Key result
The Medtronic Parallel mechanical heart valve demonstrated a Blood Damage Index for platelets around ten times higher than the St.-Jude-Medical valve in an in vitro pulse duplicator model.
Why the study?
Does the Medtronic Parallel bileaflet valve have a higher blood damage potential compared to the St. Jude Medical valve in an in vitro model?
Does the Medtronic Parallel bileaflet valve have a higher blood damage potential compared to the St. Jude Medical valve in an in vitro model?
In vitro hemodynamic analysis reveals that the Medtronic Parallel valve generates significantly higher shear stresses and platelet damage potential compared to the St. Jude Medical valve, potentially explaining its poor clinical outcomes.
Answers are grounded in this paper and cite their sources.
May help explain Medtronic Parallel valve's clinical issues; hypothesis-generating for hemocompatibility testing and design refinements.
Even nowadays, the essential problem of mechanical heart valve prostheses is the risk of thromboembolic events mainly caused by unnatural hemodynamics, e.g. just a few years ago the Medtronic Parallel (MP) showed unsatisfactory clinical results caused by thrombi. Therefore, in vitro investigations of the whole leakage jets were performed at the MP in mitral position by means of a pulse duplicator using a two channel laser Doppler anemometer. From the measured data, mean velocity profiles and the distribution of Reynolds shear stresses, as a function of the location within the jet, were calculated. From this data the potential of blood damage is evaluated computing a Blood Damage Index (BDI) of hemolysis and platelet damage. Four regurgitant free jets right above the hinges were observed during systole at the inflow side of the MP. The peak velocities at the origin of the jets were in the order of 1.6-2.1 m/s. Two jets experienced maximum turbulent shear stresses around 100 N/m2 within this area. The BDI for platelets of the MP is around ten times higher than the BDI of the St.-Jude-Medical. The study shows that besides the flow structure within the hinges of a mechanical heart valve, the whole regurgitant jet has a large blood damage potential. This potential is measurable, respectively calculable and seems to be (on account of it's support of the clinical outcome) one piece of the puzzle that explains the negative trials of the MP.
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Zimmer et al. (2000) studied Mechanical heart valve prostheses. Medtronic Parallel (MP) mechanical heart valve vs. St.-Jude-Medical mechanical heart valve was evaluated on Blood Damage Index (BDI) for platelets (10 times higher). The Medtronic Parallel mechanical heart valve demonstrated a Blood Damage Index for platelets around ten times higher than the St.-Jude-Medical valve in an in vitro pulse duplicator model.
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