RESUMO
BACKGROUND: Vascular access-related complications are an important cause of morbidity, and they account for 14% to 17% of dialysis patients' hospitalizations with an annual cost in the United States of approximately $1 billion. Previous studies have related the major predisposing factor of thrombotic complications to stenosis of the graft anastomosis. Several recent reports suggest that antiphospholipid antibodies may cause frequent thrombotic complications. The broad spectrum of diseases that cause hypercoagulable states has not been correlated with frequent PTFE graft thrombosis. STUDY DESIGN: A retrospective case series study was performed to determine the frequency of hypercoagulable states in dialysis patients who had repeated thrombotic complications of their PTFE grafts. Between May 1996 and June 1998, 91 operations were performed on 34 patients with end-stage renal disease. All arteriovenous fistulas were created with PTFE grafts and placed by a single surgeon. All patients were evaluated at operation for anastomotic stenosis, and the majority of patients were studied for hypercoagulable states. Patients with a documented hypercoagulable state were considered for warfarin therapy. RESULTS: Twenty-two individuals (64.7%) developed 67 thrombotic complications. Twelve of the 14 patients tested (85.7%) were shown to have hypercoagulable states of various causes and degrees. Thirteen patients developed multiple thrombotic complications, 11 (81.8%) were tested and proved to be hypercoagulable. Thirty-eight of the thrombotic complications had nonanatomic causes and 28 (41.8%) had hypercoagulability as the only determinable cause. Ten of the 12 hypercoagulable patients (83.3%) were relegated to intermediate to high-intensity warfarin therapy to reduce the incidence of thrombotic events. Hypercoagulable patients not receiving warfarin had a thrombosis rate of 4.0 events per year; patients on warfarin had a rate of 1.2 events per year. Twenty-three thrombotic events occurred in the anticoagulated group all with an International Normalized Ratio (INR) less than 2.7. This incidence of vascular access thrombosis may be prevented when patients are maintained at an optimal INR of 2.7-3.0. CONCLUSIONS: Hypercoagulability has been a major etiologic factor in PTFE graft thrombosis. Hypercoagulable states are often found in patients with multiple graft thromboses and in patients with nonanatomic causes for thrombosis. Antiphospholipid antibodies are prevalent in the patients with PTFE graft thrombosis, as well as abnormalities in the Protein-C, Protein-S, and Antithrombin III systems. PTFE graft thrombosis has been a frequent cause of morbidity in patients on hemodialysis, and diagnostic evaluation should include a hypercoagulability profile. Based on our data, warfarin therapy should be instituted when hypercoagulable states are found, unless otherwise contraindicated, and INR maintained at 2.7-3.0 to decrease morbidity and frequency of graft thrombosis.