Low-frequency component of photoplethysmogram reflects the autonomic control of blood pressure.

The question of how much information the photoplethysmogram (PPG) signal contains on the autonomic regulation of blood pressure (BP) remains unsolved. This study aims to compare the low-frequency (LF) and high-frequency components of PPG and BP and assess their correlation with oscillations in interbeat (RR) intervals at similar frequencies. The PPG signal from the distal phalanx of the right index finger recorded using a reflective PPG sensor at green light, the BP signal from the left hand recorded using a Finometer, and RR intervals were analyzed. These signals were simultaneously recorded within 15 min in a supine resting condition in 17 healthy subjects (12 males and 5 females) aged 33 ± 9 years (mean ± SD). The study revealed the high coherence of LF components of PPG and BP with the LF component of RR intervals. The high-frequency components of these signals had low coherence. The analysis of the signal instantaneous phases revealed the presence of high-phase coherence between the LF components of PPG and BP. It is shown that the LF component of PPG is determined not only by local myogenic activity but also reflects the processes of autonomic control of BP.

Discrepancy between the European clinical guidelines and myocardial revascularization in patients with stable coronary artery disease in Russia.

OBJECTIVE: In European Society of Cardiology/European Association for Cardio-Thoracic Surgery (ESC/EACTS) guidelines, six indications have been proposed for making a decision on myocardial revascularization in patients with stable coronary artery disease (CAD). Our aim was to study a discrepancy between the actual clinical situation and ESC/EACTS indications on performing the revascularization in patients with CAD in Russia. DESIGN AND SETTING: We used retrospective clinical data on patients with stable CAD enrolled in the 2012-2015 Russian Registry of Hypertension, Coronary Artery Disease, and Chronic Heart Failure. PARTICIPANTS: A total of 1522 patients with CAD (aged 53.0 ± 8.5 years, 76.2% male) were used for analysis. INTERVENTIONS: All patients were divided into two groups: 591 patients with performed myocardial revascularization (named as R-CAD) and 931 patients refused from revascularization (named as NR-CAD). Factors associated with revascularization performance were identified by discriminant function analysis. MAIN OUTCOME MEASURES: ESC/EACTS indications for revascularization were assessed. RESULTS: A total of 1196 patients with CAD had any ESC/EACTS indication for revascularization, but only 40.2% of them had performed invasive coronary intervention. Myocardial revascularization was appropriate in 81.4% of R-CAD patients and 76.8% of NR-CAD patients. The main factor of revascularization performance was any stenosis >50% and grades III-IV of stable angina. With non-performed revascularization, the following factors were associated: limiting angina or angina equivalent, unresponsive to medical therapy, atherosclerotic peripheral arterial disease and increasing the New York Heart Association class of chronic heart failure. Most ESC/EACTS indications had little effect on decision-making on revascularization. CONCLUSION: There is a discrepancy between the actual clinical situation and ESC/EACTS guidelines on myocardial revascularization in patients with stable CAD in Russia.

Frequency-Domain Features and Low-Frequency Synchronization of Photoplethysmographic Waveform Variability and Heart Rate Variability with Increasing Severity of Cardiovascular Diseases.

Objective-Heart rate variability (HRV) and photoplethysmographic waveform variability (PPGV) are available approaches for assessing the state of cardiovascular autonomic regulation. The goal of our study was to compare the frequency-domain features and low-frequency (LF) synchronization of the PPGV and HRV with increasing severity of cardiovascular diseases. Methods-Our study included 998 electrocardiogram (ECG) and finger photoplethysmogram (PPG) recordings from subjects, classified into five categories: 53 recordings from healthy subjects, aged 28.1 ± 6.2 years, 536 recordings from patients with hypertension (HTN), 49.0 ± 8.8 years old, 185 recordings from individuals with stable coronary artery disease (CAD) (63.9 ± 9.3 years old), 104 recordings from patients with myocardial infarction (MI) that occurred three months prior to the recordings (PMI) (65.1 ± 11.0 years old), and 120 recordings from study subjects with acute myocardial infarction (AMI) (64.7 ± 11.5 years old). Spectral analyses of the HRV and PPGV were carried out, along with an assessment of the synchronization strength between LF oscillations of the HRV and of PPGV (synchronization index). Results-Changes in all frequency-domain indices and the synchronization index were observed along the following gradient: healthy subjects → patients with HTN → patients with CAD → patients with PMI → patients with AMI. Similar frequency-domain indices of the PPGV and HRV show little relationship with each other. Conclusions-The frequency-domain indices of the PPGV are highly sensitive to the development of any cardiovascular disease and, therefore, are superior to the HRV indices in this regard. The S index is an independent parameter from the frequency-domain indices.

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. OBJECTIVE: This study evaluates the prognostic value of autonomic regulation indices for the 5-year risk of fatal and nonfatal cardiovascular events in patients after AMI. METHODS AND RESULTS: We studied 125 patients (53 [42%] female) after AMI aged between 30 and 83 years. The period of observation was 5 years with checkpoints at the first week after AMI and after each year after AMI. We compared the prognostic value of established clinical characteristics and degree S of synchronization between 0.1-Hz rhythms in heart rate and microcirculation for evaluation of the 5-year risk of mortality and recurrent myocardial infarction (MI) in patients after AMI. Acute heart failure Killip 2-4 at AMI and S < 20% at the first week after AMI were identified as the most important factors for evaluation of the risk of 5-year mortality in patients after AMI (χ(2) = 14.2, P = 0.003). Sensitivity and specificity of low S (<20%) at the first week after AMI were 76% and 43%, respectively. For evaluation of the 5-year risk of recurrent MI index S had no advantage over established clinical characteristics. CONCLUSION: The value of S below 20% in patients with AMI is a sensitive marker of high risk of mortality during the subsequent five years. It is characterized by better prognostic value than most of established clinical characteristics.

Application of the Appropriate Use Criteria for Coronary Revascularization in Patients with Acute Coronary Syndrome in the Russian Federation: Data from the Federal Registry.

OBJECTIVE: The aim of the study was to apply the appropriate use criteria (AUC) for coronary revascularization on Russian Acute Coronary Syndrome Registry (RusACSR) data to analyze validity of the decision to perform percutaneous coronary interventions (PCIs) among patients with acute coronary syndrome (ACS). MATERIAL AND METHODS: In Russia, the frequency of performing PCI increased almost 7.5 times, and more than half of all interventions were performed in patients with ACS, in the period from 2006 to 2015. AUC 2012 were used to assess PCI appropriateness. Data were exported from RusACSR from a period of January 1, 2016 to December 31, 2016. We analyzed 33 893 cases, but 13 957 patients were excluded owing to absence of data needed. The study group therefore included 19 936 patients with ACS (mean age, 65.3 ± 11.9 years; 40.3% women), and it was divided into 2 subgroups: 13 757 (67.2%) patients who were treated conservatively and 6179 (32.8%) patients who underwent PCI. According to AUC, physicians' choice of strategy was validated. RESULTS: Patients treated conservatively differed significantly (P < .001) from those who underwent PCI. In this group, non-ST segment elevation ACS was significantly more common than in the group of patients who received PCI (84.4% vs. 43.9%, P < .001). They also had more severe clinical status. According to AUC, among patients with ACS treated with PCI, the decision was warranted in 86.3% (valid decision). In 7.6% of cases, there was no need for PCI. Among patients who underwent conservative treatment, 77.7% of patients needed PCI according to AUC. According to our data, only 3.8% of patients who were treated conservatively did not need PCI. Appropriateness of invasive treatment was uncertain in 18.5% and 6.1% in the PCI and non-PCI groups, respectively. All differences were significant (P < .001). CONCLUSION: AUC implementation showed low availability of PCI for patients with non-ST segment elevation ACS accompanied by complicated clinical status. AUC for coronary revascularization could be applied in Russian clinical practice for unbiased PCI candidate selection and for evaluation of decision validity.

Synchronization of the Processes of Autonomic Control of Blood Circulation in Humans Is Different in the Awake State and in Sleep Stages.

The influence of higher nervous activity on the processes of autonomic control of the cardiovascular system and baroreflex regulation is of considerable interest, both for understanding the fundamental laws of the functioning of the human body and for developing methods for diagnostics and treatment of pathologies. The complexity of the analyzed systems limits the possibilities of research in this area and requires the development of new tools. Earlier we propose a method for studying the collective dynamics of the processes of autonomic control of blood circulation in the awake state and in different stages of sleep. The method is based on estimating a quantitative measure representing the total percentage of phase synchronization between the low-frequency oscillations in heart rate and blood pressure. Analysis of electrocardiogram and invasive blood pressure signals in apnea patients in the awake state and in different sleep stages showed a high sensitivity of the proposed measure. It is shown that in slow-wave sleep the degree of synchronization of the studied rhythms is higher than in the awake state and lower than in sleep with rapid eye movement. The results reflect the modulation of the processes of autonomic control of blood circulation by higher nervous activity and can be used for the quantitative assessment of this modulation.

Mathematical modeling of the cardiovascular autonomic control in healthy subjects during a passive head-up tilt test.

A mathematical model is proposed for the autonomic control of cardiovascular system, which takes into account two separated self-exciting sympathetic control loops of heart rate and peripheral vascular tone. The control loops are represented by self-exciting time-delay systems and their tone depends on activity of the aortic, carotid, and lower-body baroreceptors. The model is used to study the dynamics of the adaptive processes that manifest in a healthy cardiovascular system during the passive head-up tilt test. Computer simulation provides continuous observation of the dynamics of the indexes and variables that cannot be measured in the direct experiment, including the noradrenaline concentration in vessel wall and heart muscle, tone of the sympathetic and parasympathetic control, peripheral vascular resistance, and blood pressure. In the supine and upright positions, we estimated the spectral characteristics of the model variables, especially in the low-frequency band, and the original index of total percent of phase synchronization between the low-frequency oscillations in heart rate and blood pressure signals. The model demonstrates good quantitative agreement with the dynamics of the experimentally observed indexes of cardiovascular system that were averaged for 50 healthy subjects.

Which Measures of Health Status Assessment are the Most Significant in Organized Cohorts with Low Current Cardiovascular Risk? The Screening Study of Penitentiary Staff in Saratov Region, Russia.

OBJECTIVE: The aim of the present study was to compare different methods of health status assessment in organized cohort of penitentiary employees in Saratov Region, Russian Federation. MATERIALS AND METHODS: 1,014 penitentiary employees (81.8% male) aged 33.4±6.8 years were included in the cohort study. All participants underwent an annual preventive health examination in the Center of Medical and Social Rehabilitation of Russian Federal Penitentiary Service in Saratov Region. The prevalence of common cardiovascular risk factors was assessed. Risk Score and the number of fulfilled health metrics proposed by American Heart Association (AHA) were calculated for each participant. RESULTS: It is shown that penitentiary staff in Saratov Region is characterized by low current risk score (1.2±0.8%), but high prevalence of such risk factors as increased body weight and obesity (51%), tobacco use or passive smoking (81%), and unhealthy diet (55%). 98.4% of participants had the Score level of ≤5%, but only 4.5% of penitentiary staff met the ideal cardiovascular health (they met all seven AHA health metrics). One fifth of the participants met three or less AHA health metrics. A statistically significant correlation between the risk Score and the number of fulfilled AHA health metrics is revealed (Chi-square = 5.1, p=0.024). The probability of fulfilment of less than 5 AHA health metrics in subjects with medium risk score is shown to be almost twofold greater than in subjects with low risk Score. However, there are a lot of differences in the assessment of cardiovascular health by risk Score and AHA health metrics. CONCLUSION: AHA health metrics are more preferable than the risk Score or assessment of separate cardiovascular risk factors for preventive management in organized cohorts with low current cardiovascular risk such as penitentiary staff in Saratov Region.

Objectives and Design of the Russian Acute Coronary Syndrome Registry (RusACSR).

The Russian Acute Coronary Syndrome Registry (RusACSR) is a retrospective, continuous, nationwide, Web-based registry of patients with acute coronary syndromes (ACS). The RusACSR is a database that uses a secure Web-based interface for data entry by individual users. Participation in the RusACSR is voluntary. Any clinical center that provides health care to ACS patients can take part in the RusACSR. The RusACSR enrolls ACS patients who have undergone care in Russian hospitals from February 2008 to the present. Key data elements and methods of data analysis in the RusACSR are presented in this article. Up to 2015, 213 clinical centers from 36 regions of Russia had participated in the RusACSR. Currently, the database contains data on more than 250 000 ACS patients who underwent care from 2008 to 2015. Some current problems are highlighted in this article. The RusACSR is a perspective project for different epidemiologic studies in Russian ACS patients.

Model of human cardiovascular system with a loop of autonomic regulation of the mean arterial pressure.

A model of human cardiovascular system is proposed which describes the main heart rhythm, the regulation of heart function and blood vessels by the autonomic nervous system, baroreflex, and the formation of arterial blood pressure. The model takes into account the impact of respiration on these processes. It is shown that taking into account nonlinearity and introducing the autonomous loop of mean arterial blood pressure in the form of self-oscillating time-delay system allow to obtain the model signals whose statistical and spectral characteristics are qualitatively and quantitatively similar to those for experimental signals. The proposed model demonstrates the phenomenon of synchronization of mean arterial pressure regulatory system by the signal of respiration with the basic period close to 10 seconds, which is observed in the physiological experiments.

Autonomic control of cardiovascular system in pre- and postmenopausal women: a cross-sectional study.

OBJECTIVE: The aim of this cross-sectional study was to assess the features of autonomic control of the cardiovascular system in pre- and postmenopausal women. MATERIAL AND METHODS: We studied 185 postmenopausal women aged 59.3±8.5 years (mean±SD) and 104 premenopausal women aged 45.1±5.8 years. Standard indices of heart rate variability (HRV) (mean heart rate, coefficient of variation, standard deviation of the NN interval (the time elapsing between two consecutive R waves in the electrocardiogram with normal sinus rhythm) (SDNN), square root of the mean squared differences of successive NN intervals (RMSSD), proportion derived by dividing RR50, the number of interval differences of successive NN intervals greater than 50 ms, by the total number of NN intervals (PNN50), and power of low frequency (LF) and high frequency (HF) bands in absolute values and percentages of total spectral power) and index S of synchronization between the 0.1-Hz rhythms in heart rate and photoplethysmogram were compared between these two groups at rest. We assessed the following sex hormones: estradiol, follicle stimulating hormone, dehydroepiandrosterone sulfate, and testosterone. RESULTS: Mean heart rate and power of LF and HF bands were significantly different (p<0.05) in pre- and postmenopausal women. The autonomic indices were similar in women with natural and surgical menopause. Some indices (coefficient of variation, SDNN, RMSSD, PNN50, and power of LF and HF bands) showed weak correlation with menopause time in women with natural menopause. In women with surgical menopause, a moderate statistically significant correlation was observed only between menopause time and S index (r=-0.41, p=0.039). In premenopausal women, only testosterone correlated weakly with coefficient of variation, SDNN, PNN50, RMSSD, and power of HF band. In postmenopausal women, no correlations were found. We did not find any significant relationship between autonomic indices and hot flashes, assessed by hot flash diary. CONCLUSION: We did not find a clinically important relationship between cardiovascular autonomic control and menopausal status in women.

Effects of antihypertensive treatment on cardiovascular autonomic control: a prospective study.

OBJECTIVE: The aim of study was to propose an approach to the control of dynamics of autonomic dysfunction in cardiovascular system (CVS) under antihypertensive treatment (AT) in patients with arterial hypertension (AH), based on individual features of synchronization of 0.1-Hz rhythms in heart rate (HR) and photoplethysmogram (PPG) and spectral indices of heart rate variability (HRV). METHODS: We designed prospective cohort diagnostic accuracy and studied 105 AH patients (66 females) aged 47±8 years during 8 weeks. The HRV spectral indices and the index S of synchronization between the 0.1-Hz rhythms in HR and PPG during a tilt test are compared in their ability to control the AT with angiotensin-converting enzyme inhibitors (ACE-Is) (fosinopril or enalapril) and ß-blockers (atenolol or metoprolol). We apply Shapiro-Wilk, Mann-Whitney U and Wilcoxon tests. RESULTS: It is shown that the power of low-frequency (LF) band in HRV spectrum and index S can be used as criteria for initial assessment of the status of autonomic regulation in AH patients. The patients with S<25% in vertical body's position and LF>250 ms2 in horizontal body's position require ACE-Is treatment. The AH patients with LF<350 ms2 and S<30% in vertical body's position require ß-blocker treatment. The AH patients with S>25% and LF>250 ms2 in horizontal body's position do not require any ACE-Is or ß-blocker treatment. Both drug groups can be used in patients with low values of index S and low power of LF band in HRV spectrum. CONCLUSION: The control of AT can be carried out in AH patients taking into account the individual features of autonomic dysfunction in CVS. Sensitivity and specificity of our approach were 65% and 73%, respectively.

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.

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.