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PubMed1995

Heart rate increase and maximal heart rate during exercise as predictors of cardiovascular mortality: a 16-year follow-up study of 1960 healthy men.

BACKGROUND: Resting heart rate is directly associated and maximal exercise-induced heart rate inversely associated with cardiovascular mortality, and therefore their difference might contain prognostic information from both variables. The comparative long-term prognostic values of maximal exercise-induced heart rate and of the difference between it and resting heart rate were studied in apparently healthy middle-aged men. METHODS: Resting heart rate and maximal exercise-induced heart rate were measured, and their difference calculated, in 1960 apparently healthy men aged 40-59 years, and mortality was recorded over a period of 16 years. Conventional coronary risk factors were assessed at baseline. RESULTS: Both the difference between the two heart rates and the maximal exercise-induced heart rate were strongly, independently and inversely associated with cardiovascular mortality after adjustment for age, smoking, systolic blood pressure, lung function, glucose tolerance, serum cholesterol level, serum triglycerides level, physical fitness and exercise ECG findings. The adjusted relative risk of cardiovascular death in heart-rate difference quartiles 3 and 4 compared with that in quartile 1 (the lowest heart-rate difference quartile) was 0.54 (95% confidence interval 0.33-0.86; P = 0.009). The corresponding value for maximal exercise-induced heart rate was 0.56 (95% confidence interval 0.34-0.89; P = 0.018). Within the lowest heart-rate difference quartile, but not within the lowest maximal exercise-induced heart rate quartile, a further, strong, negative gradient in cardiovascular mortality was observed. In the high working capacity range, low heart-rate difference but not low maximal exercise-induced heart rate predicted very high cardiovascular disease mortality. Heart-rate difference and maximal exercise-induced heart rate were also inversely associated with non-cardiovascular disease mortality. CONCLUSIONS: Both heart-rate difference and maximal exercise-induced heart rate were strong, graded, long-term predictors of cardiovascular mortality among apparently healthy middle-aged men, independent of age, physical fitness and conventional coronary risk factors. However, low heart-rate difference was a better predictor than low maximal exercise-induced heart rate for recognizing individuals who were at particularly high risk of dying prematurely from cardiovascular diseases.

Adult↗
PubMed1982

Effects of relative metabolic rate and heart rate variation on the performance of flight attendants.

The main work of the cabin attendants in an actual flight in service for passengers. The effects of flight attendant duties in flight differ from the effects of the same tasks performed on the ground. In this study, the relative metabolic rate (RMR) and heart rate (HR) of cabin attendants in a cruising aircraft galley and cabin are compared with those of a crew working in a mock-up apparatus on the ground. The types of work tested are: (a) oshibori (steamed towel) service, (b) soft drink service, (c) setting meal tray, (d) putting casserole on tray, (e) meal tray service, (f) walking on aisle. The RMR at each type of work during flight is as indicated: (a) 1.07-2.10, (b) 1.08-1.54, (c) 1.37-1.82, (d) 2.57-3.50, (e) 2.11-3.10 and (f) 1.84. The range of HR was: (a) 105-120, (b) 90-110, (c) 90-120, (d) 100-130 and 100-140 beats/min. In most cases, the RMR and HR levels of work done in the mock-up were lower than those recorded in flight. These results suggest that the oxygen intake of work done in flight is greater than that on a mock-up. One of the reasons might be that the cabin barometric pressure (ca. 660 torr or cabin altitude ca. 1,500 m) or an aisle inclination of about 3 degrees caused a decrease in the efficiency of oxygen intake during flight.

Adult↗
PubMed1991

[The disappearance of the circadian rhythm of the heart rate in heart transplantation in the presence of acute rejection].

The present study is aimed to investigate the circadian rhythm (CR) of heart rate (HR) in acute rejecting and non-rejecting heart transplanted patients (HTP). The purpose is to provide evidence that an impairment in the HR CR may have a role in predicting episodes of acute rejection in HTP. The study was carried out on 32 Holter monitorings of 13 patients: 9 Holter monitorings were carried out during an episode of acute rejection documented by endomyocardial biopsy. Time data series were analyzed by Cosinor method in order to validate the occurrence of HR CR. The Cosinor analysis found a highly statistically significant HR CR in non-rejecting HTP. The occurrence of the HR CR was not statistically validated in acute rejecting HTP. These findings suggest that the lack of a periodic variability in the 24-hour HR pattern may be useful to diagnose acute heart rejection.

Acute Disease↗
PubMed1986

Observer ratings of perceived exertion in relation to self ratings and heart rate.

The results from a comparison made between observers' estimations of a bicycling subject's exertion and the self-raters' perceived exertion show that one can draw conclusions of an individual's exertion at physical work by using observer ratings. Six bicycling subjects (self-raters) cycled on a bicycle ergometer at six different power levels presented in random order. The estimations were made simultaneously by the observers and the self-rater during the last half minute at each power level. At the same time the self-rater's heart rate was registered. In accordance with earlier findings on physical work, the relation between heart rate and power level was linear. The estimations were made on a category-ratio scale as well as with magnitude estimation. The observers found the category-ratio scale easier to use and it seems as if the category-ratio scale is as reliable as magnitude estimation for these kinds of ratings.

Journal Article↗
PubMed2004

Influence of basic heart rate and sex on heart rate turbulence in healthy subjects.

Acceleration and deceleration of the heart rate after the occurrence of a ventricular premature complex is characterized as heart rate turbulence (HRT). Two parameters quantify heart rate turbulence: onset and slope. The physiological properties have not been clarified in a large cohort of persons yet. This study evaluated properties of HRT, and focused on the influence of basic heart rate and sex on HRT. Using a special protocol, 95 persons were studied prospectively. HRT and its physiological properties were determined in 95 persons using Holter ECGs. The authors found 24% with a turbulence onset 0% and 5% with a turbulence slope <2.5 ms/RRI. Mean heart rate during Holter differed significantly between women and men (745 vs 817 ms, P < 0.0001). A linear, weighted regression model revealed that an increased heart rate before a ventricular premature complex is associated with a decreased turbulence onset (P < 0.0001). Turbulence slope was attenuated by basic heart rate only in men (P = 0.0022). On the contrary, the study detected no influence of the basic heart rate on turbulence slope in women (P = 0.0015 for the comparison between women and men). Basic heart rate and sex show an influence on HRT and should be considered when using HRT for noninvasive risk stratification.

Adult↗
PubMedDate not supplied

Heart rate perception and the voluntary control of heart rate.

Heart rate perception was assessed in two sets of trials by having subjects set an intermittent visual pulse to match their heart rates. Just prior to matching subjects were required to either hyperventilate, hypoventilate or breathe normally to encourage a range of cardiac levels. Preceding each set of perception trials, bidirectional heart rate control was attempted. While one group of subjects received no exteroceptive feedback throughout, the other received continuous visual heart rate feedback on the second occasion. The data provided evidence of heart rate perception (as indexed by the correlation between interbeat and interpulse intervals) in a substantial number of instances. Further, perception was reliably associated with initial externally unaided cardiac control, although only in the increase direction. However, while the introduction of feedback tended to enhance cardiac control albeit only acceleratory control, no parallel effect was observed for perception. Analysis of interbeat and interpulse intervals in the different conditions of the matching task suggested that a real discrimination was probed by the procedure employed, but implied that respiratory cues afforded the basis for discrimination.

Adolescent↗
PubMed2002

[Features of heart rate, blood pressure, heart rate variability and cerebral blood flow during sequential head-up tilt test].

OBJECTIVE: To investigate the features of BP, HR, cerebral blood flow (CBF) and heart rate variation (HRV) during sequential head-up tilt table test (HUT) and provide information for methodology of testing tendency to syncope in pilots. METHOD: Sixteen healthy male were exposed to HUT +45 degrees 20 min, +60 degrees 20 min, and +75 degrees 20 min respectively with 5 min rests in between. CBFV, HR, HRV, BP were measured with transcranial doppler image (TCI), 12-Lead in phase ECG. RESULT: 1) As the tilt angle became larger, HR and DBP increased gradually (P<0.05), with SBP, PP and CBF Velocity (Vs,Vm,Vd) descended. There were significant differences among the various conditions. CV became smaller before +75 degrees, and then it began to increase. 2) Correlation between physiological indices and techno-indices were analyzed. At the point of 1 min, tilt angle was significantly positively correlated with SBP, DBP, MAP, Vd, and sdRR (P<0.01); At the point of 20 min, tilt angle was significantly positively correlated with HR and sdRR (P<0.01), but negatively correlated with SBP, PP, Vs and mRR (P<0.01), time of exposure was positively correlated with HP (P< 0.01), but negatively correlated with Vm, Vd, and mRR (P<0.01). 3) Correlation among physiological indices were also analyzed. HR were negatively correlated with SBP, Vs, Vm and Vd (P<0.01), SBP were significantly positively correlated with Vd, and mRR (P<0.01). Vs, Vm, Vd were significantly positively correlated with mRR and sdRR (P< 0.01). CONCLUSION: By investigating HR, BP, HRV and CBFV during of different angles, some advises for evaluating the tendency to syncope in pilots were put forward.

Adult↗
PubMed2005

Different methods of heart rate variability analysis reveal different correlations of heart rate variability spectrum with average heart rate.

UNLABELLED: Heart rate variability (HRV) spectrum can be calculated from the R-R or the sequence of instantaneous heart rates (IHRs). Because these signals are reciprocal, their use in the determination of the correlation of HRV with average HR may yield opposite results. AIM: The aim of this study is to reveal how HRV parameters correlate with HR depending on the kind of signal used and whether the normalization procedure or use of corrected signals affect the correlations. METHODS: Electrocardiographic recordings (512 beats) of 55 patients were considered in the analysis. RR and IHRs were calculated. Both signals were divided by their average values yielding the corrected RR and IHR. Heart rate variability spectra were estimated from these 4 kinds of signals. Total power (TP), low frequency (LF) and high frequency (HF) components, LF/HF ratio, and normalized values (ie, nLF, nHF) were calculated. RESULTS: Total power and LF estimated from RR correlated negatively with HR, but those calculated from IHR revealed a trend toward a positive correlation (respective correlation coefficients significantly differed, P < .01). The sign of correlation between HF and HR was the same regardless of the type of signal applied. The application of corrected signals made the results almost identical despite different signal origins (RR or IHR). The correlations of LF/HF, nLF, and nHF with HR were similar in all cases. CONCLUSIONS: The type of signal determines the sign of correlation among TP, LF, and HR. The parameters obtained from corrected signals, normalized quantities, and LF/HF reveal a consistent relationship with HR.

Electrocardiography↗
PubMed2005

Allometric estimation of metabolic rate from heart rate in penguins.

Studies of the relationship between heart rate (f(H)) and rate of oxygen consumption (V(.) (O(2))), which are then used to predict field metabolic rate, frequently fail to incorporate body mass as a predictive variable. This is a potentially important omission in the study of animals whose body mass fluctuates substantially during their annual cycle. In an attempt further to improve estimates of field metabolic rate from f(H), we re-evaluated data on M(b), f(H) and V(.) (O(2)) from previous studies of macaroni penguins (Eudyptes chrysolophus) and king penguins (Aptenodytes patagonicus) and derived a new relationship to integrate these three quantities. This relationship is at least as accurate and precise as previously determined relationships. We applied this same principle to published data on 11 of the 20 recognised penguin taxa to derive a relationship to predict V(.) (O(2)) from f(H) and M(b) in penguins of any species. This result has interesting implications in terms of reducing the logistical burden in studies of field metabolic rate.

Animals↗
PubMed1996

Effects of beta-blockade with bisoprolol on heart rate variability in advanced heart failure: analysis of scatterplots of R-R intervals at selected heart rates.

The effect of beta-blockade on heart-rate variability was assessed at different heart rates in 52 patients with heart failure included in the randomized, placebo-controlled, Cardiac Insufficiency Bisoprolol Study (CIBIS). Scatterplots of R-R intervals display beat-to-beat variability by plotting each R-R interval against the preceding interval. Scatterplot dispersion at different R-R intervals provides a measure of beat-to-beat heart-rate variability at different heart rates. A 24-hour Holter tape was performed at baseline and after 2 months of treatment with bisoprolol or matched placebo. Geometric measurements of scatterplots were used to determine beat-to-beat dispersion for different R-R intervals. Bisoprolol and placebo groups were well matched at base-line. After 2 months of treatment, bisoprolol significantly increased beat-to-beat variability at the longest R-R intervals (p < 0.05); however, there was no change in scatterplot dispersion at the shortest R-R intervals. This suggests that beta-blockade increases parasympathetic or decreases sympathetic tone or both in heart failure patients only at the slowest heart rates.

Adrenergic beta-Antagonists↗
PubMed1982

Computation of short-term fetal heart-rate variability from heart-rate waveforms.

Fetal heart-rate monitoring during labor is now routine in high-risk pregnancies. Beat-to-beat, or short-term variability in the heart rate has aroused considerable recent attention and several quantitative indices based on the fetal electrocardiogram have been proposed. These cannot be implemented on micro- or mini- computer-based labor-room systems without additional hardware because of the ECG processing involved. This paper describes a procedure for computing short-term variability from heart-rate waveforms. It correlates excellently with the above methods, but can be implemented on a microcomputer without special interfacing, since it uses only the slowly-varying heart-rate waveform.

Computers↗
PubMed2006

Heart rate variability and 24-hour minimum heart rate.

Heart rate variability (HRV) indices based on 24-hr electrocardiograph recordings have been used in clinical research studies to assess the aggregate activity of the autonomic nervous system. Although 24-hr HRV is generally considered noninvasive, use in research protocols typically involves considerable data collection and processing expenses and substantial participant burden. The purposes of this research methods evaluation were to describe the relationships between 24-hr minimum heart rate (HR) and several 24-hr time domain HRV indices (Ln SDNN, Ln SDANN, Ln SDNNIDX, Ln RMSSD, and Logit50) across several research data sets (normal women, normal men, children enrolled in a study of recurrent abdominal pain, women with irritable bowel syndrome, sudden cardiac arrest survivors, and heart failure patients) and to explore the possibility that 24-hr minimum HR might serve as a simpler alternative or adjunct to HRV measures in some situations. The correlations of global HRV measures (e.g., Ln SDNN, Ln SDANN) with 24-hr minimum HR were consistently larger (typical r approximately -.80) than with average HR (typical r approximately -.50). In repeated measurements, change in minimum HR was also correlated with change in general HRV (typical r approximately -.60). However, modest differentiation of minimum HR and HRV measures was noted in patients taking certain classes of cardiac medications (e.g., anti-arrhythmics, beta blockers). Twenty-four-hour minimum HR is correlated with general time domain HRV measures and might be useful as a simpler proxy, surrogate, or auxiliary variable in some clinical research applications, especially those in which participants are not receiving cardiac medications.

Abdominal Pain↗
PubMed1999

Effects of different insulin infusion rates on heart rate variability in lean and obese subjects.

The low-frequency to high-frequency ratio (LF/HF ratio) is an index of cardiac sympathovagal balance. We hypothesized that insulin might also stimulate the LF/HF ratio. Thus, 15 lean and 15 obese subjects were studied. Each subject underwent sequential hyperinsulinemic clamps (insulin infusion rate 0.50, 1, and 2 mU/kg x min) while the heart rate was recorded by the Holter technique continuously. Indirect calorimetry allowed determination of the respiratory quotient (Rq) and substrate oxidation. The leg blood flow (LBF), leg vascular resistance (LVR), and plasma norepinephrine concentration were also measured. In seven lean subjects, hyperinsulinemic clamps were repeated along with propranolol infusion (0.1 mg x kg(-1) as an intravenous bolus dose followed by continuous intravenous infusion of 0.5 mg x kg(-1) x min(-1) throughout the study). Lean subjects had better insulin action than obese subjects. Insulin infusion was associated with an increase of the deltaLF/HF ratio in both lean (P < .001 for time-dependent changes) and obese (P < .02 for time-dependent changes) subjects; however, the extent of insulin-mediated stimulation of the LF/HF ratio was greater in lean versus obese subjects. Insulin infusion did not significantly affect HF values in both groups. Independently of gender, body fat, changes in the plasma norepinephrine concentration, LBF, and LVR, the deltaLF/HF ratio at the end of the fastest insulin infusion (0.8 +/- 0.2 v 0.3 +/- 0.2, P < .04) was still greater in lean versus obese subjects. The deltaLF/HF ratio was also more stimulated during insulin versus insulin + propranolol infusion in lean subjects. In conclusion, insulin stimulates the LF/HF ratio in both lean and obese subjects and thus produces a shift in the cardiac autonomic nervous system activity toward sympathetic predominance.

Adrenergic beta-Antagonists↗
PubMed1981

Effects of noradrenergic and serotonergic neurons on blood pressure, heart rate and baroreceptor-heart rate reflex of the conscious rabbit.

The acute and chronic effects of intracisternal (i.c.) 6-hydroxydopamine (6-OHDA) and 5,6-dihydroxytryptamine (5,6-DHT) on mean arterial pressure (MAP), heart rate, and baroreceptor-heart rate reflex properties were examined in conscious rabbits. The reflex was studied by deriving MAP-heart period (HP, pulse interval) curves. The acute effects occurring over the first few hours were due to release of transmitter (noradrenaline after 6-OHDA; serotonin after 5,6-DHT) from specific synaptic sites; the changes on day 14 were due to destruction of specific neurons. Noradrenergic bulbar neurons facilitate vagal heart rate motoneurons and serotonergic neurons have an inhibitory effect. Noradrenergic bulbospinal pathways have a depressor effect on MAP and serotonergic bulbospinal activity increases MAP. These effects on heart rate and MAP were mediated through independent parallel pathways. The acute circulatory changes due to each neurotoxin also included a long latency pressor component, which was mediated through a pathway where a serotonergic neuron was in series with a noradrenergic neuron which sends fibers to a suprapontine pressor site. There were no chronic changes in resting MAP or heart rate, but chronic changes in reflex HP range and gain were opposite to the acute effects of transmitter release. These findings indicate that noradrenergic and serotonergic neurons normally participate in the central baroreceptor-heart rate reflex pathways of the intact animal.

Animals↗
PubMed1996

To what extent does a given heart rate correlate with following heart rates in the developing human fetus?

To quantitatively determine the extent to which a given heart rate correlates with the following heart rate(s) at any gestational age, we studied 181 uncomplicated human fetuses between 23 and 41 weeks gestation. A continuous 90-120 min observation was made for each case using external Doppler-ultrasound cardiotocography. For every individual fetal heart rate dataset, 'probability distribution matrices' were calculated with fetal heart rates (termed FHRs) at 1-beat/min (bpm) intervals, and the beat-to-beat(s) difference (termed DFHRn: 1 < or = n < or = 1000), also at 1-bpm intervals arranged in rows and columns, respectively, with probability in each element. Using 'piecewise linear regression', (1) the difference between the DFHR1 (n = 1) probability distribution matrix as the 'control' and a given DFHRn (n > or = 2) probability matrix as the 'variable', was analyzed to obtain the statistically critical point(s) (termed 'beat-delay' in beats) for each fetus, and (2) a scattergram of 'beat-delay' vs. gestational age-group, made from all fetuses studied, was analyzed to reveal any critical age(s) in gestation. One statistically significant point was evident at 28-29 weeks gestation. During the period prior to the critical point, a linear decrement in 'beat-delay' with 21 beats (mean) at 23-25 weeks to 11 beats at 28-29 weeks gestation was noted, suggesting that the conduction system-oriented heart beat gradually comes under functional control of the autonomic nervous system as well as under possible regulation by the maturating medulla oblongata. From the critical point, through to term, there was no significant change in 'beat-delay' ranging from 7-11 beats, thereby implying that the fetal heart rate becomes stabilized as a result of the control rendered by the more developed autonomic nervous system function. Whether or not brain function cephalad to the medulla oblongata actually participates in this phenomenon remains to be elucidated.

Embryonic and Fetal Development↗
PubMed2001

%HRmax target heart rate is dependent on heart rate performance curve deflection.

UNLABELLED: The percent of maximal heart rate (%HRmax) model is widely used to determine training intensities in healthy subjects and patients when prescribing training intensities in these groups of subjects. PURPOSE: The aim of the study was to investigate the influence of the time course of the heart rate performance curve (HRPC) on the accuracy of target training heart rate. METHODS: Sixty-two young healthy male subjects performed an incremental cycle ergometer exercise test until voluntary exhaustion. Subjects were then divided into four groups according to the time course of the HRPC. Groups were classified in regular HR response (kHR2 > 0.2), indifferent HR response (0 < kHR2 < 0.2), linear HR response (kHR2 = 0), and inverted HR response (kHR2 < 0). The first and the second lactate turn point (LTP1, LTP2) as well as the heart rate turn point (HRTP) were determined as submaximal markers of performance. Linear regression lines were calculated for HR in the three regions of energy supply defined by LTP1 and LTP2. RESULTS: HR at LTP1 and HRmax was not significantly different between all four groups. HR at LTP2 was dependent on the time course of the HRPC and was significantly lower (P < 0.05) as kHR2 decreased. Power output and blood lactate concentration at LTP1, LTP2 and maximal workload (Pmax) were not significantly different between the groups. CONCLUSION: From our data, we conclude that target training HR detected by means of the %HRmax method may be overestimated in cases where the HR response is not regular, as it was found in many of our subjects.

Adult↗