Mechanical Explanation for the Hemodynamic Efficacy of Right Atrial Appendage Autografts Used in Neo-Semilunar Valve Leaflet Reconstruction.

Background: Pediatric pulmonic and aortic valve insufficiency has recently been treated with novel procedures that use autologous right atrial appendage tissue. Whether atrial tissue's tensile strength correlates with pressures it can withstand to function as a neo-semilunar valve has not been studied. We therefore studied these properties using an ex vivo porcine heart model. Methods: Aortic cusps, pulmonic cusps, and right and left atrial appendage tissues were excised from 10 porcine hearts. Native leaflets and atrial appendage samples underwent circumferential and radial stretching by a uniaxial tensile machine. Right atrial appendage tissue from 14 additional porcine hearts was used to reconstruct neo-pulmonic and neo-aortic valves that were hydrostatically pressurized until failure. Results: The modulus of elasticity was significantly greater in aortic (3.11 ± 0.53 MPa circumferential; 1.31 ± 0.29 MPa radial) and pulmonic (2.99 ± 0.46 MPa circumferential; 1.12 ± 0.24 MPa radial) cusps than in right (0.36 ± 0.06 MPa circumferential; 0.30 ± 0.04 MPa radial) and left (0.41 ± 0.07 MPa circumferential; 0.36 ± 0.06 MPa radial) atrial appendage tissues. The average hydrostatic pressure at valve failure was similar between neo-pulmonic (104.9 ± 4.9 mm Hg) and neo-aortic (102.7 ± 2.4 mm Hg) valves. Conclusions: Atrial appendage tissue's greater distensibility may allow greater leaflet coaptation and accommodate expansion over time, enhancing growth potential. However, the greater pliability may predispose to valve prolapse if too much tissue is used or in the setting of elevated diastolic pressures. Longitudinal studies are warranted to further explore the potential of atrial tissue for valve reconstructions.