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

Abstract

In 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. The 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. PT-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). When 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.