Time and frequency domain estimates of spontaneous baroreflex sensitivity provide early detection of autonomic dysfunction in diabetes mellitus

Impaired cardiopulmonary baroreflex function and altered cardiovascular responses to hypovolemia in patients with heart failure with preserved ejection fraction

Heart failure with preserved ejection fraction (HFpEF) is associated with autonomic dysregulation, which may be related to baroreflex dysfunction. Thus, we tested the hypothesis that cardiac and peripheral vascular responses to baroreflex activation via lower-body negative pressure (LBNP; -10, -20, -30, -40 mmHg) would be diminished in patients with HFpEF (n = 10, 71 ± 7 yr) compared with healthy controls (CON, n = 9, 69 ± 5 yr). Changes in heart rate (HR), mean arterial pressure (MAP, Finapres), forearm blood flow (FBF, ultrasound Doppler), and thoracic impedance (Z) were determined. Mild levels of LBNP (-10 and -20 mmHg) were used to specifically assess the cardiopulmonary baroreflex, whereas responses across the greater levels of LBNP represented an integrated baroreflex response. LBNP significantly increased in HR in CON subjects at -30 and -40 mmHg (+3 ± 3 and +6 ± 5 beats/min, P < 0.01), but was unchanged in patients with HFpEF across all LBNP levels. LBNP provoked progressive peripheral vasoconstriction, as quantified by changes in forearm vascular conductance (FVC), in both groups. However, a marked (40%-60%) attenuation in FVC responses was observed in patients with HFpEF (-6 ± 8, -15 ± 6, -16 ± 5, and -19 ± 7 mL/min/mmHg at -10, -20, -30, and -40 mmHg, respectively) compared with controls (-15 ± 10, -22 ± 6, -25 ± 10, and -28 ± 10 mL/min/mmHg, P < 0.01). MAP was unchanged in both groups. Together, these data provide new evidence for impairments in cardiopulmonary baroreflex function and diminished cardiovascular responsiveness during hypovolemia in patients with HFpEF, which may be an important aspect of the disease-related changes in autonomic cardiovascular control in this patient group.NEW & NOTEWORTHY Data from the current study demonstrate diminished cardiovascular responsiveness during hypovolemia induced by incremental lower-body negative pressure in patients with heart failure with preserved ejection fraction (HFpEF). These diminished responses imply impaired cardiopulmonary baroreflex function and altered autonomic cardiovascular regulation which may represent an important aspect of HFpEF pathophysiology.

Spontaneous baroreflex sensitivity is attenuated in male UCD-type 2 diabetes mellitus rats: A link between metabolic and autonomic dysfunction

Patients with type 2 diabetes mellitus (T2DM) have impaired arterial baroreflex function, which may be linked to the co-existence of obesity. However, the role of obesity and its related metabolic impairments on baroreflex dysfunction in T2DM is unknown. This study aimed to investigate the role of visceral fat and adiponectin, the most abundant cytokine produced by adipocytes, on baroreflex dysfunction in T2DM rats. Experiments were performed in adult male UCD-T2DM rats assigned to the following experimental groups (n = 6 in each): prediabetic (Pre), diabetes-onset (T0), 4 weeks after onset (T4), and 12 weeks after onset (T12). Age-matched healthy Sprague-Dawley rats were used as controls. Rats were anesthetized and blood pressure was directly measured on a beat-to-beat basis to assess spontaneous baroreflex sensitivity (BRS) using the sequence technique. Dual-energy X-ray absorptiometry (DEXA) was used to assess body composition. Data are presented as mean ± SD. BRS was significantly lower in T2DM rats compared with controls at T0 (T2D: 3.7 ± 3.2 ms/mmHg vs Healthy: 16.1 ± 8.4 ms/mmHg; P = 0.01), but not at T12 (T2D: 13.4 ± 8.1 ms/mmHg vs Healthy: 9.2 ± 6.0 ms/mmHg; P = 0.16). T2DM rats had higher visceral fat mass, adiponectin, and insulin concentrations compared with control rats (all P < 0.01). Changes in adiponectin and insulin concentrations over the measured time-points mirrored one another and were opposite those of the BRS in T2DM rats. These findings demonstrate that obesity-related metabolic impairments may contribute to an attenuated spontaneous BRS in T2DM, suggesting a link between metabolic and autonomic dysfunction.

The association between blood oxygen saturation and baroreflex sensitivity in adults with type 1 diabetes with and without albuminuria

BACKGROUND

Low baroreflex sensitivity is an indicator of early cardiovascular autonomic neuropathy. We explored the association between baroreflex sensivity and blood oxygen saturation (SpO₂) in type 1 diabetes and various degrees of microvascular disease.

METHODS

In this Danish-Finnish cross-sectional multicentre study, baroreflex sensivity and SpO₂ (pulse oximetry) were examined in persons with type 1 diabetes and normoalbuminuria (n = 98), microalbuminuria (n = 28), or macroalbuminuria (n = 43), and in non-diabetic controls (n = 54). Associations and differences between groups were analysed using regression models and adjustment included age, sex, smoking, HbA_1c, blood haemoglobin, urine albumin creatinine ratio, body mass index, and estimated glomerular filtration rate.

RESULTS

In type 1 diabetes, higher baroreflex sensitivity was associated with higher SpO₂ before adjustment (% increase per one % increase in SpO₂ = 20 % (95%CI: 11-30); p < 0.001) and the association remained significant after adjustment (p = 0.02). Baroreflex sensitivity was not different between non-diabetic controls and persons with type 1 diabetes and normoalbuminuria (p = 0.052). Compared with type 1 diabetes and normoalbuminuria, baroreflex sensitivity was lower in micro- (p < 0.001) and macroalbuminuria (p < 0.001). SpO₂ was lower in persons with type 1 diabetes and normoalbuminuria compared with non-diabetic controls (p < 0.01). Within the participants with type 1 diabetes, SpO₂ was not different in micro- or macroalbuminuria compared with normoalbuminuria (p-values > 0.05), but lower in macro-compared with microalbuminuria (p < 0.01).

CONCLUSIONS

Lower baroreflex sensitivity was associated with lower SpO₂ in type 1 diabetes. The present study support the hypothesis that hypoxia could be a therapeutic target in persons with type 1 diabetes.

Cardiovagal baroreflex sensitivity, blood pressure and blood pressure variability - the Maastricht study

OBJECTIVE

Low baroreflex sensitivity (BRS) has been hypothesized to underlie high blood pressure (BP) and greater BP variability on the longer term, but evidence is scarce. In addition, these associations may differ by sex and (pre)diabetes. Therefore, we investigated whether cardiovagal BRS is associated with short- to mid-term mean BP and BP variability, and differs according to sex and (pre)diabetes.

METHODS

Cross-sectional data from the population-based Maastricht study (age 60 ± 8 years, 52% men), where office ( n  = 2846), 24-h ( n  = 2404) and 7-day BP measurements ( n  = 2006) were performed. Spontaneous BRS was assessed by cross-correlating systolic BP and instantaneous heart rate. We used linear regression with adjustments for age, sex, BP or BP variability, and cardiovascular risk factors.

RESULTS

With regard to BP, 1-SD (standard deviation) lower BRS (-5.75 ms/mmHg) was associated with higher office, 24-h and 7-day systolic BP (2.22 mmHg [95% confidence interval [CI]: 1.59; 2.80], 0.95 mmHg [0.54; 1.36], and 1.48 mmHg [0.99; 1.97], respectively) and diastolic BP (1.31 mmHg [0.97; 1.66], 0.57 mmHg [0.30; 0.84], and 0.86 mmHg [0.54; 1.17], respectively). Per 1-SD lower BRS, these associations were stronger in women (0.5-1.5 mmHg higher compared to men), and weaker in those with type 2 diabetes (1-1.5 mmHg lower compared to normal glucose metabolism). With regard to BP variability, BRS was not consistently associated with lower BP variability.

CONCLUSIONS

Lower cardiovagal BRS is associated with higher mean BP from the short- to mid-term range, and not consistently with BP variability. The associations with mean BP are stronger in women and weaker in those with type 2 diabetes.

Heart rate variability in different sleep stages is associated with metabolic function and glycemic control in type 2 diabetes mellitus

Introduction: Autonomic nervous system (ANS) plays an important role in the exchange of metabolic information between organs and regulation on peripheral metabolism with obvious circadian rhythm in a healthy state. Sleep, a vital brain phenomenon, significantly affects both ANS and metabolic function. Objectives: This study investigated the relationships among sleep, ANS and metabolic function in type 2 diabetes mellitus (T2DM), to support the evaluation of ANS function through heart rate variability (HRV) metrics, and the determination of the correlated underlying autonomic pathways, and help optimize the early prevention, post-diagnosis and management of T2DM and its complications. Materials and methods: A total of 64 volunteered inpatients with T2DM took part in this study. 24-h electrocardiogram (ECG), clinical indicators of metabolic function, sleep quality and sleep staging results of T2DM patients were monitored. Results: The associations between sleep quality, 24-h/awake/sleep/sleep staging HRV and clinical indicators of metabolic function were analyzed. Significant correlations were found between sleep quality and metabolic function (|r| = 0.386 ± 0.062, p < 0.05); HRV derived ANS function showed strengthened correlations with metabolic function during sleep period (|r| = 0.474 ± 0.100, p < 0.05); HRV metrics during sleep stages coupled more tightly with clinical indicators of metabolic function [in unstable sleep: |r| = 0.453 ± 0.095, p < 0.05; in stable sleep: |r| = 0.463 ± 0.100, p < 0.05; in rapid eye movement (REM) sleep: |r| = 0.453 ± 0.082, p < 0.05], and showed significant associations with glycemic control in non-linear analysis [fasting blood glucose within 24 h of admission (admission FBG), |r| = 0.420 ± 0.064, p < 0.05; glycated hemoglobin (HbA1c), |r| = 0.417 ± 0.016, p < 0.05]. Conclusions: HRV metrics during sleep period play more distinct role than during awake period in investigating ANS dysfunction and metabolism in T2DM patients, and sleep rhythm based HRV analysis should perform better in ANS and metabolic function assessment, especially for glycemic control in non-linear analysis among T2DM patients.

Effect of Physical Exercise on Cardiac Autonomic Modulation in Hypertensive Individuals: A Systematic Review and Meta-analysis

BACKGROUND

Cardiac autonomic dysfunction is associated with hypertension and exercise training (ET) in healthy individuals is found to improve cardiac autonomic modulation (CAM). However, the effects of physical exercise on CAM in hypertensive individuals are under debate.

OBJECTIVE

The aim of the review is to systematically evaluate the literature on the effects of physical exercise on CAM in hypertensive individuals and analyse comparative differences in the effects of exercise between hypertensive and normotensive individuals.

METHODS

Electronic databases, such as Pubmed, PEDro, Scopus, and Web of Science, were systematically searched from inception up to February, 2022, evaluating the effect of ET on CAM either by heart rate variability (HRV), baroreflex sensitivity or heart rate recovery. Fifteen studies were included in the review. The risk of bias was assessed using the Cochrane risk of bias tool version 2 and the risk of bias in studies of intervention (ROBINS-I) tool. The overall quality of evidence was assessed using the grading of recommendations, assessment, development, and evaluation approach. Ten studies were included in the quantitative analysis. The meta-analysis and sensitivity analysis were performed using review manager 5.4.1; publication bias was assessed using Jamovi 2.2.5 software.

RESULTS

The qualitative analysis revealed low to moderate certainty of evidence for ET and moderate for aerobic training. For the effect of overall ET, the analysis revealed that the standardized mean differences (SMD) showed a significant effect of ET on HF (SMD 1.76, p = 0.04) and RMSSD (SMD 1.19, p < 0.0001) and a significant decrease in LF (SMD -1.78, p = 0.04). Aerobic training revealed nonsignificant improvement in HRV parameters. In the comparative analysis, ET did not show a significant difference in improvement between hypertensive and normotensive individuals.

CONCLUSION

This review suggests an improvement in CAM with physical exercise in hypertensive individuals, but the overall effect of ET in hypertensive individuals must be interpreted with caution as the robustness of the data is compromised in the sensitivity analysis of the trials. High-quality future trials focusing on different modes of ET interventions are needed to strengthen the findings of the present review.

Long-term variability and change trend of systolic blood pressure and risk of type 2 diabetes mellitus in middle-aged Japanese individuals: findings of the Aichi Workers' Cohort Study

Studies have reported that short-term blood pressure (BP) variability (BPV) is associated with type 2 diabetes mellitus (T2DM) incidence, but the association with long-term BPV remains unclear. The present study investigated the associations of long-term BPV as well as the time trend of BP changes over time with the incidence of T2DM. This study followed a cohort of 3017 Japanese individuals (2446 male, 571 female) aged 36-65 years from 2007 through March 31, 2019. The root-mean-square error (RMSE) and the slope of systolic BP (SBP) change regressed on year were calculated individually using SBP values obtained from 2003 to baseline (2007). A multivariable Cox proportional hazard model was applied to estimate hazard ratios (HRs) and corresponding 95% confidence intervals (CIs) for tertiles of SBP RMSE and continuous SBP slopes adjusted for age, sex, smoking status, regular exercise, sodium intake, family history of diabetes, sleep disorder, body mass index (BMI), SBP, and fasting blood glucose (FBG) at baseline, and BMI slope from 2003 to 2007. The highest RMSE tertile compared to the lowest was associated with a significantly higher incidence of T2DM after adjusting for covariates (HR: 1.79, 95% CI: 1.15, 2.78). The slope was also significantly associated with T2DM incidence until baseline SBP and FBG were adjusted (HR: 1.03, 95% CI: 0.99, 1.07). In conclusion, long-term SBP variability was significantly associated with an increased incidence of T2DM independent of baseline age, sex, BMI, SBP, FBG, lifestyle factors and BMI slope from 2003 until baseline.

A Novel Method for Baroreflex Sensitivity Estimation Using Modulated Gaussian Filter

The evaluation of baroreflex sensitivity (BRS) has proven to be critical for medical applications. The use of α indices by spectral methods has been the most popular approach to BRS estimation. Recently, an algorithm termed Gaussian average filtering decomposition (GAFD) has been proposed to serve the same purpose. GAFD adopts a three-layer tree structure similar to wavelet decomposition but is only constructed by Gaussian windows in different cutoff frequency. Its computation is more efficient than that of conventional spectral methods, and there is no need to specify any parameter. This research presents a novel approach, referred to as modulated Gaussian filter (modGauss) for BRS estimation. It has a more simplified structure than GAFD using only two bandpass filters of dedicated passbands, so that the three-level structure in GAFD is avoided. This strategy makes modGauss more efficient than GAFD in computation, while the advantages of GAFD are preserved. Both GAFD and modGauss are conducted extensively in the time domain, yet can achieve similar results to conventional spectral methods. In computational simulations, the EuroBavar dataset was used to assess the performance of the novel algorithm. The BRS values were calculated by four other methods (three spectral approaches and GAFD) for performance comparison. From a comparison using the Wilcoxon rank sum test, it was found that there was no statistically significant dissimilarity; instead, very good agreement using the intraclass correlation coefficient (ICC) was observed. The modGauss algorithm was also found to be the fastest in computation time and suitable for the long-term estimation of BRS. The novel algorithm, as described in this report, can be applied in medical equipment for real-time estimation of BRS in clinical settings.

Diagnostic Tools, Biomarkers, and Treatments in Diabetic polyneuropathy and Cardiovascular Autonomic Neuropathy

The various manifestations of diabetic neuropathy, including distal symmetric sensorimotor polyneuropathy (DSPN) and cardiovascular autonomic neuropathy (CAN), are among the most prevalent chronic complications of diabetes. Major clinical complications of diabetic neuropathies, such as neuropathic pain, chronic foot ulcers, and orthostatic hypotension, are associated with considerable morbidity, increased mortality, and diminished quality of life. Despite the substantial individual and socioeconomic burden, the strategies to diagnose and treat diabetic neuropathies remain insufficient. This review provides an overview of the current clinical aspects and recent advances in exploring local and systemic biomarkers of both DSPN and CAN assessed in human studies (such as biomarkers of inflammation and oxidative stress) for better understanding of the underlying pathophysiology and for improving early detection. Current therapeutic options for DSPN are (I) causal treatment, including lifestyle modification, optimal glycemic control, and multifactorial risk intervention, (II) pharmacotherapy derived from pathogenetic concepts, and (III) analgesic treatment against neuropathic pain. Recent advances in each category are discussed, including non-pharmacological approaches, such as electrical stimulation. Finally, the current therapeutic options for cardiovascular autonomic complications are provided. These insights should contribute to a broader understanding of the various manifestations of diabetic neuropathies from both the research and clinical perspectives.

Analysis of Medication Prescriptions for Hypertension in a Class 1 and Grade A Hospital in Shanxi Province

INTRODUCTION

This study aimed to examine the medication prescriptions for hypertension in a class 1 and grade A hospital in Shanxi province to provide references for clinical rational drug use.

METHODS

An inpatient medical record inquiry system was used to evaluate the use of antihypertensives in a hypertensive population (age ≥ 18 years old) who received a prescription for one or more antihypertensives between January 2017 and December 2019. The hypertensive population was categorized into grades (1, 2, and 3), age groups, and different comorbidities to analyze the medication prescriptions. Drug analysis included angiotensin-converting enzyme inhibitor (ACEI), angiotensin receptor antagonist (ARB), calcium channel blocker (CCB), diuretics, and beta-receptor blockers (B-RB). SPSS16.0 was used for statistical analysis, including one-way analysis of variance (ANOVA,) chi-squared test, and multifactor logistic regression analysis.

RESULTS

The overall control rate of blood pressure was 60.79%. The control rates of single, double, triple, and quadruple antihypertensives were 70.08%, 59.97%, 56.27%, and 45.23%, respectively. There were more cases of grade 3 than grades 1 and 2. The 18-65 years group was larger than the 66-79 years and ≥ 80 years groups. With the increase in grade, the prescription rate of the single drug decreased and the prescription rate of the combination drug increased, but this phenomenon was not obvious in different age groups. The most common drug prescribed for monotherapy was CCB; CCB combined with B-RB had the highest drug use in the double group by age or grade. Statistically significant differences were detected in the type of comorbidities between different age groups (P < 0.001), while only some differences were observed between different grades. Also, statistically significant differences were observed in the drugs prescribed for patients with hypertension with different comorbidities (P < 0.001). Factors influencing the efficiency of antihypertensives included sex, age, diabetes, heart failure, and usage of CCB and B-RB. The prescription rate of ARB combined with B-RB was relatively higher in grade 2 cases. B-RB was the primary drug for patients with diabetes, significantly increasing the blood glucose level.

CONCLUSIONS

The medication prescription of this hospital was in line with the requirements of China's hypertension prevention and treatment guidelines. The pathophysiology of patients with hypertension in different age groups, increased use of combination drugs, and rational drug requirement should be considered when prescribing drugs.

Characteristics of cardiovascular autonomic dysfunction and association with quality of life in patients with systemic lupus erythematosus

OBJECTIVES

Cardiovascular autonomic neuropathy (CAN) may affect the clinical course of SLE leading to reduced quality of life. CAN is assessed by heart rate variability (HRV) measures and cardiovascular autonomic reflex tests (CARTs). In patients with SLE, we aimed to determine the characteristics of CAN and if CAN associates with health-related quality of life (HRQoL).

METHODS

Patients with SLE and healthy controls (HCs) were CAN tested with 5 min HRV and three CARTs to determine parameters reflecting parasympathetic and mixed sympathetic-parasympathetic function. Subjects were classified as having no, early or definitive CAN by having none, one or more than one abnormal CART, respectively. HRQoL as determined by the Short Form 12 (SF-12) was assessed in SLE.

RESULTS

Of 111 patients with SLE, 92 answered the SF-12 and 54 were matched with 54 HCs for characterisation of CAN. Definitive CAN was present in 24.1% (95% CI 15% to 37%) patients with SLE and 1.9% (95% CI 0.3% to 9.8%) HCs (OR 16.8, 95% CI 2.1 to 133.8, p=0.008). The corresponding prevalences of any CAN were 53.7% (95% CI 41% to 66%) and 22.6% (95% CI 13% to 35%). SLE patients with definitive CAN showed signs of mixed sympathetic-parasympathetic dysfunction, whereas patients without CAN primarily presented with impaired parasympathetic activity. Signs of parasympathetic as well as sympathetic-parasympathetic dysfunction were associated with low physical SF-12 component score (all: β>0.211, p<0.05). The mental SF-12 component score was not associated with any CAN indices.

CONCLUSIONS

CAN was a frequent finding in SLE and associated to self-report on impaired physical HRQoL. Even patients without CAN showed signs of impaired parasympathetic function compared with controls.

Sympathetic neural abnormalities in type 1 and type 2 diabetes: a systematic review and meta-analysis

BACKGROUND

Microneurographic recordings of muscle sympathetic nerve activity (MSNA) have shown that sympathetic activation may characterize diabetes mellitus. However, it is recognized that comorbidities and metabolic abnormalities frequently associated with both type 1 diabetes mellitus (T1DM) and type 2 diabetes mellitus (T2DM) diabetes affect MSNA, generating potential confounding effects and making the association between sympathetic activation and diabetes mellitus still a controversial matter.

METHODS

The present meta-analysis evaluated 11 microneurographic studies enrolling 314 diabetes mellitus patients and healthy controls, and MSNA was chosen as the main variable of interest. Collection of the data included indirect adrenergic markers such as heart rate and venous plasma noradrenaline, together with hemodynamic, anthropometric and metabolic variables.

RESULTS

A total of 11 microneurographic studies were evaluated including 314 diabetes mellitus patients and controls. Diabetes mellitus displayed MSNA significantly greater than controls (mean difference amounting to 8.1, 95% confidence interval 1.21-15.08, P < 0.05). This difference was ascribed to T2DM, since T1DM patients displayed MSNA values superimposable to controls. In T2DM MSNA was directly related to age (r = 0.83, β = 0.82, P < 0.04) and plasma insulin (r = 1.00, β = 2.25, P < 0.01) but not to other variables.

CONCLUSION

T2DM-related sympathetic activation is detectable even when obesity, hypertension and metabolic syndrome are excluded; not found in T1DM; not associated with anthropometric and hemodynamic variables; and related to plasma insulin.

Baroreflex sensitivity with different lags and random forests for staging cardiovascular autonomic neuropathy in subjects with diabetes

Impaired baroreflex sensitivity (BRS) may indicate cardiovascular autonomic neuropathy (CAN), which often remains undiagnosed during the initial course of diabetes mellitus. The baroreflex mechanism can be considered negative feedback because of baroreflex delay, the time delay between a change in blood pressure and the counteracting heart rate response. This work sought to analyze BRS considering lags from 1 to 10 RR intervals. We hypothesized that diabetic patients with subclinical CAN (SCAN) have a detectable delay in autonomic nervous system activity and that this would differ from patients without CAN (NCAN) and with established CAN (ECAN). In the first stage, 30 patients were included in an exploratory analysis using the Principal Component Analysis. Six indexes related to the BRS delay were proposed and considered significant for staging diabetic patients. Three indexes allowed for the differentiating of patients with and without CAN, and three indexes distinguished subjects with SCAN from subjects with NCAN or ECAN. Then, in the second stage, a random forest model was developed with 72 subjects, using the variables selected in the first stage. It was possible to detect SCAN, and to point out those subjects with the potential to change the CAN stage, allowing for the tracking of CAN progression. The model achieved a sensitivity of 96% and specificity of 100% to detect SCAN. Thus, the BRS analysis considering delayed reaction in the dynamics of heart rate variability may contribute to an accurate screening tool to staging CAN, in addition to indicating patients with most insidious disease progress.

The autonomic nervous system in its natural environment: Immersion in nature is associated with changes in heart rate and heart rate variability

Stress Recovery Theory (SRT) suggests that time spent in nature reduces stress. While many studies have examined changes in stress physiology after exposure to nature imagery, nature virtual reality, or nature walks, this study is the first to examine changes in heart rate (HR) and vagally mediated HR variability, as assessed by Respiratory Sinus Arrythmia (RSA), after a longer duration of nature exposure. Consistent with SRT, we hypothesized that immersion in nature would promote stress recovery, as indexed by an increase in RSA and a decrease in HR. We also predicted that exposure to nature would improve self-reported mood. We used a within-subjects design (N = 67) to assess changes in peripheral physiology before, during, and after a 5-day nature trip. Results demonstrated a significant decrease in RSA and a significant increase in HR during the trip compared to before or after the trip, suggesting that immersion in nature is associated with a shift toward parasympathetic withdrawal and possible sympathetic activation. These results were contrary to our hypotheses and may suggest increased attentional intake or presence of emotions associated with an increase in sympathetic activation. We also found an improvement in self-reported measures of mood during the trip compared to before or after the trip, confirming our hypotheses and replicating previous research. Implications of this study are discussed in the context of SRT.

Influence of cardiac autonomic neuropathy on cardiac repolarisation during incremental adrenaline infusion in type 1 diabetes

AIMS/HYPOTHESIS

We examined the effect of a standardised sympathetic stimulus, incremental adrenaline (epinephrine) infusion on cardiac repolarisation in individuals with type 1 diabetes with normal autonomic function, subclinical autonomic neuropathy and established autonomic neuropathy.

METHODS

Ten individuals with normal autonomic function and baroreceptor sensitivity tests (NAF), seven with subclinical autonomic neuropathy (SAN; normal standard autonomic function tests and abnormal baroreceptor sensitivity tests); and five with established cardiac autonomic neuropathy (CAN; abnormal standard autonomic function and baroreceptor tests) underwent an incremental adrenaline infusion. Saline (0.9% NaCl) was infused for the first hour followed by 0.01 μg kg^-1 min^-1 and 0.03 μg kg^-1 min^-1 adrenaline for the second and third hours, respectively, and 0.06 μg kg^-1 min^-1 for the final 30 min. High resolution ECG monitoring for QT_c duration, ventricular repolarisation parameters (T wave amplitude, T wave area symmetry ratio) and blood sampling for potassium and catecholamines was performed every 30 min.

RESULTS

Baseline heart rate was 68 (95% CI 60, 76) bpm for the NAF group, 73 (59, 87) bpm for the SAN group and 84 (78, 91) bpm for the CAN group. During adrenaline infusion the heart rate increased differently across the groups (p = 0.01). The maximum increase from baseline (95% CI) in the CAN group was 22 (13, 32) bpm compared with 11 (7, 15) bpm in the NAF and 10 (3, 18) bpm in the SAN groups. Baseline QT_c was 382 (95% CI 374, 390) ms in the NAF, 378 (363, 393) ms in the SAN and 392 (367, 417) ms in the CAN groups (p = 0.31). QT_c in all groups lengthened comparably with adrenaline infusion. The longest QT_c was 444 (422, 463) ms (NAF), 422 (402, 437) ms (SAN) and 470 (402, 519) ms (CAN) (p = 0.09). T wave amplitude and T wave symmetry ratio decreased and the maximum decrease occurred earlier, at lower infused adrenaline concentrations in the CAN group compared with NAF and SAN groups. AUC for the symmetry ratio was different across the groups and was lowest in the CAN group (p = 0.04). Plasma adrenaline rose and potassium fell comparably in all groups.

CONCLUSIONS/INTERPRETATION

Participants with CAN showed abnormal repolarisation in some measures at lower adrenaline concentrations. This may be due to denervation adrenergic hypersensitivity. Such individuals may be at greater risk of cardiac arrhythmias in response to physiological sympathoadrenal challenges such as stress or hypoglycaemia.

Impairment in Baroreflex Sensitivity in Recent-Onset Type 2 Diabetes Without Progression Over 5 Years

Impaired baroreflex sensitivity (BRS) predicts cardiovascular mortality and is prevalent in long-term diabetes. We determined spontaneous BRS in patients with recent-onset diabetes and its temporal sequence over 5 years by recording beat-to-beat blood pressure and R-R intervals over 10 min. Four time domain and four frequency domain BRS indices were computed in participants from the German Diabetes Study baseline cohort with recent-onset type 1/type 2 diabetes (n = 206/381) and age-matched glucose-tolerant control subjects (control 1/control 2: n = 65/83) and subsets of consecutive participants with type 1/type 2 diabetes who reached the 5-year follow-up (n = 84/137). Insulin sensitivity (M-value) was determined using a hyperinsulinemic-euglycemic clamp. After appropriate adjustment, three frequency domain BRS indices were reduced in type 2 diabetes compared with control 2 and were positively associated with the M-value and inversely associated with fasting glucose and HbA_1c (P < 0.05), whereas BRS was preserved in type 1 diabetes. After 5 years, a decrease in one and four BRS indices was observed in patients with type 1 and type 2 diabetes, respectively (P < 0.05), which was explained by the physiologic age-dependent decline. Unlike patients with well-controlled recent-onset type 1 diabetes, those with type 2 diabetes show early baroreflex dysfunction, likely due to insulin resistance and hyperglycemia, albeit without progression over 5 years.

Type 2 Diabetes Mellitus Is Independently Associated With Decreased Neural Baroreflex Sensitivity: The Paris Prospective Study III

OBJECTIVE

Impaired baroreflex function is an early indicator of cardiovascular autonomic imbalance. Patients with type 2 diabetes mellitus (T2D) have decreased baroreflex sensitivity (BRS), however, whether the neural BRS (nBRS) and mechanical component of the BRS is altered in those with high metabolic risk (HMR, impaired fasting glucose and metabolic syndrome) or with overt T2D, is unknown. We examined this in a community-based observational study, the Paris Prospective Study III (PPS3). Approach and Results: In 7626 adults aged 50 to 75 years, resting nBRS (estimated by low-frequency gain, from carotid distension rate and RR [time elapsed between two successive R waves] intervals) and mechanical BRS were measured by high-precision carotid echotracking. The associations between overt T2D or HMR as compared with subjects with normal glucose metabolism and nBRS or mechanical BRS were quantified using multivariable linear regression analysis. There were 319 subjects with T2D (61±6 years, 77% male), 1450 subjects with HMR (60±6 years, 72% male), and 5857 subjects with normal glucose metabolism (59±6 years, 57% male). Compared with normal glucose metabolism, nBRS was significantly lower in HMR subjects (β=-0.07 [95% CI, -0.12 to -0.01]; P=0.029) and in subjects with T2D (β=-0.18 [95% CI, -0.29 to -0.07]; P=0.002) after adjustment for confounding and mediating factors. Subgroup analysis suggests significant and independent alteration in mechanical BRS only among HMR patients who had both impaired fasting glucose and metabolic syndrome.

CONCLUSIONS

In this community-based study of individuals aged 50 to 75, a graded decrease in nBRS was observed in HMR subjects and patients with overt T2D as compared with normal glucose metabolism subjects.

Cortisol rapidly increases baroreflex sensitivity of heart rate control, but does not affect cardiac modulation of startle

Cortisol, the final product of human HPA axis activation, rapidly modulates the cortical processing of afferent signals originating from the cardiovascular system. While peripheral effects have been excluded, it remains unclear whether this effect is mediated by cortical or subcortical (e.g. brainstem) CNS mechanisms. Cardiac modulation of startle (CMS) has been proposed as a method to reflect cardio-afferent signals at subcortical (potentially brainstem-) level. Using a single blind, randomized controlled design, the cortisol group (n = 16 volunteers) received 1 mg cortisol intravenously, while the control group (n = 16) received a placebo substance. The CMS procedure involved the assessment of eye blink responses to acoustic startle stimuli elicited at six different latencies to ECG-recorded R-waves (R + 0, 100, 200, 300, 400 and 500 ms). CMS was assessed at four measurement points: baseline, -16 min, +0 min, and +16 min relative to substance application. Baroreflex sensitivity (BRS) of heart rate (HR) control was measured non-invasively based on spontaneous beat-to-beat HR and systolic blood pressure changes. In the cortisol group, salivary cortisol concentration increased after IV cortisol administration, indicating effective distribution of the substance throughout the body. Furthermore, BRS increased in the cortisol group after cortisol infusion. There was no effect of cortisol on the CMS effect, however. These results suggest that low doses of cortisol do not affect baro-afferent signals, but central or efferent components of the arterial baroreflex circuit presumably via rapid, non-genomic mechanisms.

Acute effect of photobiomodulation using light-emitting diodes (LEDs) on baroreflex sensitivity during and after constant loading exercise in patients with type 2 diabetes mellitus

To evaluate the photobiomodulation (PBM) effect on the cardiovascular autonomic control, analyzed by baroreflex sensitivity (sequence method), during constant load exercise and recovery in diabetic men, we evaluated 11 men with type 2 diabetes (DM2) (40-64 years). The constant workload exercise protocol (TECC) was performed on two different days, 14 days apart from each other, to guarantee PBM washout period. After PBM by light-emitting diode (LED) irradiation (150 J or 300 J or placebo), 10 min of rest (REST) was performed. After this period, the volunteer was positioned on a cycloergometer to start the test (1-min rest, 3-min free-load heating, 6-min constant workload-EXERCISE, 6-min free-load cool-down, 1-min rest) followed by a sitting period of 10 min (RECOVERY). The constant workload corresponded to 80%VO_2GET (gas exchange threshold) identified by a previous cardiopulmonary exercise test (CPET). PBM was applied in continuous mode, contact technique, bilaterally, on both femoral quadriceps and gastrocnemius muscle groups. The electrocardiogram R-R intervals (BioAmp FE132) and the peripheral pulse pressure signals (Finometer PRO) were collected continuously throughout the protocol. Stable sequences of 256 points were chosen at REST, EXERCISE, and RECOVERY. The baroreflex sensitivity (BRS) was computed in time domain according to the sequence method (α_seq). The comparison between therapies (150 J/300 J/placebo) and condition (REST, EXERCISE, and RECOVERY) was performed using the ANOVA two-way repeated measures test. There was no interaction between therapy and conditions during the TECC. There was only the condition effect (p < 0.001), showing that the behavior of α_seq was similar regardless of the therapy. Photobiomodulation with 150 J or 300 J applied previously to a moderate-intensity TECC in DM2 was not able to promote cardiovascular autonomic control changes leading to an improvement in BRS.

Clinical Implications of Baroreflex Sensitivity in Type 2 Diabetes

The evaluation of baroreflex sensitivity (BRS), which maintains systemic circulatory homeostasis, is an established tool to assess cardiovascular autonomic neuropathy in type 2 diabetes mellitus (T2DM). As BRS plays an important function in blood pressure regulation, reduced BRS leads to an increase in blood pressure variability, which further leads to reduced BRS. This sequence of events becomes a vicious cycle. The major risk factors for reduced BRS are T2DM and essential hypertension, but many other risk factors have been reported to influence BRS. In recent years, reports have indicated that glycemic variability (GV), such as short- and long-term GV that are considered important risk factors for macrovascular and microvascular complications, is involved in reductions in BRS independently of blood glucose levels. In this review, we discuss reduced BRS in T2DM, its features, and the potential for its reversal.

Resistance training and modulation of cardiac autonomic control in animal models: a systematic review

The purpose of the present review is to systematically evaluate the existing literature on the effects of resistance training (RT) on cardiac autonomic control in animal models. Electronic search was conducted in Pubmed, PEDro and Scopus databases from inception till June 2018. Randomised controlled trials and quasi-experimental trials which investigated the effects of RT (for at least 4 weeks) on cardiac autonomic control (assessed either by heart rate variability, baroreflex sensitivity or post-exercise heart rate recovery) in animal models were included. Out of the total 3,442 studies retrieved by the electronic search, 9 were found to be suitable as per the eligibility criteria and were included in this review. The majority of these studies (6 out of 9) demonstrated improvement in cardiovascular autonomic control after RT in animals; however, three studies did not illustrate any significant change. Standardised mean differences (SMD) showed a significant effect of RT on root mean square of successive differences between adjacent inter-beat (R-R) intervals (RMSSD) [SMD (confidence interval (CI)) = 4.56 (2.89, 6.23); P<0.0001] and bradycardic response to change in arterial blood pressure [SMD (CI)=-2.27 (-4.50, -0.03; P=0.05)] whereas no significant change was observed for other variables of cardiac autonomic control post-RT. The present systematic review do not give a clear conclusion regarding the effect of RT on cardiac autonomic control in animal models and thus highlight the need for good quality research in future.

Cystatin C Is an Important Biomarker for Cardiovascular Autonomic Dysfunction in Chinese Type 2 Diabetic Patients

BACKGROUND

Cardiovascular autonomic dysfunction is closely related to increased mortality in patients with diabetes. Previous studies have proved that cystatin C (CysC) is an important predictor of both peripheral neuropathy and cardiovascular events. However, whether CysC is also associated with cardiovascular autonomic dysfunction remains unclear. Therefore, the aim of this study was to investigate the relationship between CysC and cardiovascular autonomic dysfunction in type 2 diabetic patients without renal dysfunction.

METHODS

A total of 161 type 2 diabetic patients with normal serum creatinine (less than 133 μmol/l) and estimated glomerular filtration rate (eGFR) higher than 60 ml/min per 1.73 m² were recruited in our study. Cardiovascular autonomic dysfunction was determined by heart rate variability (HRV) measured by a 24-hour Holter monitor. Serum CysC was tested by particle-enhanced turbidimetric immunoassay, and subjects were divided into three groups based on the tertiles of CysC. Pearson correlation analysis was used to evaluate the association between different indexes, and the association of CysC with HRV indexes was assessed by multivariate linear regression analysis.

RESULTS

The HRV parameters were lower in the group with the highest CysC concentration than in the groups with lower levels of CysC (P < 0.05). Pearson correlation analysis showed a negative relationship between CysC and the HRV parameters, including SDNN (r = -0.31, P < 0.001), SDANN (r = -0.25, P = 0.002), and logLF (r = -0.18, P = 0.023). Furthermore, multivariate linear regression analysis revealed that CysC was independently correlated with SDNN (β = -24.11, P = 0.015) and SDANN (β = -19.88, P = 0.047) after adjusting for the confounding factors of gender, age, blood pressure, body mass index, eGFR, and hemoglobin A1c.

CONCLUSIONS

Serum CysC levels are associated with cardiovascular autonomic dysfunction; furthermore, CysC may be a reliable and convenient biomarker for detecting cardiovascular autonomic dysfunction.

Comparison of anthropometric, cardiovascular, autonomic, baroreflex sensitivity, aerobic fitness, inflammatory markers and oxidative stress parameters between first degree relatives of diabetes and controls

AIM

We aimed at assessing cardiovascular risk of first degree relatives of diabetes (FDRD).

METHODS

A cross sectional study involving 90 apparently healthy normoglycemic volunteers aged between 15 and 50 years (45 FDRD and 45 FDRs of non-diabetics). We measured anthropometric parameters, baroreflex sensitivity, heart rate variability, cardiac autonomic function tests, and aerobic capacity, fasting blood glucose and insulin, lipid profile, inflammatory markers, nitric oxide and oxidative stress markers.

RESULTS

FDRD had significantly higher hip circumference and BF%. Blood pressure, total peripheral resistance and cardiac output were comparable. FDRD had higher HR and rate pressure product. There were no significant differences in cardio-respiratory fitness (VO2max) and physical activity level. Time and Frequency domain parameters were comparable except for reduced NN50 and total power. Baroreflex sensitivity, 30:15 ratio and E: I ratio were significantly less in FDRD. Fasting glucose was comparable. Fasting Insulin, HOMA IR, HOMA %B and HOMA AD were higher while HOMA %S and QUICKI index were lower in FDRD. Lipid profile or lipid derived parameters were comparable except for higher non-HDLc in FDRD. Adiponectin was lower while Leptin and Leptin/apidonectin ratio was higher in FDRD. IL-6, hsCRP, TNF- alpha and MDA were significantly higher in FDRD, while TAS and nitric oxide were significantly lower in FDRD.

CONCLUSION

Higher body fat percentage, with insulin resistance, deranged cardiac autonomic function, higher oxidative stress and inflammation, lower adiponectin and nitric oxide levels places FDRD at higher cardiovascular risk and necessitates early lifestyle modification/intervention.

Association of glucose and blood pressure variability on oxidative stress in patients with type 2 diabetes mellitus and hypertension: a cross-sectional study

BACKGROUND

The present study evaluated the effects of glucose and blood pressure (BP) variability on oxidative stress in patients with type 2 diabetes mellitus (T2DM) and hypertension.

METHODS

A total of 60 inpatients with T2DM underwent continuous glucose monitoring (CGM) and ambulatory BP monitoring (ABPM). Oxidative stress was estimated using the diacron-reactive oxygen metabolites (d-ROMs) test. Glucose variability, mean glucose level, percentage coefficient of variation for glucose, mean amplitude of glycemic excursions (MAGE), and area under the postprandial plasma glucose curve were determined through CGM. BP variability was assessed by measuring average BP, standard deviation (SD) of systolic and diastolic BP, and coefficient of variation (CV) of systolic and diastolic BP during daytime and nighttime ABPM.

RESULTS

Participants had a mean age of 64.5 ± 13.3 years with the duration of the disease 13.9 ± 12.4 years and HbA1c of 8.5 ± 1.2%. Univariate analysis showed that MAGE, nighttime SDs of systolic and diastolic BP, and nighttime CV of systolic BP were significantly correlated with d-ROMs. Further, stepwise multiple regression analysis identified MAGE, nighttime SD and CV of diastolic BP, estimated glomerular filtration rate, and smoking as independent contributors to d-ROMs.

CONCLUSIONS

Oxidative stress was associated with daily glucose and nighttime diastolic BP variability in patients with T2DM and hypertension.Trial registration UMIN Clinical Trial Registry UMIN000035615, Registered January 22, 2019-retrospectively registered.

Diabetes mellitus attenuates the pressure response against hypotensive stress by impairing the sympathetic regulation of the baroreflex afferent arc

Patients with diabetes mellitus (DM) often show arterial pressure (AP) lability associated with cardiovascular autonomic neuropathy. Because the arterial baroreflex tightly regulates AP via sympathetic nerve activity (SNA), we investigated the systematic baroreflex function, considering the control theory in DM by open-loop analysis. We used Zucker diabetic fatty (ZDF) rats as a type 2 DM model. Under general anesthesia, we isolated the carotid sinuses from the systemic circulation, changed intracarotid sinus pressure (CSP), and recorded SNA and AP responses. We compared CSP-AP (total loop), CSP-SNA (afferent arc), and SNA-AP (efferent arc) relationships between ZDF lean ( n = 8) and ZDF fatty rats ( n = 6). Although the total loop gain of baroreflex (ΔAP/ΔCSP) at the operating point did not differ between the two groups, the average gain in the lower CSP range was markedly reduced in ZDF fatty rats (0.03 ± 0.01 vs. 0.87 ± 0.10 mmHg/mmHg, P < 0.001). The afferent arc showed the same trend as the total loop, with a response threshold of 139.8 ± 1.0 mmHg in ZDF fatty rats. There were no significant differences in the gain of efferent arc between the two groups. Simulation experiments indicated a markedly higher AP fall and lower total loop gain of baroreflex in ZDF fatty rats than in ZDF lean rats against hypotensive stress because the efferent arc intersected with the afferent arc in the SNA unresponsive range. Thus, we concluded that impaired baroreflex sympathetic regulation in the lower AP range attenuates the pressure response against hypotensive stress and may partially contribute to AP lability in DM. NEW & NOTEWORTHY In this study, we investigated the open-loop baroreflex function, considering the control theory in type 2 diabetes mellitus model rats to address the systematic mechanism of arterial pressure (AP) lability in diabetes mellitus. The unresponsiveness of baroreflex sympathetic regulation in the lower AP range was observed in type 2 diabetic rats. It may attenuate the baroreflex pressure-stabilizing function and induce greater AP fall against hypotensive stress.

Impaired baroreflex sensitivity and increased systolic blood pressure variability in chronic post-ischemic stroke

OBJECTIVES

Acute post-stroke patients present cardiovascular autonomic dysfunction, which manifests as lower heart rate variability and impaired baroreflex sensitivity. However, few studies performed to date have evaluated cardiovascular autonomic function in chronic post-stroke patients. The aim of this study was to evaluate cardiovascular autonomic modulation in chronic post-ischemic stroke patients.

METHODS

The seventeen enrolled subjects were divided into a stroke group (SG, n=10, 5±1 years after stroke) and a control group (CG, n=7). Non-invasive curves for blood pressure were continuously recorded (Finometer®) for 15 minutes while the subject was in a supine position. Heart rate variability and blood pressure variability were analyzed in the time and frequency domains.

RESULTS

No differences were observed in systolic and diastolic pressure and heart rate between post-stroke patients and healthy individuals. The SG group had lower indexes for heart rate variability in the time domain (standard deviation of normal to normal R-R intervals, SDNN; variance of normal to normal R-R intervals, VarNN; and root mean square differences of successive R-R intervals, RMSSD) and a lower high-frequency band for heart rate variability than was observed in the CG. Systolic blood pressure variability and the low-frequency band for systolic pressure were higher in post-stroke patients, while the alpha index was lower in the SG than in the CG.

CONCLUSION

After ischemic stroke, affected patients present chronically reduced heart rate variability, impaired cardiac vagal modulation, increased systolic blood pressure variability and higher sympathetic vascular modulation along with impaired baroreflex sensitivity, which can increase the risk of cardiovascular events, despite adequate blood pressure control.

Does resistance training modulate cardiac autonomic control? A systematic review and meta-analysis

PURPOSE

To systematically evaluate the literature on the effects of resistance training (RT) on cardiac autonomic control in healthy and diseased individuals.

METHODS

Electronic databases Pubmed, PEDro, and Scopus were systematically searched from their inception up to June 2018. Randomized controlled trials, quasi-experimental trials, and cross-over controlled trials investigating the effect of RT (of at least 4 weeks duration) on cardiac autonomic control assessed either by linear or non-linear measures of heart rate variability (HRV), baroreflex sensitivity, or post-exercise heart rate recovery were included. Of the studies retrieved, 28 were included in the systematic review. Meta-analysis was performed on 21 studies of the total 28 studies.

RESULTS

Quality and characteristic assessment revealed fair quality evidence. The majority of literature on healthy humans suggested no change in cardiac autonomic control following RT. Standardized mean differences (SMD) showed a significant effect of RT on root mean square of successive differences between adjacent inter-beat (R-R) intervals (RMSSD) [SMD 0.96, 95% confidence interval (CI) 0.20-1.73; p = 0.01], ratio of low- to high-frequency power of HRV (LF/HF ratio; SMD -0.72, 95% CI -1.03 to -0.42; p < 0.00001), standard deviation of the instantaneous beat-to-beat variability (SD1; SMD 1.78, 95% CI 1.07-2.49, p < 0.00001), and sample entropy (SMD 1.17, 95% CI 0.36-1.97, p = 0.005) in diseased individuals.

CONCLUSION

This rigorous systematic analysis revealed that RT has no or minimal effects on cardiac autonomic control of healthy individuals, but RT leads to improvement in cardiac autonomic control of diseased individuals.

Visit-to-visit HbA1c variability is inversely related to baroreflex sensitivity independently of HbA1c value in type 2 diabetes

BACKGROUND

The relationship between long-term glycemic variability (GV) represented by visit-to-visit HbA1c variability and baroreflex sensitivity (BRS) in type 2 diabetes mellitus (T2DM) has not been clarified by previous literature. The present study is the first to examine the relationships between visit-to-visit HbA1c variability and BRS.

METHODS

This retrospective study initially analyzed data on 94 patients with T2DM. Visit-to-visit HbA1c variability was evaluated using the intrapersonal coefficient of variation (CV), standard deviation (SD), and adjusted SD of 8 or more serial measurements of HbA1c during a 2-year period. The BRS was analyzed using the sequence method. Short-term GV was assessed by measuring the glucose CV during 24-h continuous glucose monitoring (CGM). The primary objective was to determine if there was a relationship between visit-to-visit HbA1c variability (HbA1c CV) and BRS. Secondary objectives were to examine the relationship between other variables and BRS and the respective and combined effects of long-term GV (HbA1c CV) and short-term GV (CGM CV) on BRS.

RESULTS

A total of 57 patients (mean age 67.2 ± 7.7 years, mean HbA1c 7.3 ± 1.0%) who met this study's inclusion criteria were finally analyzed. In the univariate analysis, HbA1c CV (r = - 0.354, p = 0.007), HbA1c SD (r = - 0.384, p = 0.003), and adjusted HbA1c SD (r = - 0.391, p = 0.003) were significantly related to low levels of BRS. Multiple regression analysis showed that HbA1c CV, HbA1c SD, and adjusted HbA1c SD were inversely related to BRS. Furthermore, although the increase in either long-term GV (HbA1c CV) or short-term GV (CGM CV) as determined by 24-h CGM was inversely correlated with BRS, additional reductions in BRS were not shown in participants with both HbA1c CV and CGM CV values above the median.

CONCLUSIONS

Visit-to-visit HbA1c variability was inversely related to BRS independently of the mean HbA1c in patients with T2DM. Therefore, visit-to-visit HbA1c variability might be a marker of reduced BRS in T2DM.

Glycemic variability in continuous glucose monitoring is inversely associated with baroreflex sensitivity in type 2 diabetes: a preliminary report

Background

It is presently unclear whether glycemic variability (GV) is associated with baroreflex sensitivity (BRS), which is an early indicator of cardiovascular autonomic neuropathy. The present study is the first to examine the relationships between BRS and GV measured using continuous glucose monitoring (CGM).

Methods

This was a multicenter, prospective, open-label clinical trial. A total of 102 patients with type 2 diabetes were consecutively recruited for this study. GV was assessed by measuring the standard deviation (SD), glucose coefficient of variation (CV), and the mean amplitude of glycemic excursions (MAGE) during CGM. The BRS was analyzed from electrocardiogram and blood pressure recordings using the sequence method on the first day of hospitalization.

Results

A total of 94 patients (mean diabetes duration 9.7 ± 9.6 years, mean HbA1c 61.0 ± 16.8 mmol/mol [7.7 ± 1.5%]) were analyzed. In the univariate analysis, CGM-SD (r = − 0.375, p = 0.000), CGM-CV (r = − 0.386, p = 0.000), and MAGE (r = − 0.395, p = 0.000) were inversely related to BRS. In addition to GV, the level of BRS correlated with the coefficient of variation in the R–R intervals (CVR-R) (r = 0.520, p = 0.000), heart rate (HR) (r = − 0.310, p = 0.002), cardio-ankle vascular index (CAVI) (r = − 0.326, p = 0.001), age (r = − 0.519, p = 0.000), and estimated glomerular filtration rate (eGFR) (r = 0.276, p = 0.007). Multiple regression analysis showed that CGM-CV and MAGE were significantly related to a decrease in BRS. These findings remained after adjusting the BRS for age, sex, hypertension, dyslipidemia, HR, eGFR, CAVI, and CGM-mean glucose. Additionally, BRS was divided according to quartiles of the duration of diabetes (Q1–4). BRS decreased after a 2-year duration of diabetes independently of age and sex.

Conclusions

GV was inversely related to BRS independently of blood glucose levels in type 2 diabetic patients. Measurement of BRS may have the potential to predict CV events in consideration of GV.

Trial registration UMIN Clinical Trials Registry UMIN000025964, 28/02/2017

Electronic supplementary material

The online version of this article (10.1186/s12933-018-0683-2) contains supplementary material, which is available to authorized users.

Blood pressure targets in type 2 diabetes. Evidence against or in favour of an aggressive approach

When associated with high blood pressure, type 2 diabetes mellitus is characterised by a high risk of adverse cardiovascular (CV) and renal outcomes. However, both can be effectively reduced by antihypertensive treatment. Current guidelines on the treatment of hypertension emphasize the need to effectively treat high blood pressure in diabetic individuals, but their recommendations differ in terms of the optimal target blood pressure value to aim for in order to maximise CV and renal protection. In some guidelines the recommended target blood pressure values are <140/90 mmHg (systolic/diastolic), whereas in others, blood pressure values close or even less than 130/80 mmHg are recommended. This paper will discuss the evidence for and against a conservative or more aggressive blood pressure target for treated diabetic hypertensive individuals based on the evidence provided by randomised trials, trial meta-analyses and large observational studies. Based on the available evidence, it appears that blood pressure targets will probably have to be lower than <140/90 mmHg, and that values approaching 130/80 mmHg should be recommended. However, evidence in favour of even lower systolic values, i.e. <130 mmHg, is limited and is definitively against a reduction to <120 mmHg.

Exercise training and cardiac autonomic function in type 2 diabetes mellitus: A systematic review

Cardiac autonomic neuropathy (CAN) is a common complication of type 2 diabetes mellitus (T2DM). It has been found to independently predict all cause and cardiovascular disease (CVD) mortality. It remains unclear whether exercise training could improve autonomic control in T2DM patients. The purpose of this study was to systematically review the effects of exercise training on cardiac autonomic function in T2DM patients. Electronic databases (MEDLINE, CENTRAL, PEDro, Scopus and Web of science) were systematically searched to retrieve relevant evidence. Clinical trials administering exercise training for at least 4 weeks and examining either heart rate variability (HRV), baroreflex sensitivity (BRS), heart rate recovery (HRR) as outcome measures were eligible. Eighteen articles were found to be relevant and were then assessed for characteristics and quality. Fifteen studies out of 18 found that exercise training leads to positive improvements in autonomic function of T2DM patients. Exercise participation enhances cardiac autonomic function of type 2 diabetics and therefore should be implemented in their management programs.

Association between day-by-day and ambulatory blood pressure variability in type 2 diabetes patients

It remains unclear whether ambulatory blood pressure variability (BPV) contributes toward day-by-day BPV, despite the fact that not only day-by-day but also ambulatory BPV is reported to be a risk factor for type 2 diabetes patients. This study aimed to determine the association between day-by-day BPV and ambulatory BPV, which is especially distinguished between diurnal and nocturnal BPV, in type 2 diabetes patients. Day-by-day and ambulatory BPV were assessed in 30 type 2 diabetes patients (aged 54±15 years; 87% men; glycated hemoglobin: 9.1±1.9%) in inpatient settings. Day-by-day systolic BPV was correlated significantly with diurnal systolic BPV (r=0.426, P=0.019), but not nocturnal systolic BPV (r=0.175, P=0.354). Multiple regression analysis showed that diurnal systolic BPV and diurnal mean systolic blood pressure were associated independently with day-by-day systolic BPV. With respect to type 2 diabetes, these findings suggest that day-by-day BPV is reflected in diurnal BPV rather than nocturnal BPV.

Integrated cardiovascular/respiratory control in type 1 diabetes evidences functional imbalance: Possible role of hypoxia

BACKGROUND

Cardiovascular (baroreflex) and respiratory (chemoreflex) control mechanisms were studied separately in diabetes, but their reciprocal interaction (well known for diseases like heart failure) had never been comprehensively assessed. We hypothesized that prevalent autonomic neuropathy would depress both reflexes, whereas prevalent autonomic imbalance through sympathetic activation would depress the baroreflex but enhance the chemoreflexes.

METHODS

In 46 type-1 diabetic subjects (7.0±0.9year duration) and 103 age-matched controls we measured the baroreflex (average of 7 methods), and the chemoreflexes, (hypercapnic: ventilation/carbon dioxide slope during hyperoxic progressive hypercapnia; hypoxic: ventilation/oxygen saturation slope during normocapnic progressive hypoxia). Autonomic dysfunction was evaluated by cardiovascular reflex tests.

RESULTS

Resting oxygen saturation and baroreflex sensitivity were reduced in the diabetic group, whereas the hypercapnic chemoreflex was significantly increased in the entire diabetic group. Despite lower oxygen saturation the hypoxic chemoreflex showed a trend toward a depression in the diabetic group.

CONCLUSION

Cardio-respiratory control imbalance is a common finding in early type 1 diabetes. A reduced sensitivity to hypoxia seems a primary factor leading to reflex sympathetic activation (enhanced hypercapnic chemoreflex and baroreflex depression), hence suggesting a functional origin of cardio-respiratory control imbalance in initial diabetes.

High blood pressure variability predicts 30-day mortality but not 1-year mortality in hospitalized elderly patients

BACKGROUND

The association of blood pressure (BP) variability (BPV) in hospitalized patients, which represents day-to-day variability, with mortality has been extensively reported in patients with stroke, but poorly defined for other medical conditions.

AIM AND METHOD

To assess the association of day-to-day blood pressure variability in hospitalized patients, 10 BP measurements were obtained in individuals ≥75 years old hospitalized in a geriatric ward. Day-to-day BPV, measured 3 times a day, was calculated in each patient as the coefficient of variation of systolic BP. Patients were stratified by quartiles of coefficient of variation of systolic BP, and 30-day and 1-year mortality data were compared between those in the highest versus the lowest (reference) group.

RESULTS

Overall, 469 patients were included in the final analysis. Mean coefficient of variation of systolic BP was 12.1%. 30-day mortality and 1-year mortality occurred in 29/469 (6.2%) and 95/469 (20.2%) individuals respectively. Patients in the highest quartile of BPV were at a significantly higher risk for 30-day mortality (HR =4.12, CI 1.12-15.10) but not for 1-year mortality compared with the lowest BPV quartile (HR =1.61, CI 0.81-3.23).

CONCLUSIONS

Day-to-day BPV is associated with 30-day, but not with 1-year mortality in hospitalized elderly patients.

Intermittent hypoxia as a means to improve aerobic capacity in type 2 diabetes

Physical inactivity and a low maximal aerobic capacity (VO_2max) strongly predict morbidity and mortality in patients with type 2 diabetes (T2D). Patients with T2D have a reduced VO_2max when compared with healthy individuals of similar age, weight, and physical activity levels, and this lower aerobic capacity is usually attributed to a reduced oxygen delivery to the working muscles. The oxygen carrying capacity of the blood, as well as increases in cardiac output and blood flow, contribute to the delivery of oxygen to the active muscles during exercise. Hemoglobin mass (Hb mass), a key determinant of oxygen carrying capacity, is suggested to be reduced in patients with T2D following the observation of a lower blood volume (BV) in combination with normal hematocrit levels in this population. Therefore, a lower Hb mass, in addition to a reported lower BV and impaired cardiovascular response to exercise, likely contributes to the reduced oxygen delivery and VO_2max in patients with T2D. While exercise training increases Hb mass, BV, and consequently VO_2max, the majority of patients with T2D are not physically active, highlighting the need for alternative methods to improve VO_2max in this population. Exposure to hypoxia triggers the release of erythropoietin, the hormone regulating red blood cell production, which increases Hb mass and consequently BV. Exposure to mild intermittent hypoxia (IH), characterized by few and short episodes of hypoxia at a fraction of inspired oxygen ranging between 10 and 14% interspersed with cycles of normoxia, increased red blood cell volume, Hb mass, and plasma volume in patients with coronary artery disease or chronic obstructive pulmonary disease, which resulted in an improved VO_2max in both populations. We hypothesize that 12 exposures to mild IH over a period of 4weeks will increase Hb mass, BV, cardiac function, and VO_2max in patients with T2D. Therefore, exposures to mild IH may increase oxygen delivery and VO_2max without the need to perform exercise in patients with T2D.

Can coefficient of variation of time-domain analysis be valuable for detecting cardiovascular autonomic neuropathy in young patients with type 1 diabetes: a case control study

Background

Cardiovascular autonomic neuropathy (CAN) increases morbidity and mortality in diabetes through association with a high risk of cardiac arrhythmias and sudden death, possibly related to silent myocardial ischemia. During the sub-clinical stage, CAN can be detected through reduction in heart rate variability (HRV). The aim of our study was to estimate if the time and frequency-domain analysis can be valuable for detecting CAN in young patients with type 1 diabetes mellitus (T1DM).

Methods

For this case control study of evaluation of cardiovascular autonomic function the 15–25 years age group of patients with duration of T1DM more than 9 years (n = 208, 89 males and 119 females) were selected. 67 patients with confirmed CAN were assigned to the “case group” and 141 patients without CAN served as a control group, the duration of T1DM was similar (15.07 ± 4.89 years vs.13.66 ± 4.02 years; p = 0.06) in both groups. Cardiovascular autonomic reflex tests and time and frequency domains analysis of HRV were performed for all subjects.

Results

Time domain measures were significantly lower in CAN group compared with control (p < 0.05). R-R max / R-R min ratio and coefficient of variation (CV) were the lowest during deep breathing among T1DM patients with CAN. Receivers operating characteristic (ROC) curves were constructed to compare the accuracies of the parameters of time-domain analysis for diagnosing CAN. We estimated a more reliable cut-off value of parameters of time-domain. The CV values in supine position <1.65, reflected sensitivity 94.3%, specificity 91.5%. The CV values during deep breathing <1.45 reflected sensitivity 97.3%, specificity 96.2%. The CV values in standing position <1.50 reflected sensitivity 96.2%, specificity 93.0%. The most valuable CV was during deep breathing (AUC 0.899). The results of frequency-domain (spectral analysis) analysis showed significant decrease in LF power and LFPA, HF Power and HFPA, total power among subjects with CAN than compared with subjects without CAN (p < 0.05).

Conclusions

Time and frequency domain analysis of HRV permits a more accurate evaluation of cardiovascular autonomic function, providing more information about sympathetic and parasympathetic activity. The coefficient of variation (time-domain analysis) especially during deep breathing could be valuable for detecting CAN.

Sensitive detection of hemodynamic failure during orthostatic stress in patients with diabetic polyneuropathy using a mini laser Doppler blood flowmeter

Autonomic dysfunction in diabetes is serious but often underestimated. The purpose of this study was to evaluate hemodynamics within the important initial phase just after standing, which cannot be evaluated by conventional instruments for orthostatic hypotension. Earlobe blood flow (EBF), which indirectly reflects the blood pressure response on standing, was evaluated using a mini laser Doppler flowmeter during standing from the sitting position in 58 healthy controls and 56 diabetic patients categorized as without (11), mild (27), and advanced diabetic polyneuropathy (18). The response area of the EBF waveform within 30 seconds after standing was calculated. An increased response area indicates poor recovery of EBF. Response area increased significantly with the degree of neuropathy (P < .001 for linear trend). Orthostatic hypotension was detected in two patients in the mild neuropathy group. The present approach may be sensitive and practical for detecting autonomic dysfunction not detected with the conventional orthostatic test.

Integrated Cardio-Respiratory Control: Insight in Diabetes

Autonomic dysfunction is a frequent and relevant complication of diabetes mellitus, as it is associated with increased morbidity and mortality. In addition, it is today considered as predictive of the most severe diabetic complications, like nephropathy and retinopathy. The classical methods of screening are the cardiovascular reflex tests and were originally interpreted as evidence of nerve damage. A more modern approach, based on the integrated control of cardiovascular and respiratory function, reveals that these abnormalities are to a great extent functional, at least in the early stage of the disease, thus suggesting new potential interventions. Therefore, this review aims to go further investigating how the imbalance of the autonomic nervous system is altered and can be influenced in many chronic pathologies through a global view of cardio-respiratory and metabolic interactions and how the same mechanisms are applicable to diabetes.

Sympathetic activity and early mobilization in patients in intensive and intermediate care with severe brain injuries: a preliminary prospective randomized study

Background

Patients who experience severe brain injuries are at risk of secondary brain damage, because of delayed vasospasm and edema. Traditionally, many of these patients are kept on prolonged bed rest in order to maintain adequate cerebral blood flow, especially in the case of subarachnoid hemorrhage. On the other hand, prolonged bed rest carries important morbidity. There may be a clinical benefit in early mobilization and our hypothesis is that early gradual mobilization is safe in these patients. The aim of this study was to observe and quantify the changes in sympathetic activity, mainly related to stress, and blood pressure in gradual postural changes by the verticalization robot (Erigo®) and after training by a lower body ergometer (MOTOmed-letto®), after prolonged bed rest of minimum 7 days.

Methods

Thirty patients with severe neurological injuries were randomized into 3 groups with different protocols of mobilization: Standard, MOTOmed-letto® or Erigo® protocol. We measured plasma catecholamines, metanephrines and blood pressure before, during and after mobilization.

Results

Blood pressure does not show any significant difference between the 3 groups. The analysis of the catecholamines suggests a significant increase in catecholamine production during Standard mobilization with physiotherapists and with MOTOmed-letto® and no changes with Erigo®.

Conclusions

This preliminary prospective randomized study shows that the mobilization of patients with severe brain injuries by means of Erigo® does not increase the production of catecholamines. It means that Erigo® is a well-tolerated method of mobilization and can be considered a safe system of early mobilization of these patients. Further studies are required to validate our conclusions.

Trial registration

The study was registered in the ISRCTN registry with the trial registration number ISRCTN56402432. Date of registration: 08.03.2016. Retrospectively registered.

Elevated HbA1c Levels Are Associated with the Blunted Autonomic Response Assessed by Heart Rate Variability during Blood Volume Reduction

A high glycemic status increases the risk for autonomic dysfunction and cardiovascular failure. The aim of this study was to investigate time-dependent changes in the autonomic response and cardiovascular dynamics and the association between the level of hemoglobin A1c (HbA1c) and autonomic response during blood volume reduction. The study population consisted of 26 preoperative participants who were scheduled for autologous blood donation (200-400 mL of whole blood) for intraoperative or postoperative use. These participants without circulatory, respiratory, or brain disease and diabetes mellitus were grouped according to their HbA1c levels: < 6.5% (n = 18) and ≥ 6.5% (n = 8). We measured blood pressure (BP) and analyzed heart rate variability (HRV) to quantify cardiac autonomic regulation throughout blood donation. During blood volume reduction, which was about 10% of the circulating blood volume, the BP and heart rate varied within normal ranges in both groups. The high-frequency (HF) component, an index of parasympathetic nerve activity, and the ratio of low-frequency (LF) to HF components (LF/HF), an index of sympathetic nerve activity, significantly decreased and increased with the progression of blood volume reduction, respectively, in the HbA1c < 6.5% group. In contrast, in the HbA1c ≥ 6.5% group, the HF component did not significantly change, and the increase in the LF/HF ratio was delayed. Time-dependent changes in HRV were related to blood volume reduction only in the HbA1c < 6.5% group. Thus, elevated HbA1c levels are associated with the decrease in the autonomic response induced by blood volume reduction.

Arterial baroreflex control of sympathetic nerve activity and heart rate in patients with type 2 diabetes

Despite greater blood pressure reactivity to acute cardiovascular stressors and a higher prevalence of hypertension in type 2 diabetes (T2D) patients, limited information is available regarding arterial baroreflex (ABR) control in T2D. We hypothesized that ABR control of muscle sympathetic nerve activity (MSNA) and heart rate (HR) are attenuated in T2D patients. Seventeen T2D patients (50 ± 2 yr; 31 ± 1 kg/m²), 9 weight-matched controls (WM-CON, 46 ± 2 yr; 32 ± 2 kg/m²) and 10 lean controls (Lean-CON, 49 ± 3 yr; 23 ± 1 kg/m²), underwent bolus infusions of sodium nitroprusside (100 μg) followed 60 s later by phenylephrine (150 μg) and weighted linear regression performed. No group differences in overall sympathetic baroreflex gain were observed (T2D: -2.5 ± 0.3 vs. WM-CON: -2.6 ± 0.2 vs. Lean-CON: -2.7 ± 0.4 arbitrary units·beat·mmHg^-1, P > 0.05) or in sympathetic baroreflex gain when derived separately during blood pressure (BP) falls (nitroprusside) and BP rises (phenylephrine). In contrast, overall cardiac baroreflex gain was reduced in T2D patients compared with Lean-CON (T2D: 8.2 ± 1.5 vs. Lean-CON: 15.6 ± 2.9 ms·mmHg^-1, P < 0.05) and also tended to be reduced in WM-CON (9.3 ± 1.9 ms·mmHg^-1) compared with Lean-CON (P = 0.059). Likewise, during BP rises, cardiac baroreflex gain was reduced in T2D patients and weight-matched controls compared with lean controls (P < 0.05), whereas no group differences were found during BP falls (P > 0.05). Sympathetic and cardiac ABR gains were comparable between normotensive and hypertensive T2D patients (P > 0.05). These findings suggest preserved ABR control of MSNA in T2D patients compared with both obese and lean age-matched counterparts, with a selective impairment in ABR HR control in T2D that may be related to obesity.

Comparison of heart rate variability and classic autonomic testing for detection of cardiac autonomic dysfunction in patients with fibromyalgia

AIM

Cardiac autonomic dysfunction (CAD) is frequently found in patients with fibromyalgia (FM). Thus, we evaluated whether heart rate variability (HRV) is superior to the Ewing tests in detecting CAD in FM patients.

METHODS

We studied 35 females with FM and 25 age-matched healthy females. In Ewing tests, results were added to yield an overall score. An abnormal result on deep breathing, the Valsalva maneuver, or orthostatic standing was counted as 1 point. A change in systolic blood pressure (SBP) of > 10 mmHg while standing counted as 1 point, and a change of > 20 mmHg as 2 points. A score of 0 was regarded as no CAD, a score of ≥ 2 as severe CAD and a score of 1 as mild CAD. HRV was measured in two ways: by R-R intervals (time-domain analysis) and by spectral analysis of a series of successive R-R intervals (frequency-domain analysis).

RESULTS

FM patients had significantly lower expiratory/inspiratory (E/I) ratios, lower Valsalva ratios and higher SBP values than healthy controls (P < 0.05, P < 0.05, P < 0.01, respectively). In the frequency domain, very low-frequency and low-frequency bands were also lower in FM patients than controls (both P < 0.05). Based on the discriminant analysis of the Ewing tests, 54.4% of cases were correctly classified. The addition of HRV parameters did not improve the reclassification.

CONCLUSION

HRV does not improve detection of CAD in FM patients over classic autonomic testing.

Cardiovascular Variability Analysis and Baroreflex Estimation in Patients with Type 2 Diabetes in Absence of Any Manifest Neuropathy

Introduction

Indexes derived from spontaneous heart period (HP) and systolic arterial pressure (SAP) fluctuations can detect autonomic dysfunction in individuals with type 2 diabetes mellitus (DM) associated to cardiovascular autonomic neuropathy (CAN) or other neuropathies. It is unknown whether HP and SAP variability indexes are sensitive enough to detect the autonomic dysfunction in DM patients without CAN and other neuropathies.

Methods

We evaluated 68 males aged between 40 and 65 years. The group was composed by DM type 2 DM with no manifest neuropathy (n = 34) and healthy (H) subjects (n = 34). The protocol consisted of 15 minutes of recording of HP and SAP variabilities at rest in supine position (REST) and after active standing (STAND). The HP power in the high frequency band (HF, from 0.15 to 0.5 Hz), the SAP power in the low frequency band (LF, from 0.04 to 0.15 Hz) and BRS estimated via spectral approach and sequence method were computed.

Results

The HF power of HP was lower in DM patients than in H subjects, while the two groups exhibited comparable HF power of HP during STAND. The LF power of SAP was similar in DM and H groups at REST and increased during STAND in both groups. BRSs estimated in the HF band and via baroreflex sequence method were lower in DM than in H and they decreased further during STAND in both populations.

Conclusion

Results suggest that vagal control of heart rate and cardiac baroreflex control was impaired in type 2 DM, while sympathetic control directed to vessels, sympathetic and baroreflex response to STAND were preserved. Cardiovascular variability indexes are sensitive enough to typify the early, peculiar signs of autonomic dysfunction in type-2 DM patients well before CAN becomes manifest.

Effect of One-Week Salt Restriction on Blood Pressure Variability in Hypertensive Patients with Type 2 Diabetes

Background

Increased short-term blood pressure (BP) variability on 24-hour ambulatory BP monitoring (ABPM) is known to be a risk factor for cardiovascular events. However, very few studies have evaluated the effect of salt restriction on BP variability particularly in hypertensive patients with type 2 diabetes. This study aimed to investigate the effect of salt restriction on systolic BP (SBP) variability.

Methods and Results

10 hypertensive patients with type 2 diabetes and not receiving antihypertensive agents were enrolled in the study. After admission, all patients received a salt-restricted diet and appropriate anti-diabetic treatments and were followed up for 7 consecutive days using ABPM. After the 7-day treatment, the median [interquartile range (IQR)] coefficient of variation (CV) for diurnal SBP variability changed from day 1 to day 7–13.0 [10.8 to 16.8] % to 13.3 [9.1 to 18.9] % (P = 0.959)—and the median [IQR] change between days 1 and 7 was -0.3 [-3.2 to 2.9] %. In addition, CV for BP variability and circadian rhythm of BP varied greatly on a day-by-day basis for 7 days, compared to mean BP values. Interestingly, increased SBP variability was associated with greater day-by-day changes in circadian rhythm of BP.

Conclusions

Salt restriction during 7-day hospitalization led to a -0.3 [-3.2 to 2.9] (median [IQR]) % change from baseline in CV for diurnal SBP variability in 10 hypertensive patients with type 2 diabetes not receiving antihypertensive agents.

Trial Registration

UMIN Clinical Trials Registry UMIN000016243

The Neural Baroreflex Pathway in Subjects With Metabolic Syndrome: A Sub-Study of the Paris Prospective Study III

The mechanisms that link metabolic syndrome (MetS) to increased cardiovascular risk are incompletely understood. We examined whether MetS is associated with the neural baroreflex pathway (NBP) and whether any such associations are independent of blood pressure values.This study involved the cross-sectional analysis of data on 2835 subjects aged 50 to 75 years from the Paris Prospective Study 3. The prevalence of MetS was defined according to the American Heart Association/National Heart Blood and Lung Institute definition. NBP values were calculated from the fluctuation of the common carotid distension rate and heart rate using fast Fourier transformation and cross-spectral analysis.The prevalence of MetS was 20.1% in men and 10.4% in women. Compared with controls, subjects with MetS (≥3 components), and those at risk for MetS (1-2 components) had lower NBP (-5.3% and -2.3%, respectively) and higher carotid stiffness (+13.5% and +6.8%, respectively). The negative association between MetS components and NBP was confirmed, even after adjustment for age, sex, and carotid stiffness. After stratification for blood pressure (BP) levels, NBP was reduced only in MetS subjects and those at risk with high BP. The NBP was positively associated with carotid stiffness in controls and subjects at risk for MetS. This association was lost in subjects with MetS, regardless of BP levels.Subjects with MetS had reduced NBP values. The role of BP is fundamental in the reduction of NBP. The mechanisms that link carotid stiffness and NBP are inactive in subjects with MetS, independent of BP levels.