Artykuły w czasopismach: „Cardiovascular system - Computer simulation”

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Bai, Jing, Hongli Lu, Jupeng Zhang i Xiaoqiang Zhou. "Simulation Study of the Interaction between Respiration and the Cardiovascular System". Methods of Information in Medicine 36, nr 04/05 (październik 1997): 261–63. http://dx.doi.org/10.1055/s-0038-1636875.

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Abstract.Many studies have been done on the respiratory and the cardiovascular system. Among them, only a few are on the interaction of these two physiologic systems. To explore the mechanism of the integration of these two physiological systems, computer simulation has been done; we report the preliminary results obtained in our laboratory. In this study, a mathematical model of the cardiovascular system integrated with the respiratory mechanical system has been established. The model is based on our previous work on cardiovascular modeling. The previous lumped lungi model has been replaced by a multielement model with more detail. Inter- thoracic and abdominal pressures are modeled as external pressure sources on the related cardiovascular elements. Using this model, a sequence of simulation studies have been carried out. Different respiratory modes have been simulated and the different effects are observed in the simulation results. The results indicate that by following a certain respiratory pattern, the circulation status can be improved. These results agree with clinical observations.Keywords: Mathematical Model, Respiration Mode, Cardiovascular System, Computer Simulation, Interaction

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Masuzawa, Toru, Yasuhiro Fukui i N. T. Smith. "Cardiovascular simulation using a multiple modeling method on a digital computer—Simulation of interaction between the cardiovascular system and angiotensin II". Journal of Clinical Monitoring 8, nr 1 (styczeń 1992): 50–58. http://dx.doi.org/10.1007/bf01618088.

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Neglia, D., G. Ferrari, F. Bernini, M. Micalizzi, A. L’Abbate, M. G. Trivella i C. De Lazzari. "Computer Simulation of Coronary Flow Waveforms during Caval Occlusion". Methods of Information in Medicine 48, nr 02 (2009): 113–22. http://dx.doi.org/10.3414/me0539.

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Summary Objectives: Mathematical modeling of the cardiovascular system is a powerful tool to extract physiologically relevant information from multi-parametric experiments. The purpose of the present work was to reproduce by means of a computer simulator, systemic and coronary measurements obtained by in vivo experiments in the pig. Methods: We monitored in anesthetized open-chest pig the phasic blood flow of the left descending coronary artery, aortic pressure, left ventricular pressure and volume. Data were acquired before, during, and after caval occlusion.Inside the software simulator (CARDIOSIM©) of the cardiovascular system, coronary circulation was modeled in three parallel branching sections. Both systemic and pulmonary circulations were simulated using a lumped parameter mathematical model. Variable elastance model reproduced Starling’s law of the heart. Results: Different left ventricular pressure-volume loops during experimental caval occlusion and simulated cardiac loops are presented. The sequence of coronary flow-aortic pressure loops obtained in vivo during caval occlusion together with the simulated loops reproduced by the software simulator are reported. Finally experimental and simulated instantaneous coronary blood flow waveforms are shown. Conclusions: The lumped parameter model of the coronary circulation, together with the cardiovascular system model, is capable of reproducing the changes during caval occlusion, with the profound shape deformation of the flow signal observed during the in vivo experiment. In perspectives, the results of the present model could offer new tool for studying the role of the different determinants of myocardial perfusion, by using the coronary loop shape as a “sensor” of ventricular mechanics in various physiological and pathophysiological conditions.

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Spicer, Sean A., i Charles A. Taylor. "Simulation-Based Medical Planning for Cardiovascular Disease: Visualization System Foundations". Computer Aided Surgery 5, nr 2 (styczeń 2000): 82–89. http://dx.doi.org/10.3109/10929080009148874.

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Spicer, Sean A., i Charles A. Taylor. "Simulation‐based medical planning for cardiovascular disease: Visualization system foundations". Computer Aided Surgery 5, nr 2 (2000): 82–89. http://dx.doi.org/10.1002/1097-0150(2000)5:2<82::aid-igs2>3.3.co;2-x.

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Nebot, Angela, François E. Cellier i Montserrat Vallverdú. "Mixed quantitative/qualitative modeling and simulation of the cardiovascular system". Computer Methods and Programs in Biomedicine 55, nr 2 (luty 1998): 127–55. http://dx.doi.org/10.1016/s0169-2607(97)00056-4.

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Sato, Toshiro, Akihiro Takeuchi, Jun Yamagami, Hareaki Yamamoto, Shigeaki Akiyama, Kyoko Endou, Masuo Shirataka, Noriaki Ikeda i Harukazu Tsuruta. "Computer assisted instruction for therapy of heart failure based on simulation of cardiovascular system". ACM SIGBIO Newsletter 9, nr 1 (marzec 1987): 57–61. http://dx.doi.org/10.1145/25065.25066.

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Bora, Şebnem, Vedat Evren, Sevcan Emek i Ibrahim Çakırlar. "Agent-based modeling and simulation of blood vessels in the cardiovascular system". SIMULATION 95, nr 4 (9.06.2017): 297–312. http://dx.doi.org/10.1177/0037549717712602.

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The purpose of this study is to develop a model to simulate the behavior of the human cardiovascular system for use in medical education. The proposed model ensures that the output of the system is accurately represented in both equilibrium conditions and imbalance conditions including in the presence of adaptive agents. In this study, field experts develop an agent-based blood vessel model, i.e., a submodel for the stated purpose. In the proposed blood vessel model, vessels are represented by agents whereas blood flow is represented by the interaction between agents. Adaptive behavior shown by vessels in terms of resistance to the blood flow is defined by the agents’ properties, which are used as the basis for calculating and graphically representing the physical parameters of blood flow, specifically blood pressure, blood flow velocity, and the resistance of the vessel. The adaptation of the vessel agents is supported by a case study, which demonstrates the adaptive behavior of the blood vessel agents through a negative feedback control mechanism. The blood vessel model proposed is flexible in nature such that it can be adapted to account for the behavior of the vessel sections in any vascular structure.

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Smith, Bram W., Steen Andreassen, Geoffrey M. Shaw, Per L. Jensen, Stephen E. Rees i J. Geoffrey Chase. "Simulation of cardiovascular system diseases by including the autonomic nervous system into a minimal model". Computer Methods and Programs in Biomedicine 86, nr 2 (maj 2007): 153–60. http://dx.doi.org/10.1016/j.cmpb.2007.02.001.

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Steele, B. N., M. T. Draney, J. P. Ku i C. A. Taylor. "Internet-based system for simulation-based medical planning for cardiovascular disease". IEEE Transactions on Information Technology in Biomedicine 7, nr 2 (czerwiec 2003): 123–29. http://dx.doi.org/10.1109/titb.2003.811880.

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Raczynski, P., A. Dawid, Z. Dendzik i Z. Gburski. "Computer Simulation of the Dynamics of Homocysteine Molecules Surrounding a Carbon Nanotube". Solid State Phenomena 140 (październik 2008): 147–52. http://dx.doi.org/10.4028/www.scientific.net/ssp.140.147.

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Excessive amounts of homocysteine in the human body have been considered recently as a factor which increases the risk of developing diseases of the cardiovascular system. The nanosystem composed of homocysteine molecules covering a single walled carbon nanotube have been studied by MD technique. The translational and rotational velocity correlation functions have been calculated for several temperatures, including the physiological temperature of 309 K. The qualitative interpretation of translational and reorientational dynamics of homocysteine molecules in this specific environment is presented.

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de Canete, J. Fernandez, P. del Saz-Orozco, D. Moreno-Boza i E. Duran-Venegas. "Object-oriented modeling and simulation of the closed loop cardiovascular system by using SIMSCAPE". Computers in Biology and Medicine 43, nr 4 (maj 2013): 323–33. http://dx.doi.org/10.1016/j.compbiomed.2013.01.007.

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Ursino, M., M. Antonucci i E. Belardinelli. "Role of active changes in venous capacity by the carotid baroreflex: analysis with a mathematical model". American Journal of Physiology-Heart and Circulatory Physiology 267, nr 6 (1.12.1994): H2531—H2546. http://dx.doi.org/10.1152/ajpheart.1994.267.6.h2531.

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To elucidate the role of venous capacity active changes in short-term cardiovascular homeostasis, a mathematical model of the carotid-sinus baroreflex system has been developed. In the model the cardiovascular system is represented as the series arrangement of six lumped compartments, which synthesize the fundamental hemodynamic properties of the systemic arterial, systemic venous, pulmonary arterial, and pulmonary venous circulations as well as of the left and right cardiac volumes. Cardiac outputs from the left and right ventricles are computed as a function of both downstream arterial pressure (afterload) and upstream atrial pressure (preload). Four distinct feedback regulatory mechanisms, working on systemic arterial resistance, heart rate, systemic venous unstressed volume, and systemic venous compliance, are assumed to operate on the cardiovascular system in response to carotid sinus pressure changes. All model parameters, both in the cardiovascular system and in feedback regulatory mechanisms, have been assigned on the basis of physiological data now available. The model is used here to simulate the pattern of the main hemodynamic quantities in the short time period (1-2 min) after acute carotid sinus activation in vagotomized subjects. Simulation results indicate that the model can reproduce experimental data quite well, with reference both to open-loop experiments and to an acute blood hemorrhage performed in closed-loop conditions. Moreover, computer simulations indicate that active changes in venous unstressed volume are of primary importance in regulating cardiac output and systemic arterial pressure during activation of the carotid sinus baroreflex.

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Asami, Kenichi. "Design of a Human Circulation Modeling System for Fitness Training". Journal of Robotics and Mechatronics 17, nr 6 (20.12.2005): 608–16. http://dx.doi.org/10.20965/jrm.2005.p0608.

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A physiological modeling and simulation system to support fitness training in which the cardiovascular system model predicts pulsatile blood flows in response to exercise levels is presented. A circulation monitor and simulator that allow interaction of humans with health enhancement devices enable development of intelligent fitness machines. A modeling and simulation system of the human circulation is necessary to realize safe and effective machines. In order to construct a better architecture of the assisting framework, a modeling and simulation system for the human circulation for fitness work could contribute to the effectiveness of programs for rehabilitation, weight change, health enhancement, and physical strengthening.

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Vallverdú, Montserrat, Carles Crexells i Pere Caminal. "Cardiovascular responses to intrathoracic pressure variations in coronary disease patients: a computer simulation". Technology and Health Care 2, nr 2 (1.07.1994): 119–40. http://dx.doi.org/10.3233/thc-1994-2207.

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Siddiqui, Shahan Yamin, Atifa Athar, Muhammad Adnan Khan, Sagheer Abbas, Yousaf Saeed, Muhammad Farrukh Khan i Muhammad Hussain. "Modelling, Simulation and Optimization of Diagnosis Cardiovascular Disease Using Computational Intelligence Approaches". Journal of Medical Imaging and Health Informatics 10, nr 5 (1.05.2020): 1005–22. http://dx.doi.org/10.1166/jmihi.2020.2996.

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Background: To provide ease to diagnose that serious sickness multi-technique model is proposed. Data Analytics and Machine intelligence are involved in the detection of various diseases for human health care. The computer is used as a tool by experts in the medical field, and the computer-based mechanism is used to diagnose different diseases in patients with high Precision. Due to revolutionary measures employed in Artificial Neural Networks (ANNs) within the research domain in the medical area, which appear to be in the data-driven applications usually described in the domain of health care. Cardio sickness according to name is a type of an ailment that is directly connected to the human heart and blood circulation setup, so it should be diagnosed on time because the delay of diagnosing of that disease may lead the sufferer to death. The research is mainly aimed to design a system that will be able to detect cardiovascular sickness in the sufferer using machine learning approaches. Objective: The main objective of the research is to gather information of the six parameters that is age, chest pain, electrocardiogram, systolic blood pressure, fasting blood sugar and serum cholesterol are used by Mamdani fuzzy expert to detect cardiovascular sickness. To propose a type of device which will be successfully used in overcoming the cardiovascular diseases. This proposed model Diagnosis Cardiovascular Disease using Mamdani Fuzzy Inference System (DCD-MFIS) shows 87.05 percent Precision. To delineate an effective Neural Network Model to predict with greater precision, whether a person is suffering from cardiovascular disease or not. As the ANN is composed of various algorithms, some will be handed down for the training of the network. The main target of the research is to make the use of three techniques, which include fuzzy logic, neural network, and deep machine learning. The research will employ the three techniques along with the previous comparisons, and given that, the results will be compared respectively. Methods: Artificial neural network and deep machine learning techniques are applied to detect cardiovascular sickness. Both techniques are applied using 13 parameters age, gender, chest pain, systolic blood pressure, serum cholesterol, fasting blood sugar, electrocardiogram, exercise including angina, heart rate, old peak, number of vessels, affected person and slope. In this research, the ANN-based research is one of the algorithms collections, which is the detection of cardiovascular diseases, is proposed. ANN constitutes of many algorithms, some of the algorithms are employed in the paper for the training of the network used, to achieve the prediction ratio and in contrast of the comparison of the mutual results shown. Results: To make better analysis and consideration of the three frameworks, which include fuzzy logic, ANN, Deep Extreme Machine Learning. The proposed automated model Diagnosis Cardiovascular Disease includes Fuzzy logic using Mamdani Fuzzy Inference System (DCD-MFIS), Artificial Neural Network (DCD–ANN) and Deep Extreme Machine Learning (DCD–DEML) approach using back propagation system. These frameworks help in attaining greater precision and accuracy. Proposed DCD Deep Extreme Machine Learning attains more accuracy with previously proposed solutions that are 92.45%. Conclusion: From the previous comparisons, the propose automated Diagnosis of Cardiovascular Disease using Fuzzy logic, Artificial Neural Network, and deep extreme machine learning approaches. The automated systems DCDMFIS, DCD–ANN and DCD–DEML, the framework proposed as effective and efficient with 87.05%, 89.4% and 92.45 % success ratios respectively. To verify the performance which lies in the ANNs and computational analysis, many indicators determining the precise performance were calculated. The training of the neural networks is made true using the 10 to 20 neurons layers which denote the hidden layer. DEML reveals and indicates a hidden layer containing 10 neurons, which shows the best result. In the last, we can conclude that after making a consideration among the three techniques fuzzy logic, Artificial Neural Network and Proposed DCD Deep Extreme Machine, the Proposed DCD Deep Extreme Machine Learning based solution give more accuracy with previously proposed solutions that are 92.45%.

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Eblen-Zajjur, Antonio. "A SIMPLE BALLISTOCARDIOGRAPHIC SYSTEM FOR A MEDICAL CARDIOVASCULAR PHYSIOLOGY COURSE". Advances in Physiology Education 27, nr 4 (grudzień 2003): 224–29. http://dx.doi.org/10.1152/advan.00025.2002.

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Ballistocardiography is an old, noninvasive technique used to record the movements of the body synchronous with the heartbeat due to left ventricular pump activity. Despite the fact that this technique to measure cardiac output has been superseded by more advanced and precise techniques, it is useful for teaching cardiac cycle physiology in an undergraduate practical course because of its noninvasive application in humans, clear physiological and physiopathological analysis, and practical approach to considering cardiac output issues. In the present report, a simple, low cost, easy-to-build ballistocardiography system is implemented together with a theoretical and practical session that includes Newton’s laws, cardiac output, cardiac pump activity, anatomy and physiology of the vessel circulation, vectorial composition, and signal transduction, which makes cardiovascular physiology easy to understand and focuses on the study of cardiac output otherwise seen only with the help of computer simulation or echocardiography. The proposed system is able to record body displacement or force as ballistocardiography traces and its changes caused by different physiological factors. The ballistocardiography session was included in our medical physiology course six years ago with very high acceptance and approval rates from the students.

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Vollkron, Michael, Heinrich Schima, Leopold Huber i Georg Wieselthaler. "Interaction of the Cardiovascular System with an Implanted Rotary Assist Device: Simulation Study with a Refined Computer Model>". Artificial Organs 26, nr 4 (kwiecień 2002): 349–59. http://dx.doi.org/10.1046/j.1525-1594.2002.06870.x.

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Leor-Librach, Ron Joseph, Ben-Zion Bobrovsky, Sarah Eliash i Elieser Kaplinsky. "Computer-controlled heart rate increase by isoproterenol infusion: mathematical modeling of the system". American Journal of Physiology-Heart and Circulatory Physiology 277, nr 4 (1.10.1999): H1478—H1483. http://dx.doi.org/10.1152/ajpheart.1999.277.4.h1478.

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The purpose of this study was mathematical modeling of the heart rate (HR) response to isoproterenol (Iso) infusion. We developed a computerized system for the controlled increase of HR by Iso, based on a modified proportional-integral controller. HR was measured in conscious, freely moving rats. We found that the steady-state HR can be described as a hyperbolic power function of the steady-state Iso flow rate. This dependence was coupled with a first-order difference equation to form a pharmacodynamic model that reliably describes the relationship between HR and Iso flow for any arbitrary form of Iso flow function. In simulation studies, we showed that the model continued to follow the HR curve from real-time experiments far beyond the initial “learning interval” from which its parameters were calculated. Our results suggest that the predictive ability and the simplicity of calculating the parameters render this pharmacodynamic model appropriate for use within future advanced, model-based, adaptive control systems and as a part of larger cardiovascular models.

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Ying Sun i Salvatore Chiaramida. "Simulation of hemodynamics and regulatory mechanisms in the cardiovascular system based on a nonlinear and time-varying model". SIMULATION 59, nr 1 (lipiec 1992): 28–36. http://dx.doi.org/10.1177/003754979205900107.

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Nicol, S., i C. Narkowicz. "Learning physiology from cardiac surgery patients." Advances in Physiology Education 274, nr 6 (czerwiec 1998): S74. http://dx.doi.org/10.1152/advances.1998.274.6.s74.

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A number of pressures have led to a very great reduction or complete abandonment of the use of animals in the teaching of physiology in most medical schools. Often animal experiments have been replaced by computer simulations, but a simulation is only as good as the model or algorithm on which it is based and can never contain the depth of information or unpredictability displayed by real animals or patients. We used a computer-based system to collect cardiovascular data from patients instrumented for cardiac surgery, allowing students to "replay" an operation. These recordings were annotated with notes, diagrams and video clips, and a student workbook was written. The resulting package contained a wealth of physiological data and was perceived by students to be very clinically relevant. The very wealth of information, however, tended to overwhelm students, and so a series of introductory Computer tutorials were written to provide students with the background necessary to cope with the clinical data.

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Clemente, F., C. De Lazzari, M. Darowski, G. Ferrari, R. Mimmo, M. Guaragno i G. Tosti. "Study of Systolic Pressure Variation (SPV) in Presence of Mechanical Ventilation". International Journal of Artificial Organs 25, nr 4 (kwiecień 2002): 313–20. http://dx.doi.org/10.1177/039139880202500410.

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Systolic pressure variation (SPV) and its components (dUp and dDown) have been demonstrated to be of interest in assessing preload in mechanically ventilated patients. The aim of this paper is to analyse the sensitivity of these variables to preload and volemic changes during mechanical ventilation in different conditions of the cardiovascular system. Computer simulation experiments have been done using a modular lumped parameter model of the cardiovascular system. The effect of mechanical ventilation has been reproduced operating on intrathoracic pressure. Experiments have been performed varying preload through filling pressure. Sensitivity of SVP, dUp and dDown is described varying separately left ventricular elastance (Ev), systemic arterial resistance (Ras) and systemic arterial compliance (Cas). The sensitivity of SPV and dDown to preload and filling pressure is appreciable for high values of Ev and for a wide variation of Ras. Preliminary clinical data concerning the three parameters show good correlation with simulation results.

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Banks, H. T., Kathleen Holm, Nathan C. Wanner, Ariel Cintrón-Arias, Grace M. Kepler i Jeffrey D. Wetherington. "A mathematical model for the first-pass dynamics of antibiotics acting on the cardiovascular system". Mathematical and Computer Modelling 50, nr 7-8 (październik 2009): 959–74. http://dx.doi.org/10.1016/j.mcm.2009.02.007.

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Yamada, Toshiyuki, Motohiko Osaka, Tomoya Uchimuro, Ryogen Yoon, Toshiaki Morikawa, Maki Sugimoto, Hisao Suda i Hideyuki Shimizu. "Three-Dimensional Printing of Life-Like Models for Simulation and Training of Minimally Invasive Cardiac Surgery". Innovations: Technology and Techniques in Cardiothoracic and Vascular Surgery 12, nr 6 (listopad 2017): 459–65. http://dx.doi.org/10.1097/imi.0000000000000423.

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Objective As the use of minimally invasive surgery in cardiothoracic surgery increases, so does the need for simulation and training. We developed a heart model for simulation and training of minimally invasive cardiac surgery, particularly minimally invasive mitral valve repair using our new three-dimensional printing system. Methods Digital imaging and communication in medicine data from patient computed tomography, three-dimensional computer-aided design, and three-dimensional printing helped create replicas of the heart and thoracic cavity. A polyvinyl alcohol model material with a texture and physical properties similar to those of heart tissue was initially used in mitral valve replicas to simulate surgical procedures. To develop this material, we mechanically investigated the composition of each part of the porcine heart. Results We investigated the elastic modulus and breaking strength of the porcine heart. Based on investigation results, the cardiac model was set at rupture strength 20 MPa, elastic modulus 0.17 MPa, and moisture content 85%. This provided a biotexture and feeling exactly like a patient heart. Computed tomography scans confirmed that the model shape was nearly the same as that of a human heart. We simulated minimally invasive mitral valve repair, including ring annuloplasty, chordal reconstruction, resection and suture, and edge-to-edge repair. Full surgery simulations using this model used minimally invasive cardiac surgery tools including a robot. Conclusions This life-like model can be used as a standard simulator to train younger, less experienced surgeons to practice minimally invasive cardiac surgery procedures and may help develop new operative tools.

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Ranftl, Sascha, Gian Marco Melito, Vahid Badeli, Alice Reinbacher-Köstinger, Katrin Ellermann i Wolfgang von der Linden. "On the Diagnosis of Aortic Dissection with Impedance Cardiography: A Bayesian Feasibility Study Framework with Multi-Fidelity Simulation Data". Proceedings 33, nr 1 (9.12.2019): 24. http://dx.doi.org/10.3390/proceedings2019033024.

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Aortic dissection is a cardiovascular disease with a disconcertingly high mortality. When it comes to diagnosis, medical imaging techniques such as Computed Tomography, Magnetic Resonance Tomography or Ultrasound certainly do the job, but also have their shortcomings. Impedance cardiography is a standard method to monitor a patients heart function and circulatory system by injecting electric currents and measuring voltage drops between electrode pairs attached to the human body. If such measurements distinguished healthy from dissected aortas, one could improve clinical procedures. Experiments are quite difficult, and thus we investigate the feasibility with finite element simulations beforehand. In these simulations, we find uncertain input parameters, e.g., the electrical conductivity of blood. Inference on the state of the aorta from impedance measurements defines an inverse problem in which forward uncertainty propagation through the simulation with vanilla Monte Carlo demands a prohibitively large computational effort. To overcome this limitation, we combine two simulations: one simulation with a high fidelity and another simulation with a low fidelity, and low and high computational costs accordingly. We use the inexpensive low-fidelity simulation to learn about the expensive high-fidelity simulation. It all boils down to a regression problem—and reduces total computational cost after all.

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Hope, I. D., F. J. Huikeshoven, R. D. Gilbert, G. G. Power i L. D. Longo. "Errors in microsphere determination of cardiac output: a computer simulation in fetal sheep". American Journal of Physiology-Heart and Circulatory Physiology 256, nr 1 (1.01.1989): H302—H310. http://dx.doi.org/10.1152/ajpheart.1989.256.1.h302.

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Through use of a compartmental model, we simulated the measurement of cardiac output and distribution by means of radioactively labeled microspheres in fetal lambs with weights between 0.5 and 3 kg. A systematic error in measured cardiac output caused by artifactual changes in blood volume caused by the injection and withdrawal of fluids during the procedure was less than 5% for fetal weights greater than or equal to 1 kg but increased for fetal weights less than 1 kg and when hypovolemia was simulated at all fetal weights. Sensitivity analysis disclosed no significant effect of changes in vascular resistance. We examined the effects of recirculation of microspheres and found no significant increase in error in the measured value of cardiac output due to 20% recirculation of all spheres entering a single isolated organ system; however, errors between 7 and 14% were observed with simulations of 20% recirculation in more than one compartment simultaneously. Recirculation also introduced significant errors in the measured distribution of cardiac output in certain cases. The effect on the measured cardiac output of a temporary change in the true cardiac output was dampened by the artifactual blood volume changes mentioned above and the fact that the measurement is a time-weighted average. We also evaluated four different experimental designs. We conclude that the microsphere technique provides a remarkably reliable means of quantifying cardiac output and individual organ flow in the fetus. The nonrandom errors inherent in the procedure examined in this study are of the order of 10%, which is likely to be less than the moment-to-moment variation in the true cardiac output.

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Shi, Yubing, i Theodosios Korakianitis. "Impeller-pump model derived from conservation laws applied to the simulation of the cardiovascular system coupled to heart-assist pumps". Computers in Biology and Medicine 93 (luty 2018): 127–38. http://dx.doi.org/10.1016/j.compbiomed.2017.12.012.

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George, Jossy P., i Suhas M. Gaikwad. "Simulation modeling for heart attack patient by mapping cholesterol level". Indonesian Journal of Electrical Engineering and Computer Science 18, nr 1 (1.04.2020): 16. http://dx.doi.org/10.11591/ijeecs.v18.i1.pp16-23.

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<p>Cholesterol is a complex structural material made up of four-fused hydrocarbon rings. There is a hydrocarbon tail linked at one end of the structure, while the hydroxyl group linked to each other on the other end. To one end of the structure, a hydrocarbon tail linked and to the other end, a hydroxyl group linked to each other. High cholesterol level is one among the major risk factors of a heart attack. It is feasible to compute and control the cholesterol level of a cardiovascular patient by making use of intended Mathematical modeling in System Dynamics (S.D.). Moreover, by simulating proposed set of equations for a heart attack patient, recovery accomplished at a faster pace. Because of S.D., a substantial amount of reduction in the patient's Cardiovascular Disease achieved by control over the sterol level of the heart patient. This simulation modeling is an attempt made in translational research domain and is useful in the healthcare industry health care industry. It will minimize the risk of heart stroke and maintain a healthy life.</p>

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Le Rolle, Virginie, Alfredo I. Hernández, Pierre-Yves Richard i Guy Carrault. "An Autonomic Nervous System Model Applied to the Analysis of Orthostatic Tests". Modelling and Simulation in Engineering 2008 (2008): 1–15. http://dx.doi.org/10.1155/2008/427926.

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One of the clinical examinations performed to evaluate the autonomic nervous system (ANS) activity is the tilt test, which consists in studying the cardiovascular response to the change of a patient's position from a supine to a head-up position. The analysis of heart rate variability signals during tilt tests has been shown to be useful for risk stratification and diagnosis on different pathologies. However, the interpretation of such signals is a difficult task. The application of physiological models to assist the interpretation of these data has already been proposed in the literature, but this requires, as a previous step, the identification of patient-specific model parameters. In this paper, a model-based approach is proposed to reproduce individual heart rate signals acquired during tilt tests. A new physiological model adapted to this problem and coupling the ANS, the cardiovascular system (CVS), and global ventricular mechanics is presented. Evolutionary algorithms are used for the identification of patient-specific parameters in order to reproduce heart rate signals obtained during tilt tests performed on eight healthy subjects and eight diabetic patients. The proposed approach is able to reproduce the main components of the observed heart rate signals and represents a first step toward a model-based interpretation of these signals.

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Bozkurt, Selim, i Koray K. Safak. "Evaluating the Hemodynamical Response of a Cardiovascular System under Support of a Continuous Flow Left Ventricular Assist Device via Numerical Modeling and Simulations". Computational and Mathematical Methods in Medicine 2013 (2013): 1–12. http://dx.doi.org/10.1155/2013/986430.

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Dilated cardiomyopathy is the most common type of the heart failure which can be characterized by impaired ventricular contractility. Mechanical circulatory support devices were introduced into practice for the heart failure patients to bridge the time between the decision to transplant and the actual transplantation which is not sufficient due to the state of donor organ supply. In this study, the hemodynamic response of a cardiovascular system that includes a dilated cardiomyopathic heart under support of a newly developed continuous flow left ventricular assist device—Heart Turcica Axial—was evaluated employing computer simulations. For the evaluation, a numerical model which describes the pressure-flow rate relations of Heart Turcica Axial, a cardiovascular system model describing the healthy and pathological hemodynamics, and a baroreflex model regulating the heart rate were used. Heart Turcica Axial was operated between 8000 rpm and 11000 rpm speeds with 1000 rpm increments for assessing the pump performance and response of the cardiovascular system. The results also give an insight about the range of the possible operating speeds of Heart Turcica Axial in a clinical application. Based on the findings, operating speed of Heart Turcica Axial should be between 10000 rpm and 11000 rpm.

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Nazir Ahmed Kazi, Raisa, i Manjur Kolhar. "Smart Cardio Forecasting System for Patients with Cardiovascular Diseases Who Live Alone". Computers, Materials & Continua 66, nr 2 (2021): 1237–50. http://dx.doi.org/10.32604/cmc.2020.012707.

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Walker, Agnes, James R. G. Butler i Stephen Colagiuri. "Economic model system of chronic diseases in Australia: a novel approach initially focusing on diabetes and cardiovascular disease". International Journal of Simulation and Process Modelling 6, nr 2 (2010): 137. http://dx.doi.org/10.1504/ijspm.2010.036018.

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Zhang, Yi, i H. Harry Asada. "Blind System Identification of Noncoprime Multichannel Systems and Its Application to Noninvasive Cardiovascular Monitoring". Journal of Dynamic Systems, Measurement, and Control 126, nr 4 (1.12.2004): 834–47. http://dx.doi.org/10.1115/1.1852460.

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Multichannel blind system identification (MBSI) is a technique for estimating both an unknown input and unknown channel dynamics from outputs measured at different points of the system. MBSI is a powerful tool particularly for the identification and estimation of dynamical systems in which a sensor, for measuring the input, is difficult to place. MBSI algorithms, however, are not applicable unless the transfer functions of individual channels are coprime, i.e., sharing no common dynamics among the channels. This paper presents a MBSI method, called intermediate input identification (IIID), applicable to multichannel, noncoprime systems containing common dynamics. A variable is introduced to split the original multichannel system into coprime multichannel subsystems and the one consisting of common dynamics. A modified MBSI method is used for identifying the coprime distinct channel dynamics, while the common dynamics is identified based on its unforced response. Identifiability conditions using linear complexity are obtained for both known and unknown model structures. Uniqueness and other properties of the solution are examined. The IIID method is then applied to noninvasive monitoring of the cardiovascular system. The arterial network is modeled as a multichannel system where the blood flow generated by the left ventricle is the input and pressure profiles measured at different branches of the artery, e.g., brachial, carotid, and femoral arteries, are the outputs. While the direct measurement of the input requires a catheter to be inserted into the heart, the IIID method does not need invasive catheterization. It would allow us to estimate both the wave form of the input flow and the arterial channel dynamics from outputs obtained with noninvasive sensors placed at different branches of the arterial network. Numerical examples and simulations verify the major theoretical results and the feasibility of the method.

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Darowski, M., P. Wolski, G. Ferrari, G. Tosti, D. M. Pisanelli i C. De Lazzari. "In Vivo and Simulation Study of Artificial Ventilation Effects on Energetic Variables in Cardiosurgical Patients". Methods of Information in Medicine 44, nr 01 (2005): 98–105. http://dx.doi.org/10.1055/s-0038-1633928.

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Summary Objectives: The analysis of energetic ventricular variable changes during artificial ventilation, obtained by numerical simulation was done. Twenty-one sets of hemodynamic parameters for eight cardiosurgical patients were used to estimate left and right stroke work. The data were collected for three methods of ventilation: conventional, lung-protective (with minute ventilation diminished by half) and high frequency ventilation (with frequency 5, 10, or 15 Hz). Methods: The computer simulator (CARDIOSIM©) of the cardiovascular system, was used as a tool to calculate values of energetic ventricular variables for conditions that corresponded to these during in vivo measurements. Different methods of ventilation caused differences of intrathoracic pressure, haemodynamic and finally energetic ventricular variables. The trends of these variable changes were the same in in vivo and simulation studies, in the whole range of intrathoracic pressure changes (Pt = 1.5-3.5 mmHg). Results: As values of main hemodynamic variables like cardiac output or arterial, systemic and pulmonary pressures were very close in both studies. Cardiac index and left ventricular stroke work also differed less than 10% for all examined patients and computer simulation. In a case of right ventricular stroke work the difference between in vivo data and simulation was a bit greater than 10% for two of eight patients under study. Conclusions: Our comparative analysis proved that numerical simulation is a very useful tool to predict changes of main hemodynamic and energy-related ventricular variables caused by different levels of positive Pt. It means that it can help an anesthesiologist to choose an appropriate method of artificial ventilation for cardiosurgical patients.

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Mukherjee, Debasmita, Lakshmi Narayan Guin i Santabrata Chakravarty. "Dynamical behavior of a mathematical model of early atherosclerosis". International Journal of Modeling, Simulation, and Scientific Computing 11, nr 01 (luty 2020): 2050006. http://dx.doi.org/10.1142/s1793962320500063.

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Atherosclerosis, a continual inflammatory disease occurring due to plaque cumulation in the arterial intima, is one of the main reasons behind deaths from diverse cardiovascular diseases. The basic interactions between oxidized low density lipoprotein (LDL) and macrophages in the formation of atherosclerotic plaque are modeled here in terms of a reaction–diffusion system in one-dimensional (1D) space under Neumann boundary conditions. Two simple mathematical models are considered which differ by the influx term only in the case of the interaction of oxidized LDL. Both the spatial and nonspatial systems are simply analyzed theoretically and numerically. Numerical bifurcation analysis confirms the existence of Hopf bifurcation concerning four significant model parameters. Examining the gravity of the model offered in this investigation, an obvious insight into this inflammatory response can be achieved both qualitatively and quantitatively.

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Lyakhov, Pavel, Mariya Kiladze i Ulyana Lyakhova. "System for Neural Network Determination of Atrial Fibrillation on ECG Signals with Wavelet-Based Preprocessing". Applied Sciences 11, nr 16 (5.08.2021): 7213. http://dx.doi.org/10.3390/app11167213.

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Today, cardiovascular disease is the leading cause of death in developed countries. The most common arrhythmia is atrial fibrillation, which increases the risk of ischemic stroke. An electrocardiogram is one of the best methods for diagnosing cardiac arrhythmias. Often, the signals of the electrocardiogram are distorted by noises of varying nature. In this paper, we propose a neural network classification system for electrocardiogram signals based on the Long Short-Term Memory neural network architecture with a preprocessing stage. Signal preprocessing was carried out using a symlet wavelet filter with further application of the instantaneous frequency and spectral entropy functions. For the experimental part of the article, electrocardiogram signals were selected from the open database PhysioNet Computing in Cardiology Challenge 2017 (CinC Challenge). The simulation was carried out using the MatLab 2020b software package for solving technical calculations. The best simulation result was obtained using a symlet with five coefficients and made it possible to achieve an accuracy of 87.5% in recognizing electrocardiogram signals.

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Puiseux, Thomas, Anou Sewonu, Ramiro Moreno, Simon Mendez i Franck Nicoud. "Numerical simulation of time-resolved 3D phase-contrast magnetic resonance imaging". PLOS ONE 16, nr 3 (26.03.2021): e0248816. http://dx.doi.org/10.1371/journal.pone.0248816.

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A numerical approach is presented to efficiently simulate time-resolved 3D phase-contrast Magnetic resonance Imaging (or 4D Flow MRI) acquisitions under realistic flow conditions. The Navier-Stokes and Bloch equations are simultaneously solved with an Eulerian-Lagrangian formalism. A semi-analytic solution for the Bloch equations as well as a periodic particle seeding strategy are developed to reduce the computational cost. The velocity reconstruction pipeline is first validated by considering a Poiseuille flow configuration. The 4D Flow MRI simulation procedure is then applied to the flow within an in vitro flow phantom typical of the cardiovascular system. The simulated MR velocity images compare favorably to both the flow computed by solving the Navier-Stokes equations and experimental 4D Flow MRI measurements. A practical application is finally presented in which the MRI simulation framework is used to identify the origins of the MRI measurement errors.

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GIANNERINI, SIMONE, RODOLFO ROSA i DIEGO LUIS GONZALEZ. "TESTING CHAOTIC DYNAMICS IN SYSTEMS WITH TWO POSITIVE LYAPUNOV EXPONENTS: A BOOTSTRAP SOLUTION". International Journal of Bifurcation and Chaos 17, nr 01 (styczeń 2007): 169–82. http://dx.doi.org/10.1142/s0218127407017240.

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The present paper is devoted to the problem of detecting the presence of two positive Lyapunov exponents in time series data. In order to accomplish this task the accuracy of the estimates is essential, but existing estimation approaches do not provide it. We present a procedure exploiting resampling methods for building a statistical test for the presence of two positive exponents of comparable magnitudes through rigorous assessment of confidence intervals. The problem is studied by means of computer experiments performed in a variety of conditions on coupled Lorenz systems. Then, a case study regarding the time series of the cardiovascular activity of the toad Bufo Arenarum is presented. A comparison with other estimator algorithms is also shown.

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Horwitz, Barry. "Functional Interactions in the Brain: Use of Correlations between Regional Metabolic Rates". Journal of Cerebral Blood Flow & Metabolism 11, nr 1_suppl (marzec 1991): A114—A120. http://dx.doi.org/10.1038/jcbfm.1991.46.

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Correlation coefficients between pairs of regional metabolic rates have been used to study patterns of functional associations among brain regions in humans and animals. An overview is provided concerning the additional information about brain functioning this type of analysis yields. A computer simulation model is presented for the purpose of giving a partial validation for correlational analysis. The model generates a set of simulated metabolic data upon which correlational analysis is performed. Because the underlying pattern of functional couplings in the model is known, these simulations demonstrate that the correlation coefficient between normalized metabolic rates is proportional to the strength of the functional coupling constant and that correlational analysis yields information on regional involvement in neural systems not evident in the pattern of absolute metabolic values.

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Bucurenciu, Cristian, Victor S. Costache i Gabriela S. Cândea. "Study of aortic dissections treatment. Segmentation, simulation and valiadation of surgical results". MATEC Web of Conferences 290 (2019): 04004. http://dx.doi.org/10.1051/matecconf/201929004004.

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Nowadays, Computational Fluid Dynamics (CFD) it’s seen as the new trend in the management of aortic pathologies. Together with visualization capabilities of cardiovascular magnetic resonance (CMR) and computed tomography (CT) imaging, real time segmentation (volumetric) models further used as meshes in Computational Fluid Dynamic supply to the clinicians an innovative and extensive decision-making system. In the present paper, we identified and analysed the clinical indicators (lumens diameters, fenestrated area and blood volume) monitored by clinicians to evaluate the patient’ condition before and after the intervention. In order to achieve the targeted aims, we used CT scans as input data (segmented with MIMICS software) and output 3D models (3matic), further processed to mesh model in ANSYS software. Computational results validate the improved patient’ condition, meaning the blood velocity tend to have values to normal flowing conditions. As a conclusion, the linear modification of velocity can be used in further investigations as an input value of pathology treatment

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Benharash, Peyman, Paul Frank i Brenda Hoy. "Development and Use of a Novel Cardiovascular Simulator: Time for a Paradigm Shift?" American Surgeon 78, nr 10 (październik 2012): 1132–36. http://dx.doi.org/10.1177/000313481207801027.

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Understanding cardiovascular physiology, pharmacology, and treatment of shock is heavily emphasized in current medical school and surgical training. Performance of individuals in treatment of critical illness remains poor despite regular didactic sessions. We have developed a PC computer-based simulator capable of integrating basic hemodynamic parameters to dynamically generate a realistic patient monitor. The methodology includes physiological feedback as found in humans. The trainees are able to learn through a series of scenarios or ad lib manipulation of parameters. Participants including medical students, nurses, and residents were given a pretest before attending either a 30-minute didactic or a 10- or 30-minute simulator session. A posttest was administered to evaluate performance after the intervention. Twenty-four participants were equally randomized with 12 receiving simulator training. Although the two groups had similar pretest scores ( P > 0.5), the simulator group showed a 24 per cent improvement, whereas the lecture group showed a 10 per cent improvement in the posttest score ( P = 0.008). Simulations in surgery and critical care are in early stages of development. Access to such simulators on a personal computer can greatly enhance understanding of the cardiovascular system. These simulators appear to be very effective and may become an integral adjunct to traditional classroom teaching methods.

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Giovannetti, Giulio, Alessandra Flori, Maria Filomena Santarelli, Vincenzo Positano, Nicola Martini, Roberto Francischello, Rolf F. Schulte i in. "Radio Frequency Coils for Hyperpolarized 13C Magnetic Resonance Experiments with a 3T MR Clinical Scanner: Experience from a Cardiovascular Lab". Electronics 10, nr 4 (3.02.2021): 366. http://dx.doi.org/10.3390/electronics10040366.

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Hyperpolarized 13C magnetic resonance (MR) is a promising technique for the noninvasive assessment of the regional cardiac metabolism since it permits heart physiology studies in pig and mouse models. The main objective of the present study is to resume the work carried out at our electromagnetic laboratory in the field of radio frequency (RF) coil design, building, and testing. In this paper, first, we review the principles of RF coils, coil performance parameters, and estimation methods by using simulations, workbench, and MR imaging experiments. Then, we describe the simulation, design, and testing of different 13C coil configurations and acquisition settings for hyperpolarized studies on pig and mouse heart with a clinical 3T MRI scanner. The coil simulation is performed by developing a signal-to-noise ratio (SNR) model in terms of coil resistance, sample-induced resistance, and magnetic field pattern. Coil resistance was calculated from Ohm’s law and sample-induced resistances were estimated with a finite-difference time-domain (FDTD) algorithm. In contrast, the magnetic field per unit current was calculated by magnetostatic theory and a FDTD algorithm. The information could be of interest to graduate students and researchers working on the design and development of an MR coil to be used in 13C studies.

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Suhail, M. Mohamed, i T. Abdul Razak. "ECG Classification Framework for Cardiac Disease Prediction Using Nonlinear Vector Decomposed Neural Network". Journal of Computational and Theoretical Nanoscience 17, nr 12 (1.12.2020): 5563–69. http://dx.doi.org/10.1166/jctn.2020.9453.

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Early detection of heart disease may prevent myocardial infarction. Electrocardiogram (ECG) is the most widely used signal in clinical practice for the diagnosis of cardiovascular diseases such as arrhythmias and myocardial infarction. Human interpretation is time-consuming, and long-term ECG records are difficult to detect in small differences.Therefore, automated recognition of myocardial infarction using a Computer-Aided Diagnosis (CAD) system is the research interest, which can be used effectively to reduce mortality among cardiovascular disease patients. The most important step in the analysis of complex R-peak/QRS signals using an automated process of ECG signal. To automate the cardiovascular disease detection process, an adequate mechanism is required to characterize ECG signals, which are unknown features according to the similarities between ECG signals. If the classification can find similarities accurately and the probability of arrhythmia detection increases, the algorithm can become an effective method in the laboratory. In this research work, a new classification strategy is proposed to all the more precisely order ECG signals dependent on a powerful model of ECG signals. In this proposed method, a Nonlinear Vector Decomposed Neural Network (NVDN) is developed, and its simulation results show that this classifier can isolate the ECGs with high productivity. This proposed technique expands the exactness of the ECG classification concerning increasingly exact arrhythmia discovery.

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Vijaya, Kalavakonda, H. Khanna Nehemiah, A. Kannan i N. G. Bhuvaneswari. "Fuzzy neuro genetic approach for predicting the risk of cardiovascular diseases". International Journal of Data Mining, Modelling and Management 2, nr 4 (2010): 388. http://dx.doi.org/10.1504/ijdmmm.2010.035565.

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Keissar, Kobi, Linda R. Davrath i Solange Akselrod. "Coherence analysis between respiration and heart rate variability using continuous wavelet transform". Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 367, nr 1892 (27.02.2009): 1393–406. http://dx.doi.org/10.1098/rsta.2008.0273.

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The continuous wavelet transform (CWT) is specifically efficient in the analysis of transient and non-stationary signals. As such, it has become a powerful candidate for time–frequency analysis of cardiovascular variability. CWT has already been established as a valid tool for the analysis of single cardiovascular signals, providing additional insights into the autonomous nervous system (ANS) activity and its control mechanism. Intercorrelation between cardiovascular signals elucidates the function of ANS central control and the peripheral reflex mechanisms. Wavelet transform coherence (WTC) can provide insight into the transient linear order of the regulatory mechanisms, via the computation of time–frequency maps of the time-variant coherence. This paper presents a framework for applying WTC for quantitative analysis of coherence in cardiovascular variability research. Computer simulations were performed to estimate the accuracy of the WTC estimates and a method for determining the coherence threshold for specific frequency band was developed and evaluated. Finally, we demonstrated, in two representative situations, the dynamic behaviour of respiration sinus arrhythmia through the analysis of the WTC between heart rate and respiration signals. This emphasizes that CWT and its application to WTC is a useful tool for dynamic analysis of cardiovascular variability.

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Choi, Hyo Won, Zhen-Du Zhang, Neil D. Farren i Ghassan S. Kassab. "Implications of complex anatomical junctions on conductance catheter measurements of coronary arteries". Journal of Applied Physiology 114, nr 5 (1.03.2013): 656–64. http://dx.doi.org/10.1152/japplphysiol.00987.2012.

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In vivo, the position of the conductance catheter to measure vessel lumen cross-sectional area may vary depending on where the conductance catheter is deployed in the complex anatomical geometry of arteries, including branches, bifurcations, or curvatures. The objective here is to determine how such geometric variations affect the cross-sectional area (CSA) estimates obtained using the cylindrical model. Computer simulations and in vitro and in vivo experiments were used to assess how the electric field and associated CSA measurement accuracy are affected by three typical in vivo conditions: 1) a vessel with abrupt change in lumen diameter (e.g., transition from aorta to coronary ostia); 2) a vessel with a T-bifurcation or a Y-bifurcation; and 3) a vessel curvature, such as in the right coronary artery, aorta, or pulmonary artery. The error in diameter from simulation results was shown to be relatively small (<7%), unless the detection electrodes were placed near the junction between two different lumen diameters or at a bifurcation junction. Furthermore, the present findings show that the effect of misaligned catheter-vessel geometrical configuration and vessel curvature on measurement accuracy is negligible. Collectively, the findings support the accuracy of the conductance method for sizing blood vessels, despite the geometric complexities of the cardiovascular system, as long as the detection electrodes are not placed at a large discontinuity in diameter or at bifurcation junctions.

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Yavorska, Evhenia, Oksana Strembitska, Michael Strembitskyi i Iryna Pankiv. "Development of a simulation model of a photoplethysmographic signal under psychoemotional stress". Eastern-European Journal of Enterprise Technologies 2, nr 9 (110) (30.04.2021): 36–45. http://dx.doi.org/10.15587/1729-4061.2021.227001.

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A simulation model of a photoplethysmographic signal under psychoemotional stress taking into account the nature of signals of biological origin and stress response stages was developed. The method of constructing the simulation model is based on reconstructing the waveform and coding points of the signal taking into account the stress response curve using harmonic functions at characteristic time intervals. Using the simulation model of the photoplethysmographic signal under psychoemotional stress with previously known parameters allows validation of methods and algorithms for processing such data. It was found that in the process of simulation, it is necessary to take into account the signal frequency, random component and stress response curve. This complicates the simulation algorithm. However, using the simulation model with variable input parameters allows reproducing the signal with an emphasis on stress response stages. One of the features of the proposed model is the ability to reproduce the signal by coding points for amplitude and time intervals using harmonic functions. The relative error for the amplitude variation of the model and experimental data is 3.97 %, and for the period – 3.41 %. Calculation of Student's t-test showed a statistically insignificant difference: p=0.296 for the amplitude and p=0.275 for the period. This indicates that the simulation model takes into account the signal characteristics under stress: frequency, random component and stress response curve. Using the proposed simulation model is an adequate way to assess methods and algorithms for analyzing the state of the cardiovascular system under psychoemotional stress

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de Oliveira, Amanda Almeida, Josemar Faustino, Maria Elena de Lima, Ronaldo Menezes i Kenia Pedrosa Nunes. "Unveiling the Interplay between the TLR4/MD2 Complex and HSP70 in the Human Cardiovascular System: A Computational Approach". International Journal of Molecular Sciences 20, nr 13 (26.06.2019): 3121. http://dx.doi.org/10.3390/ijms20133121.

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While precise mechanisms underlying cardiovascular diseases (CVDs) are still not fully understood, previous studies suggest that the innate immune system, through Toll-like receptor 4 (TLR4), plays a crucial part in the pathways leading to these diseases, mainly because of its interplay with endogenous molecules. The Heat-shock protein 70 family (HSP70-70kDa) is of particular interest in cardiovascular tissues as it may have dual effects when interacting with TLR4 pathways. Although the hypothesis of the HSP70 family members acting as TLR4 ligands is becoming widely accepted, to date no co-crystal structure of this complex is available and it is still unknown whether this process requires the co-adaptor MD2. In this study, we aimed at investigating the interplay between the TLR4/MD2 complex and HSP70 family members in the human cardiovascular system through transcriptomic data analysis and at proposing a putative interaction model between these proteins. We report compelling evidence of correlated expression levels between TLR4 and MD2 with HSP70 cognate family members, especially in heart tissue. In our molecular docking simulations, we found that HSP70 in the ATP-bound state presents a better docking score towards the TLR4/MD2 complex compared to the ADP-bound state (−22.60 vs. −10.29 kcal/mol, respectively). Additionally, we show via a proximity ligation assay for HSP70 and TLR4, that cells stimulated with ATP have higher formation of fluorescent spots and that MD2 might be required for the complexation of these proteins. The insights provided by our computational approach are potential scaffolds for future in vivo studies investigating the interplay between the TLR4/MD2 complex and HSP70 family members in the cardiovascular system.

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Madwed, J. B., P. Albrecht, R. G. Mark i R. J. Cohen. "Low-frequency oscillations in arterial pressure and heart rate: a simple computer model". American Journal of Physiology-Heart and Circulatory Physiology 256, nr 6 (1.06.1989): H1573—H1579. http://dx.doi.org/10.1152/ajpheart.1989.256.6.h1573.

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We have previously reported that low-frequency oscillations in arterial blood pressure (ABP) and heart rate (HR) occur when conscious dogs experience severe blood loss. These low-frequency oscillations are generated by enhancement of the sympathetic nervous system and inhibition of the parasympathetic nervous system. We have developed a simple computer model to elucidate those properties critical to the generation of these oscillations. Our model incorporates several important features: 1) arterial baroreceptor feedback loops, which relate ABP to targeted HR and total peripheral resistance (TPR) values; 2) two effector outputs, HR and TPR, which are controlled by the outputs of vagal, beta-adrenergic, and alpha-adrenergic effector mechanisms; 3) a fixed beat-to-beat stroke volume; and 4) a wind-kessel model, which represents the peripheral circulation. Each effector mechanism is modeled as a low-pass filter in series with a delay. The vagal effector mechanism slows the HR after a 100-ms delay and reaches maximal HR at that time. The beta-adrenergic effector mechanism speeds HR after a 2.5-s delay and then increases to maximal HR 7.5 s later. The alpha-adrenergic effector mechanism begins vasoconstriction after a 5-s delay and then reaches maximal contraction 15 s later. Computer simulations of inhibition of the vagal effector mechanism and activation of the adrenergic effector mechanisms elicit low-frequency oscillations in ABP and HR. These oscillations are similar to those observed experimentally in the dog during hemorrhage. We conclude that the slow temporal response of the alpha-adrenergic effector mechanism controlling TPR is the critical element in predicting the observed low-frequency oscillations in ABP and HR.

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WANG, WENXIN, YOUJUN LIU, XI ZHAO, JINSHENG XIE i AIKE QIAO. "HEMODYNAMICS-BASED LONG-TERM PATENCY OF DIFFERENT SEQUENTIAL GRAFTING: A PATIENT-SPECIFIC MULTI-SCALE STUDY". Journal of Mechanics in Medicine and Biology 17, nr 01 (luty 2017): 1750017. http://dx.doi.org/10.1142/s0219519417500178.

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Background and aims: Sequential grafting is one of the common coronary artery bypass grafting (CABG) surgery. But the influence of the sequential grafting position on hemodynamics and the graft patency is still unclear. Materials and methods: The zero-dimensional/three-dimensional (0D/3D) coupling method was used to finalize the multi-scale simulation of two different sequential grafting models. First, a patient-specific 3D model was reconstructed based on coronary computed tomography angiography (CCTA) images. Two different sequential grafts were implemented on this patient-specific 3D model by using virtual surgery. Thus, two different postoperative 3D models were built. Then, a lumped parameter model (LPM; 0D) was built based on the patient physiological data to simulate the cardiovascular system. Finally, the 0D/3D coupling method was used to perform the numerical simulation by coupling a 0D LPM of the cardiovascular system and the patient-specific 3D models. Moreover, the long-term patency of these two different sequential grafts was discussed in this paper. Results: The coronary flow rate and the graft flow were calculated and illustrated. The instantaneous wave-free ratio (iFR) were calculated. Postoperative iFR values increase to over 0.90 for both sequential grafts. Some hemodynamics parameters were also illustrated, such as wall shear stress (WSS), oscillatory shear index (OSI). The area of low WSS in Model 1 was much less than that in Model 2. Two regions of high OSI exist in Model 2, while only one in Model 1. Conclusions: No significant differences exist on the short-term outcomes of two models. But the long-term patency of Model 2 was worse. The Model 1 may enhance long-term patency of grafting and should be priority when the sequential grafting need to be carried out.

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