Refractory left atrial mural endocarditis secondary to a mitral valve jet lesion requiring thoracotomy: a case report.

Background: Infective endocarditis (IE) lesions rarely exist only in the endocardium, except on the valves. Such lesions are usually treated with the same strategy used to treat valvular IE. Depending on the causative organisms and degree of intracardiac structure destruction, it might be cured with conservative treatment consisting of antibiotics alone. Case summary: A 38-year-old woman had a continuous high fever. Echocardiography revealed a vegetation located on the endocardial side of the posterior wall of the left atrium, from the valve ring on the side of the posteromedial scallop, which was exposed to a mitral regurgitation jet. Mural endocarditis caused by methicillin-sensitive Staphylococcus aureus (MSSA) was diagnosed based on blood cultures. Splenic infarction developed despite various types of appropriate antibiotics. The vegetations increased in size over time to >10 mm. The patient underwent surgical resection and had an uneventful post-operative course. There was no evidence of exacerbation or recurrence during the post-operative outpatient follow-up visits. Discussion: Even in cases of isolated mural endocarditis, infections caused by MSSA that are resistant to multiple antibiotics can be challenging to manage with antibiotics alone. Specifically, for cases of MSSA IE that show resistance to various antibiotics, early consideration should be given to surgical intervention as part of the treatment process.