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Individuals on oral anticoagulants for atrial fibrillation should have their INR regularly monitored to reduce the risk of stroke

Individuals on oral anticoagulation treatment with a coumarin derivative (such as Panwarfin or Sintrom) for atrial fibrillation should have their anticoagulation regularly monitored, ensuring that their international normalised ratio, INR, remains at therapeutic levels (between 2.0 and 3.5), otherwise they run an increased risk for stroke. This was concluded by analyzing data from the Registry of the Canadian Stroke Network, a large contemporary prospective database of patients with stroke (Potentially preventable strokes in high-risk patients with atrial fibrillation who are not adequately anticoagulated, published in the journal “Stroke”, Jan. 2009).

Atrial fibrillation increases the risk for ischaemic stroke by four times and doubles the risk for death. It is well known that anticoagulation reduces the risk of stroke among people with atrial fibrillation by two thirds. These individuals should maintain their INR between 2.0 and 3.5. If INR is below 2.0 the patient is not protected, while if INR is over 4.0 the risk of complications (bleeding) related to the anticoagulant sharply increases.

In the afore-mentioned study, it was found that among patients admitted with an ischaemic stroke (either their first or a subsequent one), had known atrial fibrillation and had been classified as high risk for systemic emboli, and should therefore have remained on anticoagulation, most were either not taking warfarin at all or were inadequately anticoagulated (INR<2.0) at the time of their stroke.

Another very interesting finding was the fact that many of the patients of the study were on no relevant treatment (anticoagulation, antiplatelet, antitrombotic) whatsoever.