Tricuspid Valve Blood Cysts Mimicking Thrombus or Vegetation on Echocardiogram in a Neonate

A 2-month-old male infant, born premature with a birth weight of 865 g, was found to have a tricuspid valve mass mimicking thrombus and vegetation by echocardiogram on the fourth day of life. The patient was treated with antibiotics and anticoagulation with no change in the size of the mass on serial follow-up echocardiography. The patient died of severe pulmonary vein stenosis and complex neurological disability. Postmortem cardiac examination revealed numerous cardiac blood cysts with two dominant ones (1.6 and 1.5 mm) on the septal leaflet of the tricuspid valve, which based on the location and position corresponded to the suspected vegetation and thrombus on imaging. Cardiac blood cysts on valve leaflets are a common incidental finding during autopsy within the first 6 months of life; however, they are rarely detected on imaging because of their minute size, often < 0.5 mm. In this case, the sizable blood cysts were thought to represent thrombus or vegetation on echocardiogram, which influenced the patient management.