Study of the Biomechanical Properties and Microstructure of Trabecular Musculi Pectinati in the Left Atrial Appendage for patients with Atrial Fibrillation

Abstract

Aims: (1) Quantitatively characterize the Pseudo Fibrosis Burden (PFB) of Left Atrial Appendage (LAA) Trabecular Musculi Pectinati (TMP) in patients with atrial fibrillation based on histological analysis; (2) Explore the passive dynamic properties of LAA TMP based on uniaxial tensile experiments and determine the hyperelastic constitutive parameters; (3) Explore samples Effects of different storage conditions on the mechanical properties of left atrial appendage TMP. Methods: Fifty TMP were isolated from the resected LAAs of 21 patients with atrial fibrillation and stored (23 strips in the -78°C cryopreservation group and 27 strips in the 4°C normal temperature storage group). The TMP stress-strain curve was obtained through uniaxial tension. According to this curve, the elastic modulus of the low strain zone (EMLS) and the high strain zone (EMHS) were respectively defined. The correlation between the TMP’s diameter and its mechanical properties and the impact of storage temperature on TMP mechanics were analyzed. Four strain energy functions were used to fit the TMP stress-strain curve to obtain the hyperelastic model constitutive parameters. Histological analysis of the axial and transverse microstructure of TMP was performed using Verhoeff-Van Gieson double staining method of Elastic fibers and collagen fibers (EVG) and Masson staining respectively, and the Pseudo Fiber Burden (PFB) was calculated. Analyze the correlation between mechanical properties and PFB. Results: Cryopreservation reduced the elastic modulus in the hyperelastic stage of TMP mechanical properties. EMLS (r=-0.7228, P<0.0001)/EMHS (r=-0.6772, P<0.0001) showed a significantly negative correlation with TMP diameter, while PFB only showed a significantly higher positive correlation with EMHS (r=0.6646, P=0.0057). Conclusion: This study quantitatively characterized the morphological and mechanical features of TMP. The research revealed that different storage temperatures to some extent affected the mechanical properties of TMP. Moreover, there was a significant correlation between the mechanical properties of TMP and TMP diameter. This held potential significance for a deeper understanding of the mechanical aspects of TMP under atrial fibrillation conditions and for constructing atrial fibrillation simulation models of the LAA.