More about Warfarin

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" High-quality randomized trials demonstrate that warfarin therapy dramatically

reduces the risk for ischemic stroke associated with atrial fibrillation (1).

These trials and observational studies also indicate that the benefit of

anticoagulation is markedly reduced at INRs lower than 2.0 (2). Our study showed

that the risk for intracranial hemorrhage increases with age and with INRs above

3.5. However, patients receiving anticoagulation did not have a reduced risk for

intracranial hemorrhage at INRs less than 2.0. Thus, it appears that maintaining

the INR in the 2.0 to 3.0 range maximizes the benefits of warfarin while

minimizing the risks.

Unfortunately, older patients are at higher risk for both ischemic stroke and

intracranial hemorrhage; erratic anticoagulation exacts a greater penalty. As

Dr. Ruiz-Ruiz notes, numerous factors can lead to difficult warfarin management

in the elderly, including polypharmacy, multiple comorbid conditions, and

physical and mental frailty. We agree that the anticoagulation decision must be

individualized and must engage the patient or patient caregiver. Appropriate

decision making should account for whether patients can be safely maintained

within a therapeutic INR range of 2.0 to 3.0.

Although intracranial hemorrhage risk increases at older ages, other validated

clinical predictors of intracranial hemorrhage are few. As a consequence,

individualized risk assessment often represents guesswork. The preponderance of

evidence favors the use of warfarin in elderly patients with atrial

fibrillation. However, the large proportion of elderly patients with atrial

fibrillation, their increased risk for intracranial hemorrhage, and the

devastating consequences of intracranial hemorrhage in patients taking warfarin

all highlight the need to find better predictors of this condition. Such

knowledge would make individualized decisions about anticoagulation in atrial

fibrillation much more rational and effective. "

From University of California, San Francisco, San Francisco, CA 94143, and

Massachusetts General Hospital, Boston, MA 02114.