Overview
Definition:
Arteriovenous (AV) fistula maturation failure refers to the inability of a surgically created AV fistula to develop adequate flow, volume, and depth for successful hemodialysis within the expected timeframe
This can be due to various intrinsic or extrinsic factors affecting the fistula's vascular elements or surrounding tissues.
Epidemiology:
Maturation failure rates vary significantly depending on fistula type (radiocephalic vs
brachiocephalic), surgeon experience, and patient factors, but can range from 10-30% for initial maturation
Early failure is more common than late failure
Patients with diabetes, peripheral vascular disease, and previous interventions are at higher risk.
Clinical Significance:
Successful AV fistula maturation is paramount for chronic hemodialysis, offering superior long-term outcomes compared to other vascular access modalities
Maturation failure necessitates timely intervention to avoid prolonged reliance on central venous catheters, which carry higher morbidity and mortality
Understanding revision strategies is vital for vascular and general surgeons managing these patients.
Indications For Revision
Inadequate Flow:
Failure to achieve a minimum arterialized venous flow of 500-600 mL/min
Failure to achieve adequate arterial inflow for dialysis.
Insufficient Depth:
Vein too superficial or too deep for reliable cannulation (typically requiring a depth of 0.5-1.0 cm).
Aneurysmal Dilatation:
Excessive or symptomatic dilatation with risk of rupture or difficult cannulation.
Stenotic Lesions:
Development of stenoses within the fistula or draining vein, identified by ultrasound or during cannulation attempts, leading to recirculation or inadequate flow.
Thrombosis:
Acute or subacute thrombosis of the fistula or outflow vein.
Steal Syndrome:
Distal ischemia or symptoms of vascular steal affecting the ipsilateral limb, despite adequate fistula flow.
Diagnostic Approach
History Taking:
Detailed history of prior vascular access
Dialysis adequacy reports
Symptoms of steal syndrome (pain, paresthesia, coolness of hand)
Previous interventions or complications.
Physical Examination:
Palpation for thrill (absent or diminished in failure)
Auscultation for bruit (continuous, low-pitched in successful fistulas
may be absent or high-pitched in failure)
Examination of distal pulses and perfusion
Assessment of fistula site for signs of infection or aneurysm.
Investigations:
Duplex ultrasonography is the primary modality for assessing fistula anatomy, flow dynamics, and identifying stenotic lesions or thrombosis
Arteriography or venography may be performed if ultrasound is inconclusive or before surgical planning
Blood pressure and dialysis adequacy monitoring are crucial.
Differential Diagnosis:
Inadequate dialysis can also be due to central venous stenosis (if a catheter was used), inadequate dialyzer performance, or patient non-compliance
Other causes of limb ischemia should be considered if steal syndrome is suspected.
Surgical Revision Strategies
Primary Revision Techniques:
Direct angioplasty or stenting of stenotic lesions identified on imaging
Ligation of accessory veins contributing to inadequate flow or steal
Transposition of superficial veins to facilitate maturation.
Redo Fistula Creation:
For complete failure or absence of viable outflow vein, creation of a new fistula at a different site, often using more proximal vessels (e.g., brachial artery to basilic vein transposition or prosthetic graft).
Aneurysm Repair:
Surgical excision and reconstruction, or patch angioplasty for aneurysmal segments
In some cases, exclusion or banding may be considered.
Thrombectomy And Revision:
Surgical or pharmacomechanical thrombectomy followed by angioplasty or revision of contributing lesions
Placement of an interposition graft may be necessary if native vein is compromised.
Preoperative Planning And Patient Selection
Preoperative Assessment:
Comprehensive vascular mapping with duplex ultrasound to identify suitable inflow and outflow vessels
Assessment of comorbidities
Review of prior access history and interventions.
Patient Counseling:
Informed consent regarding the risks, benefits, and alternatives to revision surgery
Discussion of expected outcomes and potential for future failures.
Anesthesia Considerations:
Local anesthesia is often preferred for simple revisions, while general anesthesia may be required for more complex procedures or redo fistulas.
Postoperative Care And Follow-up
Immediate Postoperative Care:
Monitoring of fistula thrill and bruit
Close observation for bleeding or hematoma formation
Pain management and anticoagulation if indicated.
Long Term Monitoring:
Regular duplex ultrasound surveillance to assess flow, detect early signs of stenosis or thrombosis
Patient education on self-monitoring of thrill and bruit
Prompt reporting of any concerning symptoms.
Complication Management:
Early recognition and management of post-operative bleeding, infection, venous hypertension, or steal syndrome
Prompt referral for further intervention if issues arise.
Key Points
Exam Focus:
Understanding the flow rates (minimum 500-600 mL/min) and depth requirements for AV fistula maturation
Differentiating between stenosis, thrombosis, and steal syndrome
Knowing the common revision techniques like angioplasty, stenting, and transposition.
Clinical Pearls:
Always perform a thorough physical exam of the fistula site, listening for the characteristic bruit and feeling for the thrill
Duplex ultrasound is your best friend for diagnosis
Consider patient comorbidities and prior interventions when planning revision.
Common Mistakes:
Attributing all AV fistula failures solely to outflow stenosis without considering inflow issues or central venous pathology
Delaying revision for inadequate maturation, leading to prolonged catheter use
Inadequate preoperative vascular mapping.