Use of Tc-99m MAA in determining the etiology of increasing cyanosis following SVC-PA anastomosis for the hypoplastic left heart syndrome.

The hypoplastic left heart syndrome, which characteristically presents in the first few hours of life with cardiovascular collapse, is treated by reconstructive surgery (Norwood's procedure) beginning in the neonatal period. If untreated, more than 95% of infants with this malformation die within the first month of life. The case described involves the development of increasing cyanosis 7 weeks following bilateral superior vena caval-pulmonary artery (SVC-PA) anastomosis in an infant born with a hypoplastic left heart (including aortic and mitral valve stenosis) and an anatomic variant of bilateral superior vena cavae. The use of Tc-99m MAA proved efficacious in quantitating the differential perfusion to each lung, establishing the site of a postoperative stenosis in an anastomotic channel, and documenting systemic perfusion, thus confirming the right-to-left shunt from the superior vena cava to the systemic circulation that resulted in increasing cyanosis.