Is warfarin really underused in patients with atrial fibrillation?

Abstract

Context: There is agreement that warfarin decreases stroke risk in patients with atrial fibrillation (AF), but prior studies suggest that warfarin is markedly underused, for unclear reasons.

Objective: To determine if warfarin is underused in the treatment of patients with atrial fibrillation.

Design: Cross-sectional.

Setting: Tertiary care VA hospital.

Patients: All patients with a hospital or outpatient diagnosis of AF between 10/1/95 and 5/31/98.

Data collection: One or more physician investigators reviewed pertinent records for each patient. When any of the 3 investigators thought warfarin might be indicated, the patient's primary care provider completed a survey regarding why warfarin was not used.

Results: Of 1,289 AF patients, 844 (65%) had filled at least 1 warfarin prescription. Of the 445 remaining, 19 had died, 5 had inadequate medical records, and 54 received warfarin elsewhere, leaving 367 patients. Of these, 160 had no documented AF, 53 had only a history of AF, and 49 had only transient AF. Of the remaining 105 patients, 17 refused warfarin therapy and 72 had documented contraindications to warfarin use including bleeding risk or history, fall risk, alcohol abuse, or other compliance problems. The reasons for not using warfarin among the 16 patients remaining included provider oversight (n = 4) and various reasons suggesting provider knowledge deficits.

Conclusion: In contrast to prior studies that suggested that warfarin is markedly underused, we found that few patients with AF and no contraindication to anticoagulation were not receiving warfarin. We believe that differing study methodologies, including the use of physician review and provider survey, may explain our markedly different rate of warfarin underutilization, although local institutional factors cannot be excluded. The findings suggest that primary providers may be far more compliant with the standard of care for patients with atrial fibrillation than previously believed.

FIGURE 1

Reasons for warfarin nonuse among 367 living veterans with adequate records, an ICD-9 diagnosis of AF, and no evidence of warfarin use in the preceding 5 years.