Effect of cinacalcet on cardiovascular disease in patients undergoing dialysis

Vitamin D and chronic kidney disease-mineral bone disease (CKD-MBD)

Chronic kidney disease (CKD) is a modern day epidemic and has significant morbidity and mortality implications. Mineral and bone disorders are common in CKD and are now collectively referred to as CKD- mineral and bone disorder (MBD). These abnormalities begin to appear even in early stages of CKD and contribute to the pathogenesis of renal osteodystrophy. Alteration in vitamin D metabolism is one of the key features of CKD-MBD that has major clinical and research implications. This review focuses on biology, epidemiology and management aspects of these alterations in vitamin D metabolism as they relate to skeletal aspects of CKD-MBD in adult humans.

Cardiorenal syndrome

Cardiorenal syndrome (CRS) includes a broad spectrum of diseases within which both the heart and kidneys are involved, acutely or chronically. An effective classification of CRS in 2008 essentially divides CRS in two main groups, cardiorenal and renocardiac CRS, based on primum movens of disease (cardiac or renal); both cardiorenal and renocardiac CRS are then divided into acute and chronic, according to onset of disease. The fifth type of CRS integrates all cardiorenal involvement induced by systemic disease. This article addresses the pathophysiology, diagnosis, treatment, and outcomes of the 5 distinct types of CRS.

Leptin promotes the osteoblastic differentiation of vascular smooth muscle cells from female mice by increasing RANKL expression

Arterial calcification is a complex and active regulated process, which results from a process of osteoblastic differentiation of vascular smooth muscle cells (VSMCs). Leptin, the product of the ob gene, mainly regulates food intake and energy expenditure and recently has been considered to be correlated with the arterial calcification. However, the mechanisms of the effects of leptin on osteoblastic differentiation of VSMCs are unknown. We used calcifying vascular smooth muscle cells (CVSMCs) as a model to investigate the relationship between leptin and the osteoblastic differentiation of CVSMCs and the signaling pathways involved. Our experiments demonstrated that leptin could increase expression of receptor activator of nuclear factor-κB ligand (RANKL) and bone morphogenetic protein 4 (BMP4), as well as alkaline phosphatase (ALP) activity, runt-related transcription factor 2 expression, calcium deposition, and the formation of mineralized nodules in CVSMCs. Suppression of RANKL with small interfering RNA abolished the leptin-induced ALP activity and BMP4 expression in CVSMCs. Leptin could activate the ERK1/2 and phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway. Furthermore, pretreatment with the ERK inhibitor PD98059 and the PI3K inhibitor LY294002 abolished leptin-induced RANKL expression and blocked the promotion of ALP activity of CVSMCs. Silencing of the leptin receptor OB-Rb with small interfering RNA abolished leptin-induced activation of ERK and Akt and the expression of RANKL and reversed the effects of leptin on ALP activity. Meanwhile, addition of Noggin (the BMP4 inhibitor) blunted the effect of leptin on ALP activity. These results show that leptin can promote osteoblastic differentiation of CVSMCs by the OB-Rb/ERK1/2/RANKL-BMP4 and OB-Rb/PI3K/Akt/RANKL-BMP4 pathways.

Parathyroid scintigraphy in renal hyperparathyroidism: the added diagnostic value of SPECT and SPECT/CT

Secondary hyperparathyroidism (sHPT) is a major complication for patients with end-stage renal disease on long-term hemodialysis or peritoneal dialysis. When the disease is resistant to medical treatment, patients with severe sHPT are typically referred for parathyroidectomy (PTx), which usually improves biological parameters as well as clinical signs and symptoms. Unfortunately, early surgical failure with persistent disease may occur in 5%-10% of patients and recurrence reaches 20%-30% at 5 years. Presently, the use of parathyroid scintigraphy in sHPT is usually limited to the management of surgical failures after initial PTx. This review describes the strengths and limitations of typical (99m)Tc-sestamibi imaging protocols, and highlights the potential benefits of using parathyroid scintigraphy in the initial workup of surgical patients.

Serum potassium levels and its variability in incident peritoneal dialysis patients: associations with mortality

Background

Abnormal serum potassium is associated with an increased risk of mortality in dialysis patients. However, the impacts of serum potassium levels on short- and long-term mortality and association of potassium variability with death in peritoneal dialysis (PD) patients are uncertain.

Methods

We examined mortality-predictability of serum potassium at baseline and its variability in PD patients treated in our center January 2006 through December 2010 with follow-up through December 2012. The hazard ratios (HRs) were used to assess the relationship between baseline potassium levels and short-term (≤1 year) as well as long-term (>1 year) survival. Variability of serum potassium was defined as the coefficient of variation of serum potassium (CVSP) during the first year of PD.

Results

A total of 886 incident PD patients were enrolled, with 248 patients (27.9%) presented hypokalemia (serum potassium <3.5 mEq/L). During a median follow-up of 31 months (range: 0.5–81.0 months), adjusted all-cause mortality hazard ratio (HR) and 95% confidence interval (CI) for baseline serum potassium of <3.0, 3.0 to <3.5, 3.5 to <4.0, 4.5 to <5.0, and ≥5.0 mEq/L, compared with 4.0 to <4.5 (reference), were 1.79 (1.02–3.14), 1.15 (0.72–1.86), 1.31 (0.82–2.08), 1.33 (0.71–2.48), 1.28 (0.53–3.10), respectively. The increased risk of lower potassium with mortality was evident during the first year of follow-up, but vanished thereafter. Adjusted all-cause mortality HR for CVSP increments of 7.5% to <12.0%; 12.0% to <16.7% and ≥16.7%, compared with <7.5% (reference), were 1.35 (0.67–2.71), 2.00 (1.05–3.83) and 2.18 (1.18–4.05), respectively. Similar association was found between serum potassium levels and its variability and cardiovascular mortality.

Conclusions

A lower serum potassium level was associated with all-cause and cardiovascular mortality during the first year of follow-up in incident PD patients. In addition, higher variability of serum potassium levels conferred an increased risk of death in this population.

Extraosseous calcification in end-stage renal disease: from visceral organs to vasculature

In earlier days, periarticular accumulations of calcium phosphate causing tumor-like depositions were considered the result of passive precipitation and referred to as metastatic calcifications. From sophisticated computer tomographic studies and growing insight, we have learned that calcifications in the cardiovascular system are far more threatening and in fact one of the most important sequela of end-stage renal disease. The histologic characteristic of uremia-related calcification is arteriosclerosis of the media. In addition, there is atherosclerosis of the intima, due to the high prevalence of classic cardiovascular risk factors in renal disease. The two vascular features can frequently exist at different sites in the vasculature. Novel diagnostic techniques are helping to elucidate the pathogenetic mechanisms of active conversion of vascular smooth muscle cells to osteochondritic cells. Through this process, extensive calcification of the central and peripheral vasculature ensues, influenced by different promotors and inhibitors. Calciphylaxis is a special form of extraosseous calcification leading to skin necrosis. The factors that trigger the development of calciphylaxis are not completely understood, but this syndrome shares part of the pathophysiologic basis of extraosseous calcification in general. However, the therapeutic approach must be prompt and aggressive, because of the poor prognosis. Frequently, a fatal outcome cannot be avoided in calciphylaxis.

Vascular calcification

PURPOSE OF REVIEW

This review presents new evidence related to molecular mechanisms involved in the process of cardiovascular calcification, as well as to discuss new biomarkers and novel therapeutic strategies related to vascular calcification in chronic kidney disease (CKD) patients.

RECENT FINDINGS

microRNAs have emerged as potential players in the genesis of osteo-chondrogenic transformation, depending on the stimulus and the localization of vascular calcification. The disturbances of the fibroblast growth factor-23 (FGF23)/alpha-Klotho (Klotho) axis observed in CKD appear to play an important role in CKD-associated vascular calcification. Numerous studies have identified circulating biomarkers potentially responsible for vascular calcification and have evaluated their link with this process. The respective role of these biomarkers is not yet elucidated. Beyond phosphate binders, modulation of calcium-sensing receptor and vitamin K supplementation come into sight as new potential strategies to prevent cardiovascular calcification.

CONCLUSION

A better understanding of the molecular mechanisms which are responsible for cardiovascular calcification have led to a better detection and more adequate follow-up of this pathologic process, as well as the identification of novel therapeutic targets. Whether these new insights will lead to improved care and better survival of CKD patients with cardiovascular calcification remains to be demonstrated.

Calcitriol resistance in hemodialysis patients with secondary hyperparathyroidism

Nonselective vitamin D receptor activators (VDRA), such as calcitriol and alfacalcidol, have been successfully used in the treatment of secondary hyperparathyroidism (SHPT) in hemodialysis. Despite their beneficial effects on the control of serum PTH levels, their use has been limited by intolerance (development of hypercalcemia and hyperphosphatemia with consecutive cardiovascular toxicity). Apart from becoming intolerant, in 20-30 % of patients who use nonselective VDRA, serum PTH levels do not decrease appropriately despite increasing doses of these agents. These patients are considered calcitriol-resistant patients. Thus, calcitriol resistance and intolerance are two sides of the same coin: active vitamin D failure. Despite the clinical relevance of active vitamin D failure, definitions of resistance and intolerance are imprecise and have varied over time. More selective VDRA claim to produce less hypercalcemia and hyperphosphatemia and could help clinicians to overcome intolerance. Also, some studies have also shown that paricalcitol can be even useful in resistant patients. Significant limitations of iPTH as a reliable and useful clinical biomarker have been increasingly appreciated. There is evidence that intact PTH concentration must differ by 72 % between any two measurements before it can be considered a significant change. VDR polymorphisms could be involved in the development of SHPT in CKD patients. Interestingly, a higher incidence of the b allele of the VDR BsmI gene variant has been shown to be present in SHPT. The BsmI genotype can also affect the response of hemodialysis to IV calcitriol. A challenge for the future will be to establish biomarkers such as laboratory determinations or ultrasound findings that can help us to early identify those patients who will not respond appropriately to calcitriol or exhibit intolerable side effects .

Fitness for Entering a Simple Exercise Program and Mortality: A Study Corollary to the Exercise Introduction to Enhance Performance in Dialysis (Excite) Trial

<b><i>Background/Aims: </i></b>In this corollary analysis of the EXCITE study, we looked at possible differences in baseline risk factors and mortality between subjects excluded from the trial because non-eligible (n=216) or because eligible but refusing to participate (n=116). <b><i>Methods: </i></b>Baseline characteristics and mortality data were recorded. Survival and independent predictors of mortality were assessed by Kaplan-Meier and Cox regression analyses. <b><i>Results: </i></b>The incidence rate of mortality was higher in non-eligible vs. eligible non-randomized patients (21.0 vs. 10.9 deaths/100 persons-year; P<0.001). The crude excess risk of death in non-eligible patients (HR 1.96; 95% CI 1.36 to 2.77; P<0.001) was reduced after adjustment for risk factors which differed in the two cohorts including age, blood pressure, phosphate, CRP, smoking, diabetes, triglycerides, cardiovascular comorbidities and history of neoplasia (HR 1.60; 95% CI 1.10 to 2.35; P=0.017) and almost nullified after including in the same model also information on deambulation impairment (HR 1.16; 95% CI 0.75 to 1.80; P=0.513). <b><i>Conclusions: </i></b>Deambulation ability mostly explains the difference in survival rate in non-eligible and eligible non-randomized patients in the EXCITE trial. Extending data analyses and outcome reporting also to subjects not taking part in a trial may be helpful to assess the representability of the study population.

Phosphate: an old bone molecule but new cardiovascular risk factor

Phosphate handling in the body is complex and involves hormones produced by the bone, the parathyroid gland and the kidneys. Phosphate is mostly found in hydroxyapatite. however recent evidence suggests that phosphate is also a signalling molecule associated with bone formation. Phosphate balance requires careful regulation of gut and kidney phosphate transporters, SLC34 transporter family, but phosphate signalling in osteoblasts and vascular smooth muscle cells is likely mediated by the SLC20 transporter family (PiT1 and PiT2). If not properly regulated, phosphate imblanace could lead to mineral disorders as well as vascular calcification. In chronic kidney disease-mineral bone disorder, hyperphosphataemia has been consistently associated with extra-osseous calcification and cardiovascular disease. This review focuses on the physiological mechanisms involved in phosphate balance and cell signalling (i.e. osteoblasts and vascular smooth muscle cells) as well as pathological consequences of hyperphosphataemia. Finally, conventional as well as new and experimental therapeutics in the treatment of hyperphosphataemia are explored.

Dramatic alteration of the skull in a uremic patient with leontiasis ossea

The craniofacial skeleton represents a peculiar target of hyperparathyroidism in patients with end-stage renal disease who exhibit a dramatic pattern of uremic leontiasis ossea. Scant information regarding this condition is available in the renal literature, as the extreme and typical manifestations of leontiasis ossea have been described in only a small series of patients. We herein report a case of significant amelioration of massive modification of the facial appearance of a 30-year-old uremic Chinese woman with severe skeletal deformities who underwent total parathyroidectomy with a forearm autograft concurrently with effective drug treatment. This report may shed light on how to better understand and treat this metabolic derangement.

Ethnic differences in bone and mineral metabolism in healthy people and patients with CKD

Several studies have shown racial differences in the regulation of mineral metabolism, in the acquisition of bone mass and structure of individuals. In this review, we examine ethnic differences in bone and mineral metabolism in normal individuals and in patients with chronic kidney disease. Black individuals have lower urinary excretion and increased intestinal calcium absorption, reduced levels of 25(OH)D, and high levels of 1.25(OH)2D and parathyroid hormone (PTH). Body phosphorus concentration is higher and the levels of FGF-23 are lower than in whites. Mineral density and bone architecture are better in black individuals. These differences translate into advantages for blacks who have stronger bones, less risk of fractures, and less cardiovascular calcification. In the United States of America, the prevalence of kidney disease is similar in different ethnic groups. However, black individuals progress more quickly to advanced stages of kidney disease than whites. This faster progression does not translate into increased mortality, higher in whites, especially in the first year of dialysis. Some ethnicity-related variations in mineral metabolism persist when individuals develop CKD. Therefore, black patients have lower serum calcium concentrations, less hyperphosphatemia, low levels of 25(OH)D, higher levels of PTH, and low levels of FGF-23 compared with white patients. Bone biopsy studies show that blacks have greater bone volume. The rate of fractures and cardiovascular diseases are also less frequent. Further studies are required to better understand the cellular and molecular bases of these racial differences in bone mineral metabolism and thus better treat patients.

Long-term effect of cinacalcet hydrochloride on abdominal aortic calcification in patients on hemodialysis with secondary hyperparathyroidism

Background

Secondary hyperparathyroidism (SHPT) is one of the common complications in dialysis patients, and is associated with increased risk of vascular calcification. The effects of cinacalcet hydrochloride treatment on bone and mineral metabolism have been previously reported, but the benefit of cinacalcet on vascular calcification remains uncertain. The aim of this study was to evaluate the impact of cinacalcet on abdominal aortic calcification in dialysis patients.

Subjects and methods

Patients were on maintenance hemodialysis with insufficiently controlled SHPT (intact parathyroid hormone [PTH] >180 pg/mL) by conventional therapies. All subjects were initially administered 25 mg cinacalcet daily, with concomitant use of calcitriol analogs. Abdominal aortic calcification was annually evaluated by calculating aortic calcification area index (ACAI) using multidetector computed tomography (MDCT), from 12 months before to 36 months after the initiation of cinacalcet therapy.

Results

Twenty-three patients were analyzed in this study. The mean age was 59.0±8.7 years, 34.8% were women, and the mean dialysis duration was 163.0±76.0 months. After administration of cinacalcet, serum levels of intact PTH, phosphorus, and calcium significantly decreased, and mean Ca × P values significantly decreased from 67.4±7.9 mg²/dL² to 52±7.7 mg²/dL². Although the ACAI value did not decrease during the observation period, the increase in ACAI between 24 months and 36 months after cinacalcet administration was significantly suppressed.

Conclusion

Long-term administration of cinacalcet was associated with reduced progression of abdominal aortic calcification, and achieving appropriate calcium and phosphorus levels may reduce the rates of cardiovascular events and mortality in patients on hemodialysis.

Risk of sudden cardiac death in chronic kidney disease

The review discusses the epidemiology and the possible underlying mechanisms of sudden cardiac death (SCD) in chronic kidney disease (CKD), and highlights the unmet clinical need for noninvasive risk stratification strategies in these patients. Although renal dysfunction shares common risk factors and often coexists with atherosclerotic cardiovascular disease, the presence of renal impairment increases the risk of arrhythmic complications to an extent that cannot be explained by the severity of the atherosclerotic process. Renal impairment is an independent risk factor for SCD from the early stages of CKD; the risk increases as renal function declines and reaches very high levels in patients with end-stage renal disease on dialysis. Autonomic imbalance, uremic cardiomyopathy, and electrolyte disturbances likely play a role in increasing the arrhythmic risk and can be potential targets for treatment. Cardioverter defibrillator treatment could be offered as lifesaving treatment in selected patients, although selection strategies for this treatment mode are presently problematic in dialyzed patients. The review also examines the current experience with risk stratification tools in renal patients and suggests that noninvasive electrophysiological testing during dialysis may be of clinical value as it provides the necessary standardized environment for reproducible measurements for risk stratification purposes.

Optimizing the cost-effectiveness of treatment for chronic kidney disease-mineral and bone disorder

Chronic kidney disease-mineral and bone disorder (CKD-MBD) is an important risk factor in patients with CKD, and some medications for treating CKD-MBD have been recently marketed. Because assessment of health-care cost-effectiveness is growing in importance with increases in health expenditures, several cost-effectiveness analyses for new medications such as sevelamer, lanthanum carbonate, cinacalcet hydrochloride, and paricalcitol have been conducted. The results of these analyses have stimulated discussion on the efficient use of these medications and, in some cases, have affected treatment recommendation. However, most of these studies had methodological problems, one of them being that the effectiveness of medications was estimated based on changes of surrogate parameters, such as vascular calcification or serum biochemistry values. Furthermore, even if cost-effectiveness analyses were based on a given clinical trial, the results might differ from country to country. To provide greater health benefits under limited health expenditures based on the results of cost-effectiveness analyses, it is necessary to confirm the effectiveness of medications through well-designed clinical trials having mortality as the primary end point. In addition, cost-effectiveness analyses need to be performed separately for each country.

The clinical course of treated hyperparathyroidism among patients receiving hemodialysis and the effect of cinacalcet: the EVOLVE trial

CONTEXT

The clinical course of secondary hyperparathyroidism (sHPT) in patients on hemodialysis is not well described, and the effect of the calcimimetic cinacalcet on disease progression is uncertain.

OBJECTIVE

Our objective was to describe 1) the clinical course of sHPT in patients treated with phosphate binders and/or vitamin D sterols and 2) the impact of cinacalcet on the occurrence of severe unremitting HPT, defined by the persistence of markedly elevated PTH concentrations together with hypercalcemia or parathyroidectomy (PTX).

DESIGN AND SETTING

This was a randomized, double-blind, placebo-controlled, global, multicenter clinical trial.

PATIENTS

Of 5755 patients screened with moderate to severe sHPT, 3883 patients on hemodialysis were included in the trial.

MAIN OUTCOME MEASURES

Outcomes included PTX; severe, unremitting HPT; and use of commercial cinacalcet (a protocol violation).

INTERVENTION

Intervention was cinacalcet (30-180 mg daily) or placebo for up to 64 months.

RESULTS

In the 1935 patients randomized to placebo, 278 patients (14%) underwent PTX (median PTH 1872 pg/mL within the previous 12 weeks from surgery). Age, sex, geographic region, co-morbidity, calcium-containing phosphate binder use, and baseline serum calcium, phosphorus, and PTH concentrations were associated with PTX. Commercial cinacalcet was started in 443 (23%) patients (median PTH 1108 pg/mL before treatment began). Severe unremitting HPT developed in 470 patients (24%). In a multivariable Cox model, the relative hazard (comparing patients randomized to cinacalcet versus placebo) of severe unremitting HPT was 0.31 (95% confidence interval = 0.26-0.37). The relative hazard differed little when adjusted by baseline clinical characteristics.

CONCLUSIONS

Severe unremitting HPT develops frequently in patients on hemodialysis despite conventional therapy, and cinacalcet substantially reduces its occurrence.

Mechanisms of arterial calcifications and consequences for cardiovascular function

Cardiovascular complications are the leading cause of mortality in chronic (CKD) and end-stage renal disease (ESRD). The risk of developing cardiovascular complications is associated with changes in the structure and function of the arterial system, which are in many aspects similar to those occurring with aging. The presence of traditional risk factors does not fully explain the extension and severity of arterial disease. Therefore, other factors associated with CKD and ESRD must also be involved. Arterial calcification (AC) is a common complication of CKD and ESRD, and the extent of AC in general population as well as in patients with CKD is predictive of subsequent cardiovascular mortality beyond established conventional risk factors. AC is an active process similar to bone formation that implicates a variety of proteins involved in bone and mineral metabolism and is considered part of a systemic dysfunction defined as CKD-associated mineral and bone disorder (CKD-MBD).

Impact of cinacalcet introduction on MBD management: the MBD-5D study in Japan

Chronic kidney disease-mineral and bone disorder (CKD-MBD) has recently attracted attention in light of its association with clinical outcomes, such as fracture, cardiovascular disease, and mortality. Management of CKD-MBD has therefore come to have a central role in dialysis practice. Cinacalcet, a newly developed drug, has changed prescription patterns in many centers based on different changes in MBD markers than those observed with active vitamin D derivatives. As physicians require real-world evidence to guide their treatment decisions with respect to MBD management, we conducted the Mineral and Bone Disorder Outcomes Study for Japanese CKD Stage 5D Patients (MBD-5D), a 3-year observational study involving prevalent hemodialysis patients with secondary hyperparathyroidism (SHPT). Here, we review the results from the MBD-5D and discuss issues of MBD management in the cinacalcet era. Three years since the introduction of cinacalcet, 40% of hemodialysis patients with SHPT have come to use cinacalcet, enjoying marked improvement in management of circulating MBD markers, such as intact parathyroid hormone (PTH), phosphorus, and calcium. Combination therapy with cinacalcet and a vitamin D receptor activator (VDRA) may allow physicians to choose more suitable prescription patterns based on patient characteristics and therapeutic purposes. We observed an additive association between ‘starting cinacalcet' and ‘increased VDRA dose,' with marked improvement in the control of intact PTH levels. Further, the combination pattern of ‘starting cinacalcet' and ‘decreased VDRA dose' was associated with better achievement of target serum phosphorus and calcium levels. Future studies should examine the effect of different prescription patterns for SHPT treatment on clinical outcomes.

Uremic osteoporosis

Abnormalities in bone turnover, mineralization, and volume represent one of the three components of chronic kidney disease–related mineral and bone disorder (CKD-MBD). The risk of hip fracture is considerably high, while the risk of spinal compression fracture may not be more elevated among CKD patients than in general population. The relationship between bone fracture and bone mineral density in CKD patients is more complex than in those without kidney disease. An increase in the rate of falls has been reported to be a major cause of high hip fracture risk among CKD patients; however, it certainly is not the only underlying mechanism. Abnormal parathyroid function is not likely to be a major cause of hip fracture among CKD patients. In experimental CKD animals, mechanical elasticity properties of long bones showed an inverse correlation with kidney function. The deterioration of bone elasticity showed a significant correlation with bone biochemical changes. Of note, administration of the oral absorbent AST-120 was capable of preventing both changes. These findings suggest that uremic toxins cause a deterioration of bone material properties, and changes in material properties disturb bone elasticity. This disease concept cannot be considered to be a direct consequence of CKD-MBD. We therefore would like to call it ‘uremic osteoporosis'. This entity may be a major cause of increased hip fracture risk among CKD patients.

Calcimimetics and outcomes in CKD

In the past decade, several experimental studies demonstrated an inhibitory effect of calcimimetics on the progression of vascular calcification in animals with chronic kidney disease (CKD), in keeping with the expression of the calcium-sensing receptor (CaR) in vascular tissue. In addition, calcimimetics were also found to prevent the arterial remodeling caused by CKD and to slow the progression of atherosclerosis in uremic rats and mice, respectively. The mode of action of these CaR modulators could be both via a better control of secondary hyperparathyroidism and direct effects on the vessel wall. Two main clinical trials, ADVANCE and EVOLVE, recently evaluated in patients with CKD stage 5D the effects of the calcimimetic cinacalcet on the progression of vascular calcification and hard cardiovascular outcomes, respectively. Both trials missed their respective primary end point by intent-to-treat analysis although by other prespecified analyses, including adjustment for baseline characteristics, there was strong suggestive evidence in favor of reductions in risk, in agreement with numerous experimental studies. Further clinical trials are needed to settle this issue definitively.

Improving outcomes for ESRD patients: shifting the quality paradigm

The availability of life-saving dialysis therapy has been one of the great successes of medicine in the past four decades. Over this time period, despite treatment of hundreds of thousands of patients, the overall quality of life for patients with ESRD has not substantially improved. A narrow focus by clinicians and regulators on basic indicators of care, like dialysis adequacy and anemia, has consumed time and resources but not resulted in significantly improved survival; also, frequent hospitalizations and dissatisfaction with the care experience continue to be seen. A new quality paradigm is needed to help guide clinicians, providers, and regulators to ensure that patients' lives are improved by the technically complex and costly therapy that they are receiving. This paradigm can be envisioned as a quality pyramid: the foundation is the basic indicators (outstanding performance on these indicators is necessary but not sufficient to drive the primary outcomes). Overall, these basics are being well managed currently, but there remains an excessive focus on them, largely because of publically reported data and regulatory requirements. With a strong foundation, it is now time to focus on the more complex intermediate clinical outcomes-fluid management, infection control, diabetes management, medication management, and end-of-life care among others. Successfully addressing these intermediate outcomes will drive improvements in the primary outcomes, better survival, fewer hospitalizations, better patient experience with the treatment, and ultimately, improved quality of life. By articulating this view of quality in the ESRD program (pushing up the quality pyramid), the discussion about quality is reframed, and also, clinicians can better target their facilities in the direction of regulatory oversight and requirements about quality. Clinicians owe it to their patients, as the ESRD program celebrates its 40th anniversary, to rekindle the aspirations of the creators of the program, whose primary goal was to improve the lives of the patients afflicted with this devastating condition.

Guideline bone disease

In the current issue of Blood Purification, Palomares et al. [Blood Purif 2013;36:122-131] bemoan the poor level of compliance in dialysis units in achieving compliance with KDOQI and KDIGO bone and mineral guideline targets. These targets are based almost completely on observational data and rely on an obsolete assay for PTH. The so-called intact PTH assay measures both 1-84 PTH and 7-84 PTH; the latter has been demonstrated to possess biological activity that is antagonistic to that of 1-84 PTH. The assay cannot reliably distinguish high from low bone turnover in the target ranges suggested by the guideline panels. Targeting these ranges leads to an increased incidence of adynamic bone disease, higher calcium and phosphorus, and likely poor patient outcomes.

Evidence-based cardiology in hemodialysis patients

Cardiac events are the major cause of death in hemodialysis patients. Because of the paucity of randomized clinical trials (RCTs) in hemodialysis patients, most cardiovascular therapies in this population are based on observational studies or results extrapolated from studies that excluded hemodialysis patients. However, associations discovered in observational studies do not prove causality, and these studies often report surrogate outcomes rather than clinical end points. Furthermore, interventions that show effectiveness in the general population may have drastically different outcomes and side effect profiles in hemodialysis patients. This review discusses the results of RCTs undertaken recently to evaluate cardiovascular therapies in hemodialysis patients and emphasizes clinically relevant outcomes. Although some interventions have produced similar outcomes in hemodialysis patients and the general population, others have not, suggesting that the management of cardiovascular disease in hemodialysis patients may require strategies that differ from the best practice guidelines applied to general population.

Impact of parathyroidectomy on cardiovascular outcomes and survival in chronic hemodialysis patients with secondary hyperparathyroidism. A retrospective study of 50 cases prior to the calcimimetics era

BACKGROUND

In chronic hemodialysis patients with secondary hyperparathyroidism, pathological modifications of bone and mineral metabolism increase the risk of cardiovascular morbidity and mortality. Parathyroidectomy, reducing the incidence of cardiovascular events, may improve outcomes; however, its effects on long-term survival are still subject of active research.

METHODS

From January 2004 to December 2006, 30 hemodialysis patients, affected by severe and unresponsive secondary hyperparathyroidism, underwent parathyroidectomy - 15 total parathyroidectomy and 15 total parathyroidectomy + subcutaneous autoimplantation. During a 5-year follow-up, patients did not receive a renal transplantation and were evaluated for biochemical modifications and major cardiovascular events - death, cardiovascular accidents, myocardial infarction and peripheral vascular disease. Results were compared with those obtained in a control group of 20 hemodialysis patients, affected by secondary hyperparathyroidism, and refusing surgical treatment, and following medical treatment only.

RESULTS

The groups were comparable in terms of age, gender, dialysis vintage, and comorbidities. Postoperative cardiovascular events were observed in 18/30 - 54% - surgical patients and in 4/20 - 20%- medical patients, with a mortality rate respectively of 23.3% in the surgical group vs. 15% in the control group. Parathyroidectomy was not associated with a reduced risk of cardiovascular morbidity and survival rate was unaffected by surgical treatment.

CONCLUSIONS

In secondary hyperparathyroidism hemodialysis patients affected by severe cardiovascular disease, surgery did not modify cardiovascular morbidity and mortality rates. Therefore, in secondary hyperparathyroidism hemodialysis patients, resistant to medical treatment, only an early indication to calcimimetics, or surgery, in the initial stage of chronic kidney disease - mineral bone disorders, may offer a higher long-term survival. Further studies will be useful to clarify the role of secondary hyperparathyroidism in determining unfavorable cardiovascular outcomes and mortality in hemodialysis population.

Persistent hyperparathyroidism is a major risk factor for fractures in the five years after kidney transplantation

The risk of fractures after kidney transplantation is high. Hyperparathyroidism frequently persists after successful kidney transplantation and contributes to bone loss, but its impact on fracture has not been demonstrated. This longitudinal study was designed to evaluate hyperparathyroidism and its associations with mineral disorders and fractures in the 5 posttransplant years. We retrospectively analyzed 143 consecutive patients who underwent kidney transplantation between August 2004 and April 2006. The biochemical parameters were determined at transplantation and at 3, 12 and 60 months posttransplantation, and fractures were recorded. The median intact parathyroid hormone (PTH) level was 334 ng/L (interquartile 151-642) at the time of transplantation and 123 ng/L (interquartile 75-224) at 3 months. Thirty fractures occurred in 22 patients. The receiver operating characteristic (ROC) curve analysis for PTH at 3 months (area under the ROC curve = 0.711, p = 0.002) showed that a good threshold for predicting fractures was 130 ng/L (sensitivity = 81%, specificity = 57%). In a multivariable analysis, independent risk factors for fracture were PTH >130 ng/L at 3 months (adjusted hazard ratio [AHR] = 7.5, 95% CI 2.18-25.50), and pretransplant osteopenia (AHR = 2.7, 95% CI 1.07-7.26). In summary, this study demonstrates for the first time that persistent hyperparathyroidism is an independent risk factor for fractures after kidney transplantation.

Management of coronary atherosclerosis and acute coronary syndromes in patients with chronic kidney disease

Atherosclerosis of the coronary arteries is common, extensive, and more unstable among patients with chronic renal impairment or chronic kidney disease (CKD). The initial presentation of coronary disease is often acute coronary syndrome (ACS) that tends to be more complicated and has a higher risk of death in this population. Medical treatment of ACS includes antianginal agents, antiplatelet therapy, anticoagulants, and pharmacotherapies that modify the natural history of ventricular remodeling after injury. Revascularization, primarily with percutaneous coronary intervention and stenting, is critical for optimal outcomes in those at moderate and high risk for reinfarction, the development of heart failure, and death in predialysis patients with CKD. The benefit of revascularization in ACS may not extend to those with end-stage renal disease because of competing sources of all-cause mortality. In stable patients with CKD and multivessel coronary artery disease, observational studies have found that bypass surgery is associated with a reduced mortality as compared with percutaneous coronary intervention when patients are followed for several years. This article will review the guidelines-recommended therapeutic armamentarium for the treatment of stable coronary atherosclerosis and ACS and give specific guidance on benefits, hazards, dose adjustments, and caveats concerning patients with baseline CKD.

Cost per responder analysis in patients with secondary hyperparathyroidism on dialysis treated with cinacalcet

BACKGROUND

Growing financial pressure on US dialysis providers requires economic efficiency considerations. The objective of this study was to examine short-term economic efficiencies of a cinacalcet-based treatment approach for secondary hyperparathyroidism.

METHODS

This study retrospectively assessed cost per biochemical response of the OPTIMA trial. OPTIMA was conducted in end-stage renal disease patients to compare biochemical control in patients receiving cinacalcet in addition to vitamin D sterols and phosphate binders vs patients receiving vitamin D sterol and phosphate binders alone. It explored three laboratory measurement response definitions from baseline to week 23: (1) decreases in parathyroid hormone (PTH) ≥30%; (2) PTH ≤ 300 pg/ml; and (3) PTH ≤ 300 pg/mL, calcium <9.5 mg/dL and phosphorus <5.5 mg/dL. Medication use and costs were measured to calculate average costs and incremental cost per responder. Stratification by lower and higher baseline PTH assessed cost per response by disease severity.

RESULTS

There were 38-77% more responders with cinacalcet vs control, depending on response definition. Mean (SD) per patient total medication costs were $5423 ($3698) for cinacalcet and $2633 ($2334) for control, leading to a mean difference of $2790 over 23 weeks. When response was defined as a decrease in PTH ≥ 30% from baseline, the average cost per responder was $11,266 for control vs $7027 for cinacalcet. The incremental cost per incremental responder ranged from $5186-$9168. Across all response measures, cost per responder was lower in patients with lower baseline PTH.

CONCLUSIONS

Representing a more efficient allocation of economic resources over the short-term, cinacalcet-based treatment algorithm led to a lower cost per biochemical response, particularly in patients with lower disease severity, vs vitamin D sterols and phosphate binders alone. These findings should be interpreted alongside the study limitation of converting international trial-based medication utilization into US costs.

Strategies for postmarketing surveillance of drugs and devices in patients with ESRD undergoing dialysis

The lack of evidence on the effectiveness and safety of interventions in chronic dialysis patients has been a subject of continuing criticism. New technologies are often introduced into the market without having specifically studied or even included patients with advanced kidney disease. Therefore, the need to generate valid effectiveness and safety data in this vulnerable subpopulation is of utmost importance. The US Food and Drug Administration has recently placed an increased focus on safety surveillance, and sponsors must now meet this additional postmarketing commitment. In patients with ESRD, the unique data collection environment in the United States allows for creative and efficient study designs to meet the needs of patients, providers, and sponsors. The purpose of this manuscript is to review the methodological and practical aspects of the different options for postmarketing study design in this field, with critical appraisal of their advantages and disadvantages.

Mechanistic analysis for time-dependent effects of cinacalcet on serum calcium, phosphorus, and parathyroid hormone levels in 5/6 nephrectomized rats

This study investigates the time-dependent effects of cinacalcet on serum calcium, phosphorus, and parathyroid hormone (PTH) levels in 5/6 nephrectomized (NX) rats with experimental chronic renal insufficiency. In this study, 5/6 NX male, Sprague-Dawley rats were treated with vehicle or cinacalcet (10 mg/kg, oral, 1× daily). On Day 0 (before treatment), Day 12 and 13 after treatment (to approximate the clinical practice), and also at 0, 1, 4, 8, 16, and 24 hours after the last dosing, blood was collected for analysis. After 12 or 13 days of cinacalcet treatment, modest changes were observed in serum Ca and phosphorus (Pi), while PTH decreased by >45% to Sham levels (152 ± 15 pg/mL). Detailed mapping found that cinacalcet caused a significant time-dependent decrease in serum Ca following dosing, reaching a lowest point at 8 hours (decrease by 20% to 8.43 ± 0.37 mg/dL), and then returning to normal at 24 hours. Cinacalcet also caused a significant increase in serum Pi levels (by 18%). To investigate the potential mechanism of action, a broad approach was taken by testing cinacalcet in a panel of 77 protein-binding assays. Cinacalcet interacted with several channels, transporters, and neurotransmitter receptors, some of which are involved in brain and heart, and may impact Ca homeostasis. Cinacalcet dose-dependently increased brain natriuretic peptide (BNP) mRNA expression by 48% in cardiomyocytes, but had no significant effects on left ventricular hypertrophy and cardiac function. The results suggest that cinacalcet's hypocalcemic effect may be due to its nonspecific interaction with other receptors in brain and heart.

Which vitamin D in CKD-MBD? The time of burning questions

Vitamin D is a common treatment against secondary hyperparathyroidism in renal patients. However, the rationale for the prescription of vitamin D sterols in chronic kidney disease (CKD) is rapidly increasing due to the coexistence of growing expectancies close to unsatisfactory evidences, such as (1) the lack of randomized controlled trials (RCTs) proving the superiority of any vitamin D sterol against placebo on patients centered outcomes, (2) the scanty clinical data on head to head comparisons between the multiple vitamin D sterols currently available, (3) the absence of RCTs confirming the crescent expectations on nutritional vitamin D pleiotropic effects even in CKD patients, (4) the promising effects of vitamin D receptors activators (VDRA) against proteinuria and myocardial hypertrophy in diabetic CKD cohorts, and (5) the conflicting data on the impact on mortality of VDRA versus calcimimetic centered regimens to control CKD-MBD. The present review arguments these issues focusing on the opened questions that nephrologists should consider dealing with the prescription of nutritional vitamin D or VDRA and with the choice of a VDRA versus a calcimimetic based regimen in CKD-MBD patients.

The role of fibroblast growth factor-23 in cardiorenal syndrome

Abnormalities in chronic kidney disease-related bone and mineral metabolism (CKD-MBD) have emerged as novel risk factors in excess cardiovascular mortality in patients with CKD and end-stage renal disease (ESRD). The pathophysiological links between CKD-MBD and adverse cardiovascular events in this patient population are unclear. Hyperphosphatemia through induction of vascular calcifications and decreased active vitamin D production leading to activation of the renin angiotensin system (RAS) along with defects in innate immunity are purported to be the proximate cause of CKD-MBD-associated mortality in CKD. Recently, this view has been challenged by the observation that fibroblast growth factor-23 (FGF23), a newly discovered hormone produced in the bone that regulates phosphate and vitamin D metabolism by the kidney, is a strong predictor of adverse cardiovascular outcomes in patients with CKD and ESRD. Whether these associations between elevated circulating FGF23 levels and cardiovascular outcomes are causative, and if so, the mechanisms mediating the effects of FGF23 on the cardiovascular system are not clear. The principal physiological functions of FGF23 are mediated by activation of FGF receptor/α-klotho coreceptor complexes in target tissues. Elevated FGF23 has been associated with left ventricular hypertrophy (LVH), and it has been suggested that FGF23 may induce myocardial hypertrophy through a direct effect on cardiac myocytes. A direct 'off target' effect of FGF23 on LVH is controversial, however, since α-klotho (which is believed to be indispensable for the physiologic actions of FGF23) is not expressed in the myocardium. Another possibility is that FGF23's effect on the heart is mediated indirectly, via 'on target' regulation of hormonal pathways in the kidney, which include suppression of angiotensin-converting enzyme 2, Cyp27b1and α-klotho, which would be predicted to act on circulating factors known to regulate RAS, 1,25(OH)2D production and ion transport in the myocardium. Understanding of FGF23's pathophysiology and mechanisms of action responsible for its negative effects will be necessary to develop therapeutic strategies to treat CKD-MBD.

Lowering vascular calcification burden in chronic kidney disease: Is it possible?

High prevalence of atherosclerosis and arterial calcification in chronic kidney disease is far beyond the explanation by common cardiovascular risk factors such as aging diabetes, hypertension and dyslipidemia. The magnitude of coronary artery calcification is independently and inversely associated with renal function. In addition to cardiovascular risk factors, other chronic kidney disease-related risks such as phosphate retention, excess of calcium and prolonged dialysis vintage also contribute to the development of vascular calcification. Strategies to lower vascular calcification burden in chronic kidney disease population should include minimizing chronic kidney disease and atherosclerotic risk factors. Current therapies available are non-calcium containing phosphate binders, low dose active vitamin D and calcimimetic agent. The role of bisphosphonates in vascular calcification in chronic kidney disease population remains unclear. Preliminary data on sodium thiosulfate are promising, however, larger studies on efficacy and patient outcomes are necessary. Several large randomized controlled trials have confirmed the lack of benefit of statin in attenuating the progression of vascular calcification.

Parathyroidectomy improves survival in patients with severe hyperparathyroidism: a comparative study

Background and objectives

Secondary hyperparathyroidism (SHPT) in CKD is associated with an increased risk for mortality, but definitive data showing that parathormone control decreases mortality is still lacking. This study aimed to compare the mortality of patients with severe SHPT submitted to parathyroidectomy(PTX) with those who did not have access to surgery.

Methods

This is a retrospective study in a cohort of 251 CKD patients with severe SHPT who were referred to a CKD-MBD Center for PTX from 2005 until 2012.

Results

Most of our patients had indication of PTX, but only 49% of them had access to this surgical procedure. After a mean follow-up of 23 months, 72 patients had died. Non-survivors were older; more often had diabetes, lower serum 25 vitamin D and mostly had not been submitted to surgery. The relative risk of death was lower in the PTX patients (0.428; 95% CI, 0.28 to 0.67; p<0.0001). After adjustments, mortality risk was dependent on age (1.04; 95% CI, 1.01 to 1.07; p = 0.002), 25 vitamin D (0.43; 95% CI, 0.24 to 0.81; p = 0.006) and no access to PTX (4.13; 95% CI, 2.16 to 7.88; p<0.0001). Results remained the same in a second model using the PTX date as the study start date for the PTX group.

Conclusions

Our data confirms the benefit of PTX on mortality in patients with severe SHPT. The high mortality encountered in our population is significant and urges the need to better treat these patients.

Phosphate control in end-stage renal disease: barriers and opportunities

Hyperphosphatemia is a nearly universal complication of end-stage renal disease that is widely recognized as one of the most important and most challenging clinical targets to meet in the care of dialysis patients. Left untreated, it can lead to bone pain, pruritus and worsening secondary hyperparathyroidism. Data from observational studies demonstrate that an elevated serum phosphorus level is an independent risk factor for mortality, and that treatment with phosphate binders is independently associated with improved survival. Experimental studies provide support for the epidemiologic findings: phosphate excess promotes vascular calcification, induces endothelial dysfunction and may contribute to other emerging chronic kidney disease-specific mechanisms of cardiovascular toxicity. On the basis of this evidence, clinical practice guidelines recommend specific targets for serum phosphorus levels in the dialysis population. The purpose of this review is to summarize common challenges in meeting these targets and to identify potential opportunities for improvement.

Chronic kidney disease and cardiovascular risk: epidemiology, mechanisms, and prevention

Since the first description of the association between chronic kidney disease and heart disease, many epidemiological studies have confirmed and extended this finding. As chronic kidney disease progresses, kidney-specific risk factors for cardiovascular events and disease come into play. As a result, the risk for cardiovascular disease is notably increased in individuals with chronic kidney disease. When adjusted for traditional cardiovascular risk factors, impaired kidney function and raised concentrations of albumin in urine increase the risk of cardiovascular disease by two to four times. Yet, cardiovascular disease is frequently underdiagnosed and undertreated in patients with chronic kidney disease. This group of patients should, therefore, be acknowledged as having high cardiovascular risk that needs particular medical attention at an individual level. This view should be incorporated in the development of guidelines and when defining research priorities. Here, we discuss the epidemiology and pathophysiological mechanisms of cardiovascular risk in patients with chronic kidney disease, and discuss methods of prevention.

Gastrointestinal phosphate handling in CKD and its association with cardiovascular disease

Increases in serum concentrations of parathyroid hormone (PTH) and fibroblast growth factor 23 (FGF-23) and ultimately phosphate and decreases in 1,25-dihydroxyvitamin D level are thought to play a central role in the progressive nature of kidney disease and the development of cardiovascular disease in patients with chronic kidney disease. The initial changes in PTH and FGF-23 levels are adaptive to maintain serum phosphate concentration and phosphate load within defined levels by increasing urinary excretion of phosphate. Less well appreciated is the unanticipated finding that absorption of phosphate from the gastrointestinal tract is not downregulated in chronic kidney disease. This maladaptive response maintains higher levels of phosphate absorption, thereby contributing to the phosphate burden. Moreover, in response to a low-phosphate diet, as often is prescribed to such patients, gut phosphate absorption may be enhanced, undermining the potential beneficial effects of this intervention. Given the poor response to limiting phosphate intake and the use of phosphate binders, we suggest that research efforts be oriented toward better understanding of the factors that affect phosphate absorption in the gastrointestinal tract and the development of agents that directly inhibit phosphate transporters in the small intestine and/or their associated binding proteins.

Calcimimetic and calcilytic drugs for treating bone and mineral-related disorders

The calcium-sensing receptor (CaSR) plays a pivotal role in regulating systemic Ca(2+) homeostasis and is a target for drugs designed to treat certain disorders of bone and mineral metabolism. Calcimimetics are agonists or positive allosteric modulators of the CaSR; they inhibit parathyroid hormone (PTH) secretion and stimulate renal Ca(2+) excretion. The first calcimimetic drug is cinacalcet, a positive allosteric modulator of the CaSR that is approved for treating secondary hyperparathyroidism (HPT) in patients on renal replacement therapy and for some forms of primary HPT characterized by clinically significant hypercalcemia. Cinacalcet is also being investigated as a therapy for other hypercalcemic conditions and certain hypophosphatemic disorders. Calcilytics are CaSR inhibitors that stimulate the secretion of PTH and decrease renal excretion of Ca(2+). Although calcilytics have failed thus far as anabolic therapies for osteoporosis, they are currently being evaluated as novel therapies for new indications involving hypocalcemia and/or hypercalciuria.