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Hemodynamic Performance (hemodynamic + performance)
Selected AbstractsComputational Fluid Dynamics Analysis of Blade Tip Clearances on Hemodynamic Performance and Blood Damage in a Centrifugal Ventricular Assist DeviceARTIFICIAL ORGANS, Issue 5 2010Jingchun Wu Abstract An important challenge facing the design of turbodynamic ventricular assist devices (VADs) intended for long-term support is the optimization of the flow path geometry to maximize hydraulic performance while minimizing shear-stress-induced hemolysis and thrombosis. For unshrouded centrifugal, mixed-flow and axial-flow blood pumps, the complex flow patterns within the blade tip clearance between the lengthwise upper surface of the rotating impeller blades and the stationary pump housing have a dramatic effect on both the hydrodynamic performance and the blood damage production. Detailed computational fluid dynamics (CFD) analyses were performed in this study to investigate such flow behavior in blade tip clearance region for a centrifugal blood pump representing a scaled-up version of a prototype pediatric VAD. Nominal flow conditions were analyzed at a flow rate of 2.5 L/min and rotor speed of 3000 rpm with three blade tip clearances of 50, 100, and 200 µm. CFD simulations predicted a decrease in the averaged tip leakage flow rate and an increase in pump head and axial thrust with decreasing blade tip clearances from 200 to 50 µm. The predicted hemolysis, however, exhibited a unimodal relationship, having a minimum at 100 µm compared to 50 µm and 200 µm. Experimental data corroborate these predictions. Detailed flow patterns observed in this study revealed interesting fluid dynamic features associated with the blade tip clearances, such as the generation and dissipation of tip leakage vortex and its interaction with the primary flow in the blade-blade passages. Quantitative calculations suggested the existence of an optimal blade tip clearance by which hydraulic efficiency can be maximized and hemolysis minimized. [source] Numerical Comparative Study on the Hemodynamic Performance of a New Helical Graft With Noncircular Cross Section and SwirlGraftARTIFICIAL ORGANS, Issue 1 2010Anqiang Sun Abstract The helically distributed ribbons of thrombus, formed in the commercially available SwirlGraft (Veryan Medical, London, UK), are the result of its wall shear stress distribution, which has zonary areas of low wall shear stress. In order to overcome the inherent deficiency of the SwirlGraft, a new helical graft with a noncircular cross section was proposed and compared numerically with the SwirlGraft in terms of wall shear stress distribution, helicity of the swirling flow created, and pressure drop over the grafts. The numerical results showed that due to the modification to the geometrical configuration of the SwirlGraft, wall shear stress in the new helical graft model was enhanced, and the zones of low wall shear stress existing in the SwirlGraft were completely eliminated. The present numerical study also predicted a slightly steeper pressure drop and reduction in helicity in the new helical graft model in comparison with the SwirlGraft model. Based on the study, we believe that the new helical graft with a noncircular cross section may reduce the possibility of acute thrombus formation in the graft because the enhanced wall shear stress can impede the stay and adherence of platelets and leukocytes to the surface of the graft. [source] Early Hemodynamic Results of the Shelhigh SuperStentless Aortic BioprosthesesJOURNAL OF CARDIAC SURGERY, Issue 5 2007Paolo Cattaneo M.D. The aim of the study was to evaluate the early hemodynamic performance of the Shelhigh SuperStentless aortic valve (AV). Methods: Between July 2003 and June 2005, 35 patients (18 females; age 70.8 ± 11.7 years, range: 22-85) underwent AV replacement with the Shelhigh SuperStentless bioprostheses. Most recurrent etiology was senile degeneration in 25 (71%) patients and 24 (69%) were in New York Heart Association (NYHA) functional class III or IV. Concomitant coronary artery bypass grafting was performed in nine patients (25.7%) and mitral valve surgery in two patients (5.7%). Doppler echocardiography was performed before surgery, at six-month and one-year follow-up. Results: There were no hospital deaths and no valve-related perioperative complications. During one-year follow-up, no endocarditis or thromboembolic events were registered, no cases of structural dysfunction or valve thrombosis were noted. Mean and peak transvalvular gradients significantly decrease after AV replacement, with an evident reduction to approximately 50% of the preoperative values at six months. A 20% reduction was also observed for left ventricular mass (LVM) index at six months, with a further regression at one year. Correspondingly, significant increases in effective orifice area (EOA) and indexed EOA were determined after surgery (0.87 ± 0.14 versus 1.84 ± 0.29 cm2 and 0.54 ± 0.19 versus 1.05 ± 0.20 cm2/m2, respectively). Valve prosthesis-patient mismatch was moderate in five patients and severe in one case. Conclusions: Shelhigh SuperStentless AV provided good and encouraging hemodynamic results. Long-term follow-up is necessary to evaluate late hemodynamic performance and durability of this stentless bioprosthesis. [source] In Vivo Assessment of a New Method of Pulsatile Perfusion Based on a Centrifugal PumpARTIFICIAL ORGANS, Issue 2 2010Jesús Herreros Abstract The aim of this study was to assess platelet dysfunction and damage to organs after extracorporeal circulation using a pump based on a new method that adds a pulsatile flow to the continuous flow provided by a centrifugal pump. The continuous component of the total flow (2,3 L/min) is created by a Bio-Pump centrifugal pump, while the pulsatile component is created by the pulsating of an inner membrane pneumatically controlled by an intra-aortic counterpulsation balloon console (systolic volume of 37.5 mL in an asynchronous way with a frequency of 60 bpm). Six pigs were subjected to a partial cardiopulmonary bypass lasting 180 min and were sacrificed 60 min after extracorporeal circulation was suspended. The hematological study included the measurement of hematocrit, hemoglobin, leukocytes, and platelet function. The new pump did not significantly alter either platelet count or platelet function. In contrast, hematocrit and hemoglobin were significantly reduced during extracorporeal circulation (approximately 5% P = 0.011, and 2 g/dL P = 0.01, respectively). The leukocyte count during extracorporeal circulation showed a tendency to decrease, but this was not significant. In general, the short-term use of the new pump (4 h) did not cause any serious morphological damage to the heart, lung, kidney, or liver. The results suggest that the hemodynamic performance of the new pump is similar to a conventional centrifugal pump and could therefore be appropriate for use in extracorporeal circulation. [source] Animal Model Development for the Penn State Pediatric Ventricular Assist DeviceARTIFICIAL ORGANS, Issue 11 2009Elizabeth L. Carney Abstract:, In March 2004, the National Heart, Lung, and Blood Institute awarded five contracts to develop devices providing circulatory support for infants and small children with congenital and acquired cardiac disease. Since 2004, the team at Penn State College of Medicine has developed a pneumatically actuated ventricular assist device (VAD) with mechanical tilting disk valves. To date, hemodynamic performance, thrombogenesis, and hemolysis have been chronically evaluated in 16 animals, including 4 pygmy goats and 12 sheep. Major complications, mainly respiratory failure, have been encountered and resolved by a multi-disciplinary team. Multi-modal analgesia, appropriate antibiotic therapy, and attentive animal care have contributed to successful outcomes. Time after implant has ranged from 0 to 40 days. Most recently, a sheep implanted with Version 3 Infant VAD was electively terminated at 35 days postimplant, with no major adverse events. This report describes a successful in vivo model for evaluating a pediatric VAD. [source] The PediPump: A Versatile, Implantable Pediatric Ventricular Assist Device,Update IVARTIFICIAL ORGANS, Issue 11 2009Brian W. Duncan Abstract Cleveland Clinic's PediPump (Cleveland, OH, USA) is a ventricular assist device designed for the support of pediatric patients. The PediPump is a mixed-flow ventricular assist device with a magnetically suspended impeller measuring 10.5 mm in diameter by 64.5 mm in length. Progress and achievements for the PediPump program are considered according to the development project's three primary objectives: Basic engineering: along with size reductions, substantial design improvements have been incorporated in each design iteration including the motor, magnetic bearings, axial touch points, and heat transfer path; Anatomic modeling and device fitting studies: Techniques based on computed tomography and magnetic resonance imaging have been developed to create three-dimensional anatomic-modeling and device-fitting tools to facilitate device implantation and to assist in preoperative planning. For in vivo testing, to date, six acute (6-h duration) and nine chronic (30-day target duration) implantations have been performed in sheep; the implantation of the PediPump appears to be relatively easy with excellent hemodynamic performance and minimal hemolysis during support. Cleveland Clinic's PediPump program supported by the National Heart, Lung and Blood Institute's Pediatric Circulatory Support Program has led to the development of a pediatric ventricular assist device that has satisfactory performance in preclinical evaluation and appears to be ready to support a program of clinical testing. [source] | ||||||||||