At the most recent American Society of Diagnostic and Interventional Nephrology (ASDIN) annual scientific meeting (23–25 February 2024, New Orleans, USA), Victoria Teodorescu (Emory School of Medicine, Atlanta, USA) gave a presentation as part of the Cut, Suture, and Action in ASDINville session, in which she explored the various options for materials used in arteriovenous grafts (AVGs) and the comparative outcomes of each of these options.
Beginning her presentation, she outlined the main features of polytetrafluoroethylene (PTFE) grafts, stating that PTFE is a “ubiquitous material” used for dialysis access grafts, and that there have been some variations developed, with “one of the first [variations] being tapered, where the graft goes from four to seven millimetres [with the] smaller end at the artery”. The aim of this, she avers, is to reduce the incidence of steal. However, citing a meta-analysis of five studies, she stated that over 4,000 patients actually showed “no difference in steal, no difference in either primary or secondary patency, or in the infection rate.” Despite this, the authors did send a “word of caution”, stating that this was a relatively small number of studies, despite the large number of patients, and that “there was limited stratification of outcomes”. Symptomatic steal, Teodorescu stated, occurs in a “very, very small number” of patients and this may explain the authors’ caution.
Continuing, Teodorescu moved on to examining Herapin-bonded grafts. “[Herapin-bonded grafts] sound enticing [as an option to] reduce the episodes of thrombosis,” she postulates, but states that, despite appearances, in a prospective randomised trial of 160 grafts, whilst there was a small amount of improved patency early on in the heparin-bonded grafts compared to standard grafts, in the later period of time, there was no difference between the two.
One option that Teodorescu appeared to be in favour of was “quick-stick” grafts. Citing examples, such as the Acuseal (Gore Medical) or Flixene (Getinge) grafts, she states that she feels that these grafts could be “an advantage”. The presenter states that the Gore Acuseal features several layers of graft that enable early cannulation and “when comparison study of the immediate stick grafts are compared to standard, […] interestingly, the quick stick grafts required fewer procedures to maintain patency; 0.6 procedures”. On average, Teodorescu stated “for the quick-stick graft compared to almost 1.0 procedure for the standard graft over the same period of time. There was, as expected, no difference in steal,” but that the big advantage to these grafts is a shorter time to cannulation. Quick-stick grafts, on average, took six days to cannulate, whereas the standard graft took almost a month. Of course, what goes along with this, she adds, is “less catheter related complications”.
However, she added that there are recently published case reports that show that these grafts can de-laminate, especially Acuseal grafts. “This is visible by ultrasound, both on B mode and Doppler evaluation”. Showing an example, she stated that “if you choose to excise the graft and put in an interposition, you can actually see this is more like a dissection than anything else”. She did point out, however, that “for short segments of de-lamination, this can be treated with a stent graft”.
Drawing her presentation to a close, Teodorescu moved on to discussing bovine carotid artery grafts. “These,” she averred, “have been introduced a while back, and initially, there were very good reports of both assisted and secondary patency.” A larger study that she used as an example actually, as she framed it, negated the good results of primary patency, as it only had 32% at a year, but there was a very good secondary patency of 78%.
Using another study example, Teodorescu stated that, upon comparison between bovine carotid grafts and PTFA, primary and primary-assistant patency between the two grafts were “essentially the same”, but secondary patency for the bovine carotid graft was “actually statistically different and improved: 67% compared to 38%,” but with “no difference in infection rate”. Lower infection rates, she stated, had been postulated as one of the advantages of the bovine carotid, but that this did not pan out in this study. The authors of this study postulated that the better results of the bovine carotid were due to there being less of a mismatch between the elastic properties of the graft and the blood vessels. Teodorescu adds, however, that “the use of these grafts petered out over time”, with some of this being due to cost and that “it wasn’t available everywhere in all markets, in addition to fear of aneurysm degeneration”. Despite this, she feels that they can be useful. “We use these occasionally as an interposition graft to repair an aneurysmal fistula. When we reviewed our data of70 bovine carotid grafts compared to 111 PTFE for this indication, we actually saw that the bovine carotids performed much better in terms of primary and secondary patency, and they were less likely to be abandoned.”
In her conclusion, Teodorescu stated that there are several conduits available to create access, although the options are “dependent on patient characteristics; obviously, if there are veins in a suitable patient, do a fistula before you use a graft”. Adding her final thoughts, however she stated that she was “wondering that, with the new advent of technology coming—especially bioengineered grafts—if we’ll be able to say something different over time”.
