Aortic Leaflet Stresses Are Substantially Lower Using Pulmonary Visceral Pleura Than Pericardial Tissue

Ye Chen; Xiao Lu; Haoxiang Luo; Ghassan S Kassab

doi:10.3389/fbioe.2022.869095

Aortic Leaflet Stresses Are Substantially Lower Using Pulmonary Visceral Pleura Than Pericardial Tissue

Front Bioeng Biotechnol. 2022 Apr 26:10:869095. doi: 10.3389/fbioe.2022.869095. eCollection 2022.

Authors

Ye Chen¹, Xiao Lu¹, Haoxiang Luo², Ghassan S Kassab¹

Affiliations

¹ California Medical Innovations Institute, San Diego, CA, United States.
² Department of Mechanical Engineering, Vanderbilt University, Nashville, TN, United States.

Abstract

Background: Porcine heart and bovine pericardium valves, which are collagen-based with relatively little elastin, have been broadly utilized to construct bioprosthetic heart valves (BHVs). With a larger proportion of elastin, the pulmonary visceral pleura (PVP) has greater elasticity and could potentially serve as an advantageous biomaterial for the construction/repair of BHVs. The question of how the aortic valve's performance is affected by its bending rigidity has not been well studied. Methods: Based on the stress-strain relationships of the pericardium and PVP determined by planar uni-axial tests, a three-dimensional (3D) computational fluid-structure interaction (FSI) framework is employed to numerically investigate the aortic valve's performance by considering three different cases with Young's modulus as follows: $E = 375$ , $750$ , and $1500$ kPa, respectively. Results: The stroke volumes are 112, 99.6, and 91.4 ml as Young's modulus increases from 375 to 750 and 1500 kPa, respectively. Peak geometric opening area (GOA) values are 2.3, 2.2, and 2.0 cm² for $E = 375$ , 750, and 1500 kPa, respectively. The maximum value of the aortic leaflet stress is about 271 kPa for $E = 375$ kPa, and it increases to about 383 and 540 kPa for $E = 750$ and 1500 kPa in the belly region at the peak systole, while it reduces from 550 kPa to 450 and 400 kPa for $E = 375$ , 750, and 1500 kPa, respectively, at the instant of peak "water-hammer". Conclusion: A more compliant PVP aortic leaflet valve with a smaller Young's modulus, $E$ , has a higher cardiac output, larger GOA, and lower hemodynamic resistance. Most importantly, the aortic leaflet stresses are substantially lower in the belly region within the higher compliance PVP aortic valve tissue during the systole phase, even though some stress increase is also found during the fast-closing phase due to the "water-hammer" effect similar to that in the pericardial tissue. Future clinical studies will be conducted to test the hypothesis that the PVP-based valve leaflets with higher compliance will have lower fatigue or calcification rates due to the overall lower stress.

Keywords: aortic valve; cardiovascular flow; fluid–structure interaction; leaflet stresses; tissue stiffness.