Increased aortic wall stress in aortic insufficiency: clinical data and computer model.

OBJECTIVE

The study was aimed at determining which cardiac pathologies are associated with increased longitudinal stress in the aorta and therefore may be responsible for the intimal transverse tears seen in aortic dissections.

METHODS

Aortic root contrast injections were analyzed in 90 cardiac patients to measure the downward motion of the annulus during a cardiac cycle. A finite element model of the pressurized aortic root, arch and supra-aortic vessels was created to assess the influence of the aortic root motion on the aortic wall stress.

RESULTS

The axial displacement of the aortic root ranged from 0 to 14 mm. A multivariate analysis showed that aortic insufficiency (AI) grade, hypokinesis of the left ventricle (HKI), and myocardial hypertrophy (HTR) were 3 independent variables which correlated with the axial displacement of the aortic root (DISP), such that ARM (mm)=5.379 (P<0.0001) +1.186 x AI grade (P=0.0016) - 1.611 x HKI (P=0.0078) - 1.399 x HTR (P=0.0355) with R2=0.23. The major finding of the stress analysis was that in the ascending aorta, at approximately 2 cm above the sino-tubular junction, the longitudinal stress due to aortic root motion was 32% higher in patients with AI than in patients without AI, thereby increasing the risk of transverse intimal rupture.

CONCLUSIONS

Cardiac patients with AI are likely to experience enhanced longitudinal stress in the ascending aorta due to increased aortic root motion. Thus, these patients should be targeted and their aortic root movement monitored because it may be an important risk factor for aortic dissection.