Mitral valve infective endocarditis with spread of infection to the pulmonary valve via coronary artery pulmonary artery fistula: a case report.

Background: In cases of left-sided infective endocarditis (IE) complicated by one or more lung abscesses, close examination should be performed with the additional presence of right-sided IE in mind. Pulmonary valve IE may occur via a coronary artery pulmonary artery fistula (CAPAF) even in the absence of vegetation at the tricuspid valve.

Case presentation: A 76-year-old male was admitted to his local hospital with back pain and weight loss that had started 4 months previously. He was diagnosed with vertebral osteomyelitis, and antibiotic therapy was started. Subsequently, echocardiography revealed mobile vegetation at the mitral valve, and computed tomography (CT) showed multiple lung abscesses. The patient was then transferred to our hospital for urgent surgical intervention. Additional echocardiography revealed no visible vegetation at the tricuspid valve but did show thickening and moderate regurgitation of the pulmonary valve. These results indicated the presence of pulmonary valve IE. In addition, coronary CT angiography revealed CAPAF and intraoperative findings showed vegetation on the pulmonary valve. Therefore, mitral valve replacement (MVR), pulmonary valve replacement (RVR), and CAPAF closure were performed.

Conclusions: The present report is thought-provoking to describe the diagnosis of and surgical planning for IE. Firstly, when left-sided IE is complicated by lung abscess, a detailed evaluation of the right heart system and the potential for a left-to-right shunt should be performed, keeping in mind the possible presence of right-sided IE. Secondly, even if there is no vegetation at the tricuspid valve, there may be vegetation at the pulmonary valve, in which case an extracardiac left-to-right shunt that does not pass through the tricuspid valve may be present. CAPAF is a rare anomaly, but it causes pulmonary valve IE, which requires PVR.