MedWire News: Patients with stroke have smaller infarcts if they were taking warfarin and had a therapeutic international normalized ratio (INR) at the time of symptom onset, report researchers.
"This relation between admission INR and acute lesion volume appears to persist into subacute to chronic phase, suggesting that the impact of INR on acute infarct volume is not a transient event," they write in the Annals of Neurology.
Hakan Ay (Harvard Medical School, Boston, USA) and team studied 93 stroke patients who were using warfarin at onset and 93 non-anticoagulated patients who were matched for stroke subtype.
They found that the higher a patient's INR on admission, the smaller their infarct size on diffusion-weighted imaging within 24 hours of onset.
"It is possible that preadmission warfarin use may have caused formation of more fragile embolus or prevented thrombus propagation at the site of occlusion resulting in earlier recanalization," the team speculates.
Patients with therapeutic INRs (at least 2.0) had infarcts averaging 3.4 ml, compared with 13.1 ml in patients with a sub-therapeutic INR and 14.7 ml in patients not using an anticoagulant.
Having a therapeutic INR remained associated with smaller infarct volume on multivariate analysis, and was also associated with infarct size on follow-up imaging between days 5 and 75.
INR was associated with the severity of neurologic impairment on admission and with functional status at discharge. Patients with sub-therapeutic INRs were 2.3-fold more likely to be severely disabled or dead at discharge (modified Rankin Scale score 4-6) than patients with therapeutic INRs.
Current guidelines recommend warfarin use in high-risk patients with atrial fibrillation, but numerous studies have demonstrated underuse of the anticoagulant.
"Equally problematic is that patients with AF receiving warfarin remain within the therapeutic INR range only approximately 50% of the time while they are on treatment," say Ay et al.
"If confirmed in future studies, our results strengthen the necessity for complying with published guidelines and may provide an incentive to healthcare professionals to implement better outpatient systems to improve patient compliance to anticoagulation."
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