MEDTRONIC-HALL VERSUS ST. JUDE MEDICAL MECHANICAL AORTIC-VALVE - DOWNSTREAM TURBULENCES WITH RESPECT TO ROTATION IN PIGS

Background and aims of the study: Turbulences downstream of mechanical aortic valves are known to contribute to most valve-related complicat ions such as thrombosis, embolization or damage to blood components. I n vitro studies have demonstrated the impact of the orientation of pro stheses on transvalvular energy loss. This study evaluates the influen ce of valve orientation on turbulences in the supravalvular aorta in p igs. Methods: A rotation device which could carry a Medtronic Hall(MH) or St. Jude Medical (SJM) aortic valve prosthesis (23 mm) was constru cted and implanted into four healthy pigs. Turbulence measurements usi ng pulsed Doppler ultrasonography were carried out 3 cm downstream of the valve, while the prostheses were rotated in 45 degrees steps. Reyn old's normal stress values (RNS) were calculated as key markers for tu rbulent stresses. Results: Turbulences downstream of MH and SJM valves demonstrated a significant change with rotation. The MH valve showed minimum RNSmean values with orientation of the large orifice to the ri ght posterior aortic wall, which is the area of highest velocities dur ing ejection. With this orientation, aortic flow almost complied with physiologic conditions. Increase of turbulence was observed with any o ther position. The SJM valve revealed significant turbulent flow at an y orientation. Minimum RNSmean values were also measured with one orif ice facing the right posterior wall of the aorta. Conclusion: With opt imum orientation (major orifice facing the right posterior aortic wall ) the MH valve matches the aortic flow pattern to near-normal physiolo gy. The flow patterns of the SJM valve are less susceptible to rotatio n, but cannot attain the optimum RNS values of the MII prosthesis.