The influence of chemical treatment and suture on the elastic behavior of calf pericardium utilized in the construction of cardiac bioprostheses

Poor mechanical properties of biological tissue are known to cause wear, le ading to the failure of cardiac bioprostheses made of calf pericardium. Dif ferent chemical agents such as sodium dodecyl sulfate (SDS) are presently b eing tested as possible inhibitors of the calcification process. The object ive of this report was to determine the mechanical behavior of calf pericar dium treated with SDS for 24 h and the influence of the suture on the mecha nical properties of the tissue. Forty-eight samples were tested: 24 subject ed to a standard treatment with glutaraldehyde (12 sewn with 4/0 silk sutur e thread) and 24 incubated with SDS for 24 h (12 sewn with the same suture thread). Each sutured and nonsutured sample was cut into two strips to yiel d paired samples. All were subjected to tensile stress to breaking point. T he mean stress at breaking point in the nonsutured series treated with glut araldehyde alone was 16.42 and 13.85 MPa, depending on the region of the pe ricardium, while in the sutured samples subjected to glutaraldehyde the mea n stress was 7.50 and 7.63 MPa, respectively, differences which were statis tically significant (p=0.03 and p=0.003, respectively) when the means for n onsutured samples from equivalent regions treated with glutaraldehyde were compared. The stress at breaking point was lower in the SDS-treated series, ranging between 2.60 and 3.56 MPa. The mathematical functions that govern the stress/strain or deformation were obtained. In the series of pericardiu m treated with SDS, deformations of 10% were produced with stresses of unde r 0.4 MPa, an outcome that is intolerable from the constructive point of vi ew. We established a regression model that enabled us to determine the mech anical behavior of a sutured sample by testing a contiguous piece of tissue , with a high correlation coefficient (r > 0.99). We consider this finding to be of interest in the selection of pericardium for use in the constructi on of leaflets for cardiac bioprostheses. (C) 2000 Kluwer Academic Publishe rs.