Robert A. Hughes

Evolving models of warfarin management: anticoagulation clinics, patient self-monitoring, and patient self-management.

Since the introduction of dicoumarol in the early 1940s, oral anticoagulants have been the mainstay of therapy for the long-term treatment and prevention of thromboembolism. Anticoagulants have recently undergone a surge in popularity with the confirmation of their importance in preventing cerebral thromboembolism from atrial fibrillation 1-6 and now the confirmation of their beneficial effect in preventing recurrent myocardial infarction. 7-s In 1994 warfarin sodium was the fifth most prescribed cardiovascular medication and the thirteenth most prescribed medication in the United States. 9 Unfortunately oral anticoagulants have an extremely narrow therapeutic index, and many physicians are reluctant to treat patients because of the fear of hemorrhagic complications. 1°-13 Additionally, the l imitations of prothrombin time measurement 14 and the requirements of frequent monitoring, patient contact, and dose adjus tment make managing anticoagulation labor intensive and costly and provide another barrier to treatment. The complexity and fragmentation of routine care further enhance the potential for communication errors and laboratory testing that can lead to substantial complications and cost. In fact, the model of warfarin management is a potential risk fac~ tor for adverse events that is rarely considered when discussing wa~arin-related risk factors. The following discussion focuses on evolving models of anticoagulation management with the potential for improving the safety, efficacy, and cost-effectiveness of therapy and removing potential barriers to treatment. Coordinated anticoagulation care: The anticoagulation clinic. What constitutes coordinated anticoagu-

Effect of low-intensity warfarin anticoagulation on level of activity of the hemostatic system in patients with atrial fibrillation. BAATAF Investigators.

BACKGROUND AND PURPOSE The Boston Area Anticoagulation Trial for Atrial Fibrillation (BAATAF) demonstrated that low-intensity warfarin anticoagulation can, with safety, sharply reduce the rate of stroke in patients with nonvalvular atrial fibrillation. The beneficial effect of warfarin was presumably related to a decrease in clot formation in the cardiac atria and subsequent embolization. METHODS To assess the effect of warfarin therapy on in vivo clotting in patients in the BAATAF, we measured the plasma level of prothrombin activation fragment F1+2. One sample was obtained from 125 patients from the BAATAF; 62 were taking warfarin and 63 were not taking warfarin (control group). RESULTS The warfarin group had a 71% lower mean F1+2 level than the control group (mean F1+2 of 1.57 nmol/L in the control group compared with a mean of 0.46 nmol/L in the warfarin group; P < .001). F1+2 levels were higher in older subjects but were consistently lower in the warfarin group at all ages. Fifty-two percent of patients in the control group were taking chronic aspirin therapy at the time their F1+2 level was measured. Control patients taking aspirin had F1+2 levels very similar to control patients not taking aspirin (mean of 1.52 nmol/L for control patients on aspirin compared with 1.64 nmol/L for control patients off aspirin; P > .1). CONCLUSIONS We conclude that prothrombin activation was significantly suppressed in vivo by warfarin but not aspirin among patients in the BAATAF. These findings correlate with the marked reduction in ischemic stroke noted among patients in the warfarin treatment group observed in the BAATAF.

Workshop: Reimbursement for anticoagulation services

Anticoagulant therapy units (ATUs) have been developed to enhance quality expertise in the care of patients receiving anticoagulant therapy with warfarin and to coordinate care. The Anticoagulation Forum, representing the program directors and staff of ATUs, surveyed its membership for its 1995 National Conference on Anticoagulation Therapy. Responses were received from 109 programs with an average of 467 patients each. The consensus of program directors was that inadequate reimbursement was an important deterrent to the expansion of such care. A review of current literature reveals substantially superior outcomes in anticoagulation units versus routine care, with estimates of 4.5 fewer major bleeding events per 100 patient-years of treatment and 6 fewer thromboembolic events per 100 patientyears of treatment. The Anticoagulation Forum encourages third-party payers to develop appropriate strategies to reimburse this type of care, which should substantially improve the outcomes of anticoagulant therapy while reducing overall costs.