May increase risk of haemorrhage in elderly patients

Editor—In their study on the use of anticoagulants in patients with atrial fibrillation Mark Sudlow and colleagues do not seem to appreciate that patients may not have been prescribed warfarin because treatment was not indicated as well as because it was contraindicated.1

There is clear evidence that warfarin reduces the risk of stroke by about two thirds in patients with atrial fibrillation—from 12% to 4% per year in secondary prevention2 and from 4% to 1.5% per year in primary prevention. However, only 40-50% of these strokes are major disabling or fatal strokes,3 the reduction in their incidence being of the order of 4% per year in secondary and 1.1% per year in primary prevention.

This must be set against the risks inherent in treatment with warfarin. Large trials of treatment with warfarin in patients with atrial fibrillation have suggested that the incidence of major haemorrhage is about 2.8% per year1; this compares with a typical control figure of 0.7% per year. The figures become more worrying when older patients are considered. One stroke prevention trial reported a rate of major haemorrhage of 4.2% per year in patients over 75.4 A retrospective and prospective study of 2376 patients receiving warfarin for a variety of indications reported an incidence of life …