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Dialysis Clinic: Dysfunction of New Catheters by Old Fibrin Sheaths

A common cause of autogenous arteriovenous fistula (AVF) failure is the presence of stenosis at sites of surgical vein mobilization (1–4), called “swing point” stenosis (1) (Table 1). Anastomotic swing point stenosis occurs within a few centimeters beyond the surgical connection in the vein used to create the AVF. In published AVF failure series, this lesion is more common in forearm AVFs (64–77%) (1–3) than in upper arm AVFs (39– 56%) (1,3). In addition, AVFs that require superficialization of the basilic vein are subject to transposition swing point stenosis, a finding in 60% of failing brachiobasilic AVFs in one series (1). The pathophysiology of swing point stenosis is unknown. Hypotheses include technical surgical problems (axial rotation, kinking, or vein adventitial bands), secondary changes in the vein related to extensive dissection, as well as devascularization, and intimal hyperplasia associated with increased turbulence and shear stress following AVF creation (1). The initial diagnosis of swing point stenosis is based on clinical findings. The normal examination should reveal a soft and pliable AVF with a brisk continuous thrill at the anastomosis that diminishes gradually traveling up the fistula away from the anastomosis (5). An anastomotic swing point stenosis appears as a firm or hard AVF with a “water hammer” pulse at the surgical connection, including an absent diastolic component (5). Moving downstream along the fistula (away from the anastomosis), past the stenotic lesion, the pulse diminishes abruptly or disappears. An important sign of anastomotic swing point lesions in an AVF supporting dialysis is high negative “arterial” (prepump) pressures, since the narrowing is generally upstream from the AVF “arterial” needle. Such high negative pressures can cause a significant reduction in actual delivered blood flow, thereby compromising the adequacy of dialysis. Swing point stenosis can also present with AVF thrombosis (3). Fistulogram is the optimal technique to confirm this lesion, allowing for subsequent percutaneous angioplasty (PTA) of the stenosis. Several investigators employ PTA as the first-line therapy (1,3,4). One-year mean primary patency rates of 50% for forearm AVFs and 34% for upper arm AVFs were reported in one series (3); secondary patency rates of 80–86% were found for all AVF. Alternatively, one group advocates a new surgical anastomosis just proximal to the pathologic area (2). When PTA fails, surgical revision is uniformly recommended.