Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “HEART RATE”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 109 records · Page 6Linked to original sources
PubMedDate not supplied

Myocardial determinants in regulation of the heart rate.

Heart rate is a function of at least three factors located in the sinus node, including the pacemaker and the activity of the sympathetic and vagal pathways. Heart rate varies during breathing and exercising. The is far from being a purely academic question because, after myocardial infarction or in cardiac insufficiency, reduced heart rate variability (HRV) represents the most valuable prognostic factor. HRV is usually considered index of the sympathovagal balance and is explored using time domain analysis, such as spectral analysis. Nevertheless, methods such as the Fast Fourier Transformation are not applicable to small rodents which have an unstable heart rate with asymmetric oscillations. Nonlinear methods show chaotic behavior under some conditions. A time and frequency domain method of analysis, the Wigner-Villé Transform, has been proposed for the study of HRV in both humans and small rodents, as a compromise between linear and nonlinear methods. We developed a method to quantify both arrhythmias and HRV in unanesthetized rodents. Such a method allows study of the relationship between the physiological parameters and the myocardial phenotype. Ventricular premature beats are more frequent in 16-month-old spontaneously hypertensive rats than in age-matched controls. In addition, HRV is attenuated in spontaneously hypertensive rats, as in compensatory cardiac hypertrophy in humans, and such attenuation is considered a prognostic index. Converting enzyme inhibition reduces in parallel arterial hypertension, cardiac hypertrophy, and ventricular fibrosis; it prevents ventricular premature beats and normalizes heart rate variability. It can be demonstrated that the incidence of ventricular premature beats is linked to the myocardial phenotype in terms of both cardiac hypertrophy and fibrosis. The two factors act as independent variables. HRV is correlated with the incidence of arrhythmias, suggesting that the beneficial effects of converting enzyme inhibition are related to prevention of arrhythmias.

Animals↗
PubMed1992

Technical note: a noninvasive procedure for measuring goat heart rates.

Heart rates were obtained simultaneously from FM radio transmitters and heart rate monitors externally mounted on unanesthetized and unrestrained mixed-breed goats. Data from transmitters were highly correlated (r = .92, P < .0001) with data from monitors and the percentage difference in heart rates between the two devices was less than that observed between animals. Analyses also revealed that radio transmitters provided a reliable, repeatable, and valid method for the noninvasive measurement of goat heart rates.

Animals↗
PubMed2001

Spontaneous baroreflex modulation of heart rate and heart rate variability during orthostatic stress in tetraplegics and healthy subjects.

OBJECTIVE: This study was addressed to investigate the contribution of vagal and sympathetic mechanisms to the genesis of low-frequency (LF) oscillations of RR-interval. DESIGN: To this aim, we utilized the pathophysiological model of tetraplegics, who have intact vagal afferent and efferent pathways of the baroreceptor reflex arc but interrupted medullary-spinal sympathetic pathways. METHODS: We studied nine complete, traumatic, tetraplegics (C4-C7, TET) and 10 normally healthy subjects (NR) at rest and during physiological baroreceptors unloading induced by 70 degrees head-up tilt. Autoregressive power spectral analysis was used to investigate RR-interval and systolic arterial pressure (SAP) variabilities. Baroreflex modulation of sinus node was assessed by the spontaneous baroreflex sequences method. RESULTS: Both at-rest and during-tilt LF and high frequency (HF) components were detected in RR-interval of NR, whereas in TET only the HF component was observed in both conditions (with one exception). Baroreflex sensitivity (BRS) did not significantly differ between TET and NR at rest, and underwent a significant and similar decrease during tilt in both groups, being accompanied in NR by a significant increase in LF relative power. Spectral analysis of SAP provided results similar to RR-interval. Tilt also slowed the centre frequency of the LF components of RR-interval and SAP. CONCLUSIONS: During unperturbed physiological conditions, a change in efferent vagal activity to the heart from baroreflex stimulation by spontaneous arterial pressure changes, is unlikely to contribute on its own to the genesis of LF heart period oscillations in humans who lack the ability to modulate sympathetic nerve traffic to the heart. However, the possibility that a baroreflex modulation of LF oscillations require an intact sympathetic control should be carefully considered.

Adult↗
PubMed1991

Dynamics of heart rate.

Heart rate oscillates on several different time scales and has long-term variability in the form of 1/f noise. The physiological control of heart rate is briefly reviewed, and several typical patterns of heart rate variability, in health and sickness, are described. Considered briefly are some possible dynamical mechanisms for heart rate variability.

Journal Article↗
PubMed1984

A theoretical right atrial pressure feedback heart rate control system to restore physiologic control to the rate-limited heart.

Physiologic control of heart rate may be limited by sinus node injury or congenital conduction defects. Control theory may be applied to restore physiologic rate control. Mean right atrial pressure is a likely candidate for incorporation into an artificial control system because of its: (1) stability at rest; (2) tendency to increase during exertion in the rate-limited heart; (3) ability to decrease with increasing heart rate in the rate-limited heart; and (4) accessibility for measurement via the transvenous route. A theoretical right atrial pressure feedback heart rate control system is presented; applications to physiologic pacing of patients with sick sinus syndrome, rate control of the transplanted heart, and pump frequency control of the total artificial heart are discussed.

Arrhythmias, Cardiac↗
PubMed2001

Independent association between plasma leptin levels and heart rate in heart transplant recipients.

BACKGROUND: Leptin, the protein product of the ob gene, has been linked to a faster heart rate in animal and human studies. The interaction between leptin and heart rate in the denervated heart is not known. Therefore, we studied the relationship between plasma leptin levels and heart rate in heart transplant recipients. METHODS AND RESULTS: We studied 32 male patients (mean age, 56.5+/-9.3 years; range, 41 to 74 years) after orthotopic heart transplantation. All subjects underwent a physical examination, anthropometric measurements, blood chemistry analysis, and office blood pressure measurements. A blood sample was collected from each subject while fasting. In univariate analysis, heart rate was related to leptin levels (r=0.47, P=0.007) but heart rate was not related to systolic or diastolic blood pressure, mean arterial pressure, body mass index, or catecholamines. Leptin levels were only strongly associated with heart rate and body mass index (r=0.73, P<0.0001). In multivariate analysis, heart rate was independently and positively associated with leptin levels (F=2.61, P=0.017). We also observed a strong, independent association between leptin levels and body mass index (F=5.8, P<0.00001). CONCLUSIONS: We show an independent association between leptin levels and heart rate in heart transplant recipients. We speculate that this may be due, in part, to a direct effect of leptin on heart rate, conceivably mediated through cardiac leptin receptors.

Adult↗
PubMed1993

Heart rate, ischaemic heart disease, and sudden cardiac death in middle-aged British men.

OBJECTIVE: To examine the relation between resting heart rate and new major ischaemic heart disease events in middle aged men with and without pre-existing ischaemic heart disease. DESIGN: Prospective study of a cohort of men with eight years follow up for cardiovascular morbidity and mortality for all men. SETTING: General practices in 24 British towns (the British Regional Heart study). SUBJECTS: 7735 men aged 40-59 years drawn at random from the age-sex registers of one general practice in each town. MAIN OUTCOME MEASURES: Major ischaemic heart disease events such as sudden cardiac death, other deaths attributed to ischaemic heart disease, and non-fatal myocardial infarction. RESULTS: During the follow up period of eight years, 488 men had a major ischaemic heart disease event (217 fatal and 271 non-fatal). Of these, 117 were classified as sudden cardiac death (death within one hour of the start of symptoms). The relation between heart rate and risk of all major ischaemic heart disease events, ischaemic heart disease deaths, and sudden cardiac death was examined separately in men with and without pre-existing ischaemic heart disease. In men with no evidence of ischaemic heart disease, there was a strong positive association between resting heart rate and age adjusted rates of all major ischaemic heart disease events (fatal and non-fatal), ischaemic heart disease deaths, and sudden cardiac death. This association remained significant even after adjustment for age, systolic blood pressure, blood cholesterol, smoking, social class, heavy drinking, and physical activity, with particularly high risk in those with heart rate > or = 90 beats/min. The increased risk seen in those with increased heart rate was largely due to a significantly increased risk of sudden cardiac death, which was five times higher than in those with heart rate < 60 beats/min. The effect of heart rate on sudden cardiac death was present irrespective of blood pressure or smoking state. In men with pre-existing ischaemic heart disease a positive association was seen between raised heart rate and risk of all major ischaemic heart disease events, ischaemic heart disease death, and sudden cardiac death, but the effect was less noticeable than in men without pre-existing ischaemic heart disease. CONCLUSION: In this study of middle aged British men increased heart rate > or = 90 beats/min) is a risk factor for fatal ischaemic heart disease events but particularly for sudden cardiac death. The effect is not dependent on the presence of other established coronary risk factors and is most clearly seen in men free of pre-existing ischaemic heart disease at initial examination.

Adult↗
PubMed1997

Heart rate and heart-rate variability in patients with acute coronary heart disease classified on Bortner's scale as type A and type B.

We investigated heart rate and heart-rate variability in 82 patients, 60 men and 22 women (M = 54 yr., SD = 9) with acute coronary heart disease and scores on Bortner's scale at hospital admission and discharge. 48 patients were classified by their scores on Bortner's scale as Type A and 34 as Type B. Patients with acute coronary heart disease classified as Type A had a significantly lower mean heart rate than patients with acute coronary heart disease classified as Type B during the day at hospital admission and discharge and during the night at hospital discharge. Mean heart-rate variability was also significantly higher in the patients with acute coronary heart disease classified as Type A than in the patients with acute coronary heart disease classified as Type B during the day at hospital admission and discharge. The differences between two groups on the average heart rate and heart-rate variability were not significant during the night at hospital admission. In our study the patients with acute coronary heart disease classified by scores on Bortner's scale as Type A had higher vagal tone and more favorable sympathovagal balance than patients classified as Type B. This finding may have implications for the treatment of patients with acute coronary heart disease and may suggest some explanation about the protective effect of Type A behavior also.

Adult↗
PubMed1980

Fat cell number, resting metabolic rate, mean heart rate, and insulin elevation while seeing and smelling food as predictors of slimming.

The explanatory value of total fat cell number, resting metabolic rate, mean heart rate during sleep, and peripheral insulin while seeing and smelling food were examined in relation to weight reduction in 19 obese women on a 1100-kcal/day diet. The insulin response while seeing and smelling food was expressed as the insulin area (mU x min x 1(-1)) over the baseline level. Food was presented in front of the patient for 5 min. Insulin was determined in short intervals 20 min before and 20 min after start of food presentation. Fat cell number, resting metabolic rate, and mean heart rate during sleep were determined with standard techniques. All patients went through a period of weight loss, a plateau phase, and a period of weight regain. Body weight, fat cell number, resting metabolic rate, and/or heart rate correlated significantly with degree and rate of weight loss, duration of plateau phase, and rate of regain. In multiple regression analysis fat cell number and resting metabolic rate explained 81% of the variance for weight loss, 66% for rate of regain, and 29% for duration. For duration, only fat cell number contributed significantly. The variance of rate of weight loss was explained up to 49% by metabolic rate and insulin response while seeing and smelling food. The possibility of predicting weight reduction to a certain target weight is of great practical importance since the patients can obtain a realistic goal for their efforts to reduce body weight. Hopefully systematic investigations of factors associated with the inability of obese subjects to maintain weight reduction will improve treatment in the future.

Adipose Tissue↗
PubMed2002

QTL associated with blood pressure, heart rate, and heart weight in CBA/CaJ and BALB/cJ mice.

To better understand the genetic basis of essential hypertension, we conducted a quantitative trait locus (QTL) analysis of a population of 207 (BALB/cJ x CBA/CaJ) F(2) male mice to identify genomic regions that regulate blood pressure, heart rate, and heart weight. We identified two loci, Bpq6 (blood pressure quantitative locus 6) on chromosome 15 (Chr 15; peak, 16 cM; 95% confidence interval, 0-25 cM) and Bpq7 on Chr 7 (peak, 42 cM; 95% confidence interval, 35-50 cM) that were significantly associated with blood pressure. We also identified two loci, Hrq1 (heart rate quantitative locus 1) and Hrq2, on D2Mit304 (peak, 72 cM; 95% confidence interval 60-80 cM) and D15Mit184 (peak, 25 cM; 95% confidence interval 20-35 cM), respectively, that were significantly associated with heart rate. A significant gene-gene interaction for heart rate was found between Hrq1 and D1Mit10 (peak, 57 cM; 95% confidence interval, 45-75 cM); the latter QTL was named Hrq3. We identified a significant locus for heart weight, Hwq1 (heart weight quantitative locus 1), at D14Mit67 (peak, 38 cM; 95% confidence interval, 20-43 cM). Identification of the genes for these QTL should lead to a better understanding of the causes of essential hypertension.

Animals↗
PubMed2001

Electrocardiography, heart rates, and heart weights of free-living birds.

To examine the waveforms of electrocardiograms, cardiac rhythm, heart rates at rest and during excitement, and the rate of increase of heart rate, electrocardiograms were recorded with standard bipolar limb leads from 79 free-living birds, including 19 species. The heart weights and heart-to-body weight ratios were obtained from an additional 96 free-living birds, including 20 species. In the majority of the electrocardiograms, lead I was of low amplitudes for all waves except the P wave, and leads II and II were very similar to each other with a predominant S wave and a very short or elevated ST segment. The P wave was often superimposed on the T wave when the heart rate increased to 330 beats/min. Four types of arrhythmia were observed in 50 of the 79 birds (63.3%): 48 sinus arrhythmias, four sinus arrests, two atrial premature contractions, and one ventricular premature contraction. The resting heart rate was negatively associated with the rate of increase, suggesting that a bird with a low resting rate might be able to maintain a greater capacity to increase its heart rate than one with a high resting rate. A negative correlation on a bilogarithmic scale was obtained between the heart weight and the resting heart rate, indicating that a bird with a high heart weight had lower resting heart rate than a bird with a low heart weight. When the heart-to-body weight ratios of free-living birds were compared according to their motility, the ratios of more active birds were greater than those of less active ones.

Animals↗