National patterns of warfarin use in atrial fibrillation.

BACKGROUND: Despite consensus that patients with atrial fibrillation benefit from warfarin sodium anticoagulation, little is known about national trends and predictors of anticoagulant use.
METHODS: We analyzed 1062 visits by patients with atrial fibrillation to randomly selected office-based physicians included in the National Ambulatory Medical Care Surveys in 1980, 1981, 1985, and 1989 through 1993. Warfarin and aspirin use in these patients was extrapolated to national patterns and logistic regression was used to determine independent predictors.
RESULTS: Patients with atrial fibrillation made an estimated 1.3 (1980) to 3.1 (1992) million annual visits to physicians. Warfarin use in atrial fibrillation increased from 7% in 1980 and 1981 to 32% in 1992 and 1993 (P < .001 for trend). In 1992 and 1993, patients 80 years or older were significantly less likely to be taking warfarin (19%) compared with younger patients (36%), but showed similar rates of increase from 1980 and 1981 to 1992 and 1993. In 1992 and 1993, anticoagulation therapy was significantly more likely to be reported in visits to cardiologists (32%) and general internists (40%) compared with general and family practitioners (15%), but was similar in women (34%) and men (30%). Residents of the South (16%) had significantly lower rates of warfarin use than those in other regions of the United States (36%). Aspirin use increased from 3% to 10% (P = .001 for trend) and showed little overlap with warfarin use. Multiple logistic regression indicated that more recent year, residence outside the South, patient aged 65 to 74 years, and visits to cardiologists and internists increased the likelihood of warfarin use.
CONCLUSIONS: Anticoagulant use for atrial fibrillation has increased dramatically. The substantial increase from 1989 and 1990 to 1992 and 1993 coincided with the publication of several randomized clinical trials reporting the benefits of warfarin. Although it is unrealistic to expect universal warfarin use, the 1992 and 1993 rate of 32% is probably suboptimal given the benefit of anticoagulation in preventing embolic strokes. The oldest patients, in whom warfarin may have its greatest benefit, appear to have the lowest rates of anticoagulant use.