How to manage high Arteriovenous Fistula (AVF) flow?

Management of High Arteriovenous Fistula (AVF) Flow

Close monitoring with measurement of access flow (Qa) and cardiac output ratio (Qa/CO) every 6-12 months is essential, with prophylactic intervention indicated when Qa exceeds 1-1.5 L/min or Qa/CO exceeds 20%, particularly in patients with cardiac dysfunction or ejection fraction <15%. 1

Definition and Thresholds

High-flow AVF lacks universal consensus on exact thresholds, but the following parameters warrant intervention:

• Access flow (Qa) of 1-1.5 L/min or greater 2, 3
• Qa/CO ratio >20% (cardiopulmonary recirculation) 3
• Development of any signs of cardiac failure, regardless of absolute flow values 2
• Lower flow values may be excessive in elderly patients or those with pre-existing cardiac disease 2

The 2019 KDOQI guidelines emphasize that high-flow AVF should be managed prophylactically to avoid serious or irreversible complications, particularly high-output cardiac failure. 1

Clinical Monitoring Strategy

Physical Examination at Each Dialysis Session

Monitor for the following high-risk indicators:

• Signs of high-output cardiac failure: dyspnea, peripheral edema, elevated jugular venous pressure 1, 2
• Ipsilateral extremity edema persisting beyond 2 weeks 1
• Changes in thrill character or bruit 4
• Pulmonary hypertension symptoms 2, 3
• Massively dilated fistula 2

Surveillance Testing

• Qa measurement every 6-12 months, or more frequently if clinical concerns arise 1
• Cardiac output assessment to calculate Qa/CO ratio 3
• Echocardiography in patients with cardiac symptoms or ejection fraction concerns 1

Risk Stratification

Brachiocephalic AVFs carry 12-fold higher risk of complications compared to radiocephalic AVFs, with 61% developing cephalic arch stenosis versus 6% in radiocephalic fistulas. 5 Each 1 mL/min increase in flow correlates with 0.07% increased probability of cephalic arch stenosis development. 5

High-risk patients requiring closer monitoring include:

• Patients with ejection fraction <15% 1
• Elderly patients with pre-existing cardiac disease 2
• Upper arm (brachiocephalic) AVF locations 5
• Patients with central venous stenosis 2

Intervention Strategies

Indications for Flow Reduction

Immediate intervention is required when:

• High-output cardiac failure develops 1, 2
• Qa exceeds 1.5 L/min with cardiac symptoms 3
• Qa/CO ratio >20% 3
• Progressive cardiac decompensation despite medical management 2

Surgical Flow Reduction Techniques

Multiple surgical options exist, chosen based on operator experience and anatomic considerations:

• DRIL (Distal Revascularization-Interval Ligation) with prosthetic patch interposition 3
• RUDI (Revision Using Distal Inflow) procedures 3
• "Trench snout" technique: removal of previous anastomosis with radial artery reconstruction and interposition of 5mm diameter PTFE segment to reduce anastomotic diameter to approximately 4mm 3
• Banding procedures (though traditional techniques have shown limited success) 1

Target post-intervention flow should be approximately 1500 mL/min or less, adequate for dialysis while preventing cardiac complications. 3

Endovascular Options

• Percutaneous transluminal angioplasty (PTA) for associated stenoses that may be contributing to flow dynamics 1
• Treatment of central venous stenosis if present, as this can exacerbate high-flow complications 1, 5

Absolute Contraindications to Continued High-Flow AVF

Immediate AVF ligation is mandatory when:

• Ejection fraction <15% with high-flow access 1
• Refractory high-output cardiac failure 1, 2
• Monomelic ischemic neuropathy develops (acute neuropathy with global muscle pain, weakness, warm hand with palpable pulses within first hour post-creation) 6
• Progressive cardiac decompensation despite flow reduction attempts 2

Common Pitfalls

• Delaying intervention until cardiac failure is advanced: Early prophylactic management prevents irreversible cardiac damage 1
• Focusing solely on absolute Qa values without considering patient-specific factors: A flow of 1 L/min may be excessive in an elderly patient with cardiac disease 2
• Failing to calculate Qa/CO ratio: This provides more accurate assessment of hemodynamic impact than Qa alone 3
• Underestimating the significance of brachiocephalic AVF location: These require more aggressive surveillance given 12-fold higher complication risk 5
• Attempting medical management alone in symptomatic high-flow states: Surgical flow reduction is definitive treatment 3

Alternative Access Planning

When flow reduction fails or is contraindicated, alternative dialysis access must be established, typically requiring temporary catheter placement while planning for alternative permanent access in a different location or contralateral limb. 6 Consider catheter-based dialysis as definitive access in patients with ejection fraction <15% and limited life expectancy <6-12 months. 1