The peripheral vessels

Interventional procedures in the venous system

 

PTA and stenting of obstruction in arterio-venous fistulae in patients on hemodialysis

Obstruction of venous outflow is by far the most common problem encountered in patients with hemodialysis access fistulae. Most stenoses occur within a few centimetres of the venous anastomoses in Cimino shunts, or in grafts at the site of the proximal anastomosis. In approximately 21 % of all venous outflow lesions, however, the stenoses occur in the brachiocephalic vessels. A stenosis at the arterio-venous anastomosis 

Figure 50. PTA of venous outflow stenosis in hemodialysis shunt. A) Shuntogram with proximal compression shows widely patent AV-anastomoses but multiple stenoses of the venaus outflow tract close to the anastomosis. B) After first dilation suboptimal result. C) Good result after prolonged dilation with high pressure (12 atmos) for 6 and 10 minutes. Prolonged balloon dilatation in venous outflow stenoses often improves dilation results.

is much rarer than venous outflow obstruction. Balloon dilation particularly of venous outflow stenosis and stenosis of graft anastomoses has been used with increasing frequency during the past decade. The route of access to a lesion requiring balloon angioplasty depends on its location, and the exact anatomy of the venous outflow tract including the arterio-venous anastomosis has to be studied before any percutaneous intervention. The approach to the stenotic lesion can be either antegrade or retrograde and is chosen so as to allow sufficient space for the manipulation of guidewires, and angiographic and balloon catheters through the stenosis via a hemostatic sheath. The balloon sizes are generally 5 to 7 mm for veins below the elbow, 7 to 10 mm for those in the upper arm and 10 to 12 mm for the subclavian and brachiocephalic veins. For a stenosis of the arterio-venous anastomosis smaller balloon sizes according to the diameter of the artery may have to be chosen. As with any PTA procedure 5,000 units of Heparin are given after introducing the sheath but nothing further in the way of anticoagulation is usually necessary.

Although patency rates have been somewhat disappointing ranging from 42 to 45% at one year and as low as 12 to 38% at two years, PTA remains the treatment of first choice for failing hemodialysis fistulae (Fig. 50). Repeat dilation of venous outflow obstructions in the native outflow vein, and/or at the arteriovenous or graft anastomoses may be necessary to keep the fistula functioning for hemodialysis.

Figure 51. Patient eight months after placement of a 10 mm Wallstent for tight recurrent stenosis in the basilic vein. A) Recurrent stenosis from intimal hyperplasia at the efferent end of the stent (arrow) and moderate intimal thickening within the stent (arrowheads). B) A second 10 mm Wallstent has been placed overlapping the first one via a femoral approach with good immediate result. Patient died two months later from underlying disease with functioning shunt.

In spite of the higher recurrence rates with PTA, aggressive angiography coupled with angioplasty at the first sign of fistula dysfunction may prolong the life of a fistula for several years. Recently intravascular stents have been tried in an attempt to improve upon the results of PTA alone. In general however, primary stenting without a previous trial of conventional PTA is not recommended since a stent cannot usually prevent later restenosis from intimal hyperplasia. Exceptions to this rule may be cases where PTA has proved ineffective owing to the elastic recoil of the stenosis or where the recanalisation of chronically occluded central veins is required.
As is the case with PT A, access to the lesion depends on the location of the stenosis and for central and proximal peripheral lesions we prefer a femoral approach. We always predilate the stenotic segment before stent implantation and repeat dilation of the stented segment immediately following stent release is also performed if adequate stent expansion seems delayed.

Though the initial technical and clinical success rate after stenting of hemodialysis outflow stenosis is very high, restenosis at some point after stenting (usually between 4 and 12 months) almost invariably occurs. However, restenosis caused by intimal hyperplasia can usually be redilated quite easily by balloon angioplasty. Since patients on chronic hemdialysis are likely to have multiple surgical procedures during their lifetime it is important to perform percutaneous transluminal procedures whenever possible (Fig. 51).

PTA and stenting of benign and malignant obstructions of the vena cava and large veins

There are various causes of obstruction or stenosis of the vena cava and large veins. Those seen most frequently include compression by malignant disease, fibrous reactions after radiation therapy and the sequelae of deep vein thrombosis and from indwelling central venous catheters. Other causes for venous obstructions include trauma, infection, post-surgical complications, venous anomalies such as webs or venous spurs and finally stenoses of the liver veins or the intrahepatic segment of the IVC in Budd-Chiari syndrome. The sites most frequently involved in these conditions are the superior and inferior venae cavae (including the pelvic veins). The operative treatment of stenotic or occlusive venous disease is often difficult and involves major vascular surgery in the case of the venae cavae and other large central veins. In malignant obstruction surgery is not justified in view of the dismal prognosis of the underlying disease. Therefore interventional techniques such as percutaneous transluminal angioplasty and stenting have been recently introduced as both curative and palliative forms of treatment.

Since most obstructions are caused by external compression or fibrotic changes which do not respond well to PTA alone, angioplasty is practically always backed up by an endovascular stent. Inflow obstructions of the superior or inferior vena cava (superior vena cava and inferior vena cava syndrome) are excellent indications for stenting since the majority of the patients will respond by rapid regression of the symptoms of inflow obstruction within hours (Fig. 52). Clinical relief of symptoms can be expected in 70 to 100% of the subjects in malignant disease and in close to 100% in benign obstructions. Long-term patency in SVC and IVC stenting for malignant disease ranges from 86 to 100%, though the length of patient survival rarely lasts more than two years. If acute thrombosis or restenosis occurs a second procedure using local thrombolysis or redilatation and additional stent placement can be performed. Although there is only limited data on long-term patency for benign lesions this will probably be above 90% (Fig. 53).

Figure 52. Patient with severe superior V cava syndrome from mediastinal metastases secondary to carcinoma of the breast A +B) Phlebography of both arms shows tight stenosis of right brachiocephalic vein and occlusion of the left brachiocephalic vein. C) After stenting with a 12 mm Wallstent on the right and guidewire recanalization and stenting with a 10 mm Wallstent on the left there is good drainage. Patient was free of symptoms within hours.

Provided a stenosis or occlusion of the vena cava or a large vein can be passed using a guidewire and a preliminary dilatation of the lesion with a balloon catheter allows enough expansion of the lesion to permit stent implantation, practically any malignant or benign venous obstruction may be stented. It is important, however, to ensure that adequate blood flow will exist through the stented area which means adequate inflow and outflow. Generally a femoral approach is employed for stenting but an internal jugular approach is sometimes necessary. For very tight lesions or chronic occlusions of the brachiocephalic vessels a double approach from the arm and the femoral vein (the so called pull-through method to stabilise the guidewire from both ends) may be necessary. If significant thrombosis distal to the obstruction is found on phlebograhy, local thrombolysis with Urokinase should be performed before stent placement to prevent pulmonary emboli and/or early reocclusion.

PTA and stent implantation for palliation in malignant disease and as curative treatment in benign conditions should be regarded as the method of choice in view of its success compared to surgical alternatives.

Figure 53.Patient with veno-venous bypass for trauma to common femoral vein during operation for varices. Massive right leg swelling two months after corrective surgery. A) Crossover retro grade phlebography shows subtotal stenosis of right common femoral vein. B) After placement of a 10 mm Wallstent the antegrade flow of the femoral vein is re-established.

 

Christoph L. Zollikofer and Frode Laerum