Eighteen years of fair glycemic control preserves cardiac autonomic function in type 1 diabetes

Prevalence and Correlates of Cardiovascular Autonomic Neuropathy Among Patients with Diabetes in Uganda: A Hospital-Based Cross-sectional Study

Background:

Cardiovascular autonomic neuropathy (CAN) is a common complication in individuals with diabetes mellitus (DM) but often overlooked in clinical practice. The burden and correlates of CAN have not been extensively studied in low-income countries, particularly in sub-Saharan Africa.

Objectives:

To determine the prevalence and correlates of CAN among adults in ambulatory diabetes care in southwestern Uganda.

Method:

We conducted a cross-sectional study among adults with diabetes from November 2018 to April 2019. CAN was assessed using the five autonomic function tests: deep breathing, Valsalva maneuver, postural index on standing, change in blood pressure during standing and diastolic blood pressure response to isometric exercise. We estimated the prevalence of CAN and fit regression models to identify its demographic and clinical correlates.

Results:

We enrolled 299 individuals. The mean age was 50.1 years (SD ± 9.8), mean HbA1c was 9.7 (SD ± 2.6) and 69.6% were female. CAN was detected in 156/299 (52.2%) of the participants on the basis of one or more abnormal cardiovascular autonomic reflex tests. Out of 299 participants, 88 (29.4%) were classified as early CAN while 61/299 (20.4%) and 7/299 (2.3%) were classified as definite and severe (advanced) CAN respectively. In multivariable regression models, age over 50 years (aOR 3.48, 95%CI 1.35 –8.99, p = 0.010), duration of diabetes over 10 years (aOR 4.09, 95%CI 1.78 –9.38, p = 0.001), and presence of diabetic retinopathy (aOR 2.25, 95%CI 1.16 –4.34, p = 0.016) were correlated with CAN.

Conclusions:

Our findings reveal a high prevalence of CAN among individuals in routine outpatient care for diabetes mellitus in Uganda. Older age, longer duration of diabetes and coexistence of retinopathy are associated with CAN. Future work should explore the clinical significance and long term outcomes associated with CAN in this region.

Cardiovascular autonomic neuropathy in adolescents and young adults with type 1 and type 2 diabetes: The SEARCH for Diabetes in Youth Cohort Study

OBJECTIVE

To estimate the prevalence of and risk factors for cardiovascular autonomic neuropathy (CAN) in adolescents and young adults with type 1 and type 2 diabetes enrolled in the SEARCH for Diabetes in Youth Study.

METHODS

The study included 1646 subjects with type 1 diabetes (age 18 ± 4 years, diabetes duration 8 ± 2 years, HbA1c 9.1 ± 1.9%, 76% non-Hispanic Whites) and 252 with type 2 diabetes (age 22 ± 4 years, diabetes duration 8 ± 2 years, HbA1c 9.2 ± 3.0%, 45% non-Hispanic Blacks). Cross-sectional and longitudinal risk factors were assessed at baseline and follow-up visits. Area under the curve (AUC) was used to assess the longitudinal glycemic exposure and cardiovascular risk factors. CAN was assessed by time and frequency domain indices of heart rate variability (HRV). CAN was defined as the presence of ≥3 of 5 abnormal HRV indices.

RESULTS

The prevalence of CAN was 12% in adolescents and young adults with type 1 diabetes and 17% in those with type 2 diabetes. Poor long-term glycemic control (AUC HbA1c), high blood pressure, and elevated triglyceride levels were correlates of CAN in subjects with type 1 diabetes. In those with type 2 diabetes, CAN was associated with elevated triglycerides and increased urinary albumin excretion.

CONCLUSIONS

The prevalence of CAN in this multiethnic cohort of adolescents and young adults with type 1 and type 2 diabetes are comparable to those reported in adults with diabetes. Suboptimal glycemic control and elevated triglycerides were the modifiable risk factors associated with CAN.

Impact of glycemic control on heart rate variability in youth with type 1 diabetes: the SEARCH CVD study

AIM

This study explored the role of glycemic control on cardiac autonomic function, measured by heart rate variability (HRV), in youth with type 1 diabetes.

PATIENTS AND METHODS

A retrospective cohort of 345 youth with type 1 diabetes (mean age, 18.5 years; duration, 10 years) participating in the SEARCH for Diabetes in Youth study were enrolled in the ancillary SEARCH Cardiovascular Disease (CVD) study. Anthropometric, metabolic, and HRV parameters were collected at the current research visit. Glycemic control over time was assessed by the mean glycated hemoglobin (A1c) levels collected over the past 6 years. Multiple linear regression analysis assessed the association between A1c over time and HRV parameters, independent of demographic and CVD risk factors. Participants were categorized into four glycemic control categories based on their mean A1c over time: Group 1, optimal (mean A1c, ≤7.4%); Group 2 (mean A1c, 7.5-8.4%); Group 3 (mean A1c, 8.5-9.4%), and Group 4, poor (mean A1c, ≥9.5%), and a linear trend was explored across these categories.

RESULTS

For every 1% increase in the average A1c over 6 years there was a 5% decrease in the SD of the normal RR interval (SDNN) (P=0.02) and 7% decrease in the root mean square successive difference of the RR interval (RMSSD) (P=0.02), independent of demographic and traditional CVD risk factors. A dose-response relationship between worsening glucose control categories and measures of overall reduced HRV was found.

CONCLUSIONS

Chronic hyperglycemia is the main determinant of early cardiac autonomic dysfunction, manifested as reduced overall HRV and parasympathetic loss, among youth with type 1 diabetes.

Short-term oxygen administration restores blunted baroreflex sensitivity in patients with type 1 diabetes

AIMS/HYPOTHESIS

We hypothesised that the blunted baroreflex sensitivity (BRS) typical of type 1 diabetes is caused by a higher degree of tissue hypoxia in diabetes, and tested whether oxygen increased BRS and ventilation less, equally or more than in healthy control participants (the latter suggesting higher tissue hypoxia). In addition, we also considered the possible interference between oxygen and breathing pattern.

METHODS

In 96 participants with type 1 diabetes and 40 age-matched healthy controls, we measured BRS (average of six different standard methods), oxygen saturation, end-tidal carbon dioxide and ventilation changes during spontaneous and controlled breathing at 15 and six breaths/min, in normoxia and during 5 l/min oxygen administration.

RESULTS

BRS was blunted and blood pressure higher in diabetic participants during spontaneous breathing (p < 0.05). BRS increased with oxygen during spontaneous breathing in diabetic (p < 0.001) but not in control participants, and with oxygen the difference in BRS was no longer significant. Slow breathing in normoxia restored BRS to a similar extent to giving oxygen. Oxygen increased systolic and diastolic blood pressure, RR interval, heart rate variability, minute ventilation and tidal volume to a greater extent in diabetic patients than in controls, and decreased carbon dioxide similarly to controls.

CONCLUSIONS/INTERPRETATION

The increased response to hyperoxia suggests a pre-existing condition of tissue hypoxia that functionally restrains parasympathetic activity in patients with type 1 diabetes. Autonomic abnormalities can be partially and temporarily reversed by functional manoeuvres such as slow breathing or oxygen administration through enhancement of parasympathetic activity and/or correction of tissue hypoxia.

Deep breathing improves blunted baroreflex sensitivity even after 30 years of type 1 diabetes

AIMS/HYPOTHESES

Cardiovascular autonomic neuropathy is associated with increased morbidity in patients with type 1 diabetes. Although it is conventionally considered to be an organic, irreversible disorder, we previously demonstrated in patients with short-duration type 1 diabetes that reduced baroreflex sensitivity (BRS) could be corrected by slow, deep breathing, indicating a functional component to the disorder. We have now tested whether autonomic abnormalities in long-term diabetes progress to a stage that cannot be modified by functional manoeuvres, indicating a switch towards predominantly organic dysfunction.

METHODS

We studied 117 patients with a short duration (8.9 ± 0.1 years) and 37 patients with a long duration (33.7 ± 0.5 years) of type 1 diabetes, 73 healthy controls and 12 heart-transplanted participants (surgical heart denervation). An autonomic score was calculated from autonomic function tests. Spectral analysis of heart rate and blood pressure variability, and BRS, were obtained from recordings during normal (15 breaths per min) and slow, deep (six breaths per min) controlled breathing.

RESULTS

BRS was reduced in all patients, but more in patients with a long duration of diabetes or with increasing autonomic involvement, although the effect of duration disappeared after adjustment for age. Slow breathing increased the BRS to the level of the control participants at a normal rate of breathing (15 per min) in all patients except those with an abnormal autonomic score.

CONCLUSIONS/INTERPRETATION

Patients with type 1 diabetes have a blunted BRS that in the majority of patients can be restored by slow breathing, irrespective of disease duration. Even after a long duration of diabetes, the abnormal BRS is at least in part of functional origin.

Type 1 diabetes, hyperglycaemia, and the heart

Type 1 diabetes is associated with a substantially increased risk of cardiovascular disease that might not always be appreciated in view of the fairly young age of patients with this condition. In fact, in type 1 diabetes, the heart is subject to a variety of pathological insults, including accelerated atherosclerosis, cardiac autonomic neuropathy, and possibly intrinsic cardiomyopathy. Although the relation between hyperglycaemia and microvascular complications has been well established, a direct effect of hyperglycaemia on cardiovascular disease in type 1 diabetes has long been debated. More recently, several studies, most notably the Diabetes Control and Complications Trial/Epidemiology of Diabetes Interventions and Complications, have clarified this issue and provided conclusive evidence that hyperglycaemia is indeed a mediator of cardiovascular risk in type 1 diabetes and that intensive diabetes therapy can reduce cardiovascular disease outcomes. We review current concepts in type 1 diabetes and the heart, focusing on recent insights into the central role of hyperglycaemia.

Neuropatia autonômica: uma complicação de alto risco no diabetes melito tipo 1

O acometimento patológico do sistema nervoso no diabetes melito é muito amplo e, freqüentemente, bastante grave. A prevalência de neuropatia diabética atinge níveis elevados com a evolução temporal do diabetes, chegando, geralmente, a freqüências acima de 50% de lesão neurológica em diferentes grupos de pacientes analisados em nosso meio e no exterior. A lesão neurológica nesta situação patológica é extensa no organismo humano diabético, envolvendo amplamente todo o sistema nervoso periférico nos seus componentes sensitivo-motor e autonômico: com clínica característica e concordante com as hipóteses patogênicas de natureza metabólica e/ou microvascular. O sistema nervoso autonômico é o elemento fundamental na regulação da função da maior parte dos sistemas ou órgãos no organismo, portanto, a sua lesão pode trazer importantes alterações para as funções cardiovascular, respiratória, digestiva, urinária e genital, podendo influir na função vital de alguns desses órgãos ou sistemas. Este artigo aborda as alterações decorrentes da lesão do sistema nervoso autonômico, especialmente nos pacientes diabéticos tipo 1, procurando dimensionar o risco de morbimortalidade.

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.

Impaired postexercise cardiovascular autonomic modulation in middle-aged women with type 2 diabetes

BACKGROUND

Type 2 diabetes is associated with cardiovascular autonomic dysfunction. Postexercise autonomic modulation may be different in obese individuals with and without type 2 diabetes. We examined postexercise responses in nondiabetic and diabetic women aged 40-60 years.

METHODS

Hemodynamics, high-frequency and low-frequency of RR interval, low-frequency of systolic blood pressure variability and baroreflex sensitivity were evaluated before and after a 20 min walk at approximately 65% of VO2 peak in eight lean, 12 obese without type 2 diabetes and eight women with type 2 diabetes. Postexercise measurements were obtained at 10-15, 20-25 and 30-35 min.

RESULTS

Systolic blood pressure decreased at 10 (P<0.001) and 20 min (P<0.01) in all groups. Total peripheral resistance decreased at 10 min in all women, but the subsequent increase at 20 min was greater (P<0.01) in lean than in diabetic women. Log-transformed low-frequency of systolic blood pressure increased (P<0.01) at 10 and 20 min in all women, but the increase at 10 min was smaller (P<0.05) in diabetic than in lean women. Heart rate was increased (P<0.001) at 10 min in all women and at 20 min in both obese groups. Both log-transformed high-frequency of RR interval and baroreflex sensitivity decreased at 10 and 20 min of recovery in all groups. A group-by-time interaction (P<0.05) was observed for heart rate and baroreflex sensitivity as a lower heart rate and higher baroreflex sensitivity were observed in lean women than in women with type 2 diabetes.

CONCLUSIONS

Reduced postexercise baroreflex sensitivity and responses to autonomic cardiovascular activity contribute to an attenuated recovery of heart rate and total peripheral resistance after brisk walking in middle-aged obese women with type 2 diabetes.

Left Ventricular Mass Reduction in Type 1 Diabetic Patients With Nephropathy

Left ventricular hypertrophy regression was postulated more likely to occur in diabetic patients when renal function was preserved. Seventeen type 1 diabetic patients followed for 12 months while receiving protocol-driven glycemic and blood pressure control had baseline and 12-month echocardiography. Despite identical treatment resulting in similar blood pressures, patients with better renal function (below the group mean, serum creatinine < or =1.7 mg/dL) demonstrated reduction in left ventricular mass and septal thickness as well as increase in left ventricular fractional fiber shortening not observed in those with worse renal function (above the group mean, serum creatinine >1.7 mg/dL). This latter group also did not experience the improvement in glycemic control observed in those with better renal function. Regression of left ventricular mass and functional improvement can be accomplished with improved glycemic control. In the presence of renal dysfunction, however, efforts to control glycemia and cardiac work are suboptimal. Aggressive glycemic and blood pressure targets to reduce cardiovascular morbidity in this high-risk population should be studied.

Incipient cardiovascular autonomic imbalance revealed by wavelet analysis of heart rate variability in Type 2 diabetic patients

AIM

Incipient cardiovascular autonomic imbalance is not readily diagnosed by conventional methods. Spectral analysis of heart rate variability (HRV) by wavelet transform (WT) was used to measure cardiovascular autonomic function in patients with Type 2 diabetes.

METHODS

Thirty-two diabetic patients without (D), 26 with cardiovascular autonomic neuropathy (DAN) and 72 control subjects (C) participated. A 30-min HRV time series was analysed by wavelet transformation and four characteristic frequency intervals were defined: I (0.0095-0.021 Hz), II (0.021-0.052 Hz), III (0.052-0.145 Hz) and IV (0.145-0.6 Hz).

RESULTS

When compared with C, in both D and DAN the normalized power and amplitude of interval II were increased and of interval IV decreased, resulting in a significantly higher II/IV ratio. Furthermore, in DAN the normalized power and amplitude of interval I were increased and of interval III decreased when compared with the D and C groups. The diabetic patients were divided in two equal subgroups according to HbA(1c) < 8.0% and >or= 8.0%. In the subgroup with HbA(1c) >or= 8.0%, normalized power in interval II was significantly higher and in interval IV significantly lower than in the subgroup with HbA(1c) < 8.0%. In D, but not in DAN patients prescribed ACE inhibitors, the absolute amplitude and power of oscillations were significantly higher than in patients not taking ACE inhibitor therapy.

CONCLUSIONS

Patients with diabetes have increased sympathetic and decreased parasympathetic cardiac activity regardless of the presence of autonomic neuropathy. Glycaemic control and treatment with ACE inhibitors may favourably influence HRV in diabetic patients without autonomic neuropathy.

Efeitos fisiológicos do treinamento físico em pacientes portadores de diabetes tipo 1

Insulinoterapia, atividade física regular e planejamento alimentar, em conjunto, consistem na abordagem mais completa no tratamento de portadores de diabetes mellitus tipo 1 (DM1). Estudos clínicos e experimentais têm evidenciado os benefícios do treinamento físico em indivíduos com DM1, tais como melhora na sensibilidade à insulina, redução das doses de insulina e atenuação das disfunções autonômicas e cardiovasculares. Essa revisão aborda as adaptações fisiológicas ao treinamento físico no indivíduo com DM1 e discute as recomendações e prescrição de atividade física para esta população.

Total power and high frequency components of heart rate variability and risk factors for atherosclerosis

INTRODUCTION

Low heart rate variability, HRV, is associated with diabetic neuropathy and with ischemic heart disease, IHD. The time context points to diabetes preceding changes in HRV, while changes in HRV precede the development of atherosclerosis and IHD. The purpose of the study was to analyse the association between the physiological risk factors of IHD and HRV in a prospective design.

METHODS

In 1998 and 2002, data was gathered in a study concerning the risk factors for atherosclerosis. From among the participants it was possible to include 50 women and 24 men in a sub-study concerning HRV. Heart rate variability was measured partly during a clinical examination with exposure to a simple stress test, and partly during the first 4 h of sleep. The clinical examination, which lasted 45 min, resulted in 9, 5-minute HRV measurements, while the sleep period was divided into 2 periods of 2 h each, for which average HRV measurements were calculated. The associations between HRV and risk factors for IHD were analysed using the GLM, repeated measures method. As the dependent variables in the GLM analyses 11 levels (9 while awake and 2 while sleeping) of total power and high frequency variability, respectively, were used. The included risk factors were; body mass index, waist-hip ratio, systolic blood pressure, fibrinogen, cholesterol, HDL-cholesterol, HbA1c, testosterone, DHEAs, cortisol and catecholamines. Catecholamines were measured in urine and only in 1998. Cortisol was measured in both urine and saliva in 1998, but only in saliva in 2002. The results were adjusted according to the starting time of the measurements.

RESULTS

Among the women, waist-hip ratio and HbA1c were significantly and negatively associated with both TP and HF. Stress hormones were not associated with HRV. Among the men, waist-hip ratio, HbA1c, and fibrinogen in 2002, and cortisol and noradrenaline in 1998 were significantly and negatively associated with TP and HF.

CONCLUSION

The study showed gender differences in the observed associations. In both gender, waist ratio and HbA1c were negatively associated with TP and HF. Furthermore, in the men, but not in the women, stress hormones in 1998, i.e. cortisol and noradrenaline, was negatively associated with TP and HF. The presented data give rise to discussion of the pathophysiology behind heart rate variability and ischemic heart disease, which may be different between women and men.

Regression of Left Ventricular Hypertrophy in Diabetic Nephropathy: Loss of Parasympathetic Function Predicts Response to Treatment

Both left ventricular (LV) hypertrophy and decreased autonomic function are predictors of adverse cardiac events. Patients with diabetic nephropathy have an excess cardiovascular risk. The authors determined heart rate variability from 24-hour ambulatory electrocardiographic recordings and measures of LV mass with systolic and diastolic function from echocardiograms. Patients with diabetic nephropathy (n=16) were seen weekly for insulin and hypertension management. Glycohemoglobin decreased from 9.5+/-0.4% to 8.3+/-0.4% (p=0.01), and advanced glycated end products decreased from 12.1+/-2.2 to 7.4+/-1.2 units (p=0.03). Mean arterial pressure and body weight did not change. Serum creatinine increased (1.8+/-0.1 mg/dL to 2.0+/-0.2 mg/dL; p=0.03). The authors used a panel of markers of baseline heart rate variation to assess autonomic function. When covariance of the heart rate interval results were evaluated, the group below the median was found to have a significant decrease in LV mass, from 230 g to 184 g (p=0.013); the group above the median had an increase (182 g to 193 g; p=0.5329). Baseline covariance of the heart rate interval predicted 12-month changes in LV mass in 13 of 16 patients (predictive accuracy, 81%). Improvement in measures of heart rate variation correlated with a decrease in LV mass. Parallel improvement of LV mass and autonomic function suggests a common mechanism, allowing for prediction of LV mass improvement through analysis of baseline heart rate variation.

Influence of Autonomic Nervous Dysfunction Characterizing Effect of Diabetes Mellitus on Heart Rate Response and Exercise Capacity in Patients Undergoing Cardiac Rehabilitation for Acute Myocardial Infarction

BACKGROUND

The aim of this study was to clarify the influence of sympathetic and parasympathetic nerve (SN and PN) dysfunction on the heart rate (HR) response to exercise and the exercise capacity of patients with acute myocardial infarction (AMI) and diabetes mellitus (DM).

METHODS AND RESULTS

Fifty-two male patients who underwent cardiopulmonary exercise testing (CPX) 1 month after onset of AMI were divided into 2 groups: (DM (+) group, n=20; DM (-) group, n=32). HR, peak oxygen uptake (VO2peak), and plasma norepinephrine (NE) levels were measured during CPX. The high-frequency power (HF) was analyzed by HR variability. The DeltaHR/logDeltaNE obtained from changes of HR and NE from rest to peak exercise and HR change from baseline to the minimum HF (DeltaHRHF) were calculated as parameters of HR response derived from SN and PN activities, respectively. DeltaHR, VO2peak, DeltaHR/logDeltaNE, and DeltaHRHF were significantly lower in the DM (+) group than in the DM (-) group, and both of them showed positive correlations with VO2peak.

CONCLUSION

An inadequate HR response to exercise is a major factor causing a decline of exercise capacity, which is derived from both of SN and PN dysfunction, in AMI patients with DM.