Purpose: The transradial approach for endovascular intervention of problematic arteriovenous fistula (AVF) represents an alternative to direct puncture which can allow diagnosis and treatment of arterial and venous components through a single access. We share our institutional experience and explore the safety and efficacy of the transradial approach . Methodology: We conducted a retrospective analysis of 76 transradial approaches that were performed on 49 patients at our centre between 2018 - 2021 for intervention in problematic AVF. There were 21 female patients (42.8%) and diabetes (77.5%) was the most common cause of renal failure. Of the AVF treated there were 49 (64.5%) radiocephalic, 13 (17.1%) brachiocephalic, 9 (11.8%) brachiobasilic and 5 radiobasilic (6.6%). The index lesion treated was juxta-anastomotic in 62% of cases and venous lesions in the remaining 38%. Data were obtained from patient medical records and routinely performed post-operative surveillance ultrasonography. Results: There were 74 (97.3%) successful transradial approaches performed resulting in an average increase in volume-flow rate of 342mls/min (p<0.001). The 6-and-12 month functional patency rate was 90.7% and 81.8% respectively. The average procedure time was 64 minutes. There were no complications requiring further intervention, there was no hand ischaemia and no radial artery occlusion. There was 1 (1.31%) procedure complicated by a haematoma managed conservatively. Conclusion: Overall, the transradial approach for endovascular intervention of problematic arteriovenous fistula can offer a safe alternative to direct puncture and should be considered when there are simultaneous juxta-anastomotic and venous lesions.

Vascular Ultrasound is a useful modality for the diagnosis and monitoring of peripheral and central vascular disorders. Whilst it is relatively cheap and non-invasive, vascular ultrasound may be inaccurate, result in career limiting injury to the sonographer, and is also reliant on skilled sonographers to be performed. Vascular Accesses for Haemodialysis benefits from vascular ultrasound. The results however may be compromised by lack of patient compliance with appointments, accuracy of scans and experience of the sonographer. We present here a novel solution involving the use of a robotic ultrasound device that is able to construct tomographic images from an upper limb. These images are then analysed by artifical intelligence to detect vascular structures, which can then be reported by sonographer/ reporting physician. The results can then be distributed via cloud based services to inform the patients health practitioners. We have adpated this solution to enhance care for vascular access conduits and present these results for consideration.

Abstract Introduction Juxta-anastomotic stenosis (JXAS) is a common problem afflicting the arteriovenous fistula (AVF). This study aimed to evaluate the safety and long term efficacy of an Interwoven Nitinol stent (Supera, Abbott Vascular, Santa Clara, USA) in the treatment of radio-cephalic AVF JXAS stenosis. Methods A single-centre, retrospective, observational study was conducted of patients with failing AVF due to JXAS stenosis treated with an interwoven nitinol stent. End points included JXAS target lesion primary patency, access circuit primary patency and assisted access circuit primary patency, and Endovascular intervention rate (EIR). Results Sixty patients were treated with a Supera Stent in the JXAS between February 2014 and March 2020. One patient was excluded (AVF used for illicit drug use), leaving fifty-nine patients (67.8% male, mean age 66.9±11.4 years (Range 40-84)) with typical medical co-morbidities. 45.8% of patients had previous AVF intervention. The stent was inserted with a 100% technical success rate with a mean follow up of 729.6 ± 456.0 days (range 5 to 2182 days). JXAS target lesion primary patency was 68.2 +/- 6.6%, 53.3 +/- 7.5% and 46.2 +/- 8.1% at 12 months, 24 months and 36 months respectively. The EIR was .64 (0- 3.29) procedures/patient/year, after which the assisted access circuit primary patency rate was 94.3 +/- 3.2% at 12 months, 24 and 36 month time points. Conclusion Interwoven nitinol stent treatment of the failing AVF with juxta-anastomotic stenosis results in promising 3 year JXAS patency, with a low rate of endovascular re-intervention for those circuits developing restenosis. All AVFs were maintained over 3 years, demonstrating this treatment allows for long term radio-cephalic AVF vascular access.

PURPOSE RI has been used to predict the likelihood of AVF maturing (2) Theoretically, as a stenosis progresses to obstruct more of the vessel lumen, the resistance increases(1). The aim of this study was to review correlation between Resistance Indices (RI) and time to intervention and identify a range of RI which will help predict a poorly functioning AVF. either as a stand-alone value or in conjunction with other parameters such as volume flow of the circuit. METHODOLOGY This is a retrospective study of all AVF studies performed at Western Sydney Renal Dialysis service (WRADS) with data including Volume flow (VF), RI, minimal luminal diameter (MLD) and time to intervention determined on Duplex Ultrasound. Receiver Operator Characteristic Curves determined the normal and abnormal values with survival analysis also performed, with time to intervention. RESULTS Over 2,000 ultrasound studies of AVF were included in the analysis, with ranges of RI (ranges from 0.26 to 1.0) CI 95%. P 0.05. RI changes of about 0.7 indicate change in the flow of the AVF, this also can be linked to other markers of dysfunction. CONCLUSION Determining what are normal and abnormal RI in AVF can help predict how well functioning an AVF is and may provide a benefit to clinical pathways. References 1. Allon M, Imrey PB, Cheung AK, Radeva M, Alpers CE, Beck GJ, et al. Relationships Between Clinical Processes and Arteriovenous Fistula Cannulation and Maturation: A Multicenter Prospective Cohort Study. American Journal of Kidney Diseases. 2018;71(5):677-89. 2. Chiang W-C, Lin S-L, Tsai T-J, Hsieh B-S. High resistive index of the radial artery is related to early primary radiocephalic hemodialysis fistula failure. Clinical Nephrology. 2001;56(3/2001):236-40.

Background: The clinical utility of native arteriovenous fistula (AVF) has been limited by prolonged time for maturation, low overall maturation rate, and subsequent abandonment. Endovascular intervention is increasingly accepted as first-line therapy for AVF stenosis. The objective of this study was to evaluate AVF formation outcomes when early endovascular intervention was selectively performed to produce timely AVF maturation. Methods: a retrospective study (February 2014 to February 2020) of 82 AVF consecutive patients (mean age, 62.5±13.5 years) with ESRD who had undergone AVF construction at a single institution. 4-year AVF patency, vascular diameters, dialysis parameters, reintervention rate, and mortality were analysed. Results: Radiocephalic AVF was the most common fistula made (71 patients; 88.6%). Evaluation at a mean of 46.2±56.0 days after formation revealed 33 immature AVFs (40.2%). 19 patients underwent angioplasty and/or stenting to ensure timely maturation of the AVF. 93.9% of AVFs reached functional patency (maturation) by 6 months. Mean time to maturation was 67.8±65.9 days. After maturation, the primary access functional patency was 82%±4.3% at 6 months, 58%±5.5% at 12 months, and 34%±6.8% at 48 months. The primary assisted access functional patency was 95%±2.4% at 6 months, 90%±3.3% at 12 months, and 83%±4.7% at 48 months. 121 endovascular interventions were performed, a reintervention rate of 0.37 procedure/patient year. Mean AVF survival time was 5.9±0.26 years from maturation. Only 12 thromboses occurred after initial follow-up. All were salvaged using endovascularly, producing 100% total secondary functional patency at 4 years. Conclusions: AVF maturation rate and interval to maturation were improved with selective early endovascular intervention, providing near universal maturation. Ongoing endovascular reinterventions allowed for a low reintervention rate and long-term patency, providing reliable long-term renal vascular access.

Purpose: The WRAPSODY™ Cell-Impermeable Endoprosthesis (Merit Medical Systems, Inc.) is a new and unique self-expanding stent. It is licenced for use in the treatment of arteriovenous fistula (AVF) and graft circuit stenosis. Methods: Consecutive patients presenting to a single vascular unit with occlusive disease of their dialysis access circuits, which had failed at least three standard interventions, were treated with venoplasty followed by WRAPSODY™ endoprosthesis deployment. Patients were followed up clinically and angiographically post operatively for up to 24-months post insertion. Outcome measures included 30-day adverse events and primary patency rates (PPR) of both the target lesion and the dialysis circuit. Results: Treatment sites included the cephalic arch (7), basilic vein (2), upper limb central veins (6) and lower limb central veins (2). Native vein disease was treated in eleven cases and in-stent re-stenosis in five cases. Twelve procedures were performed for dysfunctional circuits and four for failed circuits. Thirteen patients received a total of 29 stents. The average number of primary lesion treatments by conventional venoplasty in the preceding year was 3.3 per patient. All initial procedures were successful. No patient had an adverse event related to the WRAPSODY™ device. At 3, 6, 12, 18 and 24-months, the target lesion PPR were 100% (13 of 13), 100% (8 of 8), 80% (4 of 5), 100% (2 of 2), 100% (1 of 1) respectively. While at 3, 6, 12, 18 and 24-months, the dialysis circuit PPR were 100% (13 of 13), 63% (5 of 8), 40% (2 of 5), 50% (1 of 2), 100% (1 of 1) respectively. All dialysis access circuits remained functionally patent during the study. Conclusion: The WRAPSODY™ endoprosthesis is safe and effective for treatment of recalcitrant occlusive lesions in renal access circuits with good long-term patency.

Purpose: 3D printing enables the manufacture of patient-specific anatomical models that improve patient consultation and offer novel opportunities for surgical planning and training. However, the multistep preparation process can lead to inaccurate anatomical representations which may impact clinical decision making detrimentally. Here, we validate the dimensional accuracy of vascular anatomical models manufactured using common 3D printing modalities including Fused-Deposition Modelling (FDM), Stereolithography (SLA), Selective Laser Sintering (SLS), and MultiJet (MJ) 3D printing. Methodology: A blinded dimensional accuracy study of 3D-printed models derived from patient abdominal aorta Computed Tomography Angiograms (CTAs) was performed. First, digital 3D models of patient anatomy were produced followed by the addition of measurement reference points and processing. Models were manufactured via FDM, SLA, SLS and MJ 3D printing, respectively. The accuracy of digital and 3D-printed models was assessed and compared to original CTA data to investigate errors introduced at different steps of the 3D printing process. Results: All printing modalities reliably produced hand-held patient-specific models of high quality. Quantitative assessment revealed an overall printed model deviation of -1.29 ± 0.58% (MEAN ± STDEV), -0.43 ± 0.48%, and +0.74 ± 0.64% for FDM, SLA, and SLS-printed models, respectively, compared to unmodified CTA data. Comparison of digital 3D models to CTA data revealed an average error of +0.62% resulting from digital anatomical segmentation and processing. Deviations resulting from the print modality alone were -0.67 ± 0.58%, +0.19 ± 0.48%, and +1.36 ± 0.64% for FDM, SLA, and SLS-printed models, respectively. Conclusions: This study established novel quality assurance procedures and revealed a high level of dimensional accuracy of 3D-printed patient-specific vascular anatomical models, suggesting they meet the requirements for clinical applications.

Purpose: Acute aortic syndrome (AAS) forms a group of life-threatening vascular emergencies with high rates of misdiagnosis. However, under- and over-investigation of patients using computerised tomographic aortography (CTA) carries significant risk. The aim of this study was to determine whether CTA scans were performed in proportion to a patient's risk of AAS, and the incidence of AAS, for different ethnic groups. Methodology: All atraumatic CTAs of the thoracic aorta performed in adults (>15 years old) with suspected AAS, between January 2009 and December 2019, at Auckland City Hospital in New Zealand, were included. Patients were risk stratified using the aortic dissection detection risk score (ADD-RS). The primary outcomes were the ratio of CTA scanning rates to rates of positive CTAs, and the incidence of AAS. Results: In total, 1,646 CTAs were performed on 1,543 patients. Indigenous Māori (33.5%) and Pacific Islanders (34.9%) were more likely to be at high-risk of AAS (ADD-RS>1) compared to patients of other ethnicities (25.4%; p=0.0018), with significantly higher age-standardised AAS incidence (6.9 in Māori and 5.3 in Pacific Islanders vs. 2.3 per 100,000 person-year in other ethnicities; p<0.0001 and 0.0001, respectively). However, despite this higher incidence of AAS, disproportionately fewer CTA scans were requested in the ED for Māori (9.2 CTAs per AAS diagnosis; p=0.062) and Pacific Islander (9.2 CTAs per AAS diagnosis; p=0.045) patients compared with those of other ethnic groups (13.8 CTAs per AAS diagnosis). Conclusions: Despite the significantly higher risk and age-standardised incidence of AAS among Māori and Pacific Islander patients, disproportionately fewer CTAs were requested in these patients relative to patients of other ethnicities. Therefore, clinicians should account for the increased risk of AAS in Pacific Islander and indigenous Māori populations when investigating suspected AAS.

Purpose Endoleak is a well-known complication of endovascular aneurysm repair (EVAR). Differentiation between different types of endoleak (Types I, II, III and IV) remains a diagnostic challenge and can significantly alter management. Subtraction and iodine mapping is a new application of single source computed tomography (CT) technology that has the potential to be used as a diagnostic tool for endoleak. This study explores the utility and viability of iodine mapping as a tool for the diagnosis and differentiation of endoleak as an alternative to existing imaging modalities. Methodology We conducted a pilot study using iodine mapping of subtraction CT technology compared to other diagnostic modalities such as traditional multiphase CT angiography, and dual energy CT for detection and evaluation of endoleak. A literature review was conducted, and our search parameters were extended across Embase and Medline. Results Pulmonary perfusion studies have demonstrated that single-source subtraction CT is as efficacious as dual-energy source for iodine map reconstruction, with reduced contrast-to-noise ratio. Dual-energy CT has been demonstrated to yield similar sensitivity and specificity, with lower radiation exposure when compared to traditional multiphase CT. Subtraction iodine mapping offers improved parameters such as reduced iodinated contrast burden, radiation dose and cost effectiveness compared to other CT modalities. Conclusion Subtraction with iodine mapping from a single-source CT has the potential to be an alternative imaging modality for identification and interrogation of endoleaks. Our pilot study demonstrates the benefits of this modality in the investigation of endoleaks following EVAR. Further validation studies comparing iodine mapping to current gold standard of multi-phase CT would provide robust data on efficacy of iodine mapping for the detection of endoleaks after EVAR.

Endovascular management of the arterially placed central venous lines – a single center retrospective review Jhanvi Dholakia. Anantha Narayanan, Lupe Taumoepeau Wellington Hospital, New Zealand Central venous lines (CVLs) are a fast and effective means of acquiring central access in many high acuity clinical situations. A complication of this procedure is the inadvertent arterial puncture and placement of the line. This is associated with significant morbidity by way of bleeding, thrombosis, stroke or death. Intervention for this complication has traditionally been open surgical repair of the arterial puncture site. However with evolving techniques, endovascular repair may improve morbidity associated with cut down procedures. In this single centre retrospective review, we present 7 cases of iatrogenic arterial punctures during attempted CVL insertion and portacath insetion, that were treated endovascularly. Of these, 6 patients were treated with vascular closure devices (Angioseal) and 1 patient underwent insertion of a covered stent. Post-operatively, one patient treated with a closure device developed brachial artery thrombosis at the site of their pre-emptive brachial cutdown site, necessitating open repair but recovered from this without any significant long term complications. There were no other cases of stroke or intervention related morbidity/mortality post intervention. This small series of a rare but devastating complication adds to the growing literature supporting the use of endovascular techniques and vascular closure devices in the event of iatrogenic CVL injury, in the context of appropriate resource availability and a multi-disciplinary approach.

Purpose To observe the level of agreement in the real-world reporting between CTA and three standard US measurements of the transverse AP, sagittal AP and coronal (left to right) infra-renal abdominal aortic aneurysm (AAA) diameter. Methodology A review of the Otago Vascular Diagnostics database of abdominal aortic aneurysms AAA, where ultrasound and CTA diameter data were available within ≤ 90 days of each other, were compared. The infrarenal aorta ultrasound diameter measurements in both transverse AP and sagittal AP, along with a coronal decubitus image of the aorta was collected. No transverse measurement was performed from the left to the right of the aorta. Results Three hundred twenty-five participants (238 males, mean age 76.4± 7.5) with mean ultrasound outer to the outer wall, transverse AP and sagittal AP diameters of 48.7± 10.5 mm and 48.9 ± 9.9 mm, respectively. The coronal diameter measurement aorta from left to right was 53.9 ± 12.8 mm in the left decubitus window. The mean ultrasound max was 54.3 ± 12.6 mm. The mean CT diameter measurement was 55.6 ± 12.7 mm. Correlation between the CT max and ultrasound max was r2 =0.90, 95% CI and CT with the coronal measurement r2=0.90, 95% CI; CT max and AP transverse were r2=0.80, 95% CI; and CT with AP sagittal measurement r2=0.77, 95% CI. Conclusion The decubitus ultrasound window of the abdominal aorta, with measurement of the coronal plane, may offer an alternative approach to measuring the infrarenal abdominal aortic aneurysm and should be considered when performing surveillance of all infra-renal AAA