Background: In the echocardiographic evaluation of coarctation of the aorta, the degree of antegrade diastolic flow (diastolic runoff) noted on spectral Doppler tracings traditionally was thought to be solely dependent on lesion severity. However, recent in vitro experiments suggest the presence of this spectral Doppler pattern is as much related to the severity of coarctation as it is with changes in aortic compliance. Using state-of-the-art, multidisciplinary, numeric analysis tools, the purpose of this study was to investigate the specific fluid and wall mechanics present in coarctation of the aorta to further understand these relationships.
Methods: Three computational numeric models of coarctation were developed with high, low, and no wall compliance. Flow simulations were run representing high- and low-flow states.
Results: In both the low- and high-flow states, the degree of diastolic runoff increased with increasing vessel compliance. The high compliance model had larger changes in aortic dilatation in the precoarctation region compared with the low compliance model.
Conclusions: Increased aortic compliance brings about greater dilatation of the precoarctation aorta in systole, resulting in a persistence of stored upstream energy. This stored energy, released downstream in diastole as the precoarctation aortic walls contract, leads to increased degrees of diastolic runoff. Numeric methods offer a unique perspective into the mechanisms behind such clinical measures.