Mechanisms of aortic valve incompetence: Finite-element modeling of Marfansyndrome

Objectives: Progressive aortic root dilatation and an increased aortic root elastic modulus have been documented in persons with Marfan syndrome. To e xamine the effect of aortic root dilatation and increased elastic modulus o n leaflet stress, strain, and coaptation, we used a finite-element model. Methods: The normal model incorporated the geometry, tissue thickness, and anisotropic elastic moduli of normal human roots and valves. Four Marfan mo dels were evaluated, in which the diameter of the aortic root was dilated b y 5%, 15%, 30%, and 50%. Aortic root elastic modulus in the 4 Marfan models was doubled. Under diastolic pressure, regional stresses and strains were evaluated, and the percentage of leaflet coaptation was calculated. Results: Root dilatation and stiffening significantly increased regional le aflet stress and strain compared with normal levels. Stress increases range d from 80% to 360% and strain increases ranged from 60% to 200% in the 50% dilated Marfan model. Leaflet stresses and strains were disproportionately high at the attachment edge and coaptation area. Leaflet coaptation. was de creased by approximately 20% in the 50% root dilatation model. Conclusions: Increasing root dilatation and root elastic modulus to simulat e Marfan syndrome significantly increases leaflet stress and strain and red uces coaptation in an otherwise normal aortic valve. These alterations may influence the decision to use valve-sparing aortic root replacement procedu res in patients with Marfan syndrome.