Success of AV Fistulas for Dialysis Varies Widely Between Countries

Pam Harrison

October 08, 2020

The successful creation and use of arteriovenous fistulas (AVFs) for vascular access for dialysis patients varies considerably between countries, despite national guidelines that uniformly recommend AVFs as the access of first choice.

"Optimizing vascular access (VA) use is crucial for long-term hemodialysis patient care," say the lead author of this international comparison of fistula patency and use, Ronald Pisoni, PhD, Arbor Research Collaborative for Health, Ann Arbor, Michigan, and colleagues.

"[G]reater primary and cumulative AVF patency was seen for HD [hemodialysis] patients in Japan than in EUR/ANZ [Europe, Australia, New Zealand] and the US.... These international comparisons may provide important guidance for US clinicians seeking to achieve vascular access success comparable to Europe and Japan," they note in their article, published in the American Journal of Kidney Diseases.

AVFs are not suitable for all patients, they note, so "these findings highlight the importance of selecting the best access type for each patient and developing effective clinical pathways for when AVFs fail to mature successfully."

In addition, failure of new AVFs is associated with long-term use of catheters and substantially higher mortality risk, they found.

Vascular Access in Dialysis: "A Patient's Lifeline"

Vascular access plays such a central role in hemodialysis therapy that it is often referred to as "a patient's lifeline," the researchers explain.

The aim of their observational analysis― the international Dialysis Outcomes and Practice Patterns Study (DOPPS) study ― was to compare among countries the rate of native AVF patency and time to becoming catheter free for patients with kidney disease who receive hemodialysis.

They reviewed data on AVFs newly created from 2009 to 2015. The results are based on a total of 2191 newly created AVFs in 2040 patients within 466 facilities in the United States, Japan, and Europe/Australia/New Zealand. European countries included Belgium, France, Germany, Italy, Spain, Sweden, and the United Kingdom.

Outcomes included primary/cumulative AVF patency (from creation), primary/cumulative functional patency (from first use), catheter-dependence duration, and mortality.

Japan was found to have superior primary and cumulative patencies, owing to a higher rate of successful AVF use. Cumulative functional patency was similar across regions.

Primary AVF patency for patients was 1.4-fold to 1.5-fold greater at 1 year in Japan (72%) than in Europe/Australia/New Zealand (51%); at 2 years, the rate was 60% in Japan and 40% in Europe/Australia/New Zealand (data were unavailable for US patients).

This appears to be largely accounted for by greater successful maturation of newly created AVFs in Japan (92%) than in Europe/Australia/New Zealand (70%) and the United States (63%) and "is consistent with prior work," say the researchers.

Cumulative functional patency was similar across all three international regions, with 88% of successfully used AVFs remaining patent at 1 year in each region.

Central Venous Catheter Use Varies Too

A central venous catheter (CVC) was used at the time of AVF creation for 75%, 69%, and 8% of AVFs in the United States, Europe/Australia/New Zealand, and Japan, respectively.

In Japan, 80% of these patients were CVC-free within approximately 15 days, whereas it took months for patients in Europe/Australia/New Zealand and the United States to become catheter-free after AVF creation, Pisoni noted in an interview with Medscape Medical News.

Catheter dependence following AVF creation was much longer in Europe/Australia/New Zealand and the United States, with nearly 70% of patients remaining catheter dependent 8 months post AVF creation when AVFs were not successfully used.

Not using the newly created AVF access within 6 months of its being created was associated with a 53% higher mortality rate over the next 6 months compared to cases in which the AVF was successfully used, the authors note.

Pisoni acknowledged that they could not explain why the newly created AVFs were not used in the United States or why mortality rates were so high among those for whom AVF use had proven futile.

Are the Differences Due to Speed of Dialysis or Where AVF Is Created?

Differences in techniques between countries might explain the better results for AVF patency rates and use seen in Japan, where dialysis sessions are conducted more slowly than elsewhere.

The typical blood flow rate used during a dialysis session is around 200 mL/min in Japan. In other countries, it is between 300 and 400 mL/min, and in the United States, it is between 400 to 500 mL/min. An AVF created in the United States may prove to be inadequate when required to deliver 400 to 500 mL/min of blood flow, whereas in Japan, it would be more than adequate, Pisoni suggested.

There is also a large between-country difference in where in the arm the AVFs are created.

The current analysis covers the period from 2009 to 2015. During that time, only about one third (32%) of AVFs in the United States were created in the forearm.

By contrast, during this period, about half (54%) of the AVFs in Europe/Australia/New Zealand and 84% of those in Japan were placed in the forearm.

Only in the United States did forearm AVFs display poorer cumulative AVF patency than newly created arm AVFs.

"This is seen despite the US appearing to be much more selective regarding which patients receive a forearm AVF," say Pisoni and colleagues.

This raises important questions regarding the underlying reasons ― whether surgical or otherwise ― for the low use of forearm AVFs in the United States and why cumulative AVF patency is poorer in the United States despite the much lower use of forearm AVFs.

"Typically, the vessels in the upper arm are going to be much larger than they are in the forearm, so it's easier to create an access in the upper arm," Pisoni explained.

The shift to creating an AVF in the upper arm in the United States may reflect the fact that larger vessels can accommodate the more intense blood flow rate used in dialysis in the United States compared to that used in Japan, he suggested.

Regardless of the factors that contribute to the higher failure rates in forearm fistulas among US patients, "guidelines suggest that when creating a fistula for dialysis patients, you should always try to start in the forearm, because if that first one fails, there are more sites...that you can move up to," Pisoni explained.

By initially creating a fistula in the upper arm, "you have foregone all those other sites you might have used in the forearm more distally, and this limits the number of sites you can use if the upper arm fistula fails," Pisoni cautioned.

Differences Ultimately Down to Surgeon's Experience, It Seems

Ultimately, however, the greater success achieved with AVF maturation and use in Japan compared to elsewhere may simply come down to professional experience.

"Fistula use is much higher in Japan than it is in many other countries," Pisoni pointed out.

The more fistulae created by a surgeon, the greater the success, so surgical experience at least in part explains why maturation rates of AVFs created in the United States are lower than they are in Japan.

"Time and time again, you can see by changing to a different surgeon in a different facility that fistula use can really increase," Pisoni noted.

"So it may come down to a surgeon's perspective on things and their expertise, and there is just a lot of variation in practice in this regard," he concluded.

The study was supported by funding from Proteon Therapeutics. Pisoni has disclosed no relevant financial relationships..

American Journal of Kidney Diseases. Published online September 21, 2020. Full text

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