Atrial fibrillation, the most common chronic
arrhythmia, results in an increased risk of
stroke. Anticoagulation
therapy can reduce this risk, but appears to be underused. The objective of this study was to examine the use of
warfarin and prevalence of
stroke in patients with rheumatic, nonrheumatic valvular and nonvalvular
atrial fibrillation. Between January 1993 and December 1998, 457 chronic
atrial fibrillation patients with continuous follow-up in our hospital were identified as having
rheumatic heart disease (n = 114): nonrheumatic valvular disease (n = 65); or nonvalvular disease (n = 278).
Warfarin was used less often in patients with nonrheumatic valvular (16.7%) and nonvalvular diseases (20.1%) than in those with
rheumatic heart disease (81.6%, p < 0.001). In contrast, the prevalence of
stroke among patients with nonvalvular disease was 40.3% which was similar to the 33.3% found in patients with
rheumatic heart disease but significantly higher than the 24.6% found in patients with nonrheumatic valvular disease (p < 0.05). A history of
stroke did not alter the trend of use of
warfarin among the three groups of patients. Only 20.6% of patients on
warfarin received monthly monitoring of prothrombin time. In conclusion, the anticoagulation
therapy in our patients with chronic
atrial fibrillation, regardless of their associated valvular diseases, is significantly underutilized. This underuse could account for a high prevalence of
stroke. This risk of
stroke, however, is less in patients with nonrheumatic valvular
discase than in those with nonvalvular
atrial fibrillation.