vitamin-k-semiquinone-radical and Activated-Protein-C-Resistance

: Activated protein C resistance (APC-R) is assessed as part of thrombophilia screening, preferably in patients not taking oral anticoagulants. Rivaroxaban is known to alter some APC-R assays. To our knowledge, there have been no reports on the effect of rivaroxaban on the Russell viper venom time (RVVT)-based APC-R assay in real-life patients. In 168 consecutive outpatients suspected of having venous thromboembolism because of thrombophilia, APC-R was determined using the RVVT-based ProC Ac R assay (Siemens, Marburg, Germany). Patients receiving rivaroxaban or vitamin K antagonists were eligible. We measured rivaroxaban concentrations using the anti-Xa Biophen DiXal assay (Hyphen Biomed, Neuville-Sur-Oise, France) and factor V Leiden using the real-time PCR. APC-R was detected in 23 (28%) patients on rivaroxaban (n = 81) administrated 2-48 h since the blood draw, 15 (28%) patients on vitamin K antagonists (n = 54), and in four (12%) patients off anticoagulation (n = 33). Compared with nonanticoagulated patients, APC-R ratios were similar in patients on rivaroxaban, without any correlation with rivaroxaban concentrations (from 0 to 303 μg/l). None of the patients on rivaroxaban were found to have false-negative or false-positive APC-R ratios. Rivaroxaban concentrations up to 300 μg/l do not affect results of the ProC Ac R RVVT-based assay, which could be recommended in patients referred to a clinic for thrombophilia screening in whom the time since the last dose of rivaroxaban is uncertain.

Topics: Activated Protein C Resistance; Adult; Factor Xa Inhibitors; Female; Humans; Male; Middle Aged; Prothrombin Time; Rivaroxaban; Thrombophilia; Venous Thromboembolism; Vitamin K

Vitamin K antagonists (VKAs) are widely used in thromboembolic diseases. We report five cases of necrotic leg ulcers having a particularly severe course and in which withdrawal of VKA treatment alone enabled healing.. Five patients presented with necrotic leg ulcers clinically evocative of necrotic angiodermatitis or vasculitis. Histological features were variable, including inconstantly inflammatory lesions (leukocytoclastic vasculitis) and microthrombosis. None of the patients had laboratory signs of autoimmune disease. Healing occurred in all patients only after withdrawal of VKA therapy (fluindione or acenocoumarol). Associated vascular diseases included superficial venous, distal arterial insufficiency and postphlebitic disease. In three cases, thrombotic factors were observed: hyperhomocysteinaemia or heterozygous Factor V Leiden mutation.. Although the causative role of VKAs is based solely on chronological criteria, this potential side effect deserves publication because of its practical therapeutic consequences. The physiopathological mechanisms accounting for the role of VKAs, including immunoallergic phenomena and, above all, microcirculatory thrombotic processes, are hypothetical and not universally accepted.

Topics: Acenocoumarol; Activated Protein C Resistance; Aged; Aged, 80 and over; Anticoagulants; Diabetic Angiopathies; Factor V; Female; Humans; Hyperhomocysteinemia; Leg Ulcer; Male; Necrosis; Phenindione; Polyarteritis Nodosa; Postoperative Complications; Purpura; Thrombophilia; Varicose Ulcer; Vasculitis, Leukocytoclastic, Cutaneous; Vitamin K