Cardiac MRI clinches diagnosis of Libman-Sacks endocarditis

Abstract

A 28-year-old man presented to our hospital with exertional dyspnoea that had become gradually worse over the previous 3 months. On clinical examination of his heart, the apex was displaced laterally and inferiorly, the first heart sound was muffled, and there was a grade IV–VI apical pan-systolic murmur. 2 days after admission, the patient developed a non-haemorrhagic stroke. A transthoracic echocardiogram showed a dilated left ventricle with global hypokinesia and impaired systolic function: the left ventricular ejection fraction was 33% (video 1). A roughly spherical, relatively immobile mass, approximately 1·6 cm × 1·6 cm, was seen attached to the base of the posterior leaflet of the mitral valve (video 2). There was severe, eccentric, posteriorly directed mitral valve incompetence (video 1). A transoesophageal echocardiogram confirmed the transthoracic echocardiogram findings, but it did not help us understand the true nature of the mass (video 3). A three-dimensional transoesophageal echocardiogram confirmed the previous findings (appendix and video 3). All blood cultures obtained were negative. Additionally, we did a cardiac MRI to investigate the nature of the tissue or tissues of the abnormality. After confirming the location of the mass (video 3), the MRI showed an increased T2-weighted signal (figure) with an isointense T1-weighted signal. It also had an increased signal on delayed hyperenhancement (figure), with patchy myocardial fibrosis indicating myocarditis. Taken together, all these findings confirmed that the mass was not a thrombus or the vegetation of an infective endocarditis. We concluded the diagnosis was most likely to be non-infective endocarditis—commonly known as Libman-Sacks endocarditis. Laboratory investigations supported this diagnosis: a lupus anticoagulant test was positive and the levels of anticardiolipin IgM and anti-β2 glycoprotein I IgG antibodies—markers of the antiphospholipid syndrome—were increased. We started treatment with prednisone, an immunosuppressant (mycophenolate mofetil), anticoagulation, and measures to prevent cardiac failure. Pleasingly, the patient's clinical condition improved remarkably, and his left ventricular function increased with an ejection fraction of 43%; the mitral valve mass also reduced in size to 0·5 cm × 0·4 cm (figure and video 4).