Renal transplantation normalizes baroreflex sensitivity through improvement in central arterial stiffness

Baroreflex sensitivity is impaired in survivors of mild COVID-19 at 3-6 months of clinical recovery; association with carotid artery stiffness

The association between the stiffening of barosensitive regions of central arteries and the derangements in baroreflex functions remains unexplored in COVID-19 survivors. Fifty-seven survivors of mild COVID-19 (defined as presence of upper respiratory tract symptoms and/or fever without shortness of breath or hypoxia; SpO2 > 93%), with an age range of 22-66 years (27 females) participated at 3-6 months of recovering from the acute phase of RT-PCR positive COVID-19. Healthy volunteers whose baroreflex sensitivity (BRS) and arterial stiffness data were acquired prior to the onset of the pandemic constituted the control group. BRS was found to be significantly lower in the COVID survivor group for the systolic blood pressure-based sequences (BRSSBP ) [9.78 (7.16-17.74) ms/mmHg vs 16.5 (11.25-23.78) ms/mmHg; p = 0.0253]. The COVID survivor group showed significantly higher carotid β stiffness index [7.16 (5.75-8.18) vs 5.64 (4.34-6.96); (p = 0.0004)], and pulse wave velocity β (PWVβ ) [5.67 (4.96-6.32) m/s vs 5.12 (4.37-5.41) m/s; p = 0.0002]. BRS quantified by both the sequence and spectral methods showed an inverse correlation with PWVβ in the male survivors. Impairment of BRS in the male survivors of mild COVID-19 at 3-6 months of clinical recovery shows association with carotid artery stiffness.

Baroreceptor Sensitivity in Individuals with CKD and Heart Failure

Background

Heart failure is the most common cardiovascular complication of chronic kidney disease (CKD) and foreshadows a high morbidity and mortality rate. Baroreflex impairment likely contributes to cardiovascular mortality. We aimed to study the associations between CKD, heart failure, and baroreflex sensitivity (BRS) and their association with cardiovascular outcomes.

Methods

We retrospectively analyzed data from a cohort of 247 individuals with moderate to severe HF. All subjects underwent BRS measurements after intravenous phenylephrine along with electrocardiography, echocardiography, and laboratory measurements. We used logistic regression models to assess the association of CKD (estimated glomerular filtration rate <60 ml/min per 1.73 m²) with BRS using iterative models. Cox proportional hazards models were used to assess associations of binary BRS and subgroups according to categorizations of CKD and BRS with cardiovascular mortality.

Results

Median eGFR among individuals with CKD was 52 (IQR 44-56) ml/min per 1.73 m². eGFR was lower in those with depressed BRS (65 [IQR 54-76] ml/min per 1.73 m²) compared with those with preserved BRS (73 [IQR 64-87] ml/min per 1.73 m²; P≤0.001). The majority of individuals with CKD had depressed BRS compared with those without CKD (60% versus 29%; P=0.05). In regression models, CKD and BRS were independently associated. Cardiovascular mortality was significantly increased in individuals with or without CKD and depressed BRS compared with those with preserved BRS and CKD.

Conclusions

Cardiac BRS is depressed in patients with mild to moderate CKD and HF and associated with cardiovascular mortality. Additional study to confirm its contribution to cardiovascular mortality, particularly in advanced CKD, is warranted.

Peripapillary Vascular Density Measurement in Pediatric Renal and Liver Transplant

OBJECTIVES

Noninvasive monitorization of retinal structures of the eye could be a predictor for systemic microvasculature dysfunction in transplant recipients. In this study, our purpose was to determine the optic disc and peripapillary microvascular changes in pediatric patients who had undergone liver or renal transplant surgery.

MATERIALS AND METHODS

The study was performed at Başkent University. The medical records were reviewed, and patients who had liver or renal transplant in the last 10 years and were between 4 and 18 years old were included in the study. The optic disc and peripapillary vascular density parameters were obtained by optical coherence tomography angiography (Avanti RTVue XR). The results were compared with the results from age-matched, sex-matched, and spherical equivalent-matched healthy subjects.

RESULTS

Our study included 32 eyes of 16 liver transplant patients, 20 eyes of 10 renal transplant patients, and 64 eyes of 32 healthy participants (control). Whole image peripapillary, inside disc, peripapillary, superior and inferior hemisphere, and superior, inferior, temporal, and nasal quadrant peripapillary vascular densities were evaluated. No statistically significant differences in any parameter were noted between the healthy control group and the patient groups (P > .05 for all parameters).

CONCLUSIONS

Peripapillary vascular density measurements were not affected in pediatric renal and liver transplant patients.

Impact of kidney transplantation on aortic stiffness and aortic stiffness index β0

BACKGROUND

In chronic kidney disease, the enhanced aortic stiffness increases risk of cardiovascular events. Kidney transplantation (KTx) may improve aortic stiffness; however, it is unclear whether the improvement of aortic stiffness is merely the outcome of the reduction of blood pressure (BP) post-KTx. Furthermore, the long-term trajectory of aortic stiffness remains uncertain, as activation of the immune system may have a negative long-term impact on arterial wall property.

METHOD

Using aortic stiffness β0 as a BP-independent stiffness parameter, and a statistical adjustment for BP, we aimed to examine the early vs. late changes in aortic stiffness, and to define the characteristics of patients with favourable and unfavourable long-term trajectories of aortic stiffness. In this longitudinal study, aortic stiffness was assessed before, 3, 6 and 24 months after KTx in 79 individuals. Aortic stiffness was determined by carotid-femoral pulse wave velocity (cf-PWV), and aortic stiffness index β0 was obtained by applying the stiffness parameter β0 theory to cf-PWV based on Bramwell-Hill's equation using a reference pressure.

RESULTS

There was an early reduction of β0 3 months after KTx (29.0 ± 2.0 to 25.8 ± 1.2, P = 0.033) followed by a gradual increase at 6 (28.0 ± 1.4, P = 0.005 vs. 3 months) and 24 months (28.3 ± 1.3, P = 0.003 vs. 3 months). A late increase in β0 was associated with higher levels of the interleukin-6 (P = 0.029) even after adjustment for potential cofounders. Using statistical adjustments for BP showed similar results.

CONCLUSION

Reduction of aortic stiffness index β0 3 months after KTx suggests that KTx leads to an early de-stiffening of the intrinsic mechanical properties of aorta. However, this improvement is followed by a later stiffening, which is associated with increased interleukin-6, suggesting that activation of the immune system may be involved in arterial wall remodelling in kidney recipients.

Depressed baroreflex sensitivity from spontaneous oscillations of heart rate and blood pressure in SCA1 and SCA2

OBJECTIVES

To assess the time and frequency domain measures of cardiac autonomic activity/tone in patients of genetically defined spinocerebellar ataxia (SCA) types 1 and 2, as well as to decipher the probable associations among the cardiovascular autonomic parameters and genetic and clinical characteristics.

MATERIALS AND METHODS

Simultaneous 5-min recording of RR interval (RRI) and blood pressure (BP) for the calculation of heart rate variability (HRV), blood pressure variability (BPV) and baroreflex sensitivity (BRS) were performed in genotypically confirmed SCA1 (n = 31) and SCA2 (n = 40) patients and healthy controls (n = 40). Additionally, the International Cooperative Ataxia Rating Scale (ICARS) was used for scoring of clinical severity in SCA patients.

RESULTS

Time and frequency domain parameters of HRV, BPV and BRS were depressed in SCA1 and SCA2 subtypes as compared to controls, although there was no statistically significant difference in autonomic tone between the two SCA subtypes. On correlation analysis, autonomic tone parameters were found to be associated with the clinical and genetic features of the SCA subtypes. Also, ICARS was associated with the genotype (CAG repeat length) in SCA2 patents.

CONCLUSIONS

Cardiac autonomic tone is depressed in both SCA1 and 2 as compared to healthy controls while the two SCA subtypes do not differ in terms of autonomic tone. Also, a typical association exists between disease characteristics and autonomic indices.

Arterial Stiffness in Patients With Renal Transplantation; Associations With Co-morbid Conditions, Evolution, and Prognostic Importance for Cardiovascular and Renal Outcomes

Patients with chronic kidney disease (CKD), particularly those with end-stage renal disease (ESRD), are at increased risk of cardiovascular events and mortality. The spectrum of arterial remodeling in CKD and ESRD includes atheromatosis of middle-sized conduit arteries and, most importantly, the process of arteriosclerosis, characterized by increased arterial stiffness of aorta and the large arteries. Longitudinal studies showed that arterial stiffness and abnormal wave reflections are independent cardiovascular risk factors in several populations, including patients with CKD and ESRD. Kidney transplantation is the treatment of choice for patients with ESRD, associated with improved survival and better quality of life in relation to hemodialysis or peritoneal dialysis. However, cardiovascular mortality in transplanted patients remains much higher than that in general population, a finding that is at least partly attributed to adverse lesions in the vascular tree of these patients, generated during the progression of CKD, which do not fully reverse after renal transplantation. This article attempts to provide an overview of the field of arterial stiffness in renal transplantation, discussing in detail available studies on the degree and the associations of arterial stiffness with other co-morbidities in renal transplant recipients, the prognostic significance of arterial stiffness for cardiovascular events, renal events and mortality in these individuals, as well as studies examining the changes in arterial stiffness following renal transplantation.

Reduction of Arterial Stiffness After Kidney Transplantation: A Systematic Review and Meta-Analysis

Background

End‐stage kidney disease is associated with increased arterial stiffness. Although correction of uremia by kidney transplantation (KTx) could improve arterial stiffness, results from clinical studies are unclear partly due to small sample sizes.

Method and Results

We conducted a systematic review and meta‐analysis of before‐after design studies performed in adult KTx patients with available measures of arterial stiffness parameters (pulse wave velocity [PWV], central pulse pressure [PP], and augmentation index) before and at any time post‐KTx. Mean difference of post‐ and pre‐KTx values of different outcomes were estimated using a random effect model with 95% confidence interval. To deal with repetition of measurement within a study, only 1 period of measurement was considered per study by analysis. Twelve studies were included in meta‐analysis, where a significant decrease of overall PWV by 1.20 m/s (95% CI 0.67‐1.73, I²=72%), central PWV by 1.20 m/s (95% CI 0.16‐2.25, I²=83%), peripheral PWV by 1.17 m/s (95% CI 0.17‐2.17, I²=79%), and brachial‐ankle PWV by 1.21 m/s (95% CI 0.66‐1.75, I²=0%) was observed. Central PP (reported in 4 studies) decreased by 4.75 mm Hg (95% CI 0.78–10.28, I²=50%). Augmentation index (reported in 7 studies) decreased by 10.5% (95% CI 6.9‐14.1, I²=64%). A meta‐regression analysis showed that the timing of assessment post‐KTx was the major source of the residual variance.

Conclusions

This meta‐analysis suggests a reduction of the overall arterial stiffness in patients with end‐stage kidney disease after KTx.

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.

Decreased Spontaneous Baroreflex Sensitivity as an Early Marker for Progression of Haemorrhage

INTRODUCTION

Blood donation provides an ideal setup for assessment of cardiovascular responses to mild hypovolemia for understanding the underlying mechanisms.

AIM

To evaluate cardiovascular responses in time and magnitude by estimating the spontaneous baroreflex sensitivity (BRS) during and after donation of 450 ml of blood.

METHODS

Continuous beat-to-beat blood pressure and lead II ECG was recorded before, during and after blood donation in 54 healthy volunteers (age 34.7 ± 5.08 years; weight 77.9 ± 8.20 kg), followed by offline analyses of baroreflex sensitivity.

RESULTS

The systolic, diastolic or mean blood pressures did not change during or after the blood donation. Decrease in pulse pressure and increase in heart rate was observed post donation. The spontaneous BRS decreased during [8.68 (6.038-12.69) ms/mmHg] and after blood donation [9.401 (6.396-11.59) ms/mmHg] as compared to the baseline [12.83 (6.884-18.18) ms/mmHg] with a significant decrease in α-HF on spectral analysis.

CONCLUSION

Mild blood loss (450 ml) results in non-hypotensive haemorrhage with a decrease in spontaneous BRS before the rise of heart rate during blood donation.

Cardiac and vascular changes with kidney transplantation

Cardiovascular event rates are high in patients with chronic kidney disease (CKD), increasing with deteriorating kidney function, highest in CKD patients on dialysis, and improve with kidney transplantation (KTx). The cardiovascular events in CKD patients such as myocardial infarction and heart failure are related to abnormalities of vascular and cardiac structure and function. Many studies have investigated the structural and functional abnormalities of the heart and blood vessels in CKD, and the changes that occur with KTx, but the evidence is often sparse and occasionally contradictory. We have reviewed the available evidence and identified areas where more research is required to improve the understanding and mechanisms of these changes. There is enough evidence demonstrating improvement of left ventricular hypertrophy, except in children, and sufficient evidence of improvement of left ventricular function, with KTx. There is reasonable evidence of improvement in vascular function and stiffness. However, the evidence for improvement of vascular structure and atherosclerosis is insufficient. Further studies are necessary to establish the changes in vascular structure, and to understand the mechanisms of vascular and cardiac changes, following KTx.

Cardiovascular Autonomic Dysfunction in Patients of Nonalcoholic Fatty Liver Disease

Aim. The present study was designed to evaluate the heart rate variability (HRV) in nonalcoholic fatty liver disease (NAFLD) and to assess the effect of grade of NAFLD and diabetic status on HRV. Methods. This cross-sectional study included 75 subjects (25 NAFLD without diabetes, 25 NAFLD with diabetes, and 25 controls). Measurements included anthropometry, body composition analysis, estimation of plasma glucose, serum lipids, hsCRP, and serum insulin. HRV analysis was performed in both time and frequency domains. Results. The time and frequency domain indices of overall variability (SDNN, total power) were significantly lower in NAFLD with diabetes as compared to the controls. However, the LF : HF ratio did not differ among the three groups. The variables related to obesity, lipid profile, and glucose metabolism were also higher in NAFLD with diabetes and those with Grade II NAFLD without diabetes, as compared to controls. Multivariate stepwise regression analysis showed a negative correlation between HRV and total cholesterol and fat percentage. Conclusion. The grade of NAFLD as well as diabetic status contributes to the decrease in the cardiovascular autonomic function, with diabetic status rather than grade of NAFLD playing a critical role. Serum lipids and adiposity may also contribute to cardiac autonomic dysfunction.

Vascular calcification, bone and mineral metabolism after kidney transplantation

The development of end stage renal failure can be seen as a catastrophic health event and patients with this condition are considered at the highest risk of cardiovascular disease among any other patient groups and risk categories. Although kidney transplantation was hailed as an optimal solution to such devastating disease, many issues related to immune-suppressive drugs soon emerged and it became evident that cardiovascular disease would remain a vexing problem. Progression of chronic kidney disease is accompanied by profound alterations of mineral and bone metabolism that are believed to have an impact on the cardiovascular health of patients with advanced degrees of renal failure. Cardiovascular risk factors remain highly prevalent after kidney transplantation, some immune-suppression drugs worsen the risk profile of graft recipients and the alterations of mineral and bone metabolism seen in end stage renal failure are not completely resolved. Whether this complex situation promotes progression of vascular calcification, a hall-mark of advanced chronic kidney disease, and whether vascular calcifications contribute to the poor cardiovascular outcome of post-transplant patients is reviewed in this article.

Pathophysiological contribution of vascular function to baroreflex regulation in hypertension

BACKGROUND

We examined which pathophysiological abnormalities of vascular function might be closely associated with abnormal baroreflex regulation in subjects with hypertension.

METHODS AND RESULTS

In the cross-sectional assessment, 280 subjects with hypertension were enrolled for measurement of brachial-ankle pulse wave velocity (baPWV), radial augmentation index (rAI), flow-mediated vasodilatation (FMD) of the brachial artery and baroreceptor sensitivity (BRS). These parameters were measured again as prospective assessment in some of these subjects. In the cross-sectional assessment, after adjustment for confounding variables including anti-hypertensive medication, the baPWV, but not the rAI or FMD, was found to have a significant independent relationship with BRS (standardization coefficient, -0.149, P<0.043). In the subjects who were newly started on anti-hypertensive medication (n=40), regression of baPWV before and 1 year after the start of medication was significantly associated with change in BRS during the same period. In subjects already on anti-hypertensive medication (n=92) also, the evolutional change of baPWV over a follow-up period >1.5 years was significantly associated with change in BRS during the same period.

CONCLUSIONS

Increased stiffness of the large- to middle-sized arteries, rather than abnormal central hemodynamics or endothelial dysfunction, appears to contribute to abnormal baroreflex regulation in patients with hypertension.

Renal transplantation normalizes baroreflex sensitivity through improvement in central arterial stiffness

BACKGROUND

In end-stage renal disease (ESRD) patients, the most common cause of mortality and morbidity are cardiovascular events. This could be attributed to the impaired baroreflex function observed in this group of patients. The effect of renal transplantation (RT) on the baroreflex sensitivity (BRS) in ESRD patients has been inadequately addressed. Therefore, we investigated baroreflex function and its relation to arterial stiffness indices and cardiovascular variability parameters (heart rate and blood pressure variability--HRV and BPV) in ESRD patients before and after transplantation to decipher the underlying mechanism of attenuated BRS in ESRD patients.

METHODS

We studied 23 ESRD patients (mean age; 36 years) prospectively before and at 3 and 6 months after RT. Baroreflex function was determined by spontaneous method (sequence and spectral indices). Short-term HRV and BPV were assessed using power spectrum analysis of RR intervals and systolic blood pressure by frequency domain analysis. Arterial stiffness indices were assessed by carotid-femoral pulse-wave velocity (PWV), augmentation index (AI) and central pulse pressure using Sphygmocor Vx device (AtCor Medical, Australia).

RESULTS

RT was associated with the normalization of BRS by 6 months. Arterial stiffness indices, such as AI and central pulse pressure, showed a significant reduction as early as 3 months after RT. PWV and frequency domain measures of HRV after RT did not show statistically significant changes except the LF/HF ratio which had a significant increase at 6 months when compared with baseline. Systolic BPV total power showed a significant reduction by 3 months after RT.

CONCLUSIONS

Our data suggest that RT normalizes BRS in ESRD patients by 6 months which follows the improvement in the AI and central pulse pressure.