In vitro testing of heart valve wear outside of the manufacturers laboratory--requirements and controversies.
OBJECTIVE
Currently, various national and international Standards regulate in vitro and in vivo testing as well as the clinical evaluation of heart valve prostheses. This study concentrates on a single aspect of these protocols: accelerated wear and fatigue testing.


METHODS
The differences in the above Standards were appraised and an experimental study was designed to assess the validity of Standard testing conditions with respect to in vivo relevance. An instrumented BSCC tilting disc valve was tested in two different types of fatigue testers and in a separate study in a sheep model.


RESULTS
By comparing the obtained results it could be clearly demonstrated that under the current Standard conditions (ISO, CEN, FDA) actual in vivo impact loading cannot be reproduced. Also, the two compared test devices, though operating under the same Standard conditions, generated totally different loading conditions on the test valve.


CONCLUSIONS
Based on these findings it is suggested that the actual loading conditions of each valve type should be measured either in vivo in animal models or within a circulatory mock loop which provides physiologic loading conditions, and the test conditions for accelerated wear and fatigue testing should be modified accordingly. Cavitation effects which can be assumed to be associated with high frequency wear testing is another important issue which has to be addressed in future amendments to the Test Standards.
Reul
H
H
Helmholtz-Institute for Biomedical Engineering, Aachen, Germany.
Eichler
M
M
Potthast
K
K
Schmitz
C
C
Rau
G
G
D000818:Animals; D001672:Biocompatible Materials / Q000592:standards*; D002244:Carbon / Q000592:standards; D006350:Heart Valve Prosthesis / Q000592:standards*; D006801:Humans; D066298:In Vitro Techniques; D008422:Materials Testing / Q000379:methods*; D011474:Prosthesis Design; D015203:Reproducibility of Results; D012756:Sheep; D013314:Stress, Mechanical
D001672:Biocompatible Materials; C009139:pyrolytic carbon; D002244:Carbon