Autonomic Control of the Aging Heart

Heart Rhythm Harmony Becomes Discordant as We Age

Heartbeats are initiated by pacemaker cells within the sinoatrial node (SAN) that generate spontaneous impulses at intervals that resonate around a preferred mean frequency. A coupled-clock system (CCS) intrinsic to individual pacemaker cells, that is modulated by autonomic input, drives SAN normal automaticity. Subcellular and cell-wide mechanisms within the CCS are in "dynamic equilibrium," and never achieve a true steady state. Nanoscale electromagnetic "vibrations" caused by mechanisms intrinsic to the CCS and their autonomic modulation create heartbeat rhythm, ("heartbeat music"). A "Heart-Brain Grand Symphony" (HBGS), that emerges from this "beautiful noise" as the heart beats, is broadcast to the body surface, and its numerous motifs within the symphony can be experienced by tuning into electrocardiogram (EKG) RR-interval variability rhythms. As age increases, one or more of the components of physiologic coupling within the neuroautonomic regulatory sinus node and atrial networks begins to deteriorate, and cacophony emerges within the HBGS, manifested by reductions in the mean rate and rhythm at which the CCS within SAN cells fires action potentials. These subclinical changes in SAN structure and function as age advances become "partners" with pathophysiology that defines clinical SAN and other cardiac tissue diseases, e.g., Sick Sinus Syndrome and atrial fibrillation, and as such age-associated changes in SAN structure and function are co-morbidities of these clinical cardiac diseases. In other terms as age advances, sub-clinical age-associated changes in SAN structure and function, per se, are major shareholders in SAN disease enterprises.

Normative values of short-term heart rate variability in a cross-sectional study of a Danish population. The DanFunD study

AIMS

The autonomic nervous system includes parasympathetic and sympathetic components that monitor and regulate most of the bodily functions and play a central role in the physiology and homeostasis of the human body. Heart rate variability is a non-invasive tool for quantification of rhythmic fluctuations in heart rate that reflects the function of the autonomic nervous system. The study aims to describe the heart rate variability distribution in the general population, stratified in sex and age groups, which is currently insufficiently described.

METHODS

A cross-sectional population-based study recruited participants in 10 municipalities in the western part of the greater Copenhagen area in Denmark, including 6891 men and women aged 18-72 years (participation rate was 29.5%). Short-term heart rate variability measures were obtained and related to age and gender.

RESULTS

Both time and frequency domain measures showed a huge variation in the different sex and age groups. Women had a higher median heart rate than men, and the association with age was U-shaped. Measures indicating a predominance of the parasympathetic component in relation to the sympathetic component were more frequent in women and younger age groups.

CONCLUSIONS

Both sex and age influence the heart rate variability in this adult Danish population. Therefore, our age- and sex-related reference values of heart rate variability in the time and frequency domain should be used in further epidemiological and clinical research.

Putting back respiration into respiratory sinus arrhythmia or high-frequency heart rate variability: Implications for interpretation, respiratory rhythmicity, and health

Research on respiratory sinus arrhythmia, or high-frequency heart rate variability (its frequency-domain equivalent), has been popular in psychology and the behavioral sciences for some time. It is typically interpreted as an indicator of cardiac vagal activity. However, as research has shown for decades, the respiratory pattern can influence the amplitude of these noninvasive measures substantially, without necessarily reflecting changes in tonic cardiac vagal activity. Although changes in respiration are systematically associated with experiential and behavioral states, this potential confound in the interpretation of RSA, or HF-HRV, is rarely considered. Interpretations of within-individual changes in these parameters are therefore only conclusive if undertaken relative to the breathing pattern. The interpretation of absolute levels of these parameters between individuals is additionally burdened with the problem of residual inspiratory cardiac vagal activity in humans. Furthermore, multiple demographic, anthropometric, life-style, health, and medication variables can act as relevant third variables that might explain associations of RSA or HF-HRV with experiential and behavioral variables. Because vagal activity measured by these parameters only represents the portion of cardiac vagal outflow that is modulated by the respiratory rhythm, alternative interpretations beyond cardiac vagal activity should be considered. Accumulating research shows that activity of multiple populations of neurons in the brain and the periphery, and with that organ activity and function, are modulated rhythmically by respiratory activity. Thus, observable health benefits ascribed to the cardiac vagal system through RSA or HF-HRV may actually reflect beneficial effects of respiratory modulation. Respiratory rhythmicity may ultimately provide the mechanism that integrates central, autonomic, and visceral activities.

Maternal age differences in cognitive regulation: examination of associations and interactions between RSA and EEG frontoparietal alpha power coherence

Strong cognitive regulation is advantageous for flexible, responsive parenting. Optimal cognitive regulation is reliant on associations between physiological mechanisms of central and peripheral nervous system functioning. Across middle adulthood there may be shifts in how cognitive regulation functions, reflecting changes in the associations and interactions between these physiological mechanisms. Two physiological indicators of cognitive regulation are autonomic regulation of the heart (e.g., respiratory sinus arrhythmia, RSA) and activity of the brain's frontoparietal network (e.g., frontoparietal EEG alpha power coherence, FPc). In the current study we examined maternal age differences (N = 90, age M = 32.35 years, SD = 5.86 years) in correlations and interactions between RSA and FPc in the statistical prediction of cognitive regulation [i.e., executive function (EF), effortful control (EC), cognitive reappraisal (CR)]. Age-related patterns involving interaction between RSA and FPc were found, pointing to a potential shift from optimization to compensation for changes with aging or alternately, the effects of age-based decrements in functioning. Findings are discussed in the context of adult developmental changes in maternal caregiving.

Age-Related Factors Associated With The Risk of Hip Fracture

OBJECTIVE

Advancing age is a powerful risk factor for hip fractures. The biological mechanisms through which aging impacts the risk of hip fractures have not been well studied.

METHODS

Biological factors associated with "advancing age" that help to explain how aging is associated with the risk of hip fractures are reviewed. The findings are based on analyses of the Cardiovascular Health Study, an ongoing observational study of adults aged ≥65 years with 25 years of follow-up.

RESULTS

The following 5 age-related factors were found to be significantly associated with the risk of hip fractures: (1) microvascular disease of the kidneys (albuminuria and/or elevated urine-albumin-to-creatinine ratio) and brain (abnormal white matter disease on brain magnetic resonance imaging); (2) increased serum levels of carboxymethyl-lysine, an advanced glycation end product that reflects glycation and oxidative stress; (3) reduced parasympathetic tone, as derived from 24-hour Holter monitoring; (4) carotid artery atherosclerosis in the absence of clinical cardiovascular disease; and (5) increased transfatty acid levels in the blood. Each of these factors was associated with a 10% to 25% increased risk of fractures. These associations were independent of traditional risk factors for hip fractures.

CONCLUSION

Several factors associated with older age help to explain how "aging" may be associated with the risk of hip fractures. These same factors may also explain the high risk of mortality following hip fractures.

Cardiac Behavior and Heart Rate Variability in Elderly Hypertensive Individuals during Aerobic Exercise: A Non-Randomized Controlled Study

BACKGROUND

High blood pressure is an important public health problem due to its high prevalence, the difficulty to control it, and its high contribution to morbidity. A series of changes may be linked to the aging process, compromising cardiac conduction, and reducing cardiovascular baroreceptor function. Advancing age promotes a decline in heart rate variability and this decrease can increase the probability of cardiovascular disease. The aim of this study was to analyze the autonomic modulation of heart rate in hypertensive elderly individuals during and after a session of aerobic exercise, and to compare it with elderly individuals without cardiovascular or metabolic disease. Our study was a non-randomized controlled study with hypertensive elderly (HBP group) and elderly without cardiovascular and/or metabolic diseases (control group). Data on blood pressure and heart rate variability (HRV) were collected before, during, and after 30 min of aerobic physical exercise on a treadmill. There was a reduction in HF (ms2) and SD1 (ms) in the 5 min of recovery for the elderly in the control group. The elderly in the control group also had greater RMSSD and SD1 30 min post-exercise when compared to the initial mins of recovery. We concluded that there was no difference in autonomic modulation and global heart rate variability between elderly individuals without cardiovascular and metabolic diseases and hypertensive individuals after a bout of aerobic exercise. Elderly individuals without metabolic diseases showed a decrease in parasympathetic modulation and global variability between the time of rest and 5 min of recovery. However, up to 30 min of post-exercise recovery, they restored parasympathetic activity.

Associations between locus coeruleus MRI contrast and physiological responses to acute stress in younger and older adults

Acute stress activates the brain's locus coeruleus (LC)-noradrenaline system. Recent studies indicate that a magnetic resonance imaging (MRI)-based measure of LC structure is associated with better cognitive outcomes in later life. Yet despite the LC's documented role in promoting physiological arousal during acute stress, no studies have examined whether MRI-assessed LC structure is related to arousal responses to acute stress. In this study, 102 younger and 51 older adults completed an acute stress induction task while we assessed multiple measures of physiological arousal (heart rate, breathing rate, systolic and diastolic blood pressure, sympathetic tone, and heart rate variability, HRV). We used turbo spin echo MRI scans to quantify LC MRI contrast as a measure of LC structure. We applied univariate and multivariate approaches to assess how LC MRI contrast was associated with arousal at rest and during acute stress reactivity and recovery. In older participants, having higher caudal LC MRI contrast was associated with greater stress-related increases in systolic blood pressure and decreases in HRV, as well as lower HRV during recovery from acute stress. These results suggest that having higher caudal LC MRI contrast in older adulthood is associated with more pronounced physiological responses to acute stress. Further work is needed to confirm these patterns in larger samples of older adults.

The Association of Measures of Cardiovascular Autonomic Function, Heart Rate, and Orthostatic Hypotension With Incident Glucose Disorders: The Cardiovascular Health Study

OBJECTIVE

The autonomic nervous system (ANS) innervates pancreatic endocrine cells, muscle, and liver, all of which participate in glucose metabolism. We tested whether measures of cardiovascular ANS function are independently associated with incident diabetes and annual change in fasting glucose (FG) levels as well as with insulin secretion and insulin sensitivity in older adults without diabetes.

RESEARCH DESIGN AND METHODS

Heart rate (HR) and measures of HR variability (HRV) were derived from 24-h electrocardiographic monitoring. Blood pressure, seated and standing, was measured. Cox proportional hazards models and linear mixed models were used to analyze the associations between HRV, HR, and orthostatic hypotension (SBP >20 mmHg decline) and incident diabetes or longitudinal FG change.

RESULTS

The mean annual unadjusted FG change was 1 mg/dL. Higher detrended fluctuation analyses (DFA) values, averaged over 4-11 (DFA1) or 12-20 beats (DFA2)-reflecting greater versus less organization of beat-to-beat intervals-were associated with less FG increase over time (per 1-SD increment: DFA1: -0.49 mg/dL/year [-0.96, -0.03]; DFA2: -0.55 mg/dL/year [-1.02, -0.09]). In mutually adjusted analyses, higher SD of the N-N interval (SDNN) was associated with less FG increase over time (per 1-SD increment: SDNN: -0.62 mg/dL/year [-1.22, -0.03]). Higher values of DFA1, DFA2, and SDNN were each associated with greater insulin secretion and insulin sensitivity but not with incident diabetes. We observed no association of HR or orthostatic hypotension with diabetes or FG change.

CONCLUSIONS

Specific measures of cardiac autonomic function are prospectively related to FG level changes and insulin secretion and action.

Forebrain Network Associated with Cardiovascular Control in Exercising Humans

ABSTRACT

This article describes the forebrain neurocircuitry associated with rapid heart rate response at the exercise onset with attention to ascending somatosensory information from the Type I and II afferents from the contracting muscle and potential influence of sensory information related to blood pressure and changes in heart rate.

Prevalence of pain in community-dwelling older adults with hypertension in the United States

Hypertension and pain are both prevalent conditions in the older adult population. We aimed to report the prevalence of pain discomforts and investigated the association between hypertension and pain discomforts among older adults in the United States. Data from the 2011 National Health and Aging Trends Study were analyzed. In-person interviews were conducted in 7601 adults ages ≥ 65 years. Prevalence of bothersome pain, activity-limiting pain, locations of pain and usage of pain medicine were evaluated. Demographics, comorbidities, and other covariates were compared between older adults with hypertension and those without. Multivariate regression was further performed to yield adjusted odd ratios. Among 6825 older adults, 4533 of them had a history of hypertension while 2272 of them had not. Prevalence of bothersome pain (57.12% versus 44.81%, p < 0.001) and activity-limiting pain (56.21% versus 46.12%, p < 0.001) were significantly higher in the hypertension group. After adjusting for all covariates, hypertension demonstrated a significant association with activity-limiting pain (OR 1.63, 95% CI 1.06 to 2.52, p = 0.02). In conclusion, pain was more prevalent in older Americans with hypertension. The positive association between hypertension and pain suggested that routine pain assessment and proper treatment would be required to improve the function and quality of life among older adults especially with hypertension.

Heart Rate Variability Analysis to Evaluate Autonomic Nervous System Maturation in Neonates: An Expert Opinion

While heart rate variability (HRV) is a relevant non-invasive tool to assess the autonomic nervous system (ANS) functioning with recognized diagnostic and therapeutic implications, the lack of knowledge on its interest in neonatal medicine is certain. This review aims to briefly describe the algorithms used to decompose variations in the length of the RR interval and better understand the physiological autonomic maturation data of the newborn. Assessing newborns' autonomous reactivity can identify dysautonomia situations and discriminate children with a high risk of life-threatening events, which should benefit from cardiorespiratory monitoring at home. Targeted monitoring of HRV should provide an objective reflection of the newborn's intrinsic capacity for cardiorespiratory self-regulation.

Cardiovascular autonomic nervous system function and hip fracture risk: the Cardiovascular Health Study

Among 1299 older adults with 24-h Holter monitoring data at baseline, followed for approximately 15 years, 190 incident hip fractures occurred. Increased heart rate variability was independently associated with reduced risk of hip fracture among female participants.

PURPOSE

Autonomic nervous system function modulates bone remodeling in rodent osteoporosis models. We tested whether cardiovascular autonomic function is associated with hip fracture risk in humans.

METHODS

Participants were 1299 subjects from the Cardiovascular Health Study (mean age 72.8 years). Eight heart rate variability (HRV) measures (time and frequency domains, detrended fluctuation analysis variables, and heart rate turbulence) were derived from 24-h Holter monitor scans in sinus rhythm. Median follow-up for incident hip fracture was 14.7 years [IQR 9.1, 20.2]. Cox proportional hazards models were used to calculate hazard ratios (95% confidence intervals, CI).

RESULTS

There were 144 hip fractures among 714 women (1.31 [1.06, 1.61] per 100-person years) and 46 among 585 men (0.62 [0.43, 0.90] per 100 person-years). From among HRV variables examined, a one standard deviation (SD) higher variation between normal heart beats over 24 h (the SD of NN intervals [SDNN]) was associated with a multivariable-adjusted lower hip fracture risk (HR [Formula: see text] 0.80; 95% CI 0.65-0.99; p = 0.04) in women. The adjusted association between very low frequency power, and hip fracture was borderline statistically significant in women (HR [Formula: see text] 0.82; 95% CI, 0.66-1.00; p = 0.06). When the 8 HRV variables were considered conjointly and adjusted for each other's association with hip fracture risk, a 1 SD higher SDNN value was significantly associated with reduced hip fracture risk in women (HR 0.74; 95% CI, 0.50-0.99; p = 0.05). No HRV variables were associated with hip fracture in men.

CONCLUSIONS

In older women, increased heart rate variation is associated with hip fracture risk.

Exercise-based cardiac rehabilitation and parasympathetic function in patients with coronary artery disease: a systematic review and meta-analysis

PURPOSE

The effects of exercise-based cardiac rehabilitation (CR) on parasympathetic modulation are controversial. This systematic review and meta-analysis aims to (a) determine the effect of exercise-based CR on heart-rate-derived indices associated with cardiac parasympathetic modulation in resting and post-exercise conditions in coronary artery disease (CAD) patients and (b) identify the possible moderator variables of the effect of exercise-based CR on parasympathetic modulation.

METHODS

We searched CENTRAL and Web of Science up to November 2018 for the following terms: adult CAD patients, controlled exercise-based CR interventions and parasympathetic modulation measured in resting (vagal-related heart rate variability [HRV] indices of the root mean square of the differences in successive in RR interval [RMSSD] and high frequency [HF]) and post-exercise (heart rate recovery [HRR]) pre- and post-intervention. We estimated a random-effects model of standardised mean difference (SMD) and mean difference (MD) for vagal-related HRV indices and HRR, respectively. We assessed the influence of categorical and continuous variables.

RESULTS

The overall effect size showed significant differences in RMSSD (SMD+ = 0.30; 95% confidence interval [CI] = 0.12-0.49) and HRR (MD+ = 5.35; 95% CI = 4.08-6.61 bpm) in favour of the exercise-based CR group. The overall effect size showed no differences in HF between groups (SMD+ = 0.14; 95% CI,  -0.12-0.40). Heterogeneity analyses reached statistical significance, with high heterogeneity for HF (p < 0.001; I2 = 70%) and HRR (p < 0.001; I2 = 85%). Analysis of the moderator variables showed that the effect on HRR is greater in young patients (p = 0.008) and patients treated with percutaneous intervention (p = 0.020).

CONCLUSIONS

Exercise-based CR improves the post-exercise parasympathetic function, with greater effects in younger CAD patients and in those who were revascularised with percutaneous intervention. The effects on resting parasympathetic function are more controversial due to methodological inconsistencies in measuring HRV, with the use of RMSSD recommended instead of HF because its results show higher consistency. Future studies involving women, focusing on methodological issues, and performing other training methods are needed to increase our knowledge about this topic.

Melatonin to Rescue the Aged Heart: Antiarrhythmic and Antioxidant Benefits

Aging comes with gradual loss of functions that increase the vulnerability to disease, senescence, and death. The mechanisms underlying these processes are linked to a prolonged imbalance between damage and repair. Damaging mechanisms include oxidative stress, mitochondrial dysfunction, chronodisruption, inflammation, and telomere attrition, as well as genetic and epigenetic alterations. Several endogenous tissue repairing mechanisms also decrease. These alterations associated with aging affect the entire organism. The most devastating manifestations involve the cardiovascular system and may lead to lethal cardiac arrhythmias. Together with structural remodeling, electrophysiological and intercellular communication alterations during aging predispose to arrhythmic events. Despite the knowledge on repairing mechanisms in the cardiovascular system, effective antiaging strategies able to reduce the risk of arrhythmias are still missing. Melatonin is a promising therapeutic candidate due to its pleiotropic actions. This indoleamine regulates chronobiology and endocrine physiology. Of relevance, melatonin is an antiaging, antioxidant, antiapoptotic, antiarrhythmic, immunomodulatory, and antiproliferative molecule. This review focuses on the protective effects of melatonin on age-induced cardiac functional and structural alterations, potentially becoming a new fountain of youth for the heart.

The Vagal Autonomic Pathway of COVID-19 at the Crossroad of Alzheimer's Disease and Aging: A Review of Knowledge

Coronavirus Disease 2019 (COVID-19) pandemic-triggered mortality is significantly higher in older than in younger populations worldwide. Alzheimer's disease (AD) is related to aging and was recently reported to be among the major risk factors for COVID-19 mortality in older people. The symptomatology of COVID-19 indicates that lethal outcomes of infection rely on neurogenic mechanisms. The present review compiles the available knowledge pointing to the convergence of COVID-19 complications with the mechanisms of autonomic dysfunctions in AD and aging. The severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is prone to neuroinvasion from the lung along the vagus nerve up to the brainstem autonomic nervous centers involved in the coupling of cardiovascular and respiratory rhythms. The brainstem autonomic network allows SARS-CoV-2 to trigger a neurogenic switch to hypertension and hypoventilation, which may act in synergy with aging- and AD-induced dysautonomias, along with an inflammatory "storm". The lethal outcomes of COVID-19, like in AD and unhealthy aging, likely rely on a critical hypoactivity of the efferent vagus nerve cholinergic pathway, which is involved in lowering cardiovascular pressure and systemic inflammation tone. We further discuss the emerging evidence supporting the use of 1) the non-invasive stimulation of vagus nerve as an additional therapeutic approach for severe COVID-19, and 2) the demonstrated vagal tone index, i.e., heart rate variability, via smartphone-based applications as a non-serological low-cost diagnostic of COVID-19. These two well-known medical approaches are already available and now deserve large-scale testing on human cohorts in the context of both AD and COVID-19.

Short-Term Resistance Training Improves Cardiac Autonomic Modulation and Blood Pressure in Hypertensive Older Women: A Randomized Controlled Trial

Oliveira-Dantas, FF, Brasileiro-Santos, MdS, Thomas, SG, Silva, AS, Silva, DC, Browne, RAV, Farias-Junior, LF, Costa, EC, and Santos, AdC. Short-term resistance training improves cardiac autonomic modulation and blood pressure in hypertensive older women: a randomized controlled trial. J Strength Cond Res 34(1): 37-45, 2020-This randomized controlled trial investigated the efficacy of short-term resistance training (RT) on cardiac autonomic modulation and peripheral hemodynamic parameters in hypertensive older women. Twenty-five hypertensive older women who were insufficiently active (64.7 ± 4.7 years) participated in this study. Subjects were randomly allocated to a 10-week RT program (2 d·wk in the first 5 weeks; 3 d·wk in the last 5 weeks) or a nonexercise control group. Linear reverse periodization was used for the RT program. Cardiac autonomic modulation, mean blood pressure (MBP), peripheral vascular resistance (PVR), and resting heart rate (RHR) were measured before and after 10 weeks. The RT group reduced cardiac sympathetic modulation (0V%; B = -6.6; 95% confidence interval [CI]: -12.9 to -0.2; p = 0.045; Cohen's d = 0.88) and showed a trend for increased parasympathetic modulation (2V%; B = 12.5; 95% CI: 0-25; p = 0.050; Cohen's d = 0.87) compared with the control group. The RT group reduced MBP (B = -8.5 mm Hg; 95% CI: -13.6 to -3.4; p = 0.001; Cohen's d = 1.27), PVR (B = -14.1 units; 95% CI: -19.9 to -8.4; p < 0.001; Cohen's d = 1.86), and RHR (B = -8.8 b·min; 95% CI: -14.3 to -3.3; p = 0.002; Cohen's d = 1.20) compared with the control group. In the RT group, the changes in 2V% patterns and low-frequency components showed a correlation with changes in MBP (r = -0.60; p = 0.032) and RHR (r = 0.75; p = 0.0003). In conclusion, 10 weeks of RT improved cardiac autonomic modulation and reduced MBP and PVR in hypertensive older women. These results reinforce the importance of RT for this population.

GDF-11 prevents cardiomyocyte hypertrophy by maintaining the sarcoplasmic reticulum-mitochondria communication

Growth differentiation factor 11 (GDF11) is a novel factor with controversial effects on cardiac hypertrophy both in vivo and in vitro. Although recent evidence has corroborated that GDF11 prevents the development of cardiac hypertrophy, its molecular mechanism remains unclear. In our previous work, we showed that norepinephrine (NE), a physiological pro-hypertrophic agent, increases cytoplasmic Ca²⁺ levels accompanied by a loss of physical and functional communication between sarcoplasmic reticulum (SR) and mitochondria, with a subsequent reduction in the mitochondrial Ca²⁺ uptake and mitochondrial metabolism. In order to study the anti-hypertrophic mechanism of GDF11, our aim was to investigate whether GDF11 prevents the loss of SR-mitochondria communication triggered by NE. Our results show that: a) GDF11 prevents hypertrophy in cultured neonatal rat ventricular myocytes treated with NE. b) GDF11 attenuates the NE-induced loss of contact sites between both organelles. c) GDF11 increases oxidative mitochondrial metabolism by stimulating mitochondrial Ca²⁺ uptake. In conclusion, the GDF11-dependent maintenance of physical and functional communication between SR and mitochondria is critical to allow Ca²⁺ transfer between both organelles and energy metabolism in the cardiomyocyte and to avoid the activation of Ca²⁺-dependent pro-hypertrophic signaling pathways.

Autonomic maturation from birth to 2 years: normative values

Background

While heart rate variability (HRV) constitutes a relevant non-invasive tool to assess the autonomic nervous system (ANS) function with recognized diagnostic or therapeutic implications, there is still a lack of established data on maturation of autonomic control of heart rate during the first months of life. The Autonomic Baby Evaluation (AuBE) cohort was built to establish, the normal autonomic maturation profile from birth up to 2 years, in a healthy population of full-term newborns.

Methods

Heart rate variability analysis was carried out in 271 full-term newborns (mean gestational age 39 wGA + 5 days) from reliable polysomnographic recordings at 0 (n = 270) and 6 (n = 221) months and from a 24-hour ambulatory electrocardiogram (ECG) at 12 (n = 210), 18 (n = 197), and 24 (n = 190) months. Indices of HRV analysis were calculated through the ANSLabTools software.

Results

Indices are dissociated according a temporal, geometrical, frequency, Poincaré, empirical mode decomposition, fractal, Chaos and DC/AC and entropy analysis. Each index is presented for five different periods of time, 0, 6, 12, 18 and 24 months and with smoothed values in the 3rd, 10th, 50th, 90th and 97th percentiles. Data are also presented for the full cohort and individualized by sex to account for gender variability.

Discussion & conclusion

The physiological autonomic maturation profile from birth to 2 years in a healthy population of term neonates results in a fine-tuning autonomic maturation underlying progressively a new equilibrium and privileging the parasympathetic activity over the sympathetic activity.

Heart rate response to graded exercise test of elderly subjects in different ranges of TSH levels

OBJECTIVE

Life expectancy is increasing worldwide and studies have been demonstrating that elevated serum thyroid stimulating hormone (TSH) concentration in elderly is associated with some better health outcomes. This elevation is somewhat physiological as aging. The aim of this study was to investigate the heart rate (HR) response during a graded exercise test and its recovery in healthy elderly, comparing subjects within serum TSH in the lower limit of reference range to those within the TSH in the upper limit.

SUBJECTS AND METHODS

A cross-sectional study was conducted with 86 healthy elderly aged 71.5 ± 5.1 years, with serum TSH between 0.4 - 4.0 mUl/mL. The participants were divided into two groups according to TSH level: < 1.0 mUl/mL (n = 13) and ≥ 1.0 µUI/mL (n = 73). All participants performed an ergometric test on a treadmill. The HR was recorded and analyzed at rest, during exercise and during the three minutes immediately after exercise.

RESULTS

No differences were observed in relation to HR at peak of exercise (TSH < 1.0 µUI/mL: 133.9 ± 22.5 bpm vs. TSH ≥ 1.0 µUI/mL: 132.4 ± 21.3 bpm; p = 0.70) and during the first minute of recovery phase (TSH < 1.0 µUI/mL: 122.3 ± 23.1 bpm vs. TSH ≥ 1.0 µUI/mL: 115.7 ± 18.4 bpm p = 0.33). The groups also presented similar chronotropic index (TSH < 1.0 µUI/mL: 78.1 ± 30.6 vs. TSH ≥ 1.0 µUI/mL: 79.5 ± 26.4; p = 0.74).

CONCLUSION

In this sample studied, there were no difference between lower and upper TSH level concerning HR response during rest, peak of exercise and exercise recovery.

Impact of the Autonomic Nervous System on the Skeleton

It is from the discovery of leptin and the central nervous system as a regulator of bone remodeling that the presence of autonomic nerves within the skeleton transitioned from a mere histological observation to the mechanism whereby neurons of the central nervous system communicate with cells of the bone microenvironment and regulate bone homeostasis. This shift in paradigm sparked new preclinical and clinical investigations aimed at defining the contribution of sympathetic, parasympathetic, and sensory nerves to the process of bone development, bone mass accrual, bone remodeling, and cancer metastasis. The aim of this article is to review the data that led to the current understanding of the interactions between the autonomic and skeletal systems and to present a critical appraisal of the literature, bringing forth a schema that can put into physiological and clinical context the main genetic and pharmacological observations pointing to the existence of an autonomic control of skeletal homeostasis. The different types of nerves found in the skeleton, their functional interactions with bone cells, their impact on bone development, bone mass accrual and remodeling, and the possible clinical or pathophysiological relevance of these findings are discussed.

Proinflammatory Arterial Stiffness Syndrome: A Signature of Large Arterial Aging

Age-associated structural and functional remodeling of the arterial wall produces a productive environment for the initiation and progression of hypertension and atherosclerosis. Chronic aging stress induces low-grade proinflammatory signaling and causes cellular proinflammation in arterial walls, which triggers the structural phenotypic shifts characterized by endothelial dysfunction, diffuse intimal-medial thickening, and arterial stiffening. Microscopically, aged arteries exhibit an increase in arterial cell senescence, proliferation, invasion, matrix deposition, elastin fragmentation, calcification, and amyloidosis. These characteristic cellular and matrix alterations not only develop with aging but can also be induced in young animals under experimental proinflammatory stimulation. Interestingly, these changes can also be attenuated in old animals by reducing low-grade inflammatory signaling. Thus, mitigating age-associated proinflammation and arterial phenotype shifts is a potential approach to retard arterial aging and prevent the epidemic of hypertension and atherosclerosis in the elderly.

Exercise training abrogates age-dependent loss of hypothalamic oxytocinergic circuitry and maintains high parasympathetic activity

Neuroanatomical studies associating neuronal tract tracing and immunohistochemistry identified reciprocal (ascending noradrenergic/descending oxytocinergic, OTergic) connections between brainstem cardiovascular nuclei and the paraventricular hypothalamic nucleus (PVN). Previous functional studies indicated that exercise training (T) augmented the expression/activity of OTergic pathway and improve the autonomic control of the heart. Knowing that ageing is associated with autonomic dysfunction and sinoaortic denervation blocked T-induced beneficial effects, we hypothesized that T was able to reduce age-dependent impairment by improving the afferent signaling to PVN and augmenting OTergic modulation of cardiovascular control. We evaluated the combined effects of T and age on plastic remodeling of ascending dopamine β-hydroxylase (DBH+) and descending OT+ pathways and correlated them with cardiovascular parameters. Male Wistar rats were submitted to T or kept sedentary for 8 weeks. After evaluating arterial pressure, heart rate (HR), their variabilities and spectral components in conscious rats at rest, brains were harvested to analyze the plastic remodeling of brain autonomic nuclei (immunofluorescence + confocal microscopy). The density of DBH+ neurons within the nucleus of solitary tract (NTS) and caudal ventrolateral medulla, the number of DBH+ terminals overlapping OT+ neurons in PVN preautonomic nuclei, as well as the density of OT+ neurons and their projections to NTS and dorsal motor nucleus of the vagus were markedly reduced in S rats during 8-weeks of inactivity In contrast, these effects were completely blocked by T and reversed to a large augmentation of DBH+ and OT+ densities in both cell bodies and terminals within autonomic nuclei and target areas. All plastic changes observed correlated positively with parasympathetic activity to the heart (HF-PI, but not with LF-PI) and negatively with resting HR. Data indicate that T, by increasing beneficial neuroplastic adaptive changes within brainstem-PVN reciprocal network, abrogates age-dependent deleterious remodeling and augments parasympathetic modulation of the heart, therefore improving autonomic function. This article is protected by copyright. All rights reserved.

Age-related decline in cardiac autonomic function is not attenuated with increased physical activity

Age and physical inactivity are important risk factors for cardiovascular mortality. Heart rate response to exercise (HRRE) and heart rate recovery (HRR), measures of cardiac autonomic function, are strong predictors of mortality. The present study defined the effect of age and physical activity on HRRE and HRR. Healthy women (N=72) grouped according to age (young, 20-30 years; middle, 40-50 years; and older, 65-81 years) and daily physical activity (low active <7500, high active >12,500 steps/day) performed a maximal cardiopulmonary exercise test. The HRRE was defined as an increase in heart rate from rest to 1, 3 and 5 minutes of exercise and at 1/3 of total exercise time, and HRR as the difference in heart rate between peak exercise and 1, 2, and 3 minutes later. Age was associated with a significant decline in HRRE at 1 min and 1/3 of exercise time (r= − 0.27, p=0.04, and r=−0.39, p=0.02) and HRR at 2 min and 3 min (r=−0.35, p=0.01, and r=−0.31, p=0.02). There was no significant difference in HRRE and HRR between high and low-active middle-age and older women (p>0.05). Increased level of habitual physical activity level appears to have a limited effect on age-related decline in cardiac autonomic function in women.

The Cardiac Sympathetic Nerve Activity in the Elderly Is Attenuated in the Right Lateral Decubitus Position

Objectives: The aim of this study was to evaluate the effect of the supine, left lateral decubitus, and right lateral decubitus positions on autonomic nervous activity in elderly adults by using spectral analysis of heart rate variability (HRV). Method: Forty-five adults aged 73.6 ± 5.7 years were enrolled. After lying in the supine position, all participants moved to the lateral decubitus positions in a random order and maintained the positions for 10 min, while electrocardiographic data were recorded to measure HRV. Results: The lowest heart rate continued for 10 min when participants were in the left lateral decubitus position compared with the other two positions (p < .001), while the HRV indexes remained unchanged. The low-frequency HRV to high-frequency HRV ratio (LF/HF) for the right lateral decubitus position was significantly lower than that for the other positions. Discussion: The right lateral decubitus position may attenuate sympathetic nerve activity in elderly adults.

Prioritizing Functional Capacity as a Principal End Point for Therapies Oriented to Older Adults With Cardiovascular Disease: A Scientific Statement for Healthcare Professionals From the American Heart Association

Adults are living longer, and cardiovascular disease is endemic in the growing population of older adults who are surviving into old age. Functional capacity is a key metric in this population, both for the perspective it provides on aggregate health and as a vital goal of care. Whereas cardiorespiratory function has long been applied by cardiologists as a measure of function that depended primarily on cardiac physiology, multiple other factors also contribute, usually with increasing bearing as age advances. Comorbidity, inflammation, mitochondrial metabolism, cognition, balance, and sleep are among the constellation of factors that bear on cardiorespiratory function and that become intricately entwined with cardiovascular health in old age. This statement reviews the essential physiology underlying functional capacity on systemic, organ, and cellular levels, as well as critical clinical skills to measure multiple realms of function (eg, aerobic, strength, balance, and even cognition) that are particularly relevant for older patients. Clinical therapeutic perspectives and patient perspectives are enumerated to clarify challenges and opportunities across the caregiving spectrum, including patients who are hospitalized, those managed in routine office settings, and those in skilled nursing facilities. Overall, this scientific statement provides practical recommendations and vital conceptual insights.

Age-dependent diastolic heart failure in an in vivo Drosophila model

While the signals and complexes that coordinate the heartbeat are well established, how the heart maintains its electromechanical rhythm over a lifetime remains an open question with significant implications to human health. Reasoning that this homeostatic challenge confronts all pulsatile organs, we developed a high resolution imaging and analysis toolset for measuring cardiac function in intact, unanesthetized Drosophila melanogaster. We demonstrate that, as in humans, normal aging primarily manifests as defects in relaxation (diastole) while preserving contractile performance. Using this approach, we discovered that a pair of two-pore potassium channel (K2P) subunits, largely dispensable early in life, are necessary for terminating contraction (systole) in aged animals, where their loss culminates in fibrillatory cardiac arrest. As the pumping function of its heart is acutely dispensable for survival, Drosophila represents a uniquely accessible model for understanding the signaling networks maintaining cardiac performance during normal aging.

Ganglionic GFAP + glial Gq-GPCR signaling enhances heart functions in vivo

The sympathetic nervous system (SNS) accelerates heart rate, increases cardiac contractility, and constricts resistance vessels. The activity of SNS efferent nerves is generated by a complex neural network containing neurons and glia. Gq G protein-coupled receptor (Gq-GPCR) signaling in glial fibrillary acidic protein-expressing (GFAP⁺) glia in the central nervous system supports neuronal function and regulates neuronal activity. It is unclear how Gq-GPCR signaling in GFAP⁺ glia affects the activity of sympathetic neurons or contributes to SNS-regulated cardiovascular functions. In this study, we investigated whether Gq-GPCR activation in GFAP⁺ glia modulates the regulatory effect of the SNS on the heart; transgenic mice expressing Gq-coupled DREADD (designer receptors exclusively activated by designer drugs) (hM3Dq) selectively in GFAP⁺ glia were used to address this question in vivo. We found that acute Gq-GPCR activation in peripheral GFAP⁺ glia significantly accelerated heart rate and increased left ventricle contraction. Pharmacological experiments suggest that the glial-induced cardiac changes were due to Gq-GPCR activation in satellite glial cells within the sympathetic ganglion; this activation led to increased norepinephrine (NE) release and beta-1 adrenergic receptor activation within the heart. Chronic glial Gq-GPCR activation led to hypotension in female Gfap-hM3Dq mice. This study provides direct evidence that Gq-GPCR activation in peripheral GFAP⁺ glia regulates cardiovascular functions in vivo.

A Model-Based Machine Learning Approach to Probing Autonomic Regulation From Nonstationary Vital-Sign Time Series

Physiological variables, such as heart rate (HR), blood pressure (BP) and respiration (RESP), are tightly regulated and coupled under healthy conditions, and a break-down in the coupling has been associated with aging and disease. We present an approach that incorporates physiological modeling within a switching linear dynamical systems (SLDS) framework to assess the various functional components of the autonomic regulation through transfer function analysis of nonstationary multivariate time series of vital signs. We validate our proposed SLDS-based transfer function analysis technique in automatically capturing 1) changes in baroreflex gain due to postural changes in a tilt-table study including ten subjects, and 2) the effect of aging on the autonomic control using HR/RESP recordings from 40 healthy adults. Next, using HR/BP time series of more than 450 adult ICU patients, we show that our technique can be used to reveal coupling changes associated with severe sepsis (AUC = 0.74, sensitivity = 0.74, specificity = 0.60). Our findings indicate that reduced HR/BP coupling is significantly associated with severe sepsis even after adjusting for clinical interventions (P  0.001). These results demonstrate the utility of our approach in phenotyping complex vital-sign dynamics, and in providing mechanistic hypotheses in terms of break-down of autoregulatory systems under healthy and disease conditions.

Changes of heart rate variability and prefrontal oxygenation during Tai Chi practice versus arm ergometer cycling

[Purpose] Exercise has been shown to improve cardiovascular fitness and cognitive function. Whether the inclusion of mind over exercise would increase parasympathetic control of the heart and brain activities more than general exercise at a similar intensity is not known. The aim of this study was to compare the effects of Tai Chi (mind-body exercise) versus arm ergometer cycling (body-focused exercise) on the heart rate variability and prefrontal oxygenation level. [Subjects and Methods] A Tai Chi master was invited to perform Tai Chi and arm ergometer cycling with similar exercise intensity on two separate days. Heart rate variability and prefrontal oxyhemoglobin levels were measured continuously by a RR recorder and near-infrared spectroscopy, respectively. [Results] During Tai Chi exercise, spectral analysis of heart rate variability demonstrated a higher high-frequency power as well as a lower low-frequency/high-frequency ratio than during ergometer cycling, suggesting increased parasympathetic and decreased sympathetic control of the heart. Also, prefrontal oxyhemoglobin and total hemoglobin levels were higher than those during arm ergometer exercise. [Conclusion] These findings suggest that increased parasympathetic control of the heart and prefrontal activities may be associated with Tai Chi practice. Having a “mind” component in Tai Chi could be more beneficial for older adults’ cardiac health and cognitive function than body-focused ergometer cycling.

Omega-3 polyunsaturated fatty acid supplementation attenuates blood pressure increase at onset of isometric handgrip exercise in healthy young and older humans

Aging is associated with alterations of autonomic nerve activity, and dietary intake of omega-3 polyunsaturated fatty acids, such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) found in fish oil (FO), can modulate autonomic nerve activity. However, the effect of omega-3 polyunsaturated fatty acid consumption on age-related cardiovascular responses at the onset of isometric handgrip exercise, a time of rapid autonomic adjustments, is unknown. Accordingly, 14 young (25 ± 1 years; mean ± SE) and 15 older (64 ± 2 years) healthy subjects ingested 4 g FO daily for 12 weeks. On pre- and postintervention visits, participants performed 15-sec bouts of isometric handgrip at 10%, 30%, 50%, and 70% maximal voluntary contraction (MVC) while beat-to-beat systolic, diastolic, and mean arterial blood pressure (SBP, DBP, MAP; Finometer) and heart rate (HR; electrocardiogram) were recorded. All baseline cardiovascular variables were similar between groups and visits, except DBP was higher in older subjects (P < 0.05). FO increased erythrocyte EPA and DHA content in both groups (P < 0.05). FO attenuated MAP and DBP increases in response to handgrip in both age groups (change from baseline during 70% MVC handgrip pre- and post-FO: young MAPΔ 14 ± 2 mmHg versus 10 ± 2 mmHg, older MAPΔ 14 ± 3 mmHg versus 11 ± 2 mmHg; young DBPΔ 12 ± 1 mmHg versus 7 ± 2 mmHg, older DBPΔ 12 ± 1 mmHg versus 7 ± 1 mmHg; P < 0.05). FO augmented the PP (SBP-DBP) increase with 70% MVC handgrip in both groups (P < 0.05), but did not alter SBP or HR increases with handgrip. These findings suggest that FO supplementation attenuates MAP and DBP increases at the onset of isometric handgrip exercise in healthy young and older humans.

The Role of Exercise in Cardiac Aging: From Physiology to Molecular Mechanisms

Aging induces structural and functional changes in the heart that are associated with increased risk of cardiovascular disease and impaired functional capacity in the elderly. Exercise is a diagnostic and therapeutic tool, with the potential to provide insights into clinical diagnosis and prognosis, as well as the molecular mechanisms by which aging influences cardiac physiology and function. In this review, we first provide an overview of how aging impacts the cardiac response to exercise, and the implications this has for functional capacity in older adults. We then review the underlying molecular mechanisms by which cardiac aging contributes to exercise intolerance, and conversely how exercise training can potentially modulate aging phenotypes in the heart. Finally, we highlight the potential use of these exercise models to complement models of disease in efforts to uncover new therapeutic targets to prevent or treat heart disease in the aging population.

Sympathetic nervous response to ischemia-reperfusion injury in humans is altered with remote ischemic preconditioning

Sympathetic neural activation may be detrimentally involved in tissue injury caused by ischemia-reperfusion (IR). We examined the effects of experimental IR in the forearm on sympathetic nerve response, finger reactive hyperemia, and oxidative stress, and the protection afforded by applying remote ischemic preconditioning (RIPC). Ischemia was induced in the forearm for 20 min in healthy volunteers. RIPC was induced by applying two cycles, 5 min each, of ischemia and reperfusion to the upper leg immediately before IR. We examined muscle sympathetic nerve activity (MSNA) in the contralateral leg using microneurography, finger reactive hyperemia [ischemic reactive hyperemia index (RHI)], erythrocyte production of reduced gluthathione (GSH), and plasma nitric oxide (NO) concentration. In controls (no RIPC; n = 15), IR increased MSNA in the early and late phase of ischemia (70% at 5 min; 101% at 15 min). In subjects who underwent RIPC (n = 15), the increase in MSNA was delayed to the late phase of ischemia and increased only by 40%. GSH increased during ischemia in the control group (P = 0.05), but not in those who underwent RIPC. Nitrate and nitrite concentration, taken as an index of NO availability, decreased during the reperfusion period in control individuals (P < 0.05), while no change was observed in those who underwent RIPC. Experimental IR did not affect RHI in the control condition, but a significant vasodilatory response occurred in the RIPC group (P < 0.05). RIPC attenuated ischemia-induced sympathetic activation, prevented the production of an erythrocyte marker of oxidative stress and the reduction of NO availability, and ameliorated RHI.

Beta-Adrenergic Blockade Therapy for Autonomic Dysfunction is Less Effective for Elderly Patients with Heart Failure and Reduced Left Ventricular Ejection Fraction

OBJECTIVE

Heart rate variability (HRV) has been reported to be an independent predictor of all-cause and sudden cardiac death in patients with heart failure. In the aging heart, however, both autonomic and cardiac functions appear to be altered. We assessed the relationship between aging and responsiveness of HRV and ventricular remodeling to beta-adrenergic blockade therapy in patients with heart failure and reduced ejection fraction (HFREF).

METHODS

Twenty-eight clinically stable patients with chronic heart failure, sinus rhythm, and left ventricular ejection fraction <50% as confirmed by echocardiography were included. At baseline and after carvedilol treatment, 24-hour ambulatory Holter monitor recording was used to analyze HRV indices by the maximum entropy method. Changes in these parameters were compared among three age groups.

RESULTS

HR decreased in all groups after carvedilol treatment, but was still highest in the youngest group despite the same treatment doses. Time and frequency domain variables improved. The response of time domain variables (the standard deviation of all normal sinus to normal sinus [NN] intervals and the standard deviation of the averages of NN intervals in all 5-minute or 30-minute segments) to carvedilol therapy significantly decreased with increasing age. Ventricular reverse remodeling induced by carvedilol therapy significantly decreased with increasing age. Increases in time domain variables and a low-frequency domain moderately correlated with left ventricular reverse remodeling.

CONCLUSION

Beta-adrenergic blockade therapy improved HRV variables and ventricular remodeling in HFREF patients; however, the response tended to be milder in the elderly. HRV improvement was associated with ventricular reverse remodeling.

Age influences inflammatory responses, hemodynamics, and cardiac proteasome activation during acute lung injury

BACKGROUND

Acute lung injury (ALI) is a significant source of morbidity and mortality in critically ill patients. Age is a major determinant of clinical outcome in ALI. The increased ALI-associated mortality in the older population suggests that there are age-dependent alterations in the responses to pulmonary challenge. The objective of this observational study was to evaluate age-dependent differences in the acute (within 6 hours) immunological and physiological responses of the heart and lung, to pulmonary challenge, that could result in increased severity.

METHODS

Male C57Bl/6 mice (young: 2-3 months, old: 18-20 months) were challenged intratracheally with cell wall components from Gram-positive bacteria (lipoteichoic acid and peptidoglycan). After 6 hours, both biochemical and physiological consequences of the challenge were assessed. Alveolar infiltration of inflammatory cells and protein, airspace and blood cytokines, cardiac function and myocardial proteasome activity were determined.

RESULTS

In young mice, there was a dose-dependent response to pulmonary challenge resulting in increased airspace neutrophil counts, lung permeability, and concentrations of cytokines in bronchoalveolar lavage fluid and plasma. A midrange dose was then selected to compare the responses in young and old animals. In comparison, the old animals displayed increased neutrophil accumulation in the airspaces, decreased arterial oxygen saturation, body temperatures, plasma cytokine concentrations, and a lack of myocardial proteasome response, following challenge.

CONCLUSIONS

Age-dependent differences in the onset of systemic response and in maintenance of vital functions, including temperature control, oxygen saturation, and myocardial proteasome activation, are evident. We believe a better understanding of these age-related consequences of ALI can lead to more appropriate treatments in the elderly patient population.

The exercise heart rate profile in master athletes compared to healthy controls

Endurance exercise protects the heart via effects on autonomic control of heart rate (HR); however, its effects on HR indices in healthy middle-aged men are unclear. This study compared HR profiles, including resting HR, increase in HR during exercise and HR recovery after exercise, in middle-aged athletes and controls. Fifty endurance-trained athletes and 50 controls (all male; mean age, 48·7 ± 5·8 years) performed an incremental symptom-limited exercise treadmill test. The electrocardiographic findings and HR profiles were evaluated. Maximal O2 uptake (52·6 ± 7·0 versus 34·8 ± 4·5 ml kg(-1)  min(-1) ; P<0·001) and the metabolic equivalent of task (15·4 ± 1·6 versus 12·2 ± 1·5; P<0·001) were significantly higher in athletes than in controls. Resting HR was significantly lower in athletes than in controls (62·8 ± 6·7 versus 74·0 ± 10·4 beats per minute (bpm), respectively; P<0·001). Athletes showed a greater increase in HR during exercise than controls (110·1 ± 11·0 versus 88·1 ± 15·4 bpm; P<0·001); however, there was no significant between-group difference in HR recovery at 1 min after cessation of exercise (22·9 ± 5·6 versus 21·3 ± 6·7 bpm; P = 0·20). Additionally, athletes showed a lower incidence of premature ventricular contractions (PVCs) during exercise (0·0% versus 24·0%; P<0·001). Healthy middle-aged men participating in regular endurance exercise showed more favourable exercise HR profiles and a lower incidence of PVCs during exercise than sedentary men. These results reflect the beneficial effect of endurance training on autonomic control of the heart.

The effect of aging on the specialized conducting system: a telemetry ECG study in rats over a 6 month period

Advanced age alone appears to be a risk factor for increased susceptibility to cardiac arrhythmias. We previously observed in the aged rat heart that sinus rhythm ventricular activation is delayed and characterized by abnormal epicardial patterns although conduction velocity is normal. While these findings relate to an advanced stage of aging, it is not yet known when and how ventricular electrical impairment originates and which is the underlying substrate. To address these points, we performed continuous telemetry ECG recordings in freely moving rats over a six-month period to monitor ECG waveform changes, heart rate variability and the incidence of cardiac arrhythmias. At the end of the study, we performed in-vivo multiple lead epicardial recordings and histopathology of cardiac tissue. We found that the duration of ECG waves and intervals gradually increased and heart rate variability gradually decreased with age. Moreover, the incidence of cardiac arrhythmias gradually increased, with atrial arrhythmias exceeding ventricular arrhythmias. Epicardial multiple lead recordings confirmed abnormalities in ventricular activation patterns, likely attributable to distal conducting system dysfunctions. Microscopic analysis of aged heart specimens revealed multifocal connective tissue deposition and perinuclear myocytolysis in the atria. Our results demonstrate that aging gradually modifies the terminal part of the specialized cardiac conducting system, creating a substrate for increased arrhythmogenesis. These findings may open new therapeutic options in the management of cardiac arrhythmias in the elderly population.

Prevention of cardiac events caused by surgical stress in aged rats: simultaneously activating β2-adrenoceptor and inhibiting β1-adrenoceptor

Increased plasma catecholamine levels are associated with a high risk of perioperative cardiac events in aged individuals undergoing non-cardiac surgical interventions. Given the different effects of β1-adrenoreceptor (β1AR) and β2-adrenoreceptor (β2AR) stimulation by catecholamine in cardiomyocytes, this study evaluated whether simultaneous inhibition of β1AR and activation of β2AR is better than separate application in reducing the risk of perioperative cardiac events in aged rats undergoing non-cardiac surgery. Male aged Sprague-Dawley (SD) rats were divided into five groups. Normal group received no treatment. Surgery group received an abdominal surgery with hypoxia. β1- group, β2+ group, β2+ group and β1+β2+ group received surgery and hypoxia with metoprolol (100 mg/kg·d), fenoterol (250 μg/kg·d) or both, respectively. The drugs were given three days before surgery with treatment continued through post-surgical day 7. The results showed that simultaneous activation of β2AR with a β2AR agonist and inhibition of β1AR with a selective β1AR blocker normalized myocardial oxygen consumption, decreased myocardial damage, augmented cardiomyocyte survival, improved cardiac function, reduced the incidence of arrhythmia, thus decreasing the occurrence of cardiac events in perioperative aged rats undergoing non-cardiac surgery. The results demonstrated that combined use of β2AR agonist and β1AR blocker achieved better general effects than use of either one alone. Our results provide a new insight into preventing perioperative cardiac events for elderly patients undergoing surgical stress.

Beneficial effects of physical activity on baroreflex control in the elderly

The baroreflex mechanisms, by controlling autonomic outflow to the heart and circulation, contribute importantly to neural circulatory control. The main function of the baroreflex is to prevent wide fluctuations in arterial blood pressure and to maintain the physiological homeostasis under basal resting conditions and in response to acute stress. Baroreflex-mediated changes in autonomic outflow affect heart rate, myocardial contractility, and peripheral vascular resistance. The baroreflex control of heart rate is of particular interest in pathological conditions, since it has been associated with increased propensity for cardiac mortality and sudden death. Aging is associated with significant cardiovascular modifications. The changes in baroreflex function that occur with age have been systematically studied by several methodological approaches. The available evidence indicates a reduced arterial baroreflex control of heart rate favoring an increase in sympathetic and a decrease in parasympathetic drive to the heart as well as an impairment in the baroreceptor control of blood pressure. Both kinds of changes have resultant clinical implications. Exercise training can modulate the age-related decline in baroreflex function and the attending abnormalities in autonomic control, thus accounting for some of the beneficial effects of physical activity in reducing the risk of cardiovascular morbidity and mortality.

Upper thoracic epidural anaesthesia: effects of age on neural blockade and cardiovascular parameters

BACKGROUND

Segmental dose reduction with increasing age after thoracic epidural anaesthesia (TEA) has been documented. We hypothesised that after a fixed loading dose of ropivacaine at the T3-T4 level, increasing age would result in more extended analgesic spread. In addition, other aspects of neural blockade and haemodynamic changes were studied.

METHODS

Thirty-five lung surgery patients were included in three age groups. Thirty-one patients received an epidural catheter at the T3-T4 interspace followed by an injection of 8-ml ropivacaine 0.75%. Analgesia was assessed with pinprick and temperature discrimination. Motor block was tested using the Bromage and epidural scoring scale for arm movements score. An arterial line was inserted for invasive measurement of blood pressure, cardiac index (CI) and stroke volume (SV).

RESULTS

There was no influence of age on quality of TEA except for the caudal border of analgesia being somewhat lower in the middle and older age group compared with the young age group. Heart rate (6.0 ± 5.9, P < 0.001), mean arterial pressure (16.1 ± 15.6, P < 0.001), CI (0.55 ± 0.49, P < 0.001) and SV (9.6 ± 14.6, P = 0.001) decreased after TEA for the total group. Maximal reduction in heart rate after TEA was more extensive in the young age group compared with the other age groups. There was no effect of age on other cardiovascular parameters.

CONCLUSION

We were unable to demonstrate an effect of age on the maximal number of spinal segments blocked after TEA; however, the caudad spread of analgesia increased with advancing age. In addition, reduction of heart rate was greater in the youngest group.

Cardiovascular costs of working memory performance: effects of age and performance feedback

Ageing is associated with impaired working memory (WM) performance that may increase cardiovascular costs in older workers. Performance feedback (FB) was assumed to compensate for performance decline and reduce cardiovascular costs. Forty-eight younger (29 ± 3 yr) and 45 older (55 ± 4 yr) healthy workers had to perform a 0-back task (low WM load), 2-back task (high WM load) and 2-back task with FB (high WM load & FB). Age-related performance decline and enhanced blood pressure (BP) reactivity to WM load were found. The baroreflex sensitivity (BRS) decreased under high WM load in older workers compared to younger workers. The FB abolished age differences in omission rate and increased low frequency heart rate variability (HRV) in both age groups. Moreover, FB reduced heart rate in older workers and increased BRS as well as high frequency HRV in younger workers. The results suggest that older workers compensate for WM performance decline at cost of heightened BP due to age-related reductions of vagal tone and impairments of the baroreflex mechanism. The performance FB helps older workers to partly compensate for performance deficits and reduce cardiovascular costs by moderate decreases in sympathetic tone.

Influence of aging and chronic heart failure on temporal dispersion of myocardial repolarization

Background and purpose:

QT and T_peak-T_end (Te) intervals are associated with sudden cardiac death in patients with chronic heart failure (CHF). We studied age-dependent influence on short-term temporal dispersion of these two variables in patients with postischemic CHF.

Method:

We grouped 75 CHF and 53 healthy control subjects into three age subsets: ≤50 years, >50 years and ≤65 years, and >65 years. We then calculated the following indices: QT and Te variability index (QTVI and TeVI), the ratio between the short-term variability (STV) of QT or Te, and the STV of resting rate (RR) (QT/RR STV and Te/RR STV).

Results:

In all different age subgroups, patients with CHF showed a higher level of QTVI than age-matched control subjects (≤50 years: P < 0.0001; >50 years and ≤65 years: P < 0.05; >65 years: P < 0.05). Patients with CHF < 50 years old also had all repolarization variability indices higher than normal age-matched controls (TeVI, P < 0.05; QT/RR STV, P < 0.05; Te/RR STV, P < 0.05), whereas we did not find any difference between the two older classes of subjects. Both QTVI (r²: 0.178, P < 0.05) and TeVI (r²: 0.433, P < 0.001) were positively related to age in normal subjects, even if the first correlation was weaker than the second one.

Conclusion:

Our data showed that QTVI could be used in all ages to evaluate repolarization temporal liability, whereas the other indices are deeply influenced by age. Probably, the age-dependent increase in QTVI was more influenced by a reduction of RR variability reported in older normal subjects.