A Hybrid Mock Circulation Loop for a Total Artificial Heart

Nestler, Frank; Bradley, Andrew P.; Wilson, Stephen J.; Timms, Daniel; Frazier, O.H.; Cohn, William E.

doi:10.1111/aor.12380

Cited by 35 publications

(26 citation statements)

References 25 publications

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“…The in vitro experiments were conducted in a hybrid mock circulation loop, 29 where the RBPs were operated in the physical domain, while the vasculature was implemented in the numerical domain as a lumped parameter model. The circuit was filled with a 40% by weight glycerol-water solution at 23°C to match the viscosity of blood at 37°C, 3.3 mPas.…”

Section: In Vitro Evaluationmentioning

confidence: 99%

Investigation of the inherent left‐right flow balancing of rotary total artificial hearts by means of a resistance box

et al. 2020

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With the incidence of end-stage heart failure steadily increasing, the need for a practical total artificial heart (TAH) has never been greater. Continuous flow TAHs (CFTAH) are being developed using rotary blood pumps (RBPs), leveraging their small size, mechanical simplicity, and excellent durability. To completely replace the heart with currently available RBPs, two are required; one for providing pulmonary flow and one for providing systemic flow. To prevent hazardous states, it is essential to maintain balance between the pulmonary and systemic circulation at a wide variety of physiologic states. In this study, we investigated factors determining a CFTAH's inherent ability to balance systemic and pulmonary flow passively, without active management of pump rotational speed. Four different RBPs (ReliantHeart HA5, Thoratec HMII, HeartWare HVAD, and Ventracor VentrAssist) were used in various combinations to construct CFTAHs. Each CFTAH's ability to autonomously maintain pressures and flows within defined ranges was evaluated in a hybrid mock loop as systemic and pulmonary vascular resistance (PVR) were changed. The resistance box, a method to quantify the range of vascular resistances that can be safely supported by a CFTAH, was used to compare different CFTAH configurations in an efficient and predictive way. To reduce the need for future in vitro tests and to aid in their analysis, a novel analytical evaluation to predict the resistance box of various CFTAH configurations was also performed. None of the investigated CFTAH configurations fully satisfied the predefined benchmarks for inherent flow balancing, with the VentrAssist (left) andHeartAssist 5 (right) offering the best combination. The extent to which each CFTAH was able to autonomously maintain balance was determined by the pressure sensitivity of each RPB: the sensitivity of outflow to changes in the pressure head. The analytical model showed that by matching left and right pressure sensitivity the inherent balancing performance can be improved. These findings may ultimately lead to a reduced need for manual speed changes or active control systems. K E Y W O R D Sbalancing, pressure sensitivity, resistance box, rotary blood pump, total artificial heart | 585 NESTLER ET aL.

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Section: In Vitro Evaluationmentioning

confidence: 99%

Investigation of the inherent left‐right flow balancing of rotary total artificial hearts by means of a resistance box

et al. 2020

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“…The hardware-in-loop (HIL) technique is a method that has been used to construct cardiovascular hybrid frameworks. [16][17][18] However, the real-time nature of previous implementations results in constraints by signal noise and bandwidth of the hydraulic sensors and actuators, limiting the final model accuracy. These limitations motivate the development of a more robust technique for performing HIL in a hybrid framework.…”

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An algorithm for coupling multibranch in vitro experiment to numerical physiology simulation for a hybrid cardiovascular model

Mirzaei

Farahmand

Kung

2019

Numer Methods Biomed Eng

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The hybrid cardiovascular modeling approach integrates an in vitro experiment with a computational lumped‐parameter simulation, enabling direct physical testing of medical devices in the context of closed‐loop physiology. The interface between the in vitro and computational domains is essential for properly capturing the dynamic interactions of the two. To this end, we developed an iterative algorithm capable of coupling an in vitro experiment containing multiple branches to a lumped‐parameter physiology simulation. This algorithm identifies the unique flow waveform solution for each branch of the experiment using an iterative Broyden's approach. For the purpose of algorithm testing, we first used mathematical surrogates to represent the in vitro experiments and demonstrated five scenarios where the in vitro surrogates are coupled to the computational physiology of a Fontan patient. This testing approach allows validation of the coupling result accuracy as the mathematical surrogates can be directly integrated into the computational simulation to obtain the “true solution” of the coupled system. Our algorithm successfully identified the solution flow waveforms in all test scenarios with results matching the true solutions with high accuracy. In all test cases, the number of iterations to achieve the desired convergence criteria was less than 130. To emulate realistic in vitro experiments in which noise contaminates the measurements, we perturbed the surrogate models by adding random noise. The convergence tolerance achievable with the coupling algorithm remained below the magnitudes of the added noise in all cases. Finally, we used this algorithm to couple a physical experiment to the computational physiology model to demonstrate its real‐world applicability.

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“…The ovine is a frequently used preclinical animal model for the assessment of cardiovascular device function and biocompatibility (1)(2)(3)(4)(5)(6)(7)(8)(9). Adult ovines have hearts that are similar in size to the human heart for evaluation of implantable devices such as ventricular assist devices (VAD).…”

mentioning

confidence: 99%

“…One of the primary endpoints of preclinical testing of blood contacting cardiovascular devices is to ensure adequate blood biocompatibility (6,7,(9)(10)(11)(12)(13)(14). Previously, flow cytometric assays to quantify activated ovine platelets have been reported and shown to be sensitive to blood pump complications and when there was subsequent evidence of throm-…”

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Use of a Mechanical Circulatory Support Simulation to Study Pump Interactions With the Variable Hemodynamic Environment

Horvath¹,

Horvath²,

Karimov

et al. 2018

Artificial Organs

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The Virtual Mock Loop, a versatile virtual mock circulation loop, was developed using a lumpedparameter model of the mechanically assisted human circulatory system. Inputs allow specification of a variety of continuous-flow pumps (left, right, or biventricular assist devices) and a total artificial heart that can selfregulate between left and right pump outputs. Hemodynamic inputs were simplified using a diseasebased input panel, allowing selection of a combination of cardiovascular disease states, including systolic and diastolic heart failure, stenosis, and/or regurgitation in each of the four valves, and high to low systemic and pulmonary vascular resistance values. The menu-driven output includes a summary of hemodynamic parameters and graphical output of selected flows, pressures, and volumes in the heart's four chambers as well as in the pulmonary artery and aorta.New tools to augment experimental research on implantable heart-assist devices and to increase our understanding of patient-specific pump interactions are in high demand. The purpose of this ongoing study is to demonstrate the use of a system analysis computer simulation to explore and better comprehend the interactions of mechanical circulatory support (MCS) pumps with a more extensive combination of patientspecific or simulation conditions than can be established by practical experimentation. Usability is an important factor in constructing computer models for research purposes, and among our primary objectives in creating this simulation model were to make it as portable and useful as possible outside the lab environment, by people not involved in the creation of its operational software.

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A Hybrid Mock Circulation Loop for a Total Artificial Heart

Cited by 35 publications

References 25 publications

Investigation of the inherent left‐right flow balancing of rotary total artificial hearts by means of a resistance box

Investigation of the inherent left‐right flow balancing of rotary total artificial hearts by means of a resistance box

An algorithm for coupling multibranch in vitro experiment to numerical physiology simulation for a hybrid cardiovascular model

Use of a Mechanical Circulatory Support Simulation to Study Pump Interactions With the Variable Hemodynamic Environment

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