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The hemodynamic and the thrombogenic performance of two commercially available bileaflet mechanical heart valves (MHVs)--the ATS Open Pivot Valve (ATS) and the St. Jude Regent Valve (SJM), was compared using a state of the art computational fluid dynamics-fluid structure interaction (CFD-FSI) methodology. A transient simulation of the ATS and SJM valves was conducted in a three-dimensional model geometry of a straight conduit with sudden expansion distal the valves, including the valve housing and detailed hinge geometry. An aortic flow waveform (60 beats/min, cardiac output 4 l/min) was applied at the inlet. The FSI formulation utilized a fully implicit coupling procedure using a separate solver for the fluid problem (FLUENT) and for the structural problem. Valve leaflet excursion and pressure differences were calculated, as well as shear stress on the leaflets and accumulated shear stress on particles released during both forward and backward flow phases through the open and closed valve, respectively. In contrast to the SJM, the ATS valve opened to less than maximal opening angle. Nevertheless, maximal and mean pressure gradients and velocity patterns through the valve orifices were comparable. Platelet stress accumulation during forward flow indicated that no platelets experienced a stress accumulation higher than 35 dyne x s/cm2, the threshold for platelet activation (Hellums criterion). However, during the regurgitation flow phase, 0.81% of the platelets in the SJM valve experienced a stress accumulation higher than 35 dyne x s/cm2, compared with 0.63% for the ATS valve. The numerical results indicate that the designs of the ATS and SJM valves, which differ mostly in their hinge mechanism, lead to different potential for platelet activation, especially during the regurgitation phase. This numerical methodology can be used to assess the effects of design parameters on the flow induced thrombogenic potential of blood recirculating devices.

Aspirated blood contaminated by tissue contact is the most important activator of the coagulation system and the principal cause of hemolysis during cardiopulmonary bypass. Contact with a foreign surface is not a main variable in the procoagulant effect of bypass. Mimicking the outer cell membrane structure resulted in decreased platelet activation and decreased blood loss.

secutive neonates of less than 2,500 g underwent early surgery for congenital heart disease. A retrospective analysis was performed to evaluate the early to medium term outcome.Methods. Major cardiac surgery for congenital heart defects included a complete correction in 31 patients (group I) and a palliative procedure in 18 patients (group II). Mean age at operation was 15.2 days (1 day-90 days) and mean weight was 2,190 g (1,300 g-2,500 g). Twentyfour children (49%) were born prematurely. All neonates were critically ill and 47% were already ventilated preoperatively. Heart defects included mainly ventricular septal defect (10), tetralogy of Fallot complexes (8), aortic coarctation (8), transposition complexes (7), single ventricle anomalies (4), pulmonary atresia with intact septum (4), interrupted aortic arch (3), totally anomalous pulmonary venous return (3), and common atrioventricular septal defect (2).Results. Overall surgical mortality was 18%: 4 neonates died after definitive repair and 5 after palliation; repre-