The Saturday morning session of the American Society of Diagnostic and Interventional Nephrology (ASDIN) 19th Annual Scientific Meeting (17–19 February, Orlando, USA) played host to a stimulating debate between Edgar Lerma (University of Illinois at Chicago, Chicago, USA) and Loay Salman (Albany Medical Center, Albany, USA), the question: should an asymptomatic high-flow arteriovenous fistula (AVF) be ligated or preserved in a patient who has received a transplant and ended dialysis?
Salman started proceedings by laying out that transplantation remains the very best treatment for patients with end-stage renal disease (ESRD), but that a successful transplantation presents clinicians with the problem of whether to close their dialysis access. Setting out his stall as the pro-preservation speaker, Salman put forward that the evidence in favour of ligation for asymptomatic high-flow AVFs is not strong enough—particularly given the risks of complication the procedure presents.
The inconclusive nature of the evidence is suggested by a multi-national survey carried out by Bram M Voorzaat (Leiden University Medical Center, Leiden, The Netherlands) et al and published in The Journal of Vascular Access in 2019, Salman said. He pointed out that, among the 585 multidisciplinary respondents, it was found that, if an access had a “reasonable” flow of around 1000ml/min, there was a tendency to maintain it regardless of age. When the blood flow is more than 2500ml/min, however, there is a tendency to close regardless of age, as there also is with an ejection fraction of less than 30%. That study concludes that the “significant variability in preferences demonstrates that the current evidence is not convincing to recommend routine preservation or ligation”.
With this evidence base in mind, Salman presented the questions that he asks when faced with the issue of preservation or ligation. First among these is the status of the graft—Salman noted that many transplant patients will eventually end up back on dialysis, and that this means clinicians have a duty to ensure they do so in the best way possible.
Building his case, Salman asserted: “If you decide to ligate the access, there are certain risks you are exposing that patient to. Those include mortality with any necessary new access—patients who have already experienced graft failure have a worse mortality rate compared with those awaiting transplantation.
“There will be additional challenges around finding a new access, since some will already have been used, as well as the risk of maturation failure. These are all risks brought about just by ligating the previous access.”
His next question was simple: why ligate? The evidence does not show any proven benefit around patient mortality to ligation of access after a transplant, Salman argued, making reference to a 2019 Journal of Vascular Surgery study by Caitlin W Hicks (Johns Hopkins University School of Medicine, Baltimore, USA) et al that found little difference in mortality or graft failure risk with ligation.
Salman closed his argument by advising clinicians to “carefully weigh the benefits and risks of treating complications” against those of ligating an access, before stating clearly that, in the case of non-problematic arteriovenous (AV) access, ligation should not take place after transplant. He added that a randomised controlled trial (RCT) was needed to show its benefits before it could be routinely recommended—the COBALT study in England, he said, promises to provide the groundwork for a larger trial.
The case for ligation
Next up came Lerma, who introduced himself as “normally a nice guy” who “does not debate”. Nevertheless, he quickly began assembling his argument in favour of ligation, considering first how common cardiac complications are in chronic kidney disease (CKD) patients. He referred to a 2012 study in Nefrología that was led by Rocío Martínez-Gallardo (Hospital Infanta Cristina, Badajoz, Spain), which found that 17% of its 562 enrolled CKD patients developed at least one episode of pre-dialysis heart failure—one of the risk factors for which was the presence of AV access.
Another study in Clinical Transplantation, this one headed by Tabea Schier (Innsbruck Medical University, Innsbruck, Austria), found that the mean shunt flow among kidney transplant patients with heart failure symptoms who required closure was 2,197ml/min, compared with 851ml/min among patients who did not undergo shunt closure. The former number, Lerma contended, “fits the criteria of high-flow AV access”. On top of this, Lerma referenced a further study in the European Heart Journal by Yogesh N V Reddy (Mayo Clinic, Rochester, USA) et al that found, in a retrospective study with a cohort of 137 patients with an AVF, that 43% of patients with no prior history developed incident heart failure.
“So we know high-output cardiac failure is a potential complication of high-flow AV access,” Lerma determined from this evidence. AV accesses with a blood flow >1.5l/min are at particular risk, he said, especially when created in the upper arm. He described a blood flow/cardiac output ratio of >0.30 as a “valid screening tool to perform further cardiac testing”, and added that, “if no reversible cause for high-output heart failure is identified, a case can be made for flow reduction (banding) of the AV access”.
To progress his argument in favour of ligation, Lerma brought up two further studies. First was the 2019 Circulation-published study led by Nitesh N Rao (University of Adelaide, Adelaide, Australia) which concludes that “elective ligation of patent AVF in adults with stable kidney transplant function resulted in clinically significant reduction of left ventricular (LV) myocardial mass”. This is corroborated by the findings of the second study Lerma raised here, by Tania Salehi (University of Adelaide, Adelaide, Australia) et al, which suggest that the benefits of ligation on left ventricular mass (LVM) and LVM index “appear to persist in the long term”.
Summarising what he argued are ligation’s advantages, Lerma listed the LVM reduction found in the Salehi et al study, as well as the potential reduced cardiovascular risk, minimisation of risk of rupture and the cost. Finally, he spoke from experience: “Not all AV fistulas are created equal. Fistula closure should be done for stable kidney transplant patients with symptoms of overt cardiac failure, pulmonary hypotension or access-related complications such as aneurysms and steal syndrome.”
Addressing Salman’s arguments, Lerma said: “Regarding the risks, I feel that a patient-centric approach that includes patients’ preferences is more appropriate.” He said there may also be some benefits to a low-flow fistula patient keeping their fistula, but that those with flow >1l/min may have a propensity towards cardiac failure that justifies ligation. For patients who experience graft failure, he added, “banding may be in order”. He referred listeners lastly to a 2020 review in Advances in Kidney Disease and Health, to which he contributed, that proposes an algorithm for managing high-flow AV access.