OBJECTIVES: A ventricular assist device (VAD) is an electromechanical device used to assist cardiac blood circulation, which can be employed for the treatment of end-stage heart failure and is most commonly placed in the left ventricle. Despite enhancing perfusion performance, the implantation of left ventricular assist device (LVAD) transforms the local intraventricular flow and thus may increase the risk of thrombogenesis. This study aims to investigate fluid-particle interactions and thromboembolic risk under different LVAD configurations using three-dimensional (3D) reconstruction models, focusing on the effects of outflow tract orientation and blood flow rates. METHODS: A patient-specific end-diastolic 3D reconstruction model was initially constructed in stereo lithography (STL) format using Mimics software based on CT images. Transient numerical simulations were performed to analyze fluid-particle interactions and thromboembolic risks for LVAD with varying outflow tract orientations under 2 flow rates (4 L/min and 5 L/min), using particles of uniform size (2 mm), and a blood flow rate optimization protocol was implemented for this patient. RESULTS: When the LVAD flow rate was 5 L/min, helicity and flow stagnation of the blood flow increased the particle residence time (RT) and the risk of thrombogenesis of the aortic root. The percentage of particles traveling toward the brachiocephalic trunk was up to 20.33%. When the LVAD flow rate was 4 L/min, blood turbulence in the aorta was reduced, the RT of blood particles was shortened, and then the percentage of particles traveling toward the brachiocephalic trunk decreased to 10.54%. When the LVAD blood flow rate was 5 L/min and the direction of the outflow pipe was optimal, the RT of blood particles was shortened, and then the percentage of particles traveling toward the brachiocephalic trunk decreased to 11.22%. A 18-month follow-up observation of the patient revealed that the LVAD was in good working order and the patient had no complications related to the implantation of LVAD. CONCLUSIONS Implantation of LVAD results in a higher risk of cerebral infarction; When implanting LVAD with the same outflow tract direction, optimizing flow velocity and outflow tract can reduce the risk of cerebral infarction occurrence.
Heart-Assist Devices/adverse effects* ; Humans ; Heart Failure/physiopathology* ; Blood Flow Velocity ; Thromboembolism/prevention & control* ; Models, Cardiovascular ; Heart Ventricles/physiopathology* ; Imaging, Three-Dimensional

The rotary left ventricular assist device (LVAD) has been an effective option for end-stage heart failure. However, while clinically using the LVAD, patients are often at significant risk for ventricular collapse, called suction, mainly due to higher LVAD speeds required for adequate cardiac output. Some proposed suction detection algorithms required the external implantation of sensors, which were not reliable in long-term use due to baseline drift and short lifespan. Therefore, this study presents a new suction detection system only using the LVAD intrinsic blood pump parameter (pump speed) without using any external sensor. Three feature indices are derived from the pump speed and considered as the inputs to four different classifiers to classify the pumping states as no suction or suction. The results using a combined human circulatory system and LVAD model show that the proposed method can detect ventricular suction effectively, demonstrating that it has high classification accuracy, stability, and robustness. The proposed suction detection system could be an important part in the LVAD for detecting and avoiding suction, while at the same time making the LVAD meet the cardiac output demand for the patients. It could also provide theoretical basis and technology support for designing and optimizing the control system of the LVAD.
Computer Simulation ; Heart Failure ; surgery ; Heart Ventricles ; Heart-Assist Devices ; adverse effects ; Humans ; Models, Cardiovascular ; Suction ; adverse effects

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.
Catheters ; Computer Simulation ; Equipment Design ; Heart Failure ; therapy ; Heart-Assist Devices ; adverse effects ; Hemolysis ; Humans ; Numerical Analysis, Computer-Assisted ; Thrombosis ; prevention & control ; Ventricular Dysfunction, Left ; prevention & control

This paper is aimed to study the optimal selection of structure of vaneless centrifugal blood pump. The optimal objective is determined according to requirements of clinical use. Possible schemes are generally worked out based on structural feature of vaneless centrifugal blood pump. The optimal structure is selected from possible schemes with constraints on blood perfusion and blood damage indexes. Using an optimal selection method one can find the optimum structure scheme from possible schemes effectively. The results of numerical simulation of optimal blood pump showed that the method of constraints of blood perfusion and blood damage is competent for the requirements of selection of the optimal blood pumps.
Blood Flow Velocity ; Centrifugation ; instrumentation ; Equipment Design ; Extracorporeal Circulation ; instrumentation ; Heart-Assist Devices ; adverse effects ; Hemolysis ; Hydrodynamics ; Perfusion ; Prosthesis Design

The problem of thrombus and hemolysis in blood pump has always been an important topic to study in the development of the blood pump. Numbers of research results show that it is the complicated flow and the high shear stress of the mechanical movement that result in the thrombus and hemolysis. In this study, with the cooperation of Shanghai Children's Medical Center, we have used computational fluid dynamics (CFD) commercial software FLUENT to compute and analyze the flow characteristics in a non-blade centrifugal blood pump. The results figure out that this pump has a reasonable flow distribution and the shear stress distribution is under the critical broken state of red blood cell; meanwhile, there is less thrombus and hemolysis in this pump. So it is in the foreground for clinical use.
Computer Simulation ; Heart Defects, Congenital ; therapy ; Heart-Assist Devices ; adverse effects ; Hemodynamics ; Hemolysis ; Hemorheology ; Humans ; Models, Theoretical ; Stress, Mechanical ; Thrombosis ; prevention & control

OBJECTIVETo explore the clinical application of Intra-aortic balloon pump (IABP) and centrifugal pump in low cardiac output syndrome (LCOS) after coronary artery bypass grafting (CABG).

METHODSFrom April 2000 to January 2004, 5 patients suffered serious LCOS after CABG in our department. Because maximum vasoactive agent had no significant effect, we supported these 5 patients with IABP and centrifugal pumps. The centrifugal pumps were connected with cannulas of right superior pulmonary vein and ascending aorta. The flow rate of the centrifugal pumps were increased to 3-4 L/min gradually. The dosage of vasoactive agent and flow rate of the centrifugal pumps were decreased gradually after hemodynamics stabilized.

RESULTSAll 5 patients' hemodynamics were improved significantly after the left ventricular assist by IABP and centrifugal pumps. Five patients were weaned from the centrifugal pumps after 4 to 7 days successfully. But some degree damage to blood cells and renal function were detected. Renal function of 3 patients were recovered gradually after centrifugal pumps removed and discharged successfully, One patient died of acute renal failure, 1 patient died of multiple organ failure, 5 patients need transfusion of whole blood or concentrated erythrocytes and 4 patients need transfusion of platelets.

CONCLUSIONSThere were significant improvements in hemodynamics after support with IABP and centrifugal pumps in the patients who suffered serious LCOS with less effect of maximum vasoactive agent after CABG. Some complications on blood cells and renal function should be paid more attention.

Aged ; Cardiac Output, Low ; etiology ; surgery ; Coronary Artery Bypass ; adverse effects ; Heart-Assist Devices ; Humans ; Intra-Aortic Balloon Pumping ; Male ; Middle Aged ; Retrospective Studies ; Treatment Outcome

To evaluate the effect of impeller design on pump hemolysis, five impellers with different number of vanes or different vane angles were manufactured and tested in one pump for hemolysis comparison. The impellers are made to have the same dimension and same logarithmic spiral vane from which coincide with the stream surfaces in the pump, according to the analytical and three-dimensional design method developed by the authors. Consequently, an impeller with 6 vanes and 30 degrees vane angle has the lowest hemolysis index. This result agrees with the theoretical analyses of other investigators searching optimal number of vanes and vane angle to achieve the highest efficiency of the pump.
Heart-Assist Devices ; adverse effects ; Hemolysis ; Humans ; In Vitro Techniques ; Prosthesis Design

Hemolysis caused by blood pumps is a very important characteristic. In vitro hemolysis test circuits were constructed to operate the model I centrifugal pump, the model II axial flow pump, the magnetic coupling pump and the model I & II spiral mixed pump. The output of all pumps was set at flow 5 L/min, an average pressure of 100 mmHg. Experiments were conducted for 4 hours at room temperature(25 degrees C) with 500 ml fresh anticoagulant sheep blood. Blood samples were taken for plasma free-hemoglobin measurement, and the change in temperature at the pump outlet port was measured during the experiment. Calculate the normalized index of hemolysis (NIH). The results showed that there was no relationship either between the pump rotational speed and the NIH in five types of blood pumps, or between change in temperature at the pump outlet port and NIH. The dynamic fluid field caused by pump design and structure could be the main cause of blood damage.
Animals ; Blood Flow Velocity ; Evaluation Studies as Topic ; Heart-Assist Devices ; adverse effects ; Hemolysis ; In Vitro Techniques ; Sheep ; Temperature