Hypertension in renal parenchymal disease: why is it so resistant to treatment?

Mechanisms of Antihypertensive Effect of Chlorthalidone in Advanced Chronic Kidney Disease: A Causal Mediation Analysis

Key Points

Chlorthalidone reduces the amount of fluid and the BP, but fluid volume reduction is not the cause of lowering of BP. It is not volume loss but the response to volume loss such as the synthesis of substances that lower BP is important.

Background

Chlorthalidone (CTD) in a chronic kidney disease randomized trial demonstrated a robust reduction in systolic BP in stage 4 CKD. In this study, we explore the mechanisms underlying the antihypertensive effect of CTD.

Methods

In this prespecified analysis, we analyzed the contributions of baseline levels of 24-hour urinary sodium and aldosterone and the changes from baseline to 4 weeks in the multiple mediators reflecting volume status in a causal mediation analysis framework. Baseline levels of these mediators served as covariates. No power calculation for this analysis was performed.

Results

Of the 160 patients randomized, 140 (87.5%) were included in this analysis. Compared with placebo, CTD within 4 weeks reduced weight −1.5% (95% confidence interval [CI], −2.2 to −0.7) and volume −1.4% (95% CI, −2.2 to −0.6), stimulated plasma renin 40.5% (95% CI, 25.4% to 57.4%) and serum aldosterone 40.2% (95% CI, 11.7% to 76%), and reduced plasma N -terminal pro-B-type natriuretic peptide levels −19.4% (95% CI, −33.8% to −1.9%). Mediation analysis revealed the following results: for weight change, the total effect on systolic BP was −10.8 mm Hg (95% CI, −16 to −5.7), of which weight change (indirect effect) accounted for −0.9 mm Hg (95% CI, −4.2 to 2.5) and BP change independent of weight (direct effect) accounted for −10 mm Hg (−15.7 to −4.2). Thus, the percent mediation was 8.1% (95% CI, −22.4 to 38.5). Baseline excretion of 24-hour sodium or aldosterone or any of the changes in the above mediators examined accounted for <2 mm Hg BP drop and were not significant for any of the mediators.

Conclusions

CTD improved BP control among patients with advanced CKD independent of baseline urinary sodium, aldosterone, weight loss, or changes in the renin-angiotensin system or N -terminal pro-B-type natriuretic peptide.

Clinical Trial registry name and registration number:

CTD in chronic kidney disease ClinicalTrials.gov number: NCT02841280 .

Mechanisms of inflammation modulation by different immune cells in hypertensive nephropathy

Hypertensive nephropathy (HTN) is the second leading cause of end-stage renal disease (ESRD) and a chronic inflammatory disease. Persistent hypertension leads to lesions of intrarenal arterioles and arterioles, luminal stenosis, secondary ischemic renal parenchymal damage, and glomerulosclerosis, tubular atrophy, and interstitial fibrosis. Studying the pathogenesis of hypertensive nephropathy is a prerequisite for diagnosis and treatment. The main cause of HTN is poor long-term blood pressure control, but kidney damage is often accompanied by the occurrence of immune inflammation. Some studies have found that the activation of innate immunity, inflammation and acquired immunity is closely related to the pathogenesis of HTN, which can cause damage and dysfunction of target organs. There are more articles on the mechanism of diabetic nephropathy, while there are fewer studies related to immunity in hypertensive nephropathy. This article reviews the mechanisms by which several different immune cells and inflammatory cytokines regulate blood pressure and renal damage in HTN. It mainly focuses on immune cells, cytokines, and chemokines and inhibitors. However, further comprehensive and large-scale studies are needed to determine the role of these markers and provide effective protocols for clinical intervention and treatment.

Prevalence, Predictors, and Outcomes of Resistant Hypertension in Egyptian Population

Background

Hypertension is a leading problem; it affects around thirty million adult Egyptians, according to the last national registry. The exact prevalence of resistant hypertension (RH) in Egypt wasn't spotted before. The purpose of this study was to determine the prevalence, predictors, and impact on adverse cardiovascular outcomes among adult Egyptians with RH.

Methods

The present study examined a cohort of 990 hypertensive patients who were divided into two groups based on their blood pressure control; group I (n = 842) patients who achieved blood pressure control and group II (n = 148) patients who met the RH definition criteria. All patients underwent a close follow-up for one year to evaluate the major cardiovascular events.

Results

The prevalence of RH was 14.9%. The main predictors impacting the cardiovascular outcomes of RH were advanced age (≥65 years), the presence of chronic kidney diseases, a BMI ≥ 30 kg/m², and NSAID use. After one year of follow-up, the RH group displayed noticeably higher rates of major cardiovascular events, including new-onset atrial fibrillation (6.8% vs. 2.5%, P = 0.006), cerebral stroke (4.1% vs. 1.2%, P = 0.011), myocardial infarction (4.7% vs. 1.3%, P = 0.004), and acute heart failure (4.7% vs. 1.8%, P = 0.025).

Conclusion

The prevalence of RH in Egypt is moderately high. Patients with RH have a far higher risk of cardiovascular events than those whose blood pressure is within control.

The link between immunity and hypertension in the kidney and heart

Hypertension is the primary cause of cardiovascular disease, which is a leading killer worldwide. Despite the prevalence of this non-communicable disease, still between 90% and 95% of cases are of unknown or multivariate cause ("essential hypertension"). Current therapeutic options focus primarily on lowering blood pressure through decreasing peripheral resistance or reducing fluid volume, but fewer than half of hypertensive patients can reach blood pressure control. Hence, identifying unknown mechanisms causing essential hypertension and designing new treatment accordingly are critically needed for improving public health. In recent years, the immune system has been increasingly implicated in contributing to a plethora of cardiovascular diseases. Many studies have demonstrated the critical role of the immune system in the pathogenesis of hypertension, particularly through pro-inflammatory mechanisms within the kidney and heart, which, eventually, drive a myriad of renal and cardiovascular diseases. However, the precise mechanisms and potential therapeutic targets remain largely unknown. Therefore, identifying which immune players are contributing to local inflammation and characterizing pro-inflammatory molecules and mechanisms involved will provide promising new therapeutic targets that could lower blood pressure and prevent progression from hypertension into renal or cardiac dysfunction.

Hypertension in chronic kidney disease: What lies behind the scene

Hypertension is a frequent condition encountered during kidney disease development and a leading cause in its progression. Hallmark factors contributing to hypertension constitute a complexity of events that progress chronic kidney disease (CKD) into end-stage renal disease (ESRD). Multiple crosstalk mechanisms are involved in sustaining the inevitable high blood pressure (BP) state in CKD, and these play an important role in the pathogenesis of increased cardiovascular (CV) events associated with CKD. The present review discusses relevant contributory mechanisms underpinning the promotion of hypertension and their consequent eventuation to renal damage and CV disease. In particular, salt and volume expansion, sympathetic nervous system (SNS) hyperactivity, upregulated renin–angiotensin–aldosterone system (RAAS), oxidative stress, vascular remodeling, endothelial dysfunction, and a range of mediators and signaling molecules which are thought to play a role in this concert of events are emphasized. As the control of high BP via therapeutic interventions can represent the key strategy to not only reduce BP but also the CV burden in kidney disease, evidence for major strategic pathways that can alleviate the progression of hypertensive kidney disease are highlighted. This review provides a particular focus on the impact of RAAS antagonists, renal nerve denervation, baroreflex stimulation, and other modalities affecting BP in the context of CKD, to provide interesting perspectives on the management of hypertensive nephropathy and associated CV comorbidities.

Thromboxane A2 is involved in the development of hypertension in chronic kidney disease rats

Hypertension is one of the most common complications of chronic kidney disease (CKD). Some research has indicated that changes in large artery function especially caused by thromboxane A2 (TXA2) may be a novel factor acting to induce hypertension in CKD. We studied the 5/6 nephrectomy rat model and measured serum levels of creatinine (Cr), calcium (Ca), phosphorus (P), TXA2-stable metabolites (thromboxane B2, TXB2), and caudal artery pressure after nephrectomy. The tension variations in thoracic aortas were measured after stimulating by vasoconstrictor/vasodilator using the cumulative concentration administration method and then tested the expression of TXA2 receptors in the thoracic aortas through western blots. The CKD rats developed uremia, electrolyte imbalances，and hypertension. They also exhibited a significant increase in TXB2 concentration. The aortic rings of CKD rats showed an increased contraction response to U46619 (a TXA2 analogue) and the expression of TXA2 receptors also enhanced. In the meanwhile, the diastolic function decreased in the CKD group. Our results demonstrate that the impairment of artery contractile function caused by the increase of TXA2 receptors on the wall of aortic rings may be involved in hypertension in CKD rats.

Predictive Factors Affecting the Success of Nephrectomy for the Treatment of Nephrogenic Hypertension: Multicenter Study

INTRODUCTION

The aim of our study is to evaluate the predictive factors affecting the success of treatment with nephrectomy in patients with poorly functioning kidney and nephrogenic hypertension.

METHODS

Data for patients who underwent nephrectomy with a diagnosis of nephrogenic hypertension in 3 centers between May 2010 and January 2020 were analyzed. In the postoperative period, if the blood pressure (BP) was below 140/90 mm Hg without medical treatment, it was accepted as complete response; if the arterial BP was below 140/90 mm Hg with medical treatment or less medication, it was accepted as partial response; and if BP did not decrease to normal values, it was accepted as unresponsive. Demographic characteristics, duration of hypertension, preoperative and postoperative BP values, and presence of metabolic syndrome were statistically evaluated.

RESULTS

Our study consisted of 91 patients with a mean preoperative hypertension duration of 23.3 ± 12.1 months. Among patients, 42 (46.2%) had complete response, 18 (19.8%) had partial response, and 31 (34.0%) had no response. Preoperative systolic and diastolic BP values were not effective on treatment success (p = 0.071, p = 0.973, respectively), but the increase in age and hypertension duration (p = 0.030 and p < 0.001, respectively) and the presence of metabolic syndrome (p = 0.002) significantly decreased the complete response rates.

CONCLUSIONS

Preoperative hypertension duration, advanced age, and presence of metabolic syndrome are predictive factors affecting the response to treatment in patients who undergo nephrectomy due to nephrogenic hypertension.

Lifetime risk of stroke stratified by chronic kidney disease and hypertension in the general Asian population: the Ohasama study

Lifetime risk (LTR) evaluates the absolute risk of developing a disease during the remainder of one's life. It can be a useful tool, enabling the general public to easily understand their risk of stroke. No study has been performed to determine the LTR of cardiovascular disease in patients with chronic kidney disease (CKD) with or without hypertension; therefore, we performed this study in an Asian population. We followed 1525 participants (66.0% women; age 63.1 years) in the general population of Ohasama, Japan. We defined CKD as an estimated glomerular filtration rate (eGFR) <60 mL/min/1.73 m² and/or proteinuria. Hypertension was defined as a systolic/diastolic blood pressure ≥140/≥90 mmHg and/or the use of antihypertensive medication. We calculated the sex-specific LTR of stroke adjusted for the competing risk of death. During the mean follow-up period of 16.5 years, a first stroke occurred in 238 participants. The 10-year risk of stroke at the age of 45 years was 0.0% for men and women. The LTRs of stroke at the index age of 45 years (men/women) were 20.9%/14.5% for participants without CKD and hypertension, 34.1%/29.8% for those with CKD but not hypertension, 37.9%/27.3% for those with hypertension but not CKD, and 38.4%/36.4% for those with CKD and hypertension. The LTRs of stroke tended to be higher in younger participants than in older participants with CKD and/or hypertension. CKD contributed to the LTR of stroke, as did hypertension. The prevention of CKD and hypertension can reduce the LTR of stroke, especially in young populations.

Mechanism of herbal medicine on hypertensive nephropathy (Review)

Hypertensive nephropathy is the most common complication of hypertension, and is one of the main causes of end-stage renal disease (ESRD) in numerous countries. The basic pathological feature of hypertensive nephropathy is arteriolosclerosis followed by renal parenchymal damage. The etiology of this disease is complex, and its pathogenesis is mainly associated with renal hemodynamic changes and vascular remodeling. Despite the increased knowledge on the pathogenesis of hypertensive nephropathy, the current clinical treatment methods are still not effective in preventing the development of the disease to ESRD. Herbal medicine, which is used to relieve symptoms, can improve hypertensive nephropathy through multiple targets. Since there are few clinical studies on the treatment of hypertensive nephropathy with herbal medicine, this article aims to review the progress on the basic research on the treatment of hypertensive nephropathy with herbal medicine, including regulation of the renin angiotensin system, inhibition of sympathetic excitation, antioxidant stress and anti-inflammatory protection of endothelial cells, and improvement of obesity-associated factors. Herbal medicine with different components plays a synergistic and multi-target role in the treatment of hypertensive nephropathy. The description of the mechanism of herbal medicine in the treatment of hypertensive nephropathy will contribute towards the progress of modern medicine.

Sympathetic Hyperactivity—A Hidden Enemy in Chronic Kidney Disease Patients

Chronic kidney disease is often characterized by the presence of sympathetic hyperactivity. The aim of this brief review is to summarize available knowledge on the pathogenesis of sympathetic hyperactivity and to discuss its clinical relevance, the consequences of this knowledge for the choice of treatment, and the yet unresolved issues.

Hypertension, retinopathy, and acute kidney injury in dogs: A prospective study

BACKGROUND

Systemic hypertension (SH) is a potential complication of acute kidney injury (AKI) in dogs.

OBJECTIVE

To describe the prevalence of SH and hypertensive retinopathy in dogs with AKI, to investigate the relationship between SH and severity of AKI and to assess possible factors associated with SH.

ANIMALS

Fifty-two dogs with AKI.

METHODS

Prospective observational study of dogs presenting to a tertiary referral center that fulfilled the International Renal Interest Society (IRIS) guidelines for the diagnosis of AKI. Systolic blood pressure measurement, urine protein/creatinine ratio (UPCR), urine output, presence of hypertensive retinopathy and fluid overload (FO), survival to discharge and duration of hospitalization were subsequently assessed. The prevalence of SH was calculated and the relationship between SH and recorded factors was examined by nonparametric statistics.

RESULTS

The prevalence of SH (≥160 mm Hg) on admission or during hospitalization was 75% (39/52) and in 56% (22/39) of cases this was severe (≥180 mm Hg). Sixteen percent (7/43) of dogs had evidence of hypertensive retinopathy and 77% (24/31) dogs had UPCR >0.5. Forty-two percent (22/52) dogs had FO on admission or during hospitalization. There was no association between SH and IRIS AKI grade, oligo/anuria, survival to discharge, duration of hospitalization or proteinuria. Dogs with FO on presentation were more likely to be hypertensive at admission compared to dogs without FO (P = .02). Dogs that did not survive to discharge were more likely to have FO (P = .007).

CONCLUSIONS AND CLINICAL IMPORTANCE

Systemic hypertension is common in dogs with AKI. Systemic hypertension might be associated with FO, which itself is associated with nonsurvival. Monitoring for SH and FO is therefore warranted in dogs with AKI.

Comparison of high-fat style diet-induced dysregulation of baroreflex control of renal sympathetic nerve activity in intact and ovariectomized female rats: Renal sympathetic nerve activity in high-fat style diet fed intact and ovariectomized female rats

IMPACT STATEMENT

Over activation of renal sensory nerve in obesity blunts the normal regulation of renal sympathetic nerve activity. To date, there is no investigation that has been carried out on baroreflex regulation of renal sympathetic nerve activity in obese ovarian hormones deprived rat model, and the effect of renal denervation on the baroreflex regulation of renal sympathetic nerve activity. Thus, we investigated the role of renal innervation on baroreflex regulation of renal sympathetic nerve activity in obese intact and ovariectomized female rats. Our data demonstrated that in obese states, the impaired baroreflex control is indistinguishable between ovarian hormones deprived and non-deprived states. This study will be of substantial interest to researchers working on the impact of diet-induced hypertension in pre- and postmenopausal women. This study provides insight into health risks amongst obese women regardless of their ovarian hormonal status and may be integrated in preventive health strategies.

Association of a Disrupted Dipping Pattern of Blood Pressure with Progression of Renal Injury during the Development of Salt-Dependent Hypertension in Rats

The aim of the present study is to investigate whether a disruption of the dipping pattern of blood pressure (BP) is associated with the progression of renal injury in Dahl salt-sensitive (DSS) hypertensive rats. Seven-week-old DSS rats were fed a high salt diet (HSD; 8% NaCl) for 10 weeks, followed by a transition to a normal salt diet (NSD; 0.3% NaCl) for 4 weeks. At baseline, NSD-fed DSS rats showed a dipper-type circadian rhythm of BP. By contrast, HSD for 5 days caused a significant increase in the difference between the active and inactive periods of BP with an extreme dipper type of BP, while proteinuria and renal tissue injury were not observed. Interestingly, HSD feeding for 10 weeks developed hypertension with a non-dipper pattern of BP, which was associated with obvious proteinuria and renal tissue injury. Four weeks after switching to an NSD, BP and proteinuria were significantly decreased, and the BP circadian rhythm returned to the normal dipper pattern. These data suggest that the non-dipper pattern of BP is associated with the progression of renal injury during the development of salt-dependent hypertension.

Renal Sympathetic Nerve-Derived Signaling in Acute and Chronic kidney Diseases

The kidney is innervated by afferent sensory and efferent sympathetic nerve fibers. Norepinephrine (NE) is the primary neurotransmitter for post-ganglionic sympathetic adrenergic nerves, and its signaling, regulated through adrenergic receptors (AR), modulates renal function and pathophysiology under disease conditions. Renal sympathetic overactivity and increased NE level are commonly seen in chronic kidney disease (CKD) and are critical factors in the progression of renal disease. Blockade of sympathetic nerve-derived signaling by renal denervation or AR blockade in clinical and experimental studies demonstrates that renal nerves and its downstream signaling contribute to progression of acute kidney injury (AKI) to CKD and fibrogenesis. This review summarizes our current knowledge of the role of renal sympathetic nerve and adrenergic receptors in AKI, AKI to CKD transition and CKDand provides new insights into the therapeutic potential of intervening in its signaling pathways.

Sympathetic Activation in Hypertensive Chronic Kidney Disease - A Stimulus for Cardiac Arrhythmias and Sudden Cardiac Death?

Studies have revealed a robust and independent correlation between chronic kidney disease (CKD) and cardiovascular (CV) events, including death, heart failure, and myocardial infarction. Recent clinical trials extend this range of adverse CV events, including malignant ventricular arrhythmias and sudden cardiac death (SCD). Moreover, other studies point out that cardiac structural and electrophysiological changes are a common occurrence in this population. These processes are likely contributors to the heightened hazard of arrhythmias in CKD population and may be useful indicators to detect patients who are at a higher SCD risk. Sympathetic overactivity is associated with increased CV risk, specifically in the population with CKD, and it is a central feature of the hypertensive state, occurring early in its clinical course. Sympathetic hyperactivity is already evident at the earliest clinical stage of CKD and is directly related to the progression of renal failure, being most pronounced in those with end-stage renal disease. Sympathetic efferent and afferent neural activity in kidney failure is a crucial facilitator for the perpetuation and evolvement of the disease. Here, we will revisit the role of the feedback loop of the sympathetic neural cycle in the context of CKD and how it may aggravate several of the risk factors responsible for causing SCD. Targeting the overactive sympathetic nervous system therapeutically, either pharmacologically or with newly available device-based approaches, may prove to be a pivotal intervention to curb the substantial burden of cardiac arrhythmias and SCD in the high-risk population of patients with CKD.

AORTIC ANEURYSM, DISSECTION, AND RUPTURE IN SIX BILE-FARMED BEARS

Across China and Southeast Asia, over 17,000 bears are currently farmed for bile, predominantly for traditional Chinese medicines. Bears on farms in China are cage confined and undergo repeated daily bile extraction facilitated by surgically implanted catheters or gallbladder fistulas. Numerous health problems have been reported in bile-farmed bears including peritonitis, abdominal hernias, and extraction site abscessation. Between 2009 and 2014, five Asiatic black bears ( Ursus thibetanus) and one Asiatic black/Eurasian brown bear ( Ursus arctos arctos) hybrid, rescued from the bear bile industry in China, died from ruptured and/or dissecting aortic aneurysm. Medical records were reviewed and two bears exhibited no clinical signs prior to death. In four bears, clinical findings varied and included increased stereotypic behavior prior to death, epistaxis, retinal lesions, dysphagia, weight loss, and acute onset of hyporexia. On postmortem examination, hemopericardium with dissection and/or rupture of the ascending aorta and left ventricular wall hypertrophy were present in all cases. No evidence of infectious disease, connective tissue disorders, or congenital cardiac disease was identified. Based on these observations screening thoracic radiography was performed on all bears at the rescue center and aortic dilation was identified in 73 of 134 (54.5%) bile-extracted bears. To the authors' knowledge, aortic aneurysm, rupture, and/or dissection have not been previously reported in any bear species and the high prevalence in this population of bears suggests an association with bile-farming practices. Future studies are needed to investigate the etiopathogenesis of this condition to aid in early diagnosis and improved management of bears being rescued from bile farms across Asia.

Chronic intermittent hypoxia-mediated renal sympathetic nerve activation in hypertension and cardiovascular disease

In sleep apnea syndrome (SAS), chronic intermittent hypoxia (CIH) is believed to activate the sympathetic nerve system, and is thus involved in cardiovascular diseases (CVD). However, since patients with SAS are often already obese, and have diabetes and/or hypertension (HT), the effects of CIH alone on sympathetic nerve activation and its impacts on CVD are largely unknown. We, therefore, examined the effects of CIH on sympathetic nerve activation in non-obese mice to determine whether renal sympathetic nerve denervation (RD) could ameliorate CIH-mediated cardiovascular effects. Male C57BL/6 (WT) mice were exposed to normal (FiO₂ 21%) or CIH (10% O₂, 12 times/h, 8 h/day) conditions for 4 weeks with or without RD treatment. Increased urinary norepinephrine (NE), 8-OHdG, and angiotensinogen levels and elevated serum asymmetric dimethyl arginine levels were observed in the CIH model. Concomitant with these changes, blood pressure levels were significantly elevated by CIH treatment. However, these deleterious effects by CIH were completely blocked by RD treatment. The present study demonstrated that CIH-mediated renal sympathetic nerve activation is involved in increased systemic oxidative stress, endothelial dysfunction, and renin-angiotensin system activation, thereby contributing to the development of HT and CVD, thus could be an important therapeutic target in patients with SAS.

Role of the Sympathetic Nervous System and Its Modulation in Renal Hypertension

The kidneys are densely innervated with renal efferent and afferent nerves to communicate with the central nervous system. Innervation of major structural components of the kidneys, such as blood vessels, tubules, the pelvis, and glomeruli, forms a bidirectional neural network to relay sensory and sympathetic signals to and from the brain. Renal efferent nerves regulate renal blood flow, glomerular filtration rate, tubular reabsorption of sodium and water, as well as release of renin and prostaglandins, all of which contribute to cardiovascular and renal regulation. Renal afferent nerves complete the feedback loop via central autonomic nuclei where the signals are integrated and modulate central sympathetic outflow; thus both types of nerves form integral parts of the self-regulated renorenal reflex loop. Renal sympathetic nerve activity (RSNA) is commonly increased in pathophysiological conditions such as hypertension and chronic- and end-stage renal disease. Increased RSNA raises blood pressure and can contribute to the deterioration of renal function. Attempts have been made to eliminate or interfere with this important link between the brain and the kidneys as a neuromodulatory treatment for these conditions. Catheter-based renal sympathetic denervation has been successfully applied in patients with resistant hypertension and was associated with significant falls in blood pressure and renal protection in most studies performed. The focus of this review is the neural contribution to the control of renal and cardiovascular hemodynamics and renal function in the setting of hypertension and chronic kidney disease, as well as the specific roles of renal efferent and afferent nerves in this scenario and their utility as a therapeutic target.

Left ventricular hypertrophy among chronic kidney disease patients in Ghana

Introduction

The presence of left ventricular hypertrophy (LVH) in patients with Chronic Kidney Disease (CKD) is associated with worsening cardiovascular outcomes. There is a dearth of data on LVH in Ghanaian CKD patients.

Methods

This was a cross sectional study carried out at the Komfo Anokye Teaching Hospital (KATH) in Kumasi, Ghana. A questionnaire was used to obtain information on clinical features of CKD. The MDRD-4 equation was used to calculate eGFR. Information on the prevalence and factors associated with electrocardiographic left ventricular hypertrophy were obtained during the initial assessment.

Results

About 64.5% of the 203 participants were male and the mean age was 43.9 ± 17.8 years. Most subjects (79.8%) had stage 5 disease. The mean systolic and diastolic blood pressures were 167.86 ± 39.87 and 101.8 ± 24.4 respectively. Approximately 43% of respondents had LVH. eGFR correlated negatively with LVH. High systolic pressure (OR 4.9, CI 2.4 – 10.4; p < 0.05), high diastolic pressure (OR 8.1, CI 4.0 – 16.1; p < 0.05) increased pulse pressure (OR 3.4 CI 2.6-9.3, p < 0.05), increased body mass index (OR 3.6 CI 1.7-11.2, p < 0.001) as well as male gender (OR 4.7, 95% CI 2.4 – 9.1; p <0.05) were associated with the presence of LVH.

Conclusion

LVH is common in our cohort. High pulse pressure, high DBP, increased BMI and male gender are significant associated factors. Adequate treatment of high blood pressure as well as early detection of LVH and interventions aimed at prevention and/or regression of LVH are to be encouraged.

Cooperative Oxygen Sensing by the Kidney and Carotid Body in Blood Pressure Control

Oxygen sensing mechanisms are vital for homeostasis and survival. When oxygen levels are too low (hypoxia), blood flow has to be increased, metabolism reduced, or a combination of both, to counteract tissue damage. These adjustments are regulated by local, humoral, or neural reflex mechanisms. The kidney and the carotid body are both directly sensitive to falls in the partial pressure of oxygen and trigger reflex adjustments and thus act as oxygen sensors. We hypothesize a cooperative oxygen sensing function by both the kidney and carotid body to ensure maintenance of whole body blood flow and tissue oxygen homeostasis. Under pathological conditions of severe or prolonged tissue hypoxia, these sensors may become continuously excessively activated and increase perfusion pressure chronically. Consequently, persistence of their activity could become a driver for the development of hypertension and cardiovascular disease. Hypoxia-mediated renal and carotid body afferent signaling triggers unrestrained activation of the renin angiotensin-aldosterone system (RAAS). Renal and carotid body mediated responses in arterial pressure appear to be synergistic as interruption of either afferent source has a summative effect of reducing blood pressure in renovascular hypertension. We discuss that this cooperative oxygen sensing system can activate/sensitize their own afferent transduction mechanisms via interactions between the RAAS, hypoxia inducible factor and erythropoiesis pathways. This joint mechanism supports our view point that the development of cardiovascular disease involves afferent nerve activation.

Chronic kidney disease and incident apparent treatment-resistant hypertension among blacks: Data from the Jackson Heart Study

It is unclear whether black patients with chronic kidney disease (CKD) vs those without CKD who take antihypertensive medication have an increased risk for apparent treatment-resistant hypertension (aTRH). The authors analyzed 1741 Jackson Heart Study participants without aTRH taking antihypertensive medication at baseline. aTRH was defined as uncontrolled blood pressure while taking three antihypertensive medication classes or taking four or more antihypertensive medication classes, regardless of blood pressure level. CKD was defined as an albumin to creatinine ratio ≥30 mg/g or estimated glomerular filtration rate <60 mL/min/1.73 m² . Over 8 years, 20.1% of participants without CKD and 30.5% with CKD developed aTRH. The multivariable-adjusted hazard ratio for aTRH comparing participants with CKD vs those without CKD was 1.45 (95% CI, 1.12-1.86). Participants with an albumin to creatinine ratio ≥30 vs <30 mg/g (hazard ratio, 1.44; 95% CI, 1.04-2.00) and estimated glomerular filtration rate of 45 to 59 mL/min/1.73 m² and <45 vs ≥60mL/min/1.73 m² (hazard ratio, 1.60 [95% CI, 1.16-2.20] and 2.05 [95% CI, 1.28-3.26], respectively) were more likely to develop aTRH.

The innervation of the kidney in renal injury and inflammation: a cause and consequence of deranged cardiovascular control

Extensive investigations have revealed that renal sympathetic nerves regulate renin secretion, tubular fluid reabsorption and renal haemodynamics which can impact on cardiovascular homoeostasis normally and in pathophysiological states. The significance of the renal afferent innervation and its role in determining the autonomic control of the cardiovascular system is uncertain. The transduction pathways at the renal afferent nerves have been shown to require pro-inflammatory mediators and TRPV1 channels. Reno-renal reflexes have been described, both inhibitory and excitatory, demonstrating that a neural link exists between kidneys and may determine the distribution of excretory and haemodynamic function between the two kidneys. The impact of renal afferent nerve activity on basal and reflex regulation of global sympathetic drive remains opaque. There is clinical and experimental evidence that in states of chronic kidney disease and renal injury, there is infiltration of T-helper cells with a sympatho-excitation and blunting of the high- and low-pressure baroreceptor reflexes regulating renal sympathetic nerve activity. The baroreceptor deficits are renal nerve-dependent as the dysregulation can be relieved by renal denervation. There is also experimental evidence that in obese states, there is a sympatho-excitation and disrupted baroreflex regulation of renal sympathetic nerve activity which is mediated by the renal innervation. This body of information provides an important basis for directing greater attention to the role of renal injury/inflammation causing an inappropriate activation of the renal afferent nerves as an important initiator of aberrant autonomic cardiovascular control.

Recognition and Management of Resistant Hypertension

Despite improvements in hypertension awareness and treatment, 30%-60% of hypertensive patients do not achieve BP targets and subsequently remain at risk for target organ damage. This therapeutic gap is particularly important to nephrologists, who frequently encounter treatment-resistant hypertension in patients with CKD. Data are limited on how best to treat patients with CKD and resistant hypertension, because patients with CKD have historically been excluded from hypertension treatment trials. First, we propose a consistent definition of resistant hypertension as BP levels confirmed by both in-office and out-of-office measurements that exceed appropriate targets while the patient is receiving treatment with at least three antihypertensive medications, including a diuretic, at dosages optimized to provide maximum benefit in the absence of intolerable side effects. Second, we recommend that each patient undergo a standardized, stepwise evaluation to assess adherence to dietary and lifestyle modifications and antihypertensive medications to identify and reduce barriers and discontinue use of substances that may exacerbate hypertension. Patients in whom there is high clinical suspicion should be evaluated for potential secondary causes of hypertension. Evidence-based management of resistant hypertension is discussed with special considerations of the differences in approach to patients with and without CKD, including the specific roles of diuretics and mineralocorticoid receptor antagonists and the current place of emerging therapies, such as renal denervation and baroreceptor stimulation. We endorse use of such a systematic approach to improve recognition and care for this vulnerable patient group that is at high risk for future kidney and cardiovascular events.

An angiotensin II type 1 receptor binding molecule has a critical role in hypertension in a chronic kidney disease model

Angiotensin II type 1 receptor-associated protein (ATRAP) promotes AT1R internalization along with suppression of hyperactivation of tissue AT1R signaling. Here, we provide evidence that renal ATRAP plays a critical role in suppressing hypertension in a mouse remnant kidney model of chronic kidney disease. The effect of 5/6 nephrectomy on endogenous ATRAP expression was examined in the kidney of C57BL/6 and 129/Sv mice. While 129/Sv mice with a remnant kidney showed decreased renal ATRAP expression and developed hypertension, C57BL/6 mice exhibited increased renal ATRAP expression and resistance to progressive hypertension. Consequently, we hypothesized that downregulation of renal ATRAP expression is involved in pathogenesis of hypertension in the remnant kidney model of chronic kidney disease. Interestingly, 5/6 nephrectomy in ATRAP-knockout mice on the hypertension-resistant C57BL/6 background caused hypertension with increased plasma volume. Moreover, in knockout compared to wild-type C57BL/6 mice after 5/6 nephrectomy, renal expression of the epithelial sodium channel α-subunit and tumor necrosis factor-α was significantly enhanced, concomitant with increased plasma membrane angiotensin II type 1 receptor in the kidneys. Thus, renal ATRAP downregulation is involved in the onset and progression of blood pressure elevation caused by renal mass reduction, and implicates ATRAP as a therapeutic target for hypertension in chronic kidney disease.

The Triad of Sleep Apnea, Hypertension, and Chronic Kidney Disease: A Spectrum of Common Pathology

Obstructive sleep apnea (OSA), hypertension, and chronic kidney disease (CKD) are different entities and are generally managed individually most of the time. However, CKD, OSA, and hypertension share many common risk factors and it is not uncommon to see this complex triad together. In fact, they share similar pathophysiology and have been interlinked with each other. The common pathophysiology includes chronic volume overload, hyperaldosteronism, increased sympathetic activity, endothelial dysfunction, and increased inflammatory markers. The combination of this triad has significant negative impact on the cardiovascular health, and increases the mortality and morbidity in this complicated group of patients. On one hand, progression of CKD can lead to the worsening of OSA and hypertension; similarly, worsening sleep apnea can make the hypertension difficult to treat and enhance the progression of CKD. This review article highlights the bidirectional interlink among these apparently different disease processes which share common pathophysiological mechanisms and emphasizes the importance of treating them collectively to improve outcomes.

Association of interleukin 17 / angiotensin II with refractory hypertension risk in hemodialysis patients

OBJECTIVE

The study was performed to investigate the association of interleukin 17 (IL 17) or angiotensin II (Ang II) with refractory hypertension risk in hemodialysis patients.

METHODS

Ninety hemodialysis patients were enrolled into this study, and those with hypertension were divided into two groups. The Easy-to-Control Hypertension group (ECHG) had fifty patients, while the refractory hypertension group (RHG) had forty patients. Twenty healthy individuals were recruited as the control group. IL17 and Ang II were determined using a human IL 17 / Ang II enzyme-linked immunosorbent assay kit. Serum IL 17 and Ang II concentrations in RHG patients were higher than those in ECHG patients.

RESULTS

Serum IL 17 and Ang II concentrations in both patient groups were higher than those in the control group. Linear regression analysis showed a positive correlation between IL 17 and Ang II. In multivariate regression analysis, we found that IL17 and Ang II were associated with refractory hypertension risk in hemodialysis patients.

CONCLUSION

IL17 and Ang II were associated with refractory hypertension risk in hemodialysis patients. There was also a positive correlation between IL 17and Ang II.

Renal Resistive Index Predicts Postoperative Blood Pressure Outcome in Primary Aldosteronism

The renal resistive index (RI) calculated by Doppler ultrasonography has been reported to be correlated with renal structural changes and outcomes in patients with essential hypertension or renal disease. However, little is known about this index in primary aldosteronism. In this prospective study, we examined the utility of this index to predict blood pressure (BP) outcome after adrenalectomy in patients with primary aldosteronism. We studied 94 patients with histopathologically proven aldosteronoma who underwent surgery. Parameters on renal function, including renal flow indices, were examined and followed up for 12 months postoperatively. The renal RI of the main, hilum, and interlobar arteries was significantly higher in patients with aldosteronoma compared with 100 control patients. BP, estimated glomerular filtration rate, and urinary albumin excretion significantly decreased after adrenalectomy. The resistive indices of all compartment arteries were significantly reduced 1 month after adrenalectomy and remained stable for 12 months. Patients whose interlobar RI was in the highest tertile at baseline had higher systolic BP after adrenalectomy than those whose RI was in the lowest tertile. Logistic regression analysis demonstrated that the RI of the interlobar and hilum arteries could be an independent predictive marker for intractable hypertension (systolic BP ≥140 mm Hg, increased BP, taking ≥3 antihypertensive agents, or increased number of agents) even after adrenalectomy. Therefore, in patients with aldosteronoma, the renal RI indicates partially reversible renal hemodynamics and renal structural damages that would influence postoperative BP outcome.

Prevalence and Prognostic Significance of Apparent Treatment Resistant Hypertension in Chronic Kidney Disease: Report From the Chronic Renal Insufficiency Cohort Study

The association between apparent treatment resistant hypertension (ATRH) and clinical outcomes is not well studied in chronic kidney disease. We analyzed data on 3367 hypertensive participants in the Chronic Renal Insufficiency Cohort (CRIC) to determine prevalence, associations, and clinical outcomes of ATRH in nondialysis chronic kidney disease patients. ATRH was defined as blood pressure ≥140/90 mm Hg on ≥3 antihypertensives, or use of ≥4 antihypertensives with blood pressure at goal at baseline visit. Prevalence of ATRH was 40.4%. Older age, male sex, black race, diabetes mellitus, and higher body mass index were independently associated with higher odds of having ATRH. Participants with ATRH had a higher risk of clinical events than participants without ATRH-composite of myocardial infarction, stroke, peripheral arterial disease, congestive heart failure (CHF), and all-cause mortality (hazard ratio [95% confidence interval], 1.38 [1.22-1.56]); renal events (1.28 [1.11-1.46]); CHF (1.66 [1.38-2.00]); and all-cause mortality (1.24 [1.06-1.45]). The subset of participants with ATRH and blood pressure at goal on ≥4 medications also had higher risk for composite of myocardial infarction, stroke, peripheral arterial disease, CHF, and all-cause mortality (hazard ratio [95% confidence interval], (1.30 [1.12-1.51]) and CHF (1.59 [1.28-1.99]) than those without ATRH. ATRH was associated with significantly higher risk for CHF and renal events only among those with estimated glomerular filtration rate ≥30 mL/min per 1.73 m(2). Our findings show that ATRH is common and associated with high risk of adverse outcomes in a cohort of patients with chronic kidney disease. This underscores the need for early identification and management of patients with ATRH and chronic kidney disease.

Obesity, albuminuria, and gamma-glutamyl transferase predict incidence of hypertension in indigenous Australians in rural and remote communities in northern Australia

OBJECTIVE

To describe the incidence of hypertension in a cohort of Australian Aboriginal and Torres Strait Islanders.

METHOD

A follow-up study conducted among 1831 indigenous population aged 15 years and over without hypertension at baseline from 19 communities in North Queensland during 1997-2008. Main measurements included baseline and follow-up weight, waist circumference, blood pressure, fasting glucose, lipids (triglycerides and cholesterol), gamma-glutamyl transferase, urinary albumin creatinine ratio, self-reported tobacco smoking, alcohol intake and physical activity.

RESULTS

Hundred cases of hypertension developed over 2633.4 person-years giving a crude incidence of hypertension of 22.6 (16.2-31.4) per 1000 person-years in females and 60.0 (47.1-76.6) per 1000 person-years for males. Age standardized overall incidence was 51.9 per 1000 person-years. Aboriginal participants were twice as likely as Torres Strait Islanders to develop hypertension, which increased with age. Obesity (BMI >30) strongly predicted incident hypertension independently of age or sex (adjusted hazard ratio 2.9, 95% confidence interval 1.9-4.8). Albuminuria and elevated gamma-glutamyl transferase increased the risk of hypertension (adjusted hazard ratio 1.4-1.7) in this population.

CONCLUSION

Incidence of hypertension in indigenous Australian adults is nearly double than that of the general Australian population. High background prevalence of obesity, diabetes and albuminuria contributes to this excess. As well as early detection and management of high blood pressure, albuminuria and diabetes in primary care settings, attention should be equally focused on community-level prevention and management of obesity.

Clinical and demographic characteristics of chronic kidney disease patients in a tertiary facility in Ghana

Introduction

Chronic kidney disease (CKD) has emerged as a public health challenge in countries around the world. The cost of management of CKD is enormous and unaffordable to most patients in the developing world. There is a dearth of data on characteristics of Ghanaian CKD patients at presentation.

Methods

This was a prospective cross sectional study of CKD patients during their first visit to the renal clinic of a tertiary hospital adult renal service. Following informed consent, a questionnaire was used to gather demographic, anthropometric and clinical details of patients. Laboratory data of patients were also collected and analysed.

Results

The majority (64.5%) of 203 participants were male. Most were less than 60 years old and about one third were unemployed. Across all age groups stage 5 disease was the commonest presentation; however only 4.3% could afford to initiate haemodialysis. The mean number of dialysis sessions was 12.4 (range 6-18). Chronic glomerulonephritis (33%), hypertension (21.2%) and diabetes mellitus (22.2%) were found to be the leading causes of CKD. Common complications of CKD at presentation included anaemia (86.7%), pulmonary oedema (31%), high blood pressure (55%), and infection.

Conclusion

Early detection of CKD and institution of measures to slow disease progression are to be encouraged. There is the need to make renal replacement therapy increasingly accessible and affordable to patients.

Clinical characteristics of resistant hypertension evaluated by ambulatory blood pressure monitoring

Strict control of blood pressure is important to prevent cardiovascular disease, although it is sometimes difficult to decrease blood pressure to target levels. The aim of this study was to investigate the clinical characteristics of resistant hypertension evaluated by ambulatory blood pressure monitoring. One hundred in-hospital patients, whose 24-hour average blood pressure was higher than 130/80 mmHg even after treatment with more than three antihypertensive drugs, were included in the present analysis. Circadian variation of blood pressure was evaluated by nocturnal fall in systolic blood pressure. Average blood pressures of all patients were high in both daytime and nighttime, 150.0/82.9 and 143.8/78.2 mmHg, respectively. Twenty patients had been treated with hemodialysis or peritoneal dialysis. In 63 patients out of the other 80 patients (79%), estimated glomerular filtration rate (eGFR) was also decreased (<60 mL/min/1.73 m²). The patients classified into dipper, non-dipper, riser and extreme-dipper were 20%, 43%, 34% and 3%, respectively. In addition, in 17 patients whose eGFR was preserved, 12 patients showed a non-dipper or riser pattern, suggesting that it was difficult to account for this altered circadian blood pressure variation only by renal dysfunction. These results show that a large number of the patients with resistant hypertension suffered from renal dysfunction, although it was difficult to explain altered circadian blood pressure variation based on renal dysfunction alone.

Prevalence of apparent treatment-resistant hypertension among individuals with CKD

BACKGROUND AND OBJECTIVES

Apparent treatment-resistant hypertension is defined as systolic/diastolic BP ≥ 140/90 mmHg with concurrent use of three or more antihypertensive medication classes or use of four or more antihypertensive medication classes regardless of BP level.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

The prevalence of apparent treatment-resistant hypertension among Reasons for Geographic and Racial Differences in Stroke study participants treated for hypertension (n=10,700) was determined by level of estimated GFR and albumin-to-creatinine ratio, and correlates of apparent treatment-resistant hypertension among those participants with CKD were evaluated. CKD was defined as an albumin-to-creatinine ratio ≥ 30 mg/g or estimated GFR<60 ml/min per 1.73 m(2).

RESULTS

The prevalence of apparent treatment-resistant hypertension was 15.8%, 24.9%, and 33.4% for those participants with estimated GFR ≥ 60, 45-59, and <45 ml/min per 1.73 m(2), respectively, and 12.1%, 20.8%, 27.7%, and 48.3% for albumin-to-creatinine ratio<10, 10-29, 30-299, and ≥ 300 mg/g, respectively. The multivariable-adjusted prevalence ratios (95% confidence intervals) for apparent treatment-resistant hypertension were 1.25 (1.11 to 1.41) and 1.20 (1.04 to 1.37) for estimated GFR levels of 45-59 and <45 ml/min per 1.73 m(2), respectively, versus ≥ 60 ml/min per 1.73 m(2) and 1.54 (1.39 to 1.71), 1.76 (1.57 to 1.97), and 2.44 (2.12 to 2.81) for albumin-to-creatinine ratio levels of 10-29, 30-299, and ≥ 300 mg/g, respectively, versus albumin-to-creatinine ratio<10 mg/g. After multivariable adjustment, men, black race, larger waist circumference, diabetes, history of myocardial infarction or stroke, statin use, and lower estimated GFR and higher albumin-to-creatinine ratio levels were associated with apparent treatment-resistant hypertension among individuals with CKD.

CONCLUSIONS

This study highlights the high prevalence of apparent treatment-resistant hypertension among individuals with CKD.

The neural regulation of the kidney in hypertension and renal failure

NEW FINDINGS

What is the topic of this review? Reports that bilateral renal denervation in resistant hypertensive patients results in a long-lasting reduction in blood pressure raise the question of the underlying mechanisms involved and how they may be deranged in pathophysiological states of hypertension and renal failure. What advances does it highlight? The renal sensory afferent nerves and efferent sympathetic nerves work together to exert an important control over extracellular fluid volume, hence the level at which blood pressure is set. This article emphasizes that both the afferent and the efferent renal innervation may contribute to the neural dysregulation of the kidney that occurs in chronic renal disease and resistant hypertension. Autonomic control is central to cardiovascular homeostasis, and this is exerted not only at the level of the heart and blood vessels but also at the kidney. At the kidney, the sympathetic neural regulation of renin release and fluid reabsorption may influence fluid balance and, in the longer term, the level at which blood pressure is set. The role of the renal innervation in the regulation of blood pressure has received renewed attention over the past few years, following the reports that bilateral renal denervation of resistant hypertensive patients resulted in a marked reduction in blood pressure, which has been maintained for several years. Such has been the interest that this approach of renal denervation is being applied in other patient groups with diabetes, obesity and renal failure, with the hope that there may be a sustained reduction in blood pressure as well as the amelioration of some aspects of the metabolic syndrome. However, the factors that come into play to cause the rise in blood pressure in these patient groups, particularly the resistant hypertensive patients, are far from clear. Moreover, the mechanisms leading to the fall in blood pressure following renal denervation of resistant hypertensive patients currently elude our understanding and is therefore an area that requires much more investigation to enhance our insight.

Utility of bioimpedance spectroscopy (BIS) in the management of refractory hypertension in patients with chronic kidney disease (CKD)

BACKGROUND

Expansion of extracellular volume (ECV) is a frequent cause of resistant hypertension (RHT) in patients with chronic kidney disease (CKD). The aim of this exploratory study was that of applying bioimpedance spectroscopy (BIS) for the identification of CKD patients with RHT and expansion of ECV, while trying to control blood pressure (BP) using an intensification of diuretic treatment.

METHODS

We included 50 patients with RHT and CKD who underwent BIS. In order to control BP, diuretic treatment was intensified in those patients with expansion of the ECV. In all other cases, another antihypertensive drug was added.

RESULTS

The mean age was 68.2 ± 10.4 years, 68% were male and 58% were diabetic. The mean estimated glomerular filtration rate (eGFR) was 50.7 ± 22.4 mL/min/1.72 m(2). Baseline systolic BP was 167.2 ± 8.6 mmHg and diastolic BP was 84.8 ± 9.5 mmHg. The mean number of antihypertensive drugs received was 3.8 ± 0.9. Expansion of ECV was recorded in 30 (60%) patients and was more frequent in diabetics and in patients with more albuminuria. At 6 months of follow-up, a decline of 21.4 ± 7.1 mmHg was observed in systolic BP in the patients with expansion of ECV, compared with a decrease of 9.4 ± 3.4 mmHg in the normal ECV group (P < 0.01). We did not find differences in the decrease in diastolic BP between the groups. Nine patients (30%) with ECV expansion who increased diuretic therapy reached the target blood pressure (BP) of <140/90 mmHg, when compared with only two patients (10%) who had normal ECV and in whom other antihypertensive drug was added. A total decrease in body water of 1.9 ± 1.1 L was observed in patients with ECV expansion who intensified diuretic treatment at the expense of a decline in ECV of 1.1 ± 1 L. eGFR remained stable in both groups (47.1 ± 21.1 versus 54.1 ± 25.2 mL/min/1.73 m(2); P = 0.37).

CONCLUSIONS

An increase in ECV as measured by BIS frequently occurs in RHT in patients with CKD. Diabetic and severe proteinuric patients are more exposed to expansion of ECV. BIS is a potentially useful method for identifying and treating patients with RHT and expansion of ECV. The hypothesis generated by this exploratory study needs to be tested in a randomized clinical trial.

Health risk factors and the incidence of hypertension: 4-year prospective findings from a national cohort of 60 569 Thai Open University students

OBJECTIVE

This study evaluates the impact of a number of demographic, biological, behavioural and lifestyle health risk factors on the incidence of hypertension in Thailand over a 4-year period.

DESIGN

A 4-year prospective study of health risk factors and their effects on the incidence of hypertension in a national Thai Cohort Study from 2005 to 2009.

SETTING

As Thailand is transitioning from a developing to a middle-income developed country, chronic diseases (particularly cardiovascular disease) have emerged as major health issues. Hypertension is a major risk factor for heart attack and stroke and cross-sectional studies have indicated that the prevalence is increasing.

STUDY PARTICIPANTS

A total of 57 558 Sukhothai Thammathirat Open University students who participated in both the 2005 and 2009 questionnaire surveys and who were normotensive in 2005 were included in the analysis.

MEASURES

Adjusted relative risks associating each risk factor and incidence of hypertension by sex, after controlling for confounders such as age, socioeconomic status, body mass index (BMI) and underlying diseases.

RESULTS

The overall 4-year incidence of hypertension was 3.5%, with the rate in men being remarkably higher than that in women (5.2% vs 2.1%). In both sexes, hypertension was associated with age, higher BMI and comorbidities but not with income and education. In men, hypertension was associated with physical inactivity, smoking, alcohol and fast food intake. In women, hypertension was related to having a partner.

CONCLUSIONS

In both men and women, hypertension was strongly associated with age, obesity and comorbidities while it had no association with socioeconomic factors. The cohort patterns of socioeconomy and hypertension reflect that the health risk transition in Thais is likely to be at the middle stage. Diet and lifestyle factors associate with incidence of hypertension in Thais and may be amenable targets for hypertension control programmes.

Pharmacologic treatment of hypertension in patients with chronic kidney disease

Hypertension remains an important cause of morbidity and mortality in patients with chronic kidney disease. It both contributes to and is a consequence of chronic renal dysfunction. There is a high prevalence of hypertension in chronic kidney disease, and rates of control remain sub-optimal. Numerous studies have highlighted the benefit of treating hypertension in reducing the overall mortality as well as progression of renal disease in this population. Non-pharmacologic treatment strategies remain the primary intervention in all patients but are insufficient on their own to control hypertension in most cases. Pharmacologic treatment recommendations, however, vary depending on the specific etiology of disease as well as patient characteristics. Though most classes of anti-hypertensive drugs can be used to lower blood pressure in chronic kidney disease, therapy needs to be selected based on the presence of specific co-morbidities as well as the etiology of the kidney disease. Most patients will require multi-drug therapy for achieving target blood pressure goals. This review discusses the pharmacologic options in management of hypertension in various forms of chronic kidney disease.

Identifying patients with resistant hypertension and options for clinical management

In addition to the increasing prevalence of hypertension, the number of patients with treatment-resistant hypertension is also rising. It is important to identify these patients in order to improve the treatment outcomes and to screen for potential secondary causes. Clinical characteristics of patients with resistant hypertension include advanced age, male gender, obesity, high salt intake and alcohol consumption. Those with high baseline blood pressure, diabetes, chronic kidney disease or obstructive sleep apnea are also prone to developing resistant hypertension. Physicians should initiate close monitoring and aggressive treatment for those patients, as resistant hypertension is associated with a higher risk of cardiovascular morbidities, regardless of the control of blood pressure. However, treatment of resistant hypertension is currently a great challenge in clinical practice as all of these patients are already taking multiple antihypertensive medications, including the first-line treatments advocated in guidelines. In patients who have been presented multiple drugs, the room for further titration is often limited. Spironolactone has been demonstrated to be effective as an add-on therapy for patients with resistant hypertension. In addition to drug treatment, baroreceptor stimulation therapy and renal sympathetic denervation are promising new approaches in this group of patients. Further studies on the pathogenesis and the treatment of resistant hypertension would help to improve the outcome of this patient subgroup.

Resistant hypertension in nondialysis chronic kidney disease

Resistant hypertension (RH) is defined as blood pressure (BP) that remains above the target of less than 140/90 mmHg in the general population and 130/80 mmHg in people with diabetes mellitus or chronic kidney disease (CKD) in spite of the use of at least three full-dose antihypertensive drugs including a diuretic or as BP that reaches the target by means of four or more drugs. In CKD, RH is a common condition due to a combination of factors including sodium retention, increased activity of the renin-angiotensin system, and enhanced activity of the sympathetic nervous system. Before defining the hypertensive patient as resistant it is mandatory to exclude the so-called “pseudoresistance.” This condition, which refers to the apparent failure to reach BP target in spite of an appropriate antihypertensive treatment, is mainly caused by white coat hypertension that is prevalent (30%) in CKD patients. Recently we have demonstrated that “true” RH represents an independent risk factor for renal and cardiovascular outcomes in CKD patients.

Autonomic regulation of kidney function

The kidneys play a central role in cardiovascular homeostasis by ensuring a balance between the fluid taken in and that lost and excreted during everyday activities. This ensures stability of extracellular fluid volume and maintenance of normal levels of blood pressure. Renal fluid handling is controlled via neural and humoral influences, with the former determining a rapid dynamic response to changing intake of sodium whereas the latter cause a slower longer-term modulation of sodium and water handling. Activity in the renal sympathetic nerves arises from an integration of information from the high and low pressure cardiovascular baroreceptors, the somatosensory and visceral systems as well as the higher cortical centers. Each sensory system provides varying input to the autonomic centers of the hypothalamic and medullary areas of the brain at a level appropriate to the activity being performed. In pathophysiological states, such as hypertension, heart failure and chronic renal disease, there may be an inappropriate sympathoexcitation causing sodium retention which exacerbates the disease process. The contribution of the renal sympathetic nerves to these cardiovascular diseases is beginning to be appreciated with the demonstration that renal denervation of resistant hypertensive patients results in a long-term normalization of blood pressure.

Resistant hypertension and obstructive sleep apnea in the setting of kidney disease

OBJECTIVES

To explore the relationship between obstructive sleep apnea (OSA) and resistant hypertension in chronic kidney disease (CKD) and end-stage renal disease (ESRD).

METHODS

We examined sleep parameters and blood pressure (BP) in 224 community-based, non-CKD participants from the Sleep-SCORE study: 88 nondialysis-dependent CKD and 95 ESRD participants. Unattended home polysomnography with standardized scoring protocols and automated BP monitors were used. Resistant hypertension was defined as a BP of at least 140/90  mmHg despite at least three antihypertensive drugs.

RESULTS

Mean SBP of the CKD and ESRD groups were significantly higher than that of the non-CKD group [148.2 (23.8), 144.5 (26.7) vs. 132.2  mmHg (26.7), respectively; P < 0.0001] despite the use of more antihypertensive medications. The CKD and ESRD groups had higher rates of resistant hypertension than the non-CKD group (41.4, 22.6 vs. 6.7%, respectively; P < 0.0001). The severity of sleep apnea was associated with a higher risk of resistant hypertension. Although resistant hypertension was associated with severe sleep apnea in participants with ESRD [odds ratio (OR) 7.1, 95% confidence interval (CI) 2.2-23.2), there was no significant association in the non-CKD (OR 3.5, 95% CI 0.8-15.4) or CKD groups (OR 1.2, 95% CI 0.4-3.7) after accounting for case-mix.

CONCLUSION

The association between resistant hypertension and sleep apnea appeared robust in ESRD. OSA may contribute to resistant hypertension or both may be linked to a common underlying process such as volume excess. Future studies in patients with kidney disease should further characterize the resistant hypertension-OSA relationship and determine whether treatment of underlying mechanisms may improve outcomes.

Baseline characteristics of subjects enrolled in the Evaluation of Cinacalcet HCl Therapy to Lower Cardiovascular Events (EVOLVE) trial

BACKGROUND

Secondary hyperparathyroidism (sHPT) and other abnormalities associated with chronic kidney disease-mineral bone disorder can contribute to dystrophic (including vascular) calcification. Dietary modification and variety of medications can be used to attenuate the severity of sHPT. However, it is unknown whether any of these approaches can reduce the high risks of death and cardiovascular disease in patients with end-stage renal disease.

METHODS

The Evaluation of Cinacalcet HCl Therapy to Lower Cardiovascular Events (EVOLVE) trial was designed to test the hypothesis that treatment with the calcimimetic agent cinacalcet compared with placebo (on a background of conventional therapy including phosphate binders +/- vitamin D sterols) reduces time to death or non-fatal cardiovascular events (specifically myocardial infarction, unstable angina, heart failure and peripheral arterial disease events) among patients on hemodialysis with sHPT. This report describes baseline characteristics of enrolled subjects with a focus on regional variation.

RESULTS

There were 3883 subjects randomized from 22 countries, including the USA, Canada, Australia, three Latin American nations, Russia and 15 European nations. The burden of overt cardiovascular disease at baseline was high (e.g. myocardial infarction 12.4%, heart failure 23.3%). The median plasma parathyroid hormone concentration at baseline was 692 pg/mL (10%, 90% range, 363-1694 pg/mL). At baseline, 87.2% of subjects were prescribed phosphate binders and 57.5% were prescribed activated vitamin D derivatives. Demographic data, comorbid conditions and baseline laboratory data varied significantly across regions.

CONCLUSIONS

EVOLVE enrolled 3883 subjects on hemodialysis with moderate to severe sHPT. Inclusion of subjects from multiple global regions with varying degrees of disease severity will enhance the external validity of the trial results.