[Right-sided infectious endocarditis due to methicillin-resistant Staphylococcus aureus resulting in ruptured abscess of the ventricular septum and sinus of Valsalva].

A 24-year-old woman presented with right-sided infectious endocarditis due to methicillin-resistant Staphylococcus aureus (MRSA). This is the first report of right-sided infectious endocarditis caused by MRSA in Japan. The patient was admitted to the Jichi Medical School Hospital because of fever of unknown origin and disturbance of consciousness. Several months before, she had discontinued treatment for hyperthyroidism. Antibiotics effective against MRSA, vancomycin and flomoxef, were given intravenously, but a new heart murmur was detected. Echocardiographic study revealed vegetations attached to the tricuspid valve and abscess formation on the ventricular septum. The vancomycin dosage was increased and arbekacin sulfate was also given from the sixth hospital day. However, these antibiotics had very little effect and the abscess rapidly increased in size. Color flow mapping finally demonstrated intracardiac shunt flow through the ruptured abscess of the ventricular septum and sinus of Valsalva. She died suddenly, probably from heart failure. The prognosis of infectious endocarditis due to MRSA is poor and drug therapy often fails. Thus, surgery should be considered in the early stage.