[Giant thrombus in the left atrium after mitral bioprosthesis implantation: is standard oral anticoagulation always sufficient?].

We present a case of 70-year old male after coronary by-pass surgery and mitral bioprosthesis implantation due to infective endocarditis, with continuous atrial fibrillation, who was admitted to the hospital due to the worsening of the heart failure. He was on oral antivitamine K agents with therapeutic value of INR. On echocardiography we found enlargement of all cavities with extremely big left atrium (9.5 cm) and poor contractile left ventricular function (EF 25%). An enormously big old thrombus was found in the left atrium. The patient was disqualified from surgical treatment. Treatment with unfractionated heparin was unsuccessful. We discuss if standard antithrombotic treatment is always sufficient in such unusual cases.