Apical aortic blood pump preclinical assessment for long­term use: durability test and stator topology to reduce wear in the bearing system

This study presents an assessment for long­term use of the apical aortic blood pump (AABP), focusing on wear reduction in the bearing system. AABP is a centrifugal left ventricle assist device initially developed for bridge to transplant application. To analyze AABP performance in long­term applications, a durability test was performed. This test indicated that wear in the lower bearing pivot causes device failure in long­term. A wear test in the bearing system was conducted to demonstrate the correlation of the load in the bearing system with wear. Results from the wear test showed a direct correlation between load and wear at the lower bearing pivot. In order to reduce load, thus reducing wear, a new stator topology has been proposed. In this topology, a radial stator would replace the axial stator previously used. Another durability test with the new stator has accounted twice the time without failure when compared with the original model.

In vitro assessment of the apico aortic blood pump: anatomical positioning, hydrodynamic performance, hemolysis studies, and analysis in a hybrid cardiovascular simulator

Abstract: The Apico Aortic Blood Pump (AABP) is acentrifugal continuous flow left ventricular assist device(LVAD) with ceramic bearings. The device is in the initialdevelopment phase and is being designed to be attacheddirectly to the left ventricular apex by introducing an inletcannula. This paper reports results from in vitro experiments.In order to evaluate implantation procedures anddevice dimensioning, in vitro experiments included an anatomicpositioning study for the analysis of surgical implantationprocedure and device dimensions and positioningthat was performed using the body of a pig. The resultsrevealed no damage caused by the device, and the surgicalimplantation procedure was considered feasible. Hydrodynamicperformance curves were obtained to verify theapplicability of the device as an LVAD, showing adequateperformance. Mechanical blood trauma was analyzedthrough 6-h hemolysis tests, with total pressure head of100 mm Hg and flow of 5 L/min. Mean normalized index ofhemolysis was 0.009 g/100 L (±0.002 g/100 L).Studies usinga hybrid cardiovascular simulator were conducted for threetypes of circulatory conditions: normal healthy conditions,concentric hypertrophic heart failure (CHHF), and CHHFwith AABP assistance. Analysis of cardiovascular parametersunder those three conditions demonstrated that whenthe AABP was assisting the system, parameters underCHHF conditions went back to normal healthy values, indicatingthe AABP’s effectiveness as CHHF therapy. Ourpreliminary results indicate that it is feasible to use theAABP as a LVAD. The next steps include long-term invivo experiments.

Centrifugal blood pump for temporary ventricular assist deviceswith low priming and ceramic bearings

A new model of centrifugal blood pump for temporaryventricular assist devices has been developed andevaluated. The design of the device is based on centrifugalpumping principles and the usage of ceramic bearings,resulting in a pump with reduced priming (35 ± 2 mL) thatcan be applied for up to 30 days. Computational fluiddynamic (CFD) analysis is an efficient tool to optimizeflow path geometry, maximize hydraulic performance, andminimize shear stress, consequently decreasing hemolysis.Initial studies were conducted by analyzing flow behaviorwith different impellers, aiming to determine the bestimpeller design.After CFD studies, rapid prototyping technologywas used for production of pump prototypes withthree different impellers. In vitro experiments were performedwith those prototypes, using a mock loop systemcomposed of Tygon tubes, oxygenator, digital flow meter,pressure monitor, electronic driver, and adjustable clampfor flow control, filled with a solution (1/3 water, 1/3 glycerin,1/3 alcohol) simulating blood viscosity and density.Flow-versus-pressure curves were obtained for rotationalspeeds of 1000, 1500, 2000, 2500, and 3000 rpm.As the nextstep, the CFD analysis and hydrodynamic performanceresults will be compared with the results of flow visualizationstudies and hemolysis tests.

Study of a centrifugal blood pump in a mock loop system

Abstract: An implantable centrifugal blood pump (ICBP)is being developed to be used as a ventricular assist device(VAD) in patients with severe cardiovascular diseases.TheICBP system is composed of a centrifugal pump, a motor, acontroller, and a power supply. The electricity source providespower to the controller and to a motor that moves thepump’s rotor through magnetic coupling. The centrifugalpump is composed of four parts: external conical house,external base, impeller, and impeller base.The rotor is supportedby a pivot bearing system, and its impeller base isresponsible for sheltering four permanent magnets. Ahybrid cardiovascular simulator (HCS) was used to evaluatethe ICBP’s performance. A heart failure (HF) (whenthe heart increases beat frequency to compensate fordecrease in blood flow) was simulated in the HCS. Themain objective of this work is to analyze changes in physiologicalparameters such as cardiac output, blood pressure,and heart rate in three situations: healthy heart, HF, andHF with left circulatory assistance by ICBP. The resultsshowed that parameters such as aortic pressure and cardiacoutput affected by the HF situation returned to normalvalues when the ICBP was connected to the HCS. Inconclusion, the test results showed satisfactory performancefor the ICBP as a VAD. Key Words: Ventricularassist device—Centrifugal blood pump—Cardiovascularsimulator.

Tunelizador metálico rígido na confecção de fístulas arteriovenosas dos membros superiores / Rigid metallic tunneler for the creation of arteriovenous fistulas in the upper extremity

A qualidade de um acesso vascular condiciona os resultados clínicos dos pacientes tratados por hemodiálise. A criação de um túnel para a acomodação do conduto é uma etapa importante durante a realização do acesso. Desenvolveu-se um tunelizador metálico rígido, empregado na confecção de acessos vasculares. O aparato utilizado apresentou vantagens e segurança nas cirurgias de confecções de acessos venosos para hemodiálise dos membros superiores.

The quality of a vascular access determines clinical outcomes of patients on hemodialysis. The creation of the tunnel for conduit insertion is an important step during the access. A rigid metallic tunneler was developed and employed to create arteriovenous fistulas. The device has proven advantageous and safe in operations for the creation of venous accesses for hemodialysis in the upper extremity.

A new model of centrifugal blood pump for cardiopulmonary bypass: design improvement, performance, and hemolysis tests

A new model of blood pump for cardiopulmonary bypass (CPB) application has been developed and evaluated in our laboratories. Inside the pump housing is a spiral impeller that is conically shaped and has threads on its surface. Worm gears provide an axial motion of the blood column. Rotational motion of the conical shape generates a centrifugal pumping effect and improves pumping performance. One annular magnet with six poles is inside the impeller, providing magnetic coupling to a brushless direct current motor. In order to study the pumping performance, a mock loop system was assembled. Mock loop was composed of Tygon tubes (Saint-Gobain Corporation, Courbevoie, France), oxygenator, digital flowmeter, pressure monitor, electronic driver, and adjustable clamp for flow control. Experiments were performed on six prototypes with small differences in their design. Each prototype was tested and flow and pressure data were obtained for rotational speed of 1000, 1500, 2000, 2500, and 3000 rpm. Hemolysis was studied using pumps with different internal gap sizes (1.35, 1.45, 1.55, and 1.7 mm). Hemolysis tests simulated CPB application with flow rate of 5 L/min against total pressure head of 350 mm Hg. The results from six prototypes were satisfactory, compared to the results from the literature. However, prototype #6 showed the best results. Best hemolysis results were observed with a gap of 1.45 mm, and showed a normalized index of hemolysis of 0.013 g/100 L. When combined, axial and centrifugal pumping principles produce better hydrodynamic performance without increasing hemolysis.