A Nonsurgical Approach to Stenosis
Nonsurgical management of vascular access stenosis, aneurysms, and extravasation with the Viabahn Flexible Self-Expanding Stent Graft.
The hemodialysis patient population as a whole is aging and has increasing comorbidities. These factors can make patients poor candidates for surgical repair or revision of vascular access. Surgical management of access-related venous stenoses and occlusions can also be costly and likely to cause complications. Recently, acceptable alternatives to surgical revision have been developed, such as percutaneous transluminal angioplasty (PTA) followed by endovascular placement of a flexible stent or stent graft.1-4 Effective alternatives to surgical revision can allow uninterrupted vascular access until the patient's condition stabilizes and surgical options are feasible.
Nonsurgical approaches do not necessarily decrease the incidence of repeat stenoses, but they can prolong patency intervals and increase the ease of repeated interventions.1 Conversely, surgical methods consume a current or future access site.2 Nonsurgical management of access strictures, aneurysms, and extravasations can be facilitated by the use of devices such as the Viabahn Endoprosthesis (W.L. Gore & Associates, Inc., Flagstaff, AZ), a flexible, self-expanding stent graft consisting of an external nitinol stent with an expanded polytetrafluoroethylene (ePTFE) lining on the luminal surface. Stent placement has also been used to treat angioplasty-related venous anastomotic rupture,3,4 and Viabahn stent grafts have also been used to successfully treat diffuse aortoiliac occlusive disease.5 This article describes our clinical experience using the Viabahn Stent Graft for nonsurgical treatment of vascular access complications.
Using stent grafts, we have successfully maintained patency of the existing vascular access and managed access complications without surgery in 20 high-risk patients with diabetes and hypertension who either were not suitable candidates for surgery or who had declined surgery. The access complications included outflow strictures associated with arteriovenous ePTFE grafts, arteriovenous fistula aneurysms, graft pseudoaneurysms, and extravasation. Nonsurgical treatment consisted of performing PTA followed by placement of the Viabahn Endoprosthesis Stent Graft. The stent grafts were always placed in the area of outflow stenosis or in an area of the fistula or graft that would not be cannulated for access in the future. The Viabahn stent graft offers the flexibility necessary for placement in areas with a tortuous path or repeated movement, such as across the elbow joint. Also, it is available in lengths up to 15 cm, enabling repair of long areas of stricture.
One graft patient had high-grade strictures in the region of the elbow joint, which was managed with angioplasty followed by placement of a 7-mm X 5-cm stent graft (Figure 1). A very long stricture was identified in the venous outflow tract in another graft patient, which was successfully treated with a 6-mm X 15-cm stent graft (Figure 2). A patient with a transposed basilic vein fistula had a massive aneurysm of the fistula at a previous needle cannulation site, which was treated by placing a stent graft to repair the area of aneurysm (Figure 3). Another patient had a high-grade stricture and multilocular pseudoaneurysms involving the arteriovenous graft; this patient was treated with angioplasty and stent graft placement in an area of the graft that could be avoided for future cannulations (Figure 4). The Viabahn stent graft is not suitable for penetration with a dialysis needle, and care should be taken to avoid the stent graft area when cannulating; therefore, it is important to document the placement and location of the stent graft and place a marker (eg, transcutaneous clip) indicating the “no-stick” zone occupied by the stent graft.
Placement of the stent graft was given careful consideration to avoid interference with future surgical procedures. The length and diameter of the occluded area were measured by angiography to determine the proper size of the endoprosthesis, measuring the proximal and distal diameters of the lumen of the native vessel as well as the length of the lesion and the lumen diameter at the level of the lesion. Balloon dilatation was used to dilate the lesion.
The diameter of the stent should be oversized relative to the diameter of the vessel per the manufacturer's instructions. The manufacturer supplies a sizing table that lists the appropriate device diameter and length for various vessel and lesion sizes. The device should extend at least 1 cm beyond both edges of the lesion.
PTA was performed on the affected segment prior to placement of the stent graft. The Viabahn stent graft is compressed and attached to a dual-lumen, polyethylene delivery catheter. The larger central catheter lumen is used for flushing and guidewire introduction. The smaller lumen contains the deployment mechanism. The delivery catheter is attached to a three-port hub assembly—the central port was used for guidewire introduction, the second port was used for flushing, and the third port was used for the deployment system. The stent graft was advanced over the guidewire and positioned across the affected area using fluoroscopy, to cover the entire segment treated with balloon angioplasty. The delivery catheter shaft was attached to the introducer and held in a straight and stable position with help from an assistant. The endoprosthesis was then deployed by smoothly pulling the deployment knob away from the hub adapter using a continuous pulling motion. After deployment, the device was seated against the vessel wall using an angioplasty balloon of the appropriate size and dilating it along the entire length of the endoprosthesis using minimal pressure. Care was taken to avoid inflating the balloon beyond the endoprosthesis, which could injure the luminal surface of the native vessel. Placement was verified by fluoroscopy.
The Viabahn Endoprosthesis is a very flexible stent graft that can be used to treat access aneurysms, pseudoaneurysms, extravasations, and high-grade strictures, even those across joints and angulations. It is available in lengths up to 15 cm, which allow it to be used in patients with very long strictures. Ideally, stent grafts should be flexible enough for use in tortuous vessels, long enough to cover the entire lesion, and self-expanding to ensure optimal fit in vessels that may experience progressive enlargement of the lumen.1
In contrast, rigid balloon-expandable stents require a relatively straight delivery path and are not well suited for use in tortuous vessels. Rigid balloon-expandable stents also do not conform as well to the vessel configuration as flexible stent grafts; they may cause intimal damage and stenosis at the stent edges due to irritation from vessel motion or anatomic distortion.6 Unlike noncovered metal endoprostheses,7 the Viabahn stent-graft will not undergo foreshortening.
The inside surface of the Viabahn stent graft—the surface that is exposed to the patient's blood—is nonreactive ePTFE. Noncovered metal endoprostheses have been used for the last 15 years, with mixed results.7-13 To reduce the occurrence of neointimal hyperplasia, which is the major cause of restenosis after stent placement,11 Dacron-covered stents were developed and utilized with some success.14 This was followed by development of the ePTFE-lined Viabahn stent graft, which shows promise in reducing neointimal hyperplasia.15
Proper placement of a stent graft can prolong the useful life of an access site, allows for ease of repeated interventions, and does not interfere with potential future surgeries.1,16 The procedure is relatively quick—requiring no more than 15 minutes—and is not technically difficult. The deployment mechanism permits very precise placement of the stent graft. Use of a stent graft is not a definitive procedure, but rather can be considered a temporary solution, allowing continued use of the existing access and postponing definitive surgical revision. Stent placement has been shown to help preserve vascular access for a substantial length of time; however, repeated interventions are frequently necessary to maintain access patency.1,7,17,18 Care must be taken to avoid puncturing the stent during dialysis, which can cause stent distortion and fracture.19
The Viabahn Endoprosthesis is available in lengths up to 15 cm and facilitates management of strictures, including long strictures and those that cross a joint, and fistula aneurysms or graft pseudoaneurysms (even large and multilocular ones). Use of the Viabahn stent graft offers an easy and quick way to manage stenotic access complications, particularly in patients who are not good surgical candidates, and it does not interfere with future surgical procedures. This device represents a significant advance in the management of access complications in hemodialysis patients.
John R. Ross, MD, is Chief of Surgery, Bamberg County Hospital, Bamberg, South Carolina. He holds no financial interest in any product or company mentioned herein. Dr. Ross may be reached at (803) 245-4435; JRRsurgery@aol.com.
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