Left atrial mural endocarditis secondary to mitral valve jet lesion.

A 38-year-old woman with Down syndrome and mitral valve prolapse presented with 2 weeks of fever and cough. She had presented to an outpatient clinic 1 week earlier and was prescribed empirical antibiotics for a suspected respiratory tract infection. Despite this therapy, she continued to have high spiking fevers and developed a fulminant rash, prompting emergent admission for further evaluation. She had previously been healthy without other risk factors for infective endocarditis. An IV/VI plateau–shaped holosystolic murmur was heard in the mitral area with radiation to the axilla. Laboratory studies revealed neutrophilic leukocytosis and lactic acidosis. Transthoracic echocardiography showed myxomatous morphology of the mitral valve with holosystolic prolapse of the anterior mitral leaflet (Figure, E and Movie I in the online-only Data Supplement). Color-flow Doppler showed severe eccentric mitral regurgitation with a posteriorly directed regurgitant jet (Figure, F and Movie II in the online-only Data Supplement). Jet velocities in excess of 4 m/s were measured on continuous-wave Doppler interrogation (Figure, G). Although there were no obvious vegetations on the mitral valve, a filamentous 4-cm-long oscillating mass was seen originating from free wall of the left atrium at the site of impact of the high-velocity jet (Figure, H and Movie III in the online-only Data Supplement). Transesophageal echocar-diography used to further study the intracardiac mass (Figure, I and Movie IV in the online-only Data Supplement) showed a small vegetation at the base of the anterior mitral leaflet (Figure, J and Movie V in the online-only Data Supplement). Noncontrast computed tomography of the chest and abdomen showed multiple pleura-based pulmonary nodules suspicious for septic emboli (Figure, K). Magnetic resonance imaging of the brain using T1-, T2-, and diffuse-weighted imaging sequences showed multiple lesions throughout both hemispheres of the brain and cerebellum involving predominantly the periventricular white matter and gray matter–white matter junction. Noted to be hyperintense on the T1 and T2 sequences, these lesions displayed subtle diffusion restriction on diffuse-weighted imaging, consistent with acute embolic infarcts (Figure, L). A diagnosis of left atrial mural endocarditis secondary to mitral valve jet lesion was made. The pathogenesis of the underlying mitral valve prolapse was thought to be myxoma-tous degeneration, with the abnormal substrate predisposing to concomitant native valve endocarditis. Emergent therapy was initiated with endotracheal intubation, intravenous vasopres-sors, and broad-spectrum antibiotics, including vancomycin and gentamicin. Serial blood cultures grew methicillin-sensitive Staphylococcus aureus, establishing the diagnosis of definite endocarditis by fulfilling 2 major modified Duke …