Pilot Study of Cryoplasty with Use of PolarCath Peripheral Balloon Catheter System for Dialysis Access

Artery to vein configuration of arteriovenous fistula improves hemodynamics to increase maturation and patency

Arteriovenous fistulae (AVF) are the preferred mode of hemodialysis access, but 60% of conventional [vein-to-artery (V-A)] AVF fail to mature, and only 50% remain patent at 1 year. We previously showed improved maturation and patency in a pilot study of the radial artery deviation and reimplantation (RADAR) technique that uses an artery-to-vein (A-V) configuration. Here, we show that RADAR exhibits higher rates of maturation, as well as increased primary and secondary long-term patencies. RADAR is also protective in female patients, where it is associated with decreased reintervention rates and improved secondary patency. RADAR and conventional geometries were compared further in a rat bilateral carotid artery-internal jugular vein fistula model. There was decreased cell proliferation and neointimal hyperplasia in the A-V configuration in male and female animals, but no difference in hypoxia between the A-V and V-A configurations. Similar trends were seen in uremic male rats. The A-V configuration also associated with increased peak systolic velocity and expression of Kruppel-like factor 2 and phosphorylated endothelial nitric oxide synthase, consistent with improved hemodynamics. Computed tomography and ultrasound-informed computational modeling showed different hemodynamics in the A-V and V-A configurations, and improving the hemodynamics in the V-A configuration was protective against neointimal hyperplasia. These findings collectively demonstrate that RADAR is a durable surgical option for patients requiring radial-cephalic AVF for hemodialysis access.

Future research directions to improve fistula maturation and reduce access failure

With the increasing prevalence of end-stage renal disease, there is a growing need for hemodialysis. Arteriovenous fistulae (AVF) are the preferred type of vascular access for hemodialysis, but maturation and failure continue to present significant barriers to successful fistula use. AVF maturation integrates outward remodeling with vessel wall thickening in response to drastic hemodynamic changes in the setting of uremia, systemic inflammation, oxidative stress, and pre-existent vascular pathology. AVF can fail due to both failure to mature adequately to support hemodialysis and development of neointimal hyperplasia that narrows the AVF lumen, typically near the fistula anastomosis. Failure due to neointimal hyperplasia involves vascular cell activation and migration and extracellular matrix remodeling with complex interactions of growth factors, adhesion molecules, inflammatory mediators, and chemokines, all of which result in maladaptive remodeling. Different strategies have been proposed to prevent and treat AVF failure based on current understanding of the modes and pathology of access failure; these approaches range from appropriate patient selection and use of alternative surgical strategies for fistula creation, to the use of novel interventional techniques or drugs to treat failing fistulae. Effective treatments to prevent or treat AVF failure require a multidisciplinary approach involving nephrologists, vascular surgeons, and interventional radiologists, careful patient selection, and the use of tailored systemic or localized interventions to improve patient-specific outcomes. This review provides contemporary information on the underlying mechanisms of AVF maturation and failure and discusses the broad spectrum of options that can be tailored for specific therapy.

Balloon angioplasty for low-flow access

The common mechanism for low access flow is intimal hyperplasia leading to stenosis within the access circuit. Balloon angioplasty (percutaneous transluminal angioplasty, PTA) remains the mainstay of treatment despite multiple technologies introduced in the past. New technologies continue to be introduced in an effort to improve on outcomes of angioplasty. This article briefly reviews the use of and outcomes of PTA, technologies, past, present and future as well as some of the questions that remain unanswered with PTA.

Paclitaxel-coated versus plain balloon angioplasty for dysfunctional arteriovenous fistulae: one-year results of a prospective randomized controlled trial

PURPOSE

To report 1-year results of a single-center randomized controlled trial comparing paclitaxel-coated balloon (PCB) versus high-pressure plain balloon angioplasty for the treatment of failing arteriovenous fistulae (AVFs).

MATERIALS AND METHODS

Forty patients (26 men; mean age, 61 y ± 14.63) were randomized at 1:1 to undergo PCB (n = 20) or high-pressure balloon (HPB; n = 20) angioplasty of dysfunctional AVFs. There were no significant differences in baseline demographics between groups. Enrollment required a clinical diagnosis of a dysfunctional AVF attributed to a single stenotic lesion verified with digital subtraction angiography. Primary endpoints included device success, anatomic success, clinical success, and target lesion revascularization (TLR)-free survival. Secondary endpoints included dialysis circuit primary patency and procedure-related complication rates.

RESULTS

Device success rates were 100% in the HPB group and 35% in the PCB group (P < 0001): further dilation with an HPB was needed to achieve anatomic success in 13 of 20 cases in the PCB group (65%). Anatomic and clinical success rates were 100% in both groups. TLR-free survival (PCB, 308 d; HPB, 161 d; hazard ratio [HR], 0.478; 95% confidence interval [CI], 0.236-0.966; P = .03) and access circuit primary patency (PCB, 270 d; HPB, 161 d; HR, 0.479; 95% CI, 0.237-0.968; P = .04) were significantly in favor of PCB angioplasty. No minor or major procedure-related complications occurred.

CONCLUSIONS

In this single-center study, the use of PCBs resulted in superior TLR-free survival and dialysis access circuit primary patency of dysfunctional AVFs. However, additional HPB postdilation was required in the majority of cases.

The Eternal Tale of Dialysis Access Vessels and Restenosis: Are Drug-Eluting Balloons the Solution?

In dialysis access fistulas and grafts, percutaneous transluminal angioplasty (PTA) is frequently followed by restenosis development, which results in repeated periodical re-interventions. The technique of drug-eluting balloon (DEB) angioplasty has shown promising results in the treatment of femoropopliteal arteriosclerotic lesions. In contrast to arteriosclerotic arteries, dialysis access vessels host unfavorable hemodynamics due to the direct conduction of high-pressure fluid into a low-pressure system. Hence, the beneficial effect of DEB angioplasty may be limited in this system. However, a first prospective randomized trial on 40 patients with arteriovenous fistula or graft stenoses exhibited a significantly higher 6-month primary patency of the treated lesions after DEB angioplasty than after uncoated balloon angioplasty. Despite such a positive reference, general recommendations regarding the value of DEBs in dialysis access vessels cannot be considered as serious unless large randomized controlled trials have been performed.

Superior Vena Cava Syndrome: Role of the Interventionalist

Superior vena cava syndrome results from the obstruction of blood flow through the superior vena cava and is most often due to thoracic malignancy. However, benign etiologies are on the rise secondary to more frequent use of intravascular devices such as central venous catheters and pacemakers. Although rarely a medical emergency, the symptoms can be alarming, particularly to the patient. Traditionally, superior vena cava syndrome has been managed with radiotherapy and chemotherapy. But interventional endovascular techniques have made inroads that offer a safe, rapid, and durable response. In many cases, it may be the only reasonable treatment. Because of this, an approach to endovascular treatment of this condition must be in the armamentarium of the interventional radiologist. This review will provide the reader with an insight into the etiology, pathophysiology, and various management principles of superior vena cava syndrome. The focus will be on understanding the techniques used during various endovascular interventions, including angioplasty, stenting, and pharmacomechanical thrombolysis. Discussion will also be centred on possible complications and current evidence as well as controversies regarding these approaches.

Peripheral applications of drug-coated balloons: past, present and future

Drug-coated balloon (DCB) technologies represent the latest and hottest development in the field of endovascular treatment of peripheral arterial disease. Initial experience with paclitaxel-coated balloon use in the femoral artery has demonstrated lower mid-term restenosis and superior mid-term clinical outcomes in terms of improved wound healing and reduced repeat angioplasty rates compared with standard balloon angioplasty. Many companies are presently developing and/or improving DCB catheters and therefore ongoing, technical improvements of the already existing platforms, new drugs, and innovative carriers are expected. The ongoing basic research studies and various multicenter randomized, controlled trials that are currently in progress will offer valuable scientific insights regarding the long-term effectiveness and other crucial issues, such as efficacy in various vascular beds, optimal balloon dosage, and post angioplasty antiplatelet therapy. Future applications of these devices also could include in-stent restenosis, anastomotic stenosis of surgical bypass, and benign stenoses of the central venous system. The authors envision that DCB angioplasty will evolve to a major paradigm shift in the endovascular treatment of occlusive vascular diseases.

Relationship between the Outcomes of Stent Placement and the Properties of Arteriovenous Graft Outflow Vein Stenotic Lesions

Purpose

The mechanisms of venous stenosis in vascular access include vascular constriction and neointimal hyperplasia. One purpose of this study was to examine the properties of stenotic lesions in arteriovenous graft outflow veins and the association with the results of treatment using stent placement.

Subjects and Methods.

The study involved 46 patients who underwent stent placement to treat arteriovenous graft outflow vein stenosis. The properties of stenotic lesions before stent placement were observed by ultrasonography and were classified into three groups: vascular constriction types, neointimal proliferation types, and mixed types. Stent placement was performed when elastic recoil occurred or when restenosis occurred at the same site within three months. The primary patency results for each group were then compared. The primary endpoint included patency of the treatment area.

Results.

The primary patency rate of the treatment area at 6, 12, 18 and 24 months post-stent placement for the vascular constriction type was 100.0%, 92.3%, 84.6% and 75.2%, respectively. Those rates were 66.7%, 33.3%, 33.3% and 25.0% for the neointimal proliferation type, and 90.5%, 52.4%, 38.1% and 27.2% with the mixed type. The vascular constriction type displayed excellent primary patency rates after stent placement.

Conclusions.

It is possible to define the types of stenotic lesions for which stent therapy is effective through morphological diagnosis of those lesions using ultrasound tomography.