Publications by authors named "Aron Andrade"

33 Publications

Latin American Society for Artificial Organs, Biomaterials, and Tissue Engineering: Update 2020.

Artif Organs 2020 08;44(8):771-772

University Sao Judas Tadeu, Sao Paulo, Brazil.

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http://dx.doi.org/10.1111/aor.13767DOI Listing
August 2020

Impeller geometry definition of the transventricular assist device.

Artif Organs 2020 Aug 14;44(8):803-810. Epub 2020 May 14.

CEAC, Instituto Dante Pazzanese de Cardiologia, Sao Paulo, Brazil.

According to the World Health Organization, cardiovascular disease is the number one cause of death worldwide, except Africa, where Acquired Immune Deficiency Syndrome is the leading cause of death. In this scenario, the ventricular assist device (VAD) remains the unique alternative to extend patient life until heart transplantation. At Dante Pazzanese Institute of Cardiology, the research and development of an axial flow VAD to be fully implantable within the heart was started. This pump, denominated Transventricular Assist Device (TVAD), can be surgically implanted through a small left intercostal incision in a minimally invasive manner. The goal of this work is to analyze the impeller geometries of the TVAD, to avoid high shear stresses in the fluid and aim for the best conditions to support the circulatory system using computational fluid dynamics and in vitro tests. Different rotor geometries were selected according to the literature; based on the results, the best rotor was elected. This rotor contains a pair of spiral blades of constant and relatively high pitch, which pumps liquid at a flow rate of 3 L/min at 73 mm Hg. It is also expected that this rotor presents a moderate hemolysis since the shear rate is acceptable.
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http://dx.doi.org/10.1111/aor.13708DOI Listing
August 2020

In vitro evaluation of multi-objective physiological control of the centrifugal blood pump.

Artif Organs 2020 Aug 14;44(8):785-796. Epub 2020 Feb 14.

Department of Bioengineering, Institute Dante Pazzanese of Cardiology, Sao Paulo, Brazil.

Left ventricular assist devices (LVADs) have been used as a bridge to transplantation or as destination therapy to treat patients with heart failure (HF). The inability of control strategy to respond automatically to changes in hemodynamic conditions can impact the patients' quality of life. The developed control system/algorithm consists of a control system that harmoniously adjusts pump speed without additional sensors, considering the patient's clinical condition and his physical activity. The control system consists of three layers: (a) Actuator speed control; (b) LVAD flow control (FwC); and (c) Fuzzy control system (FzC), with the input variables: heart rate (HR), mean arterial pressure (MAP), minimum pump flow, level of physical activity (data from patient), and clinical condition (data from physician, INTERMACS profile). FzC output is the set point for the second LVAD control schemer (FwC) which in turn adjusts the speed. Pump flow, MAP, and HR are estimated from actuator drive parameters (speed and power). Evaluation of control was performed using a centrifugal blood pump in a hybrid cardiovascular simulator, where the left heart function is the mechanical model and right heart function is the computational model. The control system was able to maintain MAP and cardiac output in the physiological level, even under variation of EF. Apart from this, also the rotational pump speed is adjusted following the simulated clinical condition. No backflow from the aorta in the ventricle occurred through LVAD during tests. The control algorithm results were considered satisfactory for simulations, but it still should be confirmed during in vivo tests.
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http://dx.doi.org/10.1111/aor.13639DOI Listing
August 2020

Development of a prototype anti-pollution filter for volatile anesthetics.

Int J Artif Organs 2020 Jul 2;43(7):476-481. Epub 2020 Jan 2.

IRCCS San Raffaele Scientific Institute and Vita-Salute San Raffaele University, Milan, Italy.

Introduction: The use of volatile agents during cardiopulmonary bypass allows a "single drug anesthesia" and is associated with reduced peak postoperative troponin levels. Connecting the exhaust systems to the oxygenator's gas outlet port is mandatory and allows to prevent operating room (but not atmospheric) pollution by volatile agents. The aim of this study was to create a prototype filter for volatile agents and to test its adsorption efficacy during an ex-vivo simulated conventional cardiopulmonary bypass test.

Methods: We carried out bench tests to conceive a prototype filter that could prevent room and environment pollution without damaging membrane oxygenators. We performed the tests at the Engineering Center for Circulatory Assistance Laboratory, Dante Pazzanese Institute of Cardiology, São Paulo, Brazil. Bench tests included simulation of integral adsorption tests, filter dimensions and design, flow versus pressure curve, sizing, and tightness.

Results: Calgon AT 410 was the best kind of activated charcoal granules for adsorption of sevoflurane, isoflurane, and desflurane. Filter dimension tests showed that a chamber of 30-cm width over 10-cm diameter filled with 200 g of the Calgon AT410 granules was the minimum required to fully adsorb sevoflurane for 90 min. Adsorption tests showed that the prototype filter fully adsorbed isoflurane in 100 ± 2.3 min, sevoflurane in 95 ± 3.4 min, and desflurane in 95 ± 4.3 min.

Conclusion: The new version of our prototype filter adsorbed most of the volatile anesthetics agents during an ex-vivo simulated conventional cardiopulmonary bypass test.
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http://dx.doi.org/10.1177/0391398819895991DOI Listing
July 2020

Apical aortic blood pump preclinical assessment for long-term use: Durability test and stator topology to reduce wear in the bearing system.

Artif Organs 2020 Aug 6;44(8):779-784. Epub 2019 Nov 6.

Engineering Center for Circulatory Assistante, Institute Dante Pazzanese of Cardiology, Sao Paulo, Brazil.

This study presents an assessment for long-term 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 long-term applications, a durability test was performed. This test indicated that wear in the lower bearing pivot causes device failure in long-term. 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.
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http://dx.doi.org/10.1111/aor.13587DOI Listing
August 2020

A strategy for designing of customized electromechanical actuators of blood pumps.

Artif Organs 2020 Aug 15;44(8):797-802. Epub 2019 Sep 15.

Laboratory of Bioengineering and Biomaterials BIOENG, Department of Mechanics, Federal Institute of Technology in Sao Paulo IFSP, Sao Paulo, Brazil.

Congestive heart failure is a pathology of global incidence that affects millions of people worldwide. When the heart weakens and fails to pump blood at physiological rates commensurate with the requirements of tissues, two main alternatives are cardiac transplant and ventricular assist devices (VADs). This article presents the design strategy for development of a customized VAD electromagnetic actuator. Electromagnetic actuator is a brushless direct current motor customized to drive the pump impeller by permanent magnets located in rotor-stator coupling. In this case, ceramic pivot bearings support the VAD impeller. Electronic circuitry controls rotation switching current in stator coils. The proposed methodology consisted of analytical numerical design, tridimensional computational modeling, numerical simulations using Maxwell software, actuator prototyping, and validation in the dynamometer. The axial flow actuator was chosen by its size and high power density compared to the radial flow type. First step consisted of estimating the required torque to drive the pump. Torque was estimated at 2100 rpm and mean current of 0.5 A. Numerical analysis using finite element method mapped vectors and fields to build stator coils and actuator assemblage. After tests in the dynamometer, experimental results were compared with numerical simulation and validated the proposed model. In conclusion, the proposed methodology for designing of VAD electromechanical actuator was considered satisfactory in terms of data consistency, feasibility, and reliability.
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http://dx.doi.org/10.1111/aor.13556DOI Listing
August 2020

In Vitro Hydrodynamic Evaluation of a Scaffold for Heart Valve Tissue Engineering.

Artif Organs 2019 Feb 5;43(2):195-198. Epub 2018 Oct 5.

Department of Mechanical Engineering, University of São Paulo, Polytechnic School, São Paulo, Brazil.

Although prosthetic heart valves have saved many lives, the search for a living substitute continues with the aid of tissue engineering. Much progress has been made so far, but the translation of this technology to clinical reality remains a challenge, especially due to the structural complexity of heart valves and the harsh environment they are in. In a joint effort, researchers from Federal University of ABC and Institute Dante Pazzanese of Cardiology have conceived a new bioresorbable scaffold for heart valve tissue engineering (HVTE), whose hydrodynamic performance was first assessed and described in this work. The scaffold was studied at the mitral position of a left heart simulator from Escola Politécnica of the University of São Paulo, under 60 bpm and with no cell seeding. In this condition, two-dimensional particle image velocimetry was performed to investigate the flow during diastolic and systolic phases. The results indicate that the scaffold can withstand the required intraventricular pressures for a simulated normal physiologic condition in a bioreactor. Furthermore, the averaged (N = 150) velocity vector maps showed a smooth and well-distributed flow during diastole and qualitatively demonstrated no-significant regurgitation at systole.
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http://dx.doi.org/10.1111/aor.13293DOI Listing
February 2019

Comparative study of aligned and nonaligned poly(ε-caprolactone) fibrous scaffolds prepared by solution blow spinning.

J Biomed Mater Res B Appl Biomater 2019 07 28;107(5):1462-1470. Epub 2018 Sep 28.

Universidade Federal do ABC, São Bernardo do Campo, São Paulo, Brazil.

Fibrous scaffolds have become popular in tissue engineering (TE) due to their morphological resemblance to extracellular matrix components. While electrospinning is the most common technique in the field, solution blow spinning is an emerging technique with great potential. One of its many advantages is that it can produce aligned fibers with a very simple experimental setup. This work aimed to fabricate poly(ε-caprolactone) mats with aligned fibers and compare them to nonaligned ones. For that, samples were produced using three rotational speeds of a cylindrical collector and characterized in terms of fiber alignment and diameter, mechanical properties, wettability, and biological response. Results showed that with a static collector, fibers were randomly deposited and nonaligned. As the speed was increased, the fibers began to align (as proven by image analysis), resulting in a change in mechanical behavior, but no differences in fiber diameter. Cells cultured on aligned samples were more elongated, and a higher alignment degree seemed to favor cellular growth. The results confirmed the potential of this up-and-coming technique to produce aligned fibers for TE. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 1462-1470, 2019.
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http://dx.doi.org/10.1002/jbm.b.34238DOI Listing
July 2019

Clinical evaluation of the Spiral Pump® after improvements to the original project in patients submitted to cardiac surgeries with cardiopulmonary bypass.

Rev Bras Cir Cardiovasc 2014 Jul-Sep;29(3):330-7

Instituto Dante Pazzanese de Cardiologia (IDPC), São Paulo, SP, Brazil.

Objective: The objective of this paper is to present the results from Spiral Pump clinical trial after design modifications performed at its previous project. This pump applies axial end centrifugal hydraulic effects for blood pumping during cardiopulmonary bypass for patients under cardiac surgery.

Methods: This study was performed in 52 patients (51% males), between 20 to 80 (67±14.4) years old weighing 53 to 102 (71.7±12.6) kg, mostly under myocardial revascularization surgery (34.6%) and valvular surgery (32.8%). Besides the routine evaluation of the data observed in these cases, we monitored pump rotational speed, blood flow, cardiopulmonary bypass duration, urine free hemoglobin for blood cell trauma analysis (+ to 4+), lactate desidrogenase (UI/L), fibrinogen level (mg/dL) and platelet count (nº/mm3).

Results: Besides maintaining appropriate blood pressure and metabolic parameters it was also observed that the Free Hemoglobin levels remained normal, with a slight increase after 90 minutes of cardiopulmonary bypass. The Lactate Dehydrogenase showed an increase, with medians varying between 550-770 IU/L, whereas the decrease in Fibrinogen showed medians of 130-100 mg/dl. The number of platelets showed a slight decrease with the medians ranging from 240,000 to 200,000/mm3. No difficulty was observed during perfusion terminations, nor were there any immediate deaths, and all patients except one, were discharged in good condition.

Conclusion: The Spiral Pump, as blood propeller during cardiopulmonary bypass, demonstrated to be reliable and safe, comprising in a good option as original and national product for this kind of application.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4412321PMC
http://dx.doi.org/10.5935/1678-9741.20140095DOI Listing
May 2015

In vivo evaluation of centrifugal blood pump for cardiopulmonary bypass-Spiral Pump.

Artif Organs 2013 Nov;37(11):954-7

Adib Jatene Foundation, Sao Paulo, São Paulo, Brazil.

The Spiral Pump (SP), a centrifugal blood pump for cardiopulmonary bypass (CPB), has been developed at the Dante Pazzanese Institute of Cardiology/Adib Jatene Foundation laboratories, with support from Sintegra Company (Pompeia, Brazil). The SP is a disposable pump with an internal rotor-a conically shaped fuse with double entrance threads. This rotor is supported by two ball bearings, attached to a stainless steel shaft fixed to the housing base. Worm gears provide axial motion to the blood column, and the rotational motion of the conically shaped impeller generates a centrifugal pumping effect, improving pump efficiency without increasing hemolysis. In vitro tests were performed to evaluate the SP's hydrodynamic performance, and in vivo experiments were performed to evaluate hemodynamic impact during usual CPB. A commercially available centrifugal blood pump was used as reference. In vivo experiments were conducted in six male pigs weighing between 60 and 90 kg, placed on CPB for 6 h each. Blood samples were collected just before CPB (T0) and after every hour of CPB (T1-T6) for hemolysis determination and laboratory tests (hematological and biochemical). Values of blood pressure, mean flow, pump rotational speed, and corporeal temperature were recorded. Also, ergonomic conditions were recorded: presence of noise, difficulty in removing air bubbles, trouble in installing the pump in the drive module (console), and difficulties in mounting the CPB circuit. Comparing the laboratory and hemolysis results for the SP with those of the reference pump, we can conclude that there is no significant difference between the two devices. In addition, reports made by medical staff and perfusionists described a close similarity between the two devices. During in vivo experiments, the SP maintained blood flow and pressure at physiological levels, consistent with those applied in cardiac surgery with CPB, without presenting any malfunction. Also, the SP needed lower rotational speed to obtain average blood flow and pressure, compared with the reference pump.
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http://dx.doi.org/10.1111/aor.12230DOI Listing
November 2013

In vitro assessment of the Apico Aortic Blood Pump: anatomical positioning, hydrodynamic performance, hemolysis studies, and analysis in a hybrid cardiovascular simulator.

Artif Organs 2013 Nov;37(11):950-3

Department of Bioengineering, Engineering Center for Cardiac Assistance, Dante Pazzanese Institute of Cardiology, São Paulo, Brazil; Faculty of Mechanical Engineering, Department of Materials, State University of Campinas, Campinas, São Paulo, Brazil.

The Apico Aortic Blood Pump (AABP) is a centrifugal continuous flow left ventricular assist device (LVAD) with ceramic bearings. The device is in the initial development phase and is being designed to be attached directly to the left ventricular apex by introducing an inlet cannula. This paper reports results from in vitro experiments. In order to evaluate implantation procedures and device dimensioning, in vitro experiments included an anatomic positioning study for the analysis of surgical implantation procedure and device dimensions and positioning that was performed using the body of a pig. The results revealed no damage caused by the device, and the surgical implantation procedure was considered feasible. Hydrodynamic performance curves were obtained to verify the applicability of the device as an LVAD, showing adequate performance. Mechanical blood trauma was analyzed through 6-h hemolysis tests, with total pressure head of 100 mm Hg and flow of 5 L/min. Mean normalized index of hemolysis was 0.009 g/100 L (±0.002 g/100 L). Studies using a hybrid cardiovascular simulator were conducted for three types of circulatory conditions: normal healthy conditions, concentric hypertrophic heart failure (CHHF), and CHHF with AABP assistance. Analysis of cardiovascular parameters under those three conditions demonstrated that when the AABP was assisting the system, parameters under CHHF conditions went back to normal healthy values, indicating the AABP's effectiveness as CHHF therapy. Our preliminary results indicate that it is feasible to use the AABP as a LVAD. The next steps include long-term in vivo experiments.
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http://dx.doi.org/10.1111/aor.12229DOI Listing
November 2013

Study of a centrifugal blood pump in a mock loop system.

Artif Organs 2013 Nov 15;37(11):946-9. Epub 2013 Nov 15.

Dante Pazzanese Institute of Cardiology, São Paulo, São Paulo, Brazil.

An implantable centrifugal blood pump (ICBP) is being developed to be used as a ventricular assist device (VAD) in patients with severe cardiovascular diseases. The ICBP system is composed of a centrifugal pump, a motor, a controller, and a power supply. The electricity source provides power to the controller and to a motor that moves the pump's rotor through magnetic coupling. The centrifugal pump is composed of four parts: external conical house, external base, impeller, and impeller base. The rotor is supported by a pivot bearing system, and its impeller base is responsible for sheltering four permanent magnets. A hybrid cardiovascular simulator (HCS) was used to evaluate the ICBP's performance. A heart failure (HF) (when the heart increases beat frequency to compensate for decrease in blood flow) was simulated in the HCS. The main objective of this work is to analyze changes in physiological parameters such as cardiac output, blood pressure, and heart rate in three situations: healthy heart, HF, and HF with left circulatory assistance by ICBP. The results showed that parameters such as aortic pressure and cardiac output affected by the HF situation returned to normal values when the ICBP was connected to the HCS. In conclusion, the test results showed satisfactory performance for the ICBP as a VAD.
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http://dx.doi.org/10.1111/aor.12228DOI Listing
November 2013

A system to help physicians with fracture detection in stents.

Artif Organs 2013 Nov 13;37(11):973-7. Epub 2013 Nov 13.

Dante Pazzanese Institute of Cardiology, São Paulo, São Paulo, Brazil; Fundação Educacional Inaciana, São Paulo, São Paulo, Brazil; São Judas University, São Paulo, São Paulo, Brazil.

Fractures in stents are usually detected by visual analysis, which may be affected by the presence of noise and image deformations. The lack of research into automating stent fracture detection has motivated this work, in which techniques are developed to facilitate diagnosis by observation (Image Delineation Algorithm) and, when possible, to point out areas of possible fractures (Fracture Detection Algorithm). The use of classical elements and the development of additional computational techniques contributed to the process of image analysis, providing a possible way to aid medical diagnosis. The developed algorithms are applied to image samples from femoropopliteal arteries, and the results are compared to those of medical diagnosis. As a result, aside from the improvement of image display, a kappa concordance index of 0.878 for the detection of fractures confirms the method as satisfactory, with very good agreement with medical diagnosis.
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http://dx.doi.org/10.1111/aor.12237DOI Listing
November 2013

Centrifugal blood pump for temporary ventricular assist devices with low priming and ceramic bearings.

Artif Organs 2013 Nov 13;37(11):942-5. Epub 2013 Nov 13.

Dante Pazzanese Institute of Cardiology, São Paulo, São Paulo, Brazil.

A new model of centrifugal blood pump for temporary ventricular assist devices has been developed and evaluated. The design of the device is based on centrifugal pumping principles and the usage of ceramic bearings, resulting in a pump with reduced priming (35 ± 2 mL) that can be applied for up to 30 days. Computational fluid dynamic (CFD) analysis is an efficient tool to optimize flow path geometry, maximize hydraulic performance, and minimize shear stress, consequently decreasing hemolysis. Initial studies were conducted by analyzing flow behavior with different impellers, aiming to determine the best impeller design. After CFD studies, rapid prototyping technology was used for production of pump prototypes with three different impellers. In vitro experiments were performed with those prototypes, using a mock loop system composed of Tygon tubes, oxygenator, digital flow meter, pressure monitor, electronic driver, and adjustable clamp for 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 rotational speeds of 1000, 1500, 2000, 2500, and 3000 rpm. As the next step, the CFD analysis and hydrodynamic performance results will be compared with the results of flow visualization studies and hemolysis tests.
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http://dx.doi.org/10.1111/aor.12231DOI Listing
November 2013

Experimental study of pulsatile implantable electromechanical artificial ventricle.

Rev Bras Cir Cardiovasc 2011 Jan-Mar;26(1):76-85

University of Sao Paulo Medical School (FMUSP).

Objective: The objective is to present the results of the application this device in experimental animals unloading only the left ventricle.

Methods: Between June 2002 and October 2009, were implanted in 27 calfs with age between 2½ to 4 months and 80 to 100 kg of weight, with general anaesthesia and controled ventilation, by mean of left thoracotomy a cannula in the apex of VE and a lateral anastomose of a GTFE vascular graft tube in the descending portion of the thoracic aorta, both connected to the device implanted below the diaphragm in the subcutaneous (24) and intrathoracic (three). The cardiopulmonary bypass (BP) was used in five calves, and directly introduce the outflow cannula in 22.

Results: During the implant two and in the first hours of the post operative period (PO) three deaths were observed, one related to the device. The survival between the first and the six PO day was found in 17 calves and between day 8 and day 31 (PO) in five all caused by clinical/surgical problems, and related to the device. The hemodynamic impact by the systemic pressure analysis showed 20 to 40 mmHg increase and the laboratory parameters showed lower levels of traumatic impact to the blood and a good biocompatibility.

Conclusions: This kind of research is arduous and complex where at each experiment many problems are indentified in the implantability and in the device, which are sistematic correct, to became device/procedure safe and effective.
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http://dx.doi.org/10.1590/s0102-76382011000100015DOI Listing
December 2011

Introductory tests to in vivo evaluation: magnetic coupling influence in motor controller.

ASAIO J 2011 Sep-Oct;57(5):462-5

Institute Dante Pazzanese of Cardiology, Sao Paulo, Brazil; †Unicamp, Sao Paulo, Brazil.

An implantable centrifugal blood pump has been developed with original features for a ventricle assist device (VAD). This pump is part of a multicenter and international study with objective to offer simple, affordable, and reliable devices to developing countries. Previous computational fluid dynamics investigations were performed followed by prototyping and in vitro tests. Also, previous blood tests for assessment of hemolysis showed mean normalized index of hemolysis (NIH) results of 0.0054 ± 2.46 × 10⁻³ mg/100 L (at 5 L/min and 100 mm Hg). To precede in vivo evaluation, measurements of magnetic coupling interference and enhancements of actuator control were necessary. Methodology was based on the study of two different work situations (1 and 2) studied with two different types of motors (A and B). Situation 1 is when the rotor of pump is closest to the motor and situation 2 its opposite. Torque and mechanical power were collected with a dynamometer (80 g/cm) and then plotted and compared for two situations and both motors. The results showed that motor A has better mechanical behavior and less influence of coupling. Results for situation 1 showed that it is more often under magnetic coupling influence than situation 2. The studies lead to the conclusion that motor A is the best option for in vivo studies as it has less influence of magnetic coupling in both situations.
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http://dx.doi.org/10.1097/MAT.0b013e31823005dcDOI Listing
January 2012

Specification of supervisory control systems for ventricular assist devices.

Artif Organs 2011 May;35(5):465-70

Department of Mechatronics and Mechanical Systems Engineering, Escola Politécnica da USP, São Paulo, Brazil.

One of the most important recent improvements in cardiology is the use of ventricular assist devices (VADs) to help patients with severe heart diseases, especially when they are indicated to heart transplantation. The Institute Dante Pazzanese of Cardiology has been developing an implantable centrifugal blood pump that will be able to help a sick human heart to keep blood flow and pressure at physiological levels. This device will be used as a totally or partially implantable VAD. Therefore, an improvement on device performance is important for the betterment of the level of interaction with patient's behavior or conditions. But some failures may occur if the device's pumping control does not follow the changes in patient's behavior or conditions. The VAD control system must consider tolerance to faults and have a dynamic adaptation according to patient's cardiovascular system changes, and also must attend to changes in patient conditions, behavior, or comportments. This work proposes an application of the mechatronic approach to this class of devices based on advanced techniques for control, instrumentation, and automation to define a method for developing a hierarchical supervisory control system that is able to perform VAD control dynamically, automatically, and securely. For this methodology, we used concepts based on Bayesian network for patients' diagnoses, Petri nets to generate a VAD control algorithm, and Safety Instrumented Systems to ensure VAD system security. Applying these concepts, a VAD control system is being built for method effectiveness confirmation.
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http://dx.doi.org/10.1111/j.1525-1594.2011.01267.xDOI Listing
May 2011

Cardiovascular simulator improvement: pressure versus volume loop assessment.

Artif Organs 2011 May;35(5):454-8

Department of Bioengineering, Institute Dante Pazzanese of Cardiology, São Paulo, Brazil.

This article presents improvement on a physical cardiovascular simulator (PCS) system. Intraventricular pressure versus intraventricular volume (PxV) loop was obtained to evaluate performance of a pulsatile chamber mimicking the human left ventricle. PxV loop shows heart contractility and is normally used to evaluate heart performance. In many heart diseases, the stroke volume decreases because of low heart contractility. This pathological situation must be simulated by the PCS in order to evaluate the assistance provided by a ventricular assist device (VAD). The PCS system is automatically controlled by a computer and is an auxiliary tool for VAD control strategies development. This PCS system is according to a Windkessel model where lumped parameters are used for cardiovascular system analysis. Peripheral resistance, arteries compliance, and fluid inertance are simulated. The simulator has an actuator with a roller screw and brushless direct current motor, and the stroke volume is regulated by the actuator displacement. Internal pressure and volume measurements are monitored to obtain the PxV loop. Left chamber internal pressure is directly obtained by pressure transducer; however, internal volume has been obtained indirectly by using a linear variable differential transformer, which senses the diaphragm displacement. Correlations between the internal volume and diaphragm position are made. LabVIEW integrates these signals and shows the pressure versus internal volume loop. The results that have been obtained from the PCS system show PxV loops at different ventricle elastances, making possible the simulation of pathological situations. A preliminary test with a pulsatile VAD attached to PCS system was made.
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http://dx.doi.org/10.1111/j.1525-1594.2011.01266.xDOI Listing
May 2011

Single axis controlled hybrid magnetic bearing for left ventricular assist device: hybrid core and closed magnetic circuit.

Artif Organs 2011 May;35(5):448-53

Department of Exact Sciences and Earth, Federal University of São Paulo, Rua Prof. Artur Riedel 275, Diadema CEP 09972-270, SP, Brazil.

In previous studies, we presented main strategies for suspending the rotor of a mixed-flow type (centrifugal and axial) ventricular assist device (VAD), originally presented by the Institute Dante Pazzanese of Cardiology (IDPC), Brazil. Magnetic suspension is achieved by the use of a magnetic bearing architecture in which the active control is executed in only one degree of freedom, in the axial direction of the rotor. Remaining degrees of freedom, excepting the rotation, are restricted only by the attraction force between pairs of permanent magnets. This study is part of a joint project in development by IDPC and Escola Politecnica of São Paulo University, Brazil. This article shows advances in that project, presenting two promising solutions for magnetic bearings. One solution uses hybrid cores as electromagnetic actuators, that is, cores that combine iron and permanent magnets. The other solution uses actuators, also of hybrid type, but with the magnetic circuit closed by an iron core. After preliminary analysis, a pump prototype has been developed for each solution and has been tested. For each prototype, a brushless DC motor has been developed as the rotor driver. Each solution was evaluated by in vitro experiments and guidelines are extracted for future improvements. Tests have shown good results and demonstrated that one solution is not isolated from the other. One complements the other for the development of a single-axis-controlled, hybrid-type magnetic bearing for a mixed-flow type VAD.
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http://dx.doi.org/10.1111/j.1525-1594.2011.01265.xDOI Listing
May 2011

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

Artif Organs 2011 May;35(5):443-7

Institute "Dante Pazzanese" of Cardiology University of Campinas, Campinas, São Paulo UNIPAC Division, Pompéia, Brazil.

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.
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http://dx.doi.org/10.1111/j.1525-1594.2011.01254.xDOI Listing
May 2011

Implantable centrifugal blood pump with dual impeller and double pivot bearing system: electromechanical actuator, prototyping, and anatomical studies.

Artif Organs 2011 May;35(5):437-42

Center for Engineering in Cardiac Assistance, CEAC, Institute Dante Pazzanese of Cardiology, Campinas State University, São Paulo, Brazil.

An implantable centrifugal blood pump has been developed with original features for a left ventricular assist device. This pump is part of a multicenter and international study with the objective to offer simple, affordable, and reliable devices to developing countries. Previous computational fluid dynamics investigations and wear evaluation in bearing system were performed followed by prototyping and in vitro tests. In addition, previous blood tests for assessment of normalized index of hemolysis show results of 0.0054±2.46 × 10⁻³ mg/100 L. An electromechanical actuator was tested in order to define the best motor topology and controller configuration. Three different topologies of brushless direct current motor (BLDCM) were analyzed. An electronic driver was tested in different situations, and the BLDCM had its mechanical properties tested in a dynamometer. Prior to evaluation of performance during in vivo animal studies, anatomical studies were necessary to achieve the best configuration and cannulation for left ventricular assistance. The results were considered satisfactory, and the next step is to test the performance of the device in vivo.
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http://dx.doi.org/10.1111/j.1525-1594.2011.01260.xDOI Listing
May 2011

Mock circulatory system for the evaluation of left ventricular assist devices, endoluminal prostheses, and vascular diseases.

Artif Organs 2008 Jun 16;32(6):461-7. Epub 2008 Apr 16.

Institute Dante Pazzanese of Cardiology, Escola Politécnica, University of São Paulo, Brazil.

A new digital computer mock circulatory system has been developed in order to replicate the physiologic and pathophysiologic characteristics of the human cardiovascular system. The computer performs the acquisition of pressure, flow, and temperature in an open loop system. A computer program has been developed in Labview programming environment to evaluate all these physical parameters. The acquisition system was composed of pressure, flow, and temperature sensors and also signal conditioning modules. In this study, some results of flow, cardiac frequencies, pressures, and temperature were evaluated according to physiologic ventricular states. The results were compared with literature data. In further works, performance investigations will be conducted on a ventricular assist device and endoprosthesis. Also, this device should allow for evaluation of several kinds of vascular diseases.
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http://dx.doi.org/10.1111/j.1525-1594.2008.00569.xDOI Listing
June 2008

A new technique to control brushless motor for blood pump application.

Artif Organs 2008 Apr;32(4):355-9

Department of Bioengineering, Institute Dante Pazzanese of Cardiology, São Paulo, Brazil.

This article presents a back-electromotive force (BEMF)-based technique of detection for sensorless brushless direct current motor (BLDCM) drivers. The BLDCM has been chosen as the energy converter in rotary or pulsatile blood pumps that use electrical motors for pumping. However, in order to operate properly, the BLDCM driver needs to know the shaft position. Usually, that information is obtained through a set of Hall sensors assembled close to the rotor and connected to the electronic controller by wires. Sometimes, a large distance between the motor and controller makes the system susceptible to interference on the sensor signal because of winding current switching. Thus, the goal of the sensorless technique presented in this study is to avoid this problem. First, the operation of BLDCM was evaluated on the electronic simulator PSpice. Then, a BEMF detector circuitry was assembled in our laboratories. For the tests, a sensor-dependent system was assembled where the direct comparison between the Hall sensors signals and the detected signals was performed. The obtained results showed that the output sensorless detector signals are very similar to the Hall signals at speeds of more than 2500 rpm. Therefore, the sensorless technique is recommended as a responsible or redundant system to be used in rotary blood pumps.
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http://dx.doi.org/10.1111/j.1525-1594.2008.00554.xDOI Listing
April 2008

An electro-fluid-dynamic simulator for the cardiovascular system.

Artif Organs 2008 Apr;32(4):349-54

University Sao Judas Tadeu, São Paulo, SP, Brazil.

This work presents the initial studies and the proposal for a cardiovascular system electro-fluid-dynamic simulator to be applied in the development of left ventricular assist devices (LVADs). The simulator, which is being developed at University Sao Judas Tadeu and at Institute Dante Pazzanese of Cardiology, is composed of three modules: (i) an electrical analog model of the cardiovascular system operating in the PSpice electrical simulator environment; (ii) an electronic controller, based on laboratory virtual instrumentation engineering workbench (LabVIEW) acquisition and control tool, which will act over the physical simulator; and (iii) the physical simulator: a fluid-dynamic equipment composed of pneumatic actuators and compliance tubes for the simulation of active cardiac chambers and big vessels. The physical simulator (iii) is based on results obtained from the electrical analog model (i) and physiological parameters.
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http://dx.doi.org/10.1111/j.1525-1594.2008.00553.xDOI Listing
April 2008

Computational fluid dynamics investigation of a centrifugal blood pump.

Artif Organs 2008 Apr;32(4):342-8

Institute Dante Pazzanese of Cardiology, Escola Politécnica, University of São Paulo, São Paulo, SP, Brazil.

In the development of a ventricular assist device, computational fluid dynamics (CFD) analysis is an efficient tool to obtain the best design before making the final prototype. In this study, different designs of a centrifugal blood pump were developed to investigate flow characteristics and performance. This study assumed the blood flow as being an incompressible homogeneous Newtonian fluid. A constant velocity was applied at the inlet; no slip boundary conditions were applied at device wall; and pressure boundary conditions were applied at the outlet. The CFD code used in this work was based on the finite volume method. In the future, the results of CFD analysis can be compared with flow visualization and hemolysis tests.
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http://dx.doi.org/10.1111/j.1525-1594.2008.00552.xDOI Listing
April 2008

Magnetic suspension of the rotor of a ventricular assist device of mixed flow type.

Artif Organs 2008 Apr;32(4):334-41

Department of Mechatronics Engineering, Escola Politécnica of São Paulo University, EPUSP-PMR, São Paulo, Brazil.

This work presents results of preliminary studies concerning application of magnetic bearing in a ventricular assist device (VAD) being developed by Dante Pazzanese Institute of Cardiology-IDPC (São Paulo, Brazil). The VAD-IDPC has a novel architecture that distinguishes from other known VADs. In this, the rotor has a conical geometry with spiral impellers, showing characteristics that are intermediate between a centrifugal VAD and an axial VAD. The effectiveness of this new type of blood pumping principle was showed by tests and by using it in heart surgery for external blood circulation. However, the developed VAD uses a combination of ball bearings and mechanical seals, limiting the life for some 10 h, making impossible its long-term use or its use as an implantable VAD. As a part of development of an implantable VAD, this work aims at the replacement of ball bearings by a magnetic bearing. The most important magnetic bearing principles are studied and the magnetic bearing developed by Escola Politécnica of São Paulo University (EPUSP-MB) is elected because of its very simple architecture. Besides presenting the principle of the EPUSP-MB, this work presents one possible alternative for applying the EPUSP-MB in the IDPC-VAD.
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http://dx.doi.org/10.1111/j.1525-1594.2008.00551.xDOI Listing
April 2008

New centrifugal blood pump with dual impeller and double pivot bearing system: wear evaluation in bearing system, performance tests, and preliminary hemolysis tests.

Artif Organs 2008 Apr;32(4):329-33

Department of Bioengineering, Institute Dante Pazzanese of Cardiology, IDPC, Sao Paulo, Brazil.

A new dual impeller centrifugal blood pump has been developed as a research collaboration between Baylor College of Medicine and Institute Dante Pazzanese of Cardiology for long-term left ventricle assist device (LVAD). A design feature of this new pump is a dual impeller that aims to minimize a stagnant flow pattern around the inlet port. Several different materials were tested in order to adopt a double pivot bearing design originally developed by Prof. Dr. Yukihiko Nosé from Baylor College of Medicine. Hydraulic performance tests were conducted with two different inlet ports' angle configurations 30 degrees and 45 degrees . Pump with inlet port angle of 45 degrees achieved best values of pressure ahead and flow after 1800 rpm. Preliminary hemolysis tests were conducted using human blood. The pump showed good performance results and no alarming trace of hemolysis, proving to be a feasible long-term LVAD.
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http://dx.doi.org/10.1111/j.1525-1594.2008.00550.xDOI Listing
April 2008

Spiral blood pump: conception, development and clinical application of the original project.

Rev Bras Cir Cardiovasc 2007 Apr-Jun;22(2):224-34

Bioengineering and Surgical, Division of Instituto Dante Pazzanese de Cardiologia, São Paulo, Brazil (IDPC/SP).

Introduction: This paper addresses an original project that encompasses the conception, development and clinical application of a helical bypass pump called the Spiral Pump, that uses the association of centrifugal and axial propulsion forces based de the Archimedes principle. This project has obtained a Brazilian Patent and an International Preliminary Report, defining it as an invention.

Methods: The aim of this work was to evaluate the hemodynamic capacity and the impact of its application on blood cells by means of experimental in vitro tests, including hydrodynamic efficiency, effect on hemolysis and flow visualization. Moreover, in vivo experimental tests were carried out on lambs that were submitted to cardiopulmonary bypass for six hours and in 43 patients submitted to heart bypass surgery using the Spiral Pump.

Results: When the rotor-plastic casing gap was 1.5mm, the flow generated was nearly 9 L/min, the pressure was greater than 400 mmHg at 1500 rpm, and the normalized hemolytic indexes were not greater than 0.0375 g/100L in high-flow and pressure conditions. Additionally, by the flow visualization techniques, stagnation was not seen inside the pump nor was turbulence identified at the entrance or exit of the pump, or at the ends of the spindles. In the in vivo tests using cardiopulmonary bypasses for 6 hours in lambs, the pump maintained adequate pressure rates and the free hemoglobin levels ranged between 16.36 mg% and 44.90 mg%. Evaluating the results of the 43 patients who used this pump in heart bypass operations we observed that the free hemoglobin ranged from 9.34 mg% before to 44.16 mg% after surgery, the serum fibrinogen was from 236.65 mg% to 547.26mg%, platelet blood count from 152,465 to 98,139 and the lactic dehydrogenase from 238.12mg% to 547.26mg%. The Activated Coagulation Time was close to 800 seconds during the bypass.

Conclusion: The Spiral Pump was very effective in generating adequate flow and pressure and caused no excessive harm to the blood cells.
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http://dx.doi.org/10.1590/s0102-76382007000200012DOI Listing
September 2008

Hemolysis in an electromechanical driven pulsatile total artificial heart.

Artif Organs 2003 Dec;27(12):1089-93

Department of Cardiovascular Surgery, Chiba, Japan.

A motor rotation in an electromechanically-driven pulsatile total artificial heart (TAH) may influence hemolysis. This study is designed to evaluate motor rotational conditions of the TAH and choose a suitable condition to obtain the least hemolytic characteristics. The TAH was driven in two motor rotational conditions: a constant motor rotational speed (rpm) mode (mode A) and a gradually increasing rpm mode (mode B). In these two modes, a maximum dP/dt value and a degree of hemolysis were measured and compared. The TAH was connected to an in vitro testing loop. In each mode, the TAH was driven with a fixed pumping rate of 100 bpm. A preload and an afterload were held at 15 and 100 mm Hg, respectively. The outflow of the TAH was maintained at 4.0 L/min. The maximum dP/dt in mode A and mode B was 5914 +/- 405 mm Hg/s and 2953 +/- 191 mm Hg/s, respectively. The NIH value obtained from mode A and mode B was 0.063 +/- 0.005 g/100 L and 0.026 +/- 0.003 g/100 L, respectively. The results demonstrated that the TAH driven in a gradually increasing rpm mode reduces both a maximum dP/dt value and a degree of hemolysis. The gradually increasing rpm mode is a suitable driving condition to obtain the least hemolytic characteristics.
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http://dx.doi.org/10.1111/j.1525-1594.2003.07088.xDOI Listing
December 2003
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