The epidemiology of resting heart rate in a national sample of men and women: associations with hypertension, coronary heart disease, blood pressure, and other cardiovascular risk factors

Exploring the contribution of inter-individual factors to the development of physiological heat strain in older adults exposed to simulated indoor overheating

Older adults are at elevated risk of heat-related mortality due to age-associated declines in thermoregulatory and cardiovascular function. However, the inter-individual factors that exacerbate physiological heat strain during heat exposure remain unclear, making it challenging to identify more heat-vulnerable subgroups. We therefore explored factors contributing to inter-individual variability in physiological responses of older adults exposed to simulated hot weather. Thirty-seven older adults (61-80 years, 16 females) rested for 8 h in 31 and 36 °C (45% relative humidity). Core (rectal) temperature, heart rate (HR), HR variability, mean arterial pressure (MAP), and cardiac autonomic responses to standing were measured at baseline and end-exposure. Bootstrapped least absolute shrinkage and selection operator regression was used to evaluate whether variation in these responses was related to type 2 diabetes (T2D, n = 10), hypertension (n = 18), age, sex, body morphology, habitual physical activity levels, and/or heat-acclimatization. T2D was identified as a predictor of end-exposure HR (with vs. without: 13 beats/min (bootstrap 95% confidence interval: 6, 23)), seated MAP (-7 mmHg (-18, 1)), and the systolic pressure response to standing (20 mmHg (4, 36)). HR was also influenced by sex (female vs. male: 8 beats/min (1, 16)). No other predictors were identified. The inter-individual factors explored did not meaningfully contribute to the variation in body temperature responses in older adults exposed to simulated indoor overheating. By contrast, cardiovascular responses were exacerbated in females and individuals with T2D. These findings improve understanding of how inter-individual differences contribute to heat-induced physiological strain in older persons.

The aorta in humans and African great apes, and cardiac output and metabolic levels in human evolution

Humans have a larger energy budget than great apes, allowing the combination of the metabolically expensive traits that define our life history. This budget is ultimately related to the cardiac output, the product of the blood pumped from the ventricle and the number of heart beats per minute, a measure of the blood available for the whole organism physiological activity. To show the relationship between cardiac output and energy expenditure in hominid evolution, we study a surrogate measure of cardiac output, the aortic root diameter, in humans and great apes. When compared to gorillas and chimpanzees, humans present an increased body mass adjusted aortic root diameter. We also use data from the literature to show that over the human lifespan, cardiac output and total energy expenditure follow almost identical trajectories, with a marked increase during the period of brain growth, and a plateau during most of the adult life. The limited variation of adjusted cardiac output with sex, age and physical activity supports the compensation model of energy expenditure in humans. Finally, we present a first study of cardiac output in the skeleton through the study of the aortic impression in the vertebral bodies of the spine. It is absent in great apes, and present in humans and Neanderthals, large-brained hominins with an extended life cycle. An increased adjusted cardiac output, underlying higher total energy expenditure, would have been a key process in human evolution.

Reference equations for the six-minute walking distance in obese Chinese subjects more than 40 years old

BACKGROUND

Studies have shown that the reference equations for the six-minute walking distance (6MWD), which were mainly derived from healthy, normal-weight people, are not suitable for individuals with obesity. The main purpose of this study was to establish reference equations for the 6MWD in obese Chinese subjects.

METHODS

In our study, a total of 214 individuals with obesity performed the six-minute walking tests (6MWTs) according to the American thoracic society (ATS) guidelines, and the longer 6MWD was used for further analysis. The reference equations for the 6MWD were developed using stepwise multiple regression analysis. The newly established equations for the 6MWD were compared to the existing prediction equations.

RESULTS

The mean 6MWD for the cohort was 523 ± 56 m. We found that the reliability of two 6MWTs was good. Age and BMI were identified as independent factors, and explained 31% and 27% of the variance in the 6MWD for the male and female participants, respectively. Thus, the reference equations reported in the previous studies did not accurately predict the 6MWD in our subjects.

CONCLUSION

Our study was the first to describe the 6MWD in obese Chinese subjects and to propose new predictive equations. These established equations can improve the assessment of the health of obese Chinese patients whose exercise capacity is affected by the disease.

LEVEL OF EVIDENCE

III, Cohort study.

Heart Rate and Mortality After Resuscitation in Patients With Out-of-Hospital Cardiac Arrest - Insights From the SOS-KANTO Registry

BACKGROUND

Heart rate (HR) predicts outcomes in patients with acute coronary syndrome (ACS), whereas the impact of HR on outcomes after out-of-hospital cardiac arrest (OHCA) remains unclear. This study aimed to investigate the impact of HR after resuscitation on outcomes after OHCA and whether the impact differs with OHCA etiology.

METHODS AND RESULTS

Of 16,452 patients suffering from OHCA, this study analyzed 741 adults for whom HR after resuscitation was recorded by 12-lead electrocardiogram upon hospital arrival. Etiology of OHCA was categorized into 3 groups: ACS, non-ACS, and non-cardiac. Patients in each etiology group were further divided into tachycardia (>100 beats/min) and non-tachycardia (≤100 beats/min). The impact of HR on outcomes was evaluated in each group. Among the 741 patients, the mean age was 67.6 years and 497 (67.1%) patients were male. The primary outcome - 3-month all-cause mortality - was observed in 55.8% of patients. Tachycardia after resuscitation in patients with ACS was significantly associated with higher all-cause mortality at 3 months (P=0.002), but there was no significant association between tachycardia and mortality in non-ACS and non-cardiac etiology patients. In a multivariate analysis model, the incidence of tachycardia after resuscitation independently predicted higher 3-month all-cause mortality in OHCA patients with ACS (hazard ratio: 2.17 [95% confidence interval: 1.05-4.48], P=0.04).

CONCLUSIONS

Increased HR after resuscitation was associated with higher mortality only in patients with ACS.

Two-minute walk distance reference equations for middle-aged and elderly Chinese individuals with obesity

Background and objective

While the six-minute walk test (6MWT) is often used to assess exercise capacity, the less well-known two-minute walk test (2MWT) is more feasible for some patients. In previous studies, we developed reference equations for the two-minute walk distance (2MWD) for healthy Chinese adults. However, our study did not recruit people with obesity, and the reference equations did not apply to participants with a body mass index (BMI) > 30 kg/m². The main objective of this study was to establish reference equations for the 2MWD among middle-aged and elderly Chinese individuals with obesity.

Methods

A total of 295 individuals were recruited. The participants underwent two 2MWTs, with the longer of the two 2MWDs used for further analyses. The reference equations for the 2MWD were developed using stepwise multiple regression analysis. The newly established equations for the 2MWD were then compared with the existing equations.

Results

The mean 2MWD of the participants was 176±20 m. Age and BMI were identified as independent factors that influenced the 2MWD and explained 28% and 32% of the variance in walking distance for the male and female groups, respectively. The reference equations for the 2MWD were as follows:

Conclusion

This study resulted in the development of reference equations for predicting 2MWD among middle-aged and elderly Chinese people with obesity. These equations will be a clinically valuable tool for evaluating functional capacity, determining prognoses and monitoring treatment in middle-aged and elderly Chinese people with obesity.

Associations of Infant Feeding with Body Composition and Cardiometabolic Health in Young Female University Students

Background:

We assessed the association of infant feeding with body composition and cardiometabolic health at 20 years in a setting where infant feeding is not associated with socioeconomic status.

Materials and methods:

Body size trajectory since birth, current body composition measured using whole-body dual-energy X-ray absorptiometry, and a broad range of cardiometabolic risk factors were compared cross-sectionally among young female university students who were ever breastfed (n = 158, 120 exclusively, and 38 mainly), mixed fed (n = 124), and formula fed (n = 15, 10 mainly, and 5 exclusively)

Results:

Compared with breastfed and mixed fed women, formula fed women had higher serum total and low-density lipoprotein (LDL) cholesterol although fat mass, fat distribution, fasting glucose, and insulin and high-density lipoprotein cholesterol did not differ. In addition, resting heart rates were higher in formula fed women compared with the other two groups of women although systolic and diastolic blood pressure did not differ. Further, formula fed women had higher adiponectin while serum leptin did not differ. There was no difference in birthweight, weight and height in childhood and adolescence, and glucose tolerance. On multivariate logistic regression analysis, formula feeding was associated with resting heart rates (odds ratio [OR]: 1.06, confidence interval [95% CI]; 1.01–1.12, p = 0.01) and adiponectin (OR: 1.3, 95% CI; 1.1–1.5, p < 0.001) independently of serum total and LDL cholesterol.

Conclusions:

Breastfeeding may be associated with favorable lipid profile and autonomic nervous function in young adults through mechanisms unrelated to adiposity, implicating potential long-term benefits of breastfeeding for cardiovascular health. Higher adiponectin in nonbreastfed women warrants further studies.

The Association Between Heart Rate and Glycemic Status in the National Health and Nutrition Examination Surveys

CONTEXT

Evidence suggests that heart rate (HR) is a prognostic factor for cardiovascular disease (CVD), for which persons with diabetes are at increased risk.

OBJECTIVE

The objective of this article is to determine the association between HR and glycemic status in a nationally representative sample of US adults, and, among adults with diagnosed diabetes, the association between HR and hemoglobin A1c (HbA1c) level.

DESIGN

A cross-sectional study was conducted.

SETTING

The setting of this study is the National Health and Nutrition Examination Surveys, 2011 to 2016.

PARTICIPANTS

US general adult (age ≥ 20 years) population who had information on glycemic status based on self-report, HbA1c, and fasting plasma glucose (N = 8562).

INTERVENTION

There was no intervention.

MAIN OUTCOME MEASURE

The main outcome measure of this study was mean HR (beats per minute).

RESULTS

After adjustment for examination time, age, other demographic characteristics, health insurance, health behaviors, body mass index, CVD and kidney disease, and taking antihypertensive medications, mean HR was significantly higher for those with diagnosed (75 bpm), undiagnosed diabetes (75 bpm), and prediabetes (73 bpm) compared to those with normoglycemia (71 bpm, P < .05 for all); this association was robust both for men and women. Mean HR increased with increasing HbA1c level among individuals with diagnosed diabetes independent of other risk factors (HbA1c < 7.0% [< 53 mmol/mol], 73 bpm vs A1c ≥ 11.0% [≥ 97mmol/mol], 79 bpm, P < .001); this association was most pronounced for women.

CONCLUSIONS

Adjusted mean HR was higher among individuals with diabetes and increased glycemia, which may reflect underlying autonomic and/or myocardial dysfunction among those with diabetes.

Exercise capacity and body mass index - important predictors of change in resting heart rate

BACKGROUND

Resting heart rate (RHR) is an obtainable, inexpensive, non-invasive test, readily available on any medical document. RHR has been established as a risk factor for cardiovascular morbidity, is related to other cardiovascular risk factors, and may possibly predict them. Change in RHR over time (∆RHR) has been found to be a potential predictor of mortality.

METHODS

In this prospective study, RHR and ∆RHR were evaluated at baseline and over a period of 2.9 years during routine check-ups in 6683 subjects without known cardiovascular disease from the TAMCIS: Tel-Aviv Medical Center Inflammation Survey. Multiple linear regression analysis with three models was used to examine ∆RHR. The first model accounted for possible confounders by adjusting for age, sex and body mass index (BMI). The 2nd model included smoking status, baseline RHR, diastolic blood pressure (BP), dyslipidemia, high-density lipoprotein (HDL) and metabolic equivalents of task (MET), and in the last model the change in MET and change in BMI were added.

RESULTS

RHR decreased with age, even after adjustment for sex, BMI and MET. The mean change in RHR was - 1.1 beats/min between two consecutive visits, in both men and women. This ∆RHR was strongly correlated with baseline RHR, age, initial MET, and change occurring in MET and BMI (P < 0.001).

CONCLUSIONS

Our results highlight the need for examining individual patients' ∆RHR. Reinforcing that a positive ∆RHR is an indicator of poor adherence to a healthy lifestyle.

Impact of changes in heart rate with age on all-cause death and cardiovascular events in 50-year-old men from the general population

Background

Resting heart rate (RHR), a known cardiovascular risk factor, changes with age. However, little is known about the association between changes in RHR and the risk of cardiovascular events. The purpose of this study was therefore to assess the impact of RHR at baseline, and the change in RHR over time, on the risk of all-cause death and cardiovascular events.

Design

A random population sample of men born in 1943 who were living in Gothenburg, Sweden was prospectively followed for a 21-year period.

Methods

Participants were examined three times: first in 1993 and then re-examined in 2003 and 2014. At each visit, a clinical examination, an ECG and laboratory analyses were performed. Change in RHR between 1993 and 2003 was defined as a decrease if RHR decreased by 5 beats per minute (bpm), an increase if RHR increased by 5 bpm or stable if the RHR change was <4bpm).

Results

Participants with a baseline RHR of >75 bpm in 1993 had about a twofold higher risk of all-cause death (HR 2.3, CI 1.2 to 4.7, p=0.018), cardiovascular disease (CVD) (HR 1.8, CI 1.1 to 3.0, p=0.014) and coronary heart disease (CHD) (HR 2.2, CI 1.1 to 4.5, p=0.025) compared with those with <55 bpm in 1993. Participants with a stable RHR between 1993 and 2003 had a 44% decreased risk of CVD (HR 0.56, CI 0.35 to 0.87, p=0.011) compared with participants with an increasing RHR. Furthermore, every beat increase in heart rate from 1993 was associated with a 3% higher risk for all-cause death, 1% higher risk for CVD and 2% higher risk for CHD.

Conclusion

High RHR was associated with an increased risk of death and cardiovascular events in men from the general population. Moreover, individuals with an increase in RHR between 50 and 60 years of age had worse outcome.

Elevated resting heart rate is associated with the severity of coronary artery disease in non-treated patients who underwent coronary angiography: potential role of lipoprotein subfractions

OBJECTIVE

To assess the association between resting heart rate (RHR) and lipoprotein subfractions to provide potential evidence for the relationship between RHR and severity of CAD.

METHODS

A total of 1119 consecutive non-treated subjects scheduled for coronary angiography were enrolled. High-density lipoprotein (HDL) and low-density lipoprotein (LDL) separation were performed by Lipoprint System. The link of RHR with lipoprotein subfractions was assessed.

RESULTS

Increased RHR was significantly associated with higher triglyceride, total cholesterol, non-HDL-cholesterol, and apolipoprotein B (all p < .01). Furthermore, data indicated that higher RHR was related to more severe CAD (all p < .05). In the following linear regression models, we observed that higher RHR (HRh bpm) was significantly associated with lower large HDL (β = -0.073, p = .024) and higher small LDL subfraction (β = 0.103, p = .005) after adjusting for potential confounders.

CONCLUSIONS

Increased RHR was associated with more severe CAD, which may be partly due to the significant relation to atherogenic lipoprotein subfractions.

Reference equations for the six-minute walk distance in the healthy Chinese population aged 18-59 years

BACKGROUND

The six-minute walk test (6MWT) is a safe, simple, inexpensive tool for evaluating the functional exercise capacity of patients with chronic respiratory disease. However, there is a lack of standard reference equations for the six-minute walk distance (6MWD) in the healthy Chinese population aged 18-59 years.

AIMS

The purposes of the present study were as follows: 1) to measure the anthropometric data and walking distance of a sample of healthy Chinese Han people aged 18-59 years; 2) to construct reference equations for the 6MWD; 3) to compare the measured 6MWD with previously published equations.

METHOD

The anthropometric data, demographic information, lung function, and walking distance of Chinese adults aged 18-59 years were prospectively measured using a standardized protocol. We obtained verbal consent from all the subjects before the test, and the study design was approved by the ethics committee of Wenzhou People's Hospital. The 6MWT was performed twice, and the longer distance was used for further analysis.

RESULTS

A total of 643 subjects (319 females and 324 males) completed the 6MWT, and average walking distance was 601.6±55.51 m. The walking distance was compared between females and males (578±49.85 m vs. 623±52.53 m; p < 0.0001) and between physically active subjects and sedentary subjects (609.3±56.17 m vs. 592±53.23 m; p < 0.0001). Pearson's correlation indicated that the 6MWD was significantly correlated with various demographic and the 6MWT variables, such as age, height, weight, body mass index (BMI), heart rate after the test and the difference in the heart rate before and after the test. Stepwise multiple regression analysis showed that age and height were independent predictors associated with the 6MWD. The reference equations from white, Canadian and Chilean populations tended to overestimate the walking distance in our subjects, while Brazilian and Arabian equations tended to underestimate the walking distance. There was no significant difference in the walking distance between Korean reference equations and the results of the current study.

CONCLUSION

In summary, age and height were the most significant predictors of the 6MWD, and regression equations could explain approximately 34% and 28% of the distance variance in the female and male groups, respectively.

Association of resting heart rate and hypertension stages on all-cause and cardiovascular mortality among elderly Koreans: the Kangwha Cohort Study

Background

Elevated resting heart rate and hypertension independently increase the risk of mortality. However, their combined effect on mortality in stages of hypertension according to updated clinical guidelines among elderly population is unclear.

Methods

We followed a cohort of 6100 residents (2600 males and 3500 females) of Kangwha County, Korea, ranging from 55 to 99 year-olds as of March 1985, for all-cause and cardiovascular mortality for 20.8 years until December 31, 2005. Mortality data were collected through telephone calls and visits (to 1991), and were confirmed by death record matching with the National Statistical Office (1992−2005). Hazard ratios were calculated for all-cause and cardiovascular mortality by resting heart rate and hypertension defined by Eighth Joint National Committee criteria using the Cox proportional hazard model after controlling for confounding factors.

Results

The hazard ratios associated with resting heart rate > 80 beats/min were higher in hypertensive men compared with normotensives with heart rate of 61–79 beats/min, with hazard ratios values of 1.43 (95% CI: 1.00−1.92) on all-cause mortality for prehypertension, 3.01 (95% CI: 1.07–8.28) on cardiovascular mortality for prehypertension, and 8.34 (95% CI: 2.52−28.19) for stage 2 hypertension. Increased risk (HR: 3.54, 95% CI: 1.16–9.21) was observed among those with both a resting heart rate ≥ 80 beats/min and prehypertension on cardiovascular mortality in women.

Conclusions

Individuals with coexisting elevated resting heart rate and hypertension, even in prehypertension, have a greater risk for all-cause and cardiovascular mortality compared to those with elevated resting heart rate or hypertension alone. These findings suggest that elevated resting heart rate should not be regarded as a less serious risk factor in elderly hypertensive patients.

Effect of postural changes on cardiovascular parameters across gender

INTRODUCTION

We investigated the effect of postural changes on various cardiovascular parameters across gender. Twenty-eight healthy subjects (16 male, 12 female) were observed at rest (supine) and subjected to 3 interventions; head-down tilt (HDT), HDT with lower body negative pressure (HDT+ LBNP at -30 mm Hg), and head-up tilt (HUT), each for 10 minutes separated by a 10 minutes recovery period.

METHODS

Measurements were recorded for heart rate (HR), standard deviation of the normal-to-normal intervals, root mean square of successive differences between the normal-to-normal intervals, heart rate variability-low frequency (LFRRI), heart rate variability-high frequency (HFRRI), low frequency/high frequency ratio (LFRRI/HFRRI), systolic blood pressure (SBP), mean arterial pressure (MAP), diastolic blood pressure (DBP), total peripheral resistance index (TPRI), stroke index (SI), cardiac index (CI), index of contractility (IC), left ventricular work index, and left ventricular ejection time.

RESULTS

Across all cardiovascular parameters, there was a significant main effect of the intervention applied but there was no significant main effect of gender across all parameters.

CONCLUSIONS

The results suggest that there are no specific gender differences in regards to the measured variables under the conditions of this study. Furthermore, these results suggest that in healthy subjects, there appears to be evidence that LBNP partially elicits similar cardiovascular responses to HUT, which supports the use of LBNP as an intervention to counteract the effects of central hypovolemia.

Sexual dimorphism in the osmopressor response following water ingestion

Compared with men, women exhibit a greater magnitude of increase in resting blood pressure after drinking a single water bolus of 500 ml. Accordingly, our study provides direct evidence of sexual dimorphism in the haemodynamic response to water intake.

There is conflicting evidence as to whether water drinking elicits a pressor response in healthy young adults. The inclusion of a variable number of women may have contributed to the discrepancies found in past research. Thus, we aimed at exploring whether the osmopressor response follows a sexually dimorphic pattern. In a randomized fashion, 31 healthy adults (16 men; 15 women, aged 18–40 years) ingested 50 and 500 ml of water before completing a resting protocol on two separate days. Arterial blood pressure, heart rate and spectral heart rate variability were measured in the seated position at pre- and post-25 min of water ingestion. Women responded to 500 ml of water with a greater proportion of change in diastolic and mean arterial pressure (MAP) (P<0.05). Conversely, the percent change in systolic blood pressure (SBP) and heart rate was not different between sexes after 500 ml of water. Overall, women demonstrated lower blood pressure, but higher resting heart rate compared with men (P<0.05). In contrast, heart rate variability was similar between sexes before and after ingesting either volume of water. There was a bradycardic effect of water and, irrespectively of sex; this was accompanied by increased high frequency power (HF) (P<0.05). We conclude that women display a greater magnitude of pressor response than men post-water ingestion. Accordingly, we provide direct evidence of sexual dimorphism in the haemodynamic response to water intake in young healthy adults.

Women and heart disease, the underrecognized burden: sex differences, biases, and unmet clinical and research challenges

For many years the significance of heart disease in women was vastly underappreciated, and women were significantly underrepresented in cardiovascular clinical research. We now know that cardiovascular disease is the leading cause of death for women. Women and men share many similarities in the pathophysiology and manifestations of heart disease. However, as research advances with the continued inclusion of more women, knowledge about gender differences between the female and male heart, both on a physiological and pathophysiological basis, grows. These differences can be found in all domains of cardiovascular health and disease, including heart rhythm, heart failure, coronary disease and valvular disease. Further understanding of gender differences in the heart is crucial for advancing our ability to maintain a healthy population and identify and treat heart disease in both women and men. Specific examples within the spectrum of heart disease will be discussed in this review paper, and areas for further research will be proposed.

Association of exercise heart rate response and incidence of hypertension in men

OBJECTIVE

To examine the association of heart rate (HR) responses at rest, during exercise, and after exercise with incident hypertension (HTN) in men.

PARTICIPANTS AND METHODS

A total of 10,418 healthy normotensive men without abnormalities on electrocardiography or a history of myocardial infarction, stroke, cancer, or diabetes underwent a maximal exercise test and were followed up for incidence of HTN. Heart rate reserve was defined as the maximal HR minus resting HR. Heart rate recovery was defined as HR 5 minutes after the exercise test.

RESULTS

During a mean follow-up of 6 years, there were 2831 cases of HTN. Compared with men who had lower HR reserve, the risk of incident HTN was significantly lower for men with higher HR reserve (hazard ratio, 0.84; 95% CI, 0.74-0.95 for the highest quartile vs the lowest quartile of HR reserve; P=.002) when adjusted for age, baseline examination year, smoking, heavy drinking, body mass index, resting blood pressure, cholesterol and glucose levels, and cardiorespiratory fitness. Compared with men who had higher HR recovery, the risk of incident HTN was significantly lower for men with lower HR recovery (hazard ratio, 0.90; 95% CI, 0.80-0.99 for quartile 3 vs highest quartile; P=.04) after adjusting for the aforementioned confounders. However, the overall linear trend for HR recovery was not significant (P=.26).

CONCLUSION

The risk of HTN decreased in men with higher HR reserve. Therefore, HR reserve may be considered as a useful exercise parameter for predicting the risk of HTN in men.

Association beween resting heart rate, shear and flow-mediated dilation in healthy adults

Preclinical data have demonstrated that heart rate (HR) can directly impact vascular endothelial function, in part, through a shear-stress mechanism. This study sought to explore, in humans, the associations between resting heart rate and both shear and endothelial function assessed by flow-mediated dilation (FMD). The brachial artery FMD test was performed in 31 apparently healthy volunteers. Basal (B) and hyperaemic (H) shear were quantified in the following two ways using data from the FMD test: the traditional cumulative shear area under the curve up to peak dilation (Shearcum) method; and our novel method of shear summation (Shearsum), which accounts for HR by summing each individual cardiac cycle shear up to peak dilation. Data were grouped by tertiles based on resting HR as follows: low (LHR = 43-56 beats min(-1); n = 10); middle (MHR = 58-68 beats min(-1); n = 11); and high (HHR = 69-77 beats min(-1); n = 10). Within the LHR group, both B-Shearcum and H-Shearcum were significantly higher (P < 0.001) than B-Shearsum and H-Shearsum, respectively, whereas in the HHR group B-Shearcum and H-Shearcum were significantly lower (P < 0.001) than B-Shearsum and H-Shearsum, respectively. The FMD in the LHR group (8.8 ± 0.8%) was significantly greater than that in both the MHR group (5.5 ± 0.8%; P = 0.009) and the HHR group (5.9 ± 0.8%; P = 0.024). These findings demonstrate the existence of a relationship between heart rate and both shear and endothelial function in humans. Moreover, these findings have implications for considering heart rate as an important physiological variable when quantifying shear and performing the FMD test.

Elevated resting heart rate and reduced orthostatic tolerance in obese humans

BACKGROUND

Obesity is linked with numerous physiological impairments; however, its impact on orthostatic tolerance (OT) remains unknown. This study tested the hypothesis that OT is reduced in obese individuals, and that reduced heart rate (HR) reserve and impaired cerebral autoregulation contribute to impaired OT.

METHODS

Eleven obese (8 females) and 22 non-obese (10 females) individuals were exposed to incremental lower body negative pressure (LBNP) to presyncope while HR, arterial blood pressure, and cerebral perfusion (middle cerebral artery blood velocity; MCA V mean) were measured. OT was quantified with a cumulative stress index (CSI).

RESULTS

OT was reduced in obese subjects, and there was an inverse relationship between body mass index (BMI) and OT (R = -0.47). HR was higher at rest and during each level of LBNP completed by all subjects. Similar peak HR (HRpeak) during LBNP between obese and non-obese subjects resulted in obese having a higher %peak HR at rest and at each stage of LBNP compared. Relationships existed for BMI and resting %HRpeak (R = 0.45) and resting %HRpeak and CSI (R = -0.52). Despite lower CSI in obese, MCA V mean and indices of cerebral autoregulation were similar between groups at all time points.

CONCLUSIONS

These data suggest that OT is reduced in obese and a higher resting HR, but not impaired regulation of cerebral perfusion, may contribute to this reduction.

Influence of heart rate at rest for predicting the metabolic syndrome in older Chinese adults

The aim of this study was to examine the relationship between seated resting heart rate and the metabolic syndrome (MetS) among older residents of Guangzhou, South China. A total of 30,519 older participants (≥50 years) from the Guangzhou Biobank Cohort Study were stratified into quartiles based on seated resting heart rate. The associations between each quartile and the MetS were assessed using multivariable logistic regression. A total of 6,907 (22.8 %) individuals were diagnosed as having the MetS, which was significantly associated with increasing heart rate quartiles (P < 0.001). Participants in the uppermost quartile (mean resting heart rate 91 ± 8 beats/min) of this cardiovascular proxy had an almost twofold increased adjusted risk (odds ratio (95 % CI) = 1.94 (1.79, 2.11), P < 0.001) for the MetS, as compared to those in the lowest quartile (mean resting heart rate, 63 ± 4 beats/min). Heart rate, which is an inexpensive and simple clinical measure, was independently associated with the MetS in older Chinese adults. We hope these observations will spur further studies to examine the usefulness of resting heart rate as a means of risk stratification in such populations, for which targeted interventions should be implemented.

Why socially deprived populations have a faster resting heart rate: impact of behaviour, life course anthropometry, and biology--the RECORD Cohort Study

Although studies have shown that resting heart rate (RHR) is predictive of cardiovascular morbidity/mortality, few studies focused on the epidemiology and social aetiology of RHR. Using the RECORD Cohort Study (7158 participants, 2007-2008, Paris region, France), we investigated individual/neighbourhood socioeconomic variables associated with resting heart rate, and assessed which of a number of psychological factors (depression and stress), behaviour (sport-related energy expenditure, medication use, and alcohol, coffee, and tobacco consumption), life course anthropometric factors (body mass index, waist circumference, and leg length as a marker of childhood environmental exposures), and biologic factors (alkaline phosphatase and gamma-glutamyltransferase) contributed to the socioeconomic disadvantage-RHR relationship. Combining individual/neighbourhood socioeconomic factors in a socioeconomic score, RHR increased with socioeconomic disadvantage: +0.9 [95% credible interval (CrI): +0.2, +1.6], +1.8 (95% CrI: +1.0, +2.5), and +3.6 (95% CrI: +2.9, +4.4) bpm for the 3 categories reflecting increasing disadvantage, compared with the lowest disadvantage category. Twenty-one percent of the socioeconomic disadvantage-RHR relationship was explained by sport practise variables, 9% by waist circumference, 7% by gamma-glutamyltransferase, 5% by alkaline phosphatase, and 3% by leg length. Future research should further clarify the mechanisms through which socioeconomic disadvantage influences resting heart rate, as a pathway to social disparities in cardiovascular morbidity/mortality.

[Ivabradine in coronary heart disease: experimental and clinical pharmacology]

The present paper reviews clinical evidence underlining the role of ivabradine in the management of patient with ischemic heart disease. Reduction in heart rate mediated by this selective I(f) current inhibitor has been associated with anti-ischemic efficacy without any effect on haemodynamic or myocardial contractility. The antianginal efficacy of ivabradine is similar or superior to that of conventional anti-ischemic agents. Moreover combination therapy with ivabradine provides substantial benefit in patients already receiving beta-blocker. Prognostic efficacy of ivabradine is evaluated in a large program of studies, among which BEAUTIFUL in coronary patients with left ventricular dysfunction. The SIGNIFY study is ongoing in stable coronary patients without ventricular dysfunction. Furthermore the SHIFT trial will evaluate ivabradine benefits in heart failure patients, whatever the origin, ischemic or not.

Biological mechanisms of disease and death in Moscow: rationale and design of the survey on Stress Aging and Health in Russia (SAHR)

BACKGROUND

Prior research has revealed large differences in health and mortality across countries, socioeconomic groups, and individuals. Russia experiences one of the world's highest levels of all-cause and cardiovascular mortality, great mortality differences within the population, and a heavy burden of ill health. Psychological stress has been suggested as a likely explanation of health loss and premature death in Russia and Eastern Europe. However, physiological mechanisms connecting stress with health in Russia remain unclear since existing epidemiological data are scarce and limited to conventional risk factors.

METHOD AND DESIGN

The survey on Stress Aging and Health in Russia (SAHR) is addressing this knowledge gap by collecting an unusually rich database that includes a wide range of reported information, physical and cognitive health outcomes, and biomarkers in a sample of Muscovite men and women aged 55 and older. The total planned sample size is 2,000 individuals. The sample was randomly selected from epidemiological cohorts formed in Moscow between the mid-1970s and the 1990s and from medical population registers. The baseline data collection was carried out from December 2006 to June 2009. Interviews and medical tests were administered at hospital or at home according to standardized protocol. Questionnaire information includes health, socio-demographic characteristics, economic well-being, cognitive functioning, and batteries on stress and depression. Biomarkers include anthropometry, grip strength, resting ECG, conventional cardiovascular factors of risk such as lipid profile and blood pressure, and other biochemical parameters such as those related to inflammation, glucose and insulin resistance, coagulation, fibrinolysis, and stress hormones. In addition to these measurements, SAHR includes dynamic biomarkers provided by 24-hour ECG (Holter) monitoring. This method continuously registers the beat-to-beat heart rate in naturalistic conditions without restrictions on normal daily activities. It provides information about heart functioning, including heart rate variability and ischemic and arrhythmic events.Re-examination of the study subjects will be conducted in 2009-2011 and will focus on health, functional status, economic conditions, behaviors, and attitudes towards aging. The subjects are also followed up for mortality and non-fatal health events.

DISCUSSION

The SAHR will produce a valuable set of established and novel biomarkers combined with self-reported data for the international research community and will provide important insights into factors and biological mechanisms of mortality and health losses in Russia.

Variables influencing heart rate

In both physiologic and pathological conditions, instantaneous heart rate value is the result of a rather complex interplay. It constantly varies under the influence of a number of factors: nonmodifiable and modifiable ones. Pharmacologic blockade with beta-adrenergic antagonists and/or with parasympathetic antagonists such as atropine have permitted the identification of the mechanisms of autonomic nervous regulation of heart rate in a variety of physiologic and pathological conditions. The analysis of heart rate and blood pressure variability has yielded additional information on the autonomic control of the circulation, which has proven to have diagnostic and prognostic implications in a number of clinically relevant conditions such as hypertension, acute myocardial infarction, heart failure, and predisposition to sudden cardiac death. This article will summarize, based on available epidemiologic and clinical studies, the key variables influencing heart rate and heart rate variability in view of the known association between heart rate and cardiovascular disease.

Higher heart rate may predispose to obesity and diabetes mellitus: 20-year prospective study in a general population

BACKGROUND

Emerging evidence indicates an association between sympathetic activation and metabolic syndrome. However, sympathetic activation in metabolic syndrome may be a cause, consequence, or just epiphenomenon. To elucidate this issue, the predictive power of resting heart rate for the development of abnormal glucose and lipid metabolisms after 20 years was evaluated in a general population.

METHODS

A total of 637 participants (>20 years old) underwent a health examination in 1979 including measurements of blood chemistries. Resting heart rate (bpm) was measured by an electrocardiogram. In 1999, all of the study participants again underwent a health examination, including electrocardiogram and blood chemistries. Because four of them had atrial fibrillation, and 19 subjects were taking antihypertensive medication in 1979, they were excluded from analysis. Therefore, a complete dataset of 614 subjects was available.

RESULTS

As was reported in our previous article, in 1999 we found a linear and significant (P < 0.05) cross-sectional relationship between resting heart rate and a cluster of cardiometabolic risk factors (blood pressure (BP), free fatty acid (FFA), plasma glucose, and homeostasis model assessment (HOMA) index). Baseline higher heart rate (heart rate >or=80 bpm in 1979) predicted the development of obesity, diabetes mellitus (DM), and insulin resistance in 1999 after adjustments for age, sex, and other confounders.

CONCLUSION

This is one of the first prospective reports demonstrating that higher heart rate may predispose to the development of obesity and DM, suggesting that the sympathetic nerve system may play a role in the development of obesity and DM.

Cardiovascular risk, obesity, and myocardial blood flow in postmenopausal women

BACKGROUND

This study was designed to determine whether overweight or obese status is independently associated with myocardial flow reserve (MFR), an established predictor of cardiovascular mortality, in a group of postmenopausal women with no previous cardiovascular disease. Postmenopausal women are the largest group of overweight and physically inactive individuals in the United States. Increased body mass index (BMI) is consistently associated with increased cardiovascular mortality in this population. Whether this is because of obesity itself or the accompanying increase in cardiovascular risk factors (CRFs) remains controversial.

METHODS

We examined the relationship of myocardial blood flow (MBF), coronary vascular resistance, and MFR to BMI in 60 postmenopausal women with no coronary heart disease. Subjects underwent dynamic N-13 ammonia positron emission tomography for the measurement of MBF and MFR. Baseline demographics, CRF, and hemodynamic parameters were recorded for each subject. Datasets were divided into 3 groups according to BMI: normal (18 to 24), overweight (25 to 29), and obese (>or=30).

RESULTS

The overweight and obese groups showed significantly higher resting MBF and lower MFR than the normal-weight group (both P < .001), even after adjusting for CRF. A further analysis of subjects without any CRF (n = 35) showed that the MFR remained significantly lower in the obese compared with normal-weight subjects (P = .05). Levels of known markers of vascular inflammation (high-sensitivity C-reactive protein and homocysteine) and high-density lipoprotein cholesterol levels correlated with declining MFR.

CONCLUSIONS

These findings provide a mechanistic link between obesity and coronary heart disease in this population.

The role of heart rate reduction in angina management and beyond

This article highlights the significance of heart rate as an independent risk factor and prognostic marker for cardiovascular disease and examines the pharmacological measures available that lead to effective heart rate reduction.

Treating patients with overactive bladder syndrome with antimuscarinics: heart rate considerations

In this excellent mini-review, the authors present an extensive and relevant paper on the effect of antimuscarinic agents on the heart. This is without doubt the most detailed and the most reader-friendly paper on this subject, and I am sure that it will help urologists to assist in further educating their patients when prescribing these compounds.

The effect of intensive diabetes treatment on resting heart rate in type 1 diabetes: the Diabetes Control and Complications Trial/Epidemiology of Diabetes Interventions and Complications study

OBJECTIVE

Cardiovascular disease is a major cause of morbidity and mortality in individuals with type 1 diabetes. Resting heart rate (RHR) is a risk factor for cardiovascular disease in the general population, and case-control studies have reported a higher RHR in individuals with type 1 diabetes. In individuals with type 1 diabetes, there is a positive correlation between A1C and RHR; however, no prospective studies have examined whether a causal relationship exists between A1C and RHR. We hypothesized that intensive diabetes treatment aimed to achieve normal A1C levels has an effect on RHR in individuals with type 1 diabetes.

RESEARCH DESIGN AND METHODS

A total of 1,441 individuals with type 1 diabetes who participated in the Diabetes Control and Complications Trial (DCCT) had their RHR measured biennially by an electrocardiogram during the DCCT and annually for 10 years during the Epidemiology of Diabetes Interventions and Complications (EDIC) follow-up study.

RESULTS

During the DCCT, intensive treatment was associated with lower mean RHR than conventional treatment, both in adolescents (69.0 vs. 72.0 bpm [95% CI 62.8-75.7 and 65.7-78.9, respectively], P = 0.013) and adults (66.8 vs. 68.2 [65.3-68.4 and 66.6-69.8, respectively], P = 0.0014). During follow-up in the EDIC, the difference in RHR between the treatment groups persisted for at least 10 years (P < 0.0001).

CONCLUSIONS

Compared with conventional therapy, intensive diabetes management is associated with lower RHR in type 1 diabetes. The lower RHR with intensive therapy may explain, in part, its effect in reducing cardiovascular disease, recently demonstrated in type 1 diabetes.

Prognostic significance of PVCs and resting heart rate

BACKGROUND

We sought to evaluate the prognostic significance of premature ventricular contractions (PVCs) on a routine electrocardiogram (ECG) and to evaluate the relationship between heart rate and PVCs.

METHODS

Computerized 12-lead ECGs of 45,402 veterans were analyzed. Vital status was available through the California Health Department Service.

RESULTS

There were 1731 patients with PVCs (3.8%). Compared to patients without PVCs, those with PVCs had significantly higher all-cause (39% vs 22%, P < 0.001) and cardiovascular mortality (20% vs 8%, P < 0.001). PVCs remain a significant predictor even after adjustment for age and other ECG abnormalities. The presence of multiple PVCs or complex morphologies did not add significant additional prognostic information. Those patients with PVCs had a significantly higher heart rate than those without PVCs (mean +/- SD: 78.6 +/- 15 vs 73.5 +/- 16 bpm, P < 0.001). When patients were divided into groups by heart rate (<60, 60-79, 80-99 and >100 bpm) and by the presence or absence of PVCs, mortality increased progressively with heart rate and doubled with the presence of PVCs. Using regression analysis, heart rate was demonstrated to be an independent and significant predictor of PVCs.

CONCLUSIONS

PVCs on a resting ECG are a significant and independent predictor of all-cause and cardiovascular mortality. Increased heart rate predicts mortality in patients with and without PVCs and the combination dramatically increases mortality. These findings together with the demonstrated independent association of heart rate with PVCs suggest that a hyperadrenergic state is present in patients with PVCs and that it likely contributes to their adverse prognosis.

The role of heart rate in the development of cardiovascular disease

Heart rate is an independent risk factor for patients with cardiovascular disease, in particular with arterial hypertension, myocardial infarction, coronary artery disease and heart failure. This relation is supported by a large number of animal studies as well as clinical trials which are summarized in this article. These studies demonstrated detrimental effects of increased heart rate on the function and structure of the cardiovascular system. Heart rate can be easily detected during physical examination of the patient and therefore allows a simple conclusion on prognosis and efficiency of therapy.

Association of beta-adrenoceptor single nucleotide polymorphisms with resting heart rate

The association of beta-adrenoceptor (B-AR, including three subgroups: Beta1, Beta2 and Beta3) single nucleotide polymorphisms (SNP) with resting heart rate (RHR) were analyzed. RHR of 107 healthy subjects in the supine were detected by computerized system for 8 minutes. Genotyping SNPs of S/G49 and R/G389 of Beta1-AR and W/R64 of Beta3-AR in these subjects were by means of PCR-restriction fragment length polymorphism (PCR-RFLP) technique. Genotyping SNPs of R/G16 and Q/E27 of Beta1-adrenoceptor in these subjects were by means of allele specific primer-PCR (ASP-PCR) technique. It was found that there was no significant difference among RHRs corresponding above SNPs of B-AR, but the SNP of R/G389 of Beta1-AR, in which there was significant difference among RHRs (P<0.05). Either in the female individuals or in the male, those with Beta1-AR G/G389 genotype had the highest RHR. The females with R/R389 genotype had the lowest RHR, however, the males with R/G389 genotype had the lowest RHR. The RHR was not only associated with R/G389 polymorphism of Beta1-adrenoceptor gene significantly, but also was associated with gender in Chinese.

[Heart rate reduction as a therapeutic strategy: novel options]

Elevated heart rate is associated with increased cardiovascular mortality. Heart rate reduction optimises myocardial oxygen consumption and decreases angina pectoris symptoms. Thus, heart rate control is an important therapeutic strategy in coronary artery disease and, for example, chronic heart failure. The pacemaker current I(f) plays a central role in determining spontaneous activity of the sinus node. Ivabradine, a selective inhibitor of the I(f) channel, reduces heart rate without any effect on cardiac contractility and without lowering blood pressure. While beta-blockers remain the first choice for heart rate reduction, in cases of adverse effects ivabradine may be used to treat stable angina pectoris. Studies evaluating possible further uses, for example in heart failure or after acute myocardial infarction, are still warranted.

Reference values for the 6-min walk test in healthy subjects 20-50 years old

In 102 healthy Caucasians, 20-50 years old, we investigated the effect of anthropometrics on the 6-min walk test (6MWT), in order to provide reference values for walk distance (6MWD), oxygen saturation (SpO2), pulse rate (PR), respiratory rate (RR), breathlessness perception (VAS) and for the walking distance and body weight product (DW). The mean 6MWD and DW values were 593 +/- 57 and 638+/-44 m (P < 0.01) and 35,030 +/- 5306 and 48,882 +/- 6555 kg m (P < 0.01), respectively for women and for men. While walking, SpO2 remained unaltered and subjects reached 67 +/- 10% of their maximal predicted heart rate and a RR mean value of 19 +/- 4 bpm. VAS ratings were significantly higher in females as compared to males (24 +/- 15 vs. 18 +/- 5 mm, P < 0.05), however, when corrected for PR change while walking, they were not different. The equation by stepwise multiple regression analysis included height, age and gender for the 6MWD and accounted for 42% of the total variance. This study confirms the relevant effect of anthropometrics on walking capacity and suggests that when rating dyspnea, the change in heart rate during walking should be considered.

Ivabradine -- the first selective sinus node I(f) channel inhibitor in the treatment of stable angina

Heart rate, a major determinant of angina in coronary disease, is also an important predictor of cardiovascular mortality. Lowering heart rate is therefore one of the most important therapeutic approaches in the treatment of stable angina pectoris. To date, beta-blockers and some calcium-channel antagonists reduce heart rate, but their use may be limited by adverse reactions or contraindications. Heart rate is determined by spontaneous electrical pacemaker activity in the sinoatrial node controlled by the I(f) current. Ivabradine is the first specific heart rate-lowering agent that has completed clinical development for stable angina pectoris. It is selective for the I(f) current, lowering heart rate at concentrations that do not affect other cardiac ionic currents. Specific heart-rate lowering with ivabradine reduces myocardial oxygen demand, simultaneously improving oxygen supply. Ivabradine has no negative inotropic or lusitropic effects, preserving ventricular contractility, and does not change any major electrophysiological parameters unrelated to heart rate. Randomised clinical studies in patients with stable angina show that ivabradine effectively reduces heart rate, improves exercise capacity and reduces the number of angina attacks. It has superior anti-anginal and anti-ischaemic activity to placebo and is non-inferior to atenolol and amlodipine. Ivabradine therefore offers a valuable approach to lowering heart rate exclusively and provides an attractive alternative to conventional treatment for a wide range of patients with confirmed stable angina.

Influence of age, gender, and serum triglycerides on heart rate in a cohort of asymptomatic individuals without heart disease

BACKGROUND

Age, sex and blood lipids were demonstrated in epidemiological studies to influence heart rate measured on physical examination, on 12-lead electrocardiogram or with automatic devices for short-term measurements. We hypothesized that in healthy individuals, age, sex and other clinical variables may also influence heart rate measured on 24-h ambulatory electrocardiographic monitoring.

METHODS

We studied 625 asymptomatic individuals with normal clinical examination, aged 15 to 83 (mean 42, standard deviation 11.9) years, 276 (44.2%) men and 349 (55.8%) women. Heart rate was evaluated on 24 h ambulatory electrocardiographic monitoring. Variables selected in univariate analysis (chi(2) and Student t tests) were further submitted to multivariate analysis with canonical correlation to assess the strength of associations between heart rate and other variables, and multiple linear regression models to generate reference curves.

RESULTS

Age was the most significant influence on canonical variable of heart rate relative to other clinical and laboratory variables (0.55; p<0.01). There was an increase in the minimum heart rate and a decrease of maximum heart rate with increasing age in both genders. The increase was steeper in men and the decrease was steeper in women. Minimum heart rate increased with increasing serum triglycerides and decreased as estimated maximum oxygen consumption increased.

CONCLUSIONS

There was a narrower variation of heart rate with increasing age in both genders in healthy individuals. This variation was less pronounced in women. In addition, status of body haemostasis associated with peculiar metabolic conditions expressed in serum triglycerides levels may also be associated with heart rate.

Drug insight: If inhibitors as specific heart-rate-reducing agents

Heart rate is determined primarily by spontaneously repeating net inward current carried by sodium ions and potassium ions through hyperpolarization-activated cyclic-nucleotide-gated channels. Within the heart, these channels are found most abundantly in sinoatrial cardiomyocytes. The channels open in response to membrane hyperpolarization, modulated by local cAMP concentrations. They permit activation of the I(f) current, which can be blocked specifically by molecules characterized by linked benzazepinone and benzocyclobutane rings, and which are devoid of effects on cardiac conduction, inotropy or peripheral vascular tone. The resulting heart-rate reduction has been effective in angina prevention in clinical trials involving 4,000 patients, using the prototype I(f) inhibitor, ivabradine. No serious adverse events have been attributed to the treatment; the most prominent side-effect is dose-related, always reversible and often transient visual symptoms that seldom result in voluntary drug discontinuation.

Baroreflex Regulation of Heart Rate and Sympathetic Vasomotor Tone in Women and Men

Gender has been reported to influence baroreflex heart rate regulation and baroreflex blood pressure buffering. We tested the hypothesis that gender influences baroreflex regulation of heart rate and sympathetic vasomotor tone. We recruited 32 normal-weight healthy subjects (17 men and 15 women). ECGs for heart rate, brachial and finger blood pressure, and muscle sympathetic nerve activity (MSNA) were measured. Baroreflex heart rate and MSNA regulation were assessed using incremental phenylephrine and nitroprusside infusions. Baseline blood pressure was similar in men and women. MSNA was 21+/-2.5 bursts/min in women and 19+/-2.8 bursts/min in men (NS). The gain of the baroreflex MSNA curves was similar in women and men (-1.9+/-0.2 bursts/min per mm Hg in men and -2.0+/-0.3 bursts/min per mm Hg in women). Baroreflex gain for heart rate regulation was 17+/-3.2 ms/mm Hg in women and 19+/-1.9 ms/mm Hg in men (NS). We conclude that baroreflex gains for heart rate and sympathetic MSNA regulation are similar in women and men. However, the probability for congruence between men and women in terms of the MSNA baroreflex curves was 0.06% for burst rate, 0.4% for burst incidence, and 0.01% for burst area. In women, the MSNA baroreflex curve may be shifted to slightly lower blood pressure such that at a given blood pressure MSNA tends to be lower.

[From ischaemia to heart failure: heart rate--actor or stamper?]

The heart rate in sinus rhythm depends on If current-induced automaticity of sinus node cells. Such a current is activated by hyperpolarisation and is modulated by influences from sympathetic and para-sympathetic tones. There are established prognostic values for the baseline heart rate and its variability in coronary heart disease and heart failure. However, heart rate per se directly modulates myocardial oxygen consumption and cardiac contractility by interfering with the excitation-contraction coupling. The therapeutic implications of pharmacological modulation of the heart rate are important mainly for slowing the heart rate, as illustrated by the use of calcium antagonists in coronary heart disease and beta-blockers in both coronary heart disease and heart failure. The possibility of a direct action on sinusal automaticity by drugs such as ivabradine, an If channel blocker, reveals new therapeutic perspectives. Indeed, a benefit of combination therapy with these drugs and beta-blockers should be lower heart rate values than can be attained with maximally tolerated doses of beta-blockers.

Phenotypical evidence for a gender difference in cardiac norepinephrine transporter function

Norepinephrine transporter (NET) function has a central role in the regulation of synaptic norepinephrine concentrations. Clinical observations in orthostatic intolerance patients suggest a gender difference in NET function. We compared the cardiovascular response to selective NET inhibition with reboxetine between 12 healthy men and 12 age-matched women. Finger blood pressure, brachial blood pressure, and heart rate were measured. The subjects underwent cardiovascular autonomic reflex testing and a graded head-up tilt test. In a separate study, we applied incremental concentrations of tyramine and isoproterenol through subcutaneous microdialysis catheters in eight men and in eight women. NET inhibition elicited a threefold greater increase in supine blood pressure in men than women (P < 0.05). The pressor response was driven by an increased cardiac output. The orthostatic heart rate increase during NET inhibition was greater in men than women (56 +/- 5 beats/min in men, 42 +/- 4 beats/min in women, P < 0.001). In contrast, NET inhibition resulted in a similar suppression in the cold pressor and handgrip response, low-frequency blood pressure oscillations, and venous norepinephrine in the supine position. Men and women were similarly sensitive to the lipolytic effect of isoproterenol and tyramine. We conclude that NET inhibition results in more pronounced changes in cardiac regulation in men than women. Our observations suggest that the NET contribution to cardiac norepinephrine turnover may be decreased in women. The gender difference in NET function may not be expressed in tissues that are less NET dependent than the heart.

Host and environmental determinants of heart rate and heart rate variability in four European populations

OBJECTIVE

In a population-based sample of nuclear families recruited in the framework of the European Project on Genes in Hypertension (EPOGH), we investigated the association between heart rate (HR) and its variability (HRV), and gender, age, posture, breathing frequency, body mass index, systolic blood pressure, family history of hypertension and various lifestyle factors, such as smoking, alcohol and coffee consumption and physical activity.

METHODS

RR interval and respiration were registered in the supine and standing positions (15 min each) in 1208 subjects in Bucharest (Romania, n= 267), Cracow (Poland, n= 323), Mirano (Italy, n= 323) and Novosibirsk (Russian Federation, n= 295). After exclusion of 199 participants on antihypertensive treatment and/or patients with diabetes mellitus (n= 40) or myocardial infarction (n= 4), 993 subjects were eligible for analysis. We evaluated 858 participants with high-quality recordings. Using fast Fourier transform, we decomposed HRV into low-frequency (LF: 0.04-0.15 Hz) and high-frequency (HF: 0.15-0.40 Hz) components, which were expressed in normalized units.

RESULTS

Mean values were 35.3 years for age, 24.3 kg/m for body mass index (BMI) and 121.0/77.2 mmHg for blood pressure. The group included 462 (53.8%) women. Across four centres, HR and HRV were similarly and independently associated with gender, age and postural position (P <0.001). In the supine position, HR was higher in women than men (67.2 versus 63.7 bpm). Men had higher normalized LF power than women (48.8 versus 41.5), but lower HF power (40.6 versus 47.4). The normalized HF power decreased with age (r = -0.43), whereas LF power increased (r = 0.32). On standing, HR increased (83.3 versus 65.6 bpm), normalized HF power declined (19.2 versus 44.3) and LF power increased (67.4 versus 44.9). The independent effects of respiration frequency, systolic blood pressure, family history of hypertension, body mass index and lifestyle factors on HRV differed between populations, and explained no more than 8% of the total variance.

CONCLUSIONS

Across four European populations, gender, age and posture were consistent and independent correlates of HR and HRV. Lifestyle seems to have small but varying influences on HR and/or HRV, probably depending on the environmental and cultural background of the population under study.