Arteriovenous Grafts: Much Maligned But in Need of Reconsideration?

Abstract

There are substantial variations in arteriovenous fistula (AVF) use among hemodialysis patients in different countries, in different regions of the U.S., and even in different hemodialysis units within a single metropolitan area. These variations persist after adjustment for patient demographics and comorbidities, suggesting that practice patterns play a major role in determining the frequency of AVF use. These observations led to vascular access guidelines urging nephrologists and surgeons to increase AVF creation in patients with chronic kidney disease. Over the past 20 years, as clinicians have adopted these guidelines, the prevalence of AVF use in hemodialysis patients has increased substantially. At the same time, clinicians have recognized important limitations of an unwavering "Fistula First" approach. First, a substantial proportion of AVFs fail to mature even when routine preoperative vascular mapping is used, leading to prolonged catheter dependence. Second, certain patient subgroups are at high risk for AVF nonmaturation. Third, nonmaturing AVFs frequently require interventions to promote their maturation. Fourth, AVFs that require such interventions have shortened cumulative patency. Fifth, arteriovenous grafts (AVG) have several advantages over AVFs, including lower primary failure rates, fewer interventions prior to successful cannulation, and shorter duration of catheter dependence with its associated risk of bacteremia. All these observations have led nephrologists to propose an individualized approach to vascular access, with AVG being preferred in patients who initiate hemodialysis with a catheter, particularly if they are at high risk for AVF nonmaturation and have a relatively short life expectancy.

Figure 1. Cumulative access patency of AVFs that matured with or without prior interventions and AVGs that did or did not require intervention prior to successful cannulation

Access patency was shorter for AVF with prior intervention than AVF without interventions (P < 0.0001). Access patency was shorter for AVG with prior interventions than AVG without intervention (P < 0.0001). Access patency was similar for AVF and AVG without prior interventions (P =0.16). Cumulative access patency was worse for AVF with prior interventions than for AVG without prior interventions (P = 0.01). Reproduced with permission from.

Fig 2. An algorithmic guide to choosing an appropriate hemodialysis vascular access for patients

This protocol requires the nephrologist and access surgeon to consider three important clinical factors: timing of access surgery relative to initiation of hemodialysis, life-expectancy of the patient, and prior failed vascular access. This information, along with the likelihood of AVF non-maturation, is used to determine the most appropriate vascular access for that patient: fistula (F) or graft (G). Reproduced with permission from.

Figure 3

The likelihood of catheter dependence at initiation of hemodialysis in elderly patients undergoing pre-dialysis AVF or AVG surgery, sorted by duration of pre-dialysis nephrology follow-up. Adapted from.