New Study Supports INR of 2 to 3 for Elderly Patients with A. Fib.

Henry I. Bussey, Pharm.D., FCCP, FAHA
November 2004

Review: Fang MC, Chang Y, Hylek EM, Rosand J, Greenberg SM, Go AS, Singer DE. Advanced age, anticoagulation intensity, and risk for intracranial hemorrhage among patients taking warfarin for atrial fibrillation. Ann Intern Med. 2004 Nov 16;141(10):745-52.

Elaine Hylek and her group from Boston have published several papers examining the benefit and safety of different levels of anticoagulation in selected patient populations. In this most recent paper by Fang, et al (including Dr. Hylek) (Ann Intern Med. 2004; 141:745-752) 170 cases of atrial fibrillation with intracranial hemorrhage were compared with 1,020 matched patients who did not have an intracranial hemorrhage. Key findings included that older age increased the risk of intracranial hemorrhage, but the increase was seen primarily when patients exceeded 85 years of age. An elevation in INR also was related to intracranial hemorrhage, but the increase was seen primarily when the INR was > 3.5. Finally, an INR of < 2 was not found to carry a lower risk of intracranial hemorrhage than an INR between 2 and 3. Consequently, there appears to be no benefit of treating elderly atrial fibrillation patients to an INR of less than 2 since it does not appear to be significantly safer and (as indicated in earlier studies by Hylek and colleagues) the risk of stroke doubles when the INR falls to 1.7 and triples when the INR is at 1.5.