Use of warfarin for nonvalvular atrial fibrillation in nursing home patients
T. E. Lackner and G. N. Battis
Pharmacy Corporation of America, Minneapolis, USA.
OBJECTIVE: To assess warfarin sodium use and anticoagulant monitoring in
nursing home patients with nonvalvular atrial fibrillation (NVAF),
according to American College of Chest Physicians Consensus Conference
guidelines. DESIGN: Retrospective, multicenter, point-prevalence study.
SETTING: Nursing homes in Minneapolis-St Paul, Minn. PATIENTS: Nine-hundred
two patients 60 years and older, from whom 69 with a diagnosis of NVAF and
16 with valvular atrial fibrillation (VAF) (control group) were identified.
DATA COLLECTED: Patient demographics and diseases, diagnostic tests for
atrial fibrillation (AF), antithrombotic drugs and dosage, anticoagulant
activity test results, other drugs, and drug allergies were determined by
chart review and attending physician response to written communication from
the nursing home's medical director and consultant pharmacist. MAIN OUTCOME
MEASURES: Prevalence of NVAF, VAF, and risk factors for thromboembolism and
major bleeding, use of warfarin and other antithrombotic drugs for AF,
anticoagulation control, and the relationship of warfarin dose with the
recommended international normalized ratio (INR) and prothrombin time (PT).
RESULTS: Nonvalvular AF was documented in 7.6% of the patients. Most
patients with NVAF were at an increased risk for stroke, yet only 20%
without a conventional contraindication to warfarin use experienced
anticoagulation; a greater proportion of patients with VAF experienced
anticoagulation. The INR was within the recommended range for NVAF over a
6-month period 37% of the time and recommended PT, 52% of the time. An
equal percentage of warfarin dose changes occurred in response to a PT
ratio outside the recommended range as occurred with an INR outside the
recommended range. CONCLUSIONS: Many nursing home patients have NVAF with
comorbid conditions that subject them to a greater than average risk for
thromboembolic stroke. Warfarin is underused for stroke prophylaxis and
often is not used according to the American College of Chest Physician
guidelines. Physicians, nurses, and consultant pharmacists must be better
informed about (1) known risk factors for thromboembolism and major
bleeding to identify patients with AF who will most likely benefit from
warfarin therapy, (2) maintaining an INR of 2 to 3, and (3) the need for
small warfarin dose adjustments in elderly patients.
