Fistula Interventions: Less Is More

For over a decade,^1,2 approximately 80% of patients with ESKD initiated hemodialysis (HD) with a central venous catheter, despite recommendations to use an arteriovenous fistula (AVF), the preferred vascular access for HD.^3,4 In this issue of JASN, Lee et al.⁵ examine the AVF outcomes of a representative incident elderly HD population of patients who underwent AVF creation within 6 months of HD initiation (76.9% without prior arteriovenous access surgery) and whose AVFs were used successfully for dialysis with or without assisted maturation within 6 months of AVF creation.

In this retrospective observational study using US Renal Data System data, Lee et al.⁵ found that nearly half (44%) of AVFs required one or more interventions to facilitate maturation (prematuration interventions) so that the AVF could be used for dialysis. Furthermore, increasing prematuration interventions were associated with progressively shorter functional AVF patency and higher frequency of postmaturation interventions. Finally, AVF with four or more prematuration interventions had the highest risk of functional primary patency loss and AVF abandonment. These findings have significant clinical and economic implications for patients and the health care system, respectively.

In a large, international study involving multidisciplined stakeholders and patients on HD, vascular access function was deemed to be the most important vascular access outcome for patients, and it was identified as the highest vascular access research priority.⁶ Vascular access function was defined as use of a vascular access without the need for interventions.⁷ The study by Lee et al.⁵ highlights that current practice patterns may not align with patient interests, particularly when prematuration interventions lead to more postmaturation interventions and shorter time periods of “complication free AVF use.”

Additionally, the magnitude of the problem is likely underestimated, because Lee et al.⁵ only considered those who had an AVF created within 6 months of HD start and used within 6 months of creation. Those who either did not have an AVF created in that timeframe or did not use it within 6 months may be systematically different (indication bias) with comorbidities and/or vessel characteristics known to associate with poor AVF maturation.⁸ Because of the current pressures imposed by guidelines, regulators, insurers, and the Fistula First Catheter Last Initiative, many of these patients would likely undergo AVF creation, with greater rates of interventions to assist AVF maturation and use.

Not surprisingly, this study reveals that patients who had assisted maturation were more likely to have diabetes, coronary artery disease (myocardial infarction), peripheral vascular disease, obesity, and greater overall comorbidity—factors associated with poor AVF maturation.^8,9 Furthermore, the mean AVF primary functional patency was 4.3 months, and time to abandonment after maturation was 5.4 months, similar to some studies of arteriovenous graft outcomes. This raises questions about the process of “patient selection” for vascular access. Should nephrologists be selecting patients simply for vascular access (e.g., AVF) or selecting the access type to fulfill the needs of the patient’s dialysis prescription? Patients in Japan attain successful AVF creation, early cannulation,^10,11 and use¹² in part due to differences in dialysis prescription, with median blood flow rates of 200 versus 400 ml/min, smaller needles, and longer dialysis times (4 versus 3 hours). Thus, the current demands on an AVF to fulfill a dialysis prescription in North America are greater than in Japan, almost justifying the aggressive facilitative interventions to mature the AVF to a caliber great enough to meet the high dialysis demands. This paper reveals that such an aggressive approach has consequences of further interventions and shortened functional patency but unknown effect on dialysis performance. We urgently need a fresh approach to both “patient selection” and “access selection” to be considered jointly in the context of current patient realities (their challenging comorbidities and vessel characteristics) and the fast-paced dialysis environment (dialysis prescription, provider skillset, and resources). Until we do so, there will be continual mismatches of patient eligibility for AVF, resulting AVF quality, and its ability to meet required dialysis prescriptions-leading to more interventions, patient dissatisfaction, and rising costs.

Thoughtfully chosen and correctly applied interventions can enhance and prolong AVF function. However, in the study by Lee et al.,⁵ of those who had prematuration interventions, 47.8% needed two or more interventions. Also, there was only a 1-month difference in mean functional primary patency between those who had unassisted and assisted maturation, suggesting that most patients will get interventions after the AVF is first used. Notably, AVF abandonment was similar between AVFs with unassisted or assisted maturation—could this be due to interventions performed postmaturation? Repeated angioplasties induce vessel endothelial injury with consequent aggressive neointimal hyperplasia, rapid restenosis, and reduced AVF survival.^13,14 A typical vascular access intervention rate is approximately 1.9 per patient per year.¹⁵ The rates of postmaturation AVF interventions in this study were 6.0±12.4 versus 7.1±18.8 per patient per year in patients with assisted versus unassisted AVF maturation, respectively; these intervention rates are higher than those historically seen with arteriovenous grafts.

What is driving these interventions? It is unknown what the indications for interventions were and if or how surveillance techniques were used. Additionally, patients from for-profit and freestanding facilities were more likely to have assisted maturation procedures compared with those in nonprofit and hospital-based facilities, suggesting a potential role of financial incentives. Although a dramatic increase in reimbursement for procedures in the outpatient setting occurred early in the mid-2000s, it plateaued during the timeframe of this study.¹⁵ The 2017 bundled codes effectively reduced reimbursement for the repair and maintenance of dialysis vascular access¹⁵—the long-term effects on AVF interventions, patency, and use are unknown.

Finally, the rates of intervention may have been further underestimated by their method of competing risk analysis, which may not have fully accounted for the complex effect of time within their group categorization. Validated statistical methods of competing risks (e.g., death) in the context of repeated events (e.g., interventions and thrombosis) in the presence of a terminal event (access abandonment) are challenging, relevant for dialysis studies, and actively being investigated.¹⁶

As a closing reminder, prior data on high intervention rates of arteriovenous grafts were a primary impetus for the nationwide emphasis on greater AVF creation. Yet, this study reports similar or higher intervention rates compared with those historically reported in arteriovenous grafts. Indeed, patient characteristics have changed over two decades, and a “one size fits all” approach to AVF creation and use clearly is inappropriate given the overall AVF nonuse of 51%⁵ and the consequent high intervention rates required to facilitate and maintain AVF use. There is an urgent need for a thoughtful approach to vascular access selection that includes the potential need for interventions and their effect on AVF patency and future interventions. Studies are required to not only help predict which patients will likely have AVFs that will mature but also, those that will require procedures to assist maturation and patency. There is currently a paucity of validated algorithms to help select vascular access, and prior prediction tools for AVFs that fail to mature are outdated. The energy, resources, and educational efforts put into the original nationwide Fistula First initiative were highly successful in moving the needle to create more AVFs. We now need to revitalize research in vascular access and redirect our energies, efforts, and resources to updating and educating nephrologists, interventionalists, surgeons, dialysis staff, and associated trainees on how to properly assess and individualize approaches to vascular access choice and appropriate management. The goal remains unchanged: to help each patient attain a reliable dialysis access that can provide the prescribed dialysis for each patient’s individual circumstances with as few complications and interventions as possible.¹⁷

Disclosures

None.