From the Guidelines
Arteriovenous fistulas (AVFs) steal blood flow from distal tissues due to the creation of a low-resistance pathway that diverts blood away from normal circulation, leading to compromised perfusion and ischemia, as described in the 2020 update of the KDOQI clinical practice guideline for vascular access 1. This pathological shunting occurs because the fistula allows blood to bypass the high-resistance capillary networks that normally supply distal tissues. As blood follows the path of least resistance, a significant portion flows directly from the artery into the vein through the fistula rather than continuing downstream to perfuse the hand or foot.
- The blood steal phenomenon reduces perfusion pressure in arteries distal to the fistula, potentially causing ischemia in the affected extremity, with signs and symptoms ranging from mild numbness to severe motor impairment or skin ulceration to gangrene necessitating major amputation, as outlined in the KDOQI guideline 1.
- The altered hemodynamics trigger inflammatory responses in the underperfused tissues, with the release of inflammatory mediators increasing vascular permeability.
- This permeability change, combined with the venous hypertension that develops from increased venous return through the fistula, leads to fluid extravasation into surrounding tissues, manifesting as edema. The combination of reduced arterial inflow and compromised venous outflow creates a perfect storm for tissue damage, particularly in patients with pre-existing vascular disease, highlighting the importance of careful consideration and monitoring of patients with AVFs to prevent these complications.
From the Research
Arteriovenous Fistulas and Blood Flow
- Arteriovenous fistulas (AVFs) can steal blood flow from distal tissues, leading to ischemia and potentially contributing to edema through inflammatory responses 2, 3, 4.
- The creation of AVFs can lead to Hemodialysis Access-Induced Distal Ischemia (HAIDI), characterized by ischemia in extremities due to reduced capillary perfusion 2.
- High-flow AVFs can disrupt overall circulatory dynamics, posing a significant challenge, particularly in patients with cardiovascular compromise 2.
Mechanisms of Blood Flow Theft
- Blood shunting through the AVF may cause stealing of blood and hypoperfusion in distal tissues, leading to pain, discoloration, and ulcers 4.
- High-flow AVFs have a greater risk of ischemia than normal flow AVFs, especially when combined with peripheral arteriosclerotic disease 4.
- Undetected collateral flow or side branches from target vessels can receive increased blood volume after fistula creation, expanding and stealing blood flow from the hand 3.
Treatment Options
- Techniques to reduce AVF flow and improve distal perfusion include vein approach (ligation, plication, banding, prosthetic graft interposition) and arterial interventions (distal radial artery ligation and embolization) 2.
- Anastomosis remodeling and bypassing the arteriovenous anastomotic site can also eliminate pain and heal ulcers 4, 5.
- Remote distal arteriovenous fistula creation can augment native arterial blood flow and improve distal limb perfusion 6.