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.

Outcomes of Atrioseptostomy with Stenting in Patients with Pulmonary Arterial Hypertension from a Large Single-Institution Cohort.

The aim of this study was to analyze results of stenting atrioseptostomy in patients with pulmonary arterial hypertension and a different level of risk for one-year mortality that is not well described. Patients that underwent atrioseptostomy with stenting were retrospectively divided in two groups: "intermediate" (n = 55) or "high" risk (n = 13), according to the 2015 ESC/ESR guideline. Results of atrioseptostomy were assessed during hospital period and at follow-up. Patients from "intermediate" risk group demonstrated lower mortality rate (10/55, vs. 6/13) during the course of the study period, as well as higher freedom from lung transplantation or Potts shunt. At discharge, patients of both groups presented improvement in functional class and mobility. Patients from "intermediate" risk group showed longer 6-min walking distance, and lower levels of brain natriuretic peptide. At the latest follow-up, stable position and full patency of stents with right-to-left or bidirectional shunt at atrial level and absence of syncope was confirmed in patients of both groups. Patients from the "intermediate" risk group demonstrated higher functional class, better performance of walking test, and lower levels of brain natriuretic peptide. Stenting atrioseptostomy reliably secured interatrial communication and improved clinical condition in patients with idiopathic pulmonary arterial hypertension. Mid-term results were better in "intermediate" risk group.

Low-frequency variability in photoplethysmographic waveform and heart rate during on-pump cardiac surgery with or without cardioplegia.

We studied the properties of low-frequency (LF) heart rate variability (HRV) and photoplethysmographic waveform variability (PPGV) and their interaction under conditions where the hemodynamic connection between them is obviously absent, as well as the LF regulation of PPGV in the absence of heart function. The parameters of HRV and finger PPGV were evaluated in 10 patients during cardiac surgery under cardiopulmonary bypass (on-pump cardiac surgery) with or without cardioplegia. The following spectral indices of PPGV and HRV were ertimated: the total spectral power (TP), the high-frequency (HF) and the LF ranges of TP in percents (HF% and LF%), and the LF/HF ratio. We assessed also the index S of synchronization between the LF oscillations in finger photoplethysmogram (PPG) and heart rate (HR) signals. The analysis of directional couplings was carried out using the methods of phase dynamics modeling. It is shown that the mechanisms leading to the occurrence of oscillations in the LF range of PPGV are independent of the mechanisms causing oscillations in the LF range of HRV. At the same time, the both above-mentioned LF oscillations retain their activity under conditions of artificial blood circulation and cardioplegia (the latter case applies only to LF oscillations in PPG). In artificial blood circulation, there was a coupling from the LF oscillations in PPG to those in HR, whereas the coupling in the opposite direction was absent. The coupling from the LF oscillations in PPG to those in HR has probably a neurogenic nature, whereas the opposite coupling has a hemodynamic nature (due to cardiac output).

Effect of epicardial application of amiodarone-releasing hydrogel on heart rate in an animal model.

BACKGROUND: The purpose of the experiment was to study the safety of local epicardial use of the hydrogel with amiodarone, as well as the influence of its different dosages on the heart rate of mongrel rabbits. METHODS: The epicardial application of the hydrogel material with amiodarone was performed in 46 rabbits. Rabbits were divided into 5 groups: Group No. 1-dose of amiodarone in the hydrogel 1 mg, Group No. 2-dose 3 mg; Group No. 3-dose 6 mg; Group No. 4-hydrogel without amiodarone; Group No. 5-amiodarone intravenously, 60 mg. RESULTS: The application of hydrogel with amiodarone is not accompanied by a systemic inflammatory reaction. In group No. 2, there was a significant reduction in the heart rate (before surgery: 158±16, after: 130±11, (P<0,001), without any disturbances to the conduction system of the heart functioning. With an increase in amiodarone concentration (Group No. 3), significant atrial and atrioventricular (AV) conduction defects (up to 70%) were noted; when the dosage of amiodarone (Group No. 1) was reduced, there was no influence on the heart rate reduction. The hydrogel without amiodarone has no effect on the conductive system. CONCLUSIONS: The method of local epicardial delivery of amiodarone in the form of a hydrogel material is safe. The hydrogel with amiodarone is effective for the heart rate reduction (according to the experiment on animals), compared to the control group and the group with intravenous drug administration. The optimal dosage of amiodarone in the hydrogel is 3 mg.

Comparative study of short-term cardiovascular autonomic control in cardiac surgery patients who underwent coronary artery bypass grafting or correction of valvular heart disease.

Introduction: Our aim was to perform a comparative study of short-term cardiovascular autonomic control in cardiac surgery patients who underwent coronary artery bypass grafting (CABG) or surgical correction of valvular heart disease (SCVHD ). Methods: The synchronous 15 minutes records of heart rate variability (HRV) and finger's photoplethysmographic waveform variability (PPGV) were performed in 42 cardiac surgery patients (12 women) aged 61.8 ± 8.6 years (mean ± standard deviation), who underwent CABG, and 36 patients (16 women) aged 54.2 ± 14.9 years, who underwent SCVHD , before surgery and in 5-7 days after surgery. Conventional time and frequency domain measures of HRV and index S of synchronization between the slow oscillations in PPGV and HRV were analyzed. We also calculated personal dynamics of these indices after surgery. Results: We found no differences (Р > 0.05) in all studied autonomic indices (preoperative and post-surgery) between studied patients' groups, except for the preoperative heart rate, which was higher in patients who underwent SCVHD (P = 0.013). We have shown a pronounced preoperative and post-surgery variability (magnitude of inter-quartile ranges) of all autonomic indices in studied patients. In the cluster analysis based on cardiovascular autonomic indices (preoperative and post-surgery), we divided all patients into two clusters (38 and 40 subjects) which did not differ in all clinical characteristics (except for the preoperative hematocrit, P = 0.038), index S, and all post-surgery HRV indices. First cluster (38 patients) had higher preoperative values of the HR, TP, HF, and HF%, and lower preoperative values of the LF% and LF/HF. Conclusion: The variability of cardiovascular autonomic indices in on-pump cardiac surgery patients (two characteristic clusters were identified based on preoperative indices) was not associated with their clinical characteristics and features of surgical procedure (including cardioplegia).

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.

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.