Can Kidney Transplantation Improve Arterial Stiffness in End-Stage Renal Patients?

Indoxyl Sulphate Retention Is Associated with Microvascular Endothelial Dysfunction after Kidney Transplantation

Kidney transplantation (KTx) is the preferred form of renal replacement therapy in chronic kidney disease (CKD) patients, owing to increased quality of life and reduced mortality when compared to chronic dialysis. Risk of cardiovascular disease is reduced after KTx; however, it is still a leading cause of death in this patient population. Thus, we aimed to investigate whether functional properties of the vasculature differed two years post-KTx (postKTx) compared to baseline (time of KTx). Using the EndoPAT device in 27 CKD patients undergoing living-donor KTx, we found that vessel stiffness significantly improved while endothelial function worsened postKTx vs. baseline. Furthermore, baseline serum indoxyl sulphate (IS), but not p-cresyl sulphate, was independently negatively associated with reactive hyperemia index, a marker of endothelial function, and independently positively associated with P-selectin postKTx. Finally, to better understand the functional effects of IS in vessels, we incubated human resistance arteries with IS overnight and performed wire myography experiments ex vivo. IS-incubated arteries showed reduced bradykinin-mediated endothelium-dependent relaxation compared to controls via reduced nitric oxide (NO) contribution. Endothelium-independent relaxation in response to NO donor sodium nitroprusside was similar between IS and control groups. Together, our data suggest that IS promotes worsened endothelial dysfunction postKTx, which may contribute to the sustained CVD risk.

Arterial Stiffness in Renal Transplant Recipients: 5-Year Follow-up

BACKGROUND

Chronic kidney disease is a risk factor for cardiovascular diseases. After renal transplant, some traditional and chronic kidney disease-specific risk factors vanish, but new risk factors emerge. This retrospective study aimed to define the long-term impact of renal transplant and diabetes mellitus on arterial stiffness, evaluated by measuring pulse wave velocity (PWV) and augmentation index (AI) and on myocardial perfusion, evaluated by subendocardial viability ratio (SEVR).

METHODS

PWV, AI, and SEVR were evaluated noninvasively by applanation tonometry using SphygmoCor in the first 4 weeks after kidney transplant and 4 to 5 years thereafter.

RESULTS

A total of 48 graft recipients (18 women, 30 men; mean ± standard deviation age, 47.9 ± 11.8 years) were included. The follow-up period was 57.4 ± 8.0 months. PWV did not change significantly during the follow-up period (9.1 ± 1.8m/s and 8.7 ± 1.8m/s, respectively; P = .137). In the subgroup of patients without diabetes mellitus, we observed a trend of PWV reduction, whereas in the subgroup of patients with diabetes we observed the trend of PWV increase. The duration of smoking before transplant correlated significantly with PWV (P = .012). AI in the whole group increased significantly during the study period (from 18.3% ±10.3% to 25.9% ±9.4%; P < .01) as well as SEVR (from 134.9 ± 23.1 to 155.4 ± 28.6; P = .001).

CONCLUSIONS

PWV, reflecting the central vessel stiffness, did not change significantly in the whole group during the follow-up period. The AI, which indicates systemic stiffness, increased significantly within 5 years after transplant, indicating the progression of vascular processes of elastic and muscular arteries. Significant increases in the SEVR values in both diabetics and nondiabetics indicate the long-term favorable effect of kidney transplant on myocardial perfusion.

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.

Obesity, Fat Tissue Parameters, and Arterial Stiffness in Renal Transplant Recipients

OBJECTIVE

Arterial stiffness and altered body composition (increased body fat mass [BFM] and decreased lean body mass) are acknowledged risk factors for adverse outcomes after kidney transplantation related to cardiovascular diseases. The aim of the study was the assessment of the relationship between arterial stiffness and fat tissue parameters in renal transplants recipients (RTrs).

METHODS

A group of 344 RTrs with stable disease and a mean age of 52.7 years (62.5% men) who underwent transplantation between 1994 and 2018 were randomly enrolled in the study. The following parameters of arterial stiffness were measured: brachial-ankle and carotid-femoral pulse waves velocities (baPWVs left and right, cfPWVs). The obesity and fat tissue (body mass index [BMI], waist-to-hip ratio [WHR], BFM, fat free mass [FFM], percent body fat [PBF], trunk segmental fat analysis [TSFA], and visceral fat area [VFA]) parameters were assessed with InBody 170.

RESULTS

The median time of dialysis and after kidney transplantation was 58.5 and 78 months, respectively. Obesity according BMI, WHR, and VFA was diagnosed in 49.7%, 45.0%, and 44.5% of patients, respectively. The median value of BFM, FFM, VFA, and TSFA and the mean value of PBF were 19.3 kg, 55 kg, 93.2 cm², 24.9 kg, and 27.3%, respectively. We found significant positive correlations among WHR, VFA, baPWV right, baPWV left, and cfPWV.

CONCLUSIONS

Obesity and visceral fat tissue influence on arterial stiffness. The analysis of magnitude of obesity and body fat tissue parameters can be used as an additional cardiovascular risk factor in RTrs.

KDIGO Clinical Practice Guideline on the Evaluation and Management of Candidates for Kidney Transplantation

The 2020 Kidney Disease: Improving Global Outcomes (KDIGO) Clinical Practice Guideline on the Evaluation and Management of Candidates for Kidney Transplantation is intended to assist health care professionals worldwide who evaluate and manage potential candidates for deceased or living donor kidney transplantation. This guideline addresses general candidacy issues such as access to transplantation, patient demographic and health status factors, and immunological and psychosocial assessment. The roles of various risk factors and comorbid conditions governing an individual's suitability for transplantation such as adherence, tobacco use, diabetes, obesity, perioperative issues, causes of kidney failure, infections, malignancy, pulmonary disease, cardiac and peripheral arterial disease, neurologic disease, gastrointestinal and liver disease, hematologic disease, and bone and mineral disorder are also addressed. This guideline provides recommendations for evaluation of individual aspects of a candidate's profile such that each risk factor and comorbidity are considered separately. The goal is to assist the clinical team to assimilate all data relevant to an individual, consider this within their local health context, and make an overall judgment on candidacy for transplantation. The guideline development process followed the Grades of Recommendation Assessment, Development, and Evaluation (GRADE) approach. Guideline recommendations are primarily based on systematic reviews of relevant studies and our assessment of the quality of that evidence, and the strengths of recommendations are provided. Limitations of the evidence are discussed with differences from previous guidelines noted and suggestions for future research are also provided.

Influence of Renal Transplantation and Living Kidney Donation on Large Artery Stiffness and Peripheral Vascular Resistance

BACKGROUND

Vascular status following renal transplantation (RT) may improve while living kidney donation (LKD) is possibly associated with an increased cardiovascular risk.

METHODS

We prospectively assessed glomerular filtration rate (mGFR, 51Chrome EDTA clearance) and intermediate vascular risk factors in terms of blood pressure (BP), pulse wave velocity (PWV), central augmentation index (AIx), excess pressure (Pexcess), and forearm vascular resistance in donors (n = 58, 45 ± 13 years) and recipients (n = 51, 50 ± 12 years) before and one year following LKD or RT.

RESULTS

After kidney donation, mGFR decreased by 33% to 65 ± 11 ml/min/1.73m2, while recipients obtained a mGFR of 55 ± 9 ml/min/1.73m.2 Ambulatory 24-hour mean arterial BP (MAP) remained unchanged in donors but decreased by 5 mm Hg in recipients (P < 0.05). Carotid-femoral PWV increased by 0.3 m/s in donors (P < 0.05) but remained unchanged in recipients. AIx was unaltered after LKD but decreased following RT (P < 0.01), and Pexcess did not change in either group. Resting forearm resistance (Rrest), measured by venous occlusion plethysmography, increased after LKD (P < 0.05) but was unaffected by RT, while no changes were seen in minimum resistance (Rmin). ΔPWV showed a positive linear association to Δ24-hour MAP in both groups. Multiple linear regression analysis (adjusting for age, gender, and the baseline value of the studied parameter) did not detect independent effects of graft function on 24-hour MAP, PWV, AIx, vascular resistance, or Pexcess, whereas low post-donation GFR was related to higher AIx and Rrest.

CONCLUSIONS

RT reduced BP and AIx without affecting PWV, whereas LKD resulted in increased PWV and Rrest, despite unchanged BP.

Positive correlation of serum fibroblast growth factor 23 with peripheral arterial stiffness in kidney transplantation patients

BACKGROUND

Fibroblast growth factor 23 (FGF-23) has a role in arterial stiffness (AS) apart from regulating mineral metabolism. We investigated the association between FGF-23 concentration and peripheral AS in renal transplantation (RT) recipients.

METHODS

The fasting blood samples of RT recipients (n = 66) were collected and analyzed.

RESULTS

A total of 29 (43.9%) RT recipients were classified under the peripheral AS group. The RT recipients in this group had a higher prevalence of diabetes (P < 0.001), hypertension (P = 0.001), and metabolic syndrome (P = 0.023); longer post-RT duration (P = 0.006); higher systolic blood pressure (P < 0.001) and diastolic blood pressure (P = 0.024); and higher fasting glucose (P = 0.002), total cholesterol (P = 0.049), blood urea nitrogen (P = 0.027), phosphorus (P = 0.047), and FGF-23 concentrations (P = 0.003) and FGF-23/α-klotho ratio (P < 0.001) but lower klotho concentrations (P = 0.025) than those in the control group. Moreover, FGF-23 concentration (adjusted odds ratio: 1.057, 95% confidence interval: 1.011-1.105, P = 0.015) was found to be an independent predictor of peripheral AS in RT recipients.

CONCLUSIONS

Serum FGF-23 concentration was a significant predictor of peripheral AS in RT recipients.

Kidney transplantation improves arterial stiffness in patients with end-stage renal disease

BACKGROUND

Cardiovascular disease (CVD) is the leading cause of mortality among the patients with end-stage renal disease (ESRD). Arterial stiffness is a well-accepted predictor of cardiovascular mortality in general population and ESRD patients. The aim of this study was to compare the change of arterial stiffness in kidney transplant recipients (KTRs) and ESRD patients, and further investigate the impact of kidney transplantation (KT) on arterial stiffness.

METHODS

A total of 138 maintenance hemodialysis patients, 198 KTRs and 75 healthy volunteers were enrolled in this study. The carotid-femoral pulse wave velocity (CF-PWV) and carotid-radial PWV (CR-PWV) were determined, and the correlations of PWV with biochemical parameters were analyzed.

RESULTS

CF-PWV was highest in the maintenance hemodialysis patients, but similar between KTRs and healthy volunteers. Bivariate correlation analysis among KTRs demonstrated that CF-PWV was positively correlated with high level of peripheral diastolic blood pressure, pulse pressure, mean artery pressure, BUN and HDL, but negatively correlated with albumin. Univariate polytomous logistic regression analysis showed that age, BMI, systolic blood pressure, pulse pressure, length of KT and BUN were associated with the increase of CF-PWV value.

CONCLUSIONS

Aortic stiffness could be improved after KT. Meanwhile, age, BMI, systolic blood pressure, pulse pressure, length of KT and BUN were independent predictors of the increase of CF-PWV in KTRs.

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.

Comparative Analysis of Arterial Stiffness and Body Composition in Early and Late Periods After Kidney Transplantation

INTRODUCTION

Diseases of the cardiovascular system are the most common cause of death in patients after kidney transplantation (KTx). Pulse wave velocity (PWV) measurement is a simple, noninvasive, and increasingly popular method to assess arterial stiffness, and thus to assess cardiovascular risk. The aim of the study was to compare arterial stiffness and body composition in patients after KTx in the early and late postoperative periods.

METHODS

This research was carried out from January to November 2017 at two locations: (1) Department and Clinic of General and Transplant Surgery and (2) Nephrology and Transplantology Clinic Medical University of Warsaw, the Infant Jesus Teaching Hospital, Warsaw, Poland. The study group consisted of 30 patients in the early postoperative period (2-7 postoperative days) and 151 patients in the late period (6 months to 27 years) after KTx. A single blood pressure measurement, PWV, was performed using a Schiller BR-102 plus PWV. Body composition analysis was performed using a Tanita MC-780 device.

RESULTS

The average PWV for patients in the early period after KTx was 8.02 ± 2.21 m/s and in the late period 8.09 ± 1.68 m/s. Positive correlations were found between adipose tissue in the abdominal cavity (R = 0.444, P = .033) and PWV value. There was no correlation between the values of PWV and time after transplantation (R = 0.034, P = .777). Upon analyzing patients after transplantation and taking into account the type of dialysis therapy, lower systolic blood pressure (142 ± 21 mm Hg vs 156 ± 24 mm Hg) and diastolic blood pressure (84 ± 13 mm Hg vs 98 ± 11 mm Hg) values were observed in patients treated with hemodialysis compared with those treated with peritoneal dialysis.

CONCLUSION

Using PWV measurement, we found that arterial stiffness levels were similar for early and late periods after 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.