HRV in isolated rabbit hearts and in vivo rabbit hearts

Frontiers in Physiology

BackgroundThe interactions between the autonomic nervous system (ANS), intrinsic systems (e.g., endocrine), and internal pacemaker mechanisms govern short (milliseconds–seconds)- and long (seconds–minutes)-range heart rate variability (HRV). However, there is a debate regarding the identity of the mechanism underlying HRV on each time scale. We aim to design a general method that accurately differentiates between the relative contribution of the ANS and pacemaker mechanisms to HRV in various mammals, without the need for drug perturbations or organ isolation. Additionally, we aim to explore the universality of the relative contribution of the ANS and pacemaker system of different mammals.MethodsThis work explored short- and long-range HRVs using published ECG data from dogs, rabbits, and mice. To isolate the effects of ANS on HRV, ECG segments recorded before and after ANS-blockade were compared.ResultsDifferentiation of the ANS from extrinsic and intrinsic pacemaker mechanisms was ...

Computing in Cardiology Conference (CinC)

Aim: High frequency content of QRS complex (HF-QRS) is thought to be related to local conduction velocity (CV). There also exists the evidence suggesting the coupling between CV and mechanical stretch via socalled mechano-electric feedback. The aim of this study was to investigate possible relationship between left ventricular (LV) load and the most common HF-QRS parameters. Methods: Six isolated rabbit hearts in working mode underwent an experimental protocol consisting of upward and downward steps in preload (8-11 cmH 2 O). Eight unipolar pseudo-ECGs, left atrial pressure, and flow rate were recorded at f s =10 kHz and 16-bit resolution. QRS complexes from hemodynamically stable experiment phase were clustered, aligned, and decomposed into 3 HF-QRS bands followed by the assessment of power envelope RMS, the tallest peak value and its position. Results: No statistically significant changes associated with LV load alteration were observed in HF-QRS parameter. Conclusion: No evidence of load dependent changes in conduction velocity was found in the study. However, HF signal may represent a complex spatial depolarization behavior. Low sensitivity of used metrics should also be taken into consideration.

Computing in Cardiology (CinC), 2012, 2018

Introduction: Heart rate variability (HRV) analysis tools have been mainly available for analysis of human electrocardiographic derived heart rate. We explore extending HRV analysis to two additional dimensions: (1) analysis across multiple mammalian species and (2) analysis across different levels of integration for example sinoatrial tissue. Methods: We analyzed the beating rate variability (BRV) across the two additional dimensions using the PhysioZoo computer program that we recently introduced. We used published databases of electrocardiograms from four mammal types: human (n=18), dog (n=17), rabbit (n=4) and mouse (n=8). We computed the BRV measures for each. We also show how the PhysioZoo program can be used for the analysis of sinoatrial node tissue BRV. Results: The study of typical mammalian heart and respiration rates (obtained from the dominant high frequency peak) revealed a linear relationship between these two quantities. Analysis of the rabbit sinoatrial node tissue BRV showed that it had reduced overall variability when compared to in vivo heart BRV.

Factor structure of heart rate periodogram has been detected with factor analysis. The results showed that there are at least four periodical phenomena of HRV. Two of them have not been discovered and physiologically explained yet. Their frequency ranges are 0.21 to 0.31 1/beat with the peak at 0.26 1/beat and 0.25 to 0.5 1/beat with the peak 0.35 1/beat. Despite of differences of the peak frequencies the frequency rages of the factors are overlapped. Therefore, power of spectral density within any frequency range could not be a measure of a modulating physiological mechanism activity.

2009

Among the techniques used in its evaluation, the heart rate variability (HRV) has arising as a simple and non-invasive measure of the autonomic impulses, representing one of the most promising quantitative markers of the autonomic balance. The HRV describes the oscillations in the interval between consecutive heart beats (RR interval), as well as the oscillations between consecutive instantaneous heart rates. It is a measure that can be used to assess the ANS modulation under physiological conditions, such as wakefulness and sleep conditions, different body positions, physical training and also pathological conditions. Changes in the HRV patterns provide a sensible and advanced indicator of health involvements. Higher HRV is a signal of good adaptation and characterizes a health person with efficient autonomic mechanisms, while lower HRV is frequently an indicator of abnormal and insufficient adaptation of the ANS, provoking poor patient's physiological function. Because of its importance as a marker that reflects the autonomic nervous system activity on the sinus node and as a clinical instrument to assess and identify health involvements, this study reviews conceptual aspects of the HRV, measurement devices, filtering methods, indexes used in the HRV analyses, limitations in the use and clinical applications of the HRV.

PHYSIOLOGY & BEHAVIOR, 2004

Autonomic regulation of cardiac activity during stress has not been clearly defined in farm animals. In part, this is due to the limited availability of affordable ambulatory cardiac monitors capable of accurately monitoring and storing large amounts of data that meet the criteria necessary for heart rate variability analysis. Our objectives were to measure the accuracy of a 24-h Polar RR monitor using gold standard ECG, to examine and categorise any occurring anomalies and to ascertain their impact on the outcome of heart rate variability analysis. Five 1-year-old female pigs (gilts) were socially isolated from their pen mates and cardiac activity was simultaneously measured using two systems, a 24-h Polar RR Recorder and a Telemetric ECG system. The Polar data were manually assessed both against and in isolation of the ECG data to identify anomalous beats, which were then assigned to one of five identified error categories. The anomalies in the Polar data were corrected and statistical comparisons were performed among the three data sets to evaluate the effects of anomalies on heart rate variability analysis. Bland -Altman analysis was used to measure the level of agreement among the ECG, Uncorrected Polar and Corrected Polar data. No anomalies or ectopies were found in the ECG data but 46 anomalies (0.81% of total interbeat intervals [IBI]) were found in the Polar Uncorrected data. Manual identification and editing procedures reduced this error to 0.018%. Most mean heart rate and IBI parameters were unaffected by error ( P>.05). Standard deviation (S.D.) and root mean square of successive differences (RMSSD) were 45% and 50% higher when anomalies were present in the data. Artefacts affected the magnitude of the frequency domain indices and overestimated total and parasympathetic activity and underestimated sympathetic activity. The mean difference between ECG and Uncorrected Polar data was 1.36 ms (limits of agreement À 69.03 to 71.74 ms). This was greatly improved to 0.36 ms (limits of agreement À 5.37 to 6.10 ms) after editing. Overall, even a small proportion of error biased the outcome of heart rate variability analysis. This bias was greatly reduced by correcting the anomalous beats. Bland -Altman analysis demonstrated that when there was error present in the Polar data, it could not be used interchangeably with the ECG data. However, if there were no anomalies present in the data or if they were classified and corrected using the approach in this study, then the two systems could be used interchangeably. D

Artificial Organs, 1993

In order to analyze the origin of the rhythmical fluctuations in the cardiovascular system, an artificial heart, which does not have rhythmical periodicities such as altering heart rate and cardiac function, was utilized in chronic animal experiments with adult goats. Two pneumatically actuated ventricular assist devices were implanted as a total biventricular bypass under general anesthesia, and then the natural heart was electrically fibrillated to constitute the biventricular bypass type of complete prosthetic circulation model. All hemodynamic data were recorded under awake conditions and were calculated in the computer system by spectral analysis methods. In the power spectrum of the arterial blood pressure of the animal with the artificial heart, the Mayer wave peak and respiratory wave peak were clearly observed, and spectral analysis including the coherence function suggests that the Mayer waves originated from the peripheral vascular resistance and the respiratory waves probably originated from the periodicities of the pulmonary circulation. These fluctuations in the circulatory system influenced the arterial baroreflex system and transfer to the sympathetic outflow through the central baroreflex system, which suggests that rhythmical fluctuations in hemodynamic parameters originate at least in part from these vascular periodicities.

Frontiers in Psychology, 2014

Heart rate variability (HRV), the change in the time intervals between adjacent heartbeats, is an emergent property of interdependent regulatory systems that operate on different time scales to adapt to challenges and achieve optimal performance. This article briefly reviews neural regulation of the heart, and its basic anatomy, the cardiac cycle, and the sinoatrial and atrioventricular pacemakers. The cardiovascular regulation center in the medulla integrates sensory information and input from higher brain centers, and afferent cardiovascular system inputs to adjust heart rate and blood pressure via sympathetic and parasympathetic efferent pathways. This article reviews sympathetic and parasympathetic influences on the heart, and examines the interpretation of HRV and the association between reduced HRV, risk of disease and mortality, and the loss of regulatory capacity. This article also discusses the intrinsic cardiac nervous system and the heart-brain connection, through which afferent information can influence activity in the subcortical and frontocortical areas, and motor cortex. It also considers new perspectives on the putative underlying physiological mechanisms and properties of the ultra-low-frequency (ULF), very-low-frequency (VLF), low-frequency (LF), and high-frequency (HF) bands. Additionally, it reviews the most common time and frequency domain measurements as well as standardized data collection protocols. In its final section, this article integrates Porges' polyvagal theory, Thayer and colleagues' neurovisceral integration model, Lehrer et al.'s resonance frequency model, and the Institute of HeartMath's coherence model. The authors conclude that a coherent heart is not a metronome because its rhythms are characterized by both complexity and stability over longer time scales. Future research should expand understanding of how the heart and its intrinsic nervous system influence the brain.

Circulation, 2002

The combined effects of excitability and action potential duration (APD) restitution on wavefront dynamics remain unclear. We used optical mapping techniques to study Langendorff-perfused rabbit hearts. In protocol IA (n=10), D600 at increasing concentrations was infused during ventricular fibrillation (VF). With concentration increased to 0.5 mg/L, fast VF (dominant frequency, 19.1+/-1.8 Hz) was consistently converted to ventricular tachycardia (VT). However, increasing D600 further to 2.5 or 5.0 mg/L converted VT to slow VF (11.9+/-2.3 Hz, P=0.0011). In an additional 4 hearts (protocol IB), tetrodotoxin converted a preexisting VT to slow VF (11.0+/-1.4 Hz). Optical maps show wandering wavelets in fast VF, organized reentry in VT, and spatiotemporal periodicity in slow VF. In protocol II, we determined APD and conduction time(-1) (CT(-1)) restitutions during D600 infusion. CT(-1) was used as an estimate of excitability. At 0.1 mg/L, APD and CT(-1) restitutions were steep and flat, ...

2012

The aim of the present contribution is to give a review on a new methodology that we may use when we are employed in the analyis of one of the most fundamental signals that we encounter in electrophysiology, the R-R intervals in analysis of the ECG. First of all the limits of the current FFT application are discussed. Soon after the basic foundations of the CZF method are exposed and we expose and discuss in detail a large number of physiological and clinical applications, based directly on experimental results .The results evidence the importance to use the CZF method as non invasive marker in analysis of HRV.

INDIAN JOURNAL OF PHYSIOLOGY AND ALLIED SCIENCES

Objective: A sustainable animal model is needed to detect Cardiovascular autonomic dysfunctions, which can be assessed by recording electrocardiogram and analysis of heart rate variability (HRV). Therefore, the present study tried to find out the duration for HRV analysis for reliable results.Material and methods: Recording of Electroencephalogram (ECG) is reported in many articles. However, there is no information regarding the duration of ECG to be considered for the HRV analysis. Adult Wistar rat were used for a recording of ECG and HRV analysis. A combination of Ketamine 50 mg/kg and Xylazine 10 mg/kg was used for anesthésia in all the recordings. We analyzed the HRV parameters for all the records with 10 different durations starting from 1 minute to 10 minutes and compared.Results and Discussion: It was observed that, ECG parameters were within normal range while the data from HRV analysis from different duration showed wide discrepancies depending on the duration of ECG record...

Clinical Cardiology, 1990

Journal of Integrative Cardiology

The heart rate variability (HRV), which can provide information about the balance between the sympathetic and the parasympathetic system, is accepted as an indicator of autonomic tone, which is effective on the heart. Neural remodeling developing in hearts that are affected by various diseases leads to imbalance in the autonomic activity. These changes that may occur in the autonomic nervous system may lead to ventricular arrhythmia and sudden cardiac death through negatively affecting the cardiac rhythm. HRV has been evaluated in many cardiac, neurological and rheumatological diseases in recent years and has come into the foreground as an important marker of mortality. In this review, we aimed to introduce the parameters used in HRV measurements and analyze the conditions that could influence these measurements (maneuver, diseases or drugs, etc).

This insightful and comprehensive monograph provides fundamental and detailed summaries of HeartMath Institute’s many years of innovative research. It presents brief overviews of heart rate variability, resilience, coherence, heart-brain interactions, intuition and the scientific discoveries that shaped techniques developed to increase personal and social fulfillment and effectiveness. Included are summary reports of research conducted in the business, education, health and first responder fields. Both the layperson and science professional will appreciate its simplicity and thoroughness.