Cardiovascular autonomic dysfunction in diabetes mellitus

Interplay Between Systemic Metabolic Cues and Autonomic Output: Connecting Cardiometabolic Function and Parasympathetic Circuits

There is consensus that the heart is innervated by both the parasympathetic and sympathetic nervous system. However, the role of the parasympathetic nervous system in controlling cardiac function has received significantly less attention than the sympathetic nervous system. New neuromodulatory strategies have renewed interest in the potential of parasympathetic (or vagal) motor output to treat cardiovascular disease and poor cardiac function. This renewed interest emphasizes a critical need to better understand how vagal motor output is generated and regulated. With clear clinical links between cardiovascular and metabolic diseases, addressing this gap in knowledge is undeniably critical to our understanding of the interaction between metabolic cues and vagal motor output, notwithstanding the classical role of the parasympathetic nervous system in regulating gastrointestinal function and energy homeostasis. For this reason, this review focuses on the central, vagal circuits involved in sensing metabolic state(s) and enacting vagal motor output to influence cardiac function. It will review our current understanding of brainstem vagal circuits and their unique position to integrate metabolic signaling into cardiac activity. This will include an overview of not only how metabolic cues alter vagal brainstem circuits, but also how vagal motor output might influence overall systemic concentrations of metabolic cues known to act on the cardiac tissue. Overall, this review proposes that the vagal brainstem circuits provide an integrative network capable of regulating and responding to metabolic cues to control cardiac function.

Diabetic neuropathy in children and youth: New and emerging risk factors

Pediatric neuropathy attributed to metabolic dysfunction is a well-known complication in children and youth with type 1 diabetes. Moreover, the rise of obesity and in particular of type 2 diabetes may cause an uptick in pediatric neuropathy incidence. However, despite the anticipated increase in neuropathy incidence, pathogenic insights and strategies to prevent or manage neuropathy in the setting of diabetes and obesity in children and youth remain unknown. Data from adult studies and available youth cohort studies are providing an initial understanding of potential diagnostic, management, and preventative measures in early life. This review discusses the current state of knowledge emanating from these efforts, with particular emphasis on the prevalence, clinical presentation, diagnostic approaches and considerations, and risk factors of neuropathy in type 1 and type 2 diabetes in children and youth. Also highlighted are current management strategies and recommendations for neuropathy in children and youth with diabetes. This knowledge, along with continued and sustained emphasis on identifying and eliminating modifiable risk factors, completing randomized controlled trials to assess effectiveness of strategies like weight loss and exercise, and enhancing awareness to support early detection and prevention, are pertinent to addressing the rising incidence of neuropathy associated with diabetes and obesity in children and youth.

Diabetes, and its treatment, as an effector of autonomic nervous system circuits and its functions

Diabetes increases the risk of cardiovascular complications, including heart failure, hypertension, and stroke. There is a strong involvement of autonomic dysfunction in individuals with diabetes that exhibit clinical manifestations of cardiovascular diseases (CVD). Still, the mechanisms by which diabetes and its treatments alter autonomic function and subsequently affect cardiovascular complications remain elusive. For this reason, understanding the brainstem circuits involved in sensing metabolic state(s) and enacting autonomic control of the cardiovascular system are important to develop more comprehensive therapies for individuals with diabetes at increased risk for CVD. We review how autonomic nervous system circuits change during these disease states and discuss their potential role in current pharmacotherapies that target diabetic states. Overall, this review proposes that the brainstem circuits provide an integrative sensorimotor network capable of responding to metabolic cues to regulate cardiovascular function and this network is modified by, and in turn affects, diabetes-induced CVD and its treatment.

Short-term metabolic control and sleep in children and adolescents with type 1 diabetes mellitus

AIMS

The aim of this study was to examine sleep in T1D children and in healthy controls by polysomnographic (PSG) examination and to determine the influence of short-term metabolic compensation on sleep quality and sleep disordered breathing (SDB).

METHODS

The prospective cross-sectional study included 44 T1D subjects and 60 healthy controls, aged 10-19 years. Subjects underwent anthropometric measurements, laboratory testing and standard overnight in-laboratory video polysomnography with continuous glucose monitoring (CGM).

RESULTS

No significant differences were found in total sleep time, sleep efficiency, percentage of sleep stages and respiratory parameters between T1D and healthy group. T1D children with more optimal short-term metabolic control (AvgSG < 10 mmol/l, n = 18) had a significantly lower apnea-hypopnea index (AHI) (0.3(0-0.5) vs. 0.6 (0.2-0.9) events/h, p < 0.05)and respiratory arousal index (0(0-0,1) vs. 0.2(0-0.3)), p < 0.01) compared to children with suboptimal short-term control(n = 26), no significant differences were found in parameters of sleep architecture. Obstructive sleep apnea (OSA) was diagnosed in only one T1D patient, nine T1D children had mild central apnea.

CONCLUSIONS

There may be an association between short-term metabolic compensation and SDB in T1D children without chronic complications, obesity or overweight and hypoglycemia. Further research is needed to confirm this result.

Pulmonary function tests in type 1 diabetes adolescents with diabetic cardiovascular autonomic neuropathy

Chronic diabetic complications may afflict all organ tissues including cardiovascular and respiratory system. The aim of the study was to establish if the presence of cardiovascular autonomic neuropathy (CAN) was associated with impaired pulmonary function tests in adolescents with type 1 diabetes (T1D). 46 adolescents with T1D and 25 healthy subjects at the age 15-19years were enrolled to the study. Basic anthropometric data, diabetes onset and duration, plasma glucose and A1c were established. Pulmonary function tests were measured by spirometry and the presence of CAN was examined by heart rate variability. Adolescents with T1D had significantly lower pulmonary function test parameters - FVC (p<0.01), FEV1 (p<0.01), MMEF (p<0.05) and PEFR (p<0.05) compared to the control subjects. In diabetic group, patients with CAN (CAN+, n=19) had significantly lower FVC (p<0.05), FEV1 (p<0.05) and PEFR (p<0.05) compared to patients without CAN (CAN-, n=27). All spirometric parameters were significantly lower in CAN+ subjects compared to healthy controls; however, no significant difference was found in these parameters between CAN- subjects and healthy controls. Spirometric parameters (FVC, FEV1) significantly positively correlated with diabetes onset and body mass index; and negatively correlated with diabetes duration and resting heart rate. Our results indicate that CAN may be associated with reduced pulmonary functions in adolescents with T1D.

Assessment of Peripheral Neuropathy Using Measurement of the Current Perception Threshold with the Neurometer® in patients with type 1 diabetes mellitus

OBJECTIVE

The aim of this study is to evaluate the role of current perception threshold (CPT) measurement in peripheral neuropathy in type 1 diabetic patients by using the Neurometer(®), a nerve measuring instrument.

METHODS

52 patients with type 1 diabetes mellitus with a disease duration of less than five years and normal neuropathy symptom score (NSS), neuropathy disability score (NDS) and sensory nerve conduction velocity (SCV), and 40 healthy controls were enrolled in this study. Measurement of CPT using the Neurometer(®) at 2000, 250 and 5 Hz assesses function in the bilateral median nerve and sural nerve in all studied cases. We also evaluated the glycated hemoglobin, microalbuminuria, urinary albumin/creatinine ratio and other metabolism indexes of all patients.

RESULTS

The CPT of the bilateral median nerve and sural nerve was significantly lower in diabetic patients (P<0.01). Moreover, the number of median nerve injuries in the diabetic group (left side 8/52, right side 8/52) is significantly different from the number of its ipsilateral sural nerve injuries (left side 28/52, right side 22/52) (left side P<0.01, right side P<0.01). By comparing those with DPN and those without DPN in the diabetic group, DPN groups had significantly higher glycated hemoglobin (t=2.518, P<0.05). Using binary logistic regression, high glycated hemoglobin was identified to be an independent risk factor of DPN incidence (OR (95% CI): 1.317 (1.013 -1.712), P<0.05).

CONCLUSION

These data suggest that CPT is useful in early detection of peripheral neuropathy in patients with type 1 diabetes mellitus. Patients with diabetic peripheral neuropathy, the lower limb nerve is more vulnerable than the upper limb nerve. In addition, patients with DPN had higher glycated hemoglobin which is an independent risk factor of DPN.

Evaluation of electrocardiographic parameters for early diagnosis of autonomic dysfunction in children and adolescents with type-1 diabetes mellitus

BACKGROUND

The aim of this study was to identify the sensitivity of electrocardiogram (ECG) in early diagnosis of cardiac autonomic function disorder in children with type 1 diabetes mellitus.

METHODS

A total of 150 children and adolescents with type 1 diabetes mellitus were enrolled between June 2009 and June 2010, as well as 100 age- and sex-matched healthy control children. Twelve-lead ECG was done in all cases and heart rate, QT and QTc interval, dispersion of P wave (Pd), and of QT (QTd) and QTc interval (QTcd) were measured. The clinical and demographic features such as age, gender, duration of follow up and level of HbA1c and fasting glucose were obtained and the effects of these parameters on ECG measurements were investigated.

RESULTS

The mean age of the patients and controls was 11.61 ± 3.72 years and 10.92 ± 3.2 years, respectively. QT and QTc interval and QTcd interval were significantly higher in diabetic children compared to healthy controls but these ECG findings were not associated with the duration of diabetes or glycemic state. Pd was significantly higher in the diabetic patients with HbA1c >7.5% compared to control, and this was also found in patients that were followed up >1 year.

CONCLUSIONS

Cardiac autonomic function disorder, which is one of the most important causes of morbidity and mortality, may emerge in the course of type 1 diabetes mellitus. It can be diagnosed on ECG even when the patients are asymptomatic.

Cardiovascular Risks in Adolescents With Diabetes From Vulnerable Populations

Limited data exist on the predisposition for an early trajectory of cardiovascular (CV) disease in adolescents with diabetes. We explored the effects of types of diabetes and sociodemographic factors (i.e., race, gender, income level, family structure) on the following CV risks: glucose control (A1c), blood pressure (BP), and lipid profile. Adolescents with type 1 DM (T1DM) or type 2 DM (T2DM) participated: 109 with T1DM and 42 with T2DM. The general linear model was used to examine the influence of type of DM, sociodemographic factors, and the interaction of type of DM and the sociodemographic factors on CV risks. Systolic and diastolic BP were increased in youth with T2DM versus T1DM. Non-Hispanic Blacks had a higher A1c and resting diastolic BP than non-Hispanic Whites. Lower income was also associated with higher resting diastolic BP. Males with T1DM had higher A1c, whereas females with T2DM had higher A1c. With low income, individuals with T1DM had higher A1c values than those with T2DM; those with high income and T2DM had higher A1c than those with T1DM. Adolescents with T1DM from single, divorced, or separated families had higher average A1c values. In comparison, those with T2DM from married families had higher A1c values. Triglycerides were increased for those with T2DM, with the greatest amount for Hispanics as compared with non-Hispanic Blacks. In summary, minority status, lower income, and family structure may have a greater impact on vulnerability for poor outcomes in adolescents with DM, regardless of the type of the disease.

Dispersion of the P wave as a test for cardiac autonomic function in diabetic children

OBJECTIVE

We aimed, in this study, to compare dispersion of the p wave in patients with type 1 diabetes to nondiabetic control subjects, and to investigate the relationship between the dispersion of the p wave and cardiac autonomic dysfunction in diabetic children.

METHODS

We enrolled 49 patients with type 1 diabetes, and 32 age- and sex-matched healthy subjects, measuring the Valsalva ratio, resting heart rate, and orthostatic hypotension in all. The duration of the p wave was measured manually on a high-resolution computer screen. Dispersion, defined as the difference between maximum and minimum durations of the p waves, was also measured in the 12-lead electrocardiogram before and after the Valsalva maneuver.

RESULTS

The mean age of the patients and their controls were 14.2 +/- 4.8 years, and 12.7 +/- 4.5 years, respectively. The mean duration of diabetes had been 6.2 +/- 4.6 years. Maximal and minimal values for the duration of the p wave were significantly decreased in the diabetic children, with the dispersion itself significantly increased. Values for the dispersion in the diabetic subjects were similar before and after the Valsalva maneuver, whereas dispersion was found significantly increased after this maneuver in the controls. The differences in the Valsalva ratio, resting heart rate, and orthostatic hypotension between the groups, on the other hand, were not found to be statistically significant.

CONCLUSION

The noted increase in the dispersion of the p wave in diabetic children reveals the onset of cardiac electrophysiological heterogeneity before it is possible to detect parasympathetic and sympathetic dysfunction with other tests.

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.

Non-invasive assessment of cardioregulatory autonomic functions in children with epilepsy

OBJECTIVES

We aimed to evaluate the interictal cardiovascular autonomic functions in pediatric patients with idiopathic epilepsy, both partial and generalized.

MATERIALS AND METHODS

The study included 25 patients with idiopathic epilepsy and 50 control subjects. Patients underwent five standardized clinical cardiovascular reflex autonomic tests [resting heart rate (HR), HR response to deep breathing and to Valsalva maneuver, the 30:15 ratio of HR response to standing, and blood pressure response to standing], as well as a 12 lead surface electrocardiogram. Heart rate variability (HRV) was tested via 24-h Holter monitoring and the time domain parameters (SDNN, PNN50, rMSDD) were assessed. Excretion of vanillyl mandelic acid and metanephrine was measured in 24-h urine collection.

RESULTS

Clinical reflex autonomic tests showed mild dysfunction in 8%, moderate dysfunction in 44% and severe dysfunction in 4% of patients. The HRV parameter, SDNN, was reduced in all age groups, while rMSDD and PNN50 were reduced only in the older age group. Metanephrine levels were significantly reduced in the patients group. Patients with uncontrolled epilepsy had a significantly higher frequency of autonomic dysfunction as assessed by clinical scoring.

CONCLUSION

Cardiac autonomic dysfunction is not uncommon in pediatric patients with epilepsy. Altered cardiovascular regulation seems to be related to the epilepsy itself rather than to the characteristics of the disorder.

Urinary flow disturbance as an early sign of autonomic neuropathy in diabetic children and adolescents

AIMS

Urinary bladder dysfunction is a frequent complication of diabetes mellitus in adults. The aim of this study is to determine the early disturbances of the detrusor contractility in children, and adolescents with type 1 diabetes.

MATERIALS AND METHODS

The bladder urine flow parameters were investigated in 37 children with type 1 diabetes, 10/37 with cardiovascular autonomic dysfunction (CAD) voided 482 +/- 128 mils (Group A), 27/37 without CAD voided 258 +/- 52 mils (Group B). From an earlier uroflow screening study 20 healthy children formed group control A, who had voided 488 +/- 94 mils, and another 30 healthy children formed group control B, who had voided 260 +/- 50 mils. The compared groups were matched for voided volume, age, weight, and height. There was no evidence of urinary tract abnormalities in any of the children.

RESULTS

Time to maximum flow was longer in both diabetic groups as compared with controls (P < 0.01), and the acceleration (the ratio of maximum flow and the time to maximum flow) of diabetics was significantly lower (P < 0.01). Bladder emptying was complete in each subject. Bladder wall disturbances were not seen by ultrasound.

CONCLUSIONS

The decreased acceleration of detrusor muscle contraction may be interpreted as an early sign of autonomic neuropathy in children and adolescent with type 1 diabetes, even in patients without CAD. Clinicians may be able to determine autonomic neuropathy by using uroflowmetry that is easy to perform, sensitive, reproducible, and needs only a child's minimal cooperation.

Association of angiotensin-converting enzyme DD genotype with 24-h blood pressure abnormalities in normoalbuminuric children and adolescents with Type 1 diabetes

AIMS

To assess the distribution of the insertion/deletion (I/D) polymorphism of the angiotensin-converting enzyme (ACE) gene in children and adolescents with Type 1 diabetes and to evaluate the association between ACE genotype and blood pressure (BP).

METHODS

ACE genotypes were assessed in 124 normoalbuminuric, clinically normotensive Type 1 diabetic children and adolescents and 120 non-diabetic controls using polymerase chain reaction. Twenty-four-hour ambulatory BP monitoring was undertaken in all patients.

RESULTS

ACE genotypes distributed in patients as follows: 34 (27%) DD, 57 (46%) ID, 33 (27%) II. The distribution was similar in the control group: DD in 28% (33), ID in 45% (54), and II in 27% (33). Patients with DD genotype had higher mean 24-h diastolic BP (73.8 +/- 6.2 vs. 70.2 +/- 5.0 and 69.7 +/- 6.3 mmHg; P = 0.005) and lower diurnal variation in BP (11.8 +/- 4.6 vs. 14.2 +/- 4.2 and 14.8 +/- 4.3%; P = 0.011) compared with ID and II groups. Four patients in the DD group proved to be non-dipper compared with one in the ID and none in the II group (P = 0.026). Twenty-four-hour diastolic blood pressure was independently predictive for AER as dependent variable in the DD genotype patient group (r(2) = 0.12, P = 0.03).

CONCLUSIONS

Children and adolescents with Type 1 diabetes do not differ from the non-diabetic population regarding the I/D polymorphism of the ACE gene. ACE gene polymorphism is associated with BP abnormalities in normotensive and normoalbuminuric children and adolescents with Type 1 diabetes.

Heart rate variability in young patients with diabetes mellitus and healthy subjects explored by Poincaré and sequence plots

Autonomic neuropathy is a common complication of the diabetes mellitus (DM). The significance of its early diagnosis is very high because the mortality of the patients with this complication is elevated. Considering the effort to apply new mathematical methods to cardiac dysregulation diagnosis, the major aim of the study was to ascertain which of the new heart rate variability (HRV) parameters are different in young patients with DM type 1 compared with control group. The next aim was to assess the HRV changes during prolonged (40 min) supine rest. The heart rate was continuously recorded during supine rest in 17 young patients with DM type 1 (10 women, 7 men) aged 22.4 +/- 1.0 years (mean +/- SEM). The control group consisted of 17 healthy matched probands. The HRV (time/frequency domains, Poincare and sequence plots, sample entropy) was analysed in two intervals - T1 starting at fifth minute and T2 starting at 30th minute of supine rest. The major results of our study are: the reduced Poincare plot pattern measures in the young DM group; the lower percentage of points in the third quadrant of sequence plot (this parameter was not correlated with the mean heart rate) and significant changes in HRV during supine rest in DM group (in contrast to control subjects). In conclusion, HRV parameters based on nonlinear dynamics were able to distinguish cardiac dysregulation in young patients with DM from the control group. The percentage of points in the third quadrant of sequence plot provides information that is not dependent on mean heart rate. Poincare and sequence plots, together with the rate of HRV changes during supine rest, can provide clinically relevant information usable in diagnosis of the cardiac dysregulation.

Autonomic dysfunction in uremia assessed by heart rate variability

Decreased heart rate variability is an independent risk factor for cardiac mortality in hemodialysis patients. Our aim was to determine whether it is already present in uremic children and young adults on hemodialysis and following renal transplantation. Twenty-two hemodialysis patients [age 17.2 years (median, quartiles 13.0-22.6)], 22 transplant patients [18.4 years (14.4-21.2)], and 29 healthy controls [16.4 years (15.7-21.1)] were examined. Heart rate and its high (HF) and low (LF) frequency variability were measured in the supine position for 10 min. High and low frequency variability was significantly reduced, whereas heart rate and LF/HF ratio was significantly elevated in both patient groups compared with controls. There was a clear-cut difference between the dialyzed and the transplanted groups based on the HF variability, with the lowest values in the dialysis group ( P<0.01). LF and LF/HF data did not allow us to distinguish between the patient groups. In conclusion, heart rate variability in the HF range is a sensitive tool for detecting cardiovascular autonomic dysfunction that is already present in children and adolescents with impaired kidney function.

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.

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.

Ambulatory blood pressure monitoring (ABPM) in normotensive adolescents with type 1 diabetes

OBJECTIVE

To evaluate 24-h ambulatory blood pressure monitoring (ABPM) for early detection of hypertension in adolescents with type 1 diabetes mellitus (DM1).

DESIGN

Patients underwent fundoscopy, albuminuria determinations, two repeated autonomic cardiovascular tests, heart rate (HR) variation during deep breathing and blood pressure (BP) variation during sustained handgrip. Twenty-four hour BP measurements were taken automatically by an oscillometric portable monitor.

SETTING

A specialty pediatric diabetes clinic and subjects' homes.

PARTICIPANTS

Eighteen children aged 10-17 yr with 2+ yr of DM1, without long-term complications, and 34 controls.

RESULTS

Higher ambulatory HR during the day than at night did not differ between DM1 subjects and controls. Mean systolic (s) and diastolic (d) BP in patients during the daytime were not significantly different from the control values. During the night, both sBP and dBP mean values in patients differed from those of controls. Statistical analysis of day and night HR and BP measurements were not different in both groups. The percentage decrease during the night in sBP and dBP was significantly smaller in patients than in controls. There were no differences by gender or duration of diabetes > or < 5 yr or by HbA1 above and below 10%. No difference in nocturnal sBP or dBP decline was observed between patients with or without abnormal autonomic test results.

CONCLUSION

ABPM is more reliable than casual BP measurement in detecting early BP alterations during the night, before the appearance of microalbuminuria, in young patients with DM1.

Complications of pediatric and adolescent type 1 diabetes mellitus

Type 1 diabetes mellitus is potentially associated with serious microvascular and macrovascular complications, although these are usually subclinical during the pediatric and adolescent years. There is no "grace" period for the beginnings of such complications. Duration of diabetes, glycemic control, age, and pubertal stage are critical factors contributing toward development of such problems. Other risk factors include family history (genetic predisposition), hyperlipidemia, hypertension, and smoking. The Diabetes Control and Complications Trial (DCCT) proved the importance of glycemic control and emphasized the ability of improved glucose control to prevent or decrease retinopathy, nephropathy, and neuropathy using a multidisciplinary same-philosophy-of-care approach plus targeted glucose and hemoglobin A(1c) values. Other natural history and intervention studies support the findings of the DCCT. Although our current tools are not perfect, they allow us to decrease microangiopathic complications very significantly if we educate our patients and their family members. Metabolic control counts.

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.

Autonomic nerve function in adolescents with Type 1 diabetes mellitus: relationship to microalbuminuria

AIMS

Thirty adolescent patients with Type 1 diabetes mellitus and microalbuminuria were studied for evidence of early autonomic neuropathy.

METHODS

Using tests involving cardiovascular and pupillary reflexes, the adolescents were compared with a normoalbuminuric group of patients with diabetes, who were matched for age, sex, puberty and duration of diabetes.

RESULTS

There was an increased prevalence of autonomic nerve dysfunction in the patients with microalbuminuria. These patients had higher resting heart rates (86 beats/min in the microalbuminuric group vs. 77 beats/min in normoalbuminuric controls, P = 0.002), and impaired pupillary dilatation in darkness (pupillary diameter % 56.5% vs. 62.5%, P = 0.003). Patients with microalbuminuria also had poorer long term glycaemic control (mean HbA1C 8.7% vs. 7.8%, P = 0.002) and higher blood pressures (systolic 125 vs. 116 mmHg, P = 0.001; diastolic 69 vs. 62 mmHg, P = 0.0001; mean arterial pressure 90 vs. 83 mmHg, P = 0.002) than those with normal urinary albumin excretion.

CONCLUSIONS

Microalbuminuria and autonomic nerve dysfunction co-exist in patients with Type 1 DM. Longitudinal studies will determine whether these findings have implications for the identification of patients at higher risk of progression of early renal complications.

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.