon sweep | Balloon inflation + sweep | Residual thrombus | Simple, widely available |
| Aspiration catheter | Manual suction | Arterial plug | Direct clot removal |

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.

![Step-by-step percutaneous declot procedure overview](images/declot-procedure-steps.png)

## 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.

![Declot outcomes and surveillance schedule](images/declot-outcomes-surveillance.png)

## 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.