Comparison of dynamic of autonomic control indices in cardiovascular system under the treatment by ACE inhibitor (Enalapril) and beta-blocker (Metoprolol) in patients with hypertension

The objective of the present research was to compare the influence of Enalapril and Metoprolol on synchronization of 0.1 Hz-regulation of heart and blood microcirculation. 42 patients aged 49±9 years old with hypertension I, II were included in the study. 0.1 Hz-oscillations in heart rate variability (HRV) and blood microcirculation were registered during the passive orthostatic sign while breathing spontaneously. The duration of each test was 10 minutes. Synchronization was estimated as a phase difference between 0.1 Hz-rhythms in heart rate and in filling of blood microcirculation. Quantitative measures of synchronization were also estimated. In addition frequency values of HRV spectrum in LF- and HF-ranges were assessed. Enalapril and Metoprolol had comparable effect on blood pressure reduction. Treatment with both Enalapril and Metoprolol in patients with significant vegetative dysfunction resulted in repair of functional interaction between 0.1 Hz-regulation of heart and blood microcirculation. Enalapril was preferred in hypertensive patients with prevalence of disorders of vegetative regulation of blood microcirculation. Metoprolol influenced positively on 0,1 Hz-rhythm synchronization in patients with predominance of heart vegetative regulation dysfunction and in patients with sympathicotonia. In patients with hypertension and initially normal level of synchronization of 0.1 Hz-mechanisms treatment with Enalapril or Metoprolol caused functional dissociation. Differentiated approach to the choice of hypertensive therapy should consider individual peculiarities of system vegetative dysfunction. The level of synchronization of 0.1 Hz-rhythms in cardiovascular system should especially be evaluated initially and during the treatmen

Application of adaptive nonlinear Granger causality: Disclosing network changes before and after absence seizure onset in a genetic rat model

Item does not contain fulltextBackground: Advanced methods of signal analysis of the preictal and ictal activity dynamics characterizing absence epilepsy in humans with absences and in genetic animal models have revealed new and unknown electroencephalographic characteristics, that has led to new insights and theories. New method: Taking into account that some network associations can be considered as nonlinear, an adaptive nonlinear Granger causality approach was developed and applied to analyze cortico-cortical, cortico-thalamic and intrathalamic network interactions from local field potentials (LFPs). The outcomes of adaptive nonlinear models, constructed based on the properties of electroencephalographic signal and on statistical criteria to optimize the number of coefficients in the models, were compared with the outcomes of linear Granger causality. Results: The nonlinear adaptive method showed statistically significant preictal changes in Granger causality in almost all pairs of channels, as well as ictal changes in cortico-cortical, cortico-thalamic and intrathalamic networks. Current results suggest rearrangement of interactions in the thalamo-cortical network accompanied the transition from preictal to ictal phase. Comparison with existing method(s): The linear method revealed no preictal and less ictal changes in causality. Conclusions: Achieved results suggest that this proposed adaptive nonlinear method is more sensitive than the linear one to dynamics of network properties. Since changes in coupling were found before the seizure-related increase of LFP signal amplitude and also based on some additional tests it seems likely that they were not spurious and could not result from signal to noise ratio change.9 p

Synchronization of low-frequency oscillations in the cardiovascular system: Application to medical diagnostics and treatment

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 quantitative estimation of this synchronization based on calculation of relative time of phase synchronization of oscillations is proposed. We show that assessment of synchronization between the considered oscillations can be useful for selecting an optimal dose of beta-blocker treatment in patients after acute myocardial infarction. It is found out that low value of synchronization between the low-frequency rhythms in heart rate and blood pressure at the first week after acute myocardial infarction is a sensitive marker of high risk of mortality during the subsequent 5 years

Connectivity detection in application to spike-wave discharge study

Contains fulltext : 227417.pdf (publisher's version ) (Open Access)In our study, we compare three popular approaches to directed coupling analysis, in particular transfer entropy and two types of Granger causality, applied to real data from genetic absence epilepsy rats. We have chosen the channels for which the coupling architecture is already well known from previous studies. Recordings from 5 WAG/Rij rats of 8 hours duration with at least 28 spontaneous seizures of length not less than 6 s in each recording were studied. To test results for significance, surrogate signals based on series permutation technique were constructed. Connectivity development in time was investigated by considering six two-second intervals before, during and after the seizure. Our outcomes showed large differences between studied approaches, while all of them exploit the same general idea. Transfer entropy demonstrated the smallest number of significant couplings throughout all three considered measures, while the linear Granger causality showed the largest number of them. This indicates that transfer entropy is the most conservative measure and the least sensitive one. Its sensitivity is affected by insufficient series length. The linear Granger causality is likely to demonstrate insufficient specificity.12 p

Evaluation of five-year risk of lethal outcome and development of cardiovascular disorders in patients with acute myocardial infarction on basis of 0.1-Hz rhythms synchronization in cardiovascular system

The research goal is to evaluate the impact of autonomic heart control indices on five-year risk of lethal outcome and development of cardiovascular disorders in patients with acute myocardial infarction (AMI) and to study the dynam¬ics of indices in short- and long-term period. 125 patients with AMI (42% female), ages 30 to 83 years, were enrolled in prospective observational study. Observation period lasted 6 years. Control checking was carried out in 1 week, 3 weeks, 6 months, 1 year and then annually. The dynamics of heart rate variability (HRV) and the synchronization of 0.1-Hz rhythms of heart and microcirculation (S) were studied during the first year. Outcomes proved to be death, MI, stroke. Development of acute heart failure Killip 2-4 and indices S < 20% during the first week of AMI (х2 = 10,5, p = 0,005 for the Cox model) played a significant role in evaluation of five-year risk of death after AMI. Sensitivity (Se) and specificity (Sp) of index S < 20% during the first week of AMI were 76% and 43% correspondingly. The Cox model showed that indices of HRV and 0.1-Hz rhythms synchronization were not of great value in evaluation of five-year risk of death after AMI. The article concludes that indices S < 20% in patients with AMI possess better prognostic value than common clinical parameter

Synchronization of low-frequency rhythms in electroencephalogram by respiration with linear dependent time frequency.

The aim of the present study was to investigate the features of interaction of low-frequency rhythms in delta band of electroencephalogram (EEG) and processes in vegetative regulation of circulation with respiration. Materials and methods. 19 leads of EEG, photoplethysmogram (PPG) and respiration were simultaneously recorded in four healthy males (19-25 years old) during 30 minutes physiological test with linearly increasing frequency of respiration. Modern methods of nonlinear dynamics were used to diagnose the presence of phase and frequency synchronization between respiration and low-frequency rhythms in delta band of EEG and in PPG. Results. We found significantly long sections of synchronization of delta rhythms in cervical leads of EEG and low-frequency rhythms in PPG by respiration with linearly increasing frequency. Conclusion. Obtained results correlate well with established hypothesis which suggest that low-frequency rhythms in baroreflectory regulation of circulation are in complex dynamic relationships with structures of brain stem. A method was proposed for quantitative evaluation of synchronization strength between respiration and low-frequency rhythms in electrical brain activity in physiological tests with respiration with frequency linearly increasing in time