THE DETERMINING ROLE OF CA2+ ENTERING CEL LS IN THE COURSE OF ISCHEMIA IN THE MECHANISM OF REPERFUSION ARRHYTHMIA INITIATION

The role of calcium ions entering cells upon both reperfusion and prev ious ischemia for reperfusion arrhythmias has been studied on the expe rimental model of isolated rat right ventricle perfused through corona ry artery. Manipulation by concentration of calcium ions in both perfu sion and reperfusion solutions demonstrates that calcium ions entering cells during ishemia but not upon reperfusion play a dominant role in the initiation of reperfusion tachysystolias (RTS) and reperfusion ex trasystolias. It is shown that mechanisms of reperfusion fibrillations (RF) are more sensitive than ones of RTS to changes of the intracellu lar calcium concentration. For example, RF have been easily suppressed by calcium concentration decreasing at any stage of the experiment: u pon reperfusion, or during previous ischemia, whereas RTS have not bee n suppressed even under total removal of calcium from solutions either before initiation of ischemia or during following reperfusion. Multie lectrode mapping revealed focal sources arising as the mechanism under lying not only reperfusion arrhythmias as it has been shown before [4, 7] but also arrhythmias that have been observed through experiments.