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Maki KA, Goodyke MP, Rasmussen K, Bronas UG. An Integrative Literature Review of Heart Rate Variability Measures to Determine Autonomic Nervous System Responsiveness Using Pharmacological Manipulation. J Cardiovasc Nurs 2024; 39:58-78. [PMID: 37249528 PMCID: PMC10684820 DOI: 10.1097/jcn.0000000000001001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
BACKGROUND Heart rate variability (HRV) is defined as the difference in the timing of intervals between successive heartbeats and is used as a surrogate measure to the responsiveness of the autonomic nervous system. A review and synthesis of HRV as an indicator of autonomic nervous system responsiveness to pharmacologic stimulation/blockade of sympathetic and/or parasympathetic nervous system branches have not been completed. PURPOSE The aim of this integrative review is to synthesize research examining pharmacological modulation of the autonomic nervous system and the response of time domain, frequency domain, and nonlinear measures of HRV. CONCLUSIONS Sympathetic nervous system blockade resulted in a consistent decrease in the standard deviation of normal-normal interval metric across studies. Stimulation of the parasympathetic nervous system was associated with an increase in several time, frequency, and nonlinear HRV indices, whereas blockade of the parasympathetic nervous system led to a decrease in similar indices. CLINICAL IMPLICATIONS Recommendations to improve the reproducibility of future HRV research are provided for standardization of recording, analysis, and metric decisions and more thorough reporting of HRV indices in published studies. Alterations in autonomic nervous system input to the cardiovascular system are associated with an increased risk for adverse patient outcomes and increased mortality; therefore, understanding the influence of pharmacologic autonomic nervous system modulation on HRV indices and important considerations for reproducible HRV research design will inform future translational research on cardiovascular risk reduction.
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Affiliation(s)
- Katherine A. Maki
- Translational Biobehavioral and Health Disparities Branch, National Institutes of Health, Clinical Center, Bethesda, MD, 20814
- University of Illinois at Chicago, College of Nursing, Department of Biobehavioral Nursing Science, Chicago, IL, 60612
| | - Madison P. Goodyke
- University of Illinois at Chicago, College of Nursing, Department of Biobehavioral Nursing Science, Chicago, IL, 60612
| | - Kendra Rasmussen
- The Johns Hopkins Hospital, Nursing Department, Baltimore, MD, 21287
| | - Ulf G. Bronas
- University of Illinois at Chicago, College of Nursing, Department of Biobehavioral Nursing Science, Chicago, IL, 60612
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Nowiński A, Chabowski D, Giebułtowicz J, Aleksandrowicz M, Ufnal M. Deoxycholic Acid, a Secondary Bile Acid, Increases Cardiac Output and Blood Pressure in Rats. Nutrients 2023; 16:32. [PMID: 38201862 PMCID: PMC10781055 DOI: 10.3390/nu16010032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2023] [Revised: 12/16/2023] [Accepted: 12/19/2023] [Indexed: 01/12/2024] Open
Abstract
BACKGROUND Deoxycholic acid (DCA) is a secondary bile acid produced by gut bacteria. Elevated serum concentrations of DCA are observed in cardiovascular disease (CVD). We hypothesized that DCA might influence hemodynamic parameters in rats. METHODS The concentration of DCA in systemic blood was measured with liquid chromatography coupled with mass spectrometry. Arterial blood pressure (BP), heart rate (HR) and echocardiographic parameters were evaluated in anesthetized, male, 3-4-month-old Sprague-Dawley rats administered intravenously (IV) or intracerebroventricularly (ICV) with investigated compounds. Mesenteric artery (MA) reactivity was tested ex vivo. RESULTS The baseline plasma concentration of DCA was 0.24 ± 0.03 mg/L. The oral antibiotic treatment produced a large decrease in the concentration. Administered IV, the compound increased BP and HR in a dose-dependent manner. DCA also increased heart contractility and cardiac output. None of the tested compounds-prazosin (an alpha-blocker), propranolol (beta-adrenolytic), atropine (muscarinic receptor antagonist), glibenclamide (K-ATP inhibitor) or DY 268 (FXR antagonist), glycyrrhetinic acid (11HSD2 inhibitor)-significantly diminished the DCA-induced pressor effect. ICV infusion did not exert significant HR or BP changes. DCA relaxed MAs. Systemic vascular resistance did not change significantly. CONCLUSIONS DCA elevates BP primarily by augmenting cardiac output. As a metabolite derived from gut bacteria, DCA potentially serves as a mediator in the interaction between the gut microbiota and the host's circulatory system.
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Affiliation(s)
- Artur Nowiński
- Department of Experimental Physiology and Pathophysiology, Laboratory of Centre for Preclinical Research, Medical University of Warsaw, 02-106 Warsaw, Poland; (D.C.); (M.U.)
| | - Dawid Chabowski
- Department of Experimental Physiology and Pathophysiology, Laboratory of Centre for Preclinical Research, Medical University of Warsaw, 02-106 Warsaw, Poland; (D.C.); (M.U.)
| | - Joanna Giebułtowicz
- Department of Bioanalysis and Drugs Analysis, Faculty of Pharmacy, Medical University of Warsaw, 1 Banacha, 02-097 Warsaw, Poland;
| | - Marta Aleksandrowicz
- Laboratory of Preclinical Research and Environmental Agents, Mossakowski Medical Research Institute, Polish Academy of Sciences, 02-106 Warsaw, Poland;
| | - Marcin Ufnal
- Department of Experimental Physiology and Pathophysiology, Laboratory of Centre for Preclinical Research, Medical University of Warsaw, 02-106 Warsaw, Poland; (D.C.); (M.U.)
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Frasier RM, De Oliveira Sergio T, Starski PA, Grippo AJ, Hopf FW. Heart rate variability measures indicating sex differences in autonomic regulation during anxiety-like behavior in rats. Front Psychiatry 2023; 14:1244389. [PMID: 38025424 PMCID: PMC10644002 DOI: 10.3389/fpsyt.2023.1244389] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/22/2023] [Accepted: 10/11/2023] [Indexed: 12/01/2023] Open
Abstract
Introduction Mental health conditions remain a substantial and costly challenge to society, especially in women since they have nearly twice the prevalence of anxiety disorders. However, critical mechanisms underlying sex differences remain incompletely understood. Measures of cardiac function, including heart rate (HR) and HR variability (HRV), reflect balance between sympathetic (SNS) and parasympathetic (PNS) systems and are potential biomarkers for pathological states. Methods To better understand sex differences in anxiety-related autonomic mechanisms, we examined HR/HRV telemetry in food-restricted adult rats during novelty suppression of feeding (NSF), with conflict between food under bright light in the arena center. To assess HRV, we calculated the SDNN (reflective of both SNS and PNS contribution) and rMSSD (reflective of PNS contribution) and compared these metrics to behaviors within the anxiety task. Results Females had greater HR and lower SNS indicators at baseline, as in humans. Further, females (but not males) with higher basal HR carried this state into NSF, delaying first approach to center. In contrast, males with lower SNS measures approached and spent more time in the brightly-lit center. Further, females with lower SNS indicators consumed significantly more food. In males, a high-SNS subpopulation consumed no food. Among consumers, males with greater SNS ate more food. Discussion Together, these are congruent with human findings suggesting women engage PNS more, and men SNS more. Our previous behavior-only work also observed female differences from males during initial movement and food intake. Thus, high basal SNS in females reduced behavior early in NSF, while subsequent reduced SNS allowed greater food intake. In males, lower SNS increased engagement with arena center, but greater SNS predicted higher consumption. Our findings show novel and likely clinically relevant sex differences in HRV-behavior relationships.
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Affiliation(s)
- Raizel M. Frasier
- Department of Psychiatry, Indiana University School of Medicine, Indianapolis, IN, United States
- Medical Scientist Training Program, Indiana University School of Medicine, Indianapolis, IN, United States
| | | | - Phillip A. Starski
- Department of Psychiatry, Indiana University School of Medicine, Indianapolis, IN, United States
| | - Angela J. Grippo
- Department of Psychology, Northern Illinois University, DeKalb, IL, United States
| | - F. Woodward Hopf
- Department of Psychiatry, Indiana University School of Medicine, Indianapolis, IN, United States
- Stark Neurosciences Research Institute, Indiana University, Indianapolis, IN, United States
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Švorc P, Grešová S, Švorc P. Heart rate variability in male rats. Physiol Rep 2023; 11:e15827. [PMID: 37735345 PMCID: PMC10514026 DOI: 10.14814/phy2.15827] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2023] [Revised: 09/09/2023] [Accepted: 09/12/2023] [Indexed: 09/23/2023] Open
Abstract
The cardiovascular system is primarily controlled by the autonomic nervous system, and any changes in sympathetic or parasympathetic activity also have an impact on myocardial activity. Heart rate variability (HRV) is a readily available metric used to assess heart rate control by the autonomic nervous system. HRV can provide information about neural (parasympathetic, sympathetic, reflex) and humoral (hormones, thermoregulation) control of myocardial activity. Because there are no relevant reference values for HRV parameters in rats in the scientific literature, all experimental results are only interpreted on the basis of changes from currently measured control or baseline HRV values, which are, however, significantly different in individual studies. Considering the significant variability of published HRV data, the present study focused primarily on comparing control or baseline HRV values under different conditions in in vivo experiments involving rats. The aim of the study was therefore to assess whether there are differences in the starting values before the experiment itself.
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Affiliation(s)
- Pavol Švorc
- Department of Physiology and Pathophysiology, Faculty of MedicineOstrava UniversityOstravaCzech Republic
| | - Soňa Grešová
- Department of Physiology, Faculty of MedicineUniversity PJ SafarikaKosiceSlovak Republic
| | - Pavol Švorc
- Department of Physiology and Pathophysiology, Faculty of MedicineOstrava UniversityOstravaCzech Republic
- Department of Physiology, Faculty of MedicineUniversity PJ SafarikaKosiceSlovak Republic
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Scarciglia A, Catrambone V, Bonanno C, Valenza G. Characterization of Physiological Noise in Complex Cardiovascular Variability Series. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2023; 2023:1-4. [PMID: 38082793 DOI: 10.1109/embc40787.2023.10339997] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2023]
Abstract
The cardiovascular system can be analyzed using spectral, nonlinear, and complexity metrics. Nevertheless, dynamical noise may significantly impact these quantifiers. To our knowledge, there has been no attempt to quantify the intrinsic cardiovascular system noise driving heartbeat dynamics. To this end, this study presents a novel, model-free framework to define and quantify physiological noise using nonlinear Approximate Entropy profile. The framework was tested using analytical noisy series and then applied to real Heart Rate Variability (HRV) series gathered from a publicly-available dataset of recordings from 19 young and 19 elderly subjects watching the movie "Fantasia". Results suggest that physiological noise may account for over 15% of cardiovascular dynamics and is influenced by aging, with decreased cardiac noise in the elderly compared to the young subjects. Our findings indicate that physiological noise is a crucial factor in characterizing cardiovascular dynamics, and current spectral, nonlinear, and complexity assessments should take into account underlying dynamical noise estimates.
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Nardelli M, Citi L, Barbieri R, Valenza G. Characterization of autonomic states by complex sympathetic and parasympathetic dynamics. Physiol Meas 2023; 44. [PMID: 36787644 DOI: 10.1088/1361-6579/acbc07] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2022] [Accepted: 02/14/2023] [Indexed: 02/16/2023]
Abstract
Assessment of heartbeat dynamics provides a promising framework for non-invasive monitoring of cardiovascular and autonomic states. Nevertheless, the non-specificity of such measurements among clinical populations and healthy conditions associated with different autonomic states severely limits their applicability and exploitation in naturalistic conditions. This limitation arises especially when pathological or postural change-related sympathetic hyperactivity is compared to autonomic changes across age and experimental conditions. In this frame, we investigate the intrinsic irregularity and complexity of cardiac sympathetic and vagal activity series in different populations, which are associated with different cardiac autonomic dynamics. Sample entropy, fuzzy entropy, and distribution entropy are calculated on the recently proposed sympathetic and parasympathetic activity indices (SAI and PAI) series, which are derived from publicly available heartbeat series of congestive heart failure patients, elderly and young subjects watching a movie in the supine position, and healthy subjects undergoing slow postural changes. Results show statistically significant differences between pathological/old subjects and young subjects in the resting state and during slow tilt, with interesting trends in SAI- and PAI-related entropy values. Moreover, while CHF patients and healthy subjects in upright position show the higher cardiac sympathetic activity, elderly and young subjects in resting state showed higher vagal activity. We conclude that quantification of intrinsic cardiac complexity from sympathetic and vagal dynamics may provide new physiology insights and improve on the non-specificity of heartbeat-derived biomarkers.
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Affiliation(s)
- Mimma Nardelli
- Bioengineering and Robotics Research Centre E. Piaggio and Dipartimento di Ingegneria dell'Informazione, University of Pisa, Italy
| | - Luca Citi
- School of Computer Science and Electronic Engineering, University of Essex, United Kingdom
| | - Riccardo Barbieri
- Department of Electronics, Informatics and Bioengineering, Politecnico di Milano, Milano, Italy
| | - Gaetano Valenza
- Bioengineering and Robotics Research Centre E. Piaggio and Dipartimento di Ingegneria dell'Informazione, University of Pisa, Italy
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Nie J, Tong TK, Zhou Y, Shi Q, Zhang H, Kong Z. Cardiac autonomic disturbance following resistance and sprint-interval exercises in non-obese and obese young men. Appl Physiol Nutr Metab 2022; 47:949-962. [PMID: 35728265 DOI: 10.1139/apnm-2022-0166] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
This study examined the alterations of heart rate variability (HRV) following iso-duration resistance (RES) and sprint-interval (SIE) exercises by comparing with that of non-exercise control (CON) in 14 non-obese (NOB) and 15 obese (OB) young men. Time and frequency domain measures as well as non-linear metrics of HRV were assessed before and immediately after exercise, and during every 20 min until 120 min post exercise. The variables during the first 4 hrs of actual sleep time at night, and the period of 12-14 hrs post exercise were also measured. All trials were scheduled at 20:00. It was found that RES and SIE attenuated the HRV in both NOB and OB (P <0.05), and the attenuated HRV restored progressively during subsequent recovery. Although the changes in HRV indices among various time points during the recovery period and its interaction across RES, SIE and CON were not different between NOB and OB, the restoration of the declined HRV indices to corresponding CON level in the two exercise trials in OB appeared to be sluggish in relative to NOB. Notwithstanding, post-exercise HRV that recorded during actual sleep at night and during 12-14 hrs apart from exercise were unvaried among the three trials in both groups (P>0.05). These findings suggest that obesity is likely to be a factor hindering the removal of exercise-induced cardiac autonomic disturbance in young men. Nonetheless, the declined HRV following both the RES and SIE protocols were well restored after a resting period of ~10 hrs regardless of obesity. The study was registered at ISRCTN as DOI:10.1186/ISRCTN88544091.
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Affiliation(s)
- Jinlei Nie
- Macao Polytechnic University, 59192, Faculty of Health Sciences and Sports, Macau, Macao;
| | - Tomas K Tong
- Hong Kong Baptist University, 26679, Hong Kong, Hong Kong;
| | - Yingqi Zhou
- Chengde Medical University, 92979, Chengde, Hebei, China;
| | - Qingde Shi
- Macao Polytechnic University, 59192, Faculty of Health Sciences and Sports, Macau, Macao;
| | - Haifeng Zhang
- Hebei Normal University, 66447, Physical Education College, Shijiazhuang, Heibei, China;
| | - Zhaowei Kong
- University of Macau, 59193, Faculty of Education, Taipa, Macao;
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Saul JP, Valenza G. Heart rate variability and the dawn of complex physiological signal analysis: methodological and clinical perspectives. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2021; 379:20200255. [PMID: 34689622 DOI: 10.1098/rsta.2020.0255] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 01/14/2021] [Indexed: 06/13/2023]
Abstract
Spontaneous beat-to-beat variations of heart rate (HR) have intrigued scientists and casual observers for centuries; however, it was not until the 1970s that investigators began to apply engineering tools to the analysis of these variations, fostering the field we now know as heart rate variability or HRV. Since then, the field has exploded to not only include a wide variety of traditional linear time and frequency domain applications for the HR signal, but also more complex linear models that include additional physiological parameters such as respiration, arterial blood pressure, central venous pressure and autonomic nerve signals. Most recently, the field has branched out to address the nonlinear components of many physiological processes, the complexity of the systems being studied and the important issue of specificity for when these tools are applied to individuals. When the impact of all these developments are combined, it seems likely that the field of HRV will soon begin to realize its potential as an important component of the toolbox used for diagnosis and therapy of patients in the clinic. This article is part of the theme issue 'Advanced computation in cardiovascular physiology: new challenges and opportunities'.
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Affiliation(s)
- J Philip Saul
- Department of Pediatrics, School of Medicine, West Virginia University, Morgantown, WV 25606, USA
| | - Gaetano Valenza
- Research Center E. Piaggio and Department of Information Engineering, University of Pisa, Pisa, Italy
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Nardelli M, Citi L, Barbieri R, Valenza G. Intrinsic Complexity of Sympathetic and Parasympathetic Dynamics from HRV series: a Preliminary Study on Postural Changes. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2020; 2020:2577-2580. [PMID: 33018533 DOI: 10.1109/embc44109.2020.9175587] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The analysis of complex heartbeat dynamics has been widely used to characterize heartbeat autonomic control in healthy and pathological conditions. However, underlying physiological correlates of complexity measurements from heart rate variability (HRV) series have not been identified yet. To this extent, we investigated intrinsic irregularity and complexity of cardiac sympathetic and vagal activity time series during postural changes. We exploited our recently proposed HRV-based, time-varying Sympathetic and Parasympathetic Activity Indices (SAI and PAI) and performed Sample Entropy, Fuzzy Entropy, and Distribution Entropy calculations on publicly-available heartbeat series gathered from 10 healthy subjects undergoing resting state and passive slow tilt sessions. Results show significantly higher entropy values during the upright position than resting state in both SAI and PAI series. We conclude that an increase in HRV complexity resulting from postural changes may derive from sympathetic and vagal activities with higher complex dynamics.
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10
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Valenza G, Passamonti L, Duggento A, Toschi N, Barbieri R. Uncovering complex central autonomic networks at rest: a functional magnetic resonance imaging study on complex cardiovascular oscillations. J R Soc Interface 2020; 17:20190878. [PMID: 32183642 DOI: 10.1098/rsif.2019.0878] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
This study aims to uncover brain areas that are functionally linked to complex cardiovascular oscillations in resting-state conditions. Multi-session functional magnetic resonance imaging (fMRI) and cardiovascular data were gathered from 34 healthy volunteers recruited within the human connectome project (the '100-unrelated subjects' release). Group-wise multi-level fMRI analyses in conjunction with complex instantaneous heartbeat correlates (entropy and Lyapunov exponent) revealed the existence of a specialized brain network, i.e. a complex central autonomic network (CCAN), reflecting what we refer to as complex autonomic control of the heart. Our results reveal CCAN areas comprised the paracingulate and cingulate gyri, temporal gyrus, frontal orbital cortex, planum temporale, temporal fusiform, superior and middle frontal gyri, lateral occipital cortex, angular gyrus, precuneous cortex, frontal pole, intracalcarine and supracalcarine cortices, parahippocampal gyrus and left hippocampus. The CCAN visible at rest does not include the insular cortex, thalamus, putamen, amygdala and right caudate, which are classical CAN regions peculiar to sympatho-vagal control. Our results also suggest that the CCAN is mainly involved in complex vagal control mechanisms, with possible links with emotional processing networks.
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Affiliation(s)
- Gaetano Valenza
- Bioengineering and Robotics Research Centre 'E. Piaggio', University of Pisa, Pisa, Italy.,Deparment of Information Engineering, University of Pisa, Pisa, Italy
| | - Luca Passamonti
- Institute of Bioimaging and Molecular Physiology, National Research Council, Milano, Italy.,Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK
| | - Andrea Duggento
- Department of Biomedicine and Prevention, University of Rome 'Tor Vergata', Rome, Italy
| | - Nicola Toschi
- Department of Biomedicine and Prevention, University of Rome 'Tor Vergata', Rome, Italy
| | - Riccardo Barbieri
- Department of Electronics, Informatics and Bioengineering, Politecnico di Milano, Milano, Italy
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Reyes-Lagos JJ, Ledesma-Ramírez CI, Hadamitzky M, Peña-Castillo MÁ, Echeverría JC, Lückemann L, Schedlowski M, Berg K, Wessel N, Pacheco-López G. Symbolic analysis of heart rate fluctuations identifies cardiac autonomic modifications during LPS-induced endotoxemia. Auton Neurosci 2019; 221:102577. [PMID: 31445407 DOI: 10.1016/j.autneu.2019.102577] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2019] [Revised: 07/14/2019] [Accepted: 07/15/2019] [Indexed: 12/28/2022]
Abstract
The present study aimed to compare linear and symbolic dynamics (SD) indices for detecting the autonomic cardiac changes produced by endotoxemia in freely-moving rats. In this context, we analyzed ECG-derived R-R time series in freely moving Dark Agouti rats, which received lipopolysaccharide (LPS, n = 9), or vehicle (V, n = 7). Five minutes R-R time series were assessed every hour up to +12 h and + 24 h post-LPS injection. We found that SD indices showed significant differences at +7 h between V vs. LPS groups and at +9 h between basal levels of LPS (-3 h) and post-LPS injection (pre-LPS vs. post-LPS). In general, SD seems more appropriate than linear indices to evaluate the autonomic changes of endotoxemic rats. Overall, the symbolic parameters detected decreased R-R variability and complexity, which indicate a modification of the autonomic regulation during LPS-induced endotoxemia. This modification is probably related to a reduced activity of the cholinergic anti-inflammatory pathway at the long term.
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Affiliation(s)
- José Javier Reyes-Lagos
- Autonomous University of the State of Mexico (UAEMex), Faculty of Medicine, Toluca, 50180, Mexico
| | | | - Martin Hadamitzky
- University of Duisburg-Essen, University Hospital Essen, Institute of Medical Psychology and Behavioral Immunobiology, Essen 45122, Germany
| | - Miguel Ángel Peña-Castillo
- Metropolitan Autonomous University (UAM), Campus Iztapalapa, Basic Sciences and Engineering Division, Mexico City 09340, Mexico
| | - Juan C Echeverría
- Metropolitan Autonomous University (UAM), Campus Iztapalapa, Basic Sciences and Engineering Division, Mexico City 09340, Mexico
| | - Laura Lückemann
- University of Duisburg-Essen, University Hospital Essen, Institute of Medical Psychology and Behavioral Immunobiology, Essen 45122, Germany
| | - Manfred Schedlowski
- University of Duisburg-Essen, University Hospital Essen, Institute of Medical Psychology and Behavioral Immunobiology, Essen 45122, Germany
| | - Karsten Berg
- Cardiovascular Physics, Department of Physics, Humboldt-Universität zu Berlin, Berlin 10115, Germany
| | - Niels Wessel
- Cardiovascular Physics, Department of Physics, Humboldt-Universität zu Berlin, Berlin 10115, Germany
| | - Gustavo Pacheco-López
- Metropolitan Autonomous University (UAM), Campus Lerma, Biological and Health Sciences Division, Lerma 52005, Mexico; Swiss Federal Institute of Technology (ETH) Zurich, Department of Health Sciences, and Technology, Zurich 8092, Switzerland.
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Fontolliet T, Pichot V, Bringard A, Fagoni N, Adami A, Tam E, Furlan R, Barthélémy JC, Ferretti G. TESTING THE VAGAL WITHDRAWAL HYPOTHESIS DURING LIGHT EXERCISE UNDER AUTONOMIC BLOCKADE: A HEART RATE VARIABILITY STUDY. J Appl Physiol (1985) 2018; 125:1804-1811. [PMID: 30307822 DOI: 10.1152/japplphysiol.00619.2018] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
INTRODUCTION We performed the first analysis of heart rate variability (HRV) at rest and exercise under full autonomic blockade on the same subjects, to test the conjecture that vagal tone withdrawal occurs at exercise onset. We hypothesized that, between rest and exercise: i) no differences in total power (PTOT) under parasympathetic blockade; ii) a PTOT fall under β1-sympathetic blockade; iii) no differences in Ptot under blockade of both ANS branches. METHODS 7 males (24±3 years) performed 5-min cycling (80W) supine, preceded by 5-min rest during control and with administration of atropine, metoprolol and atropine+metoprolol (double blockade). Heart rate and arterial blood pressure were continuously recorded. HRV and blood pressure variability were determined by power spectral analysis, and baroreflex sensitivity (BRS) by the sequence method. RESULTS At rest, PTOT and the powers of low (LF) and high (HF) frequency components of HRV were dramatically decreased in atropine and double blockade compared to control and metoprolol, with no effects on LF/HF ratio and on the normalised LF (LFnu) and HF (HFnu). At exercise, patterns were the same as at rest. Comparing exercise to rest, PTOT varied as hypothesized. For SAP and DAP, resting PTOT was the same in all conditions. At exercise, in all conditions, PTOT was lower than in control. BRS decreased under atropine and double blockade at rest, under control and metoprolol during exercise. CONCLUSIONS The results support the hypothesis that vagal suppression determined disappearance of HRV during exercise.
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Affiliation(s)
| | | | - Aurélien Bringard
- Department of Basic Neurosciences, University of Geneva, Switzerland, Switzerland
| | - Nazzareno Fagoni
- Dipartment of Kinesiology, College of Health Sciences, Universita di Brescia, Italy
| | - Alessandra Adami
- Department of Kinesiology, University of Rhode Island, Kingston, RI, USA, United States
| | - Enrico Tam
- Dipartimento di Scienze Neurologiche e del Movimento, Università di Verona, Italy
| | - Raffaello Furlan
- Division of Internal Medicine, Humanitas Clinical and Research Center, Rozzano Humanitas University, Italy
| | | | - Guido Ferretti
- University of Geneva, Switzerland, and of Brescia, Italy, Switzerland
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13
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Valenza G, Duggento A, Passamonti L, Diciotti S, Tessa C, Toschi N, Barbieri R. Resting-state brain correlates of cardiovascular complexity. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2018; 2017:3317-3320. [PMID: 29060607 DOI: 10.1109/embc.2017.8037566] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
While estimates of complex heartbeat dynamics have provided effective prognostic and diagnostic markers for a wide range of pathologies, brain correlates of complex cardiac measures in general and of complex sympatho-vagal dynamics in particular are still unknown. In this study we combine resting state functional Magnetic Resonance Imaging (fMRI) and physiological signal acquisition from 34 healthy subjects selected from the Human Connectome Project (HCP) repository with inhomogeneous point-process approximate and sample heartbeat entropy measures (ipApEn and ipSampEn) to investigate brain areas involved in complex cardiovascular control. Our results show that activity in the Temporal Gyrus, Frontal Orbital Cortex, Temporal Fusiform and Opercular cortices, Planum Temporale, and Paracingulate cortex are negatively correlated with ipApEn dynamics. Activity in the same cortical areas as well as in the Temporal Fusiform cortex are negatively correlated with ipSampEn dynamics. No significant positive correlations were found. These pioneering results suggest that cardiovascular complexity at rest is linked to a few specific cortical brain structures, including crucial areas connected with parasympathetic outflow. This corroborates the hypothesis of a multidimensional central network which controls nonlinear cardiac dynamics under a predominantly vagally-driven tone.
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Nardelli M, Lanata A, Bertschy G, Scilingo EP, Valenza G. Heartbeat Complexity Modulation in Bipolar Disorder during Daytime and Nighttime. Sci Rep 2017; 7:17920. [PMID: 29263393 PMCID: PMC5738374 DOI: 10.1038/s41598-017-18036-z] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2017] [Accepted: 11/30/2017] [Indexed: 02/07/2023] Open
Abstract
This study reports on the complexity modulation of heartbeat dynamics in patients affected by bipolar disorder. In particular, a multiscale entropy analysis was applied to the R-R interval series, that were derived from electrocardiographic (ECG) signals for a group of nineteen subjects comprised of eight patients and eleven healthy control subjects. They were monitored using a textile-based sensorized t-shirt during the day and overnight for a total of 47 diurnal and 27 nocturnal recordings. Patients showed three different mood states: depression, hypomania and euthymia. Results show a clear loss of complexity during depressive and hypomanic states as compared to euthymic and healthy control states. In addition, we observed that a more significant complexity modulation among healthy and pathological mood states occurs during the night. These findings suggest that bipolar disorder is associated with an enhanced sleep-related dysregulation of the Autonomic Nervous System (ANS) activity, and that heartbeat complex dynamics may serve as a viable marker of pathological conditions in mental health.
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Affiliation(s)
- Mimma Nardelli
- Computational Physiology and Biomedical Instruments group, Department of Information Engineering & Bioengineering and Robotics Research Centre E. Piaggio, School of Engineering, University of Pisa, Pisa, Italy.
| | - Antonio Lanata
- Computational Physiology and Biomedical Instruments group, Department of Information Engineering & Bioengineering and Robotics Research Centre E. Piaggio, School of Engineering, University of Pisa, Pisa, Italy
| | - Gilles Bertschy
- Department of Psychiatry and Mental Health, Strasbourg University Hospital, INSERM U1114, University of Strasbourg - F-67000, Strasbourg, France
| | - Enzo Pasquale Scilingo
- Computational Physiology and Biomedical Instruments group, Department of Information Engineering & Bioengineering and Robotics Research Centre E. Piaggio, School of Engineering, University of Pisa, Pisa, Italy
| | - Gaetano Valenza
- Computational Physiology and Biomedical Instruments group, Department of Information Engineering & Bioengineering and Robotics Research Centre E. Piaggio, School of Engineering, University of Pisa, Pisa, Italy
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Yang Y, Aro AL, Nair SG, Jayaraman R, Reinier K, Rusinaru C, Uy-Evanado A, Yarmohammadi H, Jui J, Chugh SS. Novel measure of autonomic remodeling associated with sudden cardiac arrest in diabetes. Heart Rhythm 2017; 14:1449-1455. [PMID: 28711633 PMCID: PMC5624843 DOI: 10.1016/j.hrthm.2017.07.011] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/10/2017] [Indexed: 12/22/2022]
Abstract
BACKGROUND Diabetes is independently associated with an increased risk of sudden cardiac arrest (SCA), with a need to identify novel methods for risk stratification. Diabetic patients can develop autonomic dysfunction that has been associated with an increased risk of ventricular arrhythmogenesis and manifests as reduced heart rate variability (HRV). However, previously published studies have not accounted for resting heart rate (HR), important from both pathophysiological and prognosticating standpoints. OBJECTIVE We sought to evaluate autonomic remodeling of the sinus node response in SCA and diabetes while accounting for HR. METHODS We performed a case-control study in SCA cases (age 35-59 years; 2002-2014) from the ongoing Oregon Sudden Unexpected Death Study (catchment population ∼1 million), and archived 12-lead electrocardiograms recorded prior to the SCA event were compared with those of geographic controls. Short-term HRV was calculated from digitized 10-second electrocardiograms by using established methods. We analyzed 313 subjects (mean age 52.0 ± 5.5 years; 216 men, 69.0%) and compared 4 groups: 111 diabetic (49 cases, 62 controls) and 202 nondiabetic (80 cases, 122 controls) subjects. RESULTS Analysis of covariance showed an absence of the expected interaction between HRV and HR (HRV-HR) in diabetic patients with SCA (regression slope -0.008; 95% confidence interval -0.023 to 0.0071; P = .26). This finding, unique to this population of diabetic patients with SCA, was not detected using traditional HRV measures. CONCLUSION By incorporating resting HR in this analysis, we observed that this population of diabetic patients with SCA had loss of the expected HRV-HR relationship. This potentially novel noninvasive risk measurement warrants further investigation, especially at the level of the individual patient.
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Affiliation(s)
- Yang Yang
- Heart Institute, Cedars-Sinai Medical Center, Los Angeles, California
| | - Aapo L Aro
- Heart Institute, Cedars-Sinai Medical Center, Los Angeles, California; Heart and Lung Center, Helsinki University Hospital, Helsinki, Finland
| | - Sandeep G Nair
- Heart Institute, Cedars-Sinai Medical Center, Los Angeles, California
| | - Reshmy Jayaraman
- Heart Institute, Cedars-Sinai Medical Center, Los Angeles, California
| | - Kyndaron Reinier
- Heart Institute, Cedars-Sinai Medical Center, Los Angeles, California
| | - Carmen Rusinaru
- Heart Institute, Cedars-Sinai Medical Center, Los Angeles, California
| | - Audrey Uy-Evanado
- Heart Institute, Cedars-Sinai Medical Center, Los Angeles, California
| | | | - Jonathan Jui
- Oregon Health and Science University, Portland, Oregon
| | - Sumeet S Chugh
- Heart Institute, Cedars-Sinai Medical Center, Los Angeles, California.
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Vandendriessche B, Abas M, Dick TE, Loparo KA, Jacono FJ. A Framework for Patient State Tracking by Classifying Multiscalar Physiologic Waveform Features. IEEE Trans Biomed Eng 2017; 64:2890-2900. [PMID: 28328498 DOI: 10.1109/tbme.2017.2684244] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
OBJECTIVE state-of-the-art algorithms that quantify nonlinear dynamics in physiologic waveforms are underutilized clinically due to their esoteric nature. We present a generalizable framework for classifying multiscalar waveform features, designed for patient-state tracking directly at the bedside. METHODS an artificial neural network classifier was designed to evaluate multiscale waveform features against a fingerprint database of multifractal synthetic time series. The results are mapped into a physiologic state space for near real-time patient-state tracking. RESULTS the framework was validated on cardiac beat-to-beat dynamics processed with the multiscale entropy algorithm, and assessed using PhysioNet databases. We then applied our algorithm to predict 28-day mortality for sepsis patients, and found it had greater prognostic accuracy than standard clinical severity scores. CONCLUSION we developed a novel framework to classify multiscale features of beat-to-beat dynamics, and performed an initial clinical validation to demonstrate that our approach generates a robust quantification of a patient's state, compatible with real-time bedside implementations. SIGNIFICANCE the framework generates meaningful and actionable patient-specific information, and could facilitate the dissemination of a new class of "always-on" diagnostic tools.
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17
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Silva LEV, Silva CAA, Salgado HC, Fazan R. The role of sympathetic and vagal cardiac control on complexity of heart rate dynamics. Am J Physiol Heart Circ Physiol 2017; 312:H469-H477. [DOI: 10.1152/ajpheart.00507.2016] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/19/2016] [Revised: 12/05/2016] [Accepted: 12/20/2016] [Indexed: 11/22/2022]
Abstract
Analysis of heart rate variability (HRV) by nonlinear approaches has been gaining interest due to their ability to extract additional information from heart rate (HR) dynamics that are not detectable by traditional approaches. Nevertheless, the physiological interpretation of nonlinear approaches remains unclear. Therefore, we propose long-term (60 min) protocols involving selective blockade of cardiac autonomic receptors to investigate the contribution of sympathetic and parasympathetic function upon nonlinear dynamics of HRV. Conscious male Wistar rats had their electrocardiogram (ECG) recorded under three distinct conditions: basal, selective (atenolol or atropine), or combined (atenolol plus atropine) pharmacological blockade of autonomic muscarinic or β1-adrenergic receptors. Time series of RR interval were assessed by multiscale entropy (MSE) and detrended fluctuation analysis (DFA). Entropy over short (1 to 5, MSE1–5) and long (6 to 30, MSE6–30) time scales was computed, as well as DFA scaling exponents at short (αshort, 5 ≤ n ≤ 15), mid (αmid, 30 ≤ n ≤ 200), and long (αlong, 200 ≤ n ≤ 1,700) window sizes. The results show that MSE1–5 is reduced under atropine blockade and MSE6–30 is reduced under atropine, atenolol, or combined blockade. In addition, while atropine expressed its maximal effect at scale six, the effect of atenolol on MSE increased with scale. For DFA, αshort decreased during atenolol blockade, while the αmid increased under atropine blockade. Double blockade decreased αshort and increased αlong. Results with surrogate data show that the dynamics during combined blockade is not random. In summary, sympathetic and vagal control differently affect entropy (MSE) and fractal properties (DFA) of HRV. These findings are important to guide future studies. NEW & NOTEWORTHY Although multiscale entropy (MSE) and detrended fluctuation analysis (DFA) are recognizably useful prognostic/diagnostic methods, their physiological interpretation remains unclear. The present study clarifies the effect of the cardiac autonomic control on MSE and DFA, assessed during long periods (1 h). These findings are important to help the interpretation of future studies.
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Affiliation(s)
| | | | - Helio Cesar Salgado
- Department of Physiology, Ribeirão Preto Medical School, University of São Paulo, São Paulo, Brazil
| | - Rubens Fazan
- Department of Physiology, Ribeirão Preto Medical School, University of São Paulo, São Paulo, Brazil
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18
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Dimitriev DA, Saperova EV, Dimitriev AD. State Anxiety and Nonlinear Dynamics of Heart Rate Variability in Students. PLoS One 2016; 11:e0146131. [PMID: 26807793 PMCID: PMC4726749 DOI: 10.1371/journal.pone.0146131] [Citation(s) in RCA: 56] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2015] [Accepted: 12/14/2015] [Indexed: 01/01/2023] Open
Abstract
OBJECTIVES Clinical and experimental research studies have demonstrated that the emotional experience of anxiety impairs heart rate variability (HRV) in humans. The present study investigated whether changes in state anxiety (SA) can also modulate nonlinear dynamics of heart rate. METHODS A group of 96 students volunteered to participate in the study. For each student, two 5-minute recordings of beat intervals (RR) were performed: one during a rest period and one just before a university examination, which was assumed to be a real-life stressor. Nonlinear analysis of HRV was performed. The Spielberger's State-Trait Anxiety Inventory was used to assess the level of SA. RESULTS Before adjusting for heart rate, a Wilcoxon matched pairs test showed significant decreases in Poincaré plot measures, entropy, largest Lyapunov exponent (LLE), and pointwise correlation dimension (PD2), and an increase in the short-term fractal-like scaling exponent of detrended fluctuation analysis (α1) during the exam session, compared with the rest period. A Pearson analysis indicated significant negative correlations between the dynamics of SA and Poincaré plot axes ratio (SD1/SD2), and between changes in SA and changes in entropy measures. A strong negative correlation was found between the dynamics of SA and LLE. A significant positive correlation was found between the dynamics of SA and α1. The decreases in Poincaré plot measures (SD1, complex correlation measure), entropy measures, and LLE were still significant after adjusting for heart rate. Corrected α1 was increased during the exam session. As before, the dynamics of adjusted LLE was significantly correlated with the dynamics of SA. CONCLUSIONS The qualitative increase in SA during academic examination was related to the decrease in the complexity and size of the Poincaré plot through a reduction of both the interbeat interval and its variation.
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Affiliation(s)
- Dimitriy A. Dimitriev
- Department of Biology, Chuvash State Pedagogical University, Chuvash Republic, Russia
- * E-mail:
| | - Elena V. Saperova
- Department of Biology, Chuvash State Pedagogical University, Chuvash Republic, Russia
| | - Aleksey D. Dimitriev
- Department of Biology, Chuvash State Pedagogical University, Chuvash Republic, Russia
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19
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Uhrikova Z, Zibolen M, Javorka K, Chladekova L, Javorka M. Hyperbilirubinemia and phototherapy in newborns: Effects on cardiac autonomic control. Early Hum Dev 2015; 91:351-6. [PMID: 25919997 DOI: 10.1016/j.earlhumdev.2015.03.009] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/12/2014] [Revised: 12/18/2014] [Accepted: 03/23/2015] [Indexed: 10/23/2022]
Abstract
BACKGROUND Neonatal jaundice and its phototherapeutic treatment can lead to several side effects involving activation of autonomic control mechanisms. AIM The aims of this study are to investigate the autonomic nervous system changes in icteric neonates using heart rate variability (HRV) and to assess the effect of phototherapy on short-term heart rate dynamics as an indicator of autonomic nervous control of cardiovascular system. METHODS HRV recordings from 20 icteric full-term neonates before, during and after phototherapy and from 20 healthy controls were analyzed. In addition to traditional time and frequency domain measures, heart rate complexity parameters including normalized complexity index (NCI), normalized unpredictability index (NUPI), pattern classification indices (0V%, 1V%, 2LV%, 2UV%) and irreversibility index (P%) on four time scales were evaluated. All measures were derived from data segments of 1000 RR intervals. RESULTS The analysis revealed higher values of 1V%, 2LV%, and lower P% in neonates with hyperbilirubinemia compared to controls. While HRV magnitude did not change, mean heart rate increased during and after the phototherapy. Nonlinear analysis showed a decrease of complexity, unpredictability and pattern classification measures 2LV% and 2UV%. In contrast, 0V% and irreversibility index P% were increased during and at least 30min after phototherapy. CONCLUSION The results suggest a shifted autonomic balance in icteric neonates compared to the controls and its further alterations during phototherapy. As the nonlinear HRV parameters are independent of the linear methods, they can provide new information about the cardiac regulatory mechanisms and their changes in neonates.
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Affiliation(s)
- Zuzana Uhrikova
- Clinic of Neonatology, Comenius University, Jessenius Faculty of Medicine and University Hospital, Kollarova 2, 03601 Martin, Slovakia.
| | - Mirko Zibolen
- Clinic of Neonatology, Comenius University, Jessenius Faculty of Medicine and University Hospital, Kollarova 2, 03601 Martin, Slovakia.
| | - Kamil Javorka
- Department of Physiology, Comenius University, Jessenius Faculty of Medicine, Mala Hora 4, 03601 Martin, Slovakia.
| | - Lenka Chladekova
- Department of Physiology, Comenius University, Jessenius Faculty of Medicine, Mala Hora 4, 03601 Martin, Slovakia
| | - Michal Javorka
- Department of Physiology, Comenius University, Jessenius Faculty of Medicine, Mala Hora 4, 03601 Martin, Slovakia.
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20
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Valenza G, Garcia RG, Citi L, Scilingo EP, Tomaz CA, Barbieri R. Nonlinear digital signal processing in mental health: characterization of major depression using instantaneous entropy measures of heartbeat dynamics. Front Physiol 2015; 6:74. [PMID: 25821435 PMCID: PMC4358071 DOI: 10.3389/fphys.2015.00074] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2014] [Accepted: 02/23/2015] [Indexed: 11/13/2022] Open
Abstract
Nonlinear digital signal processing methods that address system complexity have provided useful computational tools for helping in the diagnosis and treatment of a wide range of pathologies. More specifically, nonlinear measures have been successful in characterizing patients with mental disorders such as Major Depression (MD). In this study, we propose the use of instantaneous measures of entropy, namely the inhomogeneous point-process approximate entropy (ipApEn) and the inhomogeneous point-process sample entropy (ipSampEn), to describe a novel characterization of MD patients undergoing affective elicitation. Because these measures are built within a nonlinear point-process model, they allow for the assessment of complexity in cardiovascular dynamics at each moment in time. Heartbeat dynamics were characterized from 48 healthy controls and 48 patients with MD while emotionally elicited through either neutral or arousing audiovisual stimuli. Experimental results coming from the arousing tasks show that ipApEn measures are able to instantaneously track heartbeat complexity as well as discern between healthy subjects and MD patients. Conversely, standard heart rate variability (HRV) analysis performed in both time and frequency domains did not show any statistical significance. We conclude that measures of entropy based on nonlinear point-process models might contribute to devising useful computational tools for care in mental health.
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Affiliation(s)
- Gaetano Valenza
- Department of Anesthesia, Critical Care & Pain Medicine, Massachusetts General Hospital, Harvard Medical School Boston, MA, USA ; Massachusetts Institute of Technology Cambridge, MA, USA ; Department of Information Engineering, Research Center E. Piaggio, University of Pisa Pisa, Italy
| | - Ronald G Garcia
- Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital Charlestown, MA, USA ; Department of Psychiatry, Masira Research Institute, Medical School, Universidad de Santander Bucaramanga, Colombia
| | - Luca Citi
- School of Computer Science and Electronic Engineering, University of Essex Colchester, UK
| | - Enzo P Scilingo
- Department of Information Engineering, Research Center E. Piaggio, University of Pisa Pisa, Italy
| | - Carlos A Tomaz
- Laboratory of Neuroscience and Behavior, Universidade de Brasilia Brasilia, Brazil
| | - Riccardo Barbieri
- Department of Anesthesia, Critical Care & Pain Medicine, Massachusetts General Hospital, Harvard Medical School Boston, MA, USA
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21
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Javorka M, Turianikova Z, Tonhajzerova I, Lazarova Z, Czippelova B, Javorka K. Heart rate and blood pressure control in obesity - how to detect early dysregulation? Clin Physiol Funct Imaging 2015; 36:337-45. [DOI: 10.1111/cpf.12234] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2014] [Accepted: 01/06/2015] [Indexed: 01/24/2023]
Affiliation(s)
- Michal Javorka
- Department of Physiology; Jessenius Faculty of Medicine; Comenius University; Martin Slovakia
| | - Zuzana Turianikova
- Department of Physiology; Jessenius Faculty of Medicine; Comenius University; Martin Slovakia
| | - Ingrid Tonhajzerova
- Department of Physiology; Jessenius Faculty of Medicine; Comenius University; Martin Slovakia
| | - Zuzana Lazarova
- Department of Physiology; Jessenius Faculty of Medicine; Comenius University; Martin Slovakia
| | - Barbora Czippelova
- Department of Physiology; Jessenius Faculty of Medicine; Comenius University; Martin Slovakia
| | - Kamil Javorka
- Department of Physiology; Jessenius Faculty of Medicine; Comenius University; Martin Slovakia
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22
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Yaniv Y, Lyashkov AE, Lakatta EG. The fractal-like complexity of heart rate variability beyond neurotransmitters and autonomic receptors: signaling intrinsic to sinoatrial node pacemaker cells. ACTA ACUST UNITED AC 2013; 2. [PMID: 26709383 DOI: 10.4172/2329-6607.1000111] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The heart rate and rhythm are controlled by complex chaotic neural, chemical and hormonal networks which are not strictly regular, but exhibit fluctuations across multiple time scales. A careful assessment of the heart rate variability (HRV) offers clues to this complexity. A reduction in HRV, specifically in advanced age, is associated with increase in morbidity and mortality. Mechanisms that induce this decrease, however, have not been fully elucidated. The classical literature characterizes changes in HRV as a result of changes in the balance of competing influences of the sympathetic and parasympathetic autonomic impulses delivered to the heart. It has now become clear, however, that the heart rate and HRV are also determined by intrinsic properties of the pacemaker cells that comprise sinoatrial node, and that these properties respond to autonomic receptor stimulation in a non-linear mode. That HRV is determined by both the intrinsic properties of pacemaker cells in the sinoatrial node and the competing influences of the two branches of the autonomic neural input to the cells requires an expansion of our perspective about mechanisms that govern HRV in the normal heart, and how HRV changes with aging in health and in heart diseases.
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Affiliation(s)
- Yael Yaniv
- Laboratory of Cardiovascular Science, Biomedical Research Center, Intramural Research Program, National Institute on Aging, NIH, Baltimore, Maryland, USA
| | - Alexey E Lyashkov
- Department of Molecular and Comparative Pathobiology, Johns Hopkins University School of Medicine, 733 North Broadway, Baltimore, Maryland, USA
| | - Edward G Lakatta
- Laboratory of Cardiovascular Science, Biomedical Research Center, Intramural Research Program, National Institute on Aging, NIH, Baltimore, Maryland, USA
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23
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Mendes RG, Simões RP, Costa FDSM, Pantoni CBF, Di Thommazo-Luporini L, Luzzi S, Amaral-Neto O, Arena R, Catai AM, Borghi-Silva A. Is applying the same exercise-based inpatient program to normal and reduced left ventricular function patients the best strategy after coronary surgery? A focus on autonomic cardiac response. Disabil Rehabil 2013; 36:155-62. [PMID: 23651129 DOI: 10.3109/09638288.2013.782362] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
PURPOSE To assess whether the same exercise-based inpatient program applied to patients with normal and reduced left ventricular function (LVF) evokes a similar cardiac autonomic response after coronary artery bypass graft (CABG). METHOD Forty-four patients post-CABG, subgrouped according to normal LVF [LVFN: n = 23; left ventricular ejection fraction (LVEF) ≥ 55%] and reduced LVF (LVFR: n = 21; LVEF 35-54%), were included. All initiated the exercise protocol on post-operative day 1 (PO1), following a whole progressive program until discharge. Cardiac autonomic response was assessed by the indices of heart rate variability (HRV) at rest and during exercise (extremity range of motion and ambulation). RESULTS During ambulation, lower values of HRV indices were found in the LVFR group compared with the LVFN group [standard deviation of all RR (STDRR; 6.1 ± 2.7 versus 8.9 ± 4.7 ms), baseline width of the RR histogram (TINN; 30.6 ± 14.8 versus 45.8 ± 24.9 ms), SD2 (14.8 ± 8.0 versus 21.3 ± 9.0 ms), Shannon entropy (3.6 ± 0.5 versus 3.9 ± 0.4) and correlation dimension (0.08 ± 0.2 versus 0.2 ± 0.2)]. Also, when comparing the ambulation to rest change, lower values were observed in the LVFR group for linear (STDRR, TINN, RR TRI, rMSSD) and non-linear (SD2 and correlation dimension) HRV indices (p < 0.05). On PO1, we observed only intra-group differences between rest and exercise (extremity range of motion), for mean intervals between heart beats and heart rate. CONCLUSION For patients with LVFN, the same inpatient exercise protocol triggered a more attenuated autonomic response compared with patients with LVFR. These findings have implications as to how exercise should be prescribed according to LVF in the early stages following recovery from CABG. Implications for Rehabilitation Exercise-based inpatient program, performed by post-CABG patients who have normal left ventricular function, triggered a more attenuated cardiac autonomic response compared with patients with reduced left ventricular function. Volume of the inpatient exercises should be prescribed according to the left ventricular function in the early stages following recovery from CABG.
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Affiliation(s)
- Renata Gonçalves Mendes
- Cardiopulmonary Physiotherapy Laboratory, Nucleus of Research in Physical Exercise, Federal University of Sao Carlos , Sao Paulo , Brazil
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24
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Valenza G, Lanatá A, Scilingo EP. Improving emotion recognition systems by embedding cardiorespiratory coupling. Physiol Meas 2013; 34:449-64. [PMID: 23524596 DOI: 10.1088/0967-3334/34/4/449] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
This work aims at showing improved performances of an emotion recognition system embedding information gathered from cardiorespiratory (CR) coupling. Here, we propose a novel methodology able to robustly identify up to 25 regions of a two-dimensional space model, namely the well-known circumplex model of affect (CMA). The novelty of embedding CR coupling information in an autonomic nervous system-based feature space better reveals the sympathetic activations upon emotional stimuli. A CR synchrogram analysis was used to quantify such a coupling in terms of number of heartbeats per respiratory period. Physiological data were gathered from 35 healthy subjects emotionally elicited by means of affective pictures of the international affective picture system database. In this study, we finely detected five levels of arousal and five levels of valence as well as the neutral state, whose combinations were used for identifying 25 different affective states in the CMA plane. We show that the inclusion of the bivariate CR measures in a previously developed system based only on monovariate measures of heart rate variability, respiration dynamics and electrodermal response dramatically increases the recognition accuracy of a quadratic discriminant classifier, obtaining more than 90% of correct classification per class. Finally, we propose a comprehensive description of the CR coupling during sympathetic elicitation adapting an existing theoretical nonlinear model with external driving. The theoretical idea behind this model is that the CR system is comprised of weakly coupled self-sustained oscillators that, when exposed to an external perturbation (i.e. sympathetic activity), becomes synchronized and less sensible to input variations. Given the demonstrated role of the CR coupling, this model can constitute a general tool which is easily embedded in other model-based emotion recognition systems.
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Affiliation(s)
- Gaetano Valenza
- Department of Information Engineering and Research Center E. Piaggio, Faculty of Engineering, University of Pisa, Via G Caruso 16, I-56122 Pisa, Italy.
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25
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Lin CL, Jung TP, Chuang SW, Duann JR, Lin CT, Chiu TW. Self-adjustments may account for the contradictory correlations between HRV and motion-sickness severity. Int J Psychophysiol 2012; 87:70-80. [PMID: 23159509 DOI: 10.1016/j.ijpsycho.2012.11.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2012] [Revised: 09/21/2012] [Accepted: 11/03/2012] [Indexed: 10/27/2022]
Abstract
This study investigates the relationship between heart rate variability (HRV) and the level of motion sickness (MS) induced by simulated tunnel driving. The HRV indices, normalized low frequency (NLF, 0.04-0.15 Hz), normalized high frequency (NHF, 0.15-0.4 Hz), and LF/HF ratio were correlated with the subjectively and continuously rated MS levels of 20 participants. The experimental results showed that for 13 of the subjects, the MS levels positively correlated with the NLF and the LF/HF ratio and negatively correlated with the NHF. The remaining seven subjects had negative correlations between the MS levels and the NLF and the LF/HF ratio and a positive correlation between the MS levels and the NHF. To clarify this contradiction, this study also inspected the effects of subjects' self-adjustments on the correlations between the MS levels and the HRV indices and showed that the variations in the relationship might be attributed to the subjects' self-adjustments, which they used to relieve the discomfort of MS.
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Affiliation(s)
- Chun-Ling Lin
- Brain Research Center, University System of Taiwan, Hsinchu, Taiwan
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26
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Abstract
This paper reviews various nonlinear analysis methods for physiological signals. The assessment is based on a discussion of chaos-inspired methods, such as fractal dimension (FD), correlation dimension (D2), largest Lyapunov exponet (LLE), Renyi's entropy (REN), Shannon spectral entropy (SEN), and approximate entropy (ApEn). We document that these methods are used to extract discriminative features from electroencephalograph (EEG) and heart rate variability (HRV) signals by reviewing the relevant scientific literature. EEG features can be used to support the diagnosis of epilepsy and HRV features can be used to support the diagnosis of cardiovascular diseases as well as diabetes. Documenting the widespread use of these and other nonlinear methods supports our thesis that the study of feature extraction methods, based on the chaos theory, is an important subject which has been gaining more and significance in biomedical engineering. We adopt the position that pursuing research in the field of biomedical engineering is ultimately a progmatic activity, where it is necessary to engage in features that work. In this case, the nonlinear features are working well, even if we do not have conclusive evidence that the underlying physiological phenomena are indeed chaotic.
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Affiliation(s)
- OLIVER FAUST
- Ngee Ann Polytechnic, School of Engineering, Electroinic and Computer Engineering Division, 535 Clementi Road, Singapore 599489, Singapore
| | - MURALIDHAR G. BAIRY
- Department of Biomedical Engineering, Manipal Institute of Technology, Manipal, India
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27
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De Vera L, Rial RV, Pereda E, González JJ. Autonomic mediation of the interdependence between variability signals of heart rate and blood pressure in the lizard Gallotia galloti. CAN J ZOOL 2012. [DOI: 10.1139/z2012-052] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Autonomic nervous system (ANS) involvement in the mediation of the synchronization between beat-to-beat RR interval variability (RRIV) and systolic blood pressure variability (SBPV) signals of the lizard Gallotia galloti (Oudart, 1839) was investigated through linear and nonlinear time series analysis methods in a pharmacological blockade context. The ANS blockers used were atropine, prazosin, and propranolol. The interdependence between the signals was quantified by means of the magnitude-squared coherence (MSC), which measures amplitude and phase linear synchronization; the phase lag index (PLI), which evaluates the phase synchronization; and the index L, which quantifies the generalized linear and nonlinear synchronization. Atropine decreased the PLI in the low-frequency (LF: 0.01–0.05 Hz) range; prazosin decreased the MSC in the medium-frequency (MF: 0.06–0.15 Hz) range; and propranolol did not alter any of the interdependence measures. It is suggested that (i) the cholinoceptor activity mediates the phase cardiovascular synchronization in the LF range; (ii) the α1-adrenoceptor activity mediates the amplitude and phase linear cardiovascular synchronization in the MF range; and (iii) the β-adrenoceptor activity plays no role in mediating any dynamics of cardiovascular synchronization in the studied frequency range. When comparing these results with those in mammals, a lesser overall autonomic involvement in the mediation of the studied cardiovascular interdependences is seen in reptiles.
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Affiliation(s)
- Luis De Vera
- Laboratory of Biophysics, Department of Physiology, University of La Laguna, 38071-La Laguna, Tenerife, Canary Islands, Spain
| | - Rubén V. Rial
- Institut Universitari de Ciencies de la Salut, Universitat de les Illes Balears, 07071-Palma de Mallorca, Mallorca, Illes Balears, Spain
| | - Ernesto Pereda
- Electrical Engineering and Bioengineering Group, Department of Basic Physics, University of La Laguna, 38206-La Laguna, Tenerife, Canary Islands, Spain
| | - Julián J. González
- Laboratory of Biophysics, Department of Physiology, University of La Laguna, 38071-La Laguna, Tenerife, Canary Islands, Spain
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Reinhard J, Hayes-Gill BR, Schiermeier S, Hatzmann W, Heinrich TM, Hüsken-Janßen H, Herrmann E, Louwen F. Change of Spectral Analysis of Fetal Heart Rate During Clinical Hypnosis: a Prospective Randomised Trial from the 20th Week of Gestation Till Term. Geburtshilfe Frauenheilkd 2012; 72:316-321. [PMID: 25284838 DOI: 10.1055/s-0031-1298399] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2011] [Revised: 01/31/2012] [Accepted: 02/28/2012] [Indexed: 01/13/2023] Open
Abstract
Objective: To investigate the functional adaptive process of the fetal autonomic nervous system during hypnosis from the 20th week of gestation till term. Are there changes in the power spectrum analysis of fetal heart rate when the mother is having a clinical hypnosis or control period? Study Design: Fourty-nine FHR recordings were analysed. Included recordings were from singletons and abdominal fetal ECG-monitored pregnancies. All women were randomised to receive clinical hypnosis followed by a period with no intervention or vice versa. Statistical analyses were performed with the Wilcoxon signed ranks and Spearman rho correlation tests. Results: There was a significant difference found between fetal heart rate at baseline (144.3 ± 6.0) and hypnosis (142.1 ± 6.4). A difference was also detected between the standard deviation of the heart rate between baseline (6.7 ± 1.9) and hypnosis (6.8 ± 3.5). LFnu was smaller during baseline (80.2 ± 5.3) than during hypnosis (82.1 ± 5.7), whereas HFnu was significantly larger (19.8 ± 5.3 vs. 17.9 ± 5.7). There was no correlation between the gestation age and the change in LFnu, HFnu or ratio LF/HF due to the hypnosis intervention. Conclusion: The functional adaptive process of the fetal autonomic system during hypnosis is reflected by a sympathovagal shift towards increased sympathetic modulation.
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Affiliation(s)
- J Reinhard
- Obstetrics and Gynaecology Department, Johann Wolfgang Goethe University Frankfurt, Frankfurt
| | - B R Hayes-Gill
- School of Electrical and Electronic Engineering, University of Nottingham, Nottingham, United Kingdom
| | - S Schiermeier
- Obstetrics and Gynaecology, Teaching Hospital of the Ruhr-University Bochum, Witten
| | - W Hatzmann
- Obstetrics and Gynaecology, Teaching Hospital of the Ruhr-University Bochum, Witten
| | - T M Heinrich
- Obstetrics and Gynaecology Department, Johann Wolfgang Goethe University Frankfurt, Frankfurt
| | - H Hüsken-Janßen
- Deutsche Gesellschaft für Hypnose und Hypnotherapie, German Society for Clinical Hypnosis, Coesfeld
| | - E Herrmann
- Department of Biostatistics and Mathematical Models, Johann Wolfgang Goethe University Frankfurt am Main, Frankfurt
| | - F Louwen
- Obstetrics and Gynaecology Department, Johann Wolfgang Goethe University Frankfurt, Frankfurt
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Kunz VC, Borges EN, Coelho RC, Gubolino LA, Martins LEB, Silva E. Linear and nonlinear analysis of heart rate variability in healthy subjects and after acute myocardial infarction in patients. Braz J Med Biol Res 2012; 45:450-8. [PMID: 22370707 PMCID: PMC3854283 DOI: 10.1590/s0100-879x2012007500025] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2011] [Accepted: 02/07/2012] [Indexed: 11/22/2022] Open
Abstract
The objectives of this study were to evaluate and compare the use of linear and nonlinear methods for analysis of heart rate variability (HRV) in healthy subjects and in patients after acute myocardial infarction (AMI). Heart rate (HR) was recorded for 15 min in the supine position in 10 patients with AMI taking β-blockers (aged 57 ± 9 years) and in 11 healthy subjects (aged 53 ± 4 years). HRV was analyzed in the time domain (RMSSD and RMSM), the frequency domain using low- and high-frequency bands in normalized units (nu; LFnu and HFnu) and the LF/HF ratio and approximate entropy (ApEn) were determined. There was a correlation (P < 0.05) of RMSSD, RMSM, LFnu, HFnu, and the LF/HF ratio index with the ApEn of the AMI group on the 2nd (r = 0.87, 0.65, 0.72, 0.72, and 0.64) and 7th day (r = 0.88, 0.70, 0.69, 0.69, and 0.87) and of the healthy group (r = 0.63, 0.71, 0.63, 0.63, and 0.74), respectively. The median HRV indexes of the AMI group on the 2nd and 7th day differed from the healthy group (P < 0.05): RMSSD = 10.37, 19.95, 24.81; RMSM = 23.47, 31.96, 43.79; LFnu = 0.79, 0.79, 0.62; HFnu = 0.20, 0.20, 0.37; LF/HF ratio = 3.87, 3.94, 1.65; ApEn = 1.01, 1.24, 1.31, respectively. There was agreement between the methods, suggesting that these have the same power to evaluate autonomic modulation of HR in both AMI patients and healthy subjects. AMI contributed to a reduction in cardiac signal irregularity, higher sympathetic modulation and lower vagal modulation.
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Affiliation(s)
- V C Kunz
- Laboratório de Fisioterapia Cardiovascular, Núcleo de Pesquisa em Exercício Físico, Departamento de Fisioterapia, Universidade Federal de São Carlos, SP, Brasil.
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Turianikova Z, Javorka K, Baumert M, Calkovska A, Javorka M. The effect of orthostatic stress on multiscale entropy of heart rate and blood pressure. Physiol Meas 2011; 32:1425-37. [PMID: 21799239 DOI: 10.1088/0967-3334/32/9/006] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Cardiovascular control acts over multiple time scales, which introduces a significant amount of complexity to heart rate and blood pressure time series. Multiscale entropy (MSE) analysis has been developed to quantify the complexity of a time series over multiple time scales. In previous studies, MSE analyses identified impaired cardiovascular control and increased cardiovascular risk in various pathological conditions. Despite the increasing acceptance of the MSE technique in clinical research, information underpinning the involvement of the autonomic nervous system in the MSE of heart rate and blood pressure is lacking. The objective of this study is to investigate the effect of orthostatic challenge on the MSE of heart rate and blood pressure variability (HRV, BPV) and the correlation between MSE (complexity measures) and traditional linear (time and frequency domain) measures. MSE analysis of HRV and BPV was performed in 28 healthy young subjects on 1000 consecutive heart beats in the supine and standing positions. Sample entropy values were assessed on scales of 1-10. We found that MSE of heart rate and blood pressure signals is sensitive to changes in autonomic balance caused by postural change from the supine to the standing position. The effect of orthostatic challenge on heart rate and blood pressure complexity depended on the time scale under investigation. Entropy values did not correlate with the mean values of heart rate and blood pressure and showed only weak correlations with linear HRV and BPV measures. In conclusion, the MSE analysis of heart rate and blood pressure provides a sensitive tool to detect changes in autonomic balance as induced by postural change.
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Affiliation(s)
- Zuzana Turianikova
- Department of Physiology, Jessenius Faculty of Medicine, Comenius University, Martin, Slovak Republic
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Castiglioni P, Parati G, Di Rienzo M, Carabalona R, Cividjian A, Quintin L. Scale exponents of blood pressure and heart rate during autonomic blockade as assessed by detrended fluctuation analysis. J Physiol 2010; 589:355-69. [PMID: 21115648 DOI: 10.1113/jphysiol.2010.196428] [Citation(s) in RCA: 101] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
How the autonomic nervous system influences the fractal dynamics of heart rate (HR) and blood pressure (BP) remains unclear. The purpose of our study was to separately assess cardiac vagal and sympathetic (cardiac vs. vascular) influences on fractal properties of HR and BP as described by scale exponents of detrended fluctuation analysis (DFA). R-R intervals, systolic and diastolic BP were measured in nine supine volunteers before and after administration of autonomic blocking agents (atropine, propranolol, atropine+propranolol, clonidine). Spectra of DFA scale exponents, α(t), were calculated for scales between 5 and 100 s. HR and BP scale structures differed at baseline, being α(t) of HR <1, with a minimum between 10 and 20 s followed by a higher plateau between 40 to 80 s, while α(t) of BP decreased with t from values >1. Comparison of atropine and propranolol with baseline and combined cardiac parasympathetic and sympathetic blockade (atropine+propranolol) indicated opposite influences of vagal and cardiac sympathetic outflows on HR exponents. The vagal outflow adds white-noise components, amplifying differences with BP exponents; the cardiac sympathetic outflow adds Brownian motion components at short scales and contributes to the plateau between 40 and 80 s. Overall sympathetic inhibition by clonidine decreased short- and long-term exponents of HR, and short-term exponents of BP, so that their α(t) spectra had different means but similar profiles. Therefore, cardiac vagal, cardiac sympathetic and vascular sympathetic outflows contribute differently to HR and BP fractal structures. Results are explained by different distribution and dynamics of acetylcholine receptors and of α- and β-adrenergic receptors between heart and vasculature.
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Javorka M, Lazarova Z, Tonhajzerova I, Turianikova Z, Honzikova N, Fiser B, Javorka K, Baumert M. Baroreflex analysis in diabetes mellitus: linear and nonlinear approaches. Med Biol Eng Comput 2010; 49:279-88. [DOI: 10.1007/s11517-010-0707-x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2010] [Accepted: 10/21/2010] [Indexed: 10/18/2022]
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33
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Pereira-Junior PP, Marocolo M, Rodrigues FP, Medei E, Nascimento JH. Noninvasive method for electrocardiogram recording in conscious rats: feasibility for heart rate variability analysis. AN ACAD BRAS CIENC 2010; 82:431-7. [DOI: 10.1590/s0001-37652010000200019] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2008] [Accepted: 08/31/2009] [Indexed: 11/22/2022] Open
Abstract
Heart rate variability (HRV) analysis consists in a well-established tool for the assessment of cardiac autonomic control, both in humans and in animal models. Conventional methods for HRV analysis in rats rely on conscious state electrocardiogram (ECG) recording based on prior invasive surgical procedures for electrodes/transmitters implants. The aim of the present study was to test a noninvasive and inexpensive method for ECG recording in conscious rats, assessing its feasibility for HRV analysis. A custom-made elastic cotton jacket was developed to fit the rat's mean thoracic circumference, with two pieces of platinum electrodes attached on its inner surface, allowing ECG to be recorded noninvasively in conscious, restrained rats (n=6). Time- and frequency-domain HRV analyses were conducted, under basal and autonomic blockade conditions. High-quality ECG signals were obtained, being feasible for HRV analysis. As expected, mean RR interval was significantly decreased in the presence of atropine (p <0.05) and increased in the presence of propranolol (p<0.001). Also, reinforcing the reliability of the method, low- and high-frequency HRV spectral powers were significantly decreased in the presence of propranolol (p <0.05) and atropine (p< 0.001), respectively. In summary, the present work describes a novel, inexpensive and noninvasive method for surface ECG recording in conscious rats.
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Allers KA, Richards N, Scott L, Sweatman C, Cheung J, Reynolds D, Casey JH, Wayman C. II. Slow Oscillations in Vaginal Blood Flow: Regulation of Vaginal Blood Flow Patterns in Rat by Central and Autonomic Mechanisms. J Sex Med 2010; 7:1088-103. [DOI: 10.1111/j.1743-6109.2009.01466.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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35
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Almoznino-Sarafian D, Sarafian G, Zyssman I, Shteinshnaider M, Tzur I, Kaplan BZ, Berman S, Cohen N, Gorelik O. Application of HRV-CD for estimation of life expectancy in various clinical disorders. Eur J Intern Med 2009; 20:779-83. [PMID: 19892308 DOI: 10.1016/j.ejim.2009.08.006] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/03/2009] [Revised: 08/05/2009] [Accepted: 08/21/2009] [Indexed: 01/11/2023]
Abstract
BACKGROUND Low heart rate variability (HRV) was found in various medical conditions including heart failure and acute myocardial infarction. Decreased HRV in these conditions predicted poor prognosis. METHODS HRV was estimated in 133 unselected inpatients with relevant clinical bedside conditions by non-linear analysis derived from chaos theory, which calculates the correlation dimension (CD) of the cardiac electrophysiologic system (HRV-CD). RESULTS Mean HRV-CD in the entire group was 3.75+/-0.45. Heart failure, coronary artery disease, cardiac arrhythmia, low serum potassium, renal dysfunction, and diabetes mellitus were significantly associated with reduced HRV-CD compared to their counterparts [3.6 vs. 3.9 (P<.001), 3.65 vs. 3.87 (P=.005), 3.58 vs. 3.8 (P=.01), 3.38 vs. 3.81 (P=.02), 3.59 vs. 3.8 (P=.04), and 3.66 vs. 3.82 (P=.04), respectively]. Stepwise logistic regression showed heart failure to be the condition most significantly associated with low HRV-CD (odds ratio 4.2, 95% confidence interval 1.90-9.28, P<.001). In the entire group, decreased HRV-CD (< or =3.75 vs. >3.75) was associated with lower survival (P=.01). Mortality of diabetic patients with HRV-CD < or =3.75 exceeded the mortality in patients with HRV-CD >3.75 (P=.02). Heart failure, renal dysfunction or age over 70 combined with HRV-CD < or =3.75 also appeared to be associated with augmented mortality. CONCLUSIONS Diminished HRV-CD is associated with heart failure, coronary artery disease, cardiac arrhythmia, renal dysfunction, diabetes mellitus and low serum potassium. Among the latter, heart failure is most significantly associated with decreased HRV-CD. Decreased HRV-CD values, especially in diabetics, are also associated with lower survival.
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Affiliation(s)
- Dorit Almoznino-Sarafian
- The Department of Internal Medicine F, Assaf Harofeh Medical Center (affiliated to the Sackler School of Medicine, Tel-Aviv University), Zerifin, Israel.
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Castiglioni P, Parati G, Civijian A, Quintin L, Di Rienzo M. Local scale exponents of blood pressure and heart rate variability by detrended fluctuation analysis: effects of posture, exercise, and aging. IEEE Trans Biomed Eng 2009; 56:675-84. [PMID: 19389684 DOI: 10.1109/tbme.2008.2005949] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Heart rate self-affinity is often assessed by detrended fluctuations analysis, obtaining two coefficients only: a short-term (alpha(1)) exponent and a long-term (alpha(2)) exponent. Our aim is to show the limits of this approach and alternatively propose the estimation of the whole spectrum of local exponents alpha(n) for heart rate and blood pressure. To illustrate the advantages of this approach, we assess the effects of autonomic activations and age on alpha(n). We measured ECG and arterial pressure in 60 volunteers for 10 min, considering three conditions at increasing sympathetic activation: supine rest, sitting, and sitting during exercise. We computed alpha(n) of R-R intervals and systolic, mean, and diastolic blood pressures, as the slope of the detrended fluctuations function in a log-log plot. Volunteers were divided into age groups and compared. Results indicate that: 1) alpha(1) cannot be defined because short-term coefficients decrease with n, while alpha(2) cannot be defined only for blood pressure during supine rest; 2) heart rate and blood pressure scaling structures differ during supine rest but not during exercise; and 3) age effects appear mainly in supine rest, explaining discrepant results in literature. In conclusion, we recommend estimating the whole alpha(n) spectrum before possibly providing the "two-exponent" description only.
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Affiliation(s)
- Paolo Castiglioni
- Polo Tecnologico, S. Maria Nascente Research Hospital, Don Gnocchi Foundation, Milan 20148, Italy.
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Heart Rate Variability in Rats with Experimental Chronic Heart Failure and Long-Term Exposure to β-Adrenoblockers. Bull Exp Biol Med 2009; 147:181-4. [DOI: 10.1007/s10517-009-0466-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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38
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Bai X, Li J, Zhou L, Li X. Influence of the menstrual cycle on nonlinear properties of heart rate variability in young women. Am J Physiol Heart Circ Physiol 2009; 297:H765-74. [PMID: 19465541 DOI: 10.1152/ajpheart.01283.2008] [Citation(s) in RCA: 93] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
This study was designed to assess the changes in nonlinear properties of heart rate (HR) variability (HRV) during the menstrual cycle by means of complexity measures, including sample entropy (SampEn) and correlation dimension (CD), and explore probable physiological interpretations for them. In 16 healthy women (mean age: 23.8 +/- 2.7 yr), complexity measures along with the spectral components of HRV (sympathovagal markers) were analyzed over 1,500 R-R intervals recorded during both the follicular phase (day 11.9 +/- 1.4) and the luteal phase (day 22.0 +/- 1.4) of each woman's menstrual cycle. Simultaneously, serum ovarian hormone (estradiol-17 and progesterone) and thyroid-related hormone [free triiodothyronine, free thyroxine (T(4)), and thyroid-stimulating hormone] concentrations were measured. With regard to HRV measures, SampEn, CD, and high-frequency (HF) components decreased from the follicular phase to the luteal phase, whereas normalized low-frequency (LF) components and the LF-to-HF ratio as well as resting HR increased. In regard to hormone levels, whereas progesterone was increased, the other hormone concentrations were unchanged. Furthermore, across the menstrual cycle, both SampEn and CD were well correlated with the spectral indexes and free T(4) concentrations, and SampEn also showed significant correlations with the ratio of estradiol-17 to progesterone concentrations. These results suggest that the nonlinear properties in HRV are altered during the regular menstrual cycle and that the autonomic nervous system, ovarian hormone balance, and free T(4) may be involved in nonlinear HR control in healthy women. All of these factors may enrich the physiological meanings of complexity measures.
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Affiliation(s)
- Xiaopeng Bai
- Department of Cardiology, The Fourth Affiliated Hospital of Harbin Medical University, Harbin, Heilongjiang, China
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39
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Aubert AE, Vandeput S, Beckers F, Liu J, Verheyden B, Van Huffel S. Complexity of cardiovascular regulation in small animals. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2009; 367:1239-1250. [PMID: 19324706 DOI: 10.1098/rsta.2008.0276] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Oscillations of heart rate and blood pressure are related to the activity of the underlying control mechanism. They have been investigated mostly with linear methods in the time and frequency domains. Also, in recent years, many different nonlinear analysis methods have been applied for the evaluation of cardiovascular variability. This review presents the most commonly used nonlinear methods. Physiological understanding is obtained from various results from small animals.
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Affiliation(s)
- André E Aubert
- Laboratory Experimental Cardiology and Interdisciplinary Centre for Space Studies (ICSS), University Hospital Gasthuisberg, Katholieke Universiteit Leuven, Leuven 3000, Belgium.
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Javorka M, Turianikova Z, Tonhajzerova I, Javorka K, Baumert M. The effect of orthostasis on recurrence quantification analysis of heart rate and blood pressure dynamics. Physiol Meas 2008; 30:29-41. [PMID: 19039163 DOI: 10.1088/0967-3334/30/1/003] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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41
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De Vera L, Santana A, Gonzalez JJ. Nonlinearity and fractality in the variability of cardiac period in the lizard, Gallotia galloti: effects of autonomic blockade. Am J Physiol Regul Integr Comp Physiol 2008; 295:R1282-9. [DOI: 10.1152/ajpregu.90391.2008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Both nonlinear and fractal properties of beat-to-beat R-R interval variability signal (RRV) of freely moving lizards ( Gallotia galloti) were studied in baseline and under autonomic nervous system blockade. Nonlinear techniques allowed us to study the complexity, chaotic behavior, nonlinearity, stationarity, and regularity over time of RRV. Scaling behavior of RRV was studied by means of fractal techniques. The autonomic nervous system blockers used were atropine, propranolol, prazosin, and yohimbine. The nature of RRV was linear in baseline and under β-, α1- and α2-adrenoceptor blockades. Atropine changed the linear nature of RRV to nonlinear and increased its stationarity, regularity and fractality. Propranolol increased the complexity and chaotic behavior, and decreased the stationarity, regularity, and fractality of RRV. Both prazosin and yohimbine did not change any of the nonlinear and fractal properties of RRV. It is suggested that 1) the use of both nonlinear and fractal analysis is an appropriate approach for studying cardiac period variability in reptiles; 2) the cholinergic activity, which seems to make the α1-, α2- and β-adrenergic activity interaction unnecessary, determines the linear behavior in basal RRV; 3) fractality, as well as both RRV regularity and stationarity over time, may result from the balance between cholinergic and β-adrenergic activities opposing actions; 4) β-adrenergic activity may buffer both the complexity and chaotic behavior of RRV, and 5) neither the α1- nor the α2-adrenergic activity seem to be involved in the mediation of either nonlinear or fractal components of RRV.
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Zhang LF, Cheng JH, Liu X, Wang S, Liu Y, Lu HB, Ma J. Cardiovascular changes of conscious rats after simulated microgravity with and without daily −Gx gravitation. J Appl Physiol (1985) 2008; 105:1134-45. [DOI: 10.1152/japplphysiol.00184.2008] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
This study was designed to test the hypothesis that postsuspension cardiovascular manifestation in conscious rats after a medium-term (28-day) tail suspension (SUS) is hypertensive and tachycardiac and can be prevented by a countermeasure of daily 1-h dorsoventral (−G x) gravitation provided by standing (STD). To assess associated changes in cardiovascular regulation, blood pressure (BP) and heart rate (HR) variability were analyzed by spectral analysis computed by parametric autoregressive (AR) method and by nonlinear recurrence quantification analysis (RQA) and approximate entropy (ApEn) measure. The results showed that conscious SUS rats manifested hypertensive and tachycardiac response before and after being released from suspension compared with the controls, and the countermeasure of 1 h/day −G x prevented the hypertensive response. Auto- and cross-spectral analysis and transfer function analysis did not show significant changes in cardiovascular variability. However, SUS decreased the three RQA indexes [recurrence percentage (RC%), determinism percentage (DT%), and the longest diagonal line ( Lmax)] of systolic BP, whereas STD alleviated these changes. ApEn values of HR data sets were significantly higher in the SUS and SUS + STD groups compared with those of the control group before and after release from suspension. The present study has demonstrated that daily −G x for as short as 1 h is sufficient to prevent postsuspension cardiovascular alteration in conscious rats after a medium-term SUS. Nonlinear measures, but not spectral analysis, might provide promising data to estimate the overall changes in cardiovascular autonomic regulation due to microgravity exposure.
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Gonçalves H, Henriques-Coelho T, Bernardes J, Rocha AP, Nogueira A, Leite-Moreira A. Linear and nonlinear heart-rate analysis in a rat model of acute anoxia. Physiol Meas 2008; 29:1133-43. [DOI: 10.1088/0967-3334/29/9/010] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Li D, Chiang AY, Clawson CA, Main BW, Leishman DJ. Heartbeat dynamics in adrenergic blocker treated conscious beagle dogs. J Pharmacol Toxicol Methods 2008; 58:118-28. [DOI: 10.1016/j.vascn.2008.05.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2008] [Accepted: 05/02/2008] [Indexed: 10/22/2022]
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Hu K, Scheer FAJL, Buijs RM, Shea SA. The endogenous circadian pacemaker imparts a scale-invariant pattern of heart rate fluctuations across time scales spanning minutes to 24 hours. J Biol Rhythms 2008; 23:265-73. [PMID: 18487418 DOI: 10.1177/0748730408316166] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Heartbeat fluctuations in mammals display a robust temporal structure characterized by scale-invariant/fractal patterns. These scale-invariant patterns likely confer physiological advantage because they change with cardiovascular disease and these changes are associated with reduced survival. Models of physical systems imply that to produce scale-invariant patterns, factors influencing the system at different time scales must be coupled via a network of feedback interactions. A similar cardiac control network is hypothesized to be responsible for the scale-invariant pattern in heartbeat dynamics, although the essential network components have not been determined. Here is shown that scale-invariant cardiac control occurs across time scales from minutes to approximately 24 h, and that lesioning the mammalian circadian pacemaker (suprachiasmatic nucleus; SCN) completely abolishes the scale-invariant pattern at time scales>or approximately 4 h. At time scales<or approximately 4 h, the scale invariance persisted following SCN lesion but with a different pattern. These results indicate previously unrecognized multiscale influences of the SCN on heart rate fluctuations that cannot be explained by a simple pacemaker of 24-h rhythmicity. The conclusion is that the SCN serves as a major node in the cardiac control network and imparts scale-invariant cardiac control across a wide range of time scales with strongest effects between approximately 4 and 24 h. These results demonstrate that experimental manipulations (e.g., SCN lesion) can be used to begin to model and understand the origin of scale-invariant behavior in a neurophysiological system.
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Affiliation(s)
- Kun Hu
- Division of Sleep Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02215, USA.
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Sal'nikov EV, Fateev MM, Sidorov AV, Fedorov VN, Grigor'eva MV. Effect of beta-adrenoblockers on heart rate variability in awake and narcotized rats. Bull Exp Biol Med 2008; 144:494-7. [PMID: 18642695 DOI: 10.1007/s10517-007-0359-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
In narcotized rats, beta-adrenoceptor blockers changed all parameters of heart rate variability indicating up-regulation of parasympathetic activity and down-regulation of the sympathetic one. In immobilized awake rats, the temporal and geometrical parameters varied similarly, while spectral analysis indicated possible activation of other neurohumoral mechanisms against the background of beta-blocker treatment.
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Affiliation(s)
- E V Sal'nikov
- Department of Biology, Yaroslavl State Medical Academy
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Trunkvalterova Z, Javorka M, Tonhajzerova I, Javorkova J, Lazarova Z, Javorka K, Baumert M. Reduced short-term complexity of heart rate and blood pressure dynamics in patients with diabetes mellitus type 1: multiscale entropy analysis. Physiol Meas 2008; 29:817-28. [DOI: 10.1088/0967-3334/29/7/010] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Hu K, Scheer FAJL, Buijs RM, Shea SA. The circadian pacemaker generates similar circadian rhythms in the fractal structure of heart rate in humans and rats. Cardiovasc Res 2008; 80:62-8. [PMID: 18539630 DOI: 10.1093/cvr/cvn150] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
AIMS Adverse cardiovascular events in humans occur with a day/night pattern, presumably related to a daily pattern of behaviours or endogenous circadian rhythms in cardiovascular variables. Healthy humans possess a scale-invariant/fractal structure in heartbeat fluctuations that exhibits an endogenous circadian rhythm and changes towards the structure observed in cardiovascular disease at the circadian phase corresponding to the time of the broad peak of adverse cardiovascular events (at about 10 AM). To explore the relationship between the rest/activity cycle, endogenous circadian rhythmicity, and cardiac vulnerability, we tested whether the fractal structure of heart rate exhibits a similar circadian rhythm in a mammalian species that is nocturnally active (Wistar rats) compared with diurnally active humans, and how this fractal structure changes after lesioning the circadian pacemaker (suprachiasmatic nucleus, SCN) in rats. METHODS AND RESULTS Analysis of heart rate data collected over 10 days in eight intact and six SCN-lesioned Wistar rats during constant darkness revealed that: (i) as with humans, rats exhibit an endogenous circadian rhythm in the scaling exponent characterizing the hourly fractal structure of heart rate (P = 0.0005) with larger exponents during the biological day (inactive phase for rats; active phase for humans); (ii) SCN lesioning abolished the rhythm in the fractal structure of heart rate and systematically increased the scaling exponent (P = 0.01). CONCLUSION Rats possess a circadian rhythm of fractal structure of heart rate with a similar temporal pattern as previously observed in humans despite opposite rest/activity cycles between the two species. The SCN imparts this endogenous rhythm. Moreover, lesioning the SCN in rats results in a larger scaling exponent, as occurs with cardiovascular disease in humans.
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Affiliation(s)
- Kun Hu
- Division of Sleep Medicine, Brigham and Women's Hospital, Harvard Medical School, 221 Longwood Avenue, Boston, MA 02115, USA.
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Javorka M, Trunkvalterova Z, Tonhajzerova I, Javorkova J, Javorka K, Baumert M. Short-term heart rate complexity is reduced in patients with type 1 diabetes mellitus. Clin Neurophysiol 2008; 119:1071-81. [PMID: 18308624 DOI: 10.1016/j.clinph.2007.12.017] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2007] [Revised: 12/04/2007] [Accepted: 12/23/2007] [Indexed: 11/19/2022]
Abstract
OBJECTIVE The aim of this study was to test whether new heart rate variability (HRV) complexity measures provide diagnostic information regarding early subclinical autonomic dysfunction in diabetes mellitus (DM). METHODS HRV in DM type 1 patients (n=17, 10f, 7m) aged 12.9-31.5 years (duration of DM 12.4+/-1.2 years) was compared to a control group of 17 healthy matched probands. The length of R-R intervals was measured over 1h using a telemetric ECG system. In addition to linear measures, we assessed HRV complexity measures, including multiscale entropy (MSE), compression entropy and various symbolic dynamic measures (Shannon and Renyi entropies, normalized complexity index (NCI), and pattern classification). RESULTS HRV magnitude was significantly reduced in patients with DM. Several HRV complexity parameters (MSE at scales 2-4, Renyi entropy, NCI) were also significantly reduced in diabetics. MSE indices and compression entropy did not correlate with linear measures. CONCLUSIONS The magnitude and complexity of HRV are reduced in young patients with DM, indicating vagal dysfunction. SIGNIFICANCE The quantification of HRV complexity in combination with its magnitude may provide an improved diagnostic tool for cardiovascular autonomic neuropathy in DM.
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Affiliation(s)
- Michal Javorka
- Institute of Physiology, Jessenius Faculty of Medicine, Comenius University, Martin, Slovakia
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Hypnotizability-dependent modulation of the changes in heart rate control induced by upright stance. Brain Res Bull 2008; 75:692-7. [DOI: 10.1016/j.brainresbull.2007.11.012] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2007] [Revised: 08/22/2007] [Accepted: 11/21/2007] [Indexed: 10/22/2022]
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