Mycardial ischemia and determined chaos in integral homeostatic regulation.

This study was devoted to the problem of homeostatic stability loss caused by myocardial ischemia, induced by stress testing. It involved 55 patients with different variants of coronary heart disease and 15 practically healthy volunteers as controls. Routine bicycle ergometry and nonstop monitoring of the cardiac-interval duration were conducted simultaneously. The systemic homeokinetic state was evaluated by means of cardiac rhythm entropy dynamics analysis in a multidimensional space of existence. Determined chaos was shown to be the main property of these dynamics in all cases. The original method of measuring the cardiac rhythm entropy chaotisity level is presented. It is suggested that the newly revealed phenomenon of a sharp rise in the cardiac entropy trajectory chaotisity level and followed by a decrease, which happens in the multidimensional phase space, may be used as an additional criterion of myocardial ischemia development for the verification of dubious stress-testing results.