Research results of features of an intracellular calcium homeostasis in 4 and 12-month's rat cardiomyocites at postinfarction cardiosclerosis are presented. It is shown that the myocardium of animals in the old rats group is more susceptible to extrasystolic impacts. In the pathology conditions additional extrasystolic influences also had the expressed age specificity of inotropic response. The data testifying to almost identical dynamics of postextrasystolic cycles of intact myocardium in animals of investigated age groups has been obtained. The different postextrasystolic potentiation in the remodeled myocardium in old and young rats testified to different of sarcoplasmic reticulum ability to accumulate additional calcium ions. The conclusion was made that the myocardium of animals in the old rats group has more chance for development of hemodynamic significant disturbance of cardiac rhythm as a consequence of age-related changes processes of the electromechanical coupling in cardiomyocites.