Open AccessVagal Influence on Deterministic Chaos of Heart Rate in Patients after Acute Myocardial Infarction
Author(s) -
Hagerman Inger,
Berglund Margareta,
Ericson Mats,
Sylvén Christer
Publication year - 1997
Publication title -
annals of noninvasive electrocardiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.494
H-Index - 48
eISSN - 1542-474X
pISSN - 1082-720X
DOI - 10.1111/j.1542-474x.1997.tb00202.x
Subject(s) - correlation dimension , medicine , heart rate variability , lyapunov exponent , atropine , cardiology , myocardial infarction , surrogate data , heart rate , vagal tone , linear regression , mathematics , fractal dimension , statistics , blood pressure , nonlinear system , physics , mathematical analysis , fractal , quantum mechanics
Objectives To test heart rate variability (HRV) in patients with acute myocardial infarction (AMI) for nonlinear deterministic complex behavior and for its dependence on autonomic tone. Methods Fifteen patients (mean age 55, 14 men) with AMI and 16 healthy individuals (mean age 41, 11 men) with ongoing beta‐adrenergic receptor blockade were investigated after intravenouse administration of atropine (0.03 mg/kg). Nonlinear indices for HRV were assessed by local sensitive dependence on initial conditions as quantitated by the Lyapunov exponent, fractal dimension (FD), and correlation dimension. Linear indices for HRV were assessed in the time domain by the standard deviation of the RR interval (SD‐RR), the coefficient of variation (CV%), and the mean successive difference (MSD). In the frequency domain, the following indices were used: very low frequency power (VLF), low frequency power (LF), high frequency power (HF), total power (TP), and the ratio between low and high frequency power (LF/HF). Results Surrogate data analysis revealed independent behavior of the Lyapunov exponent, the FD, and the correlation dimension, suggesting the presence of deterministic chaos in HRV. The Lyapunov exponent was positive in both groups at baseline but was significantly lower in the patient group. Following atropine, the value decreased while remaining positive, but no differences between the groups were found. The FD and the correlation dimension reacted similarly to the Lyapunov exponent. All time‐domain indices were significantly lower in the patients along with power in LF and HF bands. The differences were abolished by the administration of atropine. Conclusions The heart rate of patients with AMI exhibits characteristics of deterministic chaotic behavior with a positive Lyapunov exponent but with significantly less complex behavior than in healthy controls. The difference was eliminated by atropine, suggesting that vagal tone is a major cause. The nonlinear indices have a discriminating capacity for changes in HRV comparable to linear indices.