Abstract

A term, healthy infant presented with respiratory distress and severe pulmonary hypertension (PH). With an unclear aetiology and the intent to decrease right ventricular afterload, pulmonary vasodilators were initiated. Follow-up imaging revealed a supravalvular mitral ring as the cause of the PH which resolved after surgical resection of the membrane. Supravalvular mitral ring is a rare left-side congenital heart disease lesion that can lead to PH usually between infancy and toddler years, but can be easily missed in the setting of a concurrent large atrial septal defect that masks the gradient across the left ventricular inflow. While bronchopulmonary dysplasia is the most common cause of PH in infancy, a thorough evaluation is critical for the diagnosis of this reversible cause of PH as a missed diagnosis may redirect care with pulmonary vasodilators in the acute setting and potentially worsen the clinical status.