Oral anticoagulants as secondary prophylaxis of thrombosis in patients with polycythemia vera: a retrospective analysis of 15 patients.

Thrombotic complications are the leading cause of mortality in patients with polycythemia vera (PV). Phlebotomy and myelosuppressive agents are able to reduce the frequency of thrombosis; however, despite adequate control of myeloproliferation, the thrombotic risk remains increased in PV. This has led to a search for additional antithrombotic agents suited to reduce the rate of thrombotic events in PV. We have retrospectively analyzed 15 patients with PV who received oral anticoagulants (OA) as secondary prophylaxis of thrombosis at our institution with the aim of investigating this treatment approach in patients with PV. Despite OA treatment, 2 (13%) of 15 patients displayed recurrent venous thromboembolism, 3 patients (20%) displayed recurrent arterial thromboembolism, whereas 1 patient (7%) developed recurrent restenosis/occlusion of a transjugular intrahepatic porto-systemic shunt (TIPSS) implanted because of an underlying Budd-Chiari syndrome. Three (20%) of 15 patients had a total of 5 bleeding events during OA treatment, two of which were major bleedings. In none of the major bleedings over-anticoagulation was the reason for bleeding. Within the limitations of a retrospective analysis in a small number of patients, our data suggest that meticulous control of anticoagulant therapy is of critical importance in patients with PV, since in several of our patients recurrent thromboembolic events were associated with a low anticoagulation intensity of INR<2.0. In our opinion, a prospective clinical trial similar to the recently performed ECLAP study would be needed to more thoroughly elucidate the efficacy of OA in the secondary prophylaxis of thrombosis in PV.