Atypical Cardiac Anatomy Leading to Subvalvar Aortic Stenosis in a 19-Month-Old Boy With a Murmur

A 19-month-old boy presented with a murmur and was found to have an unusual etiology of subvalvar aortic stenosis with discrete subaortic membrane and anomalous attachment of the anterior mitral valve papillary muscle to the interventricular septum. Preoperative suspicion for mitral valve involvement impacted surgical planning.