Association of impaired baroreflex sensitivity and increased arterial stiffness in peritoneal dialysis patients

Baroreflex Sensitivity as a Surrogate Biomarker for Concurrently Assessing the Severity of Arterial Stiffness and Cardiovascular Autonomic Neuropathy in Individuals with Type 2 Diabetes

This study aimed to investigate whether baroreflex sensitivity (BRS) could serve as a reliable metric for assessing cardiovascular autonomic neuropathy (CAN) and concurrently act as a surrogate biomarker for evaluating the severity of arterial stiffness and CAN in individuals diagnosed with type 2 diabetes mellitus (T2DM). Participants underwent brachial-ankle pulse wave velocity (baPWV) as well as autonomic function evaluations encompassing the Sudoscan-based modified composite autonomic scoring scale (CASS), baroreflex sensitivity, and heart rate variability in time domains and frequency domains. Linear regression analysis was performed to evaluate the influence of independent variables on baPWV and modified CASS. Participants with higher baPWV values were older, with longer diabetes duration, lower body weight, body mass index, waist circumference, elevated systolic and diastolic blood pressure, and mean arterial blood pressure. They also exhibited a higher prevalence of retinopathy as the underlying disease and reduced estimated glomerular filtration rate. Multiple linear regression analysis revealed that age and BRS were significantly associated with baPWV while diabetes duration, UACR, and BRS were significantly associated with modified CASS. Our study confirms the significant association of BRS with baPWV and modified CASS in T2DM, highlighting its pivotal role in linking microvascular and macrovascular complications. This supports BRS as a surrogate marker for assessing both the severity of arterial stiffness and cardiovascular autonomic neuropathy in T2DM, enabling the early identification of complications.

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.

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.

A Novel Method for Baroreflex Sensitivity Estimation Using Modulated Gaussian Filter

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

Chronic Kidney Disease and Arterial Stiffness: A Two-Way Path

The kidney-heart relationship has raised interest for the medical population since its vast and complex interaction significantly impacts health. Chronic kidney disease (CKD) generates vascular structure and function changes, with significant hemodynamic effects. The early arterial stiffening in CKD patients is a consequence of the interaction between oxidative stress and chronic vascular inflammation, leading to an accelerated deterioration of left ventricular function and alteration in tissue perfusion. CKD amplifies the inflammatory cascade's activation and is responsible for altering the endothelium function, increasing the vascular tone, wall thickening, and favors calcium deposits in the arterial wall. Simultaneously, the autonomic imbalance, and alteration in other hormonal systems, also favor the overactivation of inflammatory and fibrotic mediators. Thus, hormonal disarrangement also contributes to structural and functional lesions throughout the arterial wall. On the other hand, a rise in arterial stiffening and volume overload generates high left ventricular afterload. It increases the left ventricular burden with consequent myocardial remodeling, development of left ventricular hypertrophy and, in turn, heart failure. It is noteworthy that reduction in glomerular mass of renal diseases generates a compensatory glomerular filtration overdriven associated with large-arteries stiffness and high cardiovascular events. Furthermore, we consider that the consequent alterations of the arterial system's mechanical properties are crucial for altering tissue perfusion, mainly in low resistance. Thus, increasing the knowledge of these processes may help the reader to integrate them from a pathophysiological perspective, providing a comprehensive idea of this two-way path between arterial stiffness and renal dysfunction and their impact at the cardiovascular level.

Sleep moderates the association between arterial stiffness and 24-hour blood pressure variability

BACKGROUND

Arterial stiffness and increased blood pressure variability (BPV) are important subclinical cardiovascular diseases (CVDs). Evidence is accumulating that poor sleep is associated with subclinical CVDs. The purpose of our study was to investigate how sleep was related to arterial stiffness and BPV. We also explored whether sleep moderated the association between arterial stiffness and BPV.

METHODS

We conducted a cross-sectional study including 78 healthy adults aged between 35 and 64 years. Variables of interest were: 1) objective seep characteristics, assessed with a wrist actigraphy for two consecutive nights; 2) arterial stiffness, measured by carotid-femoral pulse wave velocity (cfPWV); and 3) BPV, measured using an ambulatory blood pressure monitor over 24 h and estimated by average real variability.

RESULTS

Lower sleep efficiency was an independent predictor of higher cfPWV and higher systolic BPV, while longer wake after sleep onset (WASO) was an independent predictor of higher cfPWV only. In addition, cfPWV showed a positive relationship with systolic BPV, and this relationship was moderated by sleep efficiency and WASO, respectively. The relationship between cfPWV and systolic BPV became stronger among individuals who had a level of sleep efficiency lower than 84% and who had WASO higher than 67 min, respectively.

CONCLUSION

Our study showed that poor sleep not only directly linked with arterial stiffness and BPV but also moderated the relationship between these two subclinical CVDs. These findings suggest that improving sleep quality could be a target intervention to promote cardiovascular health in clinical practice.

Link Between Elevated Long-Term Resting Heart Rate Variability and Pulse Pressure Variability for All-Cause Mortality

Background

Elevated long‐term systolic blood pressure and resting heart rate (RHR) variability are suggested to amplify the risk of all‐cause mortality (ACM). However, the link between increased RHR and pulse pressure for ACM remained unclear.

Methods and Results

This study analyzed 46 751 individuals from Kailuan Cohort Study for the end outcome of ACM. A Cox regression model was used to estimate hazard ratios for death events. Kaplan‐Meier analysis was performed to study the differences in survival as stratified by the SD, coefficient of variation, and average real variability of RHR and pulse pressure quartiles. A total of 1667 deaths (<65 years of age=866/40351, ≥65 years of age=801/6400) were recorded over 4.97±0.69 years follow‐up. Participants under the age of 65 years in the third and fourth quartiles of pulse pressure SD had an independent increase in risk for ACM (hazard ratio [95% CI], 1.16 [1.06–1.28]; and 1.19 [1.05–1.35], respectively). Additionally, participants >65 years of age had a higher risk for ACM across quartiles of RHR‐SD. The hazard ratio (95% CI) for the subjects in quartiles 2, 3, and 4 were 1.81 (1.10–2.97), 2.31 (1.37–1.3.90), and 2.64 (1.63–4.29), respectively.

Conclusions

An elevated long‐term RHR variability combined with an increased pulse pressure variability or vice versa amplifies the risk of ACM.

Reduced Baroreflex Sensitivity, Decreased Heart Rate Variability with Increased Arterial Stiffness in Predialysis

High cardiovascular morbidity and mortality is observed in predialytic chronic kidney disease (CKD) patients. The underlying mechanism of cardiovascular dysfunction often remains unclear. The present study was designed to perform multiparametric assessment of baroreflex sensitivity (BRS), arterial stiffness indices, and cardiovascular variabilities (heart rate variability [HRV] and blood pressure variability [BPV]) together in predialytic CKD patients; compare it with normal healthy controls; and determine their relationships in predialytic nondiabetic CKD patients. Thirty CKD Stage 4 and 5 predialytic non-diabetic patients and 30 healthy controls were enrolled in the study. BRS was determined by spontaneous sequence method. Short-term HRV and BPV were assessed using 5 min beat-to-beat data of RR intervals and blood pressure by time domain and frequency domain analysis. Arterial stiffness indices - carotid-femoral pulse wave velocity (PWV) and augmentation index - were measured using SphygmoCor Vx device (AtCor Medical, Australia). Predialytic CKD patients had significantly low BRS, high PWV, and low HRV as compared to healthy controls. Independent predictors of reduced systolic BRS in predialytic CKD patient group on multiple regression analysis emerged to be increase in calcium-phosphate product, increase in BPV, and decrease in HRV. Predialytic nondiabetic CKD Stage 4 and 5 patients have poor hemodynamic profile (higher PWV, lower HRV, and reduced BRS) than healthy controls. Reduced HRV and altered calcium-phosphate homeostasis emerged to be significant independent predictors of reduced BRS.

Diabetic status and grade of nonalcoholic fatty liver disease are associated with lower baroreceptor sensitivity in patients with nonalcoholic fatty liver disease

OBJECTIVES

Baroreceptor sensitivity (BRS), a functional consequence of vascular stiffness, may be affected by the presence of diabetes mellitus (DM) and nonalcoholic fatty liver disease (NAFLD). The present study was designed to assess the effect of diabetic status and NAFLD grade on the BRS in patients with NAFLD.

METHODS

Seventy-five individuals (25 NAFLD without DM, 25 NAFLD with DM and 25 controls) were recruited for the study who underwent anthropometric and body composition analysis along with estimation of plasma glucose, serum insulin and serum lipids. BRS and blood pressure variability (BPV) analysis was carried out in both time and frequency domains. Carotid-radial and carotid-dorsalis pedis artery pulse wave velocity, and radial artery augmentation index were computed as measures of arterial stiffness.

RESULTS

BRS was found to be lower in the NAFLD with DM group as well those with grade II NAFLD compared with the controls. Correlation analysis showed a negative correlation of BRS with postprandial blood glucose level (r=-0.39) and BMI (r=-0.467). The diabetic status and grade of NAFLD were associated independently with a decrease in BRS as well as the low-frequency component of diastolic BPV. The augmentation index and carotid-distal pulse wave velocity were higher in the NAFLD with DM group compared with controls.

CONCLUSION

Both the diabetic status and grade of NAFLD were shown to have an independent effect on the decrease in the BRS with a consequent effect on BPV, with a greater influence of diabetic status rather than NAFLD grade on arterial stiffness.

Improved Methods to Produce Tissue-Engineered Skin Substitutes Suitable for the Permanent Closure of Full-Thickness Skin Injuries

There is a clinical need for skin substitutes to replace full-thickness skin loss. Our group has developed a bilayered skin substitute produced from the patient's own fibroblasts and keratinocytes referred to as Self-Assembled Skin Substitute (SASS). After cell isolation and expansion, the current time required to produce SASS is 45 days. We aimed to optimize the manufacturing process to standardize the production of SASS and to reduce production time. The new approach consisted in seeding keratinocytes on a fibroblast-derived tissue sheet before its detachment from the culture plate. Four days following keratinocyte seeding, the resulting tissue was stacked on two fibroblast-derived tissue sheets and cultured at the air–liquid interface for 10 days. The resulting total production time was 31 days. An alternative method adapted to more contractile fibroblasts was also developed. It consisted in adding a peripheral frame before seeding fibroblasts in the culture plate. SASSs produced by both new methods shared similar histology, contractile behavior in vitro and in vivo evolution after grafting onto mice when compared with SASSs produced by the 45-day standard method. In conclusion, the new approach for the production of high-quality human skin substitutes should allow an earlier autologous grafting for the treatment of severely burned patients.

Estimated aortic stiffness is independently associated with cardiac baroreflex sensitivity in humans: role of ageing and habitual endurance exercise

We hypothesized that differences in cardiac baroreflex sensitivity (BRS) would be independently associated with aortic stiffness and augmentation index (AI), clinical biomarkers of cardiovascular disease (CVD) risk, among young sedentary and middle-aged/older sedentary and endurance-trained adults. A total of 36 healthy middle-aged/older (age 55-76 years, n=22 sedentary; n=14 endurance-trained) and 5 young sedentary (age 18-31 years) adults were included in a cross-sectional study. A subset of the middle-aged/older sedentary adults (n=12) completed an 8-week aerobic exercise intervention. Invasive brachial artery blood pressure waveforms were used to compute spontaneous cardiac BRS (via sequence technique) and estimated aortic pulse wave velocity (PWV) and AI (AI, via brachial-aortic transfer function and wave separation analysis). In the cross-sectional study, cardiac BRS was 71% lower in older compared with young sedentary adults (P<0.05), but only 40% lower in older adults who performed habitual endurance exercise (P=0.03). In a regression model that included age, sex, resting heart rate, mean arterial pressure (MAP), body mass index and maximal exercise oxygen uptake, estimated aortic PWV (β±SE = −5.76 ± 2.01, P=0.01) was the strongest predictor of BRS (Model R²=0.59, P<0.001). The 8 week exercise intervention improved BRS by 38% (P=0.04) and this change in BRS was associated with improved aortic PWV (r=−0.65, P=0.044, adjusted for changes in MAP). Age- and endurance exercise-related differences in cardiac BRS are independently associated with corresponding alterations in aortic PWV among healthy adults, consistent with a mechanistic link between variations in the sensitivity of the baroreflex and aortic stiffness with age and exercise.