November 29, 2000 In every new dialysis patient, a permanent access route into the venous system must be created, usually in an arm. Now researchers at the Johns Hopkins School of Public Health have compared the risks associated with the two most common venous grafts--the arteriovenous (AV) fistula (in which an artery and a vein are surgically joined under the skin so the patient's arterial blood can be diverted back to the venous circulation) and the synthetic polytetrafluoroethylene (PTFE) graft. The scientists have found that men age 72 and younger who must undergo chronic dialysis have significantly fewer complications with the AV fistula than with the synthetic graft. No such benefit was observed in women or in men 73 and older. The study appeared in the December 2000 issue of the American Journal of Kidney Diseases. Although previous studies had shown that AV fistula grafts yield superior outcomes for dialysis patients when compared to the synthetic graft, this study is the first to report the AV fistula's gender-specific benefit over PTFE grafts. First author Brad C. Astor, PhD, MPH, post-doctoral fellow, Epidemiology, Johns Hopkins School of Public Health, said, "Compared to men with an AV fistula, women with an AV fistula experienced significantly more complications with this venous access route during the first three months of dialysis, a result that suggests women may require more frequent screening for early AV-fistula dysfunction, and that this screening should continue for at least three months after initiation of dialysis." The researchers analyzed national data concerning complications arising in the venous access grafts of 833 patients, 621 with a PTFE graft and 212 with an AV fistula. The outcome measure used in the study was the time between a graft's initial placement and when that graft developed a complication warranting a procedure. For the analyses, the researchers divided the subjects into various subgroups, including venous-access type, gender, age, demographics, smoking history, and health conditions such as diabetes and heart disease. Follow-up through 1996 revealed that women with an AV fistula were over one-and-a-half times more likely than men with an AV fistula to need a subsequent access-related procedure, while women with PTFE grafts were less likely than men with PTFE grafts to have a future complication during the follow-up period. Among men, the median time before an AV fistula needed repair was 929 days, compared to 329 days for women with an AV fistula. This gender difference was apparent by 30 days into the follow-up period: One month into the study, 14 percent of women with an AV fistula had undergone procedures to fix their grafts, compared to just 5 percent of men with an AV fistula. As compared to the AV fistula, PTFE grafts were associated with a more than twofold increase in the risk of complications in men but not in women, after adjustment for age, race, presence of diabetes, and smoking history. The benefit of AV fistulae was limited to men age 72 and younger. The authors speculate that women may require a longer time for an AV fistula to mature before it can function properly as an access route to the venous system. If this hypothesis were to prove true, the AV fistula's first use, the researchers say, may need to be delayed in women. The authors said future prospective studies are needed to determine whether the AV fistula confers any long-term benefits on women and older men. Support for this study was provided by the National Heart, Lung, and Blood Institute; the National Institute of Diabetes and Digestive and Kidney Diseases; and the Agency for Health Care Research and Quality. Public Affairs Media Contacts for the Johns Hopkins Bloomberg School of Public Health: Tim Parsons or Kenna Brigham @ 410-955-6878 or paffairs@jhsph.edu. | 
