Power spectral analysis of heart rate variability in children and adolescents with IDDM

Determinants of the heart rate variability in type 1 diabetes mellitus

Background

Evaluation of heart rate variability (HRV) detects the early subclinical alterations of the autonomic nervous system. Thus, impaired HRV is the earliest subclinical marker of cardiac autonomic neuropathy (CAN) in type 1 diabetes mellitus (T1DM).

Objectives

We aimed to explore the HRV parameters in asymptomatic T1DM patients and compare them with the results obtained in healthy subjects. Potential associations between HRV parameters and the established risk factors for CAN and cardiovascular diseases were also investigated.

Methods

Seventy T1DM patients (38 ± 12 years, 46 females) and 30 healthy subjects were enrolled into the study. For HRV analysis, beat-to-beat heart rate was recorded for 30 min. The less noisy 5-min segment of the recording was analyzed by Bittium Cardiac Navigator HRV analysis software. Time domain, frequency domain, and nonlinear indices were calculated.

Results

Regarding ratio of low to high frequency component (LF/HF), no differences were found between the two populations (p = 0.227). All the further, time domain, frequency domain, and nonlinear HRV indices were significantly lower in T1DM patients (each p < 0.001). In multiple linear models, disease duration remained the only independent predictor of LF/HF ratio (p = 0.019). HbA1c was found to be significant independent predictor of all further time domain (SDNN, p < 0.001; rMSSD, p < 0.001), frequency domain (VLF, p < 0.001; LF, p = 0.002; HF, p = 0.006; Total Power, p = 0.002), and nonlinear indices (SD1, p = 0.006; SD2, p = 0.007), alone, or in combination with other factors, such as age or body mass index.

Conclusion

Asymptomatic T1DM patients have significantly reduced overall HRV as compared with healthy subjects, indicating subclinical CAN. Quality of the glycemic control is important determinant of HRV among T1DM patients. This relationship is independent of other risk factors for CAN or cardiovascular diseases.

Information-based analysis of the coupling between brain and heart reactions to olfactory stimulation

BACKGROUND

Analysis of the heart activity is one of the important areas of research in biomedical science and engineering. For this purpose, scientists analyze the activity of the heart in various conditions. Since the brain controls the heart's activity, a relationship should exist among their activities.

OBJECTIVE

In this research, for the first time the coupling between heart and brain activities was analyzed by information-based analysis.

METHODS

Considering Shannon entropy as the indicator of the information of a system, we recorded electroencephalogram (EEG) and electrocardiogram (ECG) signals of 13 participants (7 M, 6 F, 18-22 years old) in different external stimulations (using pineapple, banana, vanilla, and lemon flavors as olfactory stimuli) and evaluated how the information of EEG signals and R-R time series (as heart rate variability (HRV)) are linked.

RESULTS

The results indicate that the changes in the information of the R-R time series and EEG signals are strongly correlated (ρ=-0.9566).

CONCLUSION

We conclude that heart and brain activities are related.

Asymptomatic postprandial hypotension in patients with diabetes: The KAMOGAWA-HBP study

AIMS/INTRODUCTION

Postprandial hypotension (PPH) refers to a decrease in systolic blood pressure by ≥20 or to <90 mmHg from baseline ≥100 mmHg within 2 h of a meal. Previous studies have reported an association between diabetes and PPH; however, the characteristics of PPH in patients with diabetes remain unclear.

MATERIALS AND METHODS

We recruited patients with diabetes who regularly attended the diabetes outpatient clinic. Participants were instructed to carry out three sets of blood pressure measurements at six time points: just before and right after, and 30, 60, 90 and 120 min after their main meal of the day. Data on PPH symptoms were collected during an interview. To investigate the relationships between explanatory variables, PPH and associated symptoms, we carried out multiple logistic regression analyses.

RESULTS

We analyzed data from 300 participants. There were 150 (50.0%) participants with PPH. Systolic blood pressure before a meal was significantly associated with PPH (odds ratio [OR] 1.56, 95% confidence interval [CI] 1.30-1.86, P < 0.001), after adjusting for covariates. Furthermore, age (OR 1.08, 95% CI 1.01-1.16, P = 0.027), hemoglobin A1c level (OR 2.39, 95% CI 1.01-5.64, P = 0.030) and coefficients of variation of R-R intervals (OR 0.79, 95% CI 0.65-0.97, P = 0.032) were significantly associated with asymptomatic PPH.

CONCLUSIONS

Half of the present study outpatients with diabetes had PPH. High systolic blood pressure before a meal was significantly associated with the risk of PPH. Older adults and patients with higher levels of hemoglobin A1c or an autonomic dysfunction might have difficulties recognizing symptoms of PPH.

Early identification of cardiac autonomic neuropathy using complexity analysis in children with type 1 diabetes

AIM

In children and adolescents, there are significant limitations to detecting cardiac autonomic neuropathy (CAN), an important contributor to morbidity and mortality in adults with type 1 diabetes (T1D). The analysis of heart rate variability (HRV) is one method available to detect CAN. Some evidence shows traditional linear HRV measures detect abnormalities in youth with T1D. In this study, we aimed to assess whether non-linear complexity analysis of HRV would assist identification of CAN in youth with T1D and to assess contributory factors.

METHODS

We studied 19 youth with T1D and 17 healthy controls. Each had an electrocardiogram recorded continuously for 10 min, at a sampling frequency of 1000 Hz. Using Labview software and an algorithm for complexity analysis, along with standard time-domain and spectral analysis, recordings of the electrocardiogram were analysed to detect differences in HRV between groups.

RESULTS

Youth with T1D had significantly higher sample entropy than controls (P = 0.015) suggesting increased complexity in HRV, but similar detrended fluctuation analysis (P = 0.68). Youth with T1D also had increased % high frequency power (P = 0.017) and reduced mid-frequency power (P = 0.019) on spectral analysis. There were no differences in heart rate or blood pressure responses to standing, or time-domain analysis of HRV. Within the T1D group, sample entropy correlated strongly with triglycerides (r = 0.76, P = 0.001) and detrended fluctuation analysis correlated strongly with serum potassium (r = -0.86, P < 0.001).

CONCLUSIONS

Complexity analysis of HRV, particularly using sample entropy, may aid detection of CAN in youth with T1D.

Assessing heart rate variability in type 1 diabetes mellitus-Psychosocial stress a possible confounder

BACKGROUND

Autonomic neuropathy (AN) commonly arises as a long-term complication in diabetes mellitus and can be diagnosed from heart rate variability (HRV), calculated from electrocardiogram recordings. Psychosocial stress also affects HRV and could be one of several confounders for cardiac AN. The present work investigated the impact of psychosocial stress on HRV in individuals with type 1 diabetes mellitus (T1DM) and assessed the use of salivary cortisol as a biomarker for psychosocial stress in this context.

METHODS

A total of 167 individuals 6-60 years old (113 with T1DM and 54 healthy controls) underwent 24-hr ECG recordings with HRV analysis. Salivary cortisol was sampled thrice during the registration day. Perceived psychosocial stress along with other factors of possible importance for the interpretation of HRV was documented in a diary.

RESULTS

Heart rate variability (high-frequency power during sleep) was reduced (p < .05) with older age, longer diabetes duration, higher mean glucose levels, physical inactivity, and perceived psychosocial stress. Salivary cortisol levels in the evening were increased (p < .05) in women in ovulation phase, in individuals with preceding hypoglycemia or with hyperglycemia. The amplitude of salivary cortisol was reduced (p < .05) with the presence of perceived psychosocial stress, but only in adult healthy controls, not in individuals with diabetes.

CONCLUSION

Psychosocial stress might be a confounder for reduced HRV when diagnosing cardiac AN in T1DM. Salivary cortisol is, however, not a useful biomarker for psychosocial stress in diabetes since the physiological stress of both hypoglycemia and hyperglycemia seems to overrule the effect of psychosocial stress on cortisol.

Diabetic neuropathy in children and adolescents with type 1 diabetes mellitus: Diagnosis, pathogenesis, and associated genetic markers

Diabetic neuropathy (DN) is a common long-term complication of type 1 (T1D) and type 2 (T2D) diabetes mellitus, with significant morbidity and mortality. DN is defined as impaired function of the autonomic and/or peripheral nervous system, often subclinical, particularly in children and adolescents with T1D. Nerve conduction studies (NCS) and skin biopsies are considered gold-standard methods in the assessment of DN. Multiple environmental and genetic factors are involved in the pathogenesis of DN. Specifically, the role of metabolic control and glycemic variability is of paramount importance. A number of recently identified genes, including the AKR1B1, VEGF, MTHFR, APOE, and ACE genes, contribute significantly in the pathogenesis of DN. These genes may serve as biomarkers to predict future DN development or treatment response. In addition, they may serve as the basis for the development of new medications or gene therapy. In this review, the diagnostic evaluation, pathogenesis, and associated genetic markers of DN in children and adolescents with T1D are presented and discussed.

Cardiac autonomic neuropathy in nonobese young adults with type 1 diabetes

PURPOSE

The aim of this study was to evaluate the prevalence and risk factors for cardiac autonomic neuropathy (CAN) in nonobese nonobese young type 1 diabetes mellitus (T1DM) patients without micro- or macrovascular complications.

METHODS

CAN was assessed in 95 patients with T1DM, aged 18-29 years, using standard cardiovascular reflex tests - heart rate response to deep breathing, standing, and the Valsalva maneuver and blood pressure response to standing. Furthermore, power spectral analyses of overall heart rate variability (HRV), standard deviation of NN intervals (SDNN), and total power (TP) were tested with DiCAN. CAN was defined as abnormal results for at least 1 of the 4 cardiovascular reflex tests.

RESULTS

The prevalence of CAN was 12.6%. The frequency of one and 2 abnormal reflex tests was 10.5% and 2.1%, respectively. No significant differences were observed in age, sex, mean hemoglobin A1c (HbA1c) level, and duration of diabetes with respect to presence of CAN. Patients with CAN exhibited lower overall HRV parameters (SDNN and TP) compared with those without CAN even though there was no statistical significance. In multivariable analyses, higher mean HbA1c level was significantly associated with lower overall HRV (β=-44.42, P=0.002 for SDNN and β=-2.82, P&lt;0.001 for TP).

CONCLUSION

CAN can be detected in 12.6% of young adult T1DM patients even without other micro- or macrovascular complications. Glycemic control is the main determinant to maintain overall HRV and prevent CAN.

Comparison of Baroreflex Sensitivity and Cardiac Autonomic Function Between Adolescent Athlete and Non-athlete Boys - A Cross-Sectional Study

Introduction: It is well known that regular physical activity improves cardiovascular health, and higher baroreflex sensitivity and heart rate variability are associated with cardiovascular health. Adolescence is the age when an individual’s behavior is easily modified; early intervention at this stage in terms of physical conditioning or training prevents future cardiovascular risk. Hence, we conceived the present study to assess and compare the baroreflex sensitivity and autonomic function between adolescent athletes and non-athletes.

Methods: We recruited school going athletes (n = 30) and non-athlete boys (n = 30) in the 10–19 age group after obtaining their assent and consent from their parents. We assessed height, weight, heart rate, blood pressure, baroreflex sensitivity, and cardiac autonomic function. Comparison between groups was made using the unpaired t-test for height, weight, body mass index, heart rate, blood pressure, and baroreflex sensitivity and using Mann-Whitney U test for cardiac autonomic function parameters.

Results: There was a trend for higher baroreflex sensitivity in athletes. Heart rate variability (total power and SDNN) was higher in athletes. The parasympathetic tone was higher in terms of higher RMSSD, and higher HF power. Parasympathetic reactivity was higher in athletes in terms of higher 30:15 ratio and EI ratio.

Conclusion: Athletic level physical conditioning has a positive influence on baroreflex function and autonomic function that may prove beneficial to the adolescents’ cardiovascular health.

Cardiac autonomic function in children with type 1 diabetes

Cardiovascular autonomic neuropathy (CAN) is a major complication of type 1 diabetes (T1D). This study aimed to evaluate cardiac autonomic nervous system (ANS) function in children with T1D and its relation to different demographic, clinical and laboratory variable. This cross-sectional study included 60 children with T1D (mean age = 15.1 ± 3.3 years; duration of diabetes = 7.95 ± 3.83 years). The following 8 non-invasive autonomic testing were used for evaluation: heart rate at rest and in response to active standing (30:15 ratio), deep breathing and Valsalva maneuver (indicating parasympathetic function); blood pressure response to standing (orthostatic hypotension or OH), sustained handgrip and cold; and heart rate response to standing or positional orthostatic tachycardia syndrome or POTs (indicating sympathetic function). None had clinically manifest CAN. Compared to healthy children (5%), 36.67% of children with T1D had ≥ 2 abnormal tests (i.e., CAN) (P = 0.0001) which included significantly abnormal heart rate response to standing (POTs) (P = 0.052), active standing (30:15 ratio) (P = 0.0001) and Valsalva maneuver (P = 0.0001), indicating parasympathetic autonomic dysfunction, and blood pressure response to cold (P = 0.01), indicating sympathetic autonomic dysfunction. 54.55, 27.27 and 18.18% had early, definite and severe dysfunction of ANS. All patients had sensorimotor peripheral neuropathy. The longer duration of diabetes (> 5 years), presence of diabetic complications and worse glycemic control were significantly associated with CAN.

CONCLUSIONS

The study concluded that both parasympathetic and sympathetic autonomic dysfunctions are common in children with T1D particularly with longer duration of diabetes and presence of microvascular complications. What is Known: • Cardiovascular autonomic neuropathy (CAN) is a major complication of type 1 diabetes (T1D). • Limited studies evaluated CAN in children with T1D. What is New: • CAN is common in children with T1D. • Cardiac autonomic functions should be assessed in children with T1D particularly in presence of microvascular complications.

QT interval, corrected for heart rate, is associated with HbA1c concentration and autonomic function in diabetes

AIMS

To examine QT intervals corrected for heart rate (QTc) in adolescents with Type 1 diabetes compared with control subjects, and to determine associations with metabolic control and autonomic function.

METHODS

Resting electrocardiogram recordings of 142 adolescents with Type 1 diabetes [mean (sd) age 15.3 (2.0) years, diabetes duration 9.0 (3.5) years, HbA1c 71 (17) mmol/mol or 8.7 (1.6)%] and 125 control subjects [mean (sd) age 15.7 (2.5) years] were used to calculate QTc duration and derive mean heart rate and heart rate variability (HRV) values. Linear and logistic regression models were used to examine the associations between QTc, metabolic control and autonomic function (HRV and pupillary function).

RESULTS

QTc duration was not significantly different between subjects with Type 1 diabetes and control subjects (mean duration 392 vs 391 ms; P = 0.65). In the Type 1 diabetes group, QTc was positively associated with HbA1c [β = 4 (95% CI 2, 6); P < 0.001] and inversely associated with severe hypoglycaemic events [β = -10 (95% CI -20,-2); P = 0.01], less insulin/kg [β = -12 (95% CI -22, -2); P = 0.024] and less HRV. In the Type 1 diabetes group, QTc in the highest quintile (≥409 ms) vs quintiles 1-4 had more pupillary abnormalities (83 vs 56%; P = 0.03), lower pupillary maximum constriction velocity (4.8 vs 5.3 mm/s; P = 0.04), higher heart rate (78 vs 72 beats per min; P = 0.02) and lower HRV (standard deviation of mean NN intervals 4.0 vs 4.3 ms, P = 0.004 and root-mean-square difference of successive NN intervals 3.7 vs 4.1 ms; P = 0.004).

CONCLUSIONS

Although there are concerns about hypoglycaemia in general in people with Type 1 diabetes, chronic hyperglycaemia, rather than intermittent hypoglycaemia, appears to be more deleterious to autonomic cardiac function, even in adolescence. Longer QTc was associated with higher HbA1c concentration, lower risk of hypoglycaemia and autonomic dysfunction. Longitudinal studies are warranted.

Gastric Emptying Is More Rapid in Adolescents With Type 1 Diabetes and Impacts on Postprandial Glycemia

CONTEXT

Gastric emptying is a critical determinant of postprandial glycemic control in health and type 1 diabetes. There are few studies that assess the relationship between gastric emptying and postprandial glycaemia in adolescents with type 1 diabetes.

OBJECTIVE

The objectives of the study were to quantify gastric emptying in adolescents with type 1 diabetes and examine its relationship to postprandial glycaemia and autonomic function.

DESIGN

This was a case-control study. Gastric half-emptying time of a solid meal was measured by a (13)C-octanoate breath test. Cardio-autonomic function was measured by heart rate variability. Chronic and postprandial gastrointestinal symptoms were evaluated by questionnaire and visual analog scales. Blood glucose concentrations were monitored frequently during the study.

SETTING

The study was conducted at a tertiary pediatric hospital in South Australia.

PARTICIPANTS

Thirty adolescents (aged 15 ± 2.5 y) with type 1 diabetes and age- and sex-matched controls (gastric emptying, n = 20; heart rate variability, n = 135) participated in the study.

MAIN OUTCOME

Gastric half-emptying time was the main outcome in the study.

RESULTS

Gastric emptying was more rapid in subjects with type 1 diabetes than controls [median half emptying time 78 (interquartile range 61-99) vs 109 (interquartile range 71-124) min, P = .02]. The postprandial rise in blood glucose at 60 minutes was strongly related to gastric half-emptying time (R = -0.65, P = .0001). Gastric emptying was slower in subjects with fasting hyperglycemia but was not related to heart rate variability. Nausea, bloating, and anxiety were related to fasting glycemia (P = .03).

CONCLUSION

Rapid gastric emptying is a major determinant of postprandial glycemia in adolescents with type 1 diabetes. This observation has significant implications for therapy.

Short-term heart rate variability in a population-based sample of 10-year-old children

Heart rate variability (HRV) is a non-invasive quantitative marker of cardiac autonomic function derived from continuous electrocardiogram (ECG) recordings. Normative HRV values and development factors have not been established in pediatric populations. The objective was to derive referent time- and frequency-domain HRV values for a population-based sample of children. Children aged 9-11 years (N = 1,036) participated in the Québec Longitudinal Study of Child Development cohort cardiovascular health screening. Registered nurses measured anthropometrics (height, weight) and children wore an ambulatory Holter monitor to continuously record an ECG signal. HRV variables included time (SDNN, pNN50, RMSSD, SDANN) and frequency (HF, LF, LF/HF ratio) domain variables. Normative HRV values, stratified by age, sex, and heart rate, are presented. Greater heart rate (β avg  = -0.60, R avg (2)  = 0.39), pubertal maturation (β avg = -0.11, R avg (2)  = 0.01), later ECG recording times (β avg = -0.19, R avg (2)  = 0.07), and higher diastolic blood pressure (β avg = -0.11, R avg (2)  = 0.01) were significantly associated with reduced HRV in 10-year-old children. The normative HRV values permit clinicians to monitor, describe, and establish pediatric nosologies in primary care and research settings, which may improve treatment of diseases associated with HRV in children. By better understanding existing values, the practical applicability of HRV among clinicians will be enhanced. Lastly, developmental (e.g., puberty) and procedural (e.g., recording time) factors were identified that will improve recording procedures and interpretation of results.

Autonomic dysfunction: a possible pathophysiological pathway underlying the association between sleep and obesity in children at-risk for obesity

While mounting evidence suggests that sleep plays an important role in the etiology of obesity, the underlying pathogenic pathways are complex and unresolved. Experimental sleep deprivation studies demonstrate sympathovagal imbalance, indicative of diminished parasympathetic activity and/or heightened sympathetic activity, is consequent to poor sleep. Further, obese children exhibit sympathovagal imbalance, particularly during the night, compared to non-obese children. The question remains whether sympathovagal imbalance is one potential pathophysiological pathway underlying the association between sleep and obesity. The aim of the present study was to examine whether sympathovagal imbalance contributed to the association between sleep and obesity in children. Participants included 564 children aged 10 to 12 years (M = 11.67, SD = 0.95; 43.5% girls) from the QUALITY Cohort, a longitudinal study of children at-risk for the development of obesity. While children were at-risk due to confirmed parental obesity status, 57.7% of children were of normal body mass index (5-85th percentile). Sleep duration, sleep timing, and sleep disturbances were based on child- and parent-report. Anthropometrics were measured for central adiposity (waist circumference) and body composition (body mass index, fat mass index). Sympathovagal imbalance was derived from heart rate variability spectral analyses. Estimated path coefficients revealed that sympathovagal imbalance partially contributed to the association between poor sleep (later bedtimes, sleep-disordered breathing) and obesity. These findings highlight the importance of better understanding sympathovagal imbalance and its role in the etiology and maintenance of obesity. Future research should consider investigating nocturnal sympathovagal balance in youth.

An evaluation of heart rate variability and its modifying factors in children with type 1 diabetes

OBJECTIVE

To evaluate heart rate variability by Holter monitoring in type 1 diabetic children compared with a healthy control group and determine the factors modifying heart rate variability.

METHODS

This was designed as a prospective study comparing 28 patients, diagnosed with type 1 diabetes and under follow-up, with 27 healthy control group subjects.

RESULTS

The patients were aged 9.9 ± 4.2 years in the diabetic group, including 13 (46.5%) girls and 15 (53.5%) boys. The healthy control group comprised 20 (74%) girls and seven boys (26%) with an average age of 8.6 ± 3.7 years. The search for factors modifying heart rate variability yielded the following correlations: for the time-dependent variables, negative between age and both average and maximal heart rate (r = -0.263 and -0.460, respectively), negative between haemoglobin A1c and percentage of differences between adjacent RR intervals >50 ms, positive between diabetes duration and square root of the mean of the sum of squares of differences between adjacent NN intervals. The average heart rate and percentage of differences between adjacent RR intervals >50 ms was significantly higher in the girls than the boys in all groups. With regard to the frequency-dependent factors affecting heart rate variability, correlations were found between haemoglobin A1c level and both total power and very low frequency (r = -0.751 and -0.644) and between very low frequency and diabetes duration.

CONCLUSION

A reduction in heart rate variability parameters was observed in type 1 diabetes mellitus patients who had a long disease duration or were poorly controlled, as compared with healthy controls.

Heart rate variability in pubertal girls with type 1 diabetes: its relationship with glycaemic control, insulin resistance and hyperandrogenism

OBJECTIVE

To examine the association between glycaemic control, insulin resistance and hyperandrogenism on cardiac autonomic function in peripubertal girls with type 1 diabetes.

DESIGN

Prospective, clinic-based study of 125 girls with diabetes and 46 age-matched nondiabetic girls.

MEASUREMENTS

Heart rate variability (HRV) parameters derived from a 10-min ECG recording using LabChart Pro were as follows: standard deviation of mean NN intervals (SDNN), where NN = adjacent QRS complexes; root mean squared difference of successive NN intervals (RMSSD) - estimates of overall HRV; and low-/high-frequency (LF:HF) ratio - an estimate of the sympathovagal balance. Androgens and sex hormone binding globulin (SHBG) were measured in girls with diabetes, and free androgen index (FAI) calculated. HRV and anthropometry were measured in nondiabetic controls.

RESULTS

Adolescents with diabetes (median age 15·1 years [13·3-16·0], diabetes duration 7·0 years [4·6-10·0] and median HbA1c 8·4% [7·5-9·3]) had higher HR and lower HRV compared with controls. Using multivariate models in the diabetes group, higher HR was associated with higher HbA1c, total daily dose insulin/kg body weight and systolic BP standard deviation scores (SDS), whilst reduced HRV was associated with higher HbA1c (SDNN, RMSSD and LF:HF ratio), lower SHBG (SDNN and RMSSD) and higher weight SDS (LF:HF ratio). Higher FAI was associated with higher HR and reduced HRV measures in the univariate analyses only.

CONCLUSIONS

In adolescent girls with diabetes, reduced HRV parameters are associated with worse glycaemic control, lower SHBG and higher weight SDS. SHBG should be considered in the cardiac risk models for this population.

Exercise training improves cardiac autonomic nervous system activity in type 1 diabetic children

[Purpose] We investigated the effect exercise training has on cardiac autonomic nervous system (ANS) and cardiovascular risk profiles in children with type 1 diabetes mellitus (DM). [Subjects] Fifteen type 1 DM children (all boys; 13.0±1.0 years of age) were enrolled in the study. [Methods] The subjects received exercise training three times a week in a 12-week program. Each child was asked to walk on a treadmill to achieve an exercise intensity of VO₂max 60%. ANS activity was measured by power spectral analysis of the electrocardiogram (ECG). Blood samples were obtained for serum lipid profiles. To evaluate Doppler-shifted Fourier pulsatility index (PI) analysis, a 5-MHz continuous wave Doppler (VASCULAB D10) set was used to measure forward blood flow velocity (FLOW) in the radial artery. [Results] Total and low-frequency (LF) power of heart rate variability increased significantly after exercise intervention. Total cholesterol (TC) levels were significant lower after exercise intervention. Total and high-frequency (HF) power were significantly correlated with higher TC levels, but diastolic blood pressure and HF was significantly correlated with lower TC levels. [Conclusion] Regular exercise intervention should be prescribed for children with type 1 DM.

Relationship between autonomic nervous system function and continuous interstitial glucose measurement in patients with type 2 diabetes

AIMS

The Aim of the present study was to examine whether there is a relationship between autonomic nervous system function and glycemic variability (GV) in patients with type 2 diabetes (T2D).

METHODS

A total of 50 (29 males) patients with T2D (mean age 58.4 ± 9.9 years, median diabetes duration 5.5 [IQR 2.0-9.25] years), on oral antidiabetic agents, underwent ECG recording and subcutaneous glucose monitoring, simultaneously and continuously, for 24 hours.

RESULTS

After adjustment for HbA1c and diabetes duration, total power of heart rate variability (HRV) was inversely associated with the standard deviation of the mean interstitial tissue glucose (MITG) and with the M-value during the entire recording (r: -0.29, P = 0.052; r: -0.30, P = 0.047, resp.) and during the night (r: -0.29, P = 0.047; r: -0.31, P = 0.03, resp.). Most of the HRV time-domain indices were significantly correlated with standard deviation of the MITG and the M-value. These correlations were stronger for the HRV recordings during the night. No significant association was found between HRV parameters and MAGE.

CONCLUSIONS

HRV is inversely associated with GV in patients with T2D, which might be a sign of causation between GV and autonomic dysfunction. Prospective studies are needed to further investigate the importance of GV in the pathogenesis of long-term complications of diabetes.

The assessment of cardiac autonomic functions in adolescents with a family history of premature atherosclerosis

OBJECTIVES

Subclinical atherosclerosis has been recently detected in adolescents with a family history of premature atherosclerosis. However, no studies in the literature have assessed the cardiac autonomic functions of these adolescents. The aim of this study was to evaluate the cardiac autonomic functions of adolescents with a family history of premature atherosclerosis compared with those of age- and gender-matched adolescents without a family history of atherosclerosis.

METHOD

We evaluated the cardiac autonomic functions of 36 adolescents with a family history of premature atherosclerosis (Group 1) and compared them with those of 31 age- and gender-matched adolescents whose parents did not have premature atherosclerosis (Group 2). Twenty-four-hour time domain (standard deviation of all normal sinus RR intervals [SDNN], standard deviation of the mean of normal RR intervals in each 5-minute segment [SDANN], root-mean-square differences in successive RR intervals) and frequency domain (very low frequency, low frequency, high frequency, low frequency/high frequency) parameters of heart rate variability were used for the evaluation of cardiac autonomic functions.

RESULTS

There were no differences in the time and frequency domain parameters of heart rate variability between the two groups. Heart rate was negatively correlated with SDNN (r=-0.278, p=0.035), while age was significantly correlated with root-mean-square differences in successive RR intervals, high frequency, low frequency and low frequency/high frequency (r=-0.264, -0.370, 0.265 and 0.374, respectively; p<0.05 for all).

CONCLUSION

We found that the cardiac autonomic functions of adolescents with a family history of premature atherosclerosis were not different compared with those of adolescents without a positive family history of premature atherosclerosis. It appears that subclinical atherosclerosis does not reach a critical value such that it can alter cardiac autonomic functions in adolescence.

Relationship between autonomic nervous system activity during sleep and fasting glucose in Japanese workers

Although autonomic nervous system activity is reportedly related to diurnal glucose tolerance impairment, the relationship with glucose tolerance during sleep is unclear. Since work styles have recently diversified, it is important to assess the effect of sleep on workers' health. Elucidation of the relationship between autonomic nervous system activity during sleep and glucose tolerance in workers may facilitate preventive measures against diabetes using non-pharmacological means (e.g., sleep hygiene education, relaxation techniques and stress management). We examined whether autonomic nervous system activity during sleep is related to fasting glucose or glycated hemoglobin (HbA1c) in individuals with either normal or impaired fasting glucose tolerance. The subjects were 77 apparently healthy Japanese workers with normal or impaired fasting glucose. We used high frequency (HF) and the ratio of low frequency to high frequency (LF/HF) obtained by pulse wave analysis to estimate autonomic nervous system activity. The data were analyzed using a generalized estimating equation adjusted for potential confounders (age, gender, engagement in shift work, sleep duration, and body mass index). Fasting glucose was significantly negatively related to HF, the parasympathetic component during sleep. Our results suggest that parasympathetic activity during sleep is associated with fasting glucose in apparently healthy Japanese workers.

Modified orthostatic load for spectral analysis of short-term heart rate variability improves the sensitivity of autonomic dysfunction assessment

AIM

To evaluate the impact of orthostatic load for sensitivity of short-term spectral analysis of heart rate variability (HRV) assessment of potential early autonomic dysfunction in diabetes mellitus.

METHODS

Comparison of results of short-term time- and frequency-domain analysis of HRV during single positions and during modified orthostatic load (supine 1-standing-supine 2, each position 300 s) in diabetic subjects with good glycemic control (n=80, age 38+/-14, diabetes duration 16+/-10 years) and without autonomic neuropathy as assessed by a standard bedside reflex test battery, and in nondiabetic controls (n=150, age 40+/-13 years).

RESULTS

None of the short-term frequency-domain parameters [absolute and logarithmic (LN) values of spectral powers in total- (TF), low- (LF), and high-frequency (HF) bands and its centroid frequencies] as obtained in single positions "supine" or "standing" revealed a significant difference between well-controlled patients and healthy controls (P>.3). However, during modified orthostatic load, significant differences in DeltaLN TF((supine 1-supine 2)) and in DeltaLN LF((supine 1-supine 2)) as well as in DeltaLN LF((standing-supine 2)) values between diabetic and healthy subjects were recorded [-0.2+/-0.5 vs. -0.1+/-0.4 LN (ms(2)), P=.05; -0.3+/-0.8 vs. 0.1+/-0.7 LN (ms(2)), P=.001 and 0.2+/-1.0 vs. 0.4+/-0.9 LN (ms(2)), P=.05, respectively] with insignificant intergroup differences in related centroid frequencies. This finding suggests a delayed recovery of LF spectral power in diabetic subjects after orthostatic challenge.

CONCLUSIONS

When compared with single position measurements, the modified orthostatic load protocol improves the sensitivity of short-term HRV examination. In well-controlled diabetic subjects without cardiovascular autonomic neuropathy (as excluded by standard cardiovascular reflex testing), the delayed recovery of LF band spectral power after orthostatic load with standing up indicates diminished parasympathetic activation.

Cardiac autonomic diabetic neuropathy

Cardiovascular autonomic diabetic neuropathy (CADN) is one of the most common diabetes-associated complications. Disturbed heart rate variability (HRV) is very often the earliest symptom, even in clinically asymptomatic patients. The following article offers a topical overview for those working or interested in the fields of diabetology and cardiology.

Impact of glycemic control, disease duration, and exercise on heart rate variability in children with type 1 diabetes mellitus

BACKGROUND/PURPOSE

Type 1 diabetes is commonly associated with autonomic neuropathy. The present study investigated the influences of glycemic control, disease duration (DD), and exercise on autonomic nervous function in children with type 1 diabetes by analysis of their heart rate variability (HRV).

METHODS

Seventy-nine type 1 diabetic children were recruited and categorized into four groups by HbA1c of 8% and DD of 4.5 years. HRV parameters as determined by separate frequency domain components (low frequency: LnLF, 0.04-0.15 Hz; high frequency: LnHF, 0.15-0.5 Hz; total power: LnTP, 0.04-0.5 Hz) were measured both at rest and during exercise. Pearson's correlation, one-way ANOVA, and multiple regressions with stepwise method were used for statistical analysis.

RESULTS

While at rest, HbA1c and DD were negatively correlated with all HRV parameters. Both HbA1c and DD were significant predictors in LnTP. However, only HbA1c was a significant predictor in LnLF and LnHF. Type 1 diabetes patients with HbA1c > 8% and DD > 4.5 years had a significantly lower HRV than the other patients. During exercise, HRV reduced significantly and no significant correlation between HbA1c and HRV or between DD and HRV was observed. Also, a significant difference in HRV among the four groups was not demonstrated. The smallest decrement in HRV from resting to exercise were in subjects with HbA1c > 8% and DD > 4.5 years.

CONCLUSION

HbA1c was a more dominant predictor for LnTP, LnHF and LnLF than DD in children with type 1 diabetes at rest. HRV reduced significantly from resting to exercise. However, the responses of HRV during exercise differ from the responses of HRV at rest.

Autonomic function testing in children and adolescents with diabetes mellitus

Cardiac autonomic neuropathy (CAN) is a common complication in type 1 diabetes mellitus (T1DM) and associated with an increased mortality. Early detection of CAN would be desirable for a better individual risk stratification. The aim of this study was to determine whether autonomic dysfunction can be diagnosed in young patients with a recent history of T1DM. Autonomic function was assessed in 20 pediatric patients with T1DM, aged 10-19 yr, and a control group of 136 non-diabetic patients using four cardiorespiratory reflexes: heart rate and blood pressure response in standing position, deep breathing, and Valsalva maneuver. Furthermore, power spectral analyses of the low- and high-frequency band of heart rate variability (HRV) and baroreflex sensitivity (BRS) were tested with the non-invasive Task force monitor (CNSystems, Graz, Austria). Cardiorespiratory reflexes were pathologic for at least one item in 75% of the diabetic and 60% in the healthy control group. A reduced BRS was always combined with abnormal HRV. We found this pattern in 30% of diabetic patients and never in the control group. In patients with impaired BRS, mean hemoglobin A1c (HbA1c) was 7.7% and duration of diabetes 6.5 yr. This did not differ from the overall value of the diabetic group: HbA1c level 8.4% and diabetes duration 7.3 yr. In conclusion, signs of autonomic dysfunction are not uncommon in an early stage of diabetes in young patients. Classical cardiorespiratory reflexes seem to be less specific than HRV and BRS as testing methods.

Coefficient of variation of R-R intervals in electrocardiogram is a sensitive marker of anemia induced by autonomic neuropathy in type 1 diabetes

The present study investigated the relationship between hemoglobin (Hb) levels and autonomic failure using a sensitive marker, coefficient of variation of R-R intervals in electrocardiogram (CVR-R) in order to clarify a cause of normocytic normochromic anemia in type 1 diabetic patients without overt nephropathy. We recruited 46 patients with type 1 diabetes and measured creatinine clearance (Ccr), HbA1c, albuminuria, Hb levels and CVR-R of all patients. In addition, the status of diabetic retinopathy and neuropathy were also evaluated. Serum erythropoietin (EPO), Fe, total iron binding capacity, lactate dehydrogenase, total bilirubin levels and number of reticulocytes and mean corpuscular volume were also measured to distinguish types of anemia. To survey the statistical correlation existing between Hb and body mass index (BMI), Ccr, HbA1c, albuminuria or retinopathy, multiple regression analysis was performed. Serum EPO, Fe, TIBC, LDH and TB levels and number of reticulocytes and MCV were within normal limits. Multiple regression analysis disclosed that HbA1c, nephropathy evaluated by albuminuria and Ccr, and retinopathy has no concern with Hb level. There is only significant relationship between Hb levels and CVR-R. Similar results were obtained even if we analyzed a group of male and female separately. We conclude that CVR-R has the strong relationship on anemia without overt nephropathy in type 1 diabetes, indicating that autonomic failure contributes on the progression of anemia via a poor response of EPO to anemia.

Heart rate variability and circadian variations in type 1 diabetes mellitus

Diabetic autonomic neuropathy (DAN) commonly complicates diabetes and is associated with increased mortality rates over 5 yr. This fact denotes the significance of DAN prevention, mainly with effective glycemic control. However, total prevention of autonomic neuropathy in diabetic patients is not achievable. Thus, the timely detection of DAN and the use of effective means to improve autonomic nervous system function or slow down its progression become of utmost significance. Heart rate variability (HRV) is a technique that measures the beat-to-beat variability in RR intervals, which reflects changes in autonomic activity and their impact on cardiovascular function. Circadian variation in time and frequency domains of heart variability has been shown to correlate with circadian rhythm of ambulatory ischemia and suggests that relative changes in vagal and sympathetic tone at different times during the day may have a direct relationship to the severity of clinical events. Forty-seven (21 boys and 26 girls) type I insulin-dependent diabetics and 46 control subjects (19 boys and 27 girls) were included in the study. Our investigation demonstrated that overall HRV is markedly depressed in diabetes mellitus (DM). All time domain parameters except standard deviation of all 5-min mean RR intervals and all frequency domain indices maintain significant circadian variation. These changes in overall HRV and HRV circadian rhythms reflect significant reductions in cardiac parasympathetic activity and, possibly, increased sympathetic tone.

[Reduction of endogenous regulation in internal medicine patients]

BACKGROUND

General health-related questionnaires on quality of life do not satisfactorily distinguish between healthy and sick people. One of the reasons cited for this lack is too much mental influence. This is why we developed a questionnaire on endogenous regulation (eR) that reflects the regulatory state of various vegetative functions.

OBJECTIVE

The current study examines whether the short version eR questionnaire is able to distinguish between healthy people and internal medicine patients.

PATIENTS AND METHODS

408 participants were included in the study (284 females, 124 males). Among these were patients with colorectal cancer (n = 49), breast cancer (n = 95), diabetes mellitus (type 1: n = 20, type 2: n = 40), coronary disease (n = 39), rheumatoid illnesses (n = 28) and multimorbid patients (n = 22) as well as a healthy control group (n = 115). In addition to the eR questionnaire the study also used the Hospital Anxiety and Depression Scale (HADS), the short questionnaire on self-regulation and questions on the vegetative status.

RESULTS

The healthy control group showed the highest eR, with an estimated average of M = 29.8. Patients with breast cancer, diabetes mellitus type 2, coronary disease and rheumatoid illnesses reveal a significantly lowered eR. Multimorbid patients show the lowest eR. Patients with cancer of the colon and diabetes type 1 were measured at M = 27.9 and M = 27.3 respectively and showed no significantly lowered estimated average compared to the control group. A high eR significantly correlates (p < 0.002) with the following parameters: low levels of anxiety (r = 49) and depression (r = 0.36), high self-regulation (r = 0.34), morning type (r = 0.40), less congestive perspiration (r = 0.38), less shivering (r = 0.23), dysmenorrhoea (r = 0.38) and allergies (r = 0.17).

CONCLUSION

Healthy people show the highest, multimorbid patients the lowest eR. Consistent relations to health, illness, heat regulation and personality presence have been shown. Further studies to clarify clinical relevance are necessary.

Cardiovascular endurance and heart rate variability in adolescents with type 1 or type 2 diabetes

BACKGROUND

Incidence rates of both type 1 and type 2 diabetes mellitus (DM) are increasing in youth and may eventually contribute to premature heart disease in early adulthood. This investigation explored the influence of type of diabetes, gender, body mass index (BMI), metabolic control (HbA1c), exercise beliefs and physical activity on cardiovascular endurance (CE), and heart rate variability (HRV). Differences in exercise beliefs, physical activity, HRV, and CE in youth with type 1 versus type 2 DM were determined.

METHODS

Adolescents with type 1 DM (n = 105) or with type 2 DM (n = 27) completed the Exercise Belief Instrument and the Physical Activity Recall. Twenty-four HRV measures were obtained via Holter monitoring and analyzed using SpaceLabs Vision Premier software system. The McMaster cycle test was used to measure CE (V0(2peak)).

RESULTS

Regardless of the type of DM, females and those with higher BMI, poorer metabolic control, and lower amounts of physical activity tended to have lower levels of CE. Exercise beliefs consistently predicted both frequency and time domain HRV measures. Measures of exercise beliefs, self-reported physical activity, CE (V0(2peak)), and HRV were significantly lower in adolescents with type 2 DM in comparison to those with type 1 DM.

CONCLUSIONS AND RECOMMENDATIONS

Early findings of poor physical fitness, lower HRV, fewer positive beliefs about exercise, and less active lifestyles highlight the importance of developing culturally sensitive interventions for assisting youth to make lifelong changes in their physical activity routines. Females, those with poorer metabolic control, and minority youth with type 2 DM may be particularly vulnerable to later cardiovascular disease.

Cardiovascular autonomic function in healthy adolescents

OBJECTIVE

The purpose of this study was to determine effects of age, sex, race, body mass index, and Tanner's stage on short-term evoked cardiovascular autonomic tests (ie, Valsalva ratio and change in heart rate with deep breathing) and 24-hour heart rate variability (HRV) in a sample of healthy adolescents, as well as to identify normative indices of both short-term evoked and 24-hour HRV in this age group.

DESIGN

A descriptive, correlational design was used.

SETTING

Study took place in a university hospital in a health science center located in the mid-South.

SUBJECTS

Participants included 75 healthy adolescents: mean age was 15.0 +/- 1.6 years, 14 were African American, 61 were white, 49 were girls, and 26 were boys.

OUTCOME MEASURES

Study measures included the Valsalva ratio, change in heart rate with deep breathing, and 24-hour HRV with power spectral analysis with Holter monitoring.

RESULTS

Major significant findings included lower values of 24-hour HRV measures for girls and African American adolescents (P <.05). Indices for normal ranges of both the short-term evoked and 24-hour HRV measures were computed with 95% confidence intervals.

CONCLUSIONS

Few published studies address cardiac autonomic function, including 24-hour HRV, in adolescents. Most studies reporting actual normative control values of HRV for youth typically have not addressed sex or racial differences. Our study included the largest number of adolescents to date in the reported literature and demonstrated the importance of considering sex and race variation in interpreting test results. The availability of state-of-the-art technology for obtaining HRV data allows for the early identification of subclinical cardiac autonomic changes in youth who have predispositions for cardiac complications, such as those with diabetes, congenital heart disease, or obesity.

Autonomic nervous system activity and the state and development of obesity in Japanese school children

OBJECTIVE

The autonomic nervous system (ANS) plays an important role in regulating energy expenditure and body fat content; however, the extent to which the ANS contributes to pediatric obesity remains inconclusive. The aim of this study was to evaluate whether sympathetic and/or the parasympathetic nerve activities were altered in an obese pediatric population. We further examined a physiological association between the duration of obesity and the sympatho-vagal activities to scrutinize the nature of ANS alteration as a possible etiologic factor of childhood obesity.

RESEARCH METHODS AND PROCEDURES

Forty-two obese and 42 non-obese healthy sedentary school children were carefully selected from 1080 participants initially recruited to this study. The two groups were matched in age, gender, and height. The clinical records of physical characteristics and development of the obese children were retrospectively reviewed to investigate the onset and progression of obesity. The ANS activities were assessed during a resting condition by means of heart rate variability power spectral analysis, which enables us to identify separate frequency components, i.e., total power (TP), low-frequency (LF) power, and high-frequency (HF) power. The spectral powers were then logarithmically transformed for statistical testing.

RESULTS

The obese children demonstrated a significantly lower TP (6.77 +/- 0.12 vs. 7.11 +/- 0.04 ln ms(2), p < 0.05), LF power (6.16 +/- 0.12 vs. 6.42 +/- 0.05 ln ms(2), p < 0.05), and HF power (5.84 +/- 0.15 vs. 6.34 +/- 0.07 ln ms(2), p < 0.01) compared with the non-obese children. A partial correlation analysis revealed that the LF and HF powers among 42 obese children were negatively associated with the duration of obesity independent of age (LF: partial r = -0.55, p < 0.001; HF: partial r = -0.40, p < 0.01). The obese children were further subdivided into two groups based on the length of their obesity. All three spectral powers were significantly reduced in the obese group with obesity of >3 years (n = 18) compared to the group with obesity of <3 years.

DISCUSSION

Our data indicate that obese children possess reduced sympathetic as well as parasympathetic nerve activities. Such autonomic depression, which is associated with the duration of obesity, could be a physiological factor promoting the state and development of obesity. These findings further imply that preventing and treating obesity beginning in the childhood years could be an urgent and crucial pediatric public health issue.

Cardiovascular autonomic reactivity is decreased in adolescents with Type 1 diabetes

AIMS

To characterize autonomic nervous system function by means of the heart rate and blood pressure responses to various stimuli in relation to pubertal maturation in patients with Type 1 diabetes mellitus (DM).

METHODS

One hundred out of 138 eligible patients at the Out-patient Diabetes Clinic and 100 healthy control subjects were examined in terms of cardiovascular parameters at rest, during deep breathing and when standing. Heart rate variability was analysed with time domain,frequency domain and fractal dimension parameters. Tanner pubertal staging was performed before the examinations.

RESULTS

The time domain parameters of heart rate variability at rest or during standing did not significantly differ between the patients and controls in total or at pubertal stages. In the spectral analysis of heart rate variability the very low frequency band was decreased in the patients during standing (P = 0.023).The increase in the very low frequency (P = 0.013)and low frequency (P = 0.031) spectral powers upon changing from a supine position to standing was attenuated in the patients in total, while no significant differences were observed within the Tanner pubertal stages between patients and controls. Heart rate variability during deep breathing was decreased in the patients with distal polyneuropathy (P = 0.006).

CONCLUSIONS

Although cardiovascular integrity is in the main well preserved in adolescent patients with Type 1 DM, these patients are prone to attenuated autonomic nervous system reactivity.

QTc interval prolongation and QTc dispersion in children and adolescents with type 1 diabetes

OBJECTIVES

To evaluate whether QT interval, QT interval corrected for heart rate (QTc), and QTc dispersion changes are already present in children and adolescents with diabetes.

STUDY DESIGN

QT interval, QTc, and QTc dispersion were measured on a 12-lead surface electrocardiogram in 60 children and adolescents with stable type 1 diabetes and in 63 sex- and age-matched control subjects. Differences were evaluated by using the Kolmogorov-Smirnov Z test. The number of patients with QTc > 440 ms was compared in the two groups. The possible influence of age, sex, diabetes duration, and glycosylated hemoglobin (HbA(1c)) was examined by using Spearman correlation analysis.

RESULTS

Diabetic children had significantly longer QTc intervals and a significantly larger QTc dispersion. The number of individuals with a QTc >440 ms was significantly higher in the diabetic group (14/60) than in the control group (2/63). The effect of age on R-R interval and QTc dispersion in healthy children was less pronounced in children with diabetes. HbA(1C) values did not significantly correlate with any of the parameters.

CONCLUSIONS

QTc prolongation and a larger QTc dispersion are already present in a significant proportion of children and adolescents with diabetes.

Evaluation of autonomic nervous system function with spectral analysis of heart rate variability in a case of tetanus

The autonomic nervous system is affected in a wide variety of neurological disorders. Its dysfunction may play an important role in the clinical course and may result in serious complications, such as cardiac arrest. We report a case of tetanus who presented with severe autonomic nervous system dysfunction which was detected by spectral analysis of heart rate variability monitored over 24 h. This is a semi-quantitative method for evaluation of the status of the autonomic nervous system. In the present case, the analysis revealed profoundly decreased activity of both sympathetic and parasympathetic nervous system modulation of cardiac rhythm. The parasympathetic nervous system activity was more severely impaired than that of the sympathetic nervous system. The relative predominance of the sympathetic nervous system in the present case may have resulted in unopposed sympathetic nervous system hyperactivity manifested in this patient by tachycardia and excessive sweating. We further infer that the documented diminished buffering capacity of the autonomic nervous system may have lead to a sudden cardiac arrest in our case. Thus, spectral analysis of heart rate variability is a non-invasive and sensitive method for evaluating the status of the autonomic nervous system of critically ill patients in the hospital setting.

The association of heart-rate variability with cardiovascular risk factors and coronary artery calcification: a study in type 1 diabetic patients and the general population

OBJECTIVE

To examine the association of heart-rate variability with cardiovascular risk factors and coronary calcification in type 1 diabetic and nondiabetic subjects without a history of cardiovascular disease. Reduced heart-rate variability is associated with increased risk of coronary events. Whether it is associated with coronary atherosclerosis is unknown.

RESEARCH DESIGN AND METHODS

Power spectral analysis was used to define heart-rate variability in a cross-sectional study of 160 type 1 diabetic patients and 163 randomly selected nondiabetic adults from the general population aged 30-55 years. Coronary artery calcification was measured using electron beam-computed tomography.

RESULTS

Reduced heart-rate variability was associated with similar risk factors in the diabetic and nondiabetic subjects, namely higher HbA(1c), triglycerides, systolic blood pressure, BMI, and albumin excretion rate. Reduced heart-rate variability was significantly associated with coronary artery calcification in all subjects (odds ratio per tertile lower total power = 1.5, P = 0.01). This association was not independent of blood pressure or BMI (odds ratio on adjustment = 1.3, P = 0.1).

CONCLUSIONS

Reduced heart-rate variability clusters with other cardiovascular disease risk factors, especially those that are more common in the insulin resistance syndrome, and is associated with increased coronary calcification in asymptomatic young adults. Whether reduced heart-rate variability leads to other risk factor disturbances or mediates the effects of other risk factors on atherosclerosis deserves further study.

Heart rate variability in adolescents and adults with type 1 diabetes

BACKGROUND

Limited data are available regarding the onset or trajectory of cardiovascular autonomic deterioration in persons with type 1 diabetes.

OBJECTIVE

To describe differences in heart rate variability among adolescents with type 1 diabetes, adults with type 1 diabetes who have coexisting renal failure, and adolescent and adult controls.

RESEARCH DESIGN AND METHODS

A correlational design was used to compare the status of heart rate variability in adults with type 1 diabetes and renal failure (n = 62); healthy adult controls (n = 67); adolescents with type 1 diabetes (n = 55); and healthy adolescent controls (n = 28). Convenience samples of adult patients with diabetes awaiting kidney or pancreas and kidney transplantation, and adolescents with diabetes were recruited from local university-based clinics. Volunteers served as healthy controls. The short-term R-R variability measures included in this study were changes in heart rate with deep breathing and with the Valsalva maneuver. Twenty-four hour ambulatory heart rate monitoring with power spectral analysis was also obtained to assess longterm R-R variability.

RESULTS

Adult patients with type 1 diabetes awaiting transplantation had significantly poorer heart rate variability measures than any of the other three populations studied (p < .0001). Adult control values also were significantly lower than either teenage controls or youths with diabetes (p < .05). Although most long-term R-R variability measures were lower in adolescents with diabetes versus controls, only one measure of parasympathetic modulation (i.e., pNN50) was significantly lower (p = .042). There were significant negative associations between HbA1c and sympathetic modulation (i.e., low hertz) in both the adult group (r= -.406, p = .029) and the adolescent group (r= -.324, p = .025) with diabetes.

CONCLUSIONS

Type 1 diabetes is associated with decreased heart rate variability, with the extent of the decrease related to the age of the individual and the severity of the disease.

Association of hyperglycemia with reduced heart rate variability (The Framingham Heart Study)

This study was designed to examine the association of heart rate variability (HRV) with blood glucose levels in a large community-based population. Previous reports have shown HRV to be reduced in diabetics, suggesting the presence of abnormalities in neural regulatory mechanisms. There is scant information about HRV across the spectrum of blood glucose levels in a population-based cohort. One thousand nine hundred nineteen men and women from the Framingham Offspring Study, who underwent ambulatory electrocardiographic recordings at a routine examination, were eligible. HRV variables included the SD of normal RR intervals (SDNN), high-frequency (HF, 0.15 to 0.40 Hz) and low-frequency (LF, 0.04 to 0.15 Hz) power, and LF/HF ratio. Fasting plasma glucose levels were used to classify subjects as normal (<110 mg/dl; n = 1, 779), as having impaired fasting glucose levels (110 to 125 mg/dl; n = 56), and as having diabetes mellitus (DM >/=126 mg/dl or receiving therapy; n = 84). SDNN, LF and HF power, and LF/HF ratio were inversely related to plasma glucose levels (p <0.0001). SDNN and LF and HF powers were reduced in DM subjects (4.28 +/- 0.03, 6.03 +/- 0. 08, and 4.95 +/- 0.09) and in subjects with impaired fasting glucose levels (4.37 +/- 0.04, 6.26 +/- 0.10, and 5.06 +/- 0.11) compared with those with normal fasting glucose (4.51 +/- 0.01, 6.77 +/- 0.02, and 5.55 +/- 0.02, all p <0.005), respectively. After adjusting for covariates (age, sex, heart rate, body mass index, antihypertensive and cardiac medications, systolic and diastolic blood pressures, smoking, and alcohol and coffee consumption), LF power and LF/HF ratio were lower in DM subjects than in those with normal fasting glucose (p <0.005). HRV is inversely associated with plasma glucose levels and is reduced in diabetics as well as in subjects with impaired fasting glucose levels. Additional research is needed to determine if low HRV contributes to the increased cardiovascular morbidity and mortality described in subjects with hyperglycemia.

Heart rate variability and cardiovascular tests in young patients with diabetes mellitus type 1

The aim of this study was to obtain information about parameters of heart rate variability (HRV) in three frequency bands (high frequency - HF, low frequency - LF and very low frequency - VLF), the sensitivity of cardiovascular tests, and subjective feelings depending on autonomic nervous system balance in a group of young patients with diabetes mellitus type 1 (IDDM). Sixty-four subjects were examined: 32 patients with diabetes with a mean age of 16.1 +/- 0.7 years and a mean duration of IDDM of 6.3 +/- 0.8 years, and 32 healthy controls matched for age, sex and BMI. Shorter R-R intervals and abnormal values reflecting HRV were found in the diabetic group. In particular, parameters of total power, and HF and LF bands were reduced. The ratio VLF/HF power revealed predominance of sympathetic tone in the diabetic subjects. Although relative power VLF was increased in the supine position, the reactive rise of the VLF band activity in orthostasis was lower in the IDDM group. Using cardiovascular tests (deep breathing, Valsalva, orthostasis), significant differences in reactions were found only in the deep breathing test. Evaluation of sympathetic:parasympathetic:indifferent subjective feelings by questionnaire did not reveal any differences between the diabetic and healthy groups.