Beyond Echocardiography: Multimodality Imaging of a Mitral Valve Blood Cyst in Cryptogenic Stroke

Mitral valve blood cysts are rare, benign lesions in adults. A 52-year-old female presenting with acute ischemic stroke was found on echocardiography to have a thin-walled, mobile, 1.2 × 2.4 cm cystic mass on the posterior mitral leaflet, along with hypertrophic obstructive cardiomyopathy. Although transesophageal echocardiography detected the mass, differentiating it from solid tumors or caseous calcifications remained challenging. Noncontrast cardiac magnetic resonance imaging showed that the cyst's internal signal was isointense with the left ventricular blood pool throughout the cardiac cycle. This distinct dynamic signature definitively ruled out solid neoplasms and caseous mitral annular calcification, confirming a blood-filled cavity.