More evidence against low INR targets
Patients who receive inadequate anticoagulation therapy have a substantially increased risk of death and severe disability from atrial fibrillation-related stroke, according to researchers from Harvard Medical School, Boston
(New England Journal of Medicine 2003;349:1019).
Dr Elaine Hylek and colleagues studied ischaemic strokes in 13,559 patients
with nonvalvular atrial fibrillation. A total of 188 patients had a stroke
while being treated with warfarin. Of those with an international normalised
ratio (INR) of less than 2.0 (considered inadequate in these patients),
15 per cent either experienced a severe stroke or died compared with
5 per cent of those with an INR level greater than 2.0. “It is
unusual to have a stroke when on anticoagulation therapy, but this study
shows that it is possible to reduce the severity and complications for
patients who do experience that uncommon event,” said Dr Hylek.
The researchers also observed little additional risk of intracranial
haemorrhage with the use of warfarin until INR values exceeded 3.9.
“
All anticoagulation therapy has risks, and balancing those risks against
the possibility that insufficient therapy will lead to a severe stroke
is a serious concern. Our results show that the risk of intracranial
haemorrhage does not increase until INR levels reach 4.0, which should
reassure patients and physicians that the currently advocated INR target
of 2.5 — a range of 2.0 to 3.0 — is most likely the right
balance point,” Dr Hylek added. |
