Prognostic indicators of cardiovascular risk in renal disease

Diagnostic accuracy of Bellavere's score in cardiac autonomic neuropathy among chronic kidney disease patients: a study of prevalence and dialysis impact

Background

Cardiac autonomic neuropathy (CAN) is a significant complication in chronic kidney disease (CKD), leading to increased morbidity and mortality. Early detection is essential for managing CKD patients effectively, especially those on hemodialysis. This study evaluated the prevalence CAN in CKD and diagnostic accuracy of Bellavere's Score in predicting CAN in CKD patients, including those undergoing hemodialysis.

Methods

This prospective observational study included 200 CKD patients. Cardiac autonomic neuropathy was assessed using Bellavere's Score, calculated through a series of autonomic function tests including heart rate variability and blood pressure responses. Bellavere's Score was measured pre-and post-dialysis in hemodialysis patients. The diagnostic performance of the score was evaluated using receiver operating characteristic (ROC) curves to determine sensitivity, specificity, and likelihood ratios.

Results

Among the patients, 60% were diagnosed with CAN, with 35% having early CAN and 24% severe CAN. Bellavere's Score showed high diagnostic accuracy across CKD stages, with sensitivity ranging from 75 to 89.29% and specificity from 69.09 to 96%. In CKD stage III patients, the sensitivity was 78.57% and specificity 91.4%. In stage V, sensitivity increased to 89.29%, though specificity dropped to 69.09%. For hemodialysis patients, Bellavere's Score exhibited a sensitivity of 79.78% and specificity of 79.28%. The prevalence of CAN decreased significantly from 79.8% pre-dialysis to 64% post-dialysis (p < 0.01).

Conclusion

Bellavere's Score provides a reliable and non-invasive approach for diagnosing CAN in CKD patients, with strong diagnostic performance across different disease stages and in hemodialysis. Larger studies are warranted to further validate its utility.

Influence of Regular Physical Activity on Sleep

Good sleep and adequate physical activity are essential to health. Yet, large numbers of people are chronically deficient in sleep and physical activity. About 1 in 3 Americans get less than 7 h of sleep per night and only 1 of 4 adults regularly complete weekly physical activity in amounts recommended for good health. This chapter reviews research that has examined relationships between regular physical activity and sleep. The overall weight of evidence supports that regular physical activity is associated with better sleep quality among healthy adults, with epidemiological studies showing moderate-sized effects and more well-controlled randomized controlled trial experiments often showing larger effects. Large epidemiology studies suggest that the relationship between regular physical activity and better sleep quality may partially mediate the well-established associations between physical activity and reduced risk of mortality, cardiovascular diseases, and dementia. There is evidence that the completion of regular physical activity also is associated with better sleep quality among those with certain sleep disorders (i.e., insomnia, obstructive sleep apnea, and restless legs syndrome), mental health disorders (i.e., depression and posttraumatic stress disorder), and medical illnesses (i.e., breast cancer survivors). The evidence is inadequate to support that regular physical activity substantially improves sleep quality either (i) in children, adolescents, and older adults, (ii) in those with cancers except for breast cancer, (iii) in those with fibromyalgia, or (iv) among those with chronic kidney disease. Also, there is inadequate evidence to conclude that sleep quality is disrupted during weeks when competitive athletes engage in periods of overtraining.

Correlation of plasma metabolites and comorbid illnesses with poor sleep quality in patients with coronary heart disease

PURPOSE

This study aimed to examine the relationship between plasma metabolites (biochemical parameters) and comorbid illnesses with sleep quality in individuals with coronary heart disease (CHD).

METHODS

This descriptive cross-sectional study was conducted between 2020 and 2021 at a university hospital. Hospitalized patients with a diagnosis of CHD were analyzed. The Personal Information Form' and Pittsburgh Sleep Quality Index (PSQI) were used to collect data. Laboratory findings including plasma metabolites were examined.

RESULTS

Of 60 hospitalized patients with CHD, 50 (83%) had poor sleep quality. A positive and statistically significant correlation was found between the plasma metabolite blood urea nitrogen and poor sleep quality (r = 0.399; p = 0.002). The presence of CHD and additional chronic diseases (especially diabetes mellitus, hypertension, and chronic kidney disease) are important parameters associated with the risk of poor sleep quality (p = 0.040 < 0.05).

CONCLUSION

Increases in blood urea nitrogen level in individuals with CHD are associated with worse sleep quality. Additional chronic diseases coexisting with CHD correlate with increased risk of poor sleep quality.

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.

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.

Levels of trace blood elements associated with severe sleep disturbance in maintenance hemodialysis patients

PURPOSE

Sleep disturbance is frequently observed in patients on maintenance hemodialysis (MHD), and this population usually presents imbalances in trace elements. We investigated the association between blood trace element levels and sleep quality in patients on MHD.

METHODS

This cross-sectional and single-center study was performed in September 2019. Patients regularly undergoing hemodialysis for > 3 months at our center were recruited, and demographic, clinical, and laboratory parameters were recorded. The Pittsburgh Sleep Quality Index (PSQI) was applied to define sleep disturbance. Blood trace element (zinc, manganese, copper, selenium, and lead) levels were measured using an inductively coupled plasma mass spectrometer.

RESULTS

In total, 121 patients on MHD (male/female = 68:53) were enrolled in the study (mean age 63.7 ± 13.9 years, median dialysis vintage 38.0 [20.0, 60.0] months). According to PSQI, 56 (46%) patients experienced severe sleep disturbance. These patients were characterized by older age, higher serum parathyroid hormone levels, and lower blood selenium levels (all P < 0.05). No significant differences in blood zinc, manganese, copper, and lead levels were observed between groups. Univariate binary logistic regression showed that lower blood selenium levels were associated with severe sleep disturbance (odds ratio = 0.976, 95% confidence interval: 0.954-0.999, P = 0.038). Multivariate analyses also confirmed the results after adjusting for confounding factors.

CONCLUSION

Our study indicated an association between lower blood selenium levels and the occurrence of severe sleep disturbances in patients on MHD. However, a prospective study with a larger sample size and assessing the importance of selenium supplementation are needed to confirm the results.

Heart rhythm complexity as predictors for the prognosis of end-stage renal disease patients undergoing hemodialysis

BACKGROUND

Heart rhythm complexity, a measure of heart rate dynamics and a risk predictor in various clinical diseases, has not been systematically studied in patients with end-stage renal disease. The aim of this study is to investigate the heart rhythm complexity and its prognostic value for mortality in end-stage renal disease patients undergoing hemodialysis.

METHODS

To assess heart rhythm complexity and conventional heart rate variability measures, 4-h continuous electrocardiography for a retrospective cohort of 202 ostensibly healthy control subjects and 51 hemodialysis patients with end-stage renal disease were analyzed. Heart rhythm complexity was quantified by the complexity index from the measurement of the multiscale entropy profile.

RESULTS

During a follow-up of 13 months, 8 people died in the patient group. Values of either traditional heart rate variability measurements or complexity indices were found significantly lower in patients than those in healthy controls. In addition, the complexity indices (Area 1-5, Area 6-15 and Area 6-20) in the mortality group were significantly lower than those in the survival group, while there were no significant differences in traditional heart rate variability parameters between the two groups. In receiver operating characteristic curve analysis, Area 6-20 (AUC = 0.895, p < 0.001) showed the strongest predictive power between mortality and survival groups.

CONCLUSION

The results suggest that heart rhythm complexity is impaired for patients with end-stage renal disease. Furthermore, the complexity index of heart rate variability quantified by multiscale entropy may be a powerful independent predictor of mortality in end-stage renal disease patients undergoing hemodialysis.

Device-Based Neuromodulation for Resistant Hypertension Therapy

Despite availability of effective drugs for hypertension therapy, significant numbers of hypertensive patients fail to achieve recommended blood pressure levels on ≥3 antihypertensive drugs of different classes. These individuals have a high prevalence of adverse cardiovascular events and are defined as having resistant hypertension (RHT) although nonadherence to prescribed antihypertensive medications is common in patients with apparent RHT. Furthermore, apparent and true RHT often display increased sympathetic activity. Based on these findings, technology was developed to treat RHT by suppressing sympathetic activity with electrical stimulation of the carotid baroreflex and catheter-based renal denervation (RDN). Over the last 15 years, experimental and clinical studies have provided better understanding of the physiological mechanisms that account for blood pressure lowering with baroreflex activation and RDN and, in so doing, have provided insight into which patients in this heterogeneous hypertensive population are most likely to respond favorably to these device-based therapies. Experimental studies have also played a role in modifying device technology after early clinical trials failed to meet key endpoints for safety and efficacy. At the same time, these studies have exposed potential differences between baroreflex activation and RDN and common challenges that will likely impact antihypertensive treatment and clinical outcomes in patients with RHT. In this review, we emphasize physiological studies that provide mechanistic insights into blood pressure lowering with baroreflex activation and RDN in the context of progression of clinical studies, which are now at a critical point in determining their fate in RHT management.

Altered Autonomic Reactivity During Lower Body Negative Pressure in End-Stage Renal Disease

BACKGROUND

End stage renal disease (ESRD) is characterized by autonomic dysfunction. During orthostatic stress, sympathetic (SNS) activity increases and parasympathetic (PNS) activity decreases to maintain arterial blood pressure (BP). We hypothesized that ESRD patients have impaired ability to adjust cardiac SNS and PNS activity during orthostasis, which could contribute to increased blood pressure variability, orthostatic intolerance and falls.

METHODS

We measured beat-to-beat BP and Electrocardiography at baseline and during increasing lower body negative pressure (LBNP) in 20 ESRD patients and 18 matched controls (CON). Heart rate variability was quantified as total power (TP) and standard deviation of the N-N interval, reflecting both SNS and PNS; high frequency (HF), root mean square of successive differences of neighboring N-N intervals (RMSSD), and percent of consecutive N-N intervals differing >50 milliseconds (pNN50), reflecting cardiac PNS activity; and low frequency (LF) and LF/HF, reflecting sympoathovagal balance. BP variability was quantified as the standard deviation in systolic (SDSAP) and diastolic (SDDAP) BP.

RESULTS

Baseline HF, RMSSD, and pNN50 were significantly lower in ESRD (P < 0.05). While CON had a significant decrease in HF (P = 0.015), RMSSD (P = 0.003), and pNN50 (P = 0.005) during LBNP, there was no change in heart rate variability in ESRD. There was no significant difference in BP response, but ESRD had a significantly blunted heart rate response during graded LBNP compared to controls (P < 0.001). There was no significant difference in SDSAP or SDDAP during LBNP between groups (P > 0.05).

CONCLUSIONS

These data suggest that ESRD patients have impaired autonomic adjustments to orthostatic stress.

Effects of whole body vibration on cardiac autonomic function and exercise capacity in renal transplant recipients

Background/Aims

Whole body vibration is an exercise alternative that can be used in the rehabilitation of renal transplant recipients with the aim of reducing cardiovascular risk. The aim of this study was to evaluate the effects of whole body vibration training on heart rate variability, cardiorespiratory parameters and functional capacity on five renal transplant recipients.

Methods

Renal transplant recipients underwent whole body vibration exercise twice a week for a total of 12 weeks. All participants were monitored using the 24-hour Holter to evaluate the heart rate variability domains. An exercise test to evaluate maximal oxygen consumption and the distance walked in the Six-Minute Walk Test to evaluate functional capacity were also recorded.

Results

Overall, two of the five transplant recipients improved sympathovagal balance at the end of the study. Maximal oxygen consumption improved in three transplanted patients, and the distance walked improved for two patients. The results showed that whole body vibration training improved heart rate variability and maximal and submaximal test performance in some transplanted recipients.

Conclusion

The 12-week training protocol with twice weekly whole body vibration sessions was sufficient to improve heart rate variability and the performance of maximal and submaximal tests in some renal transplant recipients, although the responses were heterogeneous for the considered variables. Whole body vibration may be an alternative to conventional means of physical exercise because it causes minimal cardiovascular stress, which could be especially indicated for this population given the risk presence of arrhythmias and sudden death; therefore studies with better designs need to be developed in order to verify the effectiveness of this intervention.

Baroreflex function, haemodynamic responses to an orthostatic challenge, and falls in haemodialysis patients

BACKGROUND

Stage 5 chronic kidney disease patients on haemodialysis (HD) often present with dizziness and pre-syncopal events as a result of the combined effect of HD therapy and cardiovascular disease. The dysregulation of blood pressure (BP) during orthostasis may be implicated in the aetiology of falls in these patients. Therefore, we explored the relationship between baroreflex function, the haemodynamic responses to a passive orthostatic challenge, and falls in HD patients.

METHODS

Seventy-six HD patients were enrolled in this cross-sectional study. Participants were classified as "fallers" and "non-fallers" and completed a passive head up tilting to 60o (HUT-60°) test on an automated tilt table. ECG signals, continuous and oscillometric BP measurements and impedance cardiography were recorded. The following variables were derived from these measurements: heart rate (HR) stroke volume (SV), cardiac output (CO), total peripheral resistance (TPR), number of baroreceptor events, and baroreceptor effectiveness index (BEI).

RESULTS

The forty-four participants who were classified as fallers (57.9%) had a lower number of baroreceptor events (6.5±8.5 vs 14±16.7, p = .027) and BEI (20.8±24.2% vs 33.4±23.3%, p = .025). In addition, fallers experienced a significantly larger drop in systolic (-6.4±10.9 vs -0.4±7.7 mmHg, p = .011) and diastolic (-2.7±7.3 vs 1.8±6 mmHg, p = .027) oscillometric BP from supine to HUT-60° compared with non-fallers. None of the variables taken for the analysis were significantly associated with falls in multivariate logistic regression analysis.

CONCLUSIONS

This cross-sectional comparison indicates that, at rest, HD patients with a positive history of falls present with a lower count of baroreceptor sequences and BEI. Short-term BP regulation warrants further investigation as BP drops during a passive orthostatic challenge may be implicated in the aetiology of falls in HD.

Autonomic Dysfunction in Wilson's Disease: A Comprehensive Evaluation during a 3-Year Follow Up

Objectives: Wilson's disease is reported to have autonomic dysfunction, but comprehensive evaluation of autonomic function is lacking. Additionally, little is known about the change of autonomic function of Wilson's disease during continuous therapy. We assumed that patients with Wilson's disease had both sympathetic and parasympathetic autonomic impairments, and the autonomic dysfunction might be stable across a 3-year follow-up after years of optimal treatment.

Methods: Twenty-six patients with Wilson's disease and twenty-six healthy controls were recruited. Twenty patients in the Wilson's disease group were examined again after a 3-year follow-up. All the participants were evaluated by a questionnaire on dysautonomia symptoms, 24-h blood pressure and heart rate monitoring, and cardiovascular autonomic function examination in various conditions including at rest, deep breathing, Valsalva maneuver, isometric handgrip test and passive tilting. Baroreflex sensitivity and spectral analyses were performed via trigonometric regressive spectral analysis.

Results: Patients with Wilson's disease showed autonomic dysfunction mainly in the following aspects: (1) the heart rate was higher than the controls. (2) Valsalva ratio was lower in patients with Wilson's disease compared with the controls. (3) Heart rate increase during isometric hand gripping was smaller in the Wilson's disease patients than the controls. (4) Baroreflex sensitivity was lower during nearly all the cardiovascular autonomic function examinations compared with healthy controls. When tested 3 years later, baroreflex sensitivity at rest decreased compared with baseline. (5) There were mild declines of resting DBP and low frequency component of heart rate variability during the follow-up examination compared with baseline. (6) Subgroup analysis showed that patients initially presenting with neurological symptoms had a higher night-time heart rate, lower expiration: inspiration RR interval ratio (E/I ratio), lower expiration: inspiration RR interval difference (E-I difference), less increase of heart rate and diastolic blood pressure during the handgrip test, and lower baroreflex sensitivity during deep breathing than the control group. (7) Correlation analysis showed that the severity of neurological symptoms was associated with E/I ratio, E-I difference, Valsalva ratio, heart rate change during the handgrip test, and baroreflex sensitivity during deep breathing.

Conclusions: The present study reveals cardiovascular autonomic dysfunction involving both sympathetic and parasympathetic branches in Wilson's disease patients, which is especially significant in the patients with neurological onset. Autonomic function is generally stable undergoing optimal maintenance treatment in patients with Wilson's disease. Though there might be mild changes of specific parameters.

Effect of discontinuing morning dose of antihypertensive for renal transplant surgery on haemodynamic and early graft functioning: A prospective, double-blind, randomised study

BACKGROUND AND AIMS

Antihypertensive drugs are continued until the day of renal transplant surgery. These are associated with increased incidence of hypotension and bradycardia. Hence, this study was designed to evaluate perioperative haemodynamic and early graft functioning in renal recipients with discontinuation of antihypertensive drugs on the morning of surgery.

METHODS

This prospective, randomised, double-blind study recruited 120 patients. Group 1 patients received placebo tablet while Group 2 patients received usual antihypertensive drugs on the day of surgery. Perioperative haemodynamics and time for reinstitution of antihypertensives were the primary outcome measures. The secondary outcome measures were need for inotropic support and graft function. Perioperative haemodynamics were analysed using ANOVA and Student's t-tests with Bonferroni correction. Fischer's exact test was used for analysis.

RESULTS

Systolic blood pressure (SBP) declined, which was more in Group 2. Forty-one patients developed significant hypotension; a correlation was found between the maximum observed hypotension and number of antihypertensive medications (P = 0.003). Four cases had slow graft function (one in Group 1 and three in Group 2). Twenty-eight patients in Group 2 required mephentermine boluses to maintain their SBP compared to 13 patients in Group 1 (P < 0.001). Two patients in Group 2 required dopamine to maintain SBP above 90 mmHg after the establishment of reperfusion as compared to none in Group 1.

CONCLUSION

Single dose of long-acting antihypertensive drugs can be omitted on the morning of surgery without any haemodynamic fluctuations and graft function in controlled hypertensive end-stage renal disease renal transplant patients receiving a combined epidural and general anaesthesia.

Sleep disorders and chronic kidney disease

Sleep disorders have a profound and well-documented impact on overall health and quality of life in the general population. In patients with chronic disease, sleep disorders are more prevalent, with an additional morbidity and mortality burden. The complex and dynamic relationship between sleep disorders and chronic kidney disease (CKD) remain relatively little investigated. This article presents an overview of sleep disorders in patients with CKD, with emphasis on relevant pathophysiologic underpinnings and clinical presentations. Evidence-based interventions will be discussed, in the context of individual sleep disorders, namely sleep apnea, insomnia, restless leg syndrome and excessive daytime sleepiness. Limitations of the current knowledge as well as future research directions will be highlighted, with a final discussion of different conceptual frameworks of the relationship between sleep disorders and CKD.

Cardiovascular Autonomic Dysfunction in Chronic Kidney Disease: a Comprehensive Review

Cardiovascular autonomic dysfunction is a major complication of chronic kidney disease (CKD), likely contributing to the high incidence of cardiovascular mortality in this patient population. In addition to adrenergic overdrive in affected individuals, clinical and experimental evidence now strongly indicates the presence of impaired reflex control of both sympathetic and parasympathetic outflow to the heart and vasculature. Although the principal underlying mechanisms are not completely understood, potential involvements of altered baroreceptor, cardiopulmonary, and chemoreceptor reflex function, along with factors including but not limited to increased renin-angiotensin-aldosterone system activity, activation of the renal afferents and cardiovascular structural remodeling have been suggested. This review therefore analyzes potential mechanisms underpinning autonomic imbalance in CKD, covers results accumulated thus far on cardiovascular autonomic function studies in clinical and experimental renal failure, discusses the role of current interventional and therapeutic strategies in ameliorating autonomic deficits associated with chronic renal dysfunction, and identifies gaps in our knowledge of neural mechanisms driving cardiovascular disease in CKD.

Baroreflex activation: from mechanisms to therapy for cardiovascular disease

Recent technical advances have led to the development of a medical device that can reliably activate the carotid baroreflex with an acceptable degree of safety. Because activation of the sympathetic nervous system plays an important role in the pathogenesis of hypertension and heart failure, the unique ability of this device to chronically suppress central sympathetic outflow in a controlled manner suggests potential value in the treatment of these conditions. This notion is supported by both clinical and experimental animal studies, and the major aim of this article is to elucidate the physiological mechanisms that account for the favorable effects of baroreflex activation therapy in patients with resistant hypertension and heart failure. Illumination of the neurohormonal, renal, and cardiac actions of baroreflex activation is likely to provide the means for better identification of those patients that are most likely to respond favorably to this device-based therapy.

Effects of fluid overload on heart rate variability in chronic kidney disease patients on hemodialysis

Background

While fluid overload (FO) and alterations in the autonomic nervous system (ANS) such as hypersympathetic activity, are known risk factors for cardiovascular morbidity and mortality in patients on chronic hemodialysis (HD), their relationship has not been thoroughly studied.

Methods

In this observational study involving 69 patients on chronic HD, FO was assessed by whole body bioimpedance measurements before the midweek HD session and ANS activity reflected by Heart Rate Variability (HRV) was measured using 24-hour Holter electrocardiogram recordings starting before the same HD treatment. In total, 13 different HRV indices were analyzed, comprising a mixture of time domain, frequency domain and complexity parameters. A correlation analysis was performed between the HRV indices and hydration status indices. Successively, patients were retrospectively assigned to a high FO (H, FO > 2.5 L) or low FO (L, FO ≤ 2.5 L) group and these were further compared also after stratification by diabetes mellitus. Finally, a small number of patients without diabetes with significant and persistent FO were followed up for 3 months post-study to investigate how normalization of fluid status affects HRV.

Results

SDANN, VLF, LZC and HF% parameters significantly correlate with FO (correlation coefficients were respectively r = –0.40, r = –0.37, r = –0.28 and r = 0.26, p-value < 0.05). Furthermore, LF% and LF/HF were inversely correlated with hydration status (correlation coefficients were respectively r = –0.31 and r = -0.33, p-value < 0.05). These results indicate an association between FO and reduced HRV, higher parasympathetic activation and reduced sympathetic response to the HD session. Indeed, group H tended to have lower values of SDANN, VLF and LZC, and higher values of HF% than patients in the L group. Finally, there was a trend towards lower LF% measured during the last 30 minutes of HD for the H group versus the L group. Reduction in FO achieved over 3 months by implementation of a strict fluid management plan resulted in an increase of HRV.

Conclusions

Our results suggest that depressed HRV is associated with fluid overload and that normalization of hydration status is accompanied by improved HRV.

Chronic baroreflex activation restores spontaneous baroreflex control and variability of heart rate in obesity-induced hypertension

The sensitivity of baroreflex control of heart rate is depressed in subjects with obesity hypertension, which increases the risk for cardiac arrhythmias. The mechanisms are not fully known, and there are no therapies to improve this dysfunction. To determine the cardiovascular dynamic effects of progressive increases in body weight leading to obesity and hypertension in dogs fed a high-fat diet, 24-h continuous recordings of spontaneous fluctuations in blood pressure and heart rate were analyzed in the time and frequency domains. Furthermore, we investigated whether autonomic mechanisms stimulated by chronic baroreflex activation and renal denervation-current therapies in patients with resistant hypertension, who are commonly obese-restore cardiovascular dynamic control. Increases in body weight to ∼150% of control led to a gradual increase in mean arterial pressure to 17 ± 3 mmHg above control (100 ± 2 mmHg) after 4 wk on the high-fat diet. In contrast to the gradual increase in arterial pressure, tachycardia, attenuated chronotropic baroreflex responses, and reduced heart rate variability were manifest within 1-4 days on high-fat intake, reaching 130 ± 4 beats per minute (bpm) (control = 86 ± 3 bpm) and ∼45% and <20%, respectively, of control levels. Subsequently, both baroreflex activation and renal denervation abolished the hypertension. However, only baroreflex activation effectively attenuated the tachycardia and restored cardiac baroreflex sensitivity and heart rate variability. These findings suggest that baroreflex activation therapy may reduce the risk factors for cardiac arrhythmias as well as lower arterial pressure.