Objective-To determine late patency of the aortic false lumen and prop
ensity for aneurysm formation after repair of type A dissection. Desig
n-Retrospective follow up study. Setting-Regional cardiac surgical uni
t. Patients-28 patients after repair of type A dissection. Methods-Mag
netic resonance imaging (MRI) was performed between 6 weeks and 12 mon
ths after operation. Results-A patent distal false lumen with demonstr
able blood flow was found in 22 patients (78%). Only six patients had
complete obliteration of the false lumen by thrombus. The conduct of o
peration did not influence this. Nine patients (32%) showed aneurysmal
dilatation of the false lumen and three had a repeat operation. Concl
usions-So-called ''successful repair'' of aortic dissection does not o
bliterate the distal false lumen. MRI is a safe and effective radiolog
ical procedure for determining patency and dilatation in the false lum
en. Patients with type A dissection with blood flow in the false lumen
should be studied every 6 months to look for aneurysmal dilatation.