The analysis of transitions between linear and nonlinear regimes of cardiorhythm at patiens with the ischemic heart disease

Abstract

In our previous researches performed by a mathematical modeling method, it has been shown that at increased extracardial impulsation arriving on heart, saltatory transitions between various regimes of cardiodynamics take place: linear regimens are replaced by chaotic ones with different characteistics of heart
rate irregularity and cardiac electrical stability. The study of transitions between linear and nonlinear regimens of cardiodynamics has the important clinical value as depression of cardiac electrical stability is one of the reasons occurrence of arrhythmias and rising of mortality from cardiovascular diseases. The patients with ischemic heart disease belong to the group of the patients that require special attention to prevent fatal arrhythmia development. That is why the purpose of the present work was the application of the results of mathematical modeling to studying transitions between linear and nonlinear regimes of cardiodynamics in patients with ischemic heart disease. Nonlinear heart rate dynamics in patients with ischemic heart disease was studied by daily ECG monitoring on the "General Electric" apparatus (USA). Stability of time series of RR intervals was estimated on a critical cardiodynamics transition point from stable linear to chaotic mode. The linear regimes of cardiodynamics was meant as a mode with a stable sinus rhythm whereas the nonlinear (chaotic) regime was considered as a mode at which various kinds of extrasystoles were registered. It is shown that, in patients with ischemic heart disease upon gradual growth of the heart rate at a critical Fcr point, there was a saltatory transition from linear to chaotic regimes of cardiodynamics characterized by depression of degree of ordering and stability of the heart rate. Existence of a critical Fcr point sep a rating linear and nonlinear regimes of cardiodynamics in patients with ischemic heart disease is in accordance with the theoretical results received earlier by us using a mathematical modeling method.