Hypertension in Chronic Kidney Disease: The Influence of Renal Transplantation

Amiloride evokes significant natriuresis and weight loss in kidney transplant recipients with and without albuminuria

Albuminuria in kidney transplant recipients (KTRs) is associated with hypertension and aberrant glomerular filtration of serine proteases that may proteolytically activate the epithelial Na+ channel (ENaC). The present nonrandomized, pharmacodynamic intervention study aimed to investigate if inhibition of ENaC increases Na+ excretion and reduces extracellular volume in KTRs dependent on the presence of albuminuria. KTRs with and without albuminuria (albumin-to-creatinine ratio > 300 mg/g, n = 7, and <30 mg/g, n = 7, respectively) were included and ingested a diet with fixed Na+ content (150 mmol/day) for 5 days. On the last day, amiloride at 10 mg was administered twice. Body weight, 24-h urine electrolyte excretion, body water content, and ambulatory blood pressure as well as plasma renin, angiotensin II, and aldosterone concentrations were determined before and after amiloride. Amiloride led to a significant decrease in body weight, increase in 24-h urinary Na+ excretion, and decrease in 24-h urinary K+ excretion in both groups. Urine output increased in the nonalbuminuric group only. There was no change in plasma renin, aldosterone, and angiotensin II concentrations after amiloride, whereas a significant decrease in nocturnal systolic blood pressure and increase in 24-h urine aldosterone excretion was observed in albuminuric KTRs only. There was a significant correlation between 24-h urinary albumin excretion and amiloride-induced 24-h urinary Na+ excretion. In conclusion, ENaC activity contributes to Na+ and water retention in KTRs with and without albuminuria. ENaC is a relevant pharmacological target in KTRs; however, larger and long-term studies are needed to evaluate whether the magnitude of this effect depends on the presence of albuminuria.NEW & NOTEWORTHY Amiloride has a significant natriuretic effect in kidney transplant recipients (KTRs) that relates to urinary albumin excretion. The epithelial Na+ channel may be a relevant direct pharmacological target to counter Na+ retention and hypertension in KTRs. Epithelial Na+ channel blockers should be further investigated as a mean to mitigate Na+ and water retention and to potentially obtain optimal blood pressure control in KTRs.

Sex differences in ambulatory blood pressure levels, control, and phenotypes of hypertension in kidney transplant recipients

OBJECTIVES

Ambulatory blood pressure (BP) control is worse in men compared with women with chronic kidney disease (CKD) and this may partially explain the faster CKD progression in men. This is the first study investigating possible sex differences in prevalence, control and phenotypes of hypertension in kidney transplant recipients (KTRs) with office-BP and 24-h ambulatory BP monitoring (ABPM).

METHODS

This cross-sectional study included 136 male and 69 female stable KTRs who underwent office-BP measurements and 24-h ABPM. Hypertension thresholds for office and ambulatory BP were defined according to the 2017 ACC/AHA and 2021 KDIGO guidelines for KTRs.

RESULTS

Age, time from transplantation, eGFR and history of major comorbidities did not differ between groups. Office SBP/DBP levels were insignificantly higher in men than women (130.3 ± 16.3/77.3 ± 9.4 vs. 126.4 ± 17.8/74.9 ± 11.5 mmHg; P = 0.118/0.104) but daytime SBP/DBP was significantly higher in men (128.5 ± 12.1/83.0 ± 8.2 vs. 124.6 ± 11.9/80.3 ± 9.3 mmHg; P = 0.032/P = 0.044). No significant between-group differences were detected for night-time BP. The prevalence of hypertension was similar by office-BP criteria (93.4 vs. 91.3%; P = 0.589), but higher in men than women with ABPM (100 vs. 95.7%; P = 0.014). The use of ACEIs/ARBs and CCBs was more common in men. Office-BP control was similar (43.3 vs. 44.4%, P = 0.882), but 24-h control was significantly lower in men than women (16.9 vs. 30.3%; P = 0.029). White-coat hypertension was similar (5.1 vs. 7.6%; P = 0.493), whereas masked hypertension was insignificantly more prevalent in men than women (35.3 vs. 24.2%; P = 0.113).

CONCLUSION

BP levels, hypertension prevalence and control are similar by office criteria but significantly different by ABPM criteria between male and female KTRs. Worse ambulatory BP control in male compared with female KTRs may interfere with renal and cardiovascular outcomes.

Assessment of hypertension in kidney transplantation by ambulatory blood pressure monitoring: a systematic review and meta-analysis

Background

Hypertension (HTN) is common following renal transplantation and it is associated with adverse effects on cardiovascular (CV) and graft health. Ambulatory blood pressure monitoring (ABPM) is the preferred method to characterize blood pressure (BP) status, since HTN misclassification by office BP (OBP) is quite common in this population. We performed a systematic review and meta-analysis aimed at determining the clinical utility of 24-h ABPM and its potential implications for the management of HTN in this population.

Methods

Ovid-MEDLINE and PubMed databases were searched for interventional or observational studies enrolling adult kidney transplant recipients (KTRs) undergoing 24-h ABP readings compared with OBP or home BP. The main outcome was the proportion of KTRs diagnosed with HTN by ABPM, home or OBP recordings. Additionally, day-night BP variability and dipper/non-dipper status were assessed.

Results

Forty-two eligible studies (4115 participants) were reviewed. A cumulative analysis including 27 studies (3481 participants) revealed a prevalence of uncontrolled HTN detected by ABPM of 56% [95% confidence interval (CI) 46-65%]. The pooled prevalence of uncontrolled HTN according to OBP was 47% (95% CI 36-58%) in 25 studies (3261 participants). Very few studies reported on home BP recordings. The average concordance rate between OBP and ABPM measurements in classifying patients as controlled or uncontrolled hypertensive was 66% (95% CI 59-73%). ABPM revealed HTN phenotypes among KTRs. Two pooled analyses of 11 and 10 studies, respectively, revealed an average prevalence of 26% (95% CI 19-33%) for masked HTN (MHT) and 10% (95% CI 6-17%) for white-coat HTN (WCH). The proportion of non-dippers was variable across the 28 studies that analysed dipping status, with an average prevalence of 54% (95% CI 45-63%).

Conclusions

In our systematic review, comparison of OBP versus ABP measurements disclosed a high proportion of MHT, uncontrolled HTN and, to a lesser extent, WCH in KTRs. These results suggest that HTN is not adequately diagnosed and controlled by OBP recordings in this population. Furthermore, the high prevalence of non-dippers confirmed that circadian rhythm is commonly disturbed in KTRs.

Diagnostic Performance of Office versus Ambulatory Blood Pressure in Kidney Transplant Recipients

INTRODUCTION

Hypertension is the most prominent risk factor in kidney transplant recipients (KTRs). No study so far assessed in parallel the prevalence, control, and phenotypes of blood pressure (BP) or the accuracy of currently recommended office BP diagnostic thresholds in diagnosing elevated ambulatory BP in KTRs.

METHODS

205 stable KTRs underwent office BP measurements and 24-h ambulatory BP monitoring (ABPM). Hypertension was defined as follows: (1) office BP ≥140/90 mm Hg or use of antihypertensive agents following the current European Society of Cardiology/European Society of Hypertension (ESC/ESH) guidelines, (2) office BP ≥130/80 mm Hg or use of antihypertensive agents following the current American College of Cardiology/American Heart Association (ACC/AHA) guidelines, (3) ABPM ≥130/80 mm Hg or use of antihypertensive agents, and (4) ABPM ≥125/75 mm Hg or use of antihypertensive agents.

RESULTS

Hypertension prevalence by office BP was 88.3% with ESC/ESH and 92.7% with ACC/AHA definitions compared to 94.1 and 98.5% at relevant ABPM thresholds. Control rates among hypertensive patients were 69.6 and 43.7% with office BP compared to 38.3 and 21.3% with ABPM, respectively. Both for prevalence (κ-statistics = 0.52, p < 0.001 and 0.32, and p < 0.001) and control rates (κ-statistics = 0.21, p < 0.001 and 0.22, and p < 0.001, respectively), there was moderate or fair agreement of the 2 techniques. White-coat and masked hypertension were diagnosed in 6.7 and 39.5% of patients at the 140/90 threshold and 5.9 and 31.7% of patients at the 130/80 threshold. An office BP ≥140/90 mm Hg had 35.3% sensitivity and 84.9% specificity for the diagnosis of 24-h BP ≥130/80 mm Hg. An office BP ≥130/80 mm Hg had 59.7% sensitivity and 73.9% specificity for the diagnosis of 24-h BP ≥125/75 mm Hg. Receiver operating curve analyses confirmed this poor diagnostic performance.

CONCLUSIONS

At both corresponding thresholds studied, ABPM revealed particularly high hypertension prevalence and poor BP control in KTRs. Misclassification of KTRs by office BP is substantial, due to particularly high rates of masked hypertension. The diagnostic accuracy of office BP for identifying elevated ambulatory BP is poor. These findings call for a wider use of ABPM in KTRs.

Kidney transplantation and COVID-19 renal and patient prognosis

Coronavirus disease 2019 (COVD-19) emerged as a pandemic in December 2019. Infection has spread quickly and renal transplant recipients receiving chronic immunosuppression have been considered a population at high risk of infection, complications and infection-related death. During this year a large amount of information from nationwide registries, multicentre and single-centre studies have been reported. The number of renal transplant patients diagnosed with COVID-19 was higher than in the general population, but the lower threshold for testing may have contributed to its better identification. Major complications such as acute kidney injury and acute respiratory distress syndrome were very frequent in renal transplant patients, with a high comorbidity burden, but further studies are needed to support that organ transplant recipients receiving chronic immunosuppression are more prone to develop these complications than the general population. Kidney transplant recipients experience a high mortality rate compared with the general population, especially during the very early post-transplant period. Despite the fact that some studies report more favourable outcomes in patients with a kidney transplant than in patients on the kidney waiting list, the higher mortality described in the very early post-transplant period would advise against performing a kidney transplant in areas where the spread of infection is high, especially in recipients >60 years of age. Management of transplant recipients has been challenging for clinicians and strategies such as less use of lymphocyte-depleting agents for new transplants or anti-metabolite withdrawal and calcineurin inhibitor reduction for transplant patients with COVID-19 are not based on high-quality evidence.

Changes in Office Blood Pressure Control, Augmentation Index, and Liver Steatosis in Kidney Transplant Patients after Successful Hepatitis C Infection Treatment with Direct Antiviral Agents

Hepatitis C virus (HCV) infection in kidney transplant recipients (KTRs) can be successfully treated with direct antiviral agents (DAA). The aim of our study was to analyze different measures of vascular function during and after the DAA treatment. As we have observed the improvement of blood pressure (BP) control in some individuals, we have conducted an analysis of potential explanatory mechanisms behind this finding. Twenty-eight adult KTRs were prospectively evaluated before and 15 months after start of DAA therapy. Attended office BP (OBP), augmentation index (AIx), pulse wave velocity (PWV), flow-mediated dilation (FMD), liver stiffness measurement (LSM), and liver steatosis assessment (controlled attenuation parameter (CAP)) were measured. In half of the patients, improvement of OBP control (decline of systolic BP by at least 20 mmHg or reduction of the number of antihypertensive drugs used) and parallel central aortic pressure parameters, including AIx, was observed. There was a significant decrease in CAP mean values (241 ± 54 vs. 209 ± 30 dB/m, p < 0.05) only in patients with OBP control improvement. Half of our KTRs cohort after successful HCV eradication noted clinically important improvement of both OBP control and central aortic pressure parameters, including AIx. The concomitant decrease of liver steatosis was observed only in the subgroup of patients with improvement of blood pressure control.

Arterial stiffness but not endothelial dysfunction is associated with multidrug antihypertensive therapy and nondipper blood pressure pattern in kidney transplant recipients

Vascular injury related to chronic kidney disease results in increased arterial stiffness and endothelial dysfunction which may affect arterial blood pressure (BP) and influence patient and graft survival in kidney transplant recipients (KTRs).This cross-sectional study aims to elucidate the relationship between the above-mentioned measures of vascular damage and effectiveness of antihypertensive treatment in KTR.One hundred forty-five KTRs 7.6 ± 2.7 years after transplantation were enrolled in our study. Pulse wave velocity (PWV), flow-mediated dilation (FMD), and nitroglycerin-mediated dilation (NMD) were measured, and 24-hour ambulatory BP monitoring was performed.Overall, there were 62 patients with well-controlled or borderline BP and 83 subjects who did not achieve target BP despite antihypertensive treatment. Patients with suboptimal BP control were characterized by greater PWV (median 9.6/interquartile range: 3.9 vs 8.0/3.3 m/s, P = .002), but borderline lower FMD (8.4% ± 5.0% vs 9.9% ± 5.7%; P = .09) as compared with the group with better BP control. When patients were allocated to subgroups based on the number of current antihypertensive medications, no differences in FMD and NMD were found. However, a significant trend was observed for higher PWV values and decreased proportion of dippers along with the increasing number of drugs. PWV, diabetes, and total cholesterol level, but not FMD or NMD, were explanatory variables for systolic BP in multivariate analysis.Arterial stiffness but not endothelial dysfunction is associated with suboptimal BP control in stable KTRs. Less efficient antihypertensive treatment appears to be caused by inadequate control of nocturnal BP.

Diurnal blood pressure changes

The definition of diurnal blood pressure changes varies widely, which can be confusing. Short-term blood pressure variability during a 24-h period and the dipping status of diurnal blood pressure can be captured by ambulatory blood pressure monitoring, and these metrics are reported to have prognostic significance for cardiovascular complications. Morning blood pressure surge also indicates this risk, but its effect may be limited to populations with specific conditions. Meanwhile, the combined use of conventional office blood pressure and out-of-office blood pressure allows us to identify people with white-coat and masked hypertension. Current home devices can measure nocturnal blood pressure during sleep more conveniently than ambulatory monitoring; however, we should pay attention to blood pressure measurement conditions regardless of whether they are in a home, ambulatory, or office setting. The relatively poor reproducibility of diurnal blood pressure changes, including the nocturnal fall of blood pressure, is another underestimated issue to be addressed. Although information on diurnal blood pressure changes is expected to be used more effectively in the future, we should also keep in mind that blood pressure levels have remained central to the primary and secondary prevention of blood pressure-related cardiovascular diseases in clinical practice.

Association of white blood cell counts with left ventricular mass index in hypertensive patients undergoing anti-hypertensive drug therapy

Although studies using animal models have demonstrated that nonhemodynamic factors, including inflammatory cells and cytokines, contribute to left ventricular hypertrophy (LVH), there is little clinical data to confirm this association. Therefore in the present study, levels of circulating specific types of leukocyte were measured to determine the association between white blood cells and left ventricular mass index (LVMI) in hypertensive patients undergoing anti-hypertensive drug therapy. A total of 144 consecutive hypertensive patients taking anti-hypertensive drug therapy were enrolled in the current study. Subjects were divided into two groups: Those with normal geometry and those with left LVH. Total white blood cells and differentiated subtypes (neutrophils, lymphocytes, monocytes) were counted, and left ventricular end-diastolic diameter, left ventricular posterior wall thickness in diastole and inter-ventricular septal wall thickness in diastole were all measured. Analysis revealed a significant correlation between LVMI and total white blood cell levels (P=0.013). The percentage of LVH in the highest tertile of WBC was increased compared with the middle tertile (P=0.008). Furthermore, a significant correlation between the highest tertile of neutrophil counts and LVH was observed (P=0.039). However, no significant associations between LVMI and monocyte or lymphocyte counts were detected. Therefore, the current study determined that increased total white blood cell and neutrophil subtype counts were associated with LVMI in hypertensive patients undergoing anti-hypertensive drug therapy. They may provide convenient and useful markers for further risk appraisal of LVH caused by nonhemodynamic factors of hypertension.

Inflammation and Atherosclerosis Are Associated With Hypertension in Kidney Transplant Recipients

The aim of the current study was to evaluate risk factors associated with hypertension in kidney transplant recipients. The authors recruited 92 consecutive kidney transplant recipients and 30 age-matched patients with chronic kidney disease without history of cardiovascular events. Twenty-four-hour ambulatory blood pressure monitoring, pulse wave velocity, and carotid ultrasound were performed. Serum levels of log-transformed interleukin 6 (Log IL-6), soluble tumor necrosis factor receptor 2, and intercellular adhesion molecule 1 were determined. Twenty-four-hour systolic blood pressure (SBP) (P=.0001), Log IL-6 (P=.011), and total number of carotid plaques (P=.013) were higher, while the percentage decline of SBP from day to night was lower in kidney transplant recipients (P=.003). Independent predictors of 24-hour SBP were urinary protein/creatinine ratio and circulating monocytes (P=.001), while Log IL-6, serum creatinine, and total number of carotid plaques (P=.0001) were independent predictors of percentage decline of SBP from day to night. These results suggest that subclinical atherosclerosis and systemic inflammation are associated with hypertension after transplantation.

Hypertension, living kidney donors, and transplantation: where are we today?

Hypertension is a prevalent problem in kidney transplant recipients that is known to be a "traditional" risk factor for atherosclerotic cardiovascular disease leading to premature allograft failure and death. Donor, peritransplant, and recipient factors affect hypertension risk. Blood pressure control after transplantation is inversely associated with glomerular filtration rate (GFR). Calcineurin inhibitors, the most commonly used class of immunosuppressives, cause endothelial dysfunction, increase vascular tone, and sodium retention via the renin-angiotensin-aldosterone system resulting in systemic hypertension. Steroid withdrawal seems to have little impact on blood pressure control. Newer agents like belatacept appear to be associated with less hypertension. Transplant renal artery stenosis is an important, potentially treatable cause of hypertension. Dihydropyridine calcium channel blockers mitigate calcineurin inhibitor nephrotoxicity and may be associated with improved estimated GFR. Angiotensin-converting enzyme inhibitors and angiotensin receptor blockers are not recommended in the first 3 to 6 months given their effects on reduced estimated GFR, anemia, and hyperkalemia. The use of ß-blockers may be associated with improved patient survival, even for patients without cardiovascular disease. Living donation may increase blood pressure by 5 mm Hg or more. Some transplant centers accept Caucasian living donors with well-controlled hypertension on a single agent if they agree to close follow-up.