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Progress toward controlling in vivo fibrillating sheep atria using a nonlinear-dynamics-based closed-loop feedback
Daniel J. Gauthier1, G. Martin Hall, Robert A. Oliver
1Department of Physics and Department of Biomedical Engineering, Duke University and Center for Nonlinear and Complex Systems, Box 90305, Durham, North Carolina 27708.
Chaos (Woodbury, N.Y.)
|June 5, 2003
Summary
This study explored controlling atrial fibrillation in sheep using closed-loop feedback pacing. The protocol aimed to regularize heart rhythms but was found ineffective due to refractory period issues.
Area of Science:
- Cardiovascular Physiology
- Biomedical Engineering
- Control Systems
Background:
- Atrial fibrillation (AF) is a complex cardiac arrhythmia.
- Controlling cardiac dynamics in vivo presents significant challenges.
- Physiologically relevant models are crucial for developing effective interventions.
Purpose of the Study:
- To investigate the feasibility of controlling in vivo atrial fibrillation using a closed-loop feedback protocol.
- To assess the effectiveness of pacing interventions in regularizing cardiac dynamics.
- To explore the application of control algorithms in a physiologically relevant cardiac preparation.
Main Methods:
- Utilized a closed-loop feedback system to monitor and control sheep atrial dynamics.
- Applied single-site electrical pacing perturbations to suppress fibrillation.
- Measured spatial-temporal responses using a multi-channel electronic recording system.
- Employed a control algorithm to adjust shock timing based on inter-activation intervals.
Main Results:
- The closed-loop feedback protocol was not effective in regularizing atrial fibrillation dynamics.
- The control system often attempted to pace the atrium during its refractory period, failing to induce activation.
- Probability distributions indicated a lack of significant regularization of inter-activation time intervals.
Conclusions:
- The described single-sided pacing feedback protocol failed to suppress or regularize in vivo atrial fibrillation in sheep.
- The refractory period of cardiac tissue poses a significant challenge for real-time feedback control systems.
- Further research is needed to refine control strategies for cardiac arrhythmias, potentially involving dual-sided pacing or alternative sensing methods.