Dependence of Intramyocardial Pressure and Coronary Flow on Ventricular Loading and Contractility: A Model Study

Abstract

Abstract-The phasic coronary arterial inflow during the normal cardiac cycle has been explained with simple (waterfall, intramyocardial pump) models, emphasizing the role of ventricular pressure. To explain changes in isovolumic and low afterload beats, these models were extended with the effect of three-dimensional wall stress, nonlinear characteristics of the coronary bed, and extravascular fluid exchange. With the associated increase in the number of model parameters, a detailed parameter sensitivity analysis has become difficult. Therefore we investigated the primary relations between ventricular pressure and volume, wall stress, intramyocardial pressure and coronary blood flow, with a mathematical model with a limited number of parameters. The model replicates several experimental observations: the phasic character of coronary inflow is virtually independent of maximum ventricular pressure, the amplitude of the coronary flow signal varies about proportionally with cardiac contractility, and intramyocardial pressure in the ventricular wall may exceed ventricular pressure. A parameter sensitivity analysis shows that the normalized amplitude of coronary inflow is mainly determined by contractility, reflected in ventricular pressure and, at low ventricular volumes, radial wall stress. Normalized flow amplitude is less sensitive to myocardial coronary compliance and resistance, and to the relation between active fiber stress, time, and sarcomere shortening velocity.

Inverse problems in reduced order models of cardiovascular haemodynamics: aspects of data assimilation and heart rate variability

“…The model of single-ventricle physiology adopted in this study is presented in [17] and employs the one-fibre model [38,39] to describe the heart chambers and an extension to the valve model of [40] presented in [17]. The main motivation for such model choices is that they are based on physically meaningful parameters such as wall volumes of the heart chambers, effective areas of the valves, sarcomere properties, etc., for which clinical/experimental estimates are available.…”

A tissue-level electromechanical model of the left ventricle: Application to the analysis of intraventricular pressure

“…The simulation is based on parameter values from the literature: i) cellular automata parameters were adjusted to fit electrical activation times from (Durrer 20 20 et al 1970), ii) the activation duration was set to 400ms (Bovendeerd, Borsje et al 2006) and iii) the maximum level of EMDF is fixed at 7 µM (Kerckhoffs, Bovendeerd et al 2003). Some parameter values can be varied to test the behaviour of the model.…”

“…In this sense, the interpretation of the electromechanical parameters in our model will be limited to the analysis of the relative contribution of each segment to the whole ventricular activity by means of the tuning parameter T. It should be noticed that such an analytic approach has been already used in tissue-level models of the whole organ (Bovendeerd et al 2006), showing a good correspondence with organ and system-level data.…”

A Tissue-Level Electromechanical Model of the Left Ventricle: Application to the Analysis of Intraventricular Pressure

“…Although, this description remains simple, we consider it is accurate enough for this study, as the aim is to investigate the influence of the asynchronous electromechanical function of myocardial segments on ventricular pressure. In this sense, the interpretation of the electromechanical parameters in our model will be limited to the analysis of the relative contribution of each segment to the whole ventricular activity by means of the tuning parameter T. It should be noticed that such an analytic approach has been already used in tissue-level models of the whole organ (Bovendeerd et al 2006), showing a good correspondence with organ and system-level data.…”