Following a bilateral bidirectional Glenn shunt, a child had persistent hypoxemia. Agitated saline contrast injection into the jugular vein during transesophageal echocardiography displayed a rapid appearance of saline particles in the cardiac chambers suggesting the presence of pulmonary arteriovenous malformations. However, the clinical picture was not in agreement and an angiographic contrast injection during an immediate cardiac catheterization revealed the underlying pathology which was immediately corrected surgically.