Outcomes of Arteriovenous Fistula (AVF) procedure after the Fistula First Initiative
Benefits of the AVF procedure for hemodialysis
Vascular access dysfunction is a major contributor to the hospitalization of hemodialysis patients and their overall morbidity and mortality.
The Fistula First Initiative emphasized the primacy of AVF as the desired vascular access for patients maintained on chronic hemodialysis. AVFs, in general, exhibit greater functional longevity, are less prone to infections, and are associated with decreased mortality and lower costs.
Potential problems resulting from AVFs
The outcomes for this appropriately preferred access are undoubtedly poor. Up to 50% of AVFs are never usable for hemodialysis, and of the AVFs that do function, 25% will fail after two years; outcomes for other accesses are also poor with low patency rates.
The consequences of AVF failure are substantial and far-ranging. For example, such failure not only denies patients a functional access but also reduces the number of sites where subsequent accesses may be placed.
AVF procedure study – design, participants, measurements, and definitions
A retrospective cohort study of AVFs placed in 293 patients from 2006 through 2008 was conducted at Mayo Clinic. Suitability for hemodialysis required AVF usage with two needles and maintenance of blood flow > 300 ml/min for at least eight hemodialysis sessions over one month. Primary failure was defined as the permanent failure of the AVF before hemodialysis suitability. This definition includes inadequate maturation, thrombosis, failure of first and subsequent cannulations, and other complications leading to non-functional AVFs. Secondary failure was permanent failure after the AVF met dialysis suitability criteria with subsequent abandonment.
Results are shown in the following figures: Figure 1 (top) – all AVF outcomes at the end of follow-up and Figure 2 (bottom) – AVF outcomes at the end of follow-up for patients who required hemodialysis at some time and did not die or who did not receive a transplant before AVF use.
Moreover, 82 complications resulting from the creation of AVFs occurred in 21.2% of patients. Complications included bleeding, infection, steal syndrome aneurysm, thrombosis, seroma, subclavian stenosis, and nerve injury. The AVF failure rate at our clinic is consistent with previous studies.
Predictors for AVF patency
The study found differences in predictors of patency. We found that there are several factors, such as BMI, arterial diameter etc., associated with primary and secondary AVF patency. The major predictor of primary and secondary patency was artery size, and indeed, with a 1-mm increase in arterial diameter, the risk of AVF abandonment decreased by 30%. We did not observe a predictive effect of age, gender, vascular disease, BMI, catheter use, or time on hemodialysis.
This effect of artery size may reflect four factors. First, blood flow is proportional to the fourth power of the arterial radius, and thus small increments in size may substantially increase flow. Second, larger arteries may exhibit a greater vasorelaxant response, thereby accommodating greater blood flow during AVF maturation. Third, AVF thrombosis may be less likely with larger arteries, and, interestingly, we found a possible relationship between secondary AVF patency and thromboembolic disease. Fourth, creating AVFs with larger arteries may be a less challenging procedure.
What should be considered for future AVF procedures?
While the fundamental premise of Fistula First is indisputable, issues such as the complications incurred, the procedures needed, the price paid, and the overall adverse effect on quality of life should be considered as we endeavor to maximize the number of patients with functional AVFs.
VasQ – a practical solution to improve patency rates of AV fistulas
Our product 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.