[The role of Ca2+, entering the cell during reperfusion, in the mechanism of initiation and maintenance of reperfusion arrhythmias]. / Rol' Ca2+, vkhodiashchego v kletku vo vremia reperfuzii, v mekhanizme initsiatsii i podderzhaniia reperfuzionnykh aritmii.

The role of calcium ions entering cells upon reperfusion of ischemic myocardium for reperfusion arrhythmias has been investigated on the model of isolated rat right ventricle perfused through coronary artery. Manipulation by concentration of calcium ions in the reperfusion solution demonstrates that calcium ions entering cells upon reperfusion do not play a major role in the initiation of reperfusion extrasystoles and tachycardias, but have a significant influence on the maintenance of tachycardias. Multielectrode mapping revealed a focal source as the mechanism underlying reperfusion arrhythmias at low concentration or in the absence of calcium ions in the reperfusion solution.

[The defining role of calcium entering cells during ischemia as the mechanism for initiating reperfusion arrhythmias]. / Opredeliaiushchaia rol' vkhodiashchego v kletku vo vremia ishemii Ca2+ v mekhanizme initsiatsii reperfuzionnykh aritmii.

The role of calcium ions entering cells upon both reperfusion and previous ischemia for reperfusion arrhythmias has been studied on the experimental model of isolated rat right ventricle perfused through coronary artery. Manipulation by concentration of calcium ions in both perfusion and reperfusion solutions demonstrates that calcium ions entering cells during ischemia but not upon reperfusion play a dominant role in the initiation of reperfusion tachysystoles (RTS) and reperfusion extrasystoles. It is shown that mechanisms of reperfusion fibrillations (RF) are more sensitive than ones of RTS to changes of the intracellular calcium concentration. For example, RF have been easily suppressed by calcium concentration decreasing at any stage of the experiment: upon reperfusion, or during previous ischemia, whereas RTS have not been suppressed even under total removal of calcium from solutions either before initiation of ischemia or during following reperfusion. Multielectrode mapping revealed focal sources arising as the mechanism underlying not only reperfusion arrhythmias as it has been shown before [4.7] but also arrhythmias that have been observed through experiments.

[A system for computer visualization of excitation wave propagation in the myocardium]. / Sistema komp'iuternoi vizualizatsii rasprostraneniia voln vozbuzhdeniia v miokarde.

A method of computer-aided visualization of autowave vortices on the cardiac tissue surface is developed. The software for research into autowave vortex evolution is designed, which allowed an adequate presentation of excitation propagation along complex trajectories and the detection of the most essential features of excitation source behavior.

[Slow excitation waves and mechanisms of polymorphic ventricular tachycardia in an experimental model: isolated walls of the right ventricle from rabbit and squirrel]. / Medlennye volny vozbuzhdeniia i mekhanizmy polimorfnoi zheludochkovoi takhikardii v éksperimental'noi modeli: izolirovannye stenki pravogozheludochka krolika i suslika.

The mechanism of polymorphic disturbances of the heart rhythm is studied on an experimental model, isolated ventricular preparations of ground squirrel and rabbit. Polymorphic arrhythmias are identified from habitus of the isolated preparation pseudoECGs mathematically derived from electrograms registered simultaneously at 32 endocardial and 32 epicardial points. The same electrograms allow one to visualize the excitation wave propagation along each of the preparation surfaces. The comparison of excitation wave pictures and corresponding pseudoECGs enabled us to reveal the conditions necessary and sufficient for polymorphism in heart rhythm disturbances. Polymorphic arrhythmias are due to changes in wave pictures in the regions of retarded excitation propagation.

[Isolated right ventricle after coronary perfusion as a model for the study of ischemic and reperfusion-induced arrhythmia in rats]. / Izolirovannyi koronarno-perfuziruemyi pravyi zheludochek krysy kak model' dlia issledovaniia ishemicheskikh i reperfuzionnykh aritmii.

A catheter through which perfusion was performed with oxygenated saline (2.1 ml/min) was introduced into the right coronary artery ostium of the rat right ventricle that had been isolated during cardioplegia. Super perfusion (12 ml/min) was simultaneously made. Termination of the perfusion caused arrhythmias at minutes 6 to 28 of ischemia. The highest likelihood of occurrence of such arrhythmias was observed on minutes 16-20 (premature beats being seen in 86% of the experiments, extrastimulus-induced tachycardias in 75%, spontaneous tachycardias in 25%). Reperfusion was made at 3, 5, 7, 10, 13, 15, 20, 30 and 60 min following ischemia (n = 7 in each case). The occurrence of reperfusion arrhythmias is likely to be related to the duration of ischemia with the highest likelihood of 20 minutes after ischemia (tachycardia and fibrillation were observed in 100 and 71%, respectively).