AV fistulas often fail to mature
Studies over several decades have consistently demonstrated that native mature fistulas have superior longevity, spanning 4 to 5 years, and require minimal secondary interventions compared with other access types. However, despite the clear benefits of mature fistulas, early failure occurs in over 40% of fistulas. Failure is often due to clotting and thrombosis of the fistula which is caused by turbulent flow patterns around the anastomosis region. Later failures are associated with exposure of the vein to high pressure and wall tension. These arterial pressures cause a thickening of the intimal layer, called intimal hyperplasia, subsequently leading to a narrowing (stenosis) of the vessel lumen. Dember et al, 2008 report a failure rate of 53.4% at 120-150 days after fistula placement.
Turbulent Flow Patterns
A revolution in AV fistula care
VasQ™ was designed to improve maturation and patency rates of AV fistulas. It provides external support thereby addressing the root causes of fistula failure:
- Regulates flow by constraining and shaping optimal geometrical parameters of the fistula.
- Reinforces and shields the vulnerable perianastomotic vein against high pressure, wall tension, and flow levels.
VasQ™ has been shown to be safe and effective. It enhances maturation and improves patency.
A prospective single center study to evaluate the safety and efficacy of VasQ in AV fistula
St George’s Hospital,
Dr. Eric Chemla
- 20 patients received VasQ™ implant for their end-to-side Brachiocephalic fistulas
- Patients were followed for 6 months
- Study end-points included:
- Fistula maturation – Blood flow rate and vein diameter as assessed by Doppler Ultrasound examination
- Fistula patency – Assessed by Doppler Ultrasound examination
- Low complications rate
- No device-related serious adverse events
- Minimal access-related complications
- No interference with the dialysis needle, as the VasQ™ is placed distal to the needle
- No contact with blood, as the device is placed externally
- 93% of patients who had active dialysis at 6 months received dialysis through the study fistula
- 79% of study fistulas have matured after 8 weeks
- Increased success rate of the AV fistulas
- Improved fistula patency rates over the standard of care
- Superior fistula flow rate and vein diameter at 1, 3 and 6 months
Computational fluid dynamics
An analytical model was designed, simulating an AV fistula in anatomical and physiological attributes. The model defines geometrical parameters of optimal flow patterns in the anastomotic area. VasQ was designed to regulate anastomosis geometry and resulting flow patterns, as simulated in the model. The device configuration was clinically verified to obtain the desired outcome.
Below are computational fluid representations of angiography images showing the preferable flow rate profile and increased shear stress in the vein achieved when implanting VasQ™.
- Drop in arterial velocity distal to the anastomosis
- Increased velocity at the junction area between the vein and the artery
- Extended tail of increased velocity at proximal venous region
- Increased velocity along the artery
- Wider area of reduced WSS at the region of the arterial anastomosis
- Increased WSS at the proximal venous region
- Increased WSS along the artery
- Elongated area of increased WSS at the venous opening