Dilatation of the pulmonary autograft after the Ross procedure can lead to aortic insufficiency and/or aneurysmal pathology requiring reoperation. Autograft remodeling occurs as the autograft wall is exposed to systemic pressure and higher wall stresses, which have not been quantified in humans. The aim of the study was to develop a realistic Finite Element (FE) model of the human pulmonary autograft and to perform simulations at systemic pressure to quantify the increases in autograft wall stress immediately after the Ross procedure. Autograft geometry was generated from high-resolution micro-computed tomography images of an explanted human pulmonary root to create a mesh of hexahedral elements. Constitutive equations were used to describe the regional tissue material properties of the human pulmonary root obtained from bi-axial stretch testing. LS-DYNA (LSTC Inc., Livermore, CA) FE software was used to simulate cardiac cycles at pulmonary and systemic pressure. Autograft dilatation and wall stress distribution were determined. Correlation of LS-DYNA model material properties to actual tissue stress-strain data was performed to ensure model accuracy. Human autograft dilation from pulmonary to systemic pressure was minimal (32.1 to 33.4mm) due to the non-linearity of the material properties. Less compliance was demonstrated at greater wall stresses. Significant increases in autograft wall stresses were found at systemic pressures. Maximal wall stresses increased approximately 10-fold in diastole (12.4 to 122.3 kPa) and 5-fold in systole (48.1 to 234.2 kPa), relative to the wall stresses at pulmonary pressures. Pulmonary autograft wall stress increased by an order of magnitude at systemic pressure. Initial autograft dilation at systemic pressure was minimal as validated by clinical studies. Chronically elevated wall stress may lead to pathologic remodeling and aneurysmal formation over time. The correspondence of this model with future studies of post-dilated autografts will lead to an improved understanding of tissue remodeling, and offer necessary data for developing improvements to the Ross procedure.


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  • Accepted: 05 June 2012
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