An elderly patient with prosthetic mitral and aortic valves has had two small, presumably cardioembolic strokes while anticoagulated (international normalized ratio [INR] 2.5-3.5). Would increasing his desired INR to between 3.5 and 4.5 decrease his chance of further strokes?
—Michael Garrett, MD, Paradise Valley, Ariz.

There are few data indicating any difference between the INRs you cited (except for an increased risk of bleeding), but there are reported benefits from adding an antiplatelet agent to the warfarin dosage in patients with prosthetic valves (N Engl J Med. 1993;329:524-29).
—Peter F. Cohn, MD (113-8)

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