PRIMARY STROKE PREVENTION IN NONVALVULAR ATRIAL-FIBRILLATION - IMPLEMENTING THE CLINICAL-TRIAL FINDINGS

OBJECTIVE: To review the clinical trials evaluating warfarin for prima ry stroke prophylaxis in nonvalvular atrial fibrillation (NVAF), to di scuss the relative benefits and risks of warfarin versus aspirin thera py, and to review the clinical practice guidelines and identify potent ial barriers to their implementation in clinical practice. DATA SOURCE S: A MEDLINE literature search was performed to identify clinical tria ls of antithrombotic therapy for NVAF, clinical practice guidelines, s tudies evaluating physician practices and attitudes, cost-effectivenes s studies, and pertinent review articles. Key search terms included at rial fibrillation, stroke, antithrombotic, warfarin, aspirin, and cost -effectiveness. DATA EXTRACTION: Prospective, randomized clinical tria ls were selected for analysis. Clinical practice guidelines from recog nized panels of experts were reviewed. Comprehensive review articles w ere selected. DATA SYNTHESIS: NVAF is a common arrhythmia that is asso ciated with a substantial risk for stroke. Seven prospective, randomiz ed, clinical trials have conclusively demonstrated the efficacy of war farin for stroke prevention. The greatest benefits are achieved in old er patients and those with comorbidities that increase their risk for stroke. The potential benefits of preventing a devastating stroke, how ever, must be weighed against the potential for bleeding complications . Warfarin has been shown to be cost-effective in high-risk patients, provided the rate of complications is minimized. Nonetheless, many phy sicians remain hesitant to implement warfarin therapy in older, high-r isk patients. The clinical data on aspirin are less consistent than th ose observed with warfarin. Aspirin appears to be most effective in yo unger individuals or those considered to be at low risk for stroke. CO NCLUSIONS: In patients with NVAF, the personal, social, and economic c onsequences of stroke are often devastating. Clinical trials have prov ided definitive proof that the risks of stroke can be significantly re duced through the use of appropriate antithrombotic therapy. Despite t his evidence and the recommendations of a number of clinical practice guidelines, variations in care exist that continue to place patients a t risk. Additional outcomes research is needed to evaluate the impact of the clinical trial findings and practice guidelines on clinical pra ctice and to develop methods for overcoming barriers to implementation .