CLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 2007
Y Kubota
SUMMARY 1We previously reported that Ginkgo biloba extract (GBE) improves cardiovascular function in young spontaneously hypertensive rats (SHR). In the present study, changes in the cardiovascular parameters of aged SHR were examined following a 4-week diet of GBE. 2Feeding with GBE significantly decreased the heart rate and blood flow velocity in the tails of aged SHR. The contractile and relaxation responses were unchanged in isolated aortas and mesenteric arteries of aged SHR fed the GBE diet. The GBE diet did not influence the protein levels of endothelial nitric oxide synthase or soluble guanylyl cyclase in the aortas. 3These findings indicate that in aged SHR, the ingestion of GBE may cause bradycardia without a beneficial effect on the vascular relaxation response. Intake of GBE as a supplement in elderly hypertensive patients should be carefully monitored. [source]

Vagus Nerve Stimulation Therapy Induces Changes in Heart Rate of Children during Sleep

EPILEPSIA, Issue 5 2007
Boubker Zaaimi
Summary:,Purpose: This study analyzed changes in the heart rates of children receiving vagus nerve stimulation (VNS) therapy for pharmacoresistant epilepsy. Methods: Changes in the heart rates of ten children receiving VNS therapy for pharmacoresistant epilepsy were evaluated with polysomnographic recordings, including electrocardiogram (ECG), EEG, thoraco-abdominal distension, nasal airflow, and VNS artifacts. Measurements during stimulation were compared with those at baseline for each patient. Result: While the VNS therapy pulse generator was delivering stimulation, the heart rates of four children increased significantly (p < 0.01), decreased for one child, and increased at the end of the stimulation for one child. The heart rates of four children did not change. Changes in heart rate varied during VNS, within stimulation cycles for individual children and from one child to another. Changes in heart rate differed between rapid eye movement (REM) and non-REM (NREM) sleep states. Respiratory changes (increases in frequency and decreases in amplitude) were concomitant with the changes in heart rate. Conclusion: In this case series of children with pharmacoresistant epilepsy, cardiorespiratory variations occurred while the VNS therapy pulse generator was delivering stimulation. Understanding these variations may allow further optimization of VNS parameters. [source]

Heart Rate and its Variability Change After the Menopause

EXPERIMENTAL PHYSIOLOGY, Issue 3 2000
C. L. Brockbank
Resting heart rate and heart rate variability of 33 postmenopausal women were compared with those of 50 premenopausal women of comparable activity level, none of whom had used hormone replacement therapy. Heart rate was measured as the mean of at least 600 consecutive R-R intervals obtained from electrocardiograph (ECG) records, and its variability as the standard deviation of these intervals. Activity levels were assessed by a scale modified from the Allied Dunbar National Fitness Survey (1992). There was a significant reduction in both mean R-R interval and the standard deviation in the postmenopausal women who had experienced their last menstrual period (LMP) 1 year or more prior to the observations being made, but no observable changes during the first year post menopause. [source]

Sex Differences in the Effect of Heart Rate on Mortality in the Elderly

JOURNAL OF AMERICAN GERIATRICS SOCIETY, Issue 9 2003
Gila Perk MD
Objectives:, To examine the association between heart rate and mortality risk in the elderly. Design:, Longitudinal cohort. Setting:, Outpatient. Participants: Four hundred twenty-two people, aged 70 upon entry, were surveyed and followed for 6 years. Measurements: Pulse rate was measured manually, while sitting and standing, and heart rate was measured from electrocardiogram recordings. The population was divided into quartiles of heart rate, with the top quartile comprising those with heart rate greater than 77 beats per minute (bpm) and the bottom quartile those with heart rate less than 60 bpm. Results: After controlling for possible confounders, there was a clear correlation (r) between heart rate and all-cause mortality in elderly women (r=0.25, P=.0003). The correlation in women was observed using the three different methods for measuring heart rate. Heart rate was associated with all-cause and cardiovascular mortality. There was no relationship between heart rate and level of exercise or smoking status. In multiple regression analysis, the increased risk of death in the women was independent of previous cardiovascular or cerebrovascular disease, hypertension, anemia, congestive heart failure, smoking, and level of exercise or activities of daily living (relative odds ratio (ROR)=3.37, 95% confidence interval (CI)=0.96,11.8). When women using beta-blockers were excluded, this relationship became even stronger (ROR=8.5, 95% CI=1.19,60.1). Conclusion: Elevated heart rate is related to increased mortality in elderly women, thus representing a simple index of general health status in this population. Elevated heart rate did not predict mortality in elderly men. [source]

The Normal Effects of Epinephrine and Isoproterenol on Heart Rate and QT Interval: Role in Unmasking the Long QT Syndrome

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 9 2006
DAVID M. FITZGERALD M.D., F.H.R.S.Article first published online: 26 JUL 200
No abstract is available for this article. [source]

Relationship Between Heart Rate Turbulence and Heart Rate, Heart Rate Variability, and Number of Ventricular Premature Beats in Coronary Patients

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 7 2004
IWONA CYGANKIEWICZ M.D., Ph.D.
Introduction: Heart rate variability (HRV) illustrates regulation of the heart by the autonomic nervous system whereas heart rate turbulence (HRT) is believed to reflect baroreflex sensitivity. The aim of this study was to determine the association between HRT and HRV parameters and the relationship between HRT parameters and heart rate and number of ventricular premature beats (VPBs) used to calculate HRT parameters. Methods and Results: In 146 patients (117 males and 29 females; mean age 62 years) with coronary artery disease, a 24-hour ECG Holter monitoring was performed to calculate mean heart rate (RR interval), number of VPBs, time- and frequency-domain HRV parameters and two HRT parameters: turbulence onset (TO) and turbulence slope (TS). Univariate and multivariate regression analyses were performed to evaluate the association between tested parameters. Significant correlation between TS and mean RR interval was observed (r = 0.42; p < 0.001), while no association for TO vs. RR interval was found. TS values were significantly higher in patients with less than 10 VPBs/24 hours than in patients with more frequent VPBs. Significant associations between HRT and HRV parameters were found with TS showing stronger correlation with HRV parameters than TO (r value ranging from 0.35 to 0.62 for TS vs. ,0.16 to ,0.38 for TO). Conclusion: HRT parameters correlate strongly with HRV parameters indicating that HRT should be considered as a reflection of both baroreceptors response and overall autonomic tone. Heart rate dependence of turbulence slope indicates the need to adjust this parameter for heart rate. (J Cardiovasc Electrophysiol, Vol. 15, pp. 731-737, July 2004) [source]

Gender-Related Differences in Modulation of Heart Rate in Patients with Congestive Heart Failure

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 10 2000
DORON ARONSON M.D.
Gender and HRV in Heart Failure Introduction. The prognosis of women with congestive heart failure (CHF) is better than that for men, but the mechanisms underlying the female survival advantage are not well understood. CHF is characterized by profound abnormalities in cardiac autonomic control that contribute to progressive circulatory failure and influence survival. Methods and Results. Time- and frequency-domain heart rate variability (HRV) indexes were obtained from 24-hour Holter recordings and compared to assess the role of gender in 131 men and 68 women with CHF (mean age 60 ± 13.6 years, range 21 to 87; New York Heart Association Functional Class III [66%] and IV [34%]). Gender-related differences in HRV were observed only in the subset of patients with nonischemic heart failure (55 men and 39 women). Among the time-domain indexes, the SD of the RR intervals (76 ± 5.3 msec vs 55.3 ± 3.2 msec, P < 0.0001) and indexes denoting parasympathetic modulation, the percentage of RR intervals with >50 msec variation (4.0%± 1.0% vs 6.5%± 1.3%, P = 0.02), and the square root of mean squared differences of successive RR intervals (19.1 ± 3.3 vs 28.4 ± 3.8, P = 0.004) were higher in women. Among the frequency-domain indexes, the total power (7.5 ± 0.13 In-msec2 vs 8.3 ± 0.14 In-msec2, P = 0.0002), the ultralow-frequency power (7.2 ± 0.11 In-msec2 vs 8.0 ± 0.14 In-msec2, P < 0.0001), the low-frequency power (3.8 ± 0.25 In-msec2 vs 4.8 ± 0.28 In-msec2, P = 0.006), and the high-frequency power (3.8 ± 0.24 In-msec2, vs 4.6 ± 0.26 In-msec2, P = 0.003) were greater in women than in men. Conclusion. Women with nonischemic CHF have an attenuated sympathetic activation and parasympathetic withdrawal compared with men. Gender-based differences in autonomic responses in the setting of CHF may be related to the female survival advantage. (J Cardiovasc Electrophysiol, Vol. 11, pp. 1071-1077, October 2000) [source]

Should the Heart Rate of Hypertensive Patients Influence Clinical Decisions?

JOURNAL OF CLINICAL HYPERTENSION, Issue 12 2008
DPhil, Thomas G. Pickering MD
First page of article [source]

Optimal Body Temperature in Transitional Extremely Low Birth Weight Infants Using Heart Rate and Temperature as Indicators

JOURNAL OF OBSTETRIC, GYNECOLOGIC & NEONATAL NURSING, Issue 1 2010
Robin B. Knobel
ABSTRACT Objective: To explore body temperature in relationship to heart rate in extremely low birth weight (ELBW) infants during their first 12 hours to help identify the ideal set point for incubator control of body temperature. Design: Within subject, multiple-case design. Setting: A tertiary neonatal intensive care unit (NICU) in North Carolina. Participants: Ten infants born at fewer than 29 weeks gestation and weighing 400 to 1,000 g. Methods: Heart rate and abdominal body temperature were measured at 1-minute intervals for 12 hours. Heart rates were considered normal if they were between the 25th and 75th percentile for each infant. Results: Abdominal temperatures were low throughout the 12-hour study period (mean 35.17-36.68 °C). Seven of 10 infants had significant correlations between abdominal temperature and heart rate. Heart rates above the 75th percentile were associated with low and high abdominal temperatures; heart rates less than the 25th percentile were associated with very low abdominal temperatures. The extent to which abdominal temperature was abnormally low was related to the extent to which the heart rate trended away from normal in 6 of the 10 infants. Optimal temperature control point that maximized normal heart rate observations for each infant was between 36.8 °C and 37 °C. Conclusions: Hypothermia was associated with abnormal heart rates in transitional ELBW infants. We suggest nurses set incubator servo between 36.8 °C and 36.9 °C to optimally control body temperature for ELBW infants. [source]

Computer Analysis of the Fetal Heart Rate

JOURNAL OF OBSTETRIC, GYNECOLOGIC & NEONATAL NURSING, Issue 5 2000
Patricia Robin McCartney RNC
Computer analysis of the fetal heart rate is a technology of the Information Age commercially available for research and clinical practice. Intelligent systems are engineered with algorithms or neural networks designed to simulate expert knowledge. Automated analysis has provided objective, standardized, and reproducible data used to research fetal heart rate responses in the antepartum and intrapartum setting. Perinatal information systems can integrate FHR analysis and data management. [source]

Perioperative Assessment of Fetal Heart Rate and Uterine Activity

JOURNAL OF OBSTETRIC, GYNECOLOGIC & NEONATAL NURSING, Issue 3 2000
Maribeth Inturrisi RN
Improvements in surgical techniques and anesthesia allow women the option to schedule needed surgery during pregnancy. However, perioperative monitoring of the fetus and uterine activity remains a matter of controversy. Monitoring may allow rapid improvement of the fetal status or uterine activity when early compromise or contractions are detected. The reassurance and decreased medicolegal risks provided by perioperative monitoring may offset the cost of a perinatal nurse and use of monitoring equipment even though the drug and anesthetic effect on the fetal heart limit the benefits of monitoring. Simply providing adequate maternal respiratory support during surgery may improve the fetal pattern but will not eliminate external surgical effects. The need for additional research is described, and the role of the perinatal nurse is detailed in a suggested protocol. [source]

Adrenergic Receptor Polymorphisms Associated with Resting Heart Rate: The HyperGEN Study

ANNALS OF HUMAN GENETICS, Issue 5 2006
J. B. Wilk
Summary The association between polymorphisms in the ,1, ,2 and ,2B adrenergic receptor (ADR) genes (ADRB1, ADRB2 and ADRA2B) and resting heart rate was examined in white and African-American participants of the HyperGEN Study. All analyses were adjusted for age, sex, body mass index, alcohol use, smoking status and daily exercise within strata of race, hypertension status and beta-blocker use. The Ser49Gly polymorphism of the ,1 ADR was associated with resting heart rate in hypertensive African-Americans and hypertensive whites taking beta-blockers, with carriers of the Gly allele having a higher mean resting heart rate by 2.7 and 4.4 beats per minute (bpm), respectively. The Arg389Gly polymorphism of the ,1 ADR was associated with lower heart rate in the normotensive African-American sample. A ,1 haplotype (Ser49Gly-Arg389Gly) was modestly associated with resting heart rate in the hypertensive African-Americans. The ,2B C/A polymorphism was associated with heart rate in hypertensive whites, and both whites and African-Americans taking beta-blockers, with carriers of the A allele having a higher mean resting heart rate. In summary, each of the ADR gene polymorphisms was associated with heart rate in at least one stratum studied, but there was no consistent association from which one would infer a large genetic contribution to heart rate. [source]

Influence of the Maximum Heart Rate Attained during Exercise Testing on Subsequent Heart Rate Recovery

ANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 1 2010
Sina Zaim M.D.
Background: Abnormal heart rate recovery (HRR) following exercise testing has been shown to be a predictor for adverse cardiovascular events. The actual maximum heart rate (MHR) attained during the exercise test does not however have a distinct significance in traditional HRR assessment. The objective of this study was to investigate the role of MHR in HRR. Methods: This prospective study consisted of 164 patients (62% male, mean age 53.7 ± 11.7 years) who were referred for a symptom-limited standard Bruce Protocol treadmill exercise test, based on clinical indications. The patients were seated immediately at test completion and the heart rate (HR) recorded at one and two minutes postexercise. A normal HRR was defined as a HR drop of 18 beats per minute or more at the end of the first minute of recovery. The HRR profile of patients who reached ,85% of their maximum predicted heart rate (MPHR) during peak exercise were then compared to HRR profile of those who could not. Results: One hundred twelve patients (Group A) achieved a MHR , 85% of MPHR during peak exercise whereas 52 patients (Group B) did not. Chi-square analysis showed a higher incidence of normal HRR in Group A compared to Group B (p = 0.029). Analysis of variance with repeated measures showed that group A had a greater HRR at the first minute F1,162= 6.98, p = <0.01) but not the second minute (F1,162=1.83, p = .18) postexercise. Conclusion: There is a relation between the peak heart rate attained during exercise and the subsequent HRR. A low peak heart rate increases the likelihood of a less than normal HRR. Assessment of the entire heart-rate response seems warranted for more thorough risk-stratification. Ann Noninvasive Electrocardiol 2010;15(1):43,48 [source]

Familial Aggregation and Heritability of Electrocardiographic Intervals and Heart Rate in a Rural Chinese Population

ANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 2 2009
Jianping Li M.D., Ph.D.
Background: Estimates of the genetic influences on electrocardiographic (ECG) parameters are inconsistent in previous reports, and no such studies have been performed in China. So we estimated genetic contributions to PR and QRS intervals and the rate-adjusted QT interval (Bazett's QTc) in a Chinese rural population. Methods: A total of 2909 subjects from 847 families were enrolled in the current study. Genetic contributions to ECG parameters were estimated in two ways: correlation coefficients among family members (father-mother, parent-offspring, first sibling-other sibling) and the heritability of each of the ECG parameters. Results: Our results showed significant correlations among family members on theses parameters: the correlation coefficients for PR interval, QRS duration, QTc interval, and HR, between parent-sibling, and sibling-sibling were 0.17 and 0.13, 0.18 and 0.23, 0.22 and 0.28, 0.19 and 0.18, respectively. The heritability for PR interval, QRS duration, QTc interval, and HR were estimated as 0.34, 0.43, 0.40, and 0.34, respectively. Conclusion: Genetic factors, together with the environmental and other cofactors contribute no more than 60% to the variance of the ECG intervals, supporting the concept that multiple factors, including gene-gene and gene-environment interactions could influence ECG interval phenotypes, and genetic factors play a major role. [source]

Open-loop Analysis of Transfer Characteristics from Blood Pressure to Heart Rate Using an Effectively Total Artificial Heart

ARTIFICIAL ORGANS, Issue 1 2004
Akira Tanaka
Abstract:, ,It is desirable for the dynamic behavior of the drive rate of the artificial heart to be as similar as possible to that of the recipient's heart rate (HR) before implantation. This requires a model which can simulate the behavior of HR on the basis of only the information measured with the limited number of approvable implanted sensors. This article provides a linear time series model for explaining the behavior of HR only with aortic pressure and right atrial pressure. This could be obtained from open-loop analysis using a total artificial heart, which was introduced for measuring HR in vivo and for eliminating its effect on blood pressure. The model was identified in a goat equipped with a special biventricular assist device called the effectively total artificial heart (ETAH). The ETAH was introduced to make an open loop and awake situation in the animal with almost intact autonomic nerves, which could enhance the accuracy and reliability of the identification of the model. The adequacy of the proposed model was ascertained in several data sets measured in two goats, which were different from the data set used for identification. Most of the mean estimation errors were less than 3 beats/min and auto-correlation analysis showed approvable statistical appropriateness. However, it was clarified through comparison with the 1/R control method that the proposed model has a few problems still to be solved before its future implementation as an automatic controller of the TAH. [source]

Aortic Valve Closure: Relation to Tissue Velocities by Doppler and Speckle Tracking in Patients with Infarction and at High Heart Rates

ECHOCARDIOGRAPHY, Issue 4 2010
Ph.D., Svein A. Aase M.Sc.
Aim: To resolve the event in tissue Doppler (TDI)- and speckle tracking-based velocity/time curves that most accurately represent aortic valve closure (AVC) in infarcted ventricles and at high heart rates. Methods: We studied the timing of AVC in 13 patients with myocardial infarction and in 8 patients at peak dobutamine stress echo. An acquisition setup for recording alternating B-mode and TDI image frames was used to achieve the same frame rate in both cases (mean 136.7 frames per second [FPS] for infarcted ventricles, mean 136.9 FPS for high heart rates). The reference method was visual assessment of AVC in the high frame rate narrow sector B-mode images of the aortic valve. Results: The initial negative velocities after ejection in the velocity/time curves occurred before AVC, 44.9 ± 21.0 msec before the reference in the high heart rate material, and 25.2 ± 15.2 msec before the reference in the infarction material. Using this time point as a marker for AVC may cause inaccuracies when estimating end-systolic strain. A more accurate but still a practical marker for AVC was the time point of zero crossing after the initial negative velocities after ejection, 5.4 ± 15.3 msec before the reference in high heart rates and 8.2 ± 12.9 msec after the reference in the infarction material. Conclusion: The suggested marker of AVC at high heart rate and in infarcted ventricles was the time point of zero crossing after the initial negative velocities after ejection in velocity/time curves. (Echocardiography 2010;27:363-369) [source]

Short-Term Effects of Right Ventricular Pacing on Cardiorespiratory Function in Patients With a Biventricular Pacemaker

CONGESTIVE HEART FAILURE, Issue 6 2008
Stefan Toggweiler MD
The intention of this study was to evaluate the short-term effect of right ventricular (RV) pacing on cardiorespiratory function in patients with a biventricular pacemaker. A group of 26 patients with a biventricular pacemaker was enrolled in this cross-over, single-blind study. All patients underwent spiroergometry and electrocardiography in RV and biventricular pacing mode. Peak work capacity (102±32 W and 107±34 W for RV and biventricular pacing mode, respectively; P<.01) and peak oxygen consumption (21.4±6.7 mL/min/kg and 22.6±7.0 mL/min/kg for RV and biventricular pacing mode, respectively; P<.01) were significantly lower in the RV pacing mode. Heart rate at rest was significantly higher with active RV pacing. Short-term RV pacing in patients with a biventricular pacemaker resulted in a higher heart rate at rest, a lower peak work capacity, and a lower peak oxygen consumption compared with that in the biventricular pacing mode. [source]

Effect of reduced total blood volume on left ventricular volumes and kinetics in type 2 diabetes

ACTA PHYSIOLOGICA, Issue 1 2010
S. Lalande
Abstract Aim:, Although impaired left ventricular (LV) diastolic function is commonly observed in patients with type 2 diabetes, it remains unclear whether the impairment is caused by altered LV relaxation or changes in LV preload. The purpose of this study was to examine the influence of LV function and LV loading conditions on stroke volume in men with type 2 diabetes. Methods:, Cardiac magnetic resonance imaging scans were performed in eight men with type 2 diabetes and 11 non-diabetic men matched for age, weight and physical activity level. Total blood volume was determined with the Evans blue dye dilution technique. Results:, End-diastolic volume (EDV), the ratio of peak early to late mitral inflow velocity (E/A) and stroke volume were lower in men with type 2 diabetes than in non-diabetic individuals. Peak filling rate and peak ejection rate were not different between diabetic and non-diabetic individuals; however, men with type 2 diabetes had proportionally longer systolic duration than non-diabetic individuals. Heart rate was higher and total blood volume was lower in men with type 2 diabetes. The lower total blood volume was correlated with a lower EDV in men with type 2 diabetes. Conclusions:, Men with type 2 diabetes have an altered cardiac cycle and lower end-diastolic and stroke volume. A lower total blood volume and higher heart rate in men with type 2 diabetes suggest that changes in LV preload, independent of changes in LV relaxation or contractility, influence LV diastolic filling and stroke volume in this population. [source]

Lowered albumin extravasation rate in heart but not in other organs in ,3-integrin-deficient mice

ACTA PHYSIOLOGICA, Issue 4 2009
Ø. S. Svendsen
Abstract Aim:, The vascular protein permeability is dependent on the integrity of the vascular wall. The heart capillaries in male mice lacking ,3 integrins have an immature phenotype. Previously, we have demonstrated a role for ,v,3 integrins in control of interstitial fluid pressure (Pif) and thereby in the fluid flux during inflammation. We wanted to explore a possible role for ,v,3 integrins in controlling capillary protein permeability during control situation and inflammation. Methods:, We performed double-tracer and microdialysis experiments on ,3-integrin-deficient mice and wild type control mice. We also measured blood pressure and heart rate in the two mice strains. Results:, We found reduced albumin extravasation (during 25 min) in the heart capillaries (0.053 ± 0.003 vs. 0.087 ± 0.009 mL g,1 dw, P < 0.05), and an increased cardiac mass/body weight (5.3 × 10,3 ± 0.3 × 10,3 vs. 3.8 × 10,3 ± 0.1 × 10,3, P < 0.01) in the ,3-integrin-deficient mice (n = 6) compared with the controls (n = 6). Heart rate and blood pressure were the same in mice with and without ,3-integrins. No difference in permeability was found in other tissues studied, or under local inflammation. Conclusion:, These results show a function for the ,v,3 integrin in the regulation of protein permeability, selective for the heart capillaries. [source]

Adenosine infusion attenuates soluble RAGE in endotoxin-induced inflammation in human volunteers

ACTA PHYSIOLOGICA, Issue 1 2009
A. Soop
Abstract Aim:, To evaluate possible anti-inflammatory effects of pre-treatment with adenosine in a human experimental inflammatory model. Methods:, The study design was double-blind, crossover, placebo-controlled and randomized. In the Intensive Care Unit of a university hospital, 16 healthy male volunteers were treated for 5.5 h with infusions of adenosine 40 ,g kg,1 min,1 or placebo. Thirty minutes after the start of adenosine or placebo, 2 ng kg,1E-Coli endotoxin was administered. Heart rate, body temperature, blood pressure, plasma cytokines (TNF-,, IL-6 and IL-10), soluble RAGE and resistin, exhaled nitric oxide and nitrite/nitrate in urine were determined. Results:, Endotoxin elicited the expected clinical signs of an inflammatory reaction (tachycardia, fever) and led to prominent release of the cytokines studied (P < 0.001). Resistin in plasma increased after endotoxin (P < 0.001). After placebo treatment, soluble RAGE (sRAGE) in plasma increased 5 h after the endotoxin challenge (P < 0.001) but not after adenosine. After placebo, orally exhaled NO increased with a peak at 4 h (P < 0.001), although there was no statistically significant difference between the two treatments. Nitrite/nitrate in urine (n = 11) did not differ between adenosine and placebo treatments. Conclusion:, In conclusion, adenosine infusion starting before endotoxin challenge in humans attenuated sRAGE significantly but otherwise had no clear anti-inflammatory effect. Adenosine as a potential anti-inflammatory treatment in humans needs further study, including use of higher doses. The mechanism underlying the effect of adenosines on sRAGE remains unknown. [source]

Circulatory effects of apnoea in elite breath-hold divers

ACTA PHYSIOLOGICA, Issue 1 2009
F. Joulia
Abstract Aim:, Voluntary apnoea induces several physiological adaptations, including bradycardia, arterial hypertension and redistribution of regional blood flows. Elite breath-hold divers (BHDs) are able to maintain very long apnoea, inducing severe hypoxaemia without brain injury or black-out. It has thus been hypothesized that they develop protection mechanisms against hypoxia, as well as a decrease in overall oxygen uptake. Methods:, To test this hypothesis, the apnoea response was studied in BHDs and non-divers (NDs) during static and dynamic apnoeas (SA, DA). Heart rate, arterial oxygen saturation (SaO2), and popliteal artery blood flow were recorded to investigate the oxygen-conserving effect of apnoea response, and the internal carotid artery blood flow was used to examine the mechanisms of cerebral protection. Results:, The bradycardia and peripheral vasoconstriction were accentuated in BHDs compared with NDs (P < 0.01), in association with a smaller SaO2 decrease (,2.7% vs. ,4.9% during SA, P < 0.01 and ,6% vs. ,11.3% during DA, P < 0.01). Greater increase in carotid artery blood flow was also measured during apnoea in BHDs than in controls. Conclusion:, These results confirm that elite divers present a potentiation of the well-known apnoea response in both SA and DA conditions. This response is associated with higher brain perfusion which may partly explain the high levels of world apnoea records. [source]

Pressure-independent cardiac effects of angiotensin II in pigs

ACTA PHYSIOLOGICA, Issue 2 2004
M. Broomé
Abstract Background:, Angiotensin II (Ang II) is a potent vasoconstrictor with an important role in the development of cardiovascular disease. Earlier results have shown a positive acute inotropic effect of Ang II in anaesthetized pigs together with significant vasoconstriction. This investigation was designed to study cardiac effects of Ang II, when blood pressure was maintained constant by experimental means. Methods:, Ang II (200 ,g h,1) was infused in anaesthetized pigs (n = 10) at two different arterial blood pressures, the first determined by the effects of Ang II alone, and the second maintained at baseline blood pressure with nitroprusside. Cardiac systolic and diastolic function was evaluated by analysis of left ventricular pressure,volume relationships. Results:, Heart rate, end-systolic elastance (Ees) and pre-load adjusted maximal power (PWRmax EDV,2) increased at both blood pressure levels, although less when blood pressure was kept constant with nitroprusside. The time constant for isovolumetric relaxation (,1/2) was prolonged with Ang II alone and shortened with Ang II infused together with nitroprusside. Conclusion:, Ang II infusion in the pig has inotropic and chronotropic properties independent of arterial blood pressure levels, although the effects seem to be blunted by pharmacological actions of the nitric oxide donor nitroprusside. [source]

Heart rate and QT variability in children with anxiety disorders: A preliminary report

DEPRESSION AND ANXIETY, Issue 2 2001
Vikram K. Yeragani M.B.B.S.
Abstract This study compared beat-to-beat heart rate and QT variability in children with anxiety disorders (n=7) and normal controls (n=15) by using an automated algorithm to compute QT intervals. An increase in QT variability appears to be associated with a higher risk for sudden cardiac death. A decrease in heart rate variability is also linked to significant cardiovascular events. Supine detrended QT variability, QT variability corrected for mean QT interval, and QTvi (a log ratio of QT variance normalized for mean QT over heart rate variability normalized for mean heart rate) were significantly higher in children with anxiety compared to controls (P<0.05). The largest Lyapunov Exponent (LLE) of heart rate time series was significantly lower (P<0.05) in children with anxiety compared to controls. These findings suggest a relative increase in sympathetic activity and a relative decrease in cardiac vagal activity in children with anxiety disorders, and are discussed in the context of the effects of tricyclics on cardiac autonomic function in children, and the rare occurrence of sudden death during tricyclic antidepressant treatment. Depression and Anxiety 13:72,77, 2001. © 2001 Wiley-Liss, Inc. [source]

Acute Cardiac Effects of Nicotine in Healthy Young Adults

ECHOCARDIOGRAPHY, Issue 6 2002
Catherine D. Jolma M.D.
Background: Nicotine is known to have many physiologic effects. The influence of nicotine delivered in chewing gum upon cardiac hemodynamics and conduction has not been well-characterized. Methods: We studied the effects of nicotine in nonsmoking adults (6 male, 5 female; ages 23,36 years) using a double-blind, randomized, cross-over study. Subjects chewed nicotine gum (4 mg) or placebo. After 20 minutes (approximate time to peak nicotine levels), echocardiograms and signal-averaged electrocardiograms (SAECG) were obtained. After 40 minutes, subjects were again given nicotine gum or placebo in cross-over fashion. Standard echocardiographic measurements were made from two-dimensional images. We then calculated end-systolic wall stress (ESWS), shortening fraction (SF), systemic vascular resistance (SVR), velocity for circumferential fiber shortening corrected for heart rate (Vcfc), stroke volume, and cardiac output. P wave and QRS duration were measured from SAECG. Results: Significant differences (P < 0.05) from control or placebo were found for ESWS, mean blood pressure, cardiac output, SVR, heart rate, and P wave duration. No significant changes were seen in left ventricular ejection time (LVET), LV dimensions, SF, contractility (Vcfc), or QRS duration. Conclusions: These results suggest that nicotine chewing gum increases afterload and cardiac output. Cardiac contractility does not change acutely in response to nicotine gum. Heart rate and P wave duration are increased by chewing nicotine gum. [source]

Adenosine A1 Antagonism Attenuates Atropine-resistant Hypoxic Bradycardia in Rats

ACADEMIC EMERGENCY MEDICINE, Issue 9 2003
Justin L. Kaplan MD
Abstract Objectives: To test the following hypotheses: Hypoxia induces bradycardia and hemodynamic compromise that are resistant to atropine but responsive to selective antagonism of the adenosine A1 receptor (A1AdoR). The mechanism for such attenuation is independent of the vagus nerve. Methods: Ten minutes after sham or actual bilateral cervical vagotomy, paralyzed ventilated rats were made hypoxic (5% fractional inspired oxygen, continued until death). Five minutes after beginning hypoxia, intravenous treatment with BG-9719, a selective A1AdoR antagonist (0.1 mg/kg); atropine (0.1 mg/kg); BG-9719 vehicle; or saline was initiated. These drug doses were based on pilot studies. Of the eight treatment groups (eight possible combinations of vagotomy status and drug/vehicle treatment), n= 8 in all except nonvagotomized, vehicle-treated rats (where n= 7). Results: Heart rate and left ventricular contractility decreased rapidly with hypoxia. Atropine had minimal effects in prolonging survival (from mean ± SEM of 15.5 ± 2.1 minutes to 20.2 ± 2.5 minutes, p = 0.94) and attenuating posthypoxic decreases in heart rate (p = 0.89) and contractility (p = 0.83) compared with saline. BG-9719 prolonged survival, however, from 14.4 ± 1.9 minutes (with vehicle treatment) to 37.2 ± 6.8 minutes (p < 0.001). Survival, heart rate, and contractility were preserved with BG-9719 compared with atropine and vehicle (p < 0.05, all comparisons). Vagotomy prevented the effects of BG-9719 on survival prolongation (p = 0.003), heart rate (p = 0.01), and contractility (p < 0.001) but did not affect those outcomes in saline-treated rats. Conclusions: Survival, heart rate, and contractility were better preserved with BG-9719 than atropine. A1AdoR selective antagonism, possibly because of its multiple mechanisms for attenuating hypoxic cardiac insufficiency, resulted in better hemodynamic and clinical outcomes. That attenuation seems to have a component of vagal mediation. [source]

Intravenous and intratracheal administration of trimetoquinol, a fast-acting short-lived bronchodilator in horses with ,heaves'

EQUINE VETERINARY JOURNAL, Issue 6 2006
F. C. CAMARGO
Summary Reason for performing study: Trimetoquinol (TMQ) is a potent ,-adrenoceptor agonist bronchodilator used in human medicine but has not been evaluated for potential use as a therapeutic agent for horses with ,heaves'. Objectives: To assess the pharmacodynamics of TMQ in horses with ,heaves' to determine potential therapeutic effects. Methods: Increasing doses of TMQ were administered to horses with ,heaves' by i.v. and intratracheal (i.t.) routes. Doses ranged 0.001,0.2 ,g/kg bwt i.v. and 0.01,2 ,g/kg bwt i.t. Cardiac and airways effects were assessed by measurement of heart rate (HR) and maximal change in pleural pressure (,Pplmax), respectively. Side effects of sweating, agitation and muscle trembling were scored subjectively. Duration of action to i.v. (0.2 ,g/kg bwt) and i.t. (2 ,g/kg bwt) TMQ was evaluated over 6 h. Results: Intravenous TMQ was an exceptionally potent cardiac stimulant. Heart rate increased at 0.01 ,g/kg bwt, and was still increasing after administration of highest dose, 0.2 ,g/kg bwt. Airway bronchodilation, measured as a decrease in ,Pplmax, also commenced at 0.01 ,g/kg bwt. By the i.t. route, TMQ was 50,100-fold less potent than by i.v. Side effects included sweating, agitation and muscle trembling. Overall, the onset of HR and bronchodilator effects was rapid, within about 3 min, but effects were over at 2 h. Conclusion: When administered i.v. and i.t., TMQ is a highly potent cardiac stimulant and a modest bronchodilator. It may not be an appropriate pharmacological agent by i.v. and i.t. routes for the alleviation of signs in horses with ,heaves'. Further studies of TMQ by oral and aerosol routes are necessary. Potential relevance: In horses, TMQ is a fast-acting bronchodilator with a short duration of action. It could be used as a rescue agent during an episode of ,heaves'. The i.v. and i.t. administration of TMQ is associated with side effects, similar to those reported for all other ,-agonists. However, other routes, such as aerosol and oral, may prove useful and safe for the alleviation of bronchoconstriction typical of ,heaves'. [source]

Retrospective study of predictive variables for maximal heart rate (HRmax) in horses undergoing strenuous treadmill exercise

EQUINE VETERINARY JOURNAL, Issue S36 2006
T. L. VINCENT
Summary Reasons for performing study: Heart rate is one of the most commonly measured variables in equine exercise physiology and relative exercise intensity commonly expressed as % of maximal heart rate. A number of influences affect maximal heart rate (HRmax), including age of the horse but other factors have not been described. Objectives: To determine if fitness, health status, gender, breed, athletic use, body mass, in addition to age, are predictive of HRmax in the horse. Methods: Maximal heart rate data from 328 horses which underwent treadmill exercise tests at 5 different laboratories were obtained retrospectively. Univariable linear regression analyses were performed on individual variables. Multiple linear regression analysis using a backward elimination modelling procedure was then used to relate the observed HRmax values simultaneously with different predictive variables. Variables were retained in the final regression model if they or any of their categories were significantly predictive of HRmax at P<0.05 and if there was a significant collective contribution to the model from inclusion of each variable, also at P<0.05. Results: Age, fitness status, laboratory, gender and breed/use (combined category) were all statistically significantly predictive of HRmax. Together these variables accounted for 41% of the variance in HRmax. Age alone accounted for only ,13% of the variation between horses in HRmax. Neither body mass nor health status were significantly predictive. Conclusions: HRmax in the horse declines with age but is also influenced by other factors. As the factors investigated accounted for only 41% of the variation between horses, other unidentified variables with a strong influence on HRmax remain to be identified. Potential relevance: Factors such as fitness, age, gender, breed and use need to be considered when interpreting estimates or measurements of HRmax. [source]

Effects of intravenous lidocaine overdose on cardiac electrical activity and blood pressure in the horse

EQUINE VETERINARY JOURNAL, Issue 5 2001
G. A. MEYER
Summary This study aimed to identify blood serum lidocaine concentrations in the horse which resulted in clinical signs of intoxication, and to document the effects of toxic levels on the cardiovascular and cardiopulmonary systems. Nineteen clinically normal mature horses of mixed breed, age and sex were observed. Lidocaine administration was initiated in each subject with an i.v. loading dose of 1.5 mg/kg bwt and followed by continuous infusion of 0.3 mg/kg bwt/min until clinical signs of intoxication were observed. Intoxication was defined as the development of skeletal muscle tremors. Prior to administration of lidocaine, blood samples for lidocaine analysis, heart rate, mean arterial blood pressure, systolic blood pressure, diastolic blood pressure, respiratory rate and electrocardiographic (ECG) data were collected. After recording baseline data, repeat data were collected at 5 min intervals until signs of intoxication were observed. The range of serum lidocaine concentrations at which the clinical signs of intoxication were observed was 1.85,4.53 ,g/ml (mean ± s.d. 3.24 ± 0.74 ,g/ml). Statistically significant changes in P wave duration, P-R interval, R-R interval and Q-T interval were observed in comparison to control values, as a result of lidocaine administration. These changes in ECG values did not fall outside published normal values and were not clinically significant. Heart rate, blood pressures and respiratory rates were unchanged from control values. This study establishes toxic serum lidocaine levels in the horse, and demonstrates that there were no clinically significant cardiovascular effects with serum lidocaine concentrations less than those required to produce signs of toxicity. [source]

Impact of body fat mass extent on cardiac autonomic alterations in women

EUROPEAN JOURNAL OF CLINICAL INVESTIGATION, Issue 8 2009
J. Sztajzel
Abstract Background, Obesity has been associated with significant abnormalities of the cardiac autonomic regulation. However, the precise impact of increasing body weight on cardiac autonomic function and the metabolic and hormonal contributors to these changes are presently unclear. The aim of our study was to explore in subjects with increasing values of body mass index (BMI) the alterations of cardiac autonomic function and to establish the potential role of various metabolic and hormonal contributors to these alterations. Materials and methods, We investigated time and frequency domain heart rate variability (HRV) parameters taken from 24-h Holter recordings, and several anthropometric, metabolic and hormonal parameters (plasma glucose, insulin, triglycerides, free fatty acids, leptin and adiponectin) in 68 normoglycaemic and normotensive women (mean age of 40 ± 3 years), subdivided according to their BMI into 15 normal body weight (controls), 15 overweight, 18 obese and 20 morbidly obese. Results, Heart rate was increased and HRV was decreased in the morbidly obese group as compared with controls. In overall population, a negative association linked body fat mass (FM) to HRV indices. None of the metabolic and hormonal parameters were significantly related to the HRV indices, after they were adjusted for the body FM. Conclusions, Morbidly obese, normoglycaemic and normotensive young women have increased HR and low HRV, indicating an abnormal cardiac autonomic function and representing a risk factor for adverse cardiovascular events. A decrease of HRV parameters is associated with a progressive increase of body FM. Other metabolic and hormonal factors, characterising obesity, do not show an independent influence on these HRV alterations. [source]

CLINICAL STUDY: Suppression of cue-induced heroin craving and cue-reactivity by single-trial transcutaneous electrical nerve stimulation at 2 Hz

ADDICTION BIOLOGY, Issue 2 2006
Fei Zhong
ABSTRACT The purpose of the present study was to investigate the efficacy of 2 Hz transcutaneous electrical nerve stimulation (TENS) to reduce cue-induced heroin craving and the corresponding cardiovascular responses. Seventy heroin addicts with at least 1 month of abstinence were enrolled and randomly divided into two groups of 35, to receive single-trial 2 Hz TENS (TENS group) or mock TENS (mock group) during experimental procedure, respectively. They were required to express their degree of craving by visual analog scale before and after the presentation of a video-cue, and after TENS treatment, which lasted for 30 minutes. Heart rate and arterial blood pressure were simultaneously monitored in 56 cases, with 28 in each group. Results show that in mock group, video-cue induced a dramatic increase of craving score, which did not return to baseline in 150 minutes, whereas in the TENS group, 2 Hz TENS treatment produced a significant decrease of craving, reaching baseline in 90 minutes. Video-cue induced a significant increase of heart rate and systolic and diastolic blood pressure, which remained elevated for at least 60 minutes in the mock group; whereas in the TENS group, they returned to baseline immediately after the termination of TENS. These results indicate that the craving induced by a heroin-related cue can be immediately and significantly suppressed, and the cardiovascular activation totally abolished by a single-trial 2 Hz TENS for 30 minutes [source]