Evaluation of an in-vitro thrombosis assessment procedure by application to the Medtronic Parallel and St. Jude Medical valves.
OBJECTIVE
With the failure of animal trials to detect thrombosis in the Medtronic Parallel valve, interest has returned to finding a suitable in-vitro method for preclinical valve assessment. A technique has been developed that uses renneted milk to detect clotting around heart valves. The study aim was to determine whether the milk test could discern differences in clotting between the Parallel valve and the clinically successful St. Jude Medical (SJM) valve.


METHODS
The Parallel valve and the SJM valve were tested in the aortic position of a rigid model heart chamber at 2 l/min, 70 bpm pulsatile flow. Initially, the valves were run for 30 min to obtain data for localized clotting. Subsequently, the valves were run for only 5 min to obtain data for the initial stages of clotting, including clot origin.


RESULTS
Both valves clotted around their hinge regions in the 30-min tests, and this compared well with documented thrombogenic sites in vivo. The extent of clotting was similar, but clot adherence to the hinge pockets was greater on the Parallel valve than on the SJM valve. After the 5-min runs, no clot was visible on the SJM valve, but clot was consistently found in the hinge recesses of the Parallel valve, adjacent to the pivot.


CONCLUSIONS
A renneted milk test can discern differences between the clotting potentials of different heart valves. The Parallel valve clotted earlier than the SJM valve, indicating that it was more thrombogenic. Early-stage clotting was seen to occur around the pivot in the hinge pockets. The milk test has potential for contributing to in-vitro preclinical assessment techniques.
School of Engineering and Electronics, University of Edinburgh, Edinburgh, UK.
Aimee J
AJ
Martin
John R E
JR
Christy
D001021:Aortic Valve / Q000601:surgery; D020878:Device Removal; D006349:Heart Valve Diseases / Q000601:surgery; D006350:Heart Valve Prosthesis; D019918:Heart Valve Prosthesis Implantation; D006801:Humans; D008943:Mitral Valve / Q000601:surgery; D008955:Models, Cardiovascular; D011183:Postoperative Complications / Q000209:etiology; D011474:Prosthesis Design; D011475:Prosthesis Failure; D011673:Pulsatile Flow; D013927:Thrombosis / Q000209:etiology*; D013997:Time Factors