Thrombosis of Chiari's network in the setting of non-bacterial thrombotic endocarditis occurring under non-vitamin K antagonist oral anticoagulation: a case report.

Background: Non-bacterial thrombotic endocarditis (NBTE) is a rare condition characterized by sterile thrombi on undamaged valves. We herein report a case of NBTE involving the Chiari's network and the mitral valve, related to a metastatic cancer, and occurring under non-vitamin K antagonist oral anticoagulant (NOAC). Case summary: A 74-year-old patient with metastatic pulmonary cancer was diagnosed with a right atrium mass during pre-treatment cardiovascular check-up. Transoesophageal echocardiography and cardiac magnetic resonance concluded that the mass was a Chiari's network. Two months later, the patient was admitted for a pulmonary embolism and started rivaroxaban. At 1-month follow-up, the patient underwent a new echocardiography, which showed an increased size of the right atrium mass and the presence of two new masses on the mitral valve. She suffered an ischaemic stroke. Infectious work-up was negative. Coagulation factor VIII was 419%. A NBTE with Chiari's network thrombosis and mitral valve involvement was suspected in the setting of a hypercoagulable state related to the active cancer, and intravenous heparin was started, bridged to vitamin K antagonist (VKA) after 3 weeks. All the lesions were fully resolved on follow-up echocardiography at 6 weeks. Discussion: This case highlights an atypical association of thrombosis on right and left heart chamber with systemic and pulmonary embolism, related to a hypercoagulable state. Chiari's network is an embryonic remnant with no clinical significance and is exceptionally thrombosed. Failure of treatment by NOAC highlights the complexity of cancer-related thrombosis, particularly in NBTE, and the necessity of heparin and VKA in our case.