[Modeling of disturbances in electrical and mechanical function of cardiomyocytes under acute ischemia].

The effect of acute myocardial ischemia on the electrical and mechanical function of cardiomyocytes was studied in the framework of a mathematical model of a single cardiomyocyte. Acute ischemia consequences were simulated via a combination of two factors--a reduction of intracellular ATP concentration and an increase in extracellular potassium concentration, which affect the kinetics of ATP-sensitive potassium current and other potassium currents. In accord with experimental data, ischemic models produce action potential shortening and diastolic depolarization, which reduce contractile, ability of cardiomyocytes, Utilizing a 'difference-current integral' approach, we assessed quantitative contribution of ionic currents to changes in the action potential generation during ischemic injuries. It has been shown that an increase in the amplitude of inward rectifier potassium current I(K1) with increased extracellular potassium concentration has most essential contribution to the changes in the action potential duration under ischemia.

The cardiac muscle duplex as a method to study myocardial heterogeneity.

This paper reviews the development and application of paired muscle preparations, called duplex, for the investigation of mechanisms and consequences of intra-myocardial electro-mechanical heterogeneity. We illustrate the utility of the underlying combined experimental and computational approach for conceptual development and integration of basic science insight with clinically relevant settings, using previously published and new data. Directions for further study are identified.

[Mathematical models for the study of electromechanical and mechanoelectrical coupling in the myocardium].

Mathematical models have been developed to describe interactions of electrical, mechanical and chemical processes in cardiomyocytes. The models simulate wide range of experimental data on excitation-contraction coupling and, more importantly, on mechanoelectric feedback in heart muscle. The model results clearly show that mechano-dependence of intracellular calcium handling due to cooperative effects of contractile proteins activation plays a key role in cardiac mechanoelectric coupling. At the same time, mechanosensitive currents can also contribute to action potential responses to mechanical perturbations. Using this model to study the heterogeneous myocardium we have shown that temporal and functional electromechanical heterogeneity of coupled cardiomyocytes can essentially determine the myocardium contractility. Optimization of the electromechanical function of contractile system emerges from the fine coordination between the activation sequence of cardiomyocytes, their local electromechanical properties and the mechanical interaction during contraction.