Ischemic steal syndrome following arm arteriovenous fistula for hemodialysis

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1 Ischemic steal syndrome following arm arteriovenous fistula for hemodialysis Payman Zamani Cardiovascular Division, Veterans Affairs Boston Healthcare System and Cardiovascular Division, Brigham and Women s Hospital and Harvard Medical School, James Kaufman Renal Division, Veterans Affairs Boston Healthcare System and Boston University School of Medicine and Scott Kinlay Cardiovascular Division, Veterans Affairs Boston Healthcare System and Cardiovascular Division, Brigham and Women s Hospital and Harvard Medical School Abstract: Arteriovenous fistulae in the arm are commonly used for hemodialysis in end-stage renal disease. Although physiological steal with reverse flow in the artery distal to the fistula is common, hand ischemia or infarction are rare. The ischemic steal syndrome (hand or forearm ischemia) is usually a result of arterial disease proximal or distal to the fistula and/or poor collateral supply to the hand. The diagnosis is primarily clinical; however, markedly reduced digital pressures and pulse volume recordings support the diagnosis. Management requires imaging for focal stenoses or disease in arteries proximal and distal to the fistula from the aorta to the hand. We present a case caused by subclavian artery occlusion that was initially missed due to focusing investigation only on the fistula. We describe the percutaneous treatments and surgical revisions that attempt to restore flow to the hand without compromising the fistula. Keywords: angioplasty, fistula, gangrene, ischemia, peripheral vascular diseases, subclavian artery, vascular fistula Introduction Arteriovenous fistulae in the arm are the preferred access for hemodialysis in end-stage renal disease. The most common complication of fistula is thrombosis. More rarely, hand ischemia or digital infarction occurs due to poor distal blood flow. All fistulae shunt blood away from the distal arm, and physiological steal (reversed flow in the artery distal to the arteriovenous fistulae) can occur in 70% of radiocephalic fistulae and 90% of brachial artery fistulae. 1 However, symptoms of hand ischemia (pain, parasthesia, or gangrene) only occur in 1 2% of radiocephalic fistulae and 5 10% of brachial artery fistulae. 2 9 The following case highlights the approach and pitfalls to managing the ischemic steal syndrome associated with a fistula in the arm. Corresponding author: Scott Kinlay, Director, Cardiac Catheterization Laboratory and Vascular Medicine, Cardiovascular Division, VA Boston Healthcare System, 1400 VFW Parkway, West Roxbury, MA 02132, USA. scott.kinlay@va.gov Dr Robert Eberhardt was the Guest Editor for this manuscript. Case An 88-year-old man was admitted to the Boston VA with a 5-month history of pain in the left arm and hand and a 2-month history of progressive dry gangrene on the tips of the second and third fingers of his left hand. He had end-stage renal disease due to long-standing type II diabetes mellitus and hypertension, and received hemodialysis from a left upper arm brachial artery basilic vein transposition fistula created 4 years earlier. He had an extensive history of atherosclerotic peripheral vascular disease including a right carotid endarterectomy 11 years earlier, a right below knee amputation 2 years earlier, and a left above knee amputation 6 months prior to his hand symptoms. At the time of his last amputation he had suboptimal blood flow rates with the fistula during dialysis, and he had a left fistulogram that showed a moderate stenosis at the arterial-venous anastomosis of his fistula, which was treated by cutting balloon angioplasty. In the following weeks he developed pain in his left hand and fingers during hemodialysis and when moving his wheelchair. He developed a small non-healing ulcer on his left index finger that progressed to gangrene on three digits of the hand. His left arm and hand pain became continuous, and he The Author(s), Reprints and permissions: / X

2 372 P Zamani et al. had absent radial and ulnar pulses. He was evaluated with an arch aortogram that showed a 45 mm occlusion of the left subclavian artery (Figure 1A). His operative risk for a subclavian bypass was considered too high due to his co-morbidities, and it was initially thought an endovascular approach would be unsuccessful due to the long occlusion. After a second opinion, he was offered an endovascular approach using equipment commonly used to cross coronary artery occlusions. In the Cardiac Catheterization Laboratory, the left femoral artery was accessed and a 6-F LIMA guide was used to cannulate the left subclavian stump. The artery was crossed using a g Asahi Miracle guidewire (Abbott Laboratories, Abbott Park, IL, USA) (Figure 1B) and dilated with mm and mm balloons. The guide was exchanged for an 8-F LIMA guide and the lesion stented with 9.0 mm balloon expandable stents dilated to 10 mm (Figure 1C). Angiography from the left subclavian artery distally demonstrated a widely patent brachial artery, fistula, and a patent radial artery to the wrist. Immediately following the procedure, the patient reported resolution of his pain and warmth in his left hand (Figure 1D). He had hemodialysis from his fistula with improved dialysis flow rates ( ml/ min). The gangrene in his fingers remained stable and did not require surgical intervention. Pathophysiology of the ischemic steal syndrome Physiologic steal with reverse flow in the arm artery distal to the fistula is common after the creation of a fistula because of the low vascular resistance of the fistula. 7,10 This can be identified clinically by comparing the blood pressure distal to the fistula to a more proximal blood pressure or one in the contralateral forearm. For example, the systolic pressure index is a comparison of the systolic pressure in the forearm below the fistula using a hand-held Doppler device versus the contra-lateral arm. 7 In most cases, particularly with upper arm fistulae, the index is below 0.8 in the 24 hours after creating the fistula. The index tends to increase in the months after creation of the fistula, most likely due to the development of collateral arteries from the proximal inflow artery that increases blood flow to the hand. 7,10 Although steal is common, symptoms of ischemia are rare and likely prevented by compensatory vasodilation of the distal arm arteries and subsequent increased collateral flow to the forearm and hand Figure 1 (A) Arch aortogram showing proximal occlusion of the left subclavian artery. (B) Selective angiogram showing the occluded subclavian stump with a 0.014" wire crossing the occlusion. (C) Successful stenting of the proximal subclavian artery. (D) Left hand showing digital gangrene with hyperemia after stenting the subclavian artery.

3 Ischemic steal syndrome 373 to maintain adequate perfusion. 10 Hand ischemia may occur during hemodialysis because dialysis tends to lower venous return, reducing cardiac output and lowering the perfusion pressure in the fistula outflow artery and collaterals that supply the hand. 10 Pathological steal with continuous ischemic symptoms can occur because of proximal inflow disease, reduced collateral flow to the hand, or distal outflow obstruction. 11,12 These all disturb the normal compensatory mechanisms (peripheral vasodilation and increased collateral flow) to preserve perfusion to the distal arm. Any vascular disease that affects the proximal or distal arteries (e.g. atherosclerosis, vasculitis, Buerger s disease) can reduce flow to cause symptoms. Proximal inflow disease can occur in 20 30% of patients with ischemia of the hand, 2,8 as illustrated by our case of subclavian artery occlusion. Although end-stage renal disease is associated with many atherosclerosis risk factors, the risk factors for ischemic steal syndrome include diabetes mellitus, peripheral artery disease, age greater than 60 years, women, upper arm versus lower arm fistulae, multiple operations in the same limb, and the use of PTFE grafts. 3,4,8,13,14 These factors presumably relate to increased or more diffuse arteriosclerosis of the arteries in the forearm and hand, and poor development of collaterals. Assessment Diagnosis of the ischemic steal syndrome Since physiological steal is common, ischemic steal syndrome is primarily a clinical diagnosis. Signs include pallor, diminished or absent peripheral pulses in the arm or hand, sensory or motor neuropathy, and distal infarction or ulceration. The occurrence of ischemic steal has been divided into early (less than 30 days after fistula creation) or late (30 or more days) presentations. 7,14 Severe presentations of critical limb ischemia with motor dysfunction immediately after fistula creation usually need urgent revision, revascularization, or ligation. Milder symptoms may resolve spontaneously, likely due to the development of collaterals to the hand, whereas later presentations are usually progressive. 7,10 Several non-invasive physiological techniques can assess pressure and flow distal to the fistula to quantify the extent of steal. These techniques may identify those at risk of developing the syndrome or provide supportive evidence for the diagnosis in the presence of clinical findings. Physiological measures of distal limb perfusion include digital plethysmography and pulse volume recordings, the digital pressure index (ratio of digital to brachial pressure), and the systolic pressure index (ratio of the fistula forearm to contralateral forearm pressure). Digital pulse volume recordings in most asymptomatic patients with healthy fistula show a phasic waveform that is augmented by occluding the venous limb of the fistula. 10 However, in the ischemic fistula syndrome, digital systolic pressures are usually less than 50 mmhg and the resting digital pulse volume recordings are flat but return to a pulsatile waveform after occlusion of the venous limb. 10 A systolic pressure index of less than 0.57 is more commonly found in patients with ischemic steal syndrome. In one study, abnormal nerve conduction studies were more common with progressively lower systolic pressure indexes supporting ischemia as a cause of some neuropathic symptoms. 7 In another study, a digital to brachial artery pressure less than 0.6 had the best test characteristics for the ischemic steal syndrome. 5 However, in most reports, there is considerable overlap in these physiological tests between symptomatic and asymptomatic patients, 5,7 thus these tests need to be interpreted in the appropriate clinical setting. Neuropathies in the differential diagnosis Severe neuropathic syndromes occurring shortly after fistula creation require urgent attention. Ischemic monomelic neuropathy is a rare cause of sensory-motor impairment of the forearm without tissue necrosis. The initial case reports consisted of sudden and permanent sensory and motor impairment involving multiple nerve groups of a distal limb and were associated with nerve conduction studies showing axonal loss and reduced conduction velocities Cases occurring immediately after fistula creation were thought to be due to a transient reduction in blood flow that caused ischemia of the vasa nervorum, but was not prolonged enough to cause tissue loss. 7,15,17 19 It is most commonly associated with diabetes, atherosclerotic vascular disease, and upper arm fistulae. Immediate revascularization or ligation of the fistula is required for this acute presentation, but may not prevent permanent nerve damage. 15,17 Involvement of all of the distal nerves of the forearm (radial, ulnar and median nerves) with decreased nerve conduction studies and axonal loss distinguish ischemic monomelic neuropathy from focal nerve injuries such as hematoma, abscess, or venous aneurysm that tend to affect only one nerve. 19,20 Carpal tunnel syndrome tends to be more common in the fistula arm than the contralateral arm, but is distinguished by an abnormal nerve conduction study affecting primarily the median nerve. 21 A more indolent and less severe form of ischemic monomelic neuropathy may occur, and one group suggests that the diagnosis may be more likely with a progressive decline in serial nerve conduction

4 374 P Zamani et al. studies over several months associated with a reduced systolic pressure index (< 0.5). 7 In this setting, revascularization may improve the neurological symptoms. 7 Tests to localize the cause of steal Non-invasive and invasive testing has an important role in determining any potentially reversible causes of the ischemic steal syndrome. Imaging with ultrasound or arteriography (conventional, computed tomography, or magnetic resonance techniques) can assess proximal inflow and outflow disease in addition to fistula flow rates. 10 Duplex ultrasound can assess whether there is any fistula inflow or outflow disease. Functional fistulae usually have flow rates of greater than 600 ml/min, 10 and fistulae with flow rates of < 250 ml/min are more likely to thrombose. Since flow rates are exaggerated and often non-laminar in the inflow artery, manual occlusion of the venous limb of the fistula is usually required to see the typical post-stenotic blunted or monophasic flow velocity, suggesting a proximal arterial stenosis. 18 Increased flow velocities or absent flow in the distal arteries of the forearm suggest intrinsic disease distal to the fistula as a cause of ischemic steal syndrome. Marked reverse flow in the radial artery distal to the fistula may cause ischemia. Demonstration of a patent ulnar artery and palmar arch is required prior to considering embolization or ligation of the radial artery distal to the fistula to prevent hand steal. Indications for revascularization The indications for revascularization are: 1) any proximal inflow disease with poor fistula flow 2) rest pain, muscle weakness, or necrosis in the hand 5,7,8,18,19 3) ischemic monomelic neuropathy 7,18,19 Treatment of disease proximal or distal to the fistula Proximal artery disease can be treated by percutaneous methods, as in our case, or by surgical revascularization. Percutaneous methods for proximal disease offer less morbidity, and as many patients with ischemic steal syndrome have co-existing atherosclerotic vascular disease, probably less mortality than surgery. 22 Flow-limiting disease distal to the fistula can be treated by angioplasty, 11 or by surgical bypass that may be part of a surgical revision of the fistula. Severe hand steal from a radiocephalic fistula due to reverse flow in the more distal radial artery can be treated by percutaneous radial artery embolization 12 or ligation (distal radial artery ligation, DRAL), 18,23 providing there is antegrade flow in the ulnar artery and an adequate palmar arch. Methods to modify the fistula Surgical revision of the fistula improves distal blood flow by redirecting flow from the fistula to the hand or by improving collateral flow to the hand. Techniques that reduce the diameter of fistula and/or lengthen the fistula increase resistance and decrease flow in the fistula according to Poiseuille s law. 2,13 The DRIL procedure (see below) increases distal flow by creating a low resistance collateral circuit to the distal hand. 10 Fistula banding Fistula banding or plication aims to increase the resistance of the fistula to divert flow down the native artery (Figure 2). However, this reduces flow in the fistula and threatens its survival. As a result, many reports of banding show high rates of fistula thrombosis. 4,8 Intraoperative pressure or flow monitoring may improve the success of the procedure while preserving fistula flow. In one series, distal artery flow was monitored by digital plethysmography to achieve a digital pressure of greater than 50 mmhg and a digital to brachial pressure index greater than This approach relieved steal symptoms in all 16 patients, but only 10 (63%) had satisfactory graft function for more than 6 months. 9 Another approach is to monitor the flow reduction in the venous limb of the fistula to prevent severe flow reductions that would promote fistula thrombosis. 24 In a series of 78 patients with ischemic steal syndrome and high fistula flow, banding was tailored to reduce fistula flow to 400 ml/min in autogenous grafts, and 600 ml/min in prosthetic grafts. Ischemic symptoms were relieved in 86% of patients with 91% of autogenous fistulae remaining patent at 12 months. 24 Graft survival with banding was less successful with prosthetic grafts (only 58% patent at 1 year) and the authors suggested that higher flow rates (> 750 ml/min) in the graft were required to prevent thrombosis. 24 More recently, the minimally invasive limited ligation endoluminal-assisted revision (MILLER) technique describes a modified method of banding. 25 In this procedure, the fistula is exposed and a 4 5 mm balloon is introduced into the fistula and inflated. A non-resorbable suture is tied around the inflated balloon and vein to achieve a defined reduction in balloon diameter. In the original report of 16 patients, all had improvement in symptoms, two required further revision of their fistulae and

5 Ischemic steal syndrome 375 Figure 2 Diagrams illustrating several methods to reduce distal artery steal by the arterial venous fistula. (DRIL, distal revascularization, interval ligation; RUDI, revision using distal inflow; PAI, proximal arterial inflow graft.) all were patent at a mean of 3 months of follow-up. 25 Distal revascularization, interval ligation (DRIL) In this procedure, the artery distal to the fistula is ligated to prevent reversal of flow in the distal artery, and a bypass graft is placed from the brachial artery well above the fistula to the antecubital or forearm artery distal to the ligation (DRIL) (Figure 2). 26 The DRIL procedure effectively acts as a low-resistance collateral artery to the distal arm 10 and improves symptoms in over 90% of patients, while preserving the fistula in % of cases. 2,14,18,27,28 The potential disadvantages of DRIL are that the distal arm is dependent on a graft for blood supply because the native artery is ligated, and that distal anastomoses are technically more difficult in patients with diffuse disease in the distal forearm arteries. Revision using distal inflow (RUDI) The RUDI is designed to treat ischemic steal syndrome with a brachial artery fistula. In contrast to ligating the native artery, RUDI ligates the fistula at its origin and creates a bypass to the fistula from one of the more distal forearm arteries (Figure 2). 13 The other forearm artery (not used as the graft source) must be patent to prevent recurrence of a steal syndrome. RUDI tends to reduce flow in the fistula and long-term patency and flow rates in large series have not been reported. Proximal arterial inflow (PAI)/proximal arteriovenous anastomosis (PAVA) The PAI or PAVA procedure moves the origin of the fistula more proximally in the arm. 29 The fistula is ligated at its origin and a PTFE graft is run from the more proximal brachial or axillary artery to the fistula (Figure 2). By moving the graft feeder more proximally to a larger artery, relative flow into the native artery and collaterals is increased without compromising fistula flow volumes. 29 In one case series of 30 patients, 84% were free of ischemic symptoms and 87%ofthefistulaewerepatentat12months. 29 Ligation of the fistula When other treatment options fail or extensive vascular calcification prevents revascularization or fistula modification, ligation of the fistula can resolve the ischemic symptoms, but with the need to create another vascular access. Conclusions Ischemic steal syndrome causing symptoms after arm fistula creation are rare but challenging to manage. In our case example, decreased flow in the fistula was initially thought to be due to a fistula stenosis. Although angioplasty improved fistula flow, it exacerbated steal to cause hand ischemia and ultimately digital infarction. This prompted investigation of vascular causes of insufficiency beyond the fistula. Although the diagnosis of ischemic steal syndrome is principally clinical, abnormal digital pressures or pulse volume recordings support the diagnosis by quantifying the severity of vascular steal. The diagnosis can be distinguished from neuropathic pain by nerve conduction studies. Abnormal nerve conduction studies in all three distal nerves of the forearm are more characteristic of ischemic monomelic neuropathy. The cause of the ischemic steal syndrome should be directed at localizing disease from the aorta to the hand. Duplex ultrasound and arteriography should aim to interrogate the arteries proximal and distal to the fistula in addition to fistula flow.

6 376 P Zamani et al. Our case illustrates the pitfalls of focusing only on the fistula as a cause of reduced fistula flow, as a more severe proximal lesion was not considered in the initial workup. In our case, subsequent recognition of the subclavian artery occlusion led to successful angioplasty and stenting borrowing techniques familiar to those employed in crossing coronary artery occlusions. In the absence of proximal or distal disease, several surgical techniques to modify the fistula or collateral flow to the hand can successfully treat the ischemic steal syndrome while preserving the fistula. References 1 Anderson CB, Etheredge EE, Harter HR, Codd JE, Graff RJ, Newton WT. Blood flow measurements in arteriovenous dialysis fistulas. Surgery 1977; 81: Berman SS, Gentile AT, Glickman MH, et al. Distal revascularization-interval ligation for limb salvage and maintenance of dialysis access in ischemic steal syndrome. 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