Arteriovenous fistula

Published on 02/04/2015 by admin

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238 Arteriovenous fistula

Instruction

Look at this patient’s arms.

Salient features

History

• History of trauma to the limb

• History of haemodialysis and artificial arteriovenous fistula.

Examination

• Hypertrophy of the affected arm

• Prominent, dilated, tortuous veins

• Continuous thrill over the fistula; listen for continuous bruit

• Collapsing pulse; increased pulse pressure indicating hyperdynamic circulation.

Proceed as follows:

• Look for signs of cardiac failure.

• Elicit Branham’s sign: slowing of the pulse on occluding the feeding vessel of the fistula.

• If the fistula is in the upper limb, then perform Allen’s test: the radial and ulnar arteries are occluded at the wrist and the hand is exercised; the arteries are then released one at a time to establish which is the dominant feeding vessel.

• Look for signs of chronic renal failure.

Note: An arteriovenous fistula is a direct subcutaneous anastomosis of an artery and vein without prosthetic material, and is the preferred means of vascular access for haemodialysis.

Diagnosis

This patient has an arteriovenous fistula (lesion) that has been surgically created (aetiology) for haemodialysis and is functioning well.

Advanced-level questions

How are arteriovenous malformations classified?

Angiographically, as follows:

• Group 1, predominantly arterial or arteriovenous lesions: present with pain, hypertrophy of the digit or limb, deformity, distal ischaemia, venous hypertension; large lesions can cause symptoms and signs of cardiac failure

• Group 2, lesions affecting tiny vessels including capillaries: for example port-wine stain, epistaxis in hereditary haemorrhagic telangiectasia, GI haemorrhage with colonic dysplasia

• Group 3, predominantly venous lesions: local oedema, pain and venous ulceration; there may be a history of trauma.

How would you manage a patient with an arteriovenous malformation?

• Referral to a vascular surgeon

• Doppler ultrasonography

• Angiography.

When and how is an arteriovenous malformation treated?

Arteriovenous malformations are treated when they cause discomfort, disfigurement and danger to the patient. The patient should be jointly assessed by a vascular surgeon and an interventional radiologist for embolization. The temptation to ligate the feeder vessel should be resisted as subsequent embolization may be difficult. Complete exicision of the fistula is accepted treatment in resistant cases.

Why are fistulae preferred to prosthetic grafts?

Fistulae have a far lower risk of failure and a reduced requirement for revision compared with prosthetic grafts. In 2005, the Center for Medicare and Medicaid Services recommended a goal of arteriovenous fistula formation in 66% of all new patients undergoing haemodialysis in the breakthrough initiative that has become known as ‘Fistula First’. Unfortunately, a substantial number of patients lack suitable veins for the creation of autogenous fistulae and require placement of prosthetic grafts.

What the alternatives, when a fistula cannot be formed in patient requiring long-term haemodialysis?

Placement of synthetic grafts subcutaneously or of a long central line into a great vein.

What is the leading cause of failure of a prosthetic arteriovenous haemodialysis-access graft?

The leading cause of failure of a prosthetic arteriovenous haemodialysis-access graft is venous anastomotic stenosis (Fig. 238.1). Balloon angioplasty, the first-line therapy, has a tendency to lead to subsequent recoil and restenosis. Percutaneous revision of venous anastomotic stenosis in patients with a prosthetic haemodialysis graft is improved with the use of an expanded polytetrafluoroethylene endovascular stent graft, which appears to provide longer-term and superior patency and freedom from repeat interventions than standard balloon angioplasty (N Engl J Med 2010;362:494–503).

Fig. 238.1 Older dialysis fistula, showing multiple aneurysms (arrows) from multiple time use.

(With permission from Roberts, Hedges 2009.)

HH Branham, an American surgeon in the nineteenth century.

EV Allen (1900–1961), Professor of Medicine at the Mayo Clinic, Rochester, Minnesota, introduced coumarin anticoagulants into clinical practice and edited one of the first comprehensive textbooks on peripheral vascular disease.

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