Development of a re-positionable aortic stent-valve: a preliminary study in swine

Placement of aortic stent-valves in the proper position is difficult due to the high velocity and oscillation of blood flow and anatomical characteristics. To address this problem, a re-positionable stent-valve was designed and examined in a preliminary animal experiment.

Protocols for this animal study were approved by the institutional Animal Care and Use Committee. An umbrella-shaped polyurethane valve was attached at the tip of newly devised re-positionable metallic stent. The prosthesis (re-positionable stent-valve) was implanted in 5 female pigs via the right carotid artery using a 10-F introducer (Group A). As a control, the stent-without-valve was implanted in 4 female pigs (Group B). Efficacy of the valve was assessed by aortography and aortic pressure measurement. Animals were sacrificed 1 hour after stent-valve implantation for macroscopic examination.

The stent-valve was successfully implanted in all pigs. In Group A, aortography showed good function of the polyurethane valve. No significant change in diastolic pressure was noted during valve testing. In Group B, aortography and aortic pressure measurement showed massive aortic regurgitation following dysfunction of the native aortic leaflets. Post-mortem examination showed small amounts of thrombus inside the polyurethane umbrella in Group A.

Placement of the re-positionable stent-valve seems feasible and effective. However, the problem of thrombus formation inside the umbrella valve should be solved in future studies.