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Direct observation of homoclinic orbits in human heart rate variability
1Faculty of Physics, Warsaw University of Technology, Warsaw, Poland.
Insights
Homoclinic trajectories, indicative of deterministic nonlinear instabilities, were found in human heart rate variability from ECG recordings. These patterns appear in both healthy and arrhythmia-prone individuals.
Area of Science:
- Cardiology
- Nonlinear Dynamics
- Biophysics
Background:
- Human heart rate variability (HRV) is a complex physiological signal.
- Understanding the underlying dynamics of HRV is crucial for diagnosing cardiac conditions.
Purpose of the Study:
- To identify and characterize homoclinic trajectories within heart interbeat intervals.
- To investigate the role of deterministic nonlinear instabilities in human HRV.
Main Methods:
- Extraction of interbeat intervals from 24-hour Holter ECG recordings.
- Construction of iterated maps of consecutive interbeat intervals.
- Analysis of homoclinic trajectories and associated bifurcations.
Main Results:
- Homoclinic trajectories associated with hyperbolic saddles were identified in iterated interval maps.
- These trajectories were persistent, spanning thousands of heartbeats.
- Features like gluing bifurcations were observed, present in both dominant sinus rhythm and arrhythmia cases.
Conclusions:
- The presence of homoclinic trajectories strongly suggests the importance of deterministic nonlinear instabilities in human HRV.
- These findings offer new insights into the complex dynamics governing cardiac rhythm.
Abstract:
Homoclinic trajectories of the interbeat intervals between contractions of ventricles of the human heart are identified. The interbeat intervals are extracted from 24-h Holter ECG recordings. Three such recordings are discussed in detail. Mappings of the measured consecutive interbeat intervals are constructed. In the second and in some cases in the fourth iterate of the map of interbeat intervals homoclinic trajectories associated with a hyperbolic saddle are found. The homoclinic trajectories are often persistent for many interbeat intervals, sometimes spanning many thousands of heartbeats. Several features typical for homoclinic trajectories found in other systems were identified, including a signature of the gluing bifurcation. The homoclinic trajectories are present both in recordings of heart rate variability obtained from patients with an increased number of arrhythmias and in cases in which the sinus rhythm is dominant. The results presented are a strong indication of the importance of deterministic nonlinear instabilities in human heart rate variability.