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Origin of chaos in the circulation: open loop analysis with an artificial heart
T Yambe1, S Nanka, S Kobayashi
1Department of Medical Engineering and Cardiology, Institute of Development, Aging and Cancer, Tohoku University, Sendai, Japan.
Insights
This study reveals that chaotic dynamics in the cardiovascular system originate from blood vessels and sympathetic activity, crucial for developing artificial heart control algorithms. These findings highlight the central nervous system's role in cardiovascular chaos.
Area of Science:
- Cardiovascular Physiology
- Nonlinear Dynamics
- Biomedical Engineering
Background:
- The cardiovascular system is a complex system with intricate feedback loops, making the origin of its chaotic dynamics challenging to pinpoint.
- Understanding these dynamics is crucial for developing optimal control algorithms for artificial heart systems.
- Chaotic dynamics in the cardiovascular system have garnered significant clinical interest.
Purpose of the Study:
- To investigate the origin of chaos within the cardiovascular system.
- To identify the specific components responsible for generating chaotic dynamics.
- To inform the development of advanced automatic control algorithms for artificial hearts.
Main Methods:
- Open-loop analysis using an artificial heart in chronic animal experiments (goats) to eliminate pumping rate fluctuations.
- Nonlinear mathematical analysis of circulatory time series data.
- Direct measurement of sympathetic activity and analysis of action potentials.
- Mutual information analysis to assess coupling between physiological variables.
Main Results:
- Low-dimensional deterministic chaos was identified in artificial heart circulatory time series data, implicating blood vessels as a key source.
- Chaotic dynamics were also observed in sympathetic action potentials during artificial heart circulation.
- A significant coupling of nonlinear information between blood vessels and sympathetic activity was detected.
- The central nervous system (CNS) plays a critical role in cardiovascular chaotic dynamics via sympathetic activity.
Conclusions:
- Blood vessels are a significant contributor to the chaotic dynamics observed in the cardiovascular system.
- Sympathetic activity, modulated by the central nervous system, is intrinsically chaotic and coupled with vascular dynamics.
- These findings provide essential insights for designing sophisticated automatic control algorithms for artificial hearts.
Abstract:
To develop the optimal automatic control algorithm for an in vivo artificial heart system, investigation of the basic characteristics of the cardiovascular system may be important. The clinical significance of chaotic dynamics in the cardiovascular system has attracted attention. The circulation is a so-called complex system with many feedback circuits, making it very difficult to investigate the origin of chaos within the system. In this study, we investigated the origin of chaos by open loop analysis with an artificial heart (which has no fluctuation in pumping rate or contraction power) in chronic animal experiments with healthy adult goats. As a result, in the artificial heart circulatory time series data, low dimensional deterministic chaos was discovered by nonlinear mathematical analysis, suggesting the importance of blood vessels in the chaotic dynamics of the cardiovascular system. To investigate the origin of chaos further, sympathetic activity was directly measured in animals with artificial hearts. Chaotic dynamics was also recognized in sympathetic action potentials, even during artificial heart circulation. Coupling of the nonlinear information between blood vessels and sympathetic activity was suggested by analysis of mutual information. In chaotic dynamics, the central nervous system (CNS) played an important role through sympathetic activity. These findings may be useful for the development of an automatic control algorithm for an artificial heart.