A critical review of surgical strategies to minimise venous stenosis in arteriovenous grafts

It is inevitable that complications arising from surgical procedures are ascribed to surgical technique, and this applies to venous stenosis (VS) in arteriovenous grafts. However, despite a wide range of cellular studies, computer modelling, observational series and clinical trials, there remains uncertainty on whether surgical technique contributes to VS. This article reviews evidence from basic science, fluid dynamics and clinical data to try and rationalise the main surgical options to modify the occurrence of venous stenosis. There is sufficient data from diverse sources to make recommendations on clinical practice (size of target vein, shape of anastomosis, angle of approach, distance from venous needling, trauma to the target vein) whilst at the same time this emphasises the need to carefully report the practical aspects of surgical technique in future clinical trials.

Long-term outcomes following thrombolysis of arteriovenous grafts

Background: Thrombolysis for arteriovenous grafts (AVG) yields high technical success rates, however, long-term outcomes are unclear. We conducted a multicenter retrospective cohort study to analyze 5-year patency rates following AVG thrombolysis. Methods: All patients who underwent AVG thrombolysis between 2005 and 2015 at three academic hospitals were included. Prospectively maintained institutional nephrology and radiology databases were used to record demographic, clinical, and AVG characteristics. The primary outcome was primary patency, defined as AVG access survival without re-intervention including angioplasty ± stent with/without re-thrombolysis. Secondary outcomes were assisted primary patency and cumulative patency, defined as AVG access survival until re-thrombosis requiring re-thrombolysis or abandonment, respectively. Technical success was defined as restoration of flow with <30% residual stenosis. Patients were followed until 2017. Patency rates were assessed using Kaplan–Meier survival analysis and Cox proportional hazards were calculated to determine associations between covariates and patency loss. Results: Seventy-four patients underwent AVG thrombolysis during the study period with a median follow-up period of 21.4 (IQR 8.3–42.8) months. The average age was 58.6 years with a high rate of comorbidities, including hypertension (82.4%) and diabetes (54.1%). Thrombolysis technical success was 96%. There were 147 re-interventions in 46 patients, of which 98 were re-thrombolysis (mean re-intervention rate of 1.27/patient/year). Primary patency at 1, 3, and 5 years were 43.2%, 20.2%, and 7.7%. Assisted primary patency at 1, 3, and 5 years were 47.5%, 20.2%, and 7.7%. Cumulative patency at 1, 3, and 5 years were 75.0%, 38.8%, and 22.6%. Cox proportional hazards analysis demonstrated no associations between demographic, clinical, and procedural characteristics and patency rates. Conclusions: Despite a high technical success rate, thrombolysis for AVG dysfunction is associated with poor long-term patency. Future studies are needed to determine risk factors for re-thrombosis to identify patients who will benefit from AVG thrombolysis in the long-term.

Brachio-azygos transthoracic arteriovenous grafts for hemodialysis patients with bilateral central venous obstruction: A small case series

Background: It is difficult to find a reliable outflow vein for vascular access in hemodialysis patients with bilateral central venous obstruction. The lower extremity veins are currently used as the most common alternative veins to make a new vascular access. However, in patients not amenable to make lower extremity access, intrathoracic vein should be considered as an outflow vein, but there are limitations in its use due to postoperative complications. Methods: We introduce a series of cases that underwent arteriovenous graft operation using an intrathoracic vein, the azygos arch, as an outflow vein. Brachio-azygos transthoracic arteriovenous graft is a surgical procedure that anastomoses the azygos arch and the brachial artery with 7 mm ringed polytetrafluoroethylene graft via lateral thoracotomy without median sternotomy. Results: The chest tubes of the patients were removed on the third postoperative day and they discharged within a week. About 1 month later, hemodialysis was initiated through the BATAVG, and it has been used without access dysfunction. Conclusion: Brachio-azygos transthoracic arteriovenous grafts were performed using the azygos arches without major complications. The azygos arch can be a good alternative outflow vein to make a new vascular access for hemodialysis patients with bilateral central venous obstruction.

Screening and surveillance of venous stenosis in AVG: Is it time to rethink our assumptions?

Guidelines make no firm recommendations about surveillance of arteriovenous grafts as several randomised trials (RCT) have not shown a clear benefit in patency. However a more thorough review of these RCT based on epidemiological principles reveals significant limitations. In particular a key weakness of these older studies is the interventions performed for venous stenosis detected that was largely angioplasty. However, the observational data of modern stent-grafts shows a clear benefit over angioplasty, and thus seems to suggest that a modern well considered RCT is now mandated.

TP10.2.4Access surgery for dialysis patients during COVID-19

Aims To describe the organisation of a triage system and COVID-19-free surgical pathway, and to assess the outcomes after its implementation for planned dialysis access surgery for patients during the first wave of the COVID-19 pandemic in the UK. Methods In response to the suspension of elective operations due to SARS-CoV-2 outbreak, we devised a COVID-19 free surgical pathway performed in NHS and an independent hospital. We audited the outcomes of its application in patients requiring access surgery between 17 April and 15 September 2020. The data was collated, analysed, and presented at clinical governess. We are looking to re-audit for the second wave in the coming months. Results A total of 235 cases were listed, and 203 procedures were performed. Thirty-two cases were cancelled and the top reason for cancellation was patient refusal. Of the procedures carried out, 47% (n = 96) were arteriovenous fistula formation, 42% (n = 84) were peritoneal catheter procedures, and 11% (n = 23) were arteriovenous grafts. The postoperative complication rate by day 7 was 13.3% (n = 27), by day 30 was 6.9% (n = 14) and they are similar to pre-COVID outcomes. By performing a definitive dialysis access, we avoided the significant morbidity and mortality associated with tunnel-line based dialysis. No patients acquired COVID-19 or died from its related illnesses in 30 days. Conclusion Our results confirmed that our pathway was effective in delivering dialysis access in a timely manner and COVID safe. Our model is safe, easy to replicate COVID-19-free pathway and can be used during similar challenges in the future.

Stable incidence and survival of arteriovenous fistulas over 39 years: A long-term national cohort study

Introduction: The age and number of comorbidities in the hemodialysis population has increased over time. This may influence the construction and survival of the arteriovenous fistula (AVF). The present study explored the incidence and survival of AVFs over a period of 39 years. Methods: A retrospective cohort study was conducted based on Danish registries. Incident hemodialysis patients between 1977 and 2015 were included. The incidence of AVF and factors associated with the construction of an AVF were described. Risk factors for AVF survival and repair were explored by Kaplan Meier and Cox proportional hazard analysis. Results: The total number of arteriovenous accesses (AVF and arteriovenous grafts) were 10,187 and there were 4201 central venous catheters (CVC). No significant difference in the proportion of AVFs during the 39 years was seen. Age and renal diagnosis did not influence the proportion of AVFs. Patients with CVCs were found to have a significantly higher prevalence of comorbidities ( p < 0.01). AVF survival remained stable during the 39 years. The first constructed AVF had the best survival, 35% still functioning after 15 years. Factors such as brachiocephalic AVF, female sex, and diabetic nephropathy increased the risk of AVF failure (Odds Ratio (OR): 2.46, 95% Confidence Interval (CI) (2.29–2.65), 1.17 (1.10–1.25), and 1.21 (1.12–1.3)), respectively. Conclusion: Despite an older dialysis population, the proportion and survival of the AVF in the Danish dialysis population has not changed, probably because of increased awareness of AVF as the first choice of vascular access and improved surveillance, surgery, and repair.