ABSTRACT
An implantable axial blood pump was designed according to the circulation assist requirement of severe heart failure patients of China. The design point was chosen at 3 L/min flow rate with 100 mm Hg pressure rise when the blood pump can provide flow rates of 2-7 L/min. The blood pump with good hemolytic and anti-thrombogenic property at widely operating range was designed by developing a structure that including the spindly rotor impeller structure and the diffuser with splitter blades and cantilevered main blades. Numerical simulation and particle image velocimetry (PIV) experiment were conducted to analyze the hydraulic, flow fields and hemolytic performance of the blood pump. The results showed that the blood pump could provide flow rates of 2-7 L/min with pressure rise of 60.0-151.3 mm Hg when the blood pump rotating from 7 000 to 11 000 r/min. After adding the splitter blades, the separation flow at the suction surface of the diffuser has been reduced efficiently. The cantilever structure changed the blade gap from shroud to hub that reduced the tangential velocity from 6.2 m/s to 4.3-1.1 m/s in blade gap. Moreover, the maximum scalar shear stress of the blood pump was 897.3 Pa, and the averaged scalar shear stress was 37.7 Pa. The hemolysis index of the blood pump was 0.168% calculated with Heuser's hemolysis model. The PIV and simulated results showed the overall agreement of flow field distribution in diffuser region. The blood damage caused by higher shear stress would be reduced by adopting the spindle rotor impeller and diffuser with splitter blades and cantilevered main blades. The blood could flow smoothly through the axial blood pump with satisfactory hydraulics performance and without separation flow.
Subject(s)
Humans , China , Computer Simulation , Equipment Design , Heart Failure , Therapeutics , Heart-Assist Devices , Hemolysis , Models, CardiovascularABSTRACT
The tip structure is one of the key factors to determine the performance of left ventricular assist device (LVAD) inflow cannulas. The tip structure influences the thrombosis, hemolysis in cannula and left ventricle and suction leading to obstruction in ventricle. We designed four kinds of inflow cannulas that had different tips and built the numerical models of the four historical used inflow cannulas inserted into the apex of left ventricle. We computed the hemodynamic characteristics of inflow cannulas insertion by Fluent software. We researched the backflow, turbulent flow and pressure distribution of the four inflow cannulas. The results showed that the trumpet tipped inflow cannula had smooth flow velocity distribution without backflow or low velocity flow. The trumpet tipped inflow cannula had the best blood compatibility characteristics. The trumpet structure could prevent obstruction. The caged tipped cannula had serious turbulent flow which could possibly cause thrombosis and the low pressure near left ventricle wall and easily lead to ventricle collapse. The trumpet tipped inflow cannula has the best blood compatibility and is difficult to be obstructed. The trumpet tipped inflow cannula is fit to long-term use LVAD.
Subject(s)
Humans , Catheters , Computer Simulation , Equipment Design , Heart Failure , Therapeutics , Heart-Assist Devices , Hemolysis , Numerical Analysis, Computer-Assisted , Thrombosis , Ventricular Dysfunction, LeftABSTRACT
ObjectiveTo evaluate in vivo antithrombosis property of optimized FW-Ⅱ axial blood pump and provides evidence for future clinical use.MethodsA left ventricle-pump-descending aorta bypass model was established in five healthy sheep (60-70 kg) and the circulation of these sheep was assisted by FW-Ⅱ axial blood pump for 2 weeks.In preoperative and postoperative day 1,2,3,7,10 and 14,blood was drawn from the jugular vein to examine platelet activation and leukocyte-platelet aggregation respectively quantified with Annexin V,CD41/61 and CD14-PE by flow cytometry assays.Immediately after termination of the experiment,FW-Ⅱ axial blood pumps were explanted and each part was inspected for thrombus formation.Macroscopic and histological examinations were checked on heart,brain,kidney and spleen,respectively for thrombosis.ResultsCompared with preoperative baseline,the number of platelet activation and leukocyte-platelet aggregation reached a peak at postoperative day 2,it retained a high level within 7 days,then gradually decreased,but was still higher than preoperative level at dayl4.According to rotating speed,the number of platelet activation and platelet-leukocyte aggregation were lowest at the speed of 8000 r/min Minus thrombus were found in the front and rear hub of the pump rotor,and there was no thrombus at other components (flow straighter,impeller and pump housing).There were no ischemia and infarction evidences in macroscopic and histological examination of the heart,brain,kidney and spleen.ConclusionFW-II axial blood pump can be used to assist left ventricular circulation for 2 weeks with a satisfactory antithrombosis property.The level of platelet activation and leukocyte-platelet aggregation can be reduced to a lowest level at an optimized pump rotating speed.
ABSTRACT
Objective To evaluate the antireflux effect of hepaticoduodenostomy plus mucosal papilloplasty.Methods 16 dogs were divided into 3 groups receiving hepaticoduodenostomy plus mucosal papilloplasty (group A), cholecystojejunostomy with antireflux intussusceptive valve preformed in group B, and cholecystojejunostomy in group C, respectively. Postoperative biliary anterograde and retrograde pressure were measured. Clinically hepaticoduodenostomy plus mucosal papilloplasty was preformed in 13 patients suffering from choledochal cyst. Results The retrograde pressure in group A was significantly higher than that in group B and C (all P