An 11-year-old boy developed an acute aortic pseudoaneurysm during bal
loon dilation of unoperated coarctation of the aorta. The pseudoaneury
sm occurred despite the fact that the balloon catheter size did not ex
ceed the diameter of the aorta at the diaphragm. Elective delayed surg
ical repair was successfully performed after 3 weeks of antihypertensi
ve treatment when serial magnetic resonance imaging had demonstrated a
reduction in the local tissue swelling.