Association between nighttime heart rate and cardiovascular mortality in patients with implantable cardioverter-defibrillator: A cohort study

BACKGROUND

Although studies have shown that an increased resting heart rate measured randomly at a single point of the day has been associated with adverse cardiovascular outcomes, the utility of continuous monitoring of nighttime heart rate (NTHR) has remained largely uninvestigated.

OBJECTIVE

This study aimed to explore the association between NTHR and cardiovascular mortality.

METHODS

The Study of Home Monitoring System Safety and Efficacy in Cardiac Implantable Electronic Device-implanted Patients, which is a prospective cohort study, enrolled patients with implantable cardioverter-defibrillator (ICD) or cardiac resynchronization therapy defibrillator between 2010 and 2015. Baseline NTHR was measured during the programmed sleep period from 30 to 60 days after implantation. The primary outcome was cardiovascular mortality, fitted by a restricted cubic spline function.

RESULTS

A total of 534 implantable cardioverter-defibrillator recipients with sinus rhythm during the detection window were included in the study. The mean baseline NTHR was 59.6 ± 8.0 beats/min. During the follow-up period of 60.4 ± 21.8 months, 88 (16.5%) patients experienced cardiovascular mortality. After considering potential confounders, a linear association was observed. Each 1 beat/min increase in NTHR was associated with a 7.8%, 10.1%, and 5.7% increase in the risk of cardiovascular mortality in the total population, patients with heart failure, and patients without heart failure, respectively.

CONCLUSION

Continuous monitoring of NTHR may identify patients at high risk of cardiovascular mortality in a timely manner, with the potential for "preemptive" action.

TRIAL REGISTRATION

No. ChiCTR-ONRC-13003695.

Assessment of cardiovascular load among hotel room cleaners

Hotel room cleaners are a vulnerable population at risk for cardiovascular disease. To evaluate their workload heart rate (HR), % heart rate reserve (%HRR), blood pressure (BP), metabolic equivalent (MET), and energy expenditure (EE) were measured over two workdays and two off-workdays. The mean age was 45.5 (SD 8.2) years with a mean 10.4 (SD 7.8) years of work experience. Mean average and peak HR, %HRR, MET, and EE were significantly higher during a workday than an off-workday for the entire work shift, first and last hour of work. Mean average HR and %HRR saw the largest increase between the lunch and post-lunch interim. One-fourth of subjects exceeded the recommended 30% HRR threshold for 8-hour shifts. Some workers experienced a substantial increase in HR and DBP over a workday indicating physiologic fatigue and thus may be at increased risk for cardiovascular disease and premature death due to excessive physical work demands.

Predictive modeling the probability of suffering from metabolic syndrome using machine learning: A population-based study

Background

There is an increasing trend of Metabolic syndrome (MetS) prevalence, which has been considered as an important contributor for cardiovascular disease (CVD), cancers and diabetes. However, there is often a long asymptomatic phase of MetS, resulting in not diagnosed and intervened so timely as needed. It would be very helpful to explore tools to predict the probability of suffering from MetS in daily life or routinely clinical practice.

Objective

To develop models that predict individuals' probability of suffering from MetS timely with high efficacy in general population.

Methods

The present study enrolled 8964 individuals aged 40-75 years without severe diseases, which was a part of the REACTION study from October 2011 to February 2012. We developed three prediction models for different scenarios in hospital (Model 1, 2) or at home (Model 3) based on LightGBM (LGBM) technique and corresponding logistic regression (LR) models were also constructed for comparison. Model 1 included variables of laboratory tests, lifestyles and anthropometric measurements while model 2 was built with components of MetS excluded based on model 1, and model 3 was constructed with blood biochemical indexes removed based on model 2. Additionally, we also investigated the strength of association between the predictive factors and MetS, as well as that between the predictors and each component of MetS.

Results

In this study, 2714 (30.3%) participants suffer from MetS accordingly. The performances of the LGBM models in predicting the probability of suffering from MetS produced good results and were presented as follows: model 1 had an area under the curve (AUC) value of 0.993 while model 2 indicated an AUC value of 0.885. Model 3 had an AUC value of 0.859, which is close to that of model 2. The AUC values of LR model 1 and 2 for the scenario in hospital and model 3 at home were 0.938, 0.839 and 0.820 respectively, which seemed lower than that of their corresponding machine learning models, respectively. In both LGBM and logistic models, gender, height and resting pulse rate (RPR) were predictors for MetS. Women had higher risk of MetS than men (OR 8.84, CI: 6.70-11.66), and each 1-cm increase in height indicated 3.8% higher risk of suffering from MetS in people over 58 years, whereas each 1- Beat Per Minute (bpm) increase in RPR showed 1.0% higher risk in individuals younger than 62 years.

Conclusion

The present study showed that the prediction models developed by machine learning demonstrated effective in evaluating the probability of suffering from MetS, and presented prominent predicting efficacies and accuracies. Additionally, we found that women showed a higher risk of MetS than men, and height in individuals over 58 years was important factor in predicting the probability of suffering from MetS while RPR was of vital importance in people aged 40-62 years.

Associations between the rs5498 (A > G) and rs281432 (C > G) polymorphisms of the ICAM1 gene and atherosclerotic cardiovascular disease risk, including hypercholesterolemia

Background

Atherosclerotic cardiovascular disease (ASCVD) originates from complex risk factors, including age, gender, dyslipidemia, obesity, race, genetic and genetic variation. ICAM1 gene polymorphisms are a significant risk factor for ASCVD. However, the impact of the rs5498 and rs281432 polymorphisms on the prevalence of hypercholesterolemia (HCL) has not been reported. Therefore, we determine the relationships between single nucleotide polymorphisms (SNPs), including rs5498 and rs281432 on Intercellular adhesion molecule 1 gene (ICAM1) and ASCVD susceptibility in patients with HCL.

Methods

The clinical characteristics of 278 participants were assessed, and classified to groups having HCL and without HCL. ICAM1 SNPs genotyping was performed by DNA sequencing, and ICAM1 expression was measured using real-time PCR.

Results

Positive dominant model rs5498 participants had twice the risk of HCL (95% confidence interval (CI): [1.24-3.23], P = 0.005). The frequency of the G allele in rs5498 was 1.69 times higher in participants with HCL than in controls (95% CI [1.15-2.47], P = 0.007). Participants with the rs5498 AG or GG variants and high ICAM1 mRNA expression (≥3.12) had 2.49 times the risk (95% CI [1.42-4.38], P = 0.001), and those with a high LDL-C concentration (≥3.36 mmol/L) had 2.09 times the risk (95% CI [1.19-3.66], P = 0.010) of developing ASCVD compared with those with low ICAM1 mRNA and LDL-C levels. Interestingly, participants carrying the rs5498 AG or GG variants who had tachycardia (resting heart rates (RHRs) >100 beats/min) had a 5.02-times higher risk than those with a lower RHR (95% CI [1.35-18.63], P = 0.016).

Conclusions

It may consider the G allele in ICAM1 rs5498 is associated with a higher risk of ASCVD in Thai people with HCL, and is also positively associated with ICAM1 mRNA expression, LDL-C concentration, and RHR.

Initial in-hospital heart rate is associated with long-term survival in patients with acute ischemic stroke

Aims

Increased heart rate has been associated with stroke risk and outcomes. The purpose of this study was to explore the long-term prognostic value of initial in-hospital heart rate in patients with acute ischemic stroke (AIS).

Methods

We analyzed data from 21,655 patients with AIS enrolled (January 2010–September 2018) in the Chang Gung Research Database. Mean initial in-hospital heart rates were averaged and categorized into 10-beat-per-minute (bpm) increments. The primary and secondary outcomes were all-cause mortality and cardiovascular death. Hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated using multivariable adjusted Cox proportional hazard models, using the heart rate < 60 bpm subgroup as the reference.

Results

The adjusted HRs for all-cause mortality were 1.23 (95% CI 1.08–1.41) for heart rate 60–69 bpm, 1.74 (95% CI 1.53–1.97) for heart rate 70–79 bpm, 2.16 (95% CI 1.89–2.46) for heart rate 80–89 bpm, and 2.83 (95% CI 2.46–3.25) for heart rate ≥ 90 bpm compared with the reference group. Likewise, heart rate ≥ 60 bpm was also associated with an increased risk of cardiovascular death (adjusted HR 1.18 [95% CI 0.95–1.46] for heart rate 60–69 bpm, 1.57 [95% CI 1.28–1.93] for heart rate 70–79 bpm, 1.98 [95% CI 1.60–2.45] for heart rate 80–89 bpm, and 2.36 [95% CI 1.89–2.95] for heart rate ≥ 90 bpm).

Conclusions

High initial in-hospital heart rate is an independent predictor of all-cause mortality and cardiovascular death in patients with AIS.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s00392-021-01953-5.

Associations of Sedentary Time with Heart Rate and Heart Rate Variability in Adults: A Systematic Review and Meta-Analysis of Observational Studies

PURPOSE

To evaluate if sedentary time (ST) is associated with heart rate (HR) and variability (HRV) in adults.

METHODS

We systematically searched PubMed and Google Scholar through June 2020. Inclusion criteria were observational design, humans, adults, English language, ST as the exposure, resting HR/HRV as the outcome, and (meta-analysis only) availability of the quantitative association with variability. After qualitative synthesis, meta-analysis used inverse variance heterogeneity models to estimate pooled associations.

RESULTS

Thirteen and eight articles met the criteria for the systematic review and meta-analysis, respectively. All studies were cross-sectional and few used gold standard ST or HRV assessment methodology. The qualitative synthesis suggested no associations between ST and HR/HRV. The meta-analysis found a significant association between ST and HR (β = 0.24 bpm per hour ST; CI: 0.10, 0.37) that was stronger in males (β = 0.36 bpm per hour ST; CI: 0.19, 0.53). Pooled associations between ST and HRV indices were non-significant (p > 0.05). Substantial heterogeneity was detected.

CONCLUSIONS

The limited available evidence suggests an unfavorable but not clinically meaningful association between ST and HR, but no association with HRV. Future longitudinal studies assessing ST with thigh-based monitoring and HRV with electrocardiogram are needed.

Chronotropic effects and mechanisms of long-chain omega-3 polyunsaturated fatty acids on heartbeat: the latest insights

The roles of the resting heart rate (RHR) have been actively investigated and increasingly recognized in recent decades, because of the growing evidence that fast RHR is associated with and predicts the risk of developing cardiovascular and metabolic disorders, as well as all-cause mortality. Long-chain omega-3 polyunsaturated fatty acids (PUFAs) (eg, eicosapentaenoic acid and docosahexaenoic acid) have been shown to have chronotropic effects on heartbeat in both healthy people and patients with various disease conditions. The aims of this review are (1) to briefly summarize the importance of elevated RHR in disease pathogenesis and mortality; (2) to provide an update on the negative chronotropic effect of omega-3 PUFAs on the heart; (3) to highlight how omega-3 PUFAs regulate heart rate through the autonomic nervous system - a central control mechanism; and (4) to highlight how omega-3 PUFAs modulate the trans-membrane ionic channels in cardiomyocytes - a fundamental mechanism of cardiac automaticity. Eicosapentaenoic acid and docosahexaenoic acid are nutrients derived from some aquatic organisms, and they can also be converted from digested oily seeds and nuts of some terrestrial plants in the body. The consumption of omega-3 PUFAs for RHR reduction represents a lifestyle modification for risk factor management and promises nutritional benefits for public health improvement.

Investigating the relationship between emotional granularity and cardiorespiratory physiological activity in daily life

Emotional granularity describes the ability to create emotional experiences that are precise and context-specific. Despite growing evidence of a link between emotional granularity and mental health, the physiological correlates of granularity have been under-investigated. This study explored the relationship between granularity and cardiorespiratory physiological activity in everyday life, with particular reference to the role of respiratory sinus arrhythmia (RSA), an estimate of vagal influence on the heart often associated with positive mental and physical health outcomes. Participants completed a physiologically triggered experience-sampling protocol including ambulatory recording of electrocardiogram, impedance cardiogram, movement, and posture. At each prompt, participants generated emotion labels to describe their current experience. In an end-of-day survey, participants elaborated on each prompt by rating the intensity of their experience on a standard set of emotion adjectives. Consistent with our hypotheses, individuals with higher granularity exhibited a larger number of distinct patterns of physiological activity during seated rest, and more situationally precise patterns of activity during emotional events: granularity was positively correlated with the number of clusters of cardiorespiratory physiological activity discovered in seated rest data, as well as with the performance of classifiers trained on event-related changes in physiological activity. Granularity was also positively associated with RSA during seated rest periods, although this relationship did not reach significance in this sample. These findings are consistent with constructionist accounts of emotion that propose concepts as a key mechanism underlying individual differences in emotional experience, physiological regulation, and physical health.

Associations between occupational relative aerobic workload and resting blood pressure among different age groups: a cross-sectional analysis in the DPhacto study

OBJECTIVE

High levels of occupational physical activity (OPA) increase heart rate, blood pressure (BP) and the risk of hypertension. Older workers may be more vulnerable to high levels of OPA due to age-related degeneration of the cardiovascular system and cardiorespiratory fitness. This study investigates the association of relative aerobic workload (RAW) with resting BP and examines if this relation is moderated by age.

DESIGN

Cross-sectional epidemiological study.

SETTING

Data were collected among employees of 15 Danish companies in the cleaning, manufacturing and transport sectors.

PARTICIPANTS

2107 employees were invited for participation, of these 1087 accepted and 562 (42% female and 4% non-Westerns) were included in the analysis based on the criteria of being non-pregnant, no allergy to bandages, sufficient amount of heart rate data corresponding to ≥4 work hours per workday or 75% of average work hours, and no missing outcome and confounder values.

PRIMARY AND SECONDARY OUTCOME MEASURES

The primary outcome measure was BP.

RESULTS

Heart rate reserve was estimated from ambulatory 24-hour heart rate measures covering 2.5 workdays per participant (SD 1.0 day). Age significantly moderated the association between RAW and BP. Mean intensity and duration of high RAW (≥30% heart rate reserve) showed positive associations with diastolic BP and negative associations with pulse pressure (PP) among participants ≥47 years old. Tendencies towards negative associations between RAW and BP were seen among participants <47 years old.

CONCLUSIONS

Mean intensity and duration of RAW increased diastolic BP among participants ≥47 years old. Negative associations with PP may be due to healthy worker selection bias. Prevention of hypertension should consider reductions in RAW for ageing workers.

Physical activity may compensate for prolonged TV time regarding pulse rate-a cross-sectional study

BACKGROUND

Regular exercise reduces pulse rate, but it is less clear how prolonged sitting time affects pulse rate. Our hypothesis was that high physical activity could compensate for prolonged sitting time regarding the pulse rate.

METHODS

Regression analysis was performed on cross-sectional data including 47,457 men and women based on two Swedish cohort studies, EpiHealth (18-45 years) and LifeGene (45-75 years). Self-reported leisure time physical activity was given in five levels, from low (level 1) to vigorous (level 5), and television time was used as a proxy of sitting time.

RESULTS

A higher physical activity (level 4 compared to level 1) was associated with a lower pulse rate in middle-aged females (-2.7 beats per minute [bpm]; 95% CI -3.3 to -2.2) and males (-4.0 bpm; 95% CI -4.7 to -3.4). The relationship between physical activity and pulse rate was strongest in the young. A prolonged television time (3 h compared to 1 h per day) was associated with a slightly higher pulse rate in middle-aged females (+0.6 bpm; 95% CI +0.3 to +0.8) and males (+0.9 bpm; 95% CI +0.7 to +1.2). Among participants with a prolonged television time (3 h), those with a high physical activity (level 4) had a lower pulse rate compared to those with a low physical activity (level 1).

CONCLUSIONS

A prolonged television time was associated with a high pulse rate, while high physical activity was associated with a low pulse rate. The results suggest that a high physical activity could compensate for a prolonged television time regarding pulse rate.

Elevated biomarkers of sympatho-adrenomedullary activity linked to e-waste air pollutant exposure in preschool children

Air pollution is a risk factor for cardiovascular disease (CVD), and cardiovascular regulatory changes in childhood contribute to the development and progression of cardiovascular events at older ages. The aim of the study was to investigate the effect of air pollutant exposure on the child sympatho-adrenomedullary (SAM) system, which plays a vital role in regulating and controlling the cardiovascular system. Two plasma biomarkers (plasma epinephrine and norepinephrine) of SAM activity and heart rate were measured in preschool children (n = 228) living in Guiyu, and native (n = 104) and non-native children (n = 91) living in a reference area (Haojiang) for >1 year. Air pollution data, over the 4-months before the health examination, was also collected. Environmental PM_2.5, PM₁₀, SO₂, NO₂ and CO, plasma norepinephrine and heart rate of the e-waste recycling area were significantly higher than for the non-e-waste recycling area. However, there was no difference in plasma norepinephrine and heart rate between native children living in the non-e-waste recycling area and non-native children living in the non-e-waste recycling area. PM_2.5, PM₁₀, SO₂ and NO₂ data, over the 30-day and the 4-month average of pollution before the health examination, showed a positive association with plasma norepinephrine level. PM_2.5, PM₁₀, SO₂, NO₂ and CO concentrations, over the 24 h of the day of the health examination, the 3 previous 24-hour periods before the health examination, and the 24 h after the health examination, were related to increase in heart rate. At the same time, plasma norepinephrine and heart rate on children in the high air pollution level group (≤50-m radius of family-run workshops) were higher than those in the low air pollution level group. Our results suggest that air pollution exposure in e-waste recycling areas could result in an increase in heart rate and plasma norepinephrine, implying e-waste air pollutant exposure impairs the SAM system in children.

Ivabradine Treatment Reduces Cardiomyocyte Apoptosis in a Murine Model of Chronic Viral Myocarditis

This study was designed to explore the effects of ivabradine on cardiomyocyte apoptosis in a murine model of chronic viral myocarditis (CVMC). Mice were inoculated intraperitoneally with Coxsackievirus B3 at days 1, 14, and 28, respectively. On day 42, the mice were gavaged with ivabradine for 30 days until the 72nd day. The heart of infected mice was dilated and a large number of interstitial fibroblasts infiltrated into the myocardium on day 42. Compared with the untreated CVMC mice, mice treated with ivabradine showed a significant reduction in heart rate and less impairment of left ventricular function on day 72. The positive apoptosis of myocardial cells in the untreated CVMC group was significantly higher than that of the normal group and was significantly reduced after treatment with ivabradine. The expression levels of Bax and Caspase-3 in the untreated CVMC group were significantly higher than those of the normal group and were apparently reduced in the ivabradine-treated group versus the untreated CVMC group. Bcl-2 showed a high expression in the normal group and low expression in the untreated CVMC group, but its expression level in the ivabradine-treated group were higher than that of the untreated CVMC group. These results indicate that ivabradine could attenuate the expression of Caspase-3 by downregulation of Bax and upregulation of Bcl-2 to prevent the deterioration of cardiac function resulting from ventricular myocyte loss by cardiomyocyte apoptosis.

Physiological and autonomic stress responses after prolonged sleep restriction and subsequent recovery sleep in healthy young men

Purpose

Sleep restriction is increasingly common and associated with the development of health problems. We investigated how the neuroendocrine stress systems respond to prolonged sleep restriction and subsequent recovery sleep in healthy young men.

Methods

After two baseline (BL) nights of 8 h time in bed (TIB), TIB was restricted to 4 h per night for five nights (sleep restriction, SR, n = 15), followed by three recovery nights (REC) of 8 h TIB, representing a busy workweek and a recovery weekend. The control group (n = 8) had 8 h TIB throughout the experiment. A variety of autonomic cardiovascular parameters, together with salivary neuropeptide Y (NPY) and cortisol levels, were assessed.

Results

In the control group, none of the parameters changed. In the experimental group, heart rate increased from 60 ± 1.8 beats per minute (bpm) at BL, to 63 ± 1.1 bpm after SR and further to 65 ± 1.8 bpm after REC. In addition, whole day low-frequency to-high frequency (LF/HF) power ratio of heart rate variability increased from 4.6 ± 0.4 at BL to 6.0 ± 0.6 after SR. Other parameters, including salivary NPY and cortisol levels, remained unaffected.

Conclusions

Increased heart rate and LF/HF power ratio are early signs of an increased sympathetic activity after prolonged sleep restriction. To reliably interpret the clinical significance of these early signs of physiological stress, a follow-up study would be needed to evaluate if the stress responses escalate and lead to more unfavourable reactions, such as elevated blood pressure and a subsequent elevated risk for cardiovascular health problems.

The effect of exercises on left ventricular systolic and diastolic heart function in sedentary women: Step-aerobic vs core exercises

The purpose of this study is to investigate the effect of 16 weeks step-aerobic exercises and core exercises on left ventricular structure and function with some physiological parameters in sedentary women.

Methods

To achieve the purpose of this study, a total of 45 volunteers including (step-aerobic group (SAG, n = 25), core exercise group (CEG, n = 20) were selected as participants. Two different exercises were applied for 4 days a week, throughout 16 weeks, within 60 minutes for each exercise with the intensity of heart rate (HR) 60-70 percent. The HR was measured using a heart rate monitor for each subject. The physical, biochemical and echocardiographic characteristics of the women were measured before and after the exercise.

Results

During the exercise periods, there were a meaningful decrease in the body weight, BMI, value of waist region and hip circumference of the women in both intervention groups as well as in the values of HR, DBP, SBP (p < 0,05). In addition, serum homocysteine (Hcy) and high-sensitivity C-reactive protein (Hs-CRP) levels decreased and the VO_2max and left ventricular diastolic end-diastolic dimension increased in both SAG and CEG (p < 0.05). The left ventricular diastolic functions of the SAG improved more than CEG. Left ventricular systolic ejection time and fractional shortening meaningfully improved in both SAG and CEG (p < 0.01).

Conclusion

16 weeks of step-aerobic and core exercise showed significant changes of inflammatory and lipid markers with cardiac dimensions and had favorable effects on both left ventricular systolic function. Left ventricular diastolic function had more improved in SAG than the CEG.

Heart rate lowering treatment leads to a reduction in vulnerable plaque features in atherosclerotic rabbits

Objective

To investigate the effect of a heart rate (HR) lowering agent (Ivabradine) on features of atherosclerotic plaque vulnerability with magnetic resonance imaging (MRI), ultrasound imaging, and histology.

Approach and results

Atherosclerosis was induced in the abdominal aorta of 19 rabbits. Nine rabbits were treated with Ivabradine (17 mg/kg/day) during the entire study period. At week 14, imaging was performed. Plaque size was quantified on contrast-enhanced T1-weighted MR images. Microvascular flow, density, and permeability was studied with dynamic contrast-enhanced MRI. Plaque biomechanics was studied by measuring the aortic distension with ultrasound. After, animals were sacrificed and histology was performed.

HR was reduced by 16% (p = 0.026) in Ivabradine-treated animals. No differences in absolute and relative vessel wall beat-to-beat distension were found, but due to the reduction in HR, the frequency of the biomechanical load on the plaque was reduced. Plaque size (MR and histology) was similar between groups. Although microvessel density (histology) was similar between groups, AUC and K^trans, indicative for plaque microvasculature flow, density, and permeability, were decreased by 24% (p = 0.029) and 32% (p = 0.037), respectively. Macrophage content (relative RAM11 positive area) was reduced by 44% (p<0.001) on histology in Ivabradine-treated animals.

Conclusions

HR lowering treatment with Ivabradine in an atherosclerotic rabbit model is associated with a reduction in vulnerable plaque features. The current study suggests that HR reduction may be beneficial for inducing or maintaining a more stable plaque phenotype.

Use of electric field sensors for recording respiration, heart rate, and stereotyped motor behaviors in the rodent home cage

BACKGROUND

Numerous environmental and genetic factors can contribute significantly to behavioral and cardiorespiratory variability observed experimentally. Affordable technologies that allow for noninvasive home cage capture of physio-behavioral variables should enhance understanding of inter-animal variability including after experimental interventions.

NEW METHOD

We assessed whether EPIC electric field sensors (Plessey Semiconductors) embedded within or attached externally to a rodent's home cage could accurately record respiration, heart rate, and motor behaviors.

COMPARISON WITH EXISTING METHODS

Current systems for quantification of behavioral variables require expensive specialty equipment, while measures of respiratory and heart rate are often provided by surgically implanted or chronically affixed devices.

RESULTS

Sensors accurately encoded imposed sinusoidal changes in electric field tested at frequencies ranging from 0.5-100Hz. Mini-metronome arm movements were easily detected, but response magnitude was highly distance dependent. Sensors accurately reported respiration during whole-body plethysmography. In anesthetized rodents, PVC tube-embedded sensors provided accurate mechanical detection of both respiratory and heart rate. Comparable success was seen in naturally behaving animals at rest or sleeping when sensors were attached externally. Video-verified motor behaviors (sniffing, grooming, chewing, and rearing) were detectable and largely separable by their characteristic voltage fluctuations. Larger movement-related events had comparably larger voltage dynamics that easily allowed for a broad approximation of overall motor activity. Spectrograms were used to quickly depict characteristic frequencies in long-lasting recordings, while filtering and thresholding software allowed for detection and quantification of movement-related physio-behavioral events.

CONCLUSIONS

EPIC electric field sensors provide a means for affordable non-contact home cage detection of physio-behavioral variables.

Who benefits more from hemodynamically guided hypotensive therapy? The experience from two randomized, prospective and controlled trials

OBJECTIVES

Arterial hypertension (AH) may be related to fluid retention, increased vascular resistance or hyperdynamic heart function. Impedance cardiography (ICG) is shown to be useful in the individualization of antihypertensive therapy but little is known about who most benefits from this therapeutic approach. The aim of this analysis was to estimate the effectiveness of ICG-guided antihypertensive therapy with respect to baseline blood pressure (BP) from the perspective of 12 weeks' observation in randomized, prospective and controlled trials.

METHODS

This analysis involved 272 patients (average age: 44.1 ± 10.8 years) with AH. After baseline evaluation, including: office BP measurement (systolic, SBP; diastolic, DBP; mean, MBP) and ambulatory BP monitoring (mean 24-h SBP, mean 24-h DBP) the subjects were randomly assigned to groups of empiric [GE] and ICG-guided antihypertensive therapy [HD]. The results were evaluated separately in subgroups derived from median of MBP (110 mmHg): with slightly increased ('SI_BP') and more increased BP ('MI_BP'). The comparative analysis included absolute change in BP (d_OSBP, d_ODBP, d_24-h SBP, d_24-h DBP) and the percentage of patients with reduction of BP ⩾ 10 mmHg (d10_OSBP, d10_ODBP, d10_24-h SBP, d10_24-h DBP).

RESULTS

ICG-guided therapy was shown to be superior to the empiric approach, especially in MI_BP. In this subgroup, the BP reduction in HD was higher than in GE: d_OSBP (23.3 ± 10.8 versus 18.5 ± 13.9 mmHg; p = 0.035), d_ODBP (16.0 ± 6.3 versus 11.6 ± 9.6 mmHg; p = 0.003), d_24-h SBP (17.7 ± 10.8 versus 13.1 ± 13.1 mmHg; p = 0.035). This benefit was also confirmed by a higher percentage of patients with significant BP reduction: d10_OSBP (87.7% versus 69.1%; p = 0.012), d10_ODBP (69.2% versus 47.3%; p = 0.012) and d10_24-h SBP (72.3% versus 52.7%; p = 0.012). The comparison in the SI_BP subgroup did not reveal such significant differences.

CONCLUSIONS

The hemodynamically guided pharmacotherapy results in greater BP reduction. This effect is more pronounced in patients with higher baseline BP, while in those with slightly increased BP the empiric approach seems comparable to ICG.

The relation of ambulatory heart rate with all-cause mortality among middle-aged men: a prospective cohort study

The aim of this study was to investigate the association between average 24-hour ambulatory heart rate and all-cause mortality, while adjusting for resting clinical heart rate, cardiorespiratory fitness, occupational and leisure time physical activity as well as classical risk factors. A group of 439 middle-aged male workers free of baseline coronary heart disease from the Belgian Physical Fitness Study was included in the analysis. Data were collected by questionnaires and clinical examinations from 1976 to 1978. All-cause mortality was collected from the national mortality registration with a mean follow-up period of 16.5 years, with a total of 48 events. After adjustment for all before mentioned confounders in a Cox proportional hazards regression analysis, a significant increased risk for all-cause mortality was found among the tertile of workers with highest average ambulatory heart rate compared to the tertile with lowest ambulatory heart rate (Hazard ratio = 3.21, 95% confidence interval: 1.22–8.44). No significant independent association was found between resting clinic heart rate and all-cause mortality. The study indicates that average 24-hour ambulatory heart rate is a strong predictor of all-cause mortality independent from resting clinic heart rate, cardiorespiratory fitness, occupational and leisure time physical activity and other classical risk factors among healthy middle-aged workers.

Physical activity and resting pulse rate in older adults: findings from a randomized controlled trial

BACKGROUND

Elevated resting pulse rate (RPR) is a well-recognized risk factor for adverse outcomes. Epidemiological evidence supports the beneficial effects of regular exercise for lowering RPR, but studies are mainly confined to persons younger than 65 years. We set out to evaluate the utility of a physical activity (PA) intervention for slowing RPR among older adults.

METHODS

A total of 424 seniors (ages 70-89 years) were randomized to a moderate intensity PA intervention or an education-based "successful aging" health program. Resting pulse rate was assessed at baseline, 6 months, and 12 months. Longitudinal differences in RPR were evaluated between treatment groups using generalized estimating equation models, reporting unstandardized β coefficients with robust SEs.

RESULTS

Increased frequency and duration of aerobic training were observed for the PA group at 6 and 12 months as compared with the successful aging group (P < .001). In both groups, RPR remained unchanged over the course of the 12-month study period (P = .67). No significant improvement was observed (β [SE] = 0.58 [0.88]; P = .51) for RPR when treatment groups were compared using the generalized estimating equation method. Comparable results were found after omitting participants with a pacemaker, cardiac arrhythmia, or who were receiving β-blockers.

CONCLUSIONS

Twelve months of moderate intensity aerobic training did not improve RPR among older adults. Additional studies are needed to determine whether PA of longer duration and/or greater intensity can slow RPR in older persons.

Variation in resting heart rate over 4 years and the risks of myocardial infarction and death among older adults

OBJECTIVE

Resting heart rate (RHR) is an established predictor of myocardial infarction (MI) and mortality, but the relationship between variation in RHR over a period of several years and health outcomes is unclear. We evaluated the relationship between long-term variation in RHR and the risks of incident MI and mortality among older adults.

METHODS

1991 subjects without cardiovascular disease from the Cardiovascular Health Study were included. RHR was taken from resting ECGs at the first five annual study visits. RHR mean, trend and variation were estimated with linear regression. Subjects were followed for incident MI and death until December 2010. HRs for RHR mean, trend and variation are reported for differences of 10 bpm, 2 bpm/year and 2 bpm, respectively.

RESULTS

262 subjects had an incident MI event (13%) and 1326 died (67%) during 12 years of median follow-up. In primary analyses adjusted for cardiovascular risk factors, RHR mean (HR 1.12; 95% CI 1.05 to 1.20) and variation (HR 1.08; 95% CI 1.03 to 1.13) were associated with the risk of death while trend was not. None of the RHR variables were significantly associated with the risk of incident MI events; however, CIs were wide and the MI associations with RHR variables were not significantly different from the mortality associations. Adjusting for additional variables did not affect estimates, and there were no significant interactions with sex.

CONCLUSIONS

Variation in RHR over a period of several years represents a potential predictor of long-term mortality among older persons free of cardiovascular disease.

Metabolic syndrome is associated with and predicted by resting heart rate: a cross-sectional and longitudinal study

OBJECTIVE

Although higher resting heart rate (RHR) has emerged as a predictor for lifespan, the underlying mechanisms remain obscure. The present study investigates whether a positive relationship exists between RHR and metabolic syndrome (MetS) and whether RHR predicts future MetS.

METHODS

A cohort of 89,860 participants were surveyed during 2006-2007 in Kailuan/Tangshan, China. MetS was diagnosed when a participant presented at least three of the following: abdominal adiposity, low high density lipoprotein-cholesterol, high triglycerides, hypertension or impaired fasting glucose. RHR was derived from ECG recordings and subjects were stratified based on RHR. Some participants without MetS at baseline were followed-up for 4 years.

RESULTS

At baseline, 23,150 participants (25.76%) had MetS. There was a positive association between RHR and MetS. The OR of having MetS was 1.49 (95% CI 1.32 to 1.69) in subjects with RHR at 95-104 compared with those at 55-64 beats per minute (bpm) (reference), after adjusting for variables including age, sex, education, cigarette smoking, alcohol drinking, physical activities, body mass index, hypertension, diabetes, hyperlipidaemia, inflammatory biomarkers and renal function. More importantly, when 43,725 individuals from the original study without MetS at baseline were followed-up, higher RHR was found to predict greater risk of MetS incidence. The OR of developing MetS 4 years later was 1.41 (95% CI 1.21 to 1.65) in subjects with RHR at 95-104 bpm compared with reference, after all adjustments.

CONCLUSIONS

Our cross-sectional and longitudinal findings provide evidence that RHR is an independent risk factor for existing MetS and a powerful predictor for future incidence of MetS.

Novel association of the obesity risk-allele near Fas Apoptotic Inhibitory Molecule 2 (FAIM2) gene with heart rate and study of its effects on myocardial infarction in diabetic participants of the PREDIMED trial

BACKGROUND

The Fas apoptotic pathway has been implicated in type 2 diabetes and cardiovascular disease. Although a polymorphism (rs7138803; G > A) near the Fas apoptotic inhibitory molecule 2 (FAIM2) locus has been related to obesity, its association with other cardiovascular risk factors and disease remains uncertain.

METHODS

We analyzed the association between the FAIM2-rs7138803 polymorphism and obesity, blood pressure and heart rate in 7,161 participants (48.3% with type 2 diabetes) in the PREDIMED study at baseline. We also explored gene-diet interactions with adherence to the Mediterranean diet (MedDiet) and examined the effects of the polymorphism on cardiovascular disease incidence per diabetes status after a median 4.8-year dietary intervention (MedDiet versus control group) follow-up.

RESULTS

We replicated the association between the FAIM2-rs7138803 polymorphism and greater obesity risk (OR: 1.08; 95% CI: 1.01-1.16; P = 0.011; per-A allele). Moreover, we detected novel associations of this polymorphism with higher diastolic blood pressure (DBP) and heart rate at baseline (B = 1.07; 95% CI: 0.97-1.28 bmp in AA vs G-carriers for the whole population), that remained statistically significant even after adjustment for body mass index (P = 0.012) and correction for multiple comparisons. This association was greater and statistically significant in type-2 diabetic subjects (B = 1.44: 95% CI: 0.23-2.56 bmp; P = 0.010 for AA versus G-carriers). Likewise, these findings were also observed longitudinally over 5-year follow-up. Nevertheless, we found no statistically significant gene-diet interactions with MedDiet for this trait. On analyzing myocardial infarction risk, we detected a nominally significant (P = 0.041) association in type-2 diabetic subjects (HR: 1.86; 95% CI:1.03-3.37 for AA versus G-carriers), although this association did not remain statistically significant following correction for multiple comparisons.

CONCLUSIONS

We confirmed the FAIM2-rs7138803 relationship with obesity and identified novel and consistent associations with heart rate in particular in type 2 diabetic subjects. Furthermore, our results suggest a possible association of this polymorphism with higher myocardial infarction risk in type-2 diabetic subjects, although this result needs to be replicated as it could represent a false positive.

Exercise in a healthy heart program: a cohort study

OBJECTIVE

To assess the effects of exercise on resting heart rate (RHR), weight, lipid profile, and blood pressure. We hypothesized that the participants who increased their physical activity would show improvement in their cardiovascular risk factors compared to those who did not.

DESIGN

Retrospective chart review over the mean duration of 4.9 years of follow-up.

SETTING

Healthy Heart Program Prevention Clinic at St. Paul's Hospital, Vancouver, British Columbia, Canada.

PARTICIPANTS

We reviewed 300 charts of patients randomly selected from those who attended the Prevention Clinic between 1984 and 2009. 248 (82.7%) patients were referred for primary prevention and 52 (17.3%) for secondary prevention.

PRIMARY AND SECONDARY OUTCOME MEASURES

Weight, RHR, lipid profile, and blood pressure were recorded at the initial and last visit.

RESULTS

During a mean of 4.9 years of follow-up, 55% of participants improved their exercise. The mean decrease in the RHR for these patients (group 1) was 5.9 beats per minute (bpm) versus the mean increase of 0.3 bpm for the "no change" group (group 2) (P < 0.01). The mean net weight increase in group 1 was 0.06 kg/year versus 0.25 kg/year in group 2. Because of medications, all patients had a significant improvement in their lipid profiles. Furthermore, there was a statistically significant greater reduction in Framingham Risk Score (FRS) in group 1 versus group 2 (11.8% versus 15.1%, P < 0.01).

CONCLUSION

Participation in the program significantly reduces modifiable risk factors for cardiovascular disease. Improved exercise regimen results in lower RHR and greater reduction in FRS. However, even in a Prevention Program, despite strong advocacy of the importance of exercise, a significant percentage of participants does not improve their exercise habits.

Omega-3 fatty acid supplementation reduces resting heart rate of rats with epilepsy

Since cardiovascular dysfunction may contribute to sudden unexpected death in epilepsy (SUDEP), the consumption of omega-3 fatty acids (omega-3 FAs) might be beneficial as an adjunctive therapy for SUDEP prevention. It is well recognized that omega-3 FAs exert positive effects on the cardiovascular system including heart rate (HR) reduction, a major risk factor to sudden death. Thus, we evaluated the effects of chronic supplementation of omega-3 FAs on the HR of rats with epilepsy. In agreement with our previous investigations, this study also showed that the HR of animals with epilepsy is higher than that of the control group. Quite interestingly, chronic supplementation with omega-3 FAs restored the HR of rats with epilepsy toward control values. In conclusion, although further investigations are still required, our preliminary results showed a potential preventive effect of omega-3 FA supplementation against SUDEP.

Examining the relationship between exercise tolerance and isoproterenol-based cardiac reserve in murine models of heart failure

The loss of cardiac reserve is, in part, responsible for exercise intolerance in late-stage heart failure (HF). Exercise tolerance testing (ETT) has been performed in mouse models of HF; however, treadmill performance and at-rest cardiac indexes determined by magnetic resonance imaging (MRI) rarely correlate. The present study adopted a stress-MRI technique for comparison with ETT in HF models, using isoproterenol (ISO) to evoke cardiac reserve responses. Male C57BL/6J mice were randomly subjected to myocardial infarction (MI), transverse aortic constriction (TAC), or sham surgery under general anesthesia. Mice underwent serial ETT on a graded treadmill with follow-up ISO stress-MRI. TAC mice showed consistent exercise intolerance, with a 16.2% reduction in peak oxygen consumption vs. sham at 15-wk postsurgery (WPS). MI and sham mice had similar peak oxygen consumption from 7 WPS onward. Time to a respiratory exchange ratio of 1.0 correlated with ETT distance ( r = 0.64; P < 0.001). The change in ejection fraction under ISO stress was reduced in HF mice at 4 WPS [10.1 ± 3.9% change (Δ) and 8.9 ± 3.5%Δ in MI and TAC, respectively, compared with 32.0 ± 3.5%Δ in sham; P < 0.001]. However, cardiac reserve differences between surgery groups were not observed at 16 WPS in terms of ejection fraction or cardiac output. In addition, ETT did not correlate with cardiac indexes under ISO stress. In conclusion, ISO stress was unable to reflect consistent differences in ETT between HF and healthy mice, suggesting cardiac-specific indexes are not the sole factors in defining exercise intolerance in mouse HF models.

Elevated resting heart rate, physical fitness and all-cause mortality: a 16-year follow-up in the Copenhagen Male Study

Objective

To examine whether elevated resting heart rate (RHR) is an independent risk factor for mortality or a mere marker of physical fitness (VO₂Max).

Methods

This was a prospective cohort study: the Copenhagen Male Study, a longitudinal study of healthy middle-aged employed men. Subjects with sinus rhythm and without known cardiovascular disease or diabetes were included. RHR was assessed from a resting ECG at study visit in 1985–1986. VO₂Max was determined by the Åstrand bicycle ergometer test in 1970–1971. Subjects were classified into categories according to level of RHR. Associations with mortality were studied in multivariate Cox models adjusted for physical fitness, leisure-time physical activity and conventional cardiovascular risk factors.

Results

2798 subjects were followed for 16 years. 1082 deaths occurred. RHR was inversely related to physical fitness (p<0.001). Overall, increasing RHR was highly associated with mortality in a graded manner after adjusting for physical fitness, leisure-time physical activity and other cardiovascular risk factors. Compared to men with RHR ≤50, those with RHR >90 had an HR (95% CI) of 3.06 (1.97 to 4.75). With RHR as a continuous variable, risk of mortality increased with 16% (10–22) per 10 beats per minute (bpm). There was a borderline interaction with smoking (p=0.07); risk per 10 bpm increase in RHR was 20% (12–27) in smokers, and 14% (4–24) in non-smokers.

Conclusions

Elevated RHR is a risk factor for mortality independent of physical fitness, leisure-time physical activity and other major cardiovascular risk factors.

Increased night heart rate is associated with worse large artery elasticity in chronic kidney disease patients

BACKGROUND

Chronic kidney disease (CKD) is associated with high overall and cardiovascular mortality. Numerous studies have reported that increased heart rate is a risk factor for all-cause mortality. We investigated the link between sleep heart rate and artery stiffness in CKD patients.

METHODS

In a cross-sectional study, we enrolled 100 prevalent Chinese CKD patients (55 males, aged 52.5 ± 16.40 years). Heart rate was measured with an automatic system. Arterial stiffness was evaluated by using a calibrated tonometer.

RESULTS

Large artery elasticity index (LAEI) was positively correlated with body mass index and hemoglobin but negatively associated with age and systolic blood pressure. Furthermore, LAEI was negatively associated with glomerular filtration rate (GFR) and sleep heart rate. In multivariate regression, LAEI was independently predicted by SBP, BMI, age, sleep heart rate, and gender. Adjusted R (2) of the model was 0.486.

CONCLUSION

Elevated sleep heart rate is significantly associated with increased arterial stiffness in CKD patients. Further investigation is needed to explore the potential benefits of sleep heart rate lowering therapy in this patient group.

A "patient-tailored" treatment of hypertension with use of impedance cardiography: a randomized, prospective and controlled trial

Background

Arterial hypertension might be caused by hemodynamic disturbances such as fluid retention, increased vascular resistance, and hyperdynamic function of the heart. The aim of this study was to estimate the effectiveness of antihypertensive therapy based on hemodynamic assessment by impedance cardiography in a randomized, prospective, controlled trial.

Material/Methods

This study involved 128 patients (average age: 42.9±11.1 years) with arterial hypertension, randomized into groups: (1) empiric, and (2) hemodynamic, in which treatment choice considered impedance cardiography results. Evaluation of treatment effects was performed after 12 weeks and included office blood pressure measurement and ambulatory blood pressure monitoring.

Results

All final blood pressure values were lower in the hemodynamic group, significantly for office systolic blood pressure (empiric vs. hemodynamic: 136.1 vs. 131.6 mmHg; p=0.036) and diastolic blood pressure (87.0 vs. 83.7 mmHg; p=0.013), as well as night-time systolic blood pressure (121.3 vs. 117.2 mmHg; p=0.023) and diastolic blood pressure (71.9 vs. 68.4 mmHg; p=0.007). Therapy based on impedance cardiography significantly increased the reduction in office systolic blood pressure (11.0 vs. 17.3 mmHg; p=0.008) and diastolic blood pressure (7.7 vs. 12.2 mmHg; p=0.0008); as well as 24-h mean systolic blood pressure (9.8 vs. 14.2 mmHg; p=0.026), daytime systolic blood pressure (10.5 vs. 14.8 mmHg; p=0.040), and night-time systolic blood pressure (7.7 vs. 12.2 mmHg; p=0.032).

Conclusions

Antihypertensive treatment based on impedance cardiography can significantly increase blood pressure reduction in hypertensive patients.

Synergistic effects of serum uric acid and cardiometabolic risk factors on early stage atherosclerosis: the cardiometabolic risk in Chinese study

OBJECTIVE

To comprehensively examine the associations of serum uric acid (SUA) with central and peripheral arterial stiffness in Chinese adults, and particularly assess the interactions between SUA and other cardiometabolic risk factors.

METHODS

The study included 3,772 Chinese men and women with carotid radial pulse wave velocity (crPWV), carotid femoral PWV (cfPWV), carotid artery dorsalis pedis PWV (cdPWV) and SUA measured.

RESULTS

After adjustment for age, sex, and BMI, the levels of SUA were significantly associated with increasing trend of cfPWV, crPWV and cdPWV (P for trend <0.0001). Further adjustment for heart rate (HR), blood pressure (BP) and lipids attenuated the associations with crPWV and cdPWV to be non-significant (P = 0.1, P = 0.099 respectively), but the association between SUV and cfPWV remained significant (P = 0.004). We found significant interactions between SUA and HR or BP in relation to cfPWV (P for interaction = 0.03, 0.003 respectively). The associations between SUA and cfPWV were more evident among individuals with higher HR or normal BP than those with lower HR or hypertension.

CONCLUSIONS

SUA was associated with elevated aortic arterial stiffness in Chinese adults, independent of conventional cardiovascular risk factors. BP and HR might modify the deleterious effects of SUA.

Cardiovascular risk in a rural adult West African population: is resting heart rate also relevant?

INTRODUCTION

Elevated resting heart rate (RHR) is a neglected marker in cardiovascular risk factor studies of sub-Saharan African populations. This study aimed to determine the prevalence of elevated RHR and other risk factors for cardiovascular disease (CVD) and to investigate any associations between RHR and these risk factors in a rural population in Ghana.

DESIGN

Cross-sectional analysis.

METHODS

A total of 574 adults aged between 18-65 years were randomly sampled from a population register. Data collected included those on sociodemographic variables and anthropometric, blood pressure (BP), and RHR measurements. Within-person variability in RHR was calculated using data from repeat measurements taken 2 weeks apart.

RESULTS

Of study participants, 36% were male. Prevalence of casual high BP was 19%. In the population, 10% were current cigarette smokers and habitual alcohol use was high at 56%. As measured by body mass index, 2% were obese and 14% had abdominal obesity. RHR was elevated (>90 bpm) in 19%. Overall, 79% of study participants were found to have at least one CVD risk factor. RHR was significantly associated with age, waist circumference, and BP. Individuals with an elevated RHR had a higher risk (OR 1.94, 95% CI 1.15-3.26%, p = 0.013) of casual high BP compared with participants with normal RHR independently of several established CVD risk factors. The regression dilution ratio of RHR was 0.75 (95% CI 0.62-0.89).

CONCLUSIONS

Significant associations were observed between RHR and several established cardiovascular risk factors. Prospective studies are needed in sub-Saharan African populations to establish the potential value of RHR in cardiovascular risk assessment.

A prospective population study of resting heart rate and peak oxygen uptake (the HUNT Study, Norway)

Objectives

We assessed the prospective association of resting heart rate (RHR) at baseline with peak oxygen uptake (VO_2peak) 23 years later, and evaluated whether physical activity (PA) could modify this association.

Background

Both RHR and VO_2peak are strong and independent predictors of cardiovascular morbidity and mortality. However, the association of RHR with VO_2peak and modifying effect of PA have not been prospectively assessed in population studies.

Methods

In 807 men and 810 women free from cardiovascular disease both at baseline (1984–86) and follow-up 23 years later, RHR was recorded at both occasions, and VO_2peak was measured by ergospirometry at follow-up. We used Generalized Linear Models to assess the association of baseline RHR with VO_2peak, and to study combined effects of RHR and self-reported PA on later VO_2peak.

Results

There was an inverse association of RHR at baseline with VO_2peak (p<0.01). Men and women with baseline RHR greater than 80 bpm had 4.6 mL·kg⁻¹·min⁻¹ (95% confidence interval [CI], 2.8 to 6.3) and 1.4 mL·kg⁻¹·min⁻¹ (95% CI, −0.4 to 3.1) lower VO_2peak at follow-up compared with men and women with RHR below 60 bpm at baseline. We found a linear association of change in RHR with VO_2peak (p = 0.03), suggesting that a decrease in RHR over time is likely to be beneficial for cardiovascular fitness. Participants with low RHR and high PA at baseline had higher VO_2peak than inactive people with relatively high RHR. However, among participants with relatively high RHR and high PA at baseline, VO_2peak was similar to inactive people with relatively low RHR.

Conclusion

RHR is an important predictor of VO_2peak, and serial assessments of RHR may provide useful and inexpensive information on cardiovascular fitness. The results suggest that high levels of PA may compensate for the lower VO_2peak associated with a high RHR.

The "funny" current (I(f)) inhibition by ivabradine at membrane potentials encompassing spontaneous depolarization in pacemaker cells

Recent clinical trials have shown that ivabradine (IVA), a drug that inhibits the funny current (I(f)) in isolated sinoatrial nodal cells (SANC), decreases heart rate and reduces morbidity and mortality in patients with cardiovascular diseases. While IVA inhibits I(f), this effect has been reported at essentially unphysiological voltages, i.e., those more negative than the spontaneous diastolic depolarization (DD) between action potentials (APs). We tested the relative potency of IVA to block I(f) over a wide range of membrane potentials, including those that encompass DD governing to the SANC spontaneous firing rate. A clinically relevant IVA concentration of 3 μM to single, isolated rabbit SANC slowed the spontaneous AP firing rate by 15%. During voltage clamp the maximal I(f) was 18 ± 3 pA/pF (at -120 mV) and the maximal I(f) reduction by IVA was 60 ± 8% observed at -92 ± 4 mV. At the maximal diastolic depolarization (~-60 mV) I(f) amplitude was only -2.9 ± 0.4 pA/pF, and was reduced by only 41 ± 6% by IVA. Thus, I(f) amplitude and its inhibition by IVA at physiologically relevant membrane potentials are substantially less than that at unphysiological (hyperpolarized) membrane potentials. This novel finding more accurately describes how IVA affects SANC function and is of direct relevance to numerical modeling of SANC automaticity.

Comparison of 24-hour cardiovascular and autonomic function in paraplegia, tetraplegia, and control groups: implications for cardiovascular risk

BACKGROUND

Fluctuations in 24-hour cardiovascular hemodynamics, specifically heart rate (HR) and blood pressure (BP), are thought to reflect autonomic nervous system (ANS) activity. Persons with spinal cord injury (SCI) represent a model of ANS dysfunction, which may affect 24-hour hemodynamics and predispose these individuals to increased cardiovascular disease risk.

OBJECTIVE

To determine 24-hour cardiovascular and ANS function among individuals with tetraplegia (n=20; TETRA: C4-C8), high paraplegia (n=10; HP: T2-T5), low paraplegia (n=9; LP: T7-T12), and non-SCI controls (n=10). Twenty-four-hour ANS function was assessed by time domain parameters of heart rate variability (HRV); the standard deviation of the 5-minute average R-R intervals (SDANN; milliseconds/ms), and the root-mean square of the standard deviation of the R-R intervals (rMSSD; ms). Subjects wore 24-hour ambulatory monitors to record HR, HRV, and BP. Mixed analysis of variance (ANOVA) revealed significantly lower 24-hour BP in the tetraplegic group; however, BP did not differ between the HP, LP, and control groups. Mixed ANOVA suggested significantly elevated 24-hour HR in the HP and LP groups compared to the TETRA and control groups (P<0.05); daytime HR was higher in both paraplegic groups compared to the TETRA and control groups (P<0.01) and nighttime HR was significantly elevated in the LP group compared to the TETRA and control groups (P<0.01). Twenty-four-hour SDANN was significantly increased in the HP group compared to the LP and TETRA groups (P<0.05) and rMSSD was significantly lower in the LP compared to the other three groups (P<0.05). Elevated 24-hour HR in persons with paraplegia, in concert with altered HRV dynamics, may impart significant adverse cardiovascular consequences, which are currently unappreciated.

Usefulness of physical fitness and the metabolic syndrome to predict vascular disease risk in older Chinese (from the Guangzhou Biobank Cohort Study-Cardiovascular Disease Subcohort [GBCS-CVD])

Physical fitness can independently lower the risk of cardiovascular disease (CVD). We explored the independent and combined associations of physical fitness, measured using the seated at rest heart rate (RHR), and the metabolic syndrome (MS), with CVD risk, as described by an elevated pulse wave velocity (PWV) in older Chinese. Data from 1,996 participants were drawn from the Guangzhou Biobank Cohort Study-Cardiovascular Disease Subcohort. Analysis of variance and logistic regression analysis were used to establish the independent and combined associations of the RHR and the MS with PWV. The RHR was independently associated with an elevated PWV (odds ratio [OR] 1.63, 95% confidence interval [CI] 1.22 to 2.18), as was the MS (OR 2.36, 95% CI 1.76 to 3.17). The participants with a high RHR, but without the MS, had an adjusted OR of 1.63 (95% CI 1.15 to 2.30) for the presence of the CVD proxy. Those with a low RHR and the MS had an adjusted OR of 2.35 (95% CI 1.66 to 3.33). The risk of an elevated PWV increased almost fourfold with both a high RHR and a diagnosis of the MS (OR 3.87, 95% CI 2.39 to 6.28, p = 0.52 for interaction). In conclusion, physical fitness, measured using the RHR, and the MS are independently associated with an elevated PWV, a surrogate marker for CVD. The strength of this association was further increased in the presence of both. These findings confirm the beneficial effects of physical fitness on attenuating the risk of CVD among older Chinese.

The prognostic significance of heart rate for cardiovascular disease and hypertension

Five decades ago, hypertension was a debated risk factor for the development of cardiovascular disease. After further studies and the introduction of antihypertensive medications, few, if any, have doubted the important role hypertension plays as a cardiovascular risk factor. Today, a growing body of evidence emphasizes the relationship between heart rate and hypertension, and heart rate and cardiovascular disease, which makes the measurement of heart rate an important component of the cardiovascular risk assessment. Current European guidelines for managing arterial hypertension recommend the measurement of heart rate for risk stratification, but there still are no recommendations for treatment. This review discusses the evidence for a relationship between heart rate and cardiovascular mortality and morbidity and hypertension.

Resting heart rate is associated with cardiovascular and all-cause mortality after adjusting for inflammatory markers: the Copenhagen City Heart Study

AIMS

To investigate the association between resting heart rate (RHR) and markers of chronic low-grade inflammation. Also, to examine whether elevated resting heart rate is independently associated with cardiovascular and all-cause mortality in the general population, or whether elevated RHR is merely a marker of chronic low-grade inflammation.

METHODS AND RESULTS

A group of 6518 healthy subjects from the the Danish general population were followed for 18 years during which 1924 deaths occurred. Subjects underwent assessment of baseline RHR, conventional cardiovascular risk factors, high-sensitivity C-reactive protein (hsCRP), and fibrinogen. RHR was associated with hsCRP and fibrinogen in uni- and multivariate models (p < 0.0001). A 10 beats per minute increase in RHR was associated with increased cardiovascular and all-cause mortality in univariate models - HR (95%CI) (1.21 (1.14-1.29) and 1.15 (1.11-1.19); multivariate models adjusted for conventional risk factors - 1.16 (1.09-1.24) and 1.10 (1.06-1.14); multivariate models including hsCRP - 1.14 (1.07-1.22) and 1.09 (1.05-1.14); fibrinogen - 1.15 (1.07-1.22) and 1.09 (1.05-1.14); and both hsCRP and fibrinogen - 1.14 (1.07-1.22) and 1.09 (1.05-1.14).

CONCLUSION

RHR was associated with markers of chronic low-grade inflammation. However, RHR remained associated with both cardiovascular and all-cause mortality after adjusting for markers of chronic low-grade inflammation. This suggests that RHR is an independent risk factor for cardiovascular and all-cause mortality, and not merely a marker of chronic low-grade inflammation.

Resting heart rate, mortality and future coronary heart disease in the elderly: the 3C Study

OBJECTIVES

To investigate the association between resting heart rate (RHR) and mortality and incident coronary heart disease (CHD) in the elderly.

METHODS

Data derived from the Three-City Study, a French multicentre prospective study including 9294 community-dwelling elderly subjects aged ≥65 years at baseline examination between 1999 and 2001. The study population comprised 7147 participants (61% women) who were free of a pacemaker or any cardiac arrhythmias at baseline. RHR was measured twice at baseline in a seated position using an electronic tensiometer. Participants were then followed up bi-annually for vascular morbidity and mortality over 6 years. CHD events and cardiovascular death were adjudicated by an independent expert committee.

RESULTS

After 6 years of follow-up, 615 subjects died including 17.9% from cardiovascular causes. Subjects from the top quintile of RHR (>79 bpm) had respectively a 74% (95% CI, 1.3-2.3), a 87% (95% CI: 0.98-3.6, p = 0.06) and a 72% (95% CI, 1.3-2.3) increased risk of total, cardiovascular and non-cardiovascular mortality compared to those from the lowest quintile (<62 bpm), after adjustment for cardiovascular risk factors and beta-blocker (BB) use in a Cox regression analysis. Associations with total mortality were consistent according to age, gender, BB use, diabetes and hypertension status (all p values for interaction >0.10). Conversely, RHR was not predictive of incident CHD (n = 228 events; top vs lowest quintile: HR: 1.0; 95% CI: 0.6-1.5).

CONCLUSIONS

RHR is an independent risk marker of mortality but not of incident CHD events in community-dwelling elderly. Its routine measurement may help identify those who are at increased risk of mortality in the short term.

Elevated resting heart rate is associated with greater risk of cardiovascular and all-cause mortality in current and former smokers

BACKGROUND

Elevated resting heart rate is associated with mortality in general populations. Smokers may be at particular risk. The association between resting heart rate (RHR), smoking status and cardiovascular and total mortality was investigated in a general population.

METHODS

Prospective study of 16,516 healthy subjects from the Copenhagen City Heart Study. 8709 deaths, hereof 3821 cardiovascular deaths, occurred during 33 years of follow-up.

RESULTS

In multivariate Cox models with time-dependent covariates RHR was significantly associated with both cardiovascular and total mortality. Current and former smokers had, irrespective of tobacco consumption, greater relative risk of elevated RHR compared to never smokers. The relative risk of all-cause mortality per 10 bpm increase in RHR was (95% CI): 1.06 (1.01-1.10) in never smokers, 1.11 (1.07-1.15) in former smokers, 1.13 (1.09-1.16) in moderate smokers, and 1.13 (1.10-1.16) in heavy smokers. There was no gender difference. The risk estimates for cardiovascular and all-cause mortality were essentially similar. In univariate analyses, the difference in survival between a RHR in the highest (> 80 bpm) vs lowest quartile (< 65 bpm) was 4.7 years in men and 3.6 years in women. In multivariate analyses, the difference was about one year in never smokers and about two years in current and former smokers.

CONCLUSIONS

In a healthy population resting heart rate is associated with total and cardiovascular mortality. Elevated resting heart rate is associated with greater risk in subjects with a history of smoking than in never smokers.

{beta}-Adrenoceptor gene variation and intermediate physiological traits: prediction of distant phenotype

Intermediate physiological phenotype is the genetic and environmental influence on functional physiological characteristics with direct prognostic relevance to distant, more complex phenotypes, such as cardiovascular and metabolic disease. Increasingly available and affordable genotyping techniques have created an explosion of information on candidate gene variation and its relationship to intermediate physiological traits. Variation in beta-adrenoceptor genes is an intense focus of investigation because beta-adrenoceptors are: (1) ubiquitous in organ system distribution; (2) integral to a multitude of physiological processes; (3) well described in cardiovascular and metabolic disease; and (4) major pharmacological treatment targets. Furthermore, knowledge of functional gene variants in these receptors predates the description of the human genome. This review highlights the influence of common gene variation in the three beta-adrenoceptor subtypes on intermediate physiological phenotype predictive of cardiovascular disease and obesity. Although further information is needed to replicate this information across populations, this review condenses and summarizes growing trends in specific pleiotropic effects of beta-adrenoceptor polymorphisms and suggests which variants may be predictive of distant phenotype.