Heart Rate In Healthy Subjects Research Articles

Validation and Reliability of a Novel Vagus Nerve Neurodynamic Test and Its Effects on Heart Rate in Healthy Subjects: Little Differences Between Sexes.

BackgroundThe vagus nerve (VN), also called the pneumogastric nerve, connects the brainstem to organs contained in the chest and abdomen. Physiologically, VN stimulation can rapidly affect cardiac activity and heart rate (HR). VN neuropathy can increase the risk of arrhythmias and sudden death. Therefore, a selective test of VN function may be very useful. Since peripheral neurodynamic tests (NDT) are reliable for the assessment of neuropathies in somatic nerves, we aimed to validate a novel NDT to assess VN activity, namely, the VN-NTD.MethodsIn this cross-sectional double-blind, sex-balanced study, 30 participants (15 females) completed a checklist of autonomic dysfunction symptoms. During the VN-NDT administration, HR and symptoms (i.e., mechanical allodynia) were monitored in parallel to a real-time ultrasonography imaging (USI) and motion capture analysis of the neck. The VN-NDT impact on HR and its accuracy for autonomic symptoms reported in the last 7 days were tested.ResultsThe VN-NDT induced a significant HR reduction of about 12 and 8 bpm in males and females [t(1, 119) = 2.425; p < 0.017; ηp2 = 0.047, 95% confidence interval (CI): 0.93–9.18], respectively. No adverse events were observed during VN-NDT. A substantial interexaminer agreement between the evaluators in symptoms induction by VN-NDT was detected [F(1, 119) = 0.540; p = 0.464; ηp2 = 0.005, low effect]. Notably, mechanical allodynia accuracy for gastrointestinal dysfunctions was excellent (p < 0.05; 95% CI: 0.52–0.73; p < 0.001; 95% CI: 0.81–0.96).ConclusionsThe novel VN-NDT is a valid and accurate test capable of detecting VN activation with high sensitivity. Data provided are suitable for both sexes as a hallmark of HR variation due to VN normal response. The proposed VN-NDT may be reliable as daily routine neurological examination tests for the evaluation of neuropathic signs related to neuroinflammation of the VN.Clinical Trial Registrationwww.ClinicalTrials.gov, identifier NCT04192877.

Differential Network Analysis Reveals Molecular Determinants Associated with Blood Pressure and Heart Rate in Healthy Subjects.

There is mounting evidence that subclinical nonpathological high blood pressure and heart rate during youth and adulthood steadily increase the risk of developing a cardiovascular disease at a later stage. For this reason, it is important to understand the mechanisms underlying the subclinical elevation of blood pressure and heart rate in healthy, relatively young individuals. In the present study, we present a network-based metabolomic study of blood plasma metabolites and lipids measured using nuclear magnetic resonance spectroscopy on 841 adult healthy blood donor volunteers, which were stratified for subclinical low and high blood pressure (systolic and diastolic) and heart rate. Our results indicate a rewiring of metabolic pathways active in high and low groups, indicating that the subjects with subclinical high blood pressure and heart rate could present latent cardiometabolic dysregulations.

Inspiratory- and expiratory-gated transcutaneous vagus nerve stimulation have different effects on heart rate in healthy subjects: preliminary results

PurposeTranscutaneous auricular vagus nerve stimulation (taVNS) has been considered for the treatment of sympathetically mediated disorders. However, the optimal mode of stimulation is unknown. This study aimed to compare the cardiovascular effects of respiratory-gated taVNS in healthy subjects.MethodsThe examination included expiratory-gated, inspiratory-gated, and non-respiratory-gated taVNS trials. Subjects were examined twice (the order of expiratory- and inspiratory-gated taVNS was changed). taVNS trials started with controlled breathing without stimulation (pre-stimulatory recording) followed by controlled breathing with taVNS (stimulatory recording). Synchronizing taVNS with the respiratory phase was computer-controlled. Heart rate (HR) was calculated from ECG. Systolic blood pressure (SBP) and systemic vascular resistance (SVR) were recorded continuously and noninvasively. Baroreflex sensitivity based on rising (BRS-UP) or falling SBP sequences (BRS-DOWN) or all sequences (BRS-ALL) and heart rate variability (HRV) were analyzed.ResultsSeventy-two taVNS trials were obtained from 12 subjects (age 23 ± 3 years). Pre-stimulatory HR correlated with change in HR (r = − 0.25) and SVR (r = 0.24, both p < 0.05). There were no differences between three stimulatory conditions in (1) the changes of hemodynamic parameters, (2) BRS-UP and BRS-ALL, or (3) HRV indices (all p > 0.20). However, in the group of high pre-stimulatory HR trials, HR change differed between inspiratory-gated (0.11 ± 0.53%) and both expiratory-gated (− 1.30 ± 0.58%, p = 0.06) and non-respiratory-gated taVNS (− 1.69 ± 0.65, p = 0.02). BRS-DOWN was higher in inspiratory- vs. non-respiratory-gated taVNS (15.4 ± 1.3 vs. 14.1 ± 0.9 ms/mmHg, p = 0.03).ConclusionsExpiratory-gated and non-respiratory-gated taVNS exert clear cardioinhibitory effects in healthy subjects with high pre-stimulatory HR, whereas inspiratory-gated taVNS does not affect HR. Cardiac and vascular effects of taVNS depend on pre-stimulatory HR.

Cortisol Levels and Autonomic Control of Heart Rate in Healthy Subjects

Abstract Introduction: There is an increase in level of stress in the general population because of the social, personal and professional demands. Currently, there are only simple tools that can safely measure this stress such as levels of cortisol and heart rate variability (HRV). Objective: To analyze the relationship between salivary cortisol and the cardiac autonomic modulation. Methods: A total of fifty-one male and female subjects between 18 and 40 years old were evaluated. Saliva collection was achieved for the salivary cortisol dosage. The collection was performed through the SalivetteR tube. After this collection, the median cortisol levels (0.24 ug/dl) were analyzed and the volunteers were divided into two groups: i) cortisol below the mediane ii) cortisol above the median. After this division, each group consisted of 25 volunteers and then was verified the following information: age, gender, weight, height, body mass index (BMI), blood pressure. Shortly thereafter was assessment of cardiac autonomic modulation por meio da HRV. The Polar RS800cx heart rate receiver was placed on the chest of the volunteers, in the vicinity of the distal third of the sternum. The volunteers were instructed to remain in rest with spontaneous breathing in dorsal position for 20 minutes. HRV analysis included geometric, time and frequency domain indices. Results: There were no statistical differences for the two groups regarding systolic and diastolic blood pressure, heart rate, RR intervals or linear and frequency indices for the volunteers. In addition, also there was no correlation the cortisol with the analyzed variables (SAP, p=0.460; DAP, p = 0.270; HR, p = 0.360; RR, p = 0.380; SDNN, p = 0.510; rMSSD, p = 0.660; pNN50, p = 0.820; RRtri, p = 0.170; TINN, p = 0.470; SD1, p = 0.650; SD2, p = 0.500; LF [ms2], p = 0.880; LF [nu], p = 0.970; HF [ms2], p = 0.870; HF [nu], p = 0.960; LF/HF, p = 0.380 Conclusion: Heart rate variability autonomic control was unchanged in healthy subjects with physiological distribution of salivary cortisol levels. There was no association between normal salivary cortisol and resting autonomic regulation of heart rate.

Sign and magnitude scaling properties of heart rate variability in patients with end-stage renal failure: Are these properties useful to identify pathophysiological adaptations?

The scaling properties of heart rate variability data are reliable dynamical features to predict mortality and for the assessment of cardiovascular risk. The aim of this manuscript was to determine if the scaling properties, as provided by the sign and magnitude analysis, can be used to differentiate between pathological changes and those adaptations basically introduced by modifications of the mean heart rate in distinct manoeuvres (active standing or hemodialysis treatment, HD), as well as clinical conditions (end stage renal disease, ESRD). We found that in response to active standing, the short-term scaling index (α1) increased in healthy subjects and in ESRD patients only after HD. The sign short-term scaling exponent (α1sign) increased in healthy subjects and ESRD patients, showing a less anticorrelated behavior in active standing. Both α1 and α1sign did show covariance with the mean heart rate in healthy subjects, while in ESRD patients, this covariance was observed only after HD. A reliable estimation of the magnitude short-term scaling exponent (α1magn) required the analysis of time series with a large number of samples (>3000 data points). This exponent was similar for both groups and conditions and did not show covariance with the mean heart rate. A surrogate analysis confirmed the presence of multifractal properties (α1magn > 0.5) in the time series of healthy subjects and ESDR patients. In conclusion, α1 and α1sign provided insights into the physiological adaptations during active standing, which revealed a transitory impairment before HD in ESRD patients. The presence of multifractal properties indicated that a reduced short-term variability does not necessarily imply a declined regulatory complexity in these patients.

Effect of hypovolemia on efficacy of reflex maintenance of blood pressure on orthostatic challenge.

Blood volume is an important determinant of the efficacy of the negative feedback mechanisms that maintain blood pressure. However, its effect on time profile and magnitude of the responses remain unstudied. To study the effect of mild hypovolemia on time profiles and magnitude of changes in blood pressure and heart rate in healthy subjects before and after blood donation. Fifty six healthy volunteer donors who signed up for blood donation were recruited (age 35 ± 7 years; weight 75 ± 9 Kg). Baseline beat to beat blood pressure and Lead II ECG was recorded for 5 min followed by orthostatic challenge for 3 min before and after blood donation. The donation of 450 ml of blood did not lead to any changes in the resting systolic, diastolic or mean blood pressure. However, there was a significant decrease in pulse pressure after blood donation along with an increase in the heart rate. During orthostatic challenge, after blood donation there was a greater fall in systolic, diastolic, mean and pulse pressure along with a greater increase in heart rate as compared to before the blood donation. The latency to response and the total time to recovery of blood pressure and heart rate increased significantly after blood donation. Maintenance of blood pressure after orthostatic challenge is not compromised after mild hypovolemia produced by donation of 450 ml of blood. However, mild hypovolemia results in increase in latency of response and is accompanied with larger magnitude of fall in blood pressure during orthostatic challenge.

Wavelet Leader Multifractal Analysis for Heart Rate Variability

Heart Rate Variability Analysis. Analyzing and characterizing Heart Rate Variability (HRV) constitutes a significant public health stake — both for understanding mechanisms regulating heart rate in healthy subjects and for detection and classification of pathologies — that received, and continues to arouse, significant research efforts. After the seminal work in [1], spectral analysis has been massively used to investigate HRV time dynamics. Essentially, it relies on splitting the spectrum into frequency bands and on measuring the respective amounts of energy within each band. To go beyond spectrum analysis, that assumes stationarity and focuses on the sole 2nd order statistical order (the correlation function), numerous efforts were devoted to non stationary, non Gaussian and non linear analyses of HRV, using tools such as time-frequency/scale representations, chaos, entropy, complexity,. . . (cf. e.g., [2], [3], [4], [5]). Scale Invariance and Multifractal analysis. An important finding in HRV analysis consists of the observation that, at low frequencies, i.e., essentially for f ≤ 0.1 Hz, HRV time dynamics show no preferred scales: No frequency plays a specific role. It has aroused the use of concepts such as scale invariance, scaling, self-similarity or (multi-)fractal to describe HRV fluctuations. Scale invariance is reconciling the spectrum and time variability analysis perspectives (a healthy subject must show a variability at a chosen scale a, Va(t) = supu,v∈[t−a/2,t+a/2](|X(u)−X(v)|) larger than a chosen threshold) and extends them in three key respects: First, the quantity used to analyze HRV needs to be restricted neither the oscillation |X(u)−X(v)|, nor to the spectrum, but can be any multiscale quantity TX(a, t) depending jointly on the time position t and on the analysis scale a, the modulus of wavelet coefficients being natural candidates; Second, interest is no longer in the values taken by variability Va(t) at a given time, or by Spectrum at a given frequency, but instead in the power law shaped dependence of these values with respect to the analysis scale a or frequency f ; Third, analysis is not restricted to first or second order statistics of data only but aims at probing their whole statistical properties. In a multiscale (wavelet) framework, these three extensions are efficiently summarized as ∑ t T q X(a, t) ≃ a, across a large range of scales am ≤ a ≤ aM , aM/am ≫ 1 and for a range of statistical orders q. The scaling exponents ζ(q) are used for HRV characterization or pathology detection. Because the ζ(q) can be theoretically related to the fluctuations along time of the local (Holder) regularity of sample path and to the multifractal spectrum of data, this power-law

Multifractal properties of ECG patterns of patients suffering from congestive heartfailure

The multifractal properties of two-channel ECG patterns of patients suffering from severecongestive heart failure (New York Heart Association (NYHA) classes III–IV) are studiedand are compared with those for normal healthy people using the multifractal detrendedfluctuation analysis methodology. Ivanov et al (1999 Nature 399 461) have studied themultifractality of human heart rate dynamics using the wavelet transformation modulusmaxima (WTMM) methodology. But it has been observed by several scientiststhat multifractal detrended fluctuation analysis (MFDFA) works better than theWTMM method in the detection of monofractal and multifractal characteristicsof the data. Galaska et al (2008 Ann. Noninvasive Electrocardiol. 13 155) haveobserved that MFDFA is more sensitive compared to the WTMM method inthe differentiation between multifractal properties of the heart rate in healthysubjects and patients with left ventricular systolic dysfunction. In the presentwork the variation of two parameters of the multifractal spectrum—its widthW (related to the degree of multifractality) and the value of the Hölder exponentα0—for the healthy and congestive heart failure patients is studied.α0 is a measure of the degree of correlation. The degree of multifractality varies appreciably(85–90% C.L.) for the normal and the CHF sets for channel I. For channel II nosignificant change in the values is observed. The degree of correlation is found to becomparatively high for the normal healthy people compared to those suffering fromCHF.

Characterizing atypical patterns of Heart Rate before Paroxysmal Ventricular Tachycardia

Results of a comparative analysis between Heart Rate (HR) patterns occurring before the onset of Paroxysmal Ventricular Tachycardia (PVT) and from healthy subjects are shown. Two study groups were made after electrocardiographic dynamical monitoring (Holter) of volunteers. The first group includes 100 h from 27 healthy control subjects, and the second group consists of 88 h, ending with self-terminating episodes of PVT from 55 patients. Patterns are defined as sequences of consecutive RR intervals, while atypical patterns are defined as corresponding to unlikely behavior of Heart Rate in healthy subjects. We investigated spatial and temporal distributions of these patterns in order to find early signs of PVT. We found that they can be grouped on a reduced number of clusters, and the number of atypical patterns increases as we approach the onset of the episode.

Elevated Heart Rate in Cardiovascular Diseases: A Target for Treatment?

Heart rate is a major determinant of myocardial oxygen consumption and of cardiac work, and thus reduction of heart rate may represent an important strategy for the treatment of patients with a wide range of cardiac disorders. In addition, several experimental lines of research point to high heart rate as an important risk factor for atherosclerosis and, thus, pharmacologic heart rate reduction could prevent or retard the development of atherosclerotic plaques and increase survival. Today, in patients with acute or chronic coronary syndromes or with congestive heart failure, reducing heart rate is a generally accepted treatment modality. Up to now, no human study has been performed to demonstrate the efficacy and the risk-benefit ratio of cardiac slowing in patients without cardiac disorders. However, recent retrospective analyses of the INternational VErapamil-SR/trandolapril STudy and the Paris Prospective Study 1 provided promising results. Treatment of high heart rate in healthy subjects appears to be premature, but in clinical conditions such as hypertension or diabetes, the reduction of elevated heart rate appears a desirable additional goal of therapy.

Effect of Drugs Interacting With the Dopaminergic Receptors on Glucose Levels and Insulin Release in Healthy and Type 2 Diabetic Subjects

Dopamine agonists play an important role in the regulation of the central nervous-cardiovascular, renal, and hormonal systems through stimulation of dopaminergic (DA1 and DA2) and alpha- and beta-adrenergic receptors. Several studies have shown that in fat and diabetic mice. The aim of the present study was to evaluate the interaction of the dopaminergic and endocrine systems by determining the effect of the dopaminergic antagonist, metoclopramide, and dopamine on insulin secretion and cardiovascular response by blockade and activation of dopamine receptors in healthy and type 2 diabetic subjects. Healthy subjects (n =15) and subjects with type 2 diabetes (n = 15) of both genders, aged 18 to 60 years, were recruited into this study. A comparative experimental design of 90 minutes was performed in which placebo (0.9% saline) was infused intravenously for the first 30 minutes followed by metoclopramide (7.5 microg/kg/min), a dopamine receptor antagonist for 30 minutes, and then metoclopramide (7.5 microg/kg/min) plus dopamine (0.5-3 microg/kg/min) for 30 minutes. The following clinical and biochemical parameters were measured at the beginning and then every 30 minutes of the experimental period (30', 60' and 90'): systolic-diastolic and mean arterial blood pressure, heart rate, serum glucose, insulin, triacylglycerides, and total cholesterol. Baseline glycosylated hemoglobin was measured and homeostasis model assessment for insulin resistance was calculated from insulin and glucose levels. Twelve-lead electrocardiograms were also obtained at these points. Dopamine infusion induced an increase in serum insulin, systolic blood pressure, and heart rate in healthy subjects but not in subjects with type 2 diabetes. Infusion of metoclopramide induced a hypotensive effect in healthy subjects, which was blunted by inclusion of dopamine in the infusion mixture. In subjects with diabetes, metoclopramide had no effect on blood pressure, but addition of dopamine raised systolic blood pressure. Neither metoclopramide nor dopamine altered significantly the lipid profile in healthy or diabetic subjects. Dopaminergic drugs increase serum insulin probably by interacting with dopaminergic receptors, but stimulation of beta-adrenergic receptors cannot be ruled out. Stimulation of cardiovascular dopamine receptors also caused modifications of hemodynamic parameters in healthy subjects, but apparently these receptors are attenuated in patients with type 2 diabetes probably as a result of endothelial dysfunction and alterations in the sympathetic nervous system sensitivity.

Fast and low-cost analysis of heart rate variability reveals vegetative alterations in noncomplicated diabetic patients

The aim of the present preliminary study was to describe a simple protocol for the analysis of the heart rate variability (HRV) that can reveal the different autonomic control between noncomplicated diabetic patients and normal subjects within 15 min. The power spectrum of the HRV was evaluated on 5-min-long electrocardiographic recordings in both the supine and the seated positions in 30 noncomplicated non-insulin-dependent diabetic (NIDDM) patients and in 30 healthy volunteers. In healthy subjects the low-frequency (LF) value was higher in seated position than in supine position, while in diabetic patients the LF value in seated position did not differ from that in supine position and did not differ from that in healthy subjects in supine position. The present work demonstrates that the protocol described reveals a different autonomic regulation of the heart rate in healthy subjects and in NIDDM patients even if there is no clinically evident autonomic neuropathy.

Comparison of Wavelet Transform Modulus Maxima and Multifractal Detrended Fluctuation Analysis of Heart Rate in Patients with Systolic Dysfunction of Left Ventricle

In recent years the WTMM (wavelet transform modulus maxima) and MDFA (multifractal detrended fluctuation analysis) methods have become widely used techniques for the determination of nonlinear, multifractal heart rate (HR) dynamics. The purpose of our study was to compare multifractal parameters of heart rate calculated using both methods in a group of 90 patients with reduced left ventricular systolic function (rlvs group) and in a group of 39 healthy persons (nsr group). For each subject from the rlvs group (LVEF < or =40%) and the nsr group, a 24-hour ECG Holter monitoring was performed. The width of the multifractal spectrum and global Hurst exponent were calculated by means of WTMM and MDFA methods for 5-hour daytime and nighttime subsets. The width of the multifractal spectrum was significantly lower and the Hurst exponent was significantly higher in rlvs group in comparison to nsr group both during diurnal activity and nocturnal rest according to MDFA and only during diurnal activity according to WTMM method. In both groups we observed significant differences of the multifractal spectrum width and the global Hurst exponent between the nighttime and daytime recordings. MDFA seems to be more sensitive as compared with WTMM method in differentiation between multifractal properties of the heart rate in healthy subjects and patients with left ventricular systolic dysfunction.

Effects of regional anesthesia with ropivacaine on arterial pressure and heart rate in healthy subjects

The anesthetic, ropivacaine, has been used extensively in clinical practice, but few studies have evaluated this long-acting local anesthetic in dentistry. In this study we evaluated the effects of ropivacaine alone and ropivacaine + vasoconstrictor on the cardiovascular system when used as a dental anesthetic in volunteers. Thirty-two healthy subjects received two consecutive infiltrations of 1.8 ml of either 0.75% ropivacaine or ropivacaine + epinephrine into the pterygomandibular region. Pain sensation, numbness of the lip, arterial pressure, heart rate, and electrocardiogram changes were monitored for 2 h. The onset of anesthesia was 10 min after the injection and lasted for more than 2 h, and numbness of the lip lasted for approximately 8 h. Ropivacaine alone did not cause significant changes in the cardiovascular parameters, but ropivacaine + epinephrine caused a transient increase in arterial pressure and heart rate 2 min postinjection. We conclude that ropivacaine alone injected into the pterygomandibular region does not affect the cardiovascular system and that the addition of epinephrine has no beneficial effect. This finding may be relevant to dentists endeavoring to find an anesthetic of minimal cardiovascular risk to produce regional anesthesia for long-lasting procedures without the need of a vasoconstrictor.

Safety of unoprostone isopropyl as mono- or adjunctive therapy in patients with primary open-angle glaucoma or ocular hypertension.

This review summarises the safety of unoprostone isopropyl (both at the 0.12 and 0.15% concentrations) instilled twice daily in patients with primary open-angle glaucoma (POAG) or ocular hypertension (OH). For unoprostone 0.15%, combined data from two 12-month comparative monotherapy studies are reported, as well as data from three adjunctive therapy studies and two special population studies. With unoprostone monotherapy, most adverse events were mild or moderate and transient in nature. Less than 7% of unoprostone-treated patients discontinued therapy due to an adverse event. The most common adverse events associated with unoprostone were burning/stinging, burning/stinging directly upon drug instillation, ocular itching, and conjunctival hyperaemia. Unoprostone had no clinically notable effects on vital signs, laboratory profiles, or comprehensive ophthalmic examinations. One of 659 unoprostone 0.15%-treated patients had a change in iris colour after 12 months of monotherapy. Except for a higher incidence of burning/stinging and burning/stinging upon instillation, unoprostone was comparable to timolol 0.5% twice daily and betaxolol 0.5% twice daily. No safety concerns were raised with use of unoprostone as adjunctive therapy. Unoprostone had no significant effect on exercise-induced heart rate in healthy subjects or on pulmonary function in patients with mild-to-moderate asthma. The safety profile of unoprostone 0.15% was consistent with published information on the 0.12% formulation. In conclusion, unoprostone has an excellent safety profile in patients with POAG or OH.

Early Versus Late Morning Measurement of Blood Pressure in Healthy Men. A Potential Source of Measurement Bias?

Standardization of blood pressure (BP) measurement is important for both clinical and epidemiological purposes. The aim of the present study was to investigate early vs late morning measurements of BP and heart rate in healthy subjects. During the years 1972-75, healthy men aged 40-59 years ( n = 2014) participated in a cardiovascular survey in Oslo. Two to four men underwent the examination program per day; it included height/weight, a spirographic study, chest X-ray, a number of blood tests, case history, clinical examination, resting ECG and physical exercise testing. BP and heart rate measurements were meticulously standardized. When adjusting for age, smoking habits and season of year we found that men who were examined as number one in the row of two to four subjects each morning had higher systolic BP (3.6 mmHg, p < 0.001) and heart rate (3.6 beats/min, p < 0.001) at rest compared to others. They were virtually identical in all other aspects. These differences in systolic BP and heart rate at rest disappeared during bicycle exercise. Thus, we suggest that the increased BP and heart rate at rest represent a stress reaction to being number one in a row of subjects to be examined, i.e. a bias in BP and heart rate measurements, possibly of both clinical and epidemiological importance.

Need for a Revision of the Normal Limits of Resting Heart Rate

The current definition of sinus tachycardia is a heart rate >100 beats per minute (bpm).1 This limit was set arbitrarily when heart rate was not yet regarded as a risk factor for cardiovascular disease, probably with the main purpose of distinguishing between a disease state (fever, thyrotoxicosis, anemia, congestive heart failure, etc) and a normal condition. In recent years, interest has been aroused by the awareness that fast heart rate is a potent precursor of hypertension, atherosclerosis, and their sequelae.2 3 4 5 6 7 8 9 10 In addition, many leading epidemiological studies have shown that tachycardia is associated with an increased risk of death from cardiovascular and noncardiovascular causes. This relationship has been found in general populations,3 4 5 6 7 in elderly individuals,9 and in hypertensive cohorts.10 In all of these studies, the heart rate value above that in which a significant increase in risk was observed was below the 100 bpm threshold (Table 1⇓). Only in the study by Levy et al3 was tachycardia defined as a heart rate >99 bpm, but in that study the cutoff between normal and high heart rate was chosen arbitrarily, and the highest heart rate value measured during the examination was taken to define the subject’s heart rate. In all the other studies, the threshold level between normal and fast heart rate was between 79 and 90 bpm. View this table: Table 1. Heart Rate Values Above Which a Significant Increase in Risk Was Found: Data From 9 Epidemiological Studies The normalcy limits of a clinical variable can be established according to different criteria. For many parameters, such as most biochemical indexes, the 95% confidence interval is calculated to identify the upper normal limit of the variable. This statistical approach does not appear suitable for those clinical variables …

Renal Dose Dopamine Does Not Alter the Response to ß-Adrenergic Stimulation by Isoproterenol in Healthy Human Volunteers

To determine if renal dose dopamine (3 microg/kg/min) alters the heart rate (HR) by itself, or if a dopamine infusion alters the HR response to bolus doses of the beta-adrenergic agonist isoproterenol in healthy human subjects. Prospective study. Clinical laboratory of a university-affiliated academic medical center. A total of 15 healthy nonpregnant women and men aged 21 to 44 years. Subjects were monitored continuously with bedside ECG, pulse oximetry, and ambulatory ECG recording to measure the maximal HR response to separate injections of 10, 20, and 30 ng/kg of isoproterenol, given before, during, and after the infusion of 3 microg/kg/min of dopamine. Dopamine in the absence of isoproterenol did not alter baseline HR significantly (62.7+/-2.2 beats/min without dopamine; 65.4+/-2.2 with dopamine; p=0.15). All three doses of isoproterenol increased HR significantly above baseline, both in the presence and absence of dopamine (p<0.001). Dopamine infusion resulted in a higher HR following isoproterenol only for the 20-ng/kg dose. The incremental increases in HR, defined as the difference between peak HR following isoproterenol and baseline HR, were not increased during dopamine infusion for any of the doses of isoproterenol. Nausea was reported by 5 of the 15 subjects during the dopamine infusion. In healthy human subjects, infusion of 3 microg/kg/min of dopamine does not significantly increase the HR when combined with beta-adrenergic stimulation using isoproterenol, suggesting neither an additive nor antagonistic interaction between the two drugs. While our study did not demonstrate an increase in HR in healthy subjects, the risk of increasing the chronotropic response to beta-adrenergic inotropic medications with "renal dose" dopamine in critically ill patients needs to be investigated. The frequency of nausea during dopamine infusion also may influence consideration of using dopamine to augment splanchnic blood flow and renal function in conscious patients.

The acute effects of smoking on heart rate and blood pressure: An ambulatory study

AbstractUnder laboratory conditions smoking has been found to acutely increase blood pressure and heart rate in healthy subjects. Little is known about the short‐term effects of smoking under more naturalistic conditions when subjects are engaged in various activities. In this study, the short‐term effects of smoking on blood pressure and heart rate in natural settings were investigated in a group of healthy smokers. The degree to which these effects are moderated by other factors known to affect the cardiovascular system was investigated as well. Subjects (eight males, seven females) were dispatchers in the greater Los Angeles area. They wore an ambulatory blood pressure and heart rate monitor on two workdays for a total of 48 h. The present study confirmed that the acute effects of smoking on blood pressure and heart rate under natural conditions are similar to results from laboratory studies. Smoking acutely increased blood pressure and heart rate. Male and female smokers displayed similar cardiovascular reactivity to smoking. There was no indication of development of intraday tolerance. The acute action of smoking on blood pressure and heart rate was additive to the influence of posture on the cardiovascular system.

Parasympathetic activity is a major modulator of the circadian variability of heart rate in healthy subjects and in patients with coronary artery disease or diabetes mellitus

Autonomic heart rate control was assessed by power spectral analysis of heart rate variability in 24-hour ambulatory electrocardiographic recordings from 23 healthy subjects, 14 patients with coronary artery disease without cardiac dysfunction, and 14 patients with diabetes mellitus. The log value of the ratio of the low-frequency component (LF = 0.04 to 0.15 Hz) to the high-frequency component (HF = 0.15 to 0.5 Hz) and logHF were employed as indexes of sympathetic and parasympathetic activity, respectively. Diurnal and nocturnal logLF, logHF, and log(LF/HF) values were calculated for heart rates of 60, 70, and 80 beats/min. Intergroup differences among these three variables were not significant at any heart rate. Although a heart rate-related decrease in logHF was generally observed, the relationship between log(LF/HF) and heart rate was not consistent. The correlation between diurnal and nocturnal logHF values was significant at all three heart rates (r = 0.63, 0.87, and 0.59), whereas the diurnal log(LF/HF) was correlated with the nocturnal value only at 70 beats/min (r = 0.77). These results suggest that the heart rate during normal daily activities is a reliable indicator of parasympathetic tone, if not sympathetic tone, in healthy subjects and patients with coronary artery disease or diabetes mellitus.