Patency and Durability of Stent Grafts Placed in the Dialysis Circuit Cannulation Zone.

PURPOSE: To investigate the safety, durability, and patency rates of stent grafts (SGs) placed in the cannulation zone of hemodialysis access circuits. MATERIALS AND METHODS: From April 2020 to April 2023, all procedures with SGs placed in the cannulation zone were retrospectively analyzed. A total of 40 patients (25 men and 15 women) with SGs placed in the cannulation zone were included in the study. Mean age of the patients was 70 years. The Covera covered stent (BD, Franklin Lakes, New Jersey) was used in all cases. Of these, 26 were arteriovenous (AV) fistulae and 14 were AV grafts. SGs were placed for residual stenosis, perforation, aneurysm, and thrombosis. Follow-up outcomes were determined using follow-up angiographic images and included primary patency, primary-assisted patency, and secondary patency. RESULTS: The primary patency of the target lesion was 89% (SD ± 5) and 74% (SD ± 8.4) at 6 and 12 months, respectively. The primary-assisted patency was 89% (SD ± 5.2) and 78% (SD ± 7.6) at 6 and 12 months, respectively. Secondary patency of the access circuit was 97% (SD ± 2.5) at both 6 and 12 months. Mean follow-up was 332 days (range, 28-661 days). All SGs were successfully cannulated for hemodialysis. No cases of stent fracture or stent infection were observed during follow-up. CONCLUSIONS: SGs placed for cannulation zone pathologies can be safely cannulated for dialysis and have adequate short- and mid-term patency rates.

Complete stent graft relining of the hemodialysis access circuit for access salvage.

BACKGROUND: Stent grafts (SGs) are widely used in hemodialysis access procedures to maintain function and patency of the access circuit. There are no reports to date describing complete relining of the access circuit with SGs for extreme access salvage. OBJECTIVE: To report outcomes and experience with complete SG relining of the hemodialysis access circuit. METHODS: From April 2020 to May 2023, all hemodialysis salvage procedures that included complete relining of the access circuit with SGs were retrospectively analyzed from a prospectively collected database of 970 hemodialysis access interventions. SGs were placed for various pathologies including residual stenosis, perforation, aneurysm, and thrombosis. Follow up outcomes included primary patency, primary assisted patency, and secondary patency. RESULTS: A total of 16 patients were included in the study. Average stented length was 30 cm. Average follow up was 283 days (range 38-647 days). The primary patency of the entire covered segment was 80% and 68% at 6 and 12 months, respectively. The primary assisted patency of the segment was 88% and 77% at 6 and 12 months, respectively. Secondary patency of the access circuit was 94% at both 6 and 12 months. There were no issues with SG cannulation and zero cases of SG fracture or infection. CONCLUSIONS: Salvage of failing hemodialysis access circuits by complete SG relining should be considered for a limited subgroup of patients where the access circuit would otherwise be deemed unsalvageable. Complete SG relining has both good immediate outcomes and 6- and 12-month patency rates.

Stent Grafts Across the Elbow Joint for Access Salvage.

PURPOSE: Covered stent grafts (SGs) are currently being used in a wide variety of situations to maintain function and patency of hemodialysis access circuits. Stent grafts are rarely placed across the elbow joint (EJ), however, due to fear of stent fracture. This study reports on the experience and patency rates with SGs across the EJ. MATERIALS AND METHODS: From April 2020 to August 2023, all procedures with SGs placed across the EJ were retrospectively analyzed. A total of 21 patients with SGs placed across the EJ were included in the study. The Covera Vascular Covered Stent (BD, Franklin Lakes, New Jersey, USA) was used in all cases. Of these, 18 were arteriovenous (AV) fistulae, and 3 were AV grafts. Stent grafts were placed for various pathologies, including residual stenosis, perforation, aneurysm, and thrombosis. Follow-up outcomes were obtained from angiographic images on follow-up angiography and included primary patency, primary assisted patency, and secondary patency. RESULTS: The primary patency of the target lesion was 85% (CI=70%-100%) and 85% (CI=70%-100%) at 6 and 12 months, respectively. The primary assisted patency was 85% (CI=70%-100%) and 85% (CI=70%-100%) at 6 and 12 months, respectively. Secondary patency of the access circuit was 95% (CI=86%-100%) at 6 months and 89% (CI=75%-100%) at 12 months. The average follow-up duration was 393 days (range=27-768 days). There were no instances of stent fracture during follow-up. CONCLUSIONS: Stent grafts should be placed across the EJ for good short-term and mid-term patency rates. CLINICAL IMPACT: The placement of stent grafts across the elbow joint in hemodialysis patients for access salvage is controversial due to the fear of stent fracture or occlusion. This retrospective study evaluated the placement of stent grafts for access salvage in 21 patients for various etiologies. Good patency rates were seen out to 12 months and no stent fractures were observed. Although longer term data is needed, stent grafts should be considered an acceptable option for access salvage when treating lesions that cross the elbow joint.

Pave and Pop: A novel addition to the endovascular treatment of hemodialysis access aneurysms.

BACKGROUND: Hemodialysis access sites can be complicated by both true and false aneurysms with significant potential morbidity. Aneurysms have traditionally been treated by a variety of surgical methods. Less commonly, endovascular treatment with stent graft placement has been used as an alternative to open surgery. METHODS: Four patients with symptomatic aneurysmal disease in the hemodialysis access site were treated. All patients had stent grafts (SGs) placed across the diseased segment. Once the diseased segment was excluded, blood was drained from the aneurysm with an 18 g needle. All patients were seen in clinic at 1- and 3-months post procedure. RESULTS: All patients were able to receive adequate hemodialysis post procedure. Two patients were cannulated via the SG after 1 month. No aneurysm refilling was seen. No SG infections or fractures were seen. CONCLUSION: A novel addition to the endovascular treatment of aneurysmal disease in hemodialysis patients is described, that both excludes the aneurysm and drains it, providing improvement in the aesthetic appearance of the access site.

Early experience with the Abre venous stent for central venous stenoses and occlusions in hemodialysis patients.

BACKGROUND: Hemodialysis patients are prone to stenoses and occlusions throughout the access circuit. Central venous stenoses or occlusions (CVO) can be particularly challenging. There are many different types of balloons and stents available for treatment, including a new generation of dedicated venous stents (VS). In this study, we report our experience and patency rates with the Abre VS in central venous lesions in hemodialysis patients. METHODS: From April 2020 to May 2023, all procedures with Abre VSs placed for central venous lesions in hemodialysis patients were retrospectively analyzed from a prospectively collected database of 980 hemodialysis access interventions. Follow up outcomes were obtained from angiographic images on follow up angiography and included primary patency and primary assisted patency. Effective hemodialysis was considered a surrogate for access patency if no angiographic follow-up was available. RESULTS: A total of 15 patients with CVO were treated with the Abre VS. Technical success was 100%. All patients were able to achieve adequate hemodialysis after VS placement. Stents were placed across the thoracic inlet in 73% of patients. Post procedure primary patency at the target lesion site was 85% at 6 months and 70% at 12 months. Primary assisted patency of the circuit was 93% at 6 and 12 months. No stent fractures were observed. CONCLUSION: Treatment of CVO remains extremely challenging, especially when the lesion is located at the thoracic inlet. In these patients, VSs provide acceptable primary patency rates and allow patients to continue to receive effective hemodialysis. However, routine follow-up and re-interventions will likely be necessary to maintain patency in the long term.

A percutaneous biliary anastomotic reconstruction for a failed Roux-en-Y hepaticojejunostomy in a patient with cholangiocarcinoma: A case report.

We hereby report a case of a novel percutaneous biliary anastomotic reconstruction of a disconnected segment 2 bile duct to the roux limb in a patient with cholangiocarcinoma suffering from bile leak post trisegmentectomy and roux-en-y hepaticojejunostomy. The patient was not a candidate for surgical reanastomosis and was suffering from repeated episodes of cholangitis prior to our intervention. We were successfully able to resolve the patient's biliary symptoms and need for an external biliary collection bag using our technique. The patient's case and the details of our intervention with relevant imaging is discussed. A review on the management of biliary leak following roux-en-y hepaticojejunostomy is also included.

DCE-MRI of the liver: effect of linear and nonlinear conversions on hepatic perfusion quantification and reproducibility.

PURPOSE: To evaluate the effect of different methods to convert magnetic resonance (MR) signal intensity (SI) to gadolinium concentration ([Gd]) on estimation and reproducibility of model-free and modeled hepatic perfusion parameters measured with dynamic contrast-enhanced (DCE)-MRI. MATERIALS AND METHODS: In this Institutional Review Board (IRB)-approved prospective study, 23 DCE-MRI examinations of the liver were performed on 17 patients. SI was converted to [Gd] using linearity vs. nonlinearity assumptions (using spoiled gradient recalled echo [SPGR] signal equations). The [Gd] vs. time curves were analyzed using model-free parameters and a dual-input single compartment model. Perfusion parameters obtained with the two conversion methods were compared using paired Wilcoxon test. Test-retest and interobserver reproducibility of perfusion parameters were assessed in six patients. RESULTS: There were significant differences between the two conversion methods for the following parameters: AUC60 (area under the curve at 60 s, P < 0.001), peak gadolinium concentration (Cpeak, P < 0.001), upslope (P < 0.001), Fp (portal flow, P = 0.04), total hepatic flow (Ft, P = 0.007), and MTT (mean transit time, P < 0.001). Our preliminary results showed acceptable to good reproducibility for all model-free parameters for both methods (mean coefficient of variation [CV] range, 11.87-23.7%), except for upslope (CV = 37%). Among modeled parameters, DV (distribution volume) had CV <22% with both methods, PV and MTT showed CV <21% and <29% using SPGR equations, respectively. Other modeled parameters had CV >30% with both methods. CONCLUSION: Linearity assumption is acceptable for quantification of model-free hepatic perfusion parameters while the use of SPGR equations and T1 mapping may be recommended for the quantification of modeled hepatic perfusion parameters.

The relationship between oxygen and adenosine in astrocytic cultures.

Brain tissue oxygenation affects cerebral function and blood flow (CBF). Adenosine (Ado), a purine nucleoside, moderates neuronal activity, and arterial diameter. The cellular source of Ado in brain remains elusive; however, astrocytes are a logical site of production. Using astrocytic cultures, we tested the hypothesis that astrocytic derived Ado reflects cerebral oxygenation. We found that during alterations in pO(2), extracellular levels of Ado [Ado](e) changed rapidly. Graded reductions of oxygen tension revealed that[Ado](e) reached 10(-7) M to 10(-6) M with a pO(2) of 30-10mmHg, comparable with [Ado](e) and oxygen levels found in brain tissue during normoxemia. Higher O(2) levels were associated with a depression of [Ado](e). Under conditions of low pO(2) (pO(2)

Role of adenosine A2 receptors in regulation of cerebral blood flow during induced hypotension.

The mechanisms responsible for vascular autoregulation in the brain during changes in mean arterial blood pressure are ambiguous. Potentially, adenosine, a purine nucleoside and potent vasodilator, may be involved as earlier studies have documented an increase in brain adenosine concentrations with cerebral ischemia and hypotension. Consequently, we tested the hypothesis that adenosine is involved in vasodilatation during hypotension within the autoregulatory range (>50 mm Hg) by exposing adenosine 2a receptor (A2aR) knockout and wild type (WT) mice to short (2 to 5 mins) periods of hypotension. We found that autoregulation was significantly (P<0.05) impaired by 29% in A2a knockout mice as compared with WT animals. Furthermore, the A2R antagonist (A2a>A2b:10-85>1), ZM-241385, in a dose (1, 5, 10 mg/kg, intraperitoneally)-related manner, attenuated autoregulation in WT mice. In knockout mice treated with ZM-2413585 (5 and 10 mg/kg), autoregulation was further impaired indicating that A2b receptors also participated in cerebral vasodilatation. Treatment with dipyridamole (1.0 mg/kg) that increases extracellular concentrations of adenosine improved autoregulation in the A2aR knockout mice. We would conclude that adenosine through both A2a and A2b receptors is involved in physiologic vascular regulation during hypotension even within the autoregulatory range.

Regulation of cerebral vasculature in normal and ischemic brain.

We outline the mechanisms currently thought to be responsible for controlling cerebral blood flow (CBF) in the physiologic state and during ischemia, focusing on the arterial pial and penetrating microcirculation. Initially, we categorize the cerebral circulation and then review the vascular anatomy. We draw attention to a number of unique features of the cerebral vasculature, which are relevant to the microcirculatory response during ischemia: arterial histology, species differences, collateral flow, the venous drainage, the blood-brain barrier, astrocytes and vascular nerves. The physiology of the arterial microcirculation is then assessed. Lastly, we review the changes during ischemia which impact on the microcirculation. Further understanding of the normal cerebrovascular anatomy and physiology as well as the pathophysiology of ischemia will allow the rational development of a pharmacologic therapy for human stroke and brain injury.