It is important to simulate the excitation propagation process of cardiac bio-electricity in the research of ECG forward problem. Traditional methods describe them with wave simulation algorithm such as LFX simulation algorithm and vector propagation algorithm etc, these methods have some problems to certain extent, due to the presence of discreteness of space and time and asymmetry of the myocardium. This paper discussed the simulation algorithm in 2-dimension space under the circumstance of layered and non-layered structure of myocardium. By calculating the theoretic values of simulating time based on Huygen's principle, we found that there were errors in LFX algorithm and no errors in vector propagation algorithm under the circumstance of non-layered structure of the myocardium, no mater what myocardium is isotropic or anisotropic. However, there exist errors from both algorithms when the myocardium has the layered structure. An improved algorithm is proposed and the simulations have been performed to examine the efficacy of the new algorithm, and the errors are reduced obviously. By increasing the number of myocardial blocks in the model, we also analyzed its influence on the error of simulation algorithm.
Algorithms ; Computer Simulation ; Heart ; physiology ; Models, Cardiovascular

This article introduces the significance, methods and applications in human pulse study, with an emphasis on the history, current situation and progress of pulse system modeling and pulse signal analysis. The problems in present study and the methods for the future investigations were analyzed.
Heart Rate ; Humans ; Models, Cardiovascular ; Research ; trends

Torsades de Pointes is a kind of severe ventricular arrhythmia. Myocardial ischaemia is one of the major causes leading to TdP. In this paper the mechanisms of the TdP were quantitatively studied under the condition of ischaemia based on the Noble98 dynamic model of the ventricular action potential. The study was conducted on one-dimensional homogeneous myocardium with the method of computer simulation. The models were firstly developed to simulate the lower excitability, extracellular accumulation of the K+ concentration or the decreased gap junctions in ischaemic myocardium. By separately reducing the Na+ conductance, increasing the extracellular K+ concentration or decreasing the conductance of the gap junctions enabled us to study the effect of each change in isolation. Then different degrees of ischaemic models were established to study their physiological features. The study showed that the conduction velocity became slower with the ischaemia aggravation, the action potential duration became shorter and the width of the vulnerable window obviously became larger than the normal conditions. The results illustrated that ischaemia was easily leading to unidirectional conduction block and resulted in re-entry and arrhythmias.
Computer Simulation ; Models, Cardiovascular ; Myocardial Ischemia ; physiopathology

Heart Failure ; Humans ; Models, Cardiovascular ; Prognosis

Based on the noninvasive detection indeices and fuzzy mathematics method, this paper studied the noninvasive, convenient and economical cardiovascular health assessment system. The health evaluation index of cardiovascular function was built based on the internationally recognized risk factors of cardiovascular disease and the noninvasive detection index. The weight of 12 indexes was completed by the analytic hierarchy process, and the consistency test was passed. The membership function, evaluation matrix and evaluation model were built by fuzzy mathematics. The introducted methods enhanced the scientificity of the evaluation system. Through the Kappa consistency test, McNemer statistical results ( = 0.995 > 0.05) and Kappa values (Kappa = 0.616, < 0.001) suggest that the comprehensive evaluation results of model in this paper are relatively consistent with the clinical, which is of certain scientific significance for the early detection of cardiovascular diseases.
Cardiovascular Diseases ; diagnosis ; Cardiovascular System ; Fuzzy Logic ; Humans ; Models, Cardiovascular ; Research

PURPOSE: We developed a numerical model that predicts cardiovascular system response to hemodialysis, focusing on the effect of sodium profile during treatment. MATERIALS and METHODS: The model consists of a 2-compartment solute kinetics model, 3-compartment body fluid model, and 12-lumped-parameter representation of the cardiovascular circulation model connected to set-point models of the arterial baroreflexes. The solute kinetics model includes the dynamics of solutes in the intracellular and extracellular pools and a fluid balance model for the intracellular, interstitial, and plasma volumes. Perturbation due to hemodialysis treatment induces a pressure change in the blood vessels and the arterial baroreceptors then trigger control mechanisms (autoregulation system). These in turn alter heart rate, systemic arterial resistance, and cardiac contractility. The model parameters are based largely on the reported values. RESULTS: We present the results obtained by numerical simulations of cardiovascular response during hemodialysis with 3 different dialysate sodium concentration profiles. In each case, dialysate sodium concentration profile was first calculated using an inverse algorithm according to plasma sodium concentration profiles, and then the percentage changes in each compartment pressure, heart rate, and systolic ventricular compliance and systemic arterial resistance during hemodialysis were determined. A plasma concentration with an upward convex curve profile produced a cardiovascular response more stable than linear or downward convex curves. CONCLUSION: By conducting numerical tests of dialysis/cardivascular models for various treatment profiles and creating a database from the results, it should be possible to estimate an optimal sodium profile for each patient.
Blood Pressure/drug effects ; Cardiovascular System/*drug effects ; *Computer Simulation ; Models, Cardiovascular ; *Renal Dialysis ; Sodium/*pharmacology

In order to study the cardiovascular hemodynamic characteristics and evaluate the blood pump, we made a series of cardiovascular simulation devices which could reflect the hemodynamics of blood circulation system by the elastic chamber model, and tested the relations between cardiovascular hemodynamic parameters (such as systole pressure, diastole pressure, average pressure, pulsative pressure, flow rate) and ventricular afterload (peripheral resistance and vascular compliance) as well as cardiac output, diastolic period, systole period and preload. The effect of the parameters on the arterial pressure and flow rate was estimated when any one of the parameters was changed. The result of simulating experiment was coincided with that deduced from mathematical model and physiologic condition. Therefore the series of cardiovascular simulation devices can reflect the hemodynamics of blood circulation.
Blood Pressure ; physiology ; Cardiac Output ; physiology ; Cardiovascular Physiological Phenomena ; In Vitro Techniques ; Models, Cardiovascular ; Vascular Resistance ; physiology

In order to study the cardiovascular hemodynamic characteristics and evaluate the artificial heart, especially the compression cardiac assist devices, we put forward a simulating device which is made of pump, valve, tubes and controller, and can be used to imitate cardiovascular system. Moreover, in this essay, we put forth an algorithm to draw pressure-volume loop with the parameters measured, including liquid pressure, volume and air pressure. The changes in the frequency and duty of control signal and in the angle of proportional valve can symbolize cardiovascular system in different heart rates, with different systole period, and at different level, respectively. The result of simulating device experiment proved to be coincident with physiology.
Cardiovascular Physiological Phenomena ; Computer Simulation ; Equipment Design ; Heart, Artificial ; Heart-Assist Devices ; Hemodynamics ; Models, Cardiovascular

Cardiac deficiency of qi(vital energy) is one of the main syndromes in terms of TCM (Traditional Chinese Medicine). Based on our analysis of blood-tissue fluid circulation, we set up a hemodynamics model describing cardiac deficiency of qi. The model's theoretical results can reflect the manifestations of cardiac deficiency of qi, and are identical to those of clinical experimental discoveries, therefore it has substantiated our theory-cell's abnormal physiological function caused by undernourishment of tissue fluid is the reason of qi-deficiency.
Animals ; Cardiovascular Diseases ; physiopathology ; Hemodynamics ; physiology ; Humans ; Medicine, Chinese Traditional ; Models, Cardiovascular ; Qi ; Rabbits

The implantation of biventricular assist device (BiVAD) is more challenging than that of left ventricular assist device for the interaction in the process of multiple input and output. Besides, ventricular assist device (VAD) often runs in constant speed (CS) mode in clinical use and thus BiVAD also faces the problems of low pulsation and imbalance of blood volume between systemic circulation and pulmonary circulation. In this paper, a delay assist mode for a VAD by shortening the support time of VAD was put forward. Then, the effect of the delay mode on cardiac output, pulsation and the function of the aortic valve was observed by numerical method and the rules of hemodynamics were revealed. The research showed that compared with VAD supported in CS mode, the VAD using delay mode in systolic and diastolic period proposed in this paper could meet the demand of cardiac output perfusion and restore the function of the arterial valves. The open ratio of aortic valve (AV) and pulmonary valve (PV) increased with the time set in delay mode, and the blood through the AV/PV helped to balance the left and the right cardiac volume. Besides, delay mode also improved the pulsation index of arterial blood flow, which is conducive to the recovery of the ventricular pulse function of patients.
Cardiovascular System ; Diastole ; Heart Failure ; Heart Rate ; Heart-Assist Devices ; Hemodynamics ; Humans ; Models, Cardiovascular