Metabolic syndrome and short‐term heart rate variability in young adults

Aims Heart rate variability (HRV) can be used to estimate autonomic nervous control of the cardiovascular system. In middle‐aged subjects, the metabolic syndrome (MetS) is associated with lower HRV. We hypothesized that alterations in autonomic balance are already present in young adults with the MetS, and analysed the association of short‐term HRV with the MetS (using the National Cholesterol Education Program definition), in 1889 subjects aged 24–39 years. Methods Short‐term (3 min) HRV analysis included high‐frequency (HF), low‐frequency (LF) and total (TP) spectral components of HRV and LF/HF ratio. Results The presence of the MetS was associated with lower HF, LF and TP in men and women, and with higher LF/HF ratio in women. In men, waist circumference was the strongest individual MetS component that associated with HRV. After adjustments for age and heart rate, MetS was associated with lower HF and higher LF/HF ratio in women, but only with a lower TP in men (all P < 0.05). Conclusions MetS is associated with lower HRV in young adults. The individual components of MetS are differentially associated with HRV in men and in women. Our results are consistent with lower vagal activity and a possible increase in sympathetic predominance in women with the MetS. This sex difference in vagal activity and sympathovagal balance may partly explain the greater increase in cardiovascular risk associated with MetS in women than in men.     

阻塞性睡眠呼吸暂停低通气综合征患者的自主神经功能的评估

目的采用24h动态心电图心率变异性分析,研究阻塞性睡眠呼吸暂停低通气综合征(OSAHS)的自主神经功能状态变化。方法入选我院诊断的OSAHS患者50例,并将其分为轻中度组和重度组2组。对照组为年龄相匹配的正常男性26名,所有受试者均在睡眠监测的同时进行24h动态心电图检查,并进行心率变异性分析。结果时域指标:轻中度组和重度组SDNN和pNN50明显低于对照组;重度组SDNNi和RMSSD明显降低。频域分析:重度组低频功率谱明显高于对照组,轻中度组和重度组的高频功率谱明显减低而低频功率谱/高频功率谱明显增高。结论OSAHS男性患者24h的自主神经功能状态发生了异常改变,并且与其病情的严重程度相关。     

Inflammation-related effects of adjuvant influenza A vaccination on platelet activation and cardiac autonomic function

Abstract. Lanza GA, Barone L, Scalone G, Pitocco D, Sgueglia GA, Mollo R, Nerla R, Zaccardi F, Ghirlanda G, Crea F (Istituto di Cardiologia; and Università Cattolica del Sacro Cuore, Roma; Italy). Inflammation‐related effects of adjuvant influenza A vaccination on platelet activation and cardiac autonomic function. J Intern Med 2010; 269 : 118–125. Background. Inflammation, platelet reactivity and cardiac autonomic dysfunction increase the risk of cardiovascular events, but the relationships between these prognostic markers are poorly defined. In this study, we investigated the effect of an inflammatory stimulus (influenza A vaccine) on platelet activation and cardiac autonomic function. Methods. We measured serum C‐reactive protein (CRP) and interleukin‐6 levels, monocyte–platelet aggregates (MPAs) and monocyte/platelet receptor expression before and after adjuvant influenza A vaccination in 28 patients with type II diabetes (mean age 62.1 ± 8 years, 18 men). Twenty‐four‐hour Holter electrocardiogram was recorded 24 h before and after vaccination; heart rate variability (HRV) was assessed as a measure of cardiac autonomic function. Results. Inflammatory cytokines, MPA formation and monocyte/platelet receptor expression increased after vaccination. CRP was 2.6 ± 2.8 and 7.1 ± 5.7 mg L^?1 48 h before and after vaccination, respectively (P < 0.0001). HRV parameters decreased after vaccination compared to baseline, with very low‐frequency amplitude showing the most significant change (34.6 ± 11.8 and 31.0 ± 10.2 ms 48 h before and after vaccination, respectively; P = 0.002). A significant correlation was found between percentage changes in CRP levels and in most HRV variables, with the most significant correlations between changes in CRP levels and changes in standard deviation of all normal RR intervals (r = 0.43; P = 0.02). Conclusions. Together with an inflammatory reaction, influenza A vaccine induced platelet activation and sympathovagal imbalance towards adrenergic predominance. Significant correlations were found between CRP levels and HRV parameters, suggesting a pathophysiological link between inflammation and cardiac autonomic regulation. The vaccine‐related platelet activation and cardiac autonomic dysfunction may transiently increase the risk of cardiovascular events.     

Changes in autonomic nervous activity during endoscopic retrograde cholangiopancreatography: a possible factor in cardiac complications

BACKGROUND AND AIMS: The changes of autonomic nervous activity during endoscopic retrograde cholangiopancreatography (ERCP) are closely related to the development of cardiovascular complications, such as arrhythmias and acute coronary syndrome. In the present study, the correlation between changes in hemodynamics and autonomic nervous activity during ERCP procedures was evaluated by analyzing heart rate variability and blood catecholamine levels. METHODS: Twenty-three patients who underwent ERCP (ERCP group) and 15 control subjects who were only premedicated (C group) were studied. Ambulant ECG, blood pressure, arterial oxygen saturation, and blood level of catecholamine were measured. Autonomic nervous function was assessed by analyzing the spectral analysis and 1/f fluctuation. The low frequency power (LF power; 0.04-0.15 Hz), high frequency power (HF power; 0.15-0.40 Hz, indicator of parasymapathetic tone), the ratio of LF power to HF power (LF/HF ratio, indicator of sympathetic tone), and 1/f fluctuation (indicator of pleasant mood) were calculated. RESULTS: Blood pressure and heart rate were increased and arterial oxygen saturation was decreased in the ERCP group during the endoscopic procedure. Changes in the parameters of autonomic nervous function (LF power, HF power, LF/HF ratio, and 1/f fluctuation) were significantly greater in the ERCP group than in the C group, especially during cholangiography. Moreover, blood levels of catecholamines were significantly increased during the ERCP procedure. In the C group, however, blood levels of catecholamines did not significantly change except directly after premedication. CONCLUSIONS: Autonomic nervous activity varied greatly during cholangiography, demonstrating that ERCP has more than a little influence on the cardiovascular system. The results of the present study indicated that attention should be focused on changes in hemodynamics in patients with cardiovascular complications by monitoring the aforementioned hemodynamic parameters during ERCP.     

A Twin Study of Metabolic Syndrome and Autonomic Tone

Introduction: One possible mechanism of higher cardiovascular mortality associated with the metabolic syndrome (MetS) may be through abnormal modulation in autonomic tone.
Methods and Results: We examined the association between the MetS and autonomic tone as measured by heart rate variability (HRV) among 288 twins from the Twins Heart Study (THS). Of the 288 participants, 151 (52%) had the MetS. The MetS was associated with decreased HRV across all frequency ranges, and each additional MetS risk factor was associated with lower HRV. After adjustment for several potential confounders, very-low frequency (P < 0.001), low frequency (P < 0.001), and total power (P = 0.02) spectra of HRV remained significantly lower in twins with a progressively higher number of MetS components (18–50% decrease comparing twins with 5 risk factors to those with no risk factors). Among 87 twin pairs who were discordant for the number of MetS components, a one-unit increment in MetS components was associated with an 8% smaller very-low frequency (p = 0.03) and a 15% smaller low frequency spectrum (P = 0.002) comparing each twin with his brother.
Conclusion: MetS was associated with lower HRV in a well-characterized sample of middle-aged male twins. This association persisted even after controlling for genetic and shared environmental factors accounted for by comparison within twin pairs. Abnormalities of autonomic tone, as evidenced by lower HRV, may be partly responsible for the higher rate of atrial fibrillation, coronary heart disease, cardiac death, and overall mortality seen in patients with the MetS.     

The relationship of autonomic function to age-related changes in left ventricular filling in normal subjects

Heart rate and age are independent variables associated withthe pattern of normal left ventricular filling. Since heartrate variability also varies with age, the relationship betweenthese and left ventricular filling in normal subjects was assessed.In 31 subjects (age range 21 to 71 years), power spectral analysisof heart rate variability was determined from 24 h Holter tapes,and left ventricular filling was assessed by Doppler echocardiography.Relationships between heart rate variability and left ventricularfilling were assessed by univariate and multivariate regressionanalyses. Total, low frequency and high frequency power eachsignificantly correlated with the peak filling velocity withatrial systole (A) (r=–0.70, P<0.0001; r=–0.69,P<0.0001; r=–0.54, P<0.01, respectively), but didnot correlate with measures of early diastolic left ventricularfilling. Although age and A were related (r=0.46, P<0.010),age was no longer a significant variable when measures of heartrate variability were included in the multivariate regressionmodel for A. Thus, the variability in measures of early diastolicfilling in normal subjects appears to be independent of measuresof heart rate variability, whereas, A is significantly associatedwith these measures.     

Evaluation of autonomic nervous function during upper gastrointestinal endoscopy using heart rate variability

To investigate autonomic nervous function during upper gastrointestinal endoscopy, we analyzed R-R interval variability from electrocardiograms obtained during endoscopy. Holter electrocardiogram recordings were made before and after premedication, and during endoscopy. Time- and frequency-domain analyses of heart rate variability were performed in 54 subjects premedicated with scopolamine butylbromide (SB group) and in 66 subjects premedicated with glucagon (G group). To determine the effect of autonomic imbalance on arrhythmia generation during endoscopy, subjects with arrhythmias (A group) were compared with subjects without arrhythmias (N group). In the SB group, high frequency spectral power (HF power; 0.15 to 0.40 Hz), which reflects parasympathetic activity, decreased significantly after premedication, and decreased further during endoscopy (P < 0.01). Moreover, HF power before premedication or during endoscopy in the A group was significantly lower than that in the N group (P < 0.01). This study suggests that the measurement of HF power prior to endoscopy can identify subjects with reduced HF power. This should allow the prevention of cardiovascular complications related to premedication and endoscope insertion. Received: June 25, 1999 / Accepted: June 23, 2000     

Circadian change of cardiac autonomic function in correlation with intra-esophageal pH

BACKGROUND AND AIM: Although autonomic alterations are observed in patients with gastroesophageal reflux disease (GERD), the influence of visceral receptor responses on the dynamics of autonomic function remains unknown. The aim of this study was to investigate the autonomic functional changes in association with intra-esophageal pH under ambulation. METHODS: Thirty patients referred for 48 h ambulatory pH monitoring underwent simultaneous 24 h cardiac monitoring for heart rate variability (HRV). We used linear mixed-effects models to estimate the relationship between esophageal acid exposure and power spectral analysis of HRV, including low-frequency power (0.04 < LF < 0.15 Hz), high-frequency power (0.15 < or = HF < 0.4 Hz), and LF/HF power ratio. RESULTS: Over the 24-h period, patients with pathological reflux had lower average LF and HF powers than patients with functional heartburn, but the LF/HF power ratios were similar for the two patient groups. As we stratified the data according to waking and sleeping times, a significantly higher HF power but lower LF/HF power ratio was found during sleeping time regardless of diagnosis. In the regression analysis, esophageal pH was positively associated with change (not basal tone) of both LF and HF powers during waking, but only with change of HF power during sleeping time. The significant associations between pH values and changes in HRV decreased gradually with time. The LF/HF power ratio did not alter significantly with pH. CONCLUSION: Esophageal acid exposure is generally associated with decreases in autonomic tone. A predominant parasympathetic fluctuation during sleeping and a superimposed sympathetic interaction during waking dictate diurnal characteristics of autonomic regulation.     

Cardiac autonomic functions in obese children

Objective: The autonomic nervous system is assumed to have a role in the pathophysiology of obesity. In this study, we evaluated the autonomic system by measuring heart rate variability (HRV) in obese children.Methods: Thirty-two obese and 30 healthy children (mean ages: 11.6±2.0 years and 11.0±2.9 years, respectively) were enrolled in the study. Obesity was defined as a body mass index higher than 97th percentile for age- and gender-specific reference values. All participants were free of any disease and none of them was receiving any medication. Twenty-four-hour ambulatory electrocardiographic recordings were obtained and the time-domain and frequency-domain indices of HRV were analyzed. The study group was evaluated with respect to insulin resistance by HOMA-IR values.Results: A significant decrease in calculated HRV variables was observed in obese children as compared to controls. The HRV alteration was found in both time-domain and frequency-domain parameters. The subgroup analysis of the study group revealed a significant decrease in all investigated HRV parameters in the insulin-resistant obese children compared to the non-insulin-resistant obese ones.Conclusions: Our results indicate that HRV is decreased in obese children, which implies parasympathetic withdrawal and sympathetic predominance. A marked decrease in HRV was observed in insulin-resistant obese children compared to their non-insulin-resistant counterparts. We propose that autonomic imbalance pertaining especially to insulin resistance may be involved in the pathogenesis of obesity in pediatric patientsConflict of interest:None declared.     

Metabolic syndrome and physical performance in elderly men: the osteoporotic fractures in men study

OBJECTIVES: To examine the association between metabolic syndrome (MetS) and objective measures of physical performance. DESIGN: Cross‐sectional analysis of the cohort study, the Osteoporotic Fractures in Men Study. SETTING: Six clinical sites in the United States. PARTICIPANTS: Five thousand four hundred fifty‐seven ambulatory men (mean age 73.6 ± 5.9). MEASUREMENTS: Physical performance assessed according to grip strength, narrow walk speed, walking speed, and time to complete five repeated chair stands. Individual scores were converted to quintiles (worst=1 to best=5; unable to complete=0) and summed for an overall score (mean 11.6 ± 4.3, range, 1–20). MetS was defined according to World Health Organization criteria that include evidence of glucose dysregulation (insulin resistance, diabetes mellitus, or hyperinsulinemia) and at least two additional characteristics: high blood pressure, low high‐density lipoprotein cholesterol, high triglycerides, obesity. RESULTS: More than one‐quarter (26.3%) of participants met criteria for MetS. In separate linear regression models, four of five MetS components were related to performance (P<.001); only high blood pressure was unrelated. Men with MetS had a 1.1‐point lower performance score (mean 10.8, 95% confidence interval (CI)=10.6–11.0) than men without MetS (mean 11.9, 95% CI=11.8–12.0) (P<.001), adjusting for age, race, education, and site. With further covariate adjustment, this difference was reduced but remained significant (β=?0.78, P<.001). A graded association was observed between number of MetS components (0, 1, 2, or ≥3) and performance (P for trend <.001). Findings were similar excluding men with diabetes mellitus or obese men. CONCLUSION: Metabolic dysregulation is related to objectively assessed poorer physical performance in relatively healthy older men.     

An automatic device for the assessment of cardiovascular autonomic function

Autonomic neuropathy is a common complication of diabetes mellitus and is associated with significant morbidity and possibly an increase in mortality. Despite this, however, autonomic dysfunction is not usually sought in the routine assessment of diabetic patients. We report the development and testing of a small, portable and reliable device that allows the routine testing of cardiac autonomic function in the outpatient setting with minimal inconvenience to the patient. This should facilitate the accurate assessment both of patients with symptoms suggestive of autonomic dysfunction and of autonomic function in research. © 1998 John Wiley & Sons, Ltd.     

Evaluation of autonomic nervous function in patients with essential hypertension complicated with peptic ulcer

BACKGROUND AND AIMS: The relationship between peptic ulcer, autonomic activity and the incidence of Helicobacter pylori infection in untreated hypertensive patients complicated with peptic ulcer were evaluated. METHODS: Ten hypertensive patients with peptic ulcer (HT-PU group), 15 untreated essential hypertensive patients without peptic ulcer (HT group) and 10 normal subjects (N group) were enrolled, and a power spectral analysis was performed in each subject. A biopsy urease test was used to detect infection by H. pylori. RESULTS: No significant differences were observed in the values of mean low-frequency (LF) power between the three groups. However, the mean high-frequency (HF) power in the HT-PU group was significantly greater than those of the HT and N groups (P<0.01). The mean LF/HF ratios in the HT-PU and HT groups were significantly greater than that of the N group (P<0.01). With respect to H. pylori infection, no significant differences between the three groups were observed. Sympathetic activity (LF power) was increased in the HT and HT-PU groups. Furthermore, parasympathetic activity (HF power) was increased in the HT-PU group. CONCLUSIONS: These findings suggest the participation of increased parasympathetic activity in peptic ulcer patients. Therefore, it is suggested that new techniques, such as spectral analysis of heart rate variability, as used in this study, will clarify the relationship between peptic ulcer and autonomic nervous function.     

Evaluation of autonomic modulation of lung function and heart rate in children with cystic fibrosis

The autonomic nervous system (ANS) plays an important role in modulating bronchial smooth muscle contractility, which is altered in cystic fibrosis (CF). A convenient approach to probe ANS regulation is the quantitative analysis of heart rate variability (HRV). The purpose of this study was to evaluate ANS regulation in children with CF and to investigate the influence of colonization by Pseudonomas aeruginosa via assessment of HRV in colonized CF (CCF) children and noncolonized CF (NCCF) children. Sixteen children with CF (7 CCF and 9 NCCF) and seven healthy age‐matched control children were enrolled in the study. Heart rate was recorded for 10 min at rest in the supine and standing positions and HRV analysis was carried out using autoregressive spectral analysis. The CCF group was characterized by lower forced expiratory volume than NCCF, indicating an impairment of respiratory function. The HRV parameters further confirmed the possible sympathetic overactivity in CCF. Children with CF exhibited hyperactivity of the sympathetic nervous system. In particular, the CCF group presented a greater impairment of ANS modulation. Both CCF and NCCF children showed lower supine vagal activation in the HRV indices related to sympathetic activation and reduction of indices indicating vagal activity with the postural change from supine to standing when compared to the NCCF group.     

Effect of coronary artery bypass grafting on cardiac parasympathetic nervous function.

Low heart rate variability (HRV) is a predictor of a poor outcome after myocardial infarction. To determine whether coronary artery bypass grafting (CABG) has any effect on HRV, the power spectrum components of HRV were measured in 35 patients before, and 1 week after, CABG. Significant attenuation of all spectral components of HRV were found after CABG (P less than 0.001). High frequency (HF) power decreased to one third of the preoperative level, mid-frequency (MF) power to as little as one fifteenth and low frequency (LF) power to one seventh of the preoperative level. No significant restoration in MF or HF powers occurred during the 6-week follow-up period. The results suggest that CABG causes a marked attenuation of HRV. The prognostic significance of this attenuation is not known.