ANTICOAGULATION IN ATRIAL-FIBRILLATION - DOES EFFICACY IN CLINICAL-TRIALS TRANSLATE INTO EFFECTIVENESS IN PRACTICE

Background: Several recent randomized clinical trials of anticoagulati on in atrial fibrillation have demonstrated significant reduction in s troke rates with a small incidence of bleeding complications. The obje ctive of this study was to determine whether the recommendations resul ting from these trials have been implemented into routine practice, an d if the anticoagulation control, therapeutic efficacy, and low compli cation rates achieved in the trials have been matched in community pra ctice. Methods: We analyzed the anticoagulation practices and outcomes obtained for patients in atrial fibrillation at a large staff model h ealth maintenance organization (HMO). We reviewed the medical records of all patients in atrial fibrillation as of April 1990. We compared d emographic characteristics and clinical risk factors between HMO patie nts and those in the clinical trials. We also compared anticoagulation monitoring, adequacy of anticoagulation control, and clinical outcome s at the HMO with those achieved in the clinical trials. Results: Of 2 38 HMO patients in atrial fibrillation, 198 were without contraindicat ions and therefore eligible for anticoagulation. Of these, 168 were of fered anticoagulation (84.8%) and 156 were receiving anticoagulation t herapy (78.8% of those eligible). The HMO patients had a greater preva lence of comorbidities than those in the clinical trials. The routine monitoring interval at the HMO was estimated at between 36.3 and 40.9 days (compared with 21 to 28 days reported in the clinical trials). Th e prothrombin time ratios at the HMO were in the target range on 50% o f days compared with 68% of days in the clinical trials. The annual st roke and major bleeding rates in the HMO patients (1.3% and 0.6%, resp ectively) were not significantly different from the rates in the clini cal trials (1.3% and 1.1%, respectively). The annual minor bleeding ra te of 13.6% at the HMO was greater than the 7.8% to 8.4% rates in the two trials with better anticoagulation control (Boston Area Anticoagul ation Trial for Atrial Fibrillation and Stroke Prevention in Atrial Fi brillation Study) but was not significantly different than the rates o f 12.7% and 13.7% Of the two trials with poorer anticoagulation contro l (Canadian Atrial Fibrillation Anticoagulation Study and Stroke Preve ntion in Nonrheumatic Atrial Fibrillation Study). Conclusions: Anticoa gulation practices in this community setting appear to be good in that a large majority of patients were receiving anticoagulation therapy, and there were few major adverse outcomes. However, this study illustr ates two common problems in attempting to apply the results of randomi zed clinical trials to routine practice: (1) differences between commu nity patient populations and those on which the conclusions of clinica l trials are based, and (2) less successful application of therapeutic interventions in settings other than that of a controlled clinical tr ial. The greater prevalence of comorbidities in the HMO patient popula tion appears to convey a greater overall risk of thromboembolism and b leeding complications than in the clinical trials. In addition, the su boptimal anticoagulation control achieved at the HMO may increase the risks and decrease the potential benefits compared with those achieved in the clinical trials. Thus, the efficacy demonstrated in the clinic al trials of anticoagulation in atrial fibrillation may not be directl y translated into effectiveness in practice.