Vladimir I. Gridnev

Active ambulatory care management supported by short message services and mobile phone technology in patients with arterial hypertension

The use of short message services and mobile phone technology for ambulatory care management is the most accessible and most inexpensive way to transition from traditional ambulatory care management to active ambulatory care management in patients with arterial hypertension (AH). The aim of this study was to compare the clinical efficacy of active ambulatory care management supported by short message services and mobile phone technology with traditional ambulatory care management in AH patients. The study included 97 hypertensive patients under active ambulatory care management and 102 patients under traditional ambulatory care management. Blood pressure levels, body mass, and smoking history of patients were analyzed in the study. The duration of study was 1 year. In the active ambulatory care management group, 36% of patients were withdrawn from the study within a year. At the end of the year, 77% of patients from the active care management group had achieved the goal blood pressure level. That was more than 5 times higher than that in the traditional ambulatory care management group (P < .001). The risk ratio of achieving and maintaining the goal blood pressure in patients of active care management group was 5.44, CI (3.2-9.9; P = .005). Implementation of active ambulatory care management supported by short message services and mobile phone improves the quality of ambulatory care of hypertensive patients.

Synchronization of low-frequency oscillations in the human cardiovascular system.

We investigate synchronization between the low-frequency oscillations of heart rate and blood pressure having in humans a basic frequency close to 0.1 Hz. A method is proposed for quantitative estimation of synchronization between these oscillating processes based on calculation of relative time of phase synchronization of oscillations. It is shown that healthy subjects exhibit on average substantially longer epochs of internal synchronization between the low-frequency oscillations in heart rate and blood pressure than patients after acute myocardial infarction.

Evaluation of 5‐Year Risk of Cardiovascular Events in Patients after Acute Myocardial Infarction Using Synchronization of 0.1‐Hz Rhythms in Cardiovascular System

Background: Synchronization between 0.1‐Hz rhythms in cardiovascular system is deteriorated at acute myocardial infarction (AMI) leading to a disruption of natural functional couplings within the system of autonomic regulation.

[Internal synchronization of the main 0.1-Hz rhythms in the autonomic control of the cardiovascular system].

Synchronization parameters of 0.1-Hz rhythms isolated from the heart rate and the oscillations of the blood volume in microcirculatory vessels were studied in 12 healthy subjects and 32 patients with acute myocardial infarction. Recordings of the electrocardiogram and the pulsogram from the distal phalanx of the index finger, as well as mechanical recording of respiration with the body in a horizontal position, were performed. In patients with myocardial infarction, the recordings were performed during the first three to five days and the third week after the infarction. Synchronization was tested by plotting phase differences and calculating the total percentage of phase synchronization. Synchronization parameters of 0.1-Hz rhythms were high in healthy subjects. In patients with acute myocardial infarction, synchronization of 0.1-Hz rhythms was considerably poorer. The data obtained suggest that the studied 0.1-Hz rhythms are two independent oscillatory processes that are synchronized in healthy subjects. However, this interaction may be disturbed in cardiovascular pathologies, e.g., myocardial infarction.

Diagnostic of cardio-vascular disease with help of largest Lyapunov exponent of RR-sequences

Abstract We suggest to present a discrete sequence of cardiointervals in the form of a smooth time dependence and for the given time series compute the largest Lyapunov exponent. Processing the database with RR-intervals of patients suffering from coronary artery disease (CAD) has shown that the largest Lyapunov exponent can be a diagnostic criteria allowing one to distinguish between different groups of patients with more confidence than the standard methods for time series processing accepted in cardiology.

Phase and frequency locking of 0.1-Hz oscillations in heart rate and baroreflex control of blood pressure by breathing of linearly varying frequency as determined in healthy subjects

Functional interaction was studied between the subsystems that ensure autonomic control of the heart rate (HR) and blood pressure (BP) and give rise to 0.1-Hz oscillations in R-R intervals (RRI) and photoplethysmogram (PPG). Twenty-five recordings were obtained from 18- to 32-year-old healthy persons (six women and nineteen men). The RRI and PPG were recorded simultaneously while the respiration rate of a subject in the sitting position increased linearly from 0.05 Hz to 0.25 Hz within 25 min. Phase and frequency locking of 0.1-Hz oscillations by breathing proved to be possible in both RRI and PPG. The intervals of phase and frequency locking of oscillations by respiration differed in duration and relative position. These distinctions suggest that the mechanisms of autonomic 0.1-Hz control of HR and BP are functionally independent.

Selection of optimal dose of beta-blocker treatment in myocardial infarction patients based on changes in synchronization between 0.1 Hz oscillations in heart rate and peripheral microcirculation.

Background Selection of the optimal dose of beta-blocker treatment in myocardial infarction (MI) patients is problematic because of a lack of well-established guidelines. Methods We evaluated changes in synchronization between 0.1 Hz oscillations in heart rate (HR) and plethysmographic peripheral microcirculation in response to a tilt-table test and to 3-month treatment with the highest tolerated beta-blocker (metoprolol) dose in 43 patients aged between 41 and 77 years with acute MI 6 months prior to the start of the study. Before the study the patients were treated with small doses of beta-blocker. Phase differences between HR and peripheral microcirculation oscillations were used to measure the degree of synchronization (S), and relative change in S from horizontal position was used to characterize the response to vertical tilt. Results Two groups of MI patients matched for clinical characteristics were identified on the basis of the results. The first group was composed of patients with decreased S as a response to vertical tilt at the beginning of the study. The patients with increased S during vertical tilt before treatment with the highest tolerated beta-blocker dose were attributed to the second group. The response to vertical tilt in the first group of patients was postulated to indicate the need to increase beta-blocker dose, and in turn, the response in the second group to indicate an already adequate beta-blocker dose. Conclusion Assessment of synchronization of 0.1 Hz HR and peripheral microcirculation oscillations as a response to a tilt test can possibly be used as a guideline for selecting beta-blocker dose in post-MI patients.

Influence of external periodic stimuli on heart rate variability in healthy subjects and in coronary heart disease patients

Frequency estimates of the heart rate variability (HRV) spectrum influenced by external periodic stimuli were studied in healthy subjects and patients with coronary heart disease (CHD). Sensory stimulation by periodic eye opening at a rate of 15, 10, 8, 6, or 5 times per minute, as well as spontaneous and controlled breathing at a rate of 15, 10, 8, 6, or 5 times per minute, was used. It was found that the spectral response to external periodic oscillations was determined by a frequency-dependent phenomenon, the maximal amplitude of heart rate variations being observed in the case of external stimuli at a frequency of 0.1 Hz. A resonance frequency in the 0.1-Hz range may be suggested to exist in the cardiovascular controls. Significant differences in the HRV frequency characteristics between CHD patients and healthy subjects were shown. CHD patients had a characteristic decline in HRV responses to external oscillations; the power of these responses did not depend on the frequency of external stimuli.

Interaction of 0.1-Hz oscillations in heart rate variability and distal blood flow variability

Biophysical features of 0.1-Hz oscillations of heart rate variability (HRV) and distal blood flow (DBF) variability were compared in healthy subjects and patients after acute myocardial infarction (MI). Patients with acute MI (72 men and 53 women; 125 in total) and healthy subjects (23 men and 10 women; 33 in total) aged 30–83 and 20–46 years, respectively, participated in the study. The patients were involved in the study for a year after acute MI. The delay in coupling 0.1-Hz oscillations of HRV and DBF variability was estimated. In healthy subjects, the delay in the heart → DBF coupling proved to be less than the delay in the DBF → heart coupling. Acute MI results mainly in disruption of the heart → DBF coupling, which is partially restored by the end of the first year after acute MI, though it remains lower than in healthy subjects. The DBF → heart coupling is rapidly restored to the level of healthy subjects within three weeks after acute MI.

Mechanisms of Periodic Heart Rate Oscillations: A Study Using Controlled Breathing Tests

An orthostatic test with frequency-controlled breathing (with periods of 4, 6, 8, 10, and 12 s) was used to analyze frequency estimates of the heart rate variability (HRV) spectrum in the low frequency (LF) and high frequency (HF) ranges in 36 volunteers (26 men and 10 women) aged 19–21 years without signs of heart or respiratory pathology. The subjects took a breath at the moment of an auditory signal. There were no other requirements for the respiration rhythm. Variables were compared using Wilcoxon’s test for pairwise comparisons; correlations were estimated by Spearman’s rank correlation R test. The sensitivities of the LF and HF ranges of the HRV spectrum to periodic respiratory perturbations at different frequencies were demonstrated to differ from each other. Autonomous 0.10- and 0.25-Hz circuits of oscillatory processes were found in HRV. The transition zone of influence of these circuits was located in the region around 0.125 Hz. The characteristics of the 0.10- and 0.25-Hz oscillations in HRV were studied. It was demonstrated that the 0.10-Hz oscillatory process is a potent mechanism of heart rate control, is affected by external factors, and determines the dynamics of the autonomic nervous state of the body, while the 0.25-Hz process is a regulatory mechanism of medium strength, is resistant to external factors, and characterizes the adaptation reserve of the autonomic nervous control of the heart rate, as well as the autonomic nervous state of the body. Resonance responses in the HRV spec-trum can be used for studying the characteristics of the 0.10- and 0.25-Hz oscillations.