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The Immature AVF: Inappropriate Behavior and How it can be Modified (The Blame Game)

In an effort to reach the target for fistula creation of 65% by 2009, the National Kidney Foundation Kidney Disease Outcomes Quality Initiative (KDOQI) Clinical Practice Guidelines: Vascular Access 2006 Updates emphasize the need to reduce the primary failure rate of fistulae. (1) Recent data have demonstrated that a majority of fistulae that fail to mature can be salvaged by percutaneous intervention. (2-12). An immature fistula is defined as a fistula that has not developed to the point where it has adequate blood flow or size to allow for repetitive cannulation with 15G or 16G dialysis needles to support dialysis or a fistula that fails within the first three months of usage. (7) Early recognition and timely intervention can assist in salvage of these fistulae. Inappropriate Behavior of the Monitoring Physician – Failure to Identify Fistula Non-maturation The physician responsible for monitoring the newly created fistula, whether a surgeon, nephrologist, interventionalist, or other health care professional must maintain an aggressive approach to monitoring a newly created fistula so that non-maturation may be detected early. The KDOQI Guideline 3.2.4 states that if a fistula fails to mature by 6 weeks, a fistulogram or other imaging study should be obtained to determine the cause of the problem (1). The National Vascular Access Improvement Initiative, Fistula First recommends that a post-operative physical examination be conducted four weeks after fistula creation to detect early signs of failure and refer for diagnostic study and intervention as needed (13). The physical examination is an easy, reliable and inexpensive monitoring method. In a poorly maturing fistula multiple venous outflow veins, accessory veins, or poorly defined cannulation areas may be seen. A discontinuous, high pitched bruit heard only in systole may be present. A pulse (water hammer) with no or a minimal thrill indicates an underlying stenosis. If a thrill is barely palpable across the fistula an inflow lesion must be considered. A swing point stenosis may be considered when a thrill is palpated at the narrowed swing point segment with concomitant non-maturation of outflow vein (1, 14). If necessary, a diagnostic Doppler ultrasound may be performed to quantify the flow, assess venous diameter and to identify any stenoses. A venous diameter >4mm and flow volume >500mL/min increases the predictive power of fistula maturation and adequacy for dialysis to 95%. (15) In addition, diagnostic Doppler ultrasound may be a preferred diagnostic method because it avoids diagnostic cannulation of the newly created fistula and thereby avoids iatrogenic damage of the thin wall of the newly arterialized vein (1). Fistulae that are going to mature will do so within the first 2-4 weeks. Therefore, evaluation should be conducted 4-6 weeks after creation so that once early fistula failure is recognized prompt correction may be undertaken (7, 14). Inappropriate Behavior of the Patient – Failure to Exercise The KDOQI Guideline 3.2.3 states that fistula hand-arm exercise should be performed to mature the fistula (1). Strengthening the forearm by using isometric exercises to increase handgrip strength may increase blood flow, thereby enhance vein maturation, (16) and has been shown to increase forearm vessel size (17, 18). Muscle mass increase from exercise may also enhance vein prominence and decrease superficial fat (1). It is therefore essential to emphasize the importance of exercise to the patient. Inappropriate Behavior of the Fistula – Blame the Arteries and Veins Causes of early fistula failure are frequently due to anatomic lesions anywhere within the access circuit. Arterial inflow lesions include anatomically small vessels and atherosclerotic disease/arterial stenoses. Arterial anastomotic and venous swing point stenoses are commonly seen acquired le-