D-Dimer versus International Normalized Ratio of Prothrombin Time in Ischemic Stroke Patients Treated with Sufficient Warfarin

BackgroundIn patients receiving chronic warfarin therapy, the international normalized ratio of prothrombin time (PT-INR) reportedly correlates with the incidence, size, severity, and outcome of ischemic stroke, and thus there are guidelines for the optimal PT-INR range that is to be maintained during secondary or primary prevention of ischemic stroke. However, the details of ischemic stroke in patients in whom an optimal PT-INR is maintained by warfarin therapy have not been thoroughly investigated. We conducted a retrospective study to determine the predictors of the size, severity, and outcome of ischemic stroke occurring in patients under chronic warfarin therapy and maintenance of an optimum PT-INR.MethodsThe study group comprised 22 consecutive acute ischemic stroke patients who were receiving warfarin and whose PT-INR was within the optimal range on admission. The PT-INR and plasma D-dimer level of these patients on admission were analyzed in relation to infarction volume, National Institutes of Health Stroke Scale score on admission, and modified Rankin Scale score at discharge.ResultsPT-INR did not correlate with infarction volume, severity, or outcome. The D-dimer level correlated positively and significantly with the volume (r = .49, P < .05), severity (r = .54, P < .05), and outcome of ischemic stroke (r = .61, P < .01) and did not correlate with the PT-INR (r = −.27, P = .23).ConclusionsWhen the PT-INR is within optimal range in patients receiving chronic warfarin therapy but who suffer an ischemic stroke, the admission D-dimer level, but not PT-INR, correlates with the size, severity, and outcome of the stroke. Thus, monitoring the D-dimer level in patients receiving long-term warfarin therapy is important, regardless of whether the optimal PT-INR is maintained.