[Nonoclusive thrombosis of mechanical mitral valve prosthesis caused by inadequate treatment of anticoagulant therapy resistance].
BACKGROUND; Oral anticoagulants have been used in the prevention of thromboembolic complications for over six decades. A rare, but possible problem in the application of these medications could be resistance to them.


METHODS
We presented a patient with nonocclusive thrombosis of the mechanical mitral prosthesis due to inadequately treated resistance to peroral anticoagulant therapy. Resistance to oral anticoagulant medications was proven by an increased dosage of warfarin up to 20 mg and, after that, acenokumarol to 15 mg over ten days which did not lead to an increase in the international normalised ratio (INR) value over 1.2. On the basis of information that she did not take food rich in vitamin K or medications which could reduce effects of oral anticoagulants, and that she did not have additional illnesses and conditions that could cause an inadequate response to anticoagulant therapy, it was circumstantially concluded that this was a hereditary form of resistance. Because of the existing mechanical prosthetics on the mitral position, low molecular heparin has been introduced into the therapy. The patient reduced it on her own initiative, leading to nonocclusive valvular thrombosis.


CONCLUSIONS
When associated complications like absolute arrhithmia does not exist, the finding of resistance to oral anticoagulant agents is an indication for the replacement of a mechanical prosthetic with a biological one which has been done in this patients.
Ivanović
Branislava
B
Klinicki centar Srbije, Institut za kardiovaskularne bolesti, Beograd, Srbija. lole@net.yu
Vujisić-Tecić
Bosiljka
B
Simić
Dragan
D
Cvetković-Matić
Danica
D
D000284:Administration, Oral; D000328:Adult; D000925:Anticoagulants / Q000008:administration & dosage*; D004351:Drug Resistance; D005260:Female; D006349:Heart Valve Diseases / Q000209:etiology* / Q000517:prevention & control; D006350:Heart Valve Prosthesis / Q000009:adverse effects*; D019918:Heart Valve Prosthesis Implantation / Q000009:adverse effects*; D006801:Humans; D055118:Medication Adherence; D008943:Mitral Valve; D013927:Thrombosis / Q000209:etiology* / Q000517:prevention & control
D000925:Anticoagulants