One of the most common, and easily addressed, complications with AVFs is development of primary and recurrent stenoses in various sites of the vascular access. Each AVF type behaves differently as to where stenoses typically occur. Brachiocephalic AVFs (BCAVFs) are typically plagued by stenoses at the cephalic arch, with reports describing up to a 77% prevalence of significant stenoses at this site. Angioplasty has been a mainstay of treatment for dialysis access stenoses, although literature has supported the use of stent graft placement compared with angioplasty alone.[11–14]
We found the luminal diameter at the cephalic arch decreased by 18.9% per month after the first exclusive angioplasty and 16.5% per month after the first stenting procedure among patients with a BCAVF. Restenosis rates were relatively similar between high-pressure and standard angioplasty procedures, suggesting consistent effectiveness when a high-pressure balloon was required to eliminate the lesion. Consistent with the literature, restenosis rates were higher after the first bare metal stent (18.1% per month) compared to stent graft (8.0% per month). Overall, these findings indicate that once a patient presents with a cephalic arch stenosis and is treated with an angioplasty or stent, they are at risk of having a 50% stenosis in 2.65 or 3.03 months, respectively. Stated differently, a patient with a post intervention residual stenosis of 10% after their first exclusive angioplasty or stent is estimated to progress to have a 67% or 60% stenosis in 3 months, respectively. Restenosis rates were relatively similar across subsequent angioplasty or stent procedures during follow-up.
One of the longest retrospective studies involving hemodialysis upper arm AVFs found a 34% primary and 82% secondary patency rate at one year, although there was no differentiation between brachiocephalic versus brachiobasilic fistulae. This study found the interval for re-intervention was 10.6 months in upper arm AVFs, but did not specify the exclusivity or combinations of intervention types nor the site of malfunction. We observed the interval for re-intervention after exclusive angioplasty or stenting procedures was approximately 3 months. However, the confidence limits for restenosis rates and re-intervention times were typically large, which represents high patient-to-patient variability.
Future studies are needed to identify the predictors of restenosis risk at the cephalic arch. Arterialized pressures, intimal hyperplasia, and turbulence are likely culprits for rapidly recurrent and possibly angioplasty-resistant stenoses. Fistula age may also be affecting the durability of the vessel wall. Neo-intimal hyperplasia and turbulence has been suggested as a cause of rapid recurrent in-stent stenosis.[11, 16, 17] For bare metal stents, the intima continues to be exposed to turbulent flow and biochemical constituents of blood vessels through the interstices, and may explain why lower restenosis rates were seen for stent grafts. Although not evaluated, several incidences of stent fracture were noted as causing recurrent stenosis; oftentimes, angioplasty and/or stenting was required to improve the flow and appearance.
Our study has several strengths, the most obvious of which includes the focus on exclusive interventions that afforded the ability to reasonably assess restenosis rates at a specific lesion site. In addition, the analysis included a large number of patients treated by various practitioner types in a broad geography. All these factors represent clinically relevant interventions and consequently, this data likely represents reproducible, real world outcomes. However, this study cohort may not be fully generalizable and is not representative of the groups of patients who had unremarkable complications upon evaluation, or a mixture of interventions (e.g. thrombectomy and high-pressure angioplasty). Also, drug eluting balloons were not evaluated due to many factors, including minimal adoption in the outpatient setting that is likely secondary to cost and familiarity with the equipment.
The retrospective nature of this study is an inherent weakness. Also, stenosis measurements may have varied by practitioner, although a small random sampling of cases with image review showed good agreement with reported degrees of stenosis. Given the large number of centers, inter-operator variability also poses a problem when evaluating the need for stenting, stent type, and general personal practice regarding stenting versus angioplasty alone. Also, the precise morphology of the stenosis, focal versus long segment versus multifocal, was not clearly specified. While morphology may play a role in the long-term success of endoluminal interventions, it is not clear stratifying the results based on morphology would have any impact. Lastly, these models of recurrence are based on a linear progression of stenosis development warranting treatment. It is feasible that after numerous interventions, the rate of progression may change, either for better or worse.