Cardiovascular Autonomic Dysfunction in Chronic Kidney Disease: a Comprehensive Review

Impact of sympathetic hyperactivity induced by brain microglial activation on organ damage in sepsis with chronic kidney disease

BACKGROUND

Sympathetic nerve activity (SNA) plays a central role in the pathogenesis of several diseases such as sepsis and chronic kidney disease (CKD). Activation of microglia in the paraventricular nucleus of the hypothalamus (PVN) has been implicated in SNA. The mechanisms responsible for the adverse prognosis observed in sepsis associated with CKD remain to be determined. Therefore, we aimed to clarify the impact of increased SNA resulting from microglial activation on hemodynamics and organ damage in sepsis associated with CKD.

METHODS AND RESULTS

In protocol 1, male Sprague-Dawley rats underwent either nephrectomy (Nx) or sham surgery followed by cecal ligation and puncture (CLP) or sham surgery. After CLP, Nx-CLP rats exhibited decreased blood pressure, increased heart rate, elevated serum creatinine and bilirubin levels, and decreased platelet count compared to Nx-Sham rats. Heart rate variability analysis revealed an increased low to high frequency (LF/HF) ratio in Nx-CLP rats, indicating increased SNA. Nx-CLP rats also had higher creatinine and bilirubin levels and lower platelet counts than sham-CLP rats after CLP. In protocol 2, Nx-CLP rats were divided into two subgroups: one received minocycline, an inhibitor of microglial activation, while the other received artificial cerebrospinal fluid (CSF) intracerebroventricularly via an osmotic minipump. The minocycline-treated group (Nx-mino-CLP) showed attenuated hypotensive and increased heart rate responses compared to the CSF-treated group (Nx-CSF-CLP), and the LF/HF ratio was also decreased. Echocardiography showed larger left ventricular dimensions and inferior vena cava in the Nx-mino-CLP group. In addition, creatinine and bilirubin levels were lower and platelet counts were higher in the Nx-mino-CLP group compared to the Nx-CSF-CLP group.

CONCLUSIONS

In septic rats with concomitant CKD, SNA was significantly enhanced and organ dysfunction was increased. It has been suggested that the mechanism of exacerbated organ dysfunction in these models may involve abnormal systemic hemodynamics, possibly triggered by activation of the central sympathetic nervous system through activation of microglia in the PVN.

A cross-sectional study on the impact of hemodialysis duration on retinal nerve fiber layer thinning in hemodialysis patients

This study aimed to investigate the relationship between hemodialysis duration (HDD) and retinal nerve fiber layer (RNFL) thickness. A total of 60 patients receiving maintenance hemodialysis and 67 healthy controls were analyzed. Spectral domain optical coherence tomography (SD-OCT) was employed to measure annular RNFL thicknesses. The hemodialysis group exhibited reduced temporal and inferior RNFL thicknesses relative to the control group. In hemodialysis patients, the inferior RNFL thickness was negatively correlated with HDD and positively correlated with intraocular pressure (IOP). Moreover, IOP was positively correlated with HDD. Mediation analysis showed that the negative correlation between HDD and inferior RNFL thickness was mediated by IOP. In conclusion, hemodialysis leads to temporal and inferior RNFL thinning, and the thickness reduction is proportional to hemodialysis duration. However, such changes are not induced by an increase in IOP.

The Clinical Significance and Application of Heart Rate Variability in Dialysis Patients: A Narrative Review

Autonomic nervous system (ANS) dysfunction is prevalent in end-stage kidney disease (ESKD) patients, carrying significant risks for morbidity and mortality. Heart rate variability (HRV) is a simple and non-invasive method to evaluate ANS functions and predict prognoses in specific patient populations. Since there is a lack of a clear understanding of the clinical significance of HRV in predicting prognoses in ESKD patients, an updated review on this topic is urgently warranted. The clinical significance of HRV in dialysis patients includes its associations with metabolic syndrome, nutritional status, intradialytic hypotension, vascular access failure, major adverse cardiovascular events, and mortality. These findings underscore the essential role of the autonomic reserve, which might denote the elevation of ANS activity as a response to external stimulus. Patients with a higher level of sympathetic activity at the resting stage, but who are unable to adequately elevate their sympathetic activity under stress might be susceptible to a worse outcome in critical circumstances. Further applications of HRV include HRV biofeedback, risk classification, and real-time HRV monitoring. Overall, HRV is an optimal tool for predicting prognoses in dialysis patients. Further study is encouraged in order to gain a clearer understanding of the clinical significance and application of HRV, and thereby enhance the care of ESKD patients.

Resting Heart Rate Independent of Cardiovascular Disease Risk Factors Is Associated With End-Stage Renal Disease: A Cohort Study Based on 476 347 Adults

BACKGROUND

The relationship between resting heart rate (RHR) and the risk of end-stage renal disease (ESRD) among those without cardiovascular disease remains unclear. We aim to establish temporal consistency and elucidate the independent relationship between RHR and the risk of ESRD.

METHODS AND RESULTS

This cohort enrolled participants from 476 347 individuals who had taken part in a screening program from 1996 to 2017. We identified 2504 participants who had ESRD, and the median follow-up was 13 years. RHR was extracted from electrocardiography results, and the study assessed the relationship between RHR and the risk of ESRD using the Cox proportional hazards model. Of the participants, 32.6% had an RHR of 60 to 69 beats per minute (bpm), and 22.2% had an RHR of ≥80 bpm. Participants with an RHR of ≥80 bpm had a higher stage of chronic kidney disease, lower estimated glomerular filtration rate, and more proteinuria than those with an RHR of 60 to 69 bpm. Participants with an RHR of 80 to 89 and ≥90 bpm had a 24% (hazard ratio [HR], 1.24 [95% CI, 1.09-1.42]) and 64% (HR, 1.64 [95% CI, 1.42-1.90]) higher risk of ESRD, respectively. The risk of ESRD remained significantly elevated (HR, 1.32 [95% CI, 1.10-1.58] per 10-beat increase from 60 bpm) after excluding participants who smoked; had hypertension, diabetes, or hyperlipidemia; or were overweight.

CONCLUSIONS

An RHR of ≥80 bpm is significantly associated with an increased risk of ESRD. These results suggest that RHR may serve as a risk factor for kidney disease in individuals without established cardiovascular disease risk factors.

Association Between Arterial Stiffness and Measures of Autonomic Dysfunction in People With Chronic Kidney Disease

Background

Autonomic nervous system (ANS) dysfunction and vascular stiffness increase cardiovascular risk in people with chronic kidney disease (CKD). Chronic elevations in sympathetic activity can lead to increased arterial stiffness; however, the relationship between these variables is unknown in CKD.

Objective

To explore the association between measures of autonomic function and arterial stiffness in patients with moderate-to-severe CKD.

Methods

This study was a prespecified secondary analysis of a randomized controlled trial. This included the following measures: 24-hour ambulatory blood pressure (BP), carotid-femoral and carotid-radial pulse wave velocity (PWV), and postexercise heart rate recovery (HRR). We used mixed effect linear regression models with Bayesian information criteria (BIC) to assess the contribution of ANS measurements.

Results

Forty-four patients were included in the analysis. Mean carotid-femoral and carotid-radial PWV were 7.12 m/s (95% CI 6.13, 8.12) and 8.51 m/s (7.90, 9.11), respectively. Mean systolic dipping, calculated as percentage change in mean systolic readings from day to night, was 10.0% (95% CI 7.79, 12.18). Systolic dipping was independently associated with carotid-radial PWV, MD -0.09 m/s (95% CI -0.15, -0.02) and had the lowest BIC.

Conclusions

Systolic dipping was associated with carotid-radial PWV in people with moderate-to-severe CKD; however, there was no association with carotid-femoral PWV. Systolic dipping may be a feasible surrogate of ANS function, as the association with carotid-radial PWV was consistent with the minimal clinically important difference (MCID). Future studies are needed to define the relationship between ANS function, arterial stiffness, and CV events over time in people with CKD.

Does Renal Denervation a Reasonable Treatment Option in Hemodialysis-Dependent Patient with Resistant Hypertension? A Narrative Review

PURPOSE OF REVIEW

This narrative review aims to assess the pathophysiology, diagnosis, and treatment of resistant hypertension (RH) in end-stage kidney disease (ESKD) patients on dialysis, with a specific focus on the effect of renal denervation (RDN) on short-term and long-term blood pressure (BP) control. Additionally, we share our experience with the use of RDN in an amyloidotic patient undergoing hemodialysis with RH.

RECENT FINDINGS

High BP, an important modifiable cardiovascular risk factor, is often observed in patients in ESKD, despite the administration of multiple antihypertensive medications. However, in clinical practice, it remains challenging to identify RH patients on dialysis treatment because of the absence of specific definition for RH in this context. Moreover, the use of invasive approaches, such as RDN, to treat RH is limited by the exclusion of patients with reduced renal function (eGFR < 45 mL/min/1.73 m3) in the clinical trials. Nevertheless, recent studies have reported encouraging results regarding the effectiveness of RDN in stage 3 and 4 chronic kidney disease (CKD) and ESKD patients on dialysis, with reductions in BP of nearly up to 10 mmhg. Although multiple underlying pathophysiological mechanisms contribute to RH, the overactivation of the sympathetic nervous system in ESKD patients on dialysis plays a crucial role. The diagnosis of RH requires both confirmation of adherence to antihypertensive therapy and the presence of uncontrolled BP values by ambulatory BP monitoring or home BP monitoring. Treatment involves a combination of nonpharmacological approaches (such as dry weight reduction, sodium restriction, dialysate sodium concentration reduction, and exercise) and pharmacological treatments. A promising approach for managing of RH is based on catheter-based RDN, through radiofrequency, ultrasound, or alcohol infusion, directly targeting on sympathetic overactivity.

Autonomic Nervous System Dysfunction in Peritoneal Dialysis Patients: An Underrecognized Cardiovascular Risk Factor?

BACKGROUND

In patients with end-stage kidney disease (ESKD) receiving peritoneal dialysis (PD), cardiovascular events represent the predominant cause of morbidity and mortality, with cardiac arrhythmias and sudden death being the leading causes of death in this population. Autonomic nervous system (ANS) dysfunction is listed among the non-traditional risk factors accounting for the observed high cardiovascular burden, with a plethora of complex and not yet fully understood pathophysiologic mechanisms being involved.

SUMMARY

In recent years, preliminary studies have investigated and confirmed the presence of ANS dysfunction in PD patients, while relevant results from cohort studies have linked ANS dysfunction with adverse clinical outcomes in these patients. In light of these findings, ANS dysfunction has been recently receiving wider consideration as an independent cardiovascular risk factor in PD patients. The aim of this review was to describe the mechanisms involved in the pathogenesis of ANS dysfunction in ESKD and particularly PD patients and to summarize the existing studies evaluating ANS dysfunction in PD patients.

KEY MESSAGES

ANS dysfunction in PD patients is related to multiple complex mechanisms that impair the balance between SNS/PNS, and this disruption represents a crucial intermediator of cardiovascular morbidity and mortality in this population.

Urinary epidermal growth factor levels correlate with cardiovascular autonomic neuropathy indices in adults with type 1 diabetes

The relationship between urinary endothelial growth factor (uEGF) and cardiovascular autonomic neuropathy (CAN) in adults with type 1 diabetes was evaluated. uEGF levels at baseline and standardized CAN measures were collected at baseline and annually for 3 years for type 1 diabetes adults. Linear regression analysis and linear mixed effects model were used for analysis. In this cohort (n = 44, 59% women, mean ± standard deviation age 34 ± 13 years and diabetes duration 14 ± 6 years), lower baseline uEGF levels correlated with lower baseline expiration : inspiration ratios (P = 0.03) and greater annual declines in Valsalva ratios (P = 0.02) in the unadjusted model, and correlated with lower low-frequency power : high-frequency power ratios (P = 0.01) and greater annual changes in low-frequency power : high-frequency power ratios (P = 0.01) after adjustment for age, sex, body mass index, and hemoglobin A1C. In conclusion, baseline uEGF levels correlate to baseline and longitudinal changes in CAN indices. A large-scale, long-term study is needed to validate uEGF as a reliable CAN biomarker.

Heart rate variability at rest and in response to stress: Comparative study between hemodialysis and peritoneal dialysis patients

Cardiac arrhythmias and sudden death are the leading causes of mortality in end-stage kidney disease (ESKD). Autonomic nervous system (ANS) dysfunction contributes to this arrhythmogenic background. This study compared heart rate variability (HRV) indices between hemodialysis (HD) and peritoneal dialysis (PD) patients, both at rest and in response to mental and physical stimulation maneuvers. Thirty-four HD and 34 PD patients matched for age, sex, and dialysis vintage, and 17 age- and sex-matched controls were studied. ANS function was examined by linear and non-linear HRV indices. Heart rate was recorded continuously (Finometer-PRO) at rest and during ANS maneuvers (orthostatic, mental-arithmetic, sit-to-stand, handgrip exercise tests). At rest, no significant differences between HD and PD were observed in HRV (root mean square of successive differences [RMSSD]: HD = 57.1 ± 81.1 vs PD = 69.6 ± 113.4 ms; P = 0.792), except for detrended fluctuation analysis (DFA-α1) (HD = 0.87 ± 0.40 vs PD = 0.70 ± 0.20; P = 0.047). DFA-α1 was significantly lower in PD than controls (1.00 ± 0.33; P < 0.05). All HRV indices during the mental-arithmetic test (RMSSD: HD = 128.2 ± 346.0 vs PD = 87.5 ± 150.0 ms; P = 0.893) and the physical stress tests were similar between HD and PD. The standard deviation along the line-of-identity (SD2)/the standard deviation perpendicular to the line-of-identity (SD1) ratio during mental-arithmetic was marginally lower in HD and significantly lower in PD than controls (PD = 1.31 ± 0.47 vs controls = 1.79 ± 0.64; P < 0.05). Both dialysis groups presented similar patterns in HRV responses during orthostatic and handgrip exercise tests. After the sit-to-stand, RMSSD, SD1, SD2, and DFA-α2 were higher compared to rest only in HD (RMSSD = 57.1 ± 81.1 vs 126.7 ± 185.7 ms; P = 0.028), suggesting a greater difficulty of HD patients in recovering normal ANS function in response to physical stress. In conclusion, HRV indices at rest and after mental and physical stimulation did not differ between HD and PD; however, the ANS responses following the sit-to-stand test were more impaired in HD. These findings suggest that ANS dysfunction is not largely affected by dialysis modality, but small differences in normal ANS recovery may exist.

Effects of Acute Exercise on Cardiac Autonomic Response and Recovery in Non-Dialysis Chronic Kidney Disease Patients

Purpose: Heart rate variability (HRV) has gained acceptance as a key marker of cardiovascular health. We compared HRV responses after continuous moderate-intensity exercise (CMIE) and high-intensity interval exercise (HIIE) matched for intensity and duration in individuals with midspectrum chronic kidney disease (CKD). Methods: Twenty men and women (age 62.0 ± 10 yrs.) diagnosed with CKD stages G3a and G3b participated in a 2 (condition) x 4 (time point) repeated cross-over measures design study. HRV time-domain indices were based on the standard deviation of all NN intervals (SDNN) and the square root of the mean of the sum of the squares of differences between adjacent NN intervals (RMSSD) and frequency domain. High-frequency (HF), low-frequency (LF), total power (TP) were examined. CMIE consisted of treadmill walking for 30 minutes at a 2% incline and speed corresponding to 60%-65% of reserve volume of oxygen (VO2R). HIIE included five intervals of 3 minutes at 90% of VO2R and 2 minutes at 20% VO2R intervals. Conditions were designed to be of the same average intensity (60% to 65% of VO2R) and caloric expenditure (~144 kcal). Results: Immediately following exercise SDNN, RMSSD, HF, LF, and TP were significantly lower compared to before exercise (p <.05). HRV responses were not different between conditions and conditions X time (p >.05). Conclusions: Thirty minutes of either CMIE or HIIE decreased HRV indices, pointing to an autonomic imbalance favoring vagal mediation. HRV's responses regarding HIIE were no different from CMIE, therefore, from an autonomic function point of view this similarity may be useful for CKD exercise prescription and programming.

Home-Based Exercise Training and Cardiac Autonomic Neuropathy in Kidney Transplant Recipients with Type-II Diabetes Mellitus

This randomized clinical trial aimed to examine the effects of a 6-month home-based, combined exercise training program on Cardiac Autonomic Neuropathy (CAN) in kidney transplant recipients (KTRs) with diabetes. Twenty-five KTRs (19 men (76.0%), with a mean age of 54.4 ± 11.3 years old, CAN and type II Diabetes Mellitus (DM-II)), were randomly assigned into two groups: A (n1 = 13 KTRs), who underwent a home-based exercise training program for 6 months, and B (n2 = 12 KTRs), who were assessed at the end of the study. A cardiopulmonary exercise testing (CPET), sit-to-stand test in 30 s (30-s STS), isokinetic muscle strength dynamometry, and 24-h electrocardiographic monitoring were applied to all participants, both at the baseline and at the end of the clinical trial. At first, there were no statistically significant differences between groups. After 6 months, group A showed higher values in exercise time by 8.7% (p = 0.02), VO2peak by 7.3% (p < 0.05), 30-s STS by 12.0% (p < 0.05), upper limb strength by 46.1% (p < 0.05), and lower limb strength by 24.6% (p = 0.02), respectively, compared to the B group. Furthermore, inter-group changes at the end of the 6-month study indicated that group A statistically increased the standard deviation of R-R intervals (SDNN) by 30.3% (p = 0.01), root mean square of successive differences between normal heartbeats (rMSSD) by 32.0% (p = 0.03), number of pairs of successive NN (R-R) intervals that differ by more than 50 ms (pNN50) by 29.0% (p = 0.04), high frequency (HF (ms2)) by 21.6% (p < 0.05), HF (n.u.) by 48.5% (p = 0.01), and turbulence slope (TS) by 22.5% (p = 0.02), and decreased the low frequency (LF (ms2)) by 13.2% (p = 0.01), LF (n.u.) by 24.9% (p = 0.04), and LF/HF ratio by 24% (p = 0.01), compared to group B. Linear regression analysis after the 6-month study showed that there was a strong positive correlation between VO2peak and SDNN (r = 0.701, p < 0.05) in group A. Moreover, multiple regression analysis showed that KTRs' participation in the exercise program showed favorable modifications to sympathovagal balance and aerobic capacity, as measured with SDNN and VO2peak, respectively. To summarize, diabetic KTRs' cardiac autonomic function and functional capacity can be improved after a home-based long-term exercise training program.

Nine Months of Hybrid Intradialytic Exercise Training Improves Ejection Fraction and Cardiac Autonomic Nervous System Activity

Cardiovascular disease is the most common cause of death in hemodialysis (HD) patients. Intradialytic aerobic exercise training has a beneficial effect on cardiovascular system function and reduces mortality in HD patients. However, the impact of other forms of exercise on the cardiovascular system, such as hybrid exercise, is not clear. Briefly, hybrid exercise combines aerobic and strength training in the same session. The present study examined whether hybrid intradialytic exercise has long-term benefits on left ventricular function and structure and the autonomous nervous system in HD patients. In this single-group design, efficacy-based intervention, twelve stable HD patients (10M/2F, 56 ± 19 years) participated in a nine-month-long hybrid intradialytic training program. Both echocardiographic assessments of left ventricular function and structure and heart rate variability (HRV) were assessed pre, during and after the end of the HD session at baseline and after the nine-month intervention. Ejection Fraction (EF), both assessed before and at the end of the HD session, appeared to be significantly improved after the intervention period compared to the baseline values (48.7 ± 11.1 vs. 58.8 ± 6.5, p = 0.046 and 50.0 ± 13.4 vs. 56.1 ± 3.4, p = 0.054 respectively). Regarding HRV assessment, hybrid exercise training increased LF and decreased HF (p < 0.05). Both conventional Doppler and tissue Doppler imaging indices of diastolic function did not change after the intervention period (p > 0.05). In conclusion, long-term intradialytic hybrid exercise training was an effective non-pharmacological approach to improving EF and the cardiac autonomous nervous system in HD patients. Such exercise training programs could be incorporated into HD units to improve the patients’ cardiovascular health.

Predictive value of heart rate variability on long-term mortality in end-stage kidney disease on hemodialysis

Autonomic disturbance is common in end-stage kidney disease (ESKD). Heart rate variability (HRV) is a useful tool to assess autonomic function. We aimed to evaluate the predictive value of HRV on all-cause mortality and explore the proper timing of HRV assessment. This prospective cohort study enrolled 163 ESKD on hemodialysis patients from April-December 2018. HRV measurements were recorded ten minutes before hemodialysis, four hours during hemodialysis, and ten minutes after hemodialysis. Clinical parameters and all-cause mortality were recorded. Cox-proportional hazard regression was used for statistical analysis. After a median follow up of 40 months, 37 (22.7%) patients died. Post-dialysis HRV parameters including higher very low frequency (VLF) (hazard ratio [HR], 0.881; 95%confidence interval [CI], 0.828-0.937; p<0.001), higher normalized low frequency (nLF) (HR, 0.950; 95%CI, 0.917-0.984; p = 0.005) and higher LF/HF ratio (HR, 0.232; 95%CI, 0.087-0.619; p = 0.004) were the independent predictors associated with lower risk for all-cause mortality. Higher post-dialysis normalized high frequency (nHF) increased risk of mortality (HR, 1.051; 95%CI, 1.015-1.089; p = 0.005). HRV parameters at pre-dialysis and during dialysis were not predictive for all-cause mortality. The area under receiver operating characteristic curve (AuROC) of VLF for survival was highest compared to other HRV parameters at post-dialysis period (AuROC 0.71; 95% CI; 0.62-0.79; p<0.001). In conclusion, post-dialysis HRV parameters predicted all-cause mortaliy in ESKD. VLF measured at post-dialysis exhibited best predictive value for survival in chronic hemodialysis patients.

Electrochemical skin conductance and heart rate variability in patients with non-dialysis chronic kidney disease

BACKGROUND

Chronic kidney disease (CKD) is very common now and associates with high overall and cardiovascular mortality. Numerous studies have reported that Heart rate variability (HRV) could also be used to detect cardiovascular autonomic dysfunction (CAD). We investigated the association of electrochemical skin conductance (ESC) of EZSCAN results with HRV in non-dialysis CKD patients.

METHODS

In a cross-sectional study, we enrolled 248 prevalent non-dialysis CKD patients. Patients underwent a 24-h Holter (CB-2302-A, Bio Instrument, China). A time domain analysis of HRV was performed, and the following parameters were obtained: SDNN, SDANN, rMSSD, pNN50. EZSCAN device (Impeto Medical, Paris, France) measures ESC values of each participants. Mean global skin conductance computed as 0.5 * (reflecting (right + left hand)/2 + (right and left foot)/2). Log transforms data into a normal distribution for statistical analysis.

RESULTS

There were 142 males and 106 females included in the present study. Patients' age was 56.6±17.08 years. Logarithm(Log) (global ESC) was independently predicted by age (P<0.01), hypertension history, estimated Glomerular filtration rate (eGFR) and log SDNN (P<0.05). While log SDANN, rMSSD and pNN50 were not independent predictors for log (global ESC).

CONCLUSION

Increased global ESC significantly associated with elevated HRV, specifically SDNN in non-dialysis CKD patients. This suggested that global ESC may appear to be an important predictor of CAD, and even could be used as a cardiovascular risk factor in non-dialysis CKD patients.

Non-dipping pulse rate and chronic changes of the kidney in patients with chronic kidney disease

Introduction

An insufficient decrease in nocturnal pulse rate (PR), non-dipping PR, reflects autonomic imbalance and is associated with cardiovascular events and all-cause mortality. We aimed to investigate the clinical and microanatomical structural findings associated with the non-dipping PR status in patients with chronic kidney disease (CKD).

Methods

This cross-sectional study included 135 patients who underwent ambulatory blood pressure monitoring and kidney biopsy concurrently at our institution between 2016 and 2019. Non-dipping PR status was defined as (daytime PR-nighttime PR)/daytime PR <0.1. We compared clinical parameters and microstructural changes in the kidney between patients with and without non-dipping PR, including 24 h proteinuria, glomerular volume, and Mayo Clinic/Renal Pathology Society Chronicity Score.

Results

The median age was 51 years (interquartile range: 35-63), 54% of which were male, and the median estimated glomerular filtration rate was 53.0 (30.0-75.0) mL/min/1.73 m². Non-dipping PR status was observed in 39 patients. Patients with non-dipping PR were older and had worse kidney function, higher blood pressure, greater prevalence of dyslipidemia, lower hemoglobin levels, and a larger amount of urinary protein excretion than patients with dipping PR. Patients with non-dipping PR had more severe glomerulosclerosis, interstitial fibrosis, tubular atrophy, and arteriosclerosis. In the multivariable analysis, the severe chronic changes of the kidney were associated with non-dipping PR status after adjusting for age, sex, and other clinical parameters (odds ratio = 20.8; 95% confidence interval, 2.82-153; P = 0.003).

Conclusion

This study is the first to indicate that non-dipping PR is significantly associated with chronic microanatomical changes in the kidneys of patients with CKD.

Baroreflex Sensitivity Assessment Using the Sequence Method with Delayed Signals in End-Stage Renal Disease Patients

Impaired baroreflex sensitivity (BRS) is partially responsible for erratic blood pressure fluctuations in End-Stage Renal Disease (ESRD) patients on chronic hemodialysis (HD), which is related to autonomic nervous dysfunction. The sequence method with delayed signals allows for the measurement of BRS in a non-invasive fashion and the investigation of alterations in this physiological feedback system that maintains BP within healthy limits. Our objective was to evaluate the modified delayed signals in the sequence method for BRS assessment in ESRD patients without pharmacological antihypertensive treatment and compare them with those of healthy subjects. We recruited 22 healthy volunteers and 18 patients with ESRD. We recorded continuous BP to obtain a 15-min time series of systolic blood pressure and interbeat intervals during the supine position (SP) and active standing (AS) position. The time series with delays from 0 to 5 heartbeats were used to calculate the BRS, number of data points, number of sequences, and estimation error. The BRS from the ESRD patients was smaller than in healthy subjects (p < 0.05). The BRS estimation with the delayed sequences also increased the number of data points and sequences and decreased the estimation error compared to the original time series. The modified sequence method with delayed signals may be useful for the measurement of baroreflex sensitivity in ESRD patients with a shorter recording time and maintaining an estimation error below 0.01 in both the supine and active standing positions. With this framework, it was corroborated that baroreflex sensitivity in ESRD is decreased when compared with healthy subjects.

Joint effect of blood pressure and glycemic variation on the risk of cardiovascular morbidity and mortality in persons with type 2 diabetes

OBJECTIVE

Few studies have explored the association of visit-to-visit variation in blood pressure (BP) and glycemic factors with cardiovascular disease (CVD) morbidity and mortality. This study aimed to examine the independent and joint effect of visit-to-visit BP and glycemic variation on CVD morbidity and mortality in persons with T2DM.

METHODS

The present study consisted of two retrospective cohort studies. The Taiwan Diabetes Study was based on a database of the National Diabetes Care Management Program (DCMP) and linked with cardiovascular morbidity incidence. The Taichung Diabetes Study was based on the DCMP database of a medical center, which can be linked with the National Death Registry dataset. The outcomes were analyzed by using Cox's proportional hazard models.

RESULTS

A total of 13,280 and 10,894 persons with T2DM in Taiwan and Taichung Diabetes Study, respectively, were included. SBP-CV, FPG-CV, and HbA1c-CV were significant predictors of stroke, CVD event or death, all-cause mortality, and expanded CVD mortality, whereas DBP-CV was a significant predictor of all-cause mortality and expanded and non-expanded CVD mortality. The joint effect of SBP, FPG, and HbA1c predicted the incidence of stroke and CVD event or death with increased risks of 16 %-35 %. In addition, the joint effect of SBP, DBP, FPG, and HbA1c was associated with all-cause and expanded CVD mortality with increased risks of 29 %-81 %.

CONCLUSIONS

The joint effect of BP and glucose variation improved the prediction of cardiovascular morbidity and mortality. Moreover, simultaneous measurement of visit-to-visit BP and glycemic variation may stratify persons with cardiovascular risks and may be regarded as important therapeutic goals in the care of T2DM.

Hypertension in chronic kidney disease: What lies behind the scene

Hypertension is a frequent condition encountered during kidney disease development and a leading cause in its progression. Hallmark factors contributing to hypertension constitute a complexity of events that progress chronic kidney disease (CKD) into end-stage renal disease (ESRD). Multiple crosstalk mechanisms are involved in sustaining the inevitable high blood pressure (BP) state in CKD, and these play an important role in the pathogenesis of increased cardiovascular (CV) events associated with CKD. The present review discusses relevant contributory mechanisms underpinning the promotion of hypertension and their consequent eventuation to renal damage and CV disease. In particular, salt and volume expansion, sympathetic nervous system (SNS) hyperactivity, upregulated renin–angiotensin–aldosterone system (RAAS), oxidative stress, vascular remodeling, endothelial dysfunction, and a range of mediators and signaling molecules which are thought to play a role in this concert of events are emphasized. As the control of high BP via therapeutic interventions can represent the key strategy to not only reduce BP but also the CV burden in kidney disease, evidence for major strategic pathways that can alleviate the progression of hypertensive kidney disease are highlighted. This review provides a particular focus on the impact of RAAS antagonists, renal nerve denervation, baroreflex stimulation, and other modalities affecting BP in the context of CKD, to provide interesting perspectives on the management of hypertensive nephropathy and associated CV comorbidities.

Effects of a Combined Intradialytic Exercise Training Program and Music on Cardiac Autonomic Nervous System Activity in Hemodialysis Patients

This study aimed to examine the effect of an intradialytic exercise program in combination with music on heart rate variability (HRV) indices and functional capacity in patients on maintenance hemodialysis (HD). Methods: Forty HD patients were randomized to four training groups for six months: the combined music and exercise group (Group A), the exercise group (Group B), the music group (Group C), and the control group (Group D). At baseline and after 6 months, all participants underwent both short- (for 30 min) and long- (for 24 h) term measurements of HRV and functional capacity assessment with a 6 min walking test (6MWT). Patients of groups A and C listened to preferred music. Results: Long-term HRV analysis showed that standard deviation of all normal-to-normal RR intervals (SDNN) and the square root of the mean squared differences of successive RR intervals (rMSSD) were significantly higher at the end of the study in groups A (by 13.2% and 47.3%), B (by 15.1% and 50%), and C (by 9.0% and 30.1%), compared to group D (p < 0.05). Values of rMSSD and percentage of RR intervals differing by more than 50 ms from the preceding RR interval (pNN50) were elevated in groups A (by 35.6% and 142.9%), B (by 36.1% and 75%), and C (by 15.2% and 28.6%), compared to baseline measurements (p < 0.05). Also, pNN50 was increased in group A compared to groups B (by 21.4%), C (by 88.9%), and D (by 142.9%) (p < 0.05). Similar results were noted by short-term HRV analysis. Functional capacity was improved at the end of the 6-month study in groups A (by 20.3% and 25.7%) and B (by 15.8% and 21.1%) compared to groups C and D (p < 0.05). Conclusions: Intradialytic exercise combined with music-listening can improve the functional capacity and cardiac autonomic nervous system activity in hemodialysis patients.

Preventing and Managing Falls in Adults With Cardiovascular Disease: A Scientific Statement From the American Heart Association

Falls and fear of falling are a major health issue and associated with high injury rates, high medical care costs, and significant negative impact on quality of life. Adults with cardiovascular disease are at high risk of falling. However, the prevalence and specific risks for falls among adults with cardiovascular disease are not well understood, and falls are likely underestimated in clinical practice. Data from surveys of patient-reported and medical record-based analyses identify falls or risks for falling in 40% to 60% of adults with cardiovascular disease. Increased fall risk is associated with medications, structural heart disease, orthostatic hypotension, and arrhythmias, as well as with abnormal gait and balance, physical frailty, sensory impairment, and environmental hazards. These risks are particularly important among the growing population of older adults with cardiovascular disease. All clinicians who care for patients with cardiovascular disease have the opportunity to recognize falls and to mitigate risks for falling. This scientific statement provides consensus on the interdisciplinary evaluation, prevention, and management of falls among adults with cardiac disease and the management of cardiovascular care when patients are at risk of falling. We outline research that is needed to clarify prevalence and factors associated with falls and to identify interventions that will prevent falls among adults with cardiovascular disease.

Factors Associated with Reduced Heart Rate Variability in the General Japanese Population: The Iwaki Cross-Sectional Research Study

Although many studies have reported factors associated with reduced heart rate variability (HRV) in Western populations, evidence is limited among Asian populations. Therefore, we investigated the factors associated with reduced HRV values in a general Japanese population by measuring HRV among the participants of the Iwaki Health Promotion Project who underwent medical examination in 2019. We performed 90-s HRV measurements in 1065 participants. Of these, we evaluated the coefficient of variation in R–R intervals (CVRR) and standard deviation in R–R intervals (SDNN). Blood was collected under a fasting condition, and investigations of glucose metabolism, lipid metabolism, renal function, liver function, advanced glycation end products, and blood pressure were performed. A multivariate regression analysis of the association between CVRR or SDNN and blood test parameters and blood pressure in 987 participants with adequately completed HRV assessments showed that reduced CVRR or SDNN was associated with higher levels of glycated hemoglobin (HbA1c), glycoalbumin, blood glucose, triglycerides, creatinine, plasma pentosidine, and diastolic blood pressure. In the general Japanese population, higher levels of HbA1c, glycoalbumin, blood glucose, triglycerides, creatinine, plasma pentosidine, and diastolic blood pressure are associated with reduced CVRR or SDNN, which are typical HRV parameters.

Early morning hemodynamic changes and left ventricular hypertrophy and mortality in hemodialysis patients

INTRODUCTION

An exaggeration of the early morning increase in BP, a phenomenon accompanied by a parallel rise in heart rate (HR), is a marker of high cardiovascular risk. The early morning changes in these parameters have not been investigated in the hemodialysis population.

METHODS

In a pilot, single center study including a series of 58 patients we measured the pre-awakening BP and HR surges and the nocturnal dipping of the same parameters as well as other established indicators of autonomic function (weighted 24 h systolic BP and HR variability) and tested their relationship with the left ventricular mass index (LVMI) and with the risk of death over a median follow up of 40 months.

RESULTS

The pre-awakening HR surge (r = - 0.46, P = 0.001) but not the corresponding BP surge (r = - 0.1, P = 0.98) was associated with LVMI and the risk of death [HR (1 unit): 0.89, 95% CI 0.83-0.96, P = 0.001]. The link between the pre-awakening HR surge with these outcome measures was robust and largely independent of established risk factors in the hemodialysis population, including the nocturnal dipping of BP. Weighted 24 h systolic BP and HR variability did not correlate with LVMI (all P > 0.11) nor with the risk of death (P > 0.11) and were also independent of the nocturnal dipping of systolic BP and HR.

CONCLUSION

This pilot study suggests that the low early morning changes in HR, likely reflecting enhanced sympathetic activity, entail a high risk for left ventricular hypertrophy (LVH) and mortality in the hemodialysis population.

Decline in renal function associated with cardiovascular autonomic neuropathy positively coordinated with proteinuria in patients with type 2 diabetes

AIMS/INTRODUCTION

To investigate the association between cardiovascular autonomic neuropathy (CAN) assessed by the coefficient of variation of the R-R interval and the reduction in the estimated glomerular filtration rate (eGFR) in patients with type 2 diabetes.

MATERIALS AND METHODS

This retrospective observational cohort study enrolled type 2 diabetes patients who had their coefficient of variation of the R-R interval measured on an electrocardiogram from January 2005 to December 2018. CAN was defined using the reference coefficient of variation of the R-R interval value based on age and sex. The primary outcome was set as a 40% eGFR decline from baseline. Regression analyses using the Cox proportional hazards model were carried out to evaluate the association.

RESULTS

Of the 831 patients, 118 (14.2%) were diagnosed with CAN. In the analysis of the primary outcome, the median follow-up period was 5.3 years, and 25 (21.2%) patients with CAN and 78 (10.9%) patients without CAN developed a 40% eGFR decline. In the univariate regression analysis, CAN was significantly associated with a 40% eGFR decline (hazard ratio 2.42, 95% confidence interval 1.54-3.80). In the multivariate analysis, CAN remained almost significant after adjusting for the prognostic risk factors for CAN and the decline in the renal function, and an interaction with proteinuria was found. In analyses for the interaction effect between CAN and proteinuria, the presence of CAN synergistically increased the risk of an eGFR decline in patients with macroproteinuria.

CONCLUSIONS

CAN strongly increased the risk of a 40% eGFR decline from baseline, especially in type 2 diabetes patients with macroproteinuria.

Cardiac Autonomic Dysfunction Is Associated With Risk of Diabetic Kidney Disease Progression in Type 2 Diabetes Mellitus

BACKGROUND

Evidence on the relationship between heart rate variability (HRV) and albumin-to-creatinine ratio (ACR) combined with estimated glomerular filtration rate (eGFR) in patients with type 2 diabetes mellitus (T2DM) is rare. Thus, this study aimed to investigate the relationship between heart rate variability and the risk of diabetic kidney disease (DKD) progression in diabetes patients.

METHOD

Overall, 747 T2DM patients who were admitted to the Second Affiliated Hospital of Nanchang University underwent 24-hour dynamic electrocardiograms for HRV analysis. Time-domain HRV measures included mean heart rate, standard deviation of the R-R interval (SDNN), SDNN index, root mean squared difference of successive RR intervals (RMSSD), and percent of adjacent RR intervals with a difference greater than 50 ms (PNN50). Frequency-domain measures included low frequency (LF), very low frequency (VLF), high frequency (HF) components and LF-to-HF ratio. The risk of DKD progression was determined by combining ACR and eGFR and stratified as low risk (Group A), moderately increased risk (Group B), high risk (Group C), and very high risk (Group D) based on the Kidney Disease: Improving Global Outcomes guidelines.

RESULT

There were significant differences in HRV parameters among the four risk groups (SDNN: 113 ms vs 109 ms vs 101 ms vs 81 ms, P<0.01; LF: 240.2 ms² vs 241.1 ms² vs 155.2 ms² vs 141.9 ms², P<0.01; LF-to-HF ratio: 1.70 vs 1.24 vs 1.12 vs 0.93, P<0.01; VLF: 723.7 ms² vs 601.1 ms² vs 446.4 ms² vs 356.3 ms², P<0.01). A very high risk of DKD progression was significantly associated with a lower SDNN (β=-19.5, 95% CI: -30.0 to -10.0, P<0.01), and moderately increased, high, and very high risks were associated with lower LF-to-HF ratio and VLF (P<0.05). Logistic regression analysis showed that group D had a higher risk of reduced SDNN, LF-to-HF ratio, and VLF compared with group A after adjusting for systolic blood pressure, glycated haemoglobin, haemoglobin, high-density lipoprotein cholesterol, and age (odds ratio (95% CI): 0.989 (0. 983-0.996), 0.674 (0.498-0.913), and 0.999 (0.999-1.000), respectively).

CONCLUSION

Cardiac autonomic dysfunction is associated with a risk of DKD progression in adults with T2DM, and reduced heart rate variability increased such risk. Thus, HRV screening may be necessary in patients with T2DM, especially those with high proteinuria.

Role of Heart Rate Variability in Association Between Glomerular Hyperfiltration and All-Cause Mortality

Background

Glomerular hyperfiltration (GHF) is paradoxically associated with increased cardiovascular events in healthy individuals, but the pathogenesis remains unclear. We aim to investigate whether GHF is associated with mortality and whether decreased heart rate variability (HRV) is associated with GHF.

Methods and Results

We retrospectively analyzed 1615 participants (aged 66.1±17.3 years, 61.9% men) without prior cardiovascular events. The glomerular filtration rate was estimated using the Chronic Kidney Disease Epidemiology Collaboration equation. GHF was defined as glomerular filtration rate >the 95th percentile after stratification for age and sex, whereas normal filtration was defined as the 25th to 75th percentiles. HRV indexes, including time domain, frequency domain, and sample entropy, were measured using 24‐hour ambulatory electrocardiography. Clinical outcomes were defined as all‐cause mortality at 2 years. During a mean follow‐up of 16.5±8.2 months, there were 117 deaths (7.2%). GHF was associated with a higher risk of death (hazard ratio and 95% CIs, 1.97 [1.15–3.37]). Reduced HRV indexes, including time domain, frequency domain, and sample entropy (odds ratio and 95% CIs, 0.79 [0.70–0.89]) were all independently associated with the presence of GHF after accounting for age, sex, mean heart rate, morbidities, and medications. In subgroup analysis, reduced HRV was more predictive of GHF in the young than the elderly. Mediation analysis revealed a significant mediation effect between HRV and GHF in addition to their respective detrimental effects on survival.

Conclusions

Reduced HRV was independently associated with the presence of GHF. Autonomic dysfunction may be involved in the pathogenesis of adverse outcomes of GHF in individuals without prior cardiovascular events.

Increased β-adrenergic stimulation augments vascular smooth muscle cell calcification via PKA/CREB signalling

In chronic kidney disease (CKD), hyperphosphatemia promotes medial vascular calcification, a process augmented by osteogenic transdifferentiation of vascular smooth muscle cells (VSMCs). VSMC function is regulated by sympathetic innervation, and these cells express α- and β-adrenergic receptors. The present study explored the effects of β2-adrenergic stimulation by isoproterenol on VSMC calcification. Experiments were performed in primary human aortic VSMCs treated with isoproterenol during control or high phosphate conditions. As a result, isoproterenol dose dependently up-regulated the expression of osteogenic markers core-binding factor α-1 (CBFA1) and tissue-nonspecific alkaline phosphatase (ALPL) in VSMCs. Furthermore, prolonged isoproterenol exposure augmented phosphate-induced calcification of VSMCs. Isoproterenol increased the activation of PKA and CREB, while knockdown of the PKA catalytic subunit α (PRKACA) or of CREB1 genes was able to suppress the pro-calcific effects of isoproterenol in VSMCs. β2-adrenergic receptor silencing or inhibition with the selective antagonist ICI 118,551 blocked isoproterenol-induced osteogenic signalling in VSMCs. The present observations imply a pro-calcific effect of β2-adrenergic overstimulation in VSMCs, which is mediated, at least partly, by PKA/CREB signalling. These observations may support a link between sympathetic overactivity in CKD and vascular calcification.

Avaliação da modulação autonômica da frequência cardíaca de pacientes com doença renal crônica em hemodiálise: estudo preliminar

RESUMO A doença renal crônica (DRC) é definida como dano à função renal. Doentes renais crônicos atingem alta prevalência de morte por eventos cardiovasculares antes dos estágios finais, sendo maior a mortalidade em estágio dialítico, em que é evidenciado um desequilíbrio autonômico. Objetivamos avaliar a modulação simpatovagal de pacientes com DRC em tratamento de hemodiálise ambulatorial. Foram avaliados 23 pacientes, divididos em: Grupo DRC com DRC no estágio 5D (DRC-5D) em tratamento regular de hemodiálise ambulatorial; Grupo-controle com indivíduos saudáveis. A variabilidade da frequência cardíaca (VFC) foi coletada por um cardiofrequencímetro e analisada por índices lineares do domínio do tempo e do domínio da frequência. 14 pacientes no Grupo DRC com média de idade 48±16; e 9 pacientes saudáveis no Grupo-controle com média de idade 64±5. Nos resultados pelo domínio de tempo, o Grupo DRC mostrou valores significativamente maiores da frequência cardíaca (FC) comparado ao Grupo-controle (83,49±13,09 bpm vs. 67,88±9,43 bpm). Todavia, os índices média dos intervalos R-R (735,82±121,54 ms vs. 898,94±123,58 ms), RMSSD (11,75±11,86 ms vs. 20,03±6,80 ms), SDNN (17,06±9,81ms vs. 28,42±7,62 ms) do Grupo DRC mostraram valores significativamente menores comparados aos do Grupo-controle, respectivamente. Nos resultados pelo domínio da frequência, o Grupo DRC mostrou valores significativamente menores em comparação ao Grupo-controle nos índices BFab (129,7±184,3 ms vs. 262,31±168,15 ms) e AFab (82,70±227,66 ms vs. 180,77±119,85 ms). Pacientes com DRC em hemodiálise apresentaram redução da modulação parassimpática quando comparados com indivíduos saudáveis, sugerindo prejuízo do balanço simpatovagal e, consequente, disfunção autonômica cardíaca.

International Consensus Based Review and Recommendations for Minimum Reporting Standards in Research on Transcutaneous Vagus Nerve Stimulation (Version 2020)

Given its non-invasive nature, there is increasing interest in the use of transcutaneous vagus nerve stimulation (tVNS) across basic, translational and clinical research. Contemporaneously, tVNS can be achieved by stimulating either the auricular branch or the cervical bundle of the vagus nerve, referred to as transcutaneous auricular vagus nerve stimulation(VNS) and transcutaneous cervical VNS, respectively. In order to advance the field in a systematic manner, studies using these technologies need to adequately report sufficient methodological detail to enable comparison of results between studies, replication of studies, as well as enhancing study participant safety. We systematically reviewed the existing tVNS literature to evaluate current reporting practices. Based on this review, and consensus among participating authors, we propose a set of minimal reporting items to guide future tVNS studies. The suggested items address specific technical aspects of the device and stimulation parameters. We also cover general recommendations including inclusion and exclusion criteria for participants, outcome parameters and the detailed reporting of side effects. Furthermore, we review strategies used to identify the optimal stimulation parameters for a given research setting and summarize ongoing developments in animal research with potential implications for the application of tVNS in humans. Finally, we discuss the potential of tVNS in future research as well as the associated challenges across several disciplines in research and clinical practice.

Inverted circadian variation of arterial pressure in a geriatric patient: an indicator of autonomic dysfunction

BACKGROUND

Orthostatic hypotension (OH) in geriatric patients frequently involves a component of autonomic failure (AF). The combination of OH with nocturnal hypertension (NHT) is indicative of AF, which is described as pure (PAF), when neurologic symptoms are absent, or as multisystem atrophy (MSA), when combined with motor disturbance (Parkinsonism or Parkinson disease).

CASE PRESENTATION

An 87-year-old man presented with long-lasting OH. He frequently fell, causing several fractures, and he developed heart failure. Blood pressure (BP) registration revealed a reversal of the day-night rhythm with NHT. An 18-FDG PET brain CT scan showed cerebellar hypometabolism, indicating MSA.

CONCLUSIONS

This case demonstrates the use of continuous BP registration in geriatric patients with OH for diagnosing NHT. It illustrates the usefulness of 18-FDG PET brain CT scan to specify the nature of the AF. The case also illustrates the difficulty of managing the combination of OH and NHT.

Autonomic cardiovascular alterations as therapeutic targets in chronic kidney disease

Purpose

The present paper will review the impact of different therapeutic interventions on the autonomic dysfunction characterizing chronic renal failure.

Methods

We reviewed the results of the studies carried out in the last few years examining the effects of standard pharmacologic treatment, hemodialysis, kidney transplantation, renal nerve ablation and carotid baroreceptor stimulation on parasympathetic and sympathetic control of the cardiovascular system in patients with renal failure.

Results

Drugs acting on the renin–angiotensin system as well as central sympatholytic agents have been documented to improve autonomic cardiovascular control. This has also been shown for hemodialysis, although with more heterogeneous results related to the type of dialytic procedure adopted. Kidney transplantation, in contrast, particularly when performed together with the surgical removal of the native diseased kidneys, has been shown to cause profound sympathoinhibitory effects. Finally, a small amount of promising data are available on the potential favorable autonomic effects (particularly the sympathetic ones) of renal nerve ablation and carotid baroreceptor stimulation in chronic kidney disease.

Conclusions

Further studies are needed to clarify several aspects of the autonomic responses to therapeutic interventions in chronic renal disease. These include (1) the potential to normalize sympathetic activity in uremic patients by the various therapeutic approaches and (2) the definition of the degree of sympathetic deactivation to be achieved during treatment.

Autonomic Cardiovascular Alterations in Chronic Kidney Disease: Effects of Dialysis, Kidney Transplantation, and Renal Denervation

PURPOSE OF REVIEW

To review the results of studies of the effects of dialysis and kidney transplantation on the autonomic nervous system alterations that occur in chronic kidney disease.

RECENT FINDINGS

Vagal control of the heart mediated by arterial baroreceptors is altered early in the course of the renal disease. Sympathetic activation occurs, with increases in resting heart rate, venous plasma norepinephrine levels, muscle sympathetic nerve traffic, and other indirect indices of adrenergic drive. The magnitude of the changes reflects the clinical severity of the kidney disease. Both the sympathetic and parasympathetic alterations have a reflex origin, depending on the impairment in baroreflex and cardiopulmonary reflex control of the cardiovascular system. These alterations are partially reversed during acute hemodialysis, but the responses are variable depending on the specific type of dialytic treatment that is employed. Renal transplantation improves reflex cardiovascular control, resulting in sympathoinhibition following renal transplantation if the native kidneys are removed. Sympathoinhibitory effects have been also reported in renal failure patients after bilateral renal denervation. Assessment of autonomic nervous system responses to dialysis and renal transplantation provides information of clinical interest, given the evidence that autonomic alterations are involved in the development and progression of cardiovascular complications, as well as in the prognosis of chronic kidney disease.

Elevated circulating growth differentiation factor 15 is related to decreased heart rate variability in chronic kidney disease patients

Background

Growth differentiation factor 15(GDF15) is a distant member of the superfamily of the transforming growth factor beta (TGF-β). It has been established that increased GDF15 levels are associated with an increased risk of cardiovascular disease. However, the detail effect of GDF15 on cardiovascular system in patients with chronic kidney disease (CKD) needs detail analysis.

Methods

Patients with CKD who did not need dialysis were enrolled in the study. Blood pressure (BP), endothelial function, pulse wave velocity (PWV) and heart rate variability (HRV) were taken in all subjects. Plasma GDF15 concentration was measured by an enzyme-linked immunosorbent assay.

Results

Among the 355 participants, the mean age was 57.4 (±14.2) years old and the mean estimated glomerular filtration rate (eGFR) was 50.1 (±33.2) mL/min/1.73m². The average plasma GDF15 level was 1394.7 (±610.1) pg/mL. Higher GDF15 concentrations were significantly associated with decreased eGFR and increased urine protein-to-creatinine ratio (uPCR). In multivariable models, after adjusting for potential confounders, plasma GDF15 has negative concerning with HRV parameters including the standard deviation of the normal-to-normal (NN) interval (SDNN), the square root of the mean of the sum of the squares of differences between adjacent NN intervals (RMSSD) and Triangular Index.

Conclusion

We observed there was a link between increased plasma of GDF15 and decreased HRV. The mechanisms and prediction of GDF15 in the cardiovascular disease with CKD needs further discussion and study.

Exercise training in dialysis patients: impact on cardiovascular and skeletal muscle health

Dialysis patients show a high rate of reduced functional capacity, morbidity and mortality. Cardiovascular disorders, muscle atrophy and malnutrition play an essential role among the aetiological factors. Sedentary lifestyle characterizes them and contributes to the aggravation of the disorders. On the contrary, exercise training is an important preventive and therapeutic tool both for cardiovascular problems and for the appearance of muscle atrophy in dialysis patients. Regular exercise causes both central (cardiac) and peripheral (muscular) adaptations, improving functional capacity. In particular, circulatory system clinical trials in haemodialysis (HD) patients documented that exercise has favourable effects on heart function, promotes balance on the cardiac autonomic nervous system and contributes to the management of arterial hypertension. In the muscular system, it prevents muscle atrophy or contributes significantly to its treatment. The main preventive mechanisms of the beneficial effect of exercise on the muscles constitute the inhibition of the apoptotic processes and protein degradation. Exercise training in HD patients leads to an increase of muscle fibers, mitochondria and capillaries, and the combination of regular exercise and dietary strategies is even more effective in preventing or treating muscle atrophy. Finally, an improvement in functional capacity and quality of life was found also in peritoneal dialysis patients following exercise training.

Orthostatic hypotension among elderly patients in Italian internal medicine wards: an observational study

Orthostatic hypotension (OH) is a multifactorial disorder, often asymptomatic. The prevalence of OH increases with age, ranging from 5 to 11% among middle-aged patients to 55% in the frail elderly depending on age and associated comorbidities. OH is often unrecognized or misdiagnosed and little is known about its prevalence in hospitalized elderly patients. Our aims were: (1) to determine the prevalence of OH in a cohort of elderly patients hospitalized in two internal medicine wards in Italy; (2) and to describe their characteristics and symptoms. During the 5 months from March 1, 2017 to July 31, 2017, the first 85 consecutive patients (65 years or older) admitted in two internal medicine wards were enrolled. Patients were included in the study if they were able to get out of bed alone or with minor assistance, and able to stand up for at least 3 min. The study population comprised 85 patients with a mean age of 79.6 ( ± 7.2) years. OH was found in 64 (75.3%), occasional OH in 41 (48.2%), persistent OH in 23 (27.1%), and 21 (24.7%) patients had no OH. All patients had diastolic OH and 37 (57.8%) also systolic. Patients with persistent OH were oldest, with a higher percentage of renal failure. Twenty-six patients (40.6%) with OH reported symptoms. Dizziness was the most common symptom, especially after breakfast. No association was found between type of medications and risk of OH. Mortality risk was not statistically different between patients with or without OH 3 (p = 0.10) and 6 months after discharge (p = 0.18), but a trend was observed. We found that OH is very common in the patients admitted in the internal medicine wards, particularly diastolic OH. Close attention should be paid to OH and its symptoms, especially dizziness, in the oldest-old patients, and in patients with renal failure.

Association between heart rate recovery after exercise and renal function in patients referred for treadmill exercise test

Introduction

Heart rate recovery (HRR) is a marker of parasympathetic activity recovery after exercise, and it is associated with cardiovascular mortality and total mortality. Impaired renal function is also associated with cardiac mortality. The aim of this study was to investigate the association between HRR after exercise and renal function in patients referred for a treadmill exercise test.

Patients and methods

This cross-sectional study was conducted at a regional hospital in southern Taiwan. Patients who completed a symptom-limited treadmill exercise test from January 2015 to February 2018 were recruited. Before the treadmill exercise test, patients were asked to complete a questionnaire on the past disease history and lifestyle factors. Serum creatinine measurement within two years prior to or after the date of the treadmill exercise test of the patients was also obtained from the medical records for these patients. Estimated glomerular filtration rate (eGFR) was calculated. Simple and multiple linear regression analyses were performed to investigate the association between one-minute HRR and eGFR.

Results

A total of 2,825 patients completed the treadmill exercise test, and serum creatinine measurement was identified from medical records for 2,153 patients (76.2%). Multiple linear regression analysis revealed that a lower eGFR was significantly associated with lower one-minute HRR (P< 0.001), adjusting for other significant independent factors, including age, waist circumference, type 2 diabetes mellitus, and smoking.

Conclusions

In this cross-sectional observational study, a lower eGFR was significantly and independently associated with decreased one-minute HRR, suggesting that parasympathetic activity recovery after exercise could be impaired by a decrease in renal function.

Chronic Kidney Disease as a Risk Factor for Heart Failure With Preserved Ejection Fraction: A Focus on Microcirculatory Factors and Therapeutic Targets

Heart failure (HF) and chronic kidney disease (CKD) co-exist, and it is estimated that about 50% of HF patients suffer from CKD. Although studies have been performed on the association between CKD and HF with reduced ejection fraction (HFrEF), less is known about the link between CKD and heart failure with preserved ejection fraction (HFpEF). Approximately, 50% of all patients with HF suffer from HFpEF, and this percentage is projected to rise in the coming years. Therapies for HFrEF are long established and considered quite successful. In contrast, clinical trials for treatment of HFpEF have all shown negative or disputable results. This is likely due to the multifactorial character and the lack of pathophysiological knowledge of HFpEF. The typical co-existence of HFpEF and CKD is partially due to common underlying comorbidities, such as hypertension, dyslipidemia and diabetes. Macrovascular changes accompanying CKD, such as hypertension and arterial stiffening, have been described to contribute to HFpEF development. Furthermore, several renal factors have a direct impact on the heart and/or coronary microvasculature and may underlie the association between CKD and HFpEF. These factors include: (1) activation of the renin-angiotensin-aldosterone system, (2) anemia, (3) hypercalcemia, hyperphosphatemia and increased levels of FGF-23, and (4) uremic toxins. This review critically discusses the above factors, focusing on their potential contribution to coronary dysfunction, left ventricular stiffening, and delayed left ventricular relaxation. We further summarize the directions of novel treatment options for HFpEF based on the contribution of these renal drivers.

The regulation effect of WNT-RAS signaling in hypothalamic paraventricular nucleus on renal fibrosis

Background

Abnormal activation of wnt/β-catenin signaling and renin-angiotensin system is known to play a vital role in the development and progression of CKD. We hypothesized that abnormal expression of central wnt/β-catenin signaling and renin-angiotensin system (WNT-RAS signaling) was tightly involved in CKD.

Methods

We established sham-operated and 5/6 nephrectomized (5/6 NX) rat model and blocked the central wnt signaling by intracerebroventricular injection of adeno-associated virus vector which can overexpress target gene DKK1. The central and renal expression level of wnt/β-catenin signaling and RAS and renal injury were assessed.

Results

The expression levels of the main wnt/β-catenin signaling components in both brain and kidney of 5/6NX rats, such as wnt3a and active-β-catenin, were elevated obviously and the up-regulation were inhibited by central blockade of the wnt signaling. Furthermore, the expression of the major components of RAS in both brain and kidney in 5/6NX rats, such as angiotensinogen (AGT), angiotensin converting enzyme (ACE-1), angiotensin II AT1-receptor (AT1R), was significantly up-regulated and the up-regulated expression was inhibited by central blockade of the wnt singling. Notably, central blockade of the wnt signaling improved renal function as indicated by decreased serum creatinine and 24 h urinary protein, and attenuated interstitial fibrosis as indicated by reduced Sirius red staining and expression of Fibronectin, Collagen-I and α-SMA.

Conclusion

These data suggest that the central WNT-RAS signaling plays a significant role in the development and progression of CKD.

Does glucagon-like peptide-1 induce diuresis and natriuresis by modulating afferent renal nerve activity?

Glucagon-like peptide-1 (GLP-1), an incretin hormone, has diuretic and natriuretic effects. The present study was designed to explore the possible underlying mechanisms for the diuretic and natriuretic effects of GLP-1 via renal nerves in rats. Immunohistochemistry revealed that GLP-1 receptors were avidly expressed in the pelvic wall, the wall being adjacent to afferent renal nerves immunoreactive to calcitonin gene-related peptide, which is the dominant neurotransmitter for renal afferents. GLP-1 (3 μM) infused into the left renal pelvis increased ipsilateral afferent renal nerve activity (110.0 ± 15.6% of basal value). Intravenous infusion of GLP-1 (1 µg·kg^-1·min^-1) for 30 min increased renal sympathetic nerve activity (RSNA). After the distal end of the renal nerve was cut to eliminate the afferent signal, the increase in efferent renal nerve activity during intravenous infusion of GLP-1 was diminished compared with the increase in total RSNA (17.0 ± 9.0% vs. 68.1 ± 20.0% of the basal value). Diuretic and natriuretic responses to intravenous infusion of GLP-1 were enhanced by total renal denervation (T-RDN) with acute surgical cutting of the renal nerves. Selective afferent renal nerve denervation (A-RDN) was performed by bilateral perivascular application of capsaicin on the renal nerves. Similar to T-RDN, A-RDN enhanced diuretic and natriuretic responses to GLP-1. Urine flow and Na⁺ excretion responses to GLP-1 were not significantly different between T-RDN and A-RDN groups. These results indicate that the diuretic and natriuretic effects of GLP-1 are partly governed via activation of afferent renal nerves by GLP-1 acting on sensory nerve fibers within the pelvis of the kidney.

How Low Do We Go (in the Post-SPRINT Era)?

Hypertension is frequently both a cause and complication of CKD. The optimal blood pressure target in CKD has been of hot debate over the decades with little data to inform the goals. Here, we review the data from the Systolic Blood Pressure Intervention Trial (SPRINT), Modification of Diet in Renal Disease (MDRD), African American Study of Kidney Disease and Hypertension (AASK), Ramipril Efficacy in Nephropathy-2 (REIN-2), and Action to Control Cardiovascular Risk in Diabetes (ACCORD) trials to use the available evidence to better inform what blood pressure goal should be recommended in patients with CKD and to answer the question "How low should we go?".

Heart Rate Variability and Its Relation to Chronic Kidney Disease: Results From the PREVEND Study

OBJECTIVE

In the general population, reduced heart rate variability (HRV) has been associated with cardiovascular disease. However, its relation to chronic kidney disease (CKD) is debated. We therefore investigated the relation between low HRV and renal outcomes.

METHODS

In the population-based Prevention of REnal and Vascular ENdstage Disease study, renal outcomes (CKD, estimated glomerular filtration rate [eGFR], urinary albumin) were measured at baseline and three consecutive examinations. HRV measures (among which SDNN [standard deviation of normal-to-normal RR intervals]) were calculated from time series of beat-to-beat pulse wave recordings at baseline. The lowest (risk) quartile was compared with the upper three quartiles combined, in multivariable survival and linear mixed-effects analyses.

RESULTS

In 4605 participants (49% males, age range = 33-80, 0.6% blacks), we observed 341 new participants of CKD during a median follow-up duration of 7.4 years. Low SDNN was associated with higher incidence of CKD (crude HR = 1.66, 95% CI = 1.30 to 2.12, p < .001), but this association was no longer significant after adjustment for age, sex, and cardiovascular risk factors (adjusted HR = 1.13, 95% CI = 0.86 to 1.48, p = .40, similar for other HRV measures). No associations between SDNN and eGFR trajectories were found in the total sample. However, in a subgroup of participants with baseline CKD (n = 939), we found a significant association of low SDNN (but not other HRV measures) with lower baseline eGFR, even after multivariable adjustment (adjusted βlevel difference = -3.73 ml/min/1.73 m, 95% CI = -6.70 to -0.75, p = .014), but not with steeper eGFR decline.

CONCLUSIONS

These results suggest that reduced HRV may be a complication of CKD rather than a causal factor.

Upper Extremity Medial Arterial Calcification and Peripheral Artery Disease in Asymptomatic Patients With Chronic Kidney Disease in Predialysis Stage

Two types of peripheral artery disease (PAD) in asymptomatic patients with chronic kidney disease (CKD) can be detected by the use of duplex Doppler: medial arterial calcification (MAC) and occlusive PAD. The aim of this pilot study is to evaluate different types of subclinical PAD in upper extremities of patients with CKD. The prevalence of upper extremity MAC and occlusive PAD was investigated in 41 asymptomatic patients with CKD and 18 controls with normal kidney function, using duplex Doppler ultrasound, according to the vascular laboratory protocol. A mild-to-severe MAC was significantly more prevalent in patients with CKD compared to the control group ( P = .015), mostly in radial arteries (RAs; P = .002 and P = .016, respectively). The prevalence of occlusive PAD was not significantly different between the 2 groups ( P = .381). Patients in the CKD group were younger, nonsmokers, and more often had hypertension ( P = .038, P = .038, and P = .034, respectively). A duplex ultrasound screening for upper extremity subclinical PAD in patients with CKD in a predialysis stage may identify patients with mild-to-severe MAC which is important in surgery of hemodialysis access.

Graded Association Between Kidney Function and Impaired Orthostatic Blood Pressure Stabilization in Older Adults

Background

Impaired orthostatic blood pressure (BP) stabilization is highly prevalent in older adults and is a predictor of end‐organ injury, falls, and mortality. We sought to characterize the relationship between postural BP responses and the kidney.

Methods and Results

We performed a cross‐sectional analysis of 4204 participants from The Irish Longitudinal Study on Ageing, a national cohort of community‐dwelling adults aged ≥50 years. Beat‐to‐beat systolic and diastolic BP were measured during a 2‐minute active stand test. The primary predictor was cystatin C estimated glomerular filtration rate (eGFR) categorized as follows (mL/min per 1.73 m²): ≥90 (reference, n=1414); 75 to 89 (n=1379); 60 to 74 (n=942); 45 to 59 (n=337); <45 (n=132). We examined the association between eGFR categories and (1) sustained orthostatic hypotension, defined as a BP drop exceeding consensus thresholds (systolic BP drop ≥20 mm Hg±diastolic BP drop ≥10 mm Hg) at each 10‐second interval from 60 to 110 seconds inclusive; (2) pattern of BP stabilization, characterized as the difference from baseline in mean systolic BP/diastolic BP at 10‐second intervals. The mean age of subjects was 61.6 years; 47% of subjects were male, and the median eGFR was 82 mL/min per 1.73 m². After multivariable adjustment, participants with eGFR <60 mL/min per 1.73 m² were approximately twice as likely to have sustained orthostatic hypotension (P=0.008 for trend across eGFR categories). We observed a graded association between eGFR categories and impaired orthostatic BP stabilization, particularly within the first minute of standing.

Conclusions

We report a novel, graded relationship between diminished eGFR and impaired orthostatic BP stabilization. Mapping the postural BP response merits further study in kidney disease as a potential means of identifying those at risk of hypotension‐related events.

A heart-brain-kidney network controls adaptation to cardiac stress through tissue macrophage activation

Heart failure is a complex clinical syndrome characterized by insufficient cardiac function. In addition to abnormalities intrinsic to the heart, dysfunction of other organs and dysregulation of systemic factors greatly affect the development and consequences of heart failure. Here we show that the heart and kidneys function cooperatively in generating an adaptive response to cardiac pressure overload. In mice subjected to pressure overload in the heart, sympathetic nerve activation led to activation of renal collecting-duct (CD) epithelial cells. Cell-cell interactions among activated CD cells, tissue macrophages and endothelial cells within the kidney led to secretion of the cytokine CSF2, which in turn stimulated cardiac-resident Ly6C^lo macrophages, which are essential for the myocardial adaptive response to pressure overload. The renal response to cardiac pressure overload was disrupted by renal sympathetic denervation, adrenergic β2-receptor blockade or CD-cell-specific deficiency of the transcription factor KLF5. Moreover, we identified amphiregulin as an essential cardioprotective mediator produced by cardiac Ly6C^lo macrophages. Our results demonstrate a dynamic interplay between the heart, brain and kidneys that is necessary for adaptation to cardiac stress, and they highlight the homeostatic functions of tissue macrophages and the sympathetic nervous system.

Effects of stroke on changes in heart rate variability during hemodialysis

Background

Stroke and low heart rate variability (HRV) are both associated with an unfavorable prognosis in hemodialysis patients. The relationship between stroke and changes in HRV during hemodialysis remains unclear.

Methods

This study measured differences between predialysis and postdialysis HRV (△HRV) in 182 maintenance hemodialysis patients, including 30 patients with stroke, to assess changes in HRV during hemodialysis, and also to compare results to 114 healthy controls.

Results

All predialysis HRV measurements had no differences between stroke patients and those without stroke, but were lower than healthy controls. Postdialysis very low frequency (VLF) (P < 0.001), low frequency (LF) (P = 0.001), total power (TP) (P < 0.001) and the LF/high frequency (HF) ratio (P < 0.001) increased significantly relative to predialysis values in patients without stroke, whereas postdialysis HRV did not increase in stroke patients. After multivariate adjustment, dialysis vintage was negatively associated with △VLF (β = -0.698, P = 0.046), △LF (β = -0.931, P = 0.009), and △TP (β = -0.887, P = 0.012) in patients without stroke. Serum intact parathyroid hormone (β = -0.707, P = 0.019) was negatively associated with △LF. Total cholesterol (β = -0.008, P = 0.001) and high sensitivity C-reactive protein (β = -0.474, P = 0.012) were inversely correlated with the △LF/HF ratio in patients without stroke.

Conclusion

HRV in hemodialysis patients is lower than in the general population. Increase in △HRV was observed in hemodialysis patients without stroke but not in stroke patients. This result suggests suppressed autonomic nervous reactions against volume unloading during hemodialysis, which might contribute to unfavorable outcomes in hemodialysis patients but even more so in those with prior stroke. Nephrologists should notice the importance of △HRV especially in high-risk patients.

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.