Intralimbic hematoma formation within an atrial septal aneurysm in a neonate with hypoplastic left heart syndrome.

Atrial septal restriction is estimated to occur in up to 22% of patients with hypoplastic left heart syndrome and is associated with poor prognosis postnatally. Atrial septal aneurysms are known to be more prevalent in patients with congenital heart disease and atrial septal restriction due to elevated atrial pressures in fetal life. We report the case of a newborn with hypoplastic left heart syndrome, restrictive interatrial communication, and atrial septal aneurysm. The latter led to formation of a large intralimbic hematoma within it, which resulted in complete obstruction of the interatrial communication after birth, which led to death. We suggest that in addition to the known associated problems encountered in patients with hypoplastic left heart syndrome and restrictive interatrial communication, aneurysmal formation of the interatrial septum should alert the fetal and postnatal echocardiographer further, and careful assessment and follow-up is recommended.