Investigation of statistical characteristics of interaction between the low-frequency oscillations in heart rate variability and peripheral microcirculation in healthy subjects and myocardial infarction patients

Objective. This study compares the statistical characteristics of interaction between 0.1 Hz oscillations in heart rate variability (HRV) and photoplethysmogram (PPG) in healthy subjects and myocardial infarction (Ml) patients. Material and methods. We studied 23 healthy subjects (20 men and 3 women aged 26±3 years) and 23 patients (12 men and 11 women aged 52±4 years) at about one month after Ml. The 10-minute signals of simultaneously recorded cardioin-tervalogram (CIG) and PPG were studied. We calculated the total percentage of phase synchronization between the studied 0.1 Hz oscillations and estimated the distribution functions of duration of synchronous and non-synchronous epochs, the variability of basic frequency of oscillations, and variance of phase noises in 0.1 Hz oscillations in HRV and PPG. Results. The total percentage of phase synchronization between 0.1 Hz oscillations is significantly greater in healthy subjects than in Ml patients (47±3% and 26±4%, respectively). Significant difference between these two groups in the distribution of duration of synchronous and non-synchronous epochs was not revealed. The Ml patients had greater variance between the basic frequencies of 0.1 Hz oscillations in HRV and PPG than healthy subjects. This phenomenon correlates with the increased level of phase noises in the records of Ml patients. Conclusion. The quality of synchronization between 0.1 Hz oscillations in HRV and PPG is associated with the strength of influence of external factors (noises) and variability of the basic frequency of these oscillations.