[Pulmonary Embolism Despite Rivaroxaban in an Obese Patient].

Introduction Rivaroxaban, an oral factor Xa inhibitor, is approved for therapy of venous thromboembolism. It is unclear whether the standard dose for patients with a body mass index (BMI) > 40 kg/m2 is sufficient. History The 45-year-old patient was admitted because of increasing respiratory distress. She had a history of pulmonary embolism 30 months before the admission, a factor V Leiden mutation and several hospitalisations due to dermatomycoses. The patient briefly took phenprocoumon which was changed to 20 mg rivaroxaban due to a lack of adherence. Six months before admission, the patient paused the rivaroxaban therapy because of dental surgery and suffered a recurrent pulmonary embolism. Findings and Diagnosis The patient presented with increasing difficulty of breathing, morbid obesity with a BMI of 59.3 kg/m2 and intertrigo of the lower extremities. The ECG showed a right axis deviation, a pulmonary P-wave and an incomplete right bundle branch block. Computed tomography showed pulmonary embolisms of the left lower lobe. The pulmonary artery was dilated, and the right atrium was enlarged. Venous thrombosis of the lower limb could not be certainly ruled out. The D-dimer was elevated with 5.895 mg/L (normal value up to 169 mg/L) and NT-pro-BNP was elevated at 5.580 ng/L (normal value up to 0.5 ng/L). Sixteen hours after the onset of symptoms, 22 hours after the last dose, the serum rivaroxaban level was 137 ng/ml. According to manufacturers, the therapeutic range of rivaroxaban after 2 - 4 hours is 22 - 535 ng/ml, and after 24 hours 6 - 239 ng/ml. Therapy and course After initiation of a therapy with low-molecular weight heparin and subsequent oral anticoagulation with phenprocoumon, the symptoms decreased. Conclusions It is highly probable that the pulmonary embolism occurred at a time when the rivaroxaban level was in the therapeutic range. Since there are only few data about safety and efficacy of rivaroxaban and other non-vitamin K-oral anticoagulants (NOACs) in severely obese patients, the recommendations of the "International Society for Thrombosis and Haemostasis" should be followed: Rivaroxaban and other NOACs should not be used in patients with a BMI > 40 kg/m2 or weight > 120 kg, since only few data on this patient group are available. If NOACs are necessary in these patients, serum concentrations of NOACs should be measured.