AJM Theme Issue: Cardiology
Clinical research study
Warfarin Prescribing in Atrial Fibrillation: The Impact of Physician, Patient, and Hospital Characteristics

https://doi.org/10.1016/j.amjmed.2005.09.052Get rights and content

Abstract

Purpose

The study investigated the determinants of warfarin use in patients with atrial fibrillation (AF).

Methods

We assembled a retrospective cohort of community-dwelling elderly patients (aged ≥66 years) with AF using linked administrative databases. We identified the physicians responsible for the ambulatory care of these patients using physician service claims and compared patients who did and did not have an identifiable provider. For those patients with an identifiable provider, we assessed the association between patient, physician, and hospital factors and warfarin use.

Results

Our cohort consisted of 140,185 patients, of whom 116,200 (83%) had an identifiable cardiac provider. Patients without a provider were significantly more likely to have comorbid conditions that increase their risk of warfarin-associated bleeding. After adjustment for clinical factors, patients without a provider were significantly less likely to receive warfarin (odds ratio 0.37, 95% confidence interval: 0.36-0.38). Of patients with providers, 50,551 patients (43.5%) received warfarin within 180 days after hospital discharge. Warfarin use was positively associated with AF-associated stroke risk factors (eg, prior stroke, congestive heart failure) and negatively associated with warfarin-associated bleeding risk factors (eg, history of intracerebral hemorrhage). After controlling for patient and hospital factors, patients cared for by noncardiologist physicians with cardiology consultation were more likely to receive warfarin then patients treated in noncollaborative environments.

Conclusions

Warfarin continues to be substantially underprescribed to patients who are at high risk for AF-associated cardioembolic stroke. Our findings highlight the need for targeted quality improvement interventions and suggest preferred models of AF care involving routine collaboration between cardiologists and other physicians.

Section snippets

Setting and Design

We assembled a retrospective cohort of community-dwelling elderly patients (aged ≥66 years) with AF in Ontario, Canada, by linking several large health care databases. Ontario has a population of approximately 12 million people, of whom approximately 1.5 million are aged 65 years or older.27 All Ontario residents have universal, publicly funded health insurance for hospital care and physician services, and elderly residents also have prescription drug coverage for drugs listed in the provincial

Results

During our study time frame, 168,697 patients were hospitalized with a most-responsible or major comorbid diagnosis of AF. We excluded 28,512 patients who had valvular heart disease, thyroxicosis, or a high probability of transient AF; who lived in a long-term care setting; or who died within 60 days of hospital discharge. Therefore, our cohort consisted of 140,185 patients of whom 116,200 (83%) had an identifiable MRCP.

Discussion

The findings of this very large population-based study of patients with nonvalvular AF support existing evidence that warfarin is substantially underprescribed to patients who are at high risk of AF-associated cardioembolic stroke. Because the factors conventionally considered to be associated with higher rates of anticoagulation-related bleeding (eg, a history of gastrointestinal or intracerebral hemorrhage or advanced age) may not substantially increase bleeding risk,37 our results suggest

Acknowledgments

The authors are grateful to Kathy Sykora and Jin Leo for their computing expertise. Dr. Choudhry had full access to all the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.

References (44)

  • W.M. Feinberg et al.

    Prevalence, age distribution, and gender of patients with atrial fibrillation. Analysis and implications

    Arch Intern Med

    (1995)
  • A.S. Go et al.

    Prevalence of diagnosed atrial fibrillation in adults: national implications for rhythm management and stroke prevention: the anticoagulation and risk factors in atrial fibrillation (ATRIA) study

    JAMA

    (2001)
  • A. Majeed et al.

    Trends in the prevalence and management of atrial fibrillation in general practice in England and Wales, 1994-1998analysis of data from the general practice research database

    Heart

    (2001)
  • W.A. Wattigney et al.

    Increasing trends in hospitalization for atrial fibrillation in the United States, 1985 through 1999implications for primary prevention

    Circulation

    (2003)
  • R.G. Hart et al.

    Antithrombotic therapy to prevent stroke in patients with atrial fibrillationa meta-analysis

    Ann Intern Med

    (1999)
  • P.A. Wolf et al.

    Atrial fibrillation as an independent risk factor for strokethe Framingham Study

    Stroke

    (1991)
  • V. Fuster et al.

    ACC/AHA/ESC guidelines for the management of patients with atrial fibrillation. A report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines and the European Society of Cardiology Committee for Practice Guidelines and Policy Conferences (Committee to develop guidelines for the management of patients with atrial fibrillation) developed in collaboration with the North American Society of Pacing and Electrophysiology

    Eur Heart J

    (2001)
  • M.C. Fang et al.

    National trends in antiarrhythmic and antithrombotic medication use in atrial fibrillation

    Arch Intern Med

    (2004)
  • A.S. Go et al.

    Warfarin use among ambulatory patients with nonvalvular atrial fibrillationthe anticoagulation and risk factors in atrial fibrillation (ATRIA) study

    Ann Intern Med

    (1999)
  • K.H. Humphries et al.

    New-onset atrial fibrillationsex differences in presentation, treatment, and outcome

    Circulation

    (2001)
  • N. Cohen et al.

    Warfarin for stroke prevention still underused in atrial fibrillationpatterns of omission

    Stroke

    (2000)
  • P.A. Wolf et al.

    Atrial fibrillation: a major contributor to stroke in the elderly. The Framingham Study

    Arch Intern Med

    (1987)

    • Cited by (0)

    This work was supported by the Harvard Pilgrim Health Care Foundation and a Canadian Institute for Health Research Chronic Disease New Emerging Theme (NET) program grant (NET 54010). Dr. Choudhry also was supported by the Harvard Medical School Fellowship in Pharmaceutical Policy Research, a Frank Knox Scholarship from Harvard University, and a Canadian Institutes of Health Research Post-Doctoral Fellowship. Drs. Soumerai and Ross-Degnan are investigators in the HMO Research Network Center for Education and Research in Therapeutics, funded by the U.S. Agency for Healthcare Research and Quality, and were also supported by grant R01 AG022362-01 from the National Institute on Aging. Dr. Laupacis is a Senior Scientist of the Canadian Institutes of Health Services Research.

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