Overview
Definition:
Thrombectomy of arteriovenous (AV) access refers to the surgical or endovascular removal of thrombus (blood clot) that obstructs an AV fistula or graft used for hemodialysis
This procedure aims to restore patency and usability of the access for dialysis, preventing or treating access dysfunction.
Epidemiology:
Thrombosis is a major cause of AV access failure, affecting approximately 15-30% of fistulas and 20-40% of grafts annually
This necessitates re-interventions, including thrombectomy, to maintain dialysis access for end-stage renal disease (ESRD) patients.
Clinical Significance:
Successful thrombectomy is crucial for maintaining adequate blood flow during hemodialysis, ensuring effective waste product removal, and preventing significant morbidity associated with access failure
It prolongs the functional lifespan of the AV access, reducing the need for central venous catheters or repeat access creation, which carry higher complication rates.
Indications
Absolute Indications:
Complete or near-complete occlusion of AV fistula or graft by thrombus, leading to inadequate blood flow for hemodialysis
Documented access thrombosis with inability to perform dialysis through the access.
Relative Indications:
Significant stenosis leading to recurrent thrombosis or poor dialysis flow
Acute distal steal syndrome secondary to thrombosis
Symptomatic swelling or pain related to thrombus.
Contraindications:
Uncorrectable infection of the access or surrounding tissues
Limited life expectancy of the patient
Patient refusal or inability to undergo the procedure
Absence of usable inflow or outflow vessels on imaging.
Diagnostic Approach
History Taking:
Inquire about duration and effectiveness of dialysis treatments
Note any changes in fistula/graft thrill or bruit
Ask about arm swelling, pain, or discoloration
Assess for symptoms of access infection
Review prior access interventions and complications.
Physical Examination:
Palpate for thrill and auscultate for bruit along the AV access
Examine for signs of distal ischemia (coolness, pallor, diminished pulses)
Assess for signs of infection (erythema, warmth, purulence, fever)
Evaluate for arm edema.
Imaging Studies:
Duplex ultrasonography (US) is the primary modality to assess access patency, identify thrombus, and evaluate for stenosis
Angiography (conventional or CT/MR) may be used to delineate the extent of thrombosis and identify underlying stenotic lesions or collateral vessels, guiding surgical or endovascular planning.
Laboratory Tests:
Complete blood count (CBC) to assess for anemia or infection
Coagulation profile (PT/INR, aPTT) to assess bleeding risk
Blood cultures if infection is suspected
Renal function tests (BUN, creatinine) for baseline status.
Management
Preoperative Preparation:
Ensure adequate hydration and optimize renal function
Administer prophylactic antibiotics if indicated, especially for grafts
Review imaging findings to plan the approach
Obtain informed consent
Ensure appropriate vascular access for anesthesia administration.
Surgical Thrombectomy:
Involves surgical exposure of the AV access (fistula or graft)
Arteriotomy is made proximal to the clot
Fogarty catheters or similar devices are used to mechanically extract the thrombus
Careful irrigation and inspection of the lumen are performed
Anastomosis is repaired or graft is reconstructed
Re-establishment of thrill and bruit is assessed.
Endovascular Thrombectomy:
Performed via percutaneous puncture of the access
Catheters are advanced to the thrombosed segment
Various devices like AngioJet, rheolytic thrombectomy devices, or aspiration thrombectomy catheters are used to macerate and remove the clot
Mechanical thrombectomy is often followed by balloon angioplasty to treat underlying stenosis and may require stenting
Thrombolytic therapy (e.g., urokinase, tPA) may be used adjunctively or as a primary treatment for recalcitrant thrombus.
Postoperative Care:
Close monitoring of access patency (thrill, bruit, flow)
Strict fluid balance and vital sign monitoring
Pain management
Wound care and monitoring for signs of infection
Administration of anticoagulation (e.g., heparin or LMWH) and antiplatelet agents (e.g., aspirin) as per protocol
Early resumption of dialysis if feasible.
Complications
Early Complications:
Bleeding at the access site or puncture site
Hematoma formation
Incomplete thrombus removal leading to recurrent thrombosis
Embolization of thrombus fragments to distal circulation
Infection
Allergic reaction to contrast or thrombolytics
Graft or fistula limb damage.
Late Complications:
Restenosis of the access at the treated site or elsewhere
Pseudoaneurysm formation
Graft infection
Venous outflow obstruction
Continued access failure requiring further intervention.
Prevention Strategies:
Regular access surveillance with physical examination and Doppler US to detect early signs of stenosis or thrombosis
Timely angioplasty or surgical revision of stenotic lesions
Strict adherence to sterile technique during access cannulation
Judicious use of anticoagulation/antiplatelet therapy post-intervention.
Prognosis
Factors Affecting Prognosis:
Success of initial thrombectomy
Presence and severity of underlying stenotic lesions
Quality of native veins or graft material
Patient's overall health status and adherence to follow-up
Development of new thrombotic events.
Outcomes:
Successful thrombectomy can restore adequate dialysis flow and prolong access survival
Primary patency rates vary, with endovascular interventions often requiring adjunct angioplasty or stenting
Surgical thrombectomy may offer better initial patency for complex clot burdens but can have higher morbidity
Graft survival is generally lower than fistula survival.
Follow Up:
Regular clinical and US surveillance of the access is essential
Monitoring for thrill, bruit, and signs of stenosis or thrombosis
Patients should be educated on self-monitoring and reporting any changes
Follow-up frequency is typically determined by the patient's risk factors and previous access history.
Key Points
Exam Focus:
Understand the indications for thrombectomy (failure to dialyze)
Differentiate between surgical and endovascular approaches
Recall common thrombectomy devices (Fogarty catheter, AngioJet)
Recognize the role of angioplasty and stenting in endovascular thrombectomy
Be aware of anticoagulation/antiplatelet strategies post-procedure.
Clinical Pearls:
Always assess the thrill and bruit pre- and post-thrombectomy
If performing endovascular thrombectomy, ensure a thorough assessment for underlying stenosis, as isolated thrombus is rare
Consider thrombolysis for diffuse, non-occlusive thrombus or as an adjunct to mechanical methods
Remember that thrombectomy alone does not address the underlying cause of thrombosis (usually stenosis).
Common Mistakes:
Performing thrombectomy without adequately addressing underlying stenosis, leading to rapid re-thrombosis
Incomplete clot removal
Aggressive manipulation causing damage to the access vein or graft
Failure to provide adequate postoperative anticoagulation
Misinterpreting imaging findings leading to inappropriate intervention.