Impact of aortic dimensions and pulse pressure on late aneurysm formation in operated type A aortic dissection. A magnetic resonance imaging study.

Background: Patients operated on for type A aortic dissection remain at risk of long-term aneurysm development, the main cause for late death. The aim of this study was to identify early predictors for aneurysm formation at three-years after surgery.

Methods: A study group of 70 consecutive patients (52 +/- 10 years-old, 41 male), operated on for aortic dissection with replacement of the ascending segment, was evaluated prospectively for three-years. In order to detect aneurysm formation, the dimension of residual distal aortic segments was obtained soon after surgery and then annually for three years using cardiovascular magnetic resonance.

Results: During follow-up (38 +/- 2.6 months), aneurysm was found in 25 patients (35%) involving residual segments. Larger initial dimension of segments, higher pulse pressure, lower distensibility of residual segments and the presence of a residual flap were univariately associated with aneurysm. Multivariate analysis identified the initial dimension (mm) of the descending thoracic aorta (OR 1.47, 95%CI: [1.19-1.82]) and pulse pressure (OR 1.43,95%CI: [1.10-1.86]) as independent variables for aneurysm formation. A risk score using pulse pressure and descending thoracic dimension was constructed. Patients with or=45 yielded 100% of aneurysm frequency.

Conclusions: Type A aortic dissection treated by graft interposition is associated with a high risk of aneurysm formation. Early post-operative pulse pressure and the descending thoracic aortic dimension were independent variables and seem to be the main predictors for the outcome.