[Effect of stretch of the electric activity of human myocardial cells].

The effects of cyclic deformation (0.03-0.3 mm/S) on electrical activity was examined on an isolated myocardium of patients suffering from mitral stenosis and congenital septal heart diseases. The muscle deformation was shown to decrease prepotential (the first component) and spike (the second component) amplitudes of double component action potentials which were specific for the pathological myocardium under study. It was also found that appearance of the second component was delayed in the course of deformation and almost ceased after deformation reached certain level. The delay of appearance of the second component was followed by the emergence of the second twitch that was similar to the extrasystolic one. Disappearance of the second component produced a decrease in contractility. When action potentials recorded were typical of the normal myocardium, they manifested no changes even upon a significant stretch. It is suggested that high sensitivity to stretch of the double component action potentials depends on conduction disturbances seen in the pathological myocardium.