SAN FRANCISCO – Outcomes of forearm and upper arm hemodialysis arteriovenous grafts are similar despite the fact that large caliber outflow veins are often encountered in the upper arm, results from a large trial showed.
"To preserve a maximal number of access sites, forearm location should always be considered before resorting to an upper arm graft," Dr. Alik Farber said at the Society for Vascular Surgery Annual Meeting.
The incidence and prevalence of end-stage renal disease in the United States has grown exponentially in the past 25 years, said Dr. Farber, chief of vascular and endovascular surgery at Boston University Medical Center. "In fact, in 2010 almost 400,000 patients were undergoing hemodialysis," he said. "At the same time, there has been a steady increase in the percent of AV fistulas placed and an associated decline in the percent of AV grafts placed in the United States. In 2010, 20% of patients were undergoing hemodialysis through AV grafts."
Dr. Alik Farber
Most grafts in the upper extremity are based on the brachial artery. Some are in the forearm while others are in the upper arm. "In the forearm most grafts are looped," Dr. Farber said. "In the upper arm some are looped and some are straight. As it turns out, the optimal graft configuration is unknown. The optimal venous outflow in the upper extremity is unknown. And the optimal location of the first-time AV graft is controversial."
He went on to note that the forearm AV graft "saves the upper arm for a future graft site and has a potential advantage of increasing the suitability of upper arm veins for future native fistula. On the other hand, there is some evidence in the literature that forearm grafts have lower patency rates. The upper arm graft may have higher patency rates because they are ‘sawn into’ large caliber veins. However, surgeons who preferentially place upper arm grafts tend to skip potential distal access sites."
Given the dearth of information on this topic, Dr. Farber and his associates set out to compare outcomes of forearm and upper arm grafts and to evaluate the association between upper extremity AV graft configuration, location, venous outflow, and patency in 649 patients from a multicenter trial conducted by the Dialysis Access Consortium (DAC). This was a randomized, controlled trial of dipyridamole versus placebo in patients with new AV grafts. It found that dipyridamole increased primary unassisted graft patency (N. Engl. J. Med. 2009;360:2191-201). "The important thing for us was that this is the largest randomized, controlled trial of AV grafts conducted to date," Dr. Farber said.
He presented results from 522 patients with AV grafts that were based on the brachial artery. Of the 522 patients, 269 had a forearm graft (fAVG) and 253 had an upper arm graft (uAVG). The primary outcome was loss of primary unassisted patency. "This was defined as a first occurrence of graft thrombosis, an access procedure to correct a greater than 50% stenosis, or other surgical graft modification," Dr. Farber explained. The secondary outcome was cumulative graft failure, "which was defined as the time from randomization to complete loss of access site for dialysis." Kaplan-Meier curves and Cox models were used to examine the effects of access location and configuration on study outcomes.
Compared with patients in the fAVG group, those in the uAVG group were more likely to be male (43% vs. 34%), to be African-American (78% vs. 62%), to have a lower body mass index (mean of 29 kg/m2 vs. a mean of 32 kg/m2), to have a lower baseline systolic blood pressure (139 mm Hg vs. 146 mm Hg), to have hemodialysis initiated before graft placement (80% vs. 64%), and to be on dialysis for a longer period of time (a mean of 2.59 years vs. a mean of 2.51 years).
Unadjusted analyses showed that there was no significant difference in the loss of primary unassisted graft patency or cumulative graft failure between the fAVG and uAVG groups.
Multivariate analyses of outcomes controlled for covariates revealed that the risk of loss of primary unassisted graft patency was not significantly higher in the uAVG group, compared with the fAVG group (hazard ratio of 1.24; P = .15). However, there was a suggestion of an association of increased risk of cumulative graft failure among upper arm grafts (HR 1.37; P = .09).
In a comparison of straight vs. looped grafts, straight configuration grafts "appeared to have a lower risk of primary and secondary failure, compared with looped figuration grafts, [but] this difference was not statistically significant," he said.