Chemical treatment and tissue selection: factors that influence the mechanical behaviour of porcine pericardium

Calcification and mechanical failure are the major causes of the loss of ca rdiac bioprostheses. The chemical treatments used to stabilize the tissue e mployed are considered to play a fundamental role in the development of the se two phenomena, although the problem is multifactorial and the underlying causes are yet to be fully identified. Currently, there is an ongoing sear ch for chemical treatments capable of reducing or eliminating the process o f calcification while preserving the mechanoelastic characteristics of the tissue. One of the approaches to this effort is the elimination of the phos pholipid component from the biological tissue employed in prosthesis constr uction. There is evidence that this component may be responsible for the pr ecipitation of calcium salts. The present study compares two delipidating c hemical treatments involving chloroform/methanol and sodium dodecyl sulfate (SDS) with the use of glutaraldehyde (GA) alone. For this purpose, porcine pericardial tissue was subjected to tensile strength testing employing a h ydraulic simulator. A total of 234 samples were studied 90 treated with GA, 72 treated with chloroform/methanol and 72 treated with SDS. The mean brea king strength was significantly higher in the samples treated with GA (betw een 43.29 and 63.01 MPa) when compared with those of tissue treated with ch loroform/methanol (29.92-42.30MPa) or with SDS (13.49-19.06MPa). In a secon d phase of the study, selection criteria based on morphological and mechani cal factors were applied to the pericardial membranes employing a system of paired samples. The mathematical analysis of the findings in one fragment will aid in determining the mechanical behavior of its adjacent twin sample . In conclusion, the anticalcification chemical treatments tested in the ex perimental model conferred a lesser mechanical resistance than that obtaine d with GA. On the other hand, the utilization of paired samples was found t o be useful in the prediction of the mechanical behavior of porcine pericar dial tissue. Nevertheless, in order for our method of selection to be consi dered the most adequate approach, it will be necessary to validate these fi ndings in dynamic studies involving a real, functional model. (C) 2001 Else vier Science Ltd. All rights reserved.