Vascular Calcification in Patients With Chronic Kidney Disease

Mineral Bone Disorders in Kidney Disease Patients: The Ever-Current Topic

Chronic kidney disease (CKD) is a complex and multifactorial disease, and one of the most prevalent worldwide. Chronic kidney disease–mineral bone disorders (CKD–MBD) with biochemical and hormonal alterations are part of the complications associated with the progression of CKD. Pathophysiology of CKD–MBD focused on abnormalities in serum levels of several biomarkers (such as FGF-23, klotho, phosphate, calcium, vitamin D, and PTH) which are discussed in this review. We therefore examine the prognostic association between CKD–MBD and the increased risk for cardiovascular events, mortality, and CKD progression to end-stage kidney disease (ESKD). Lastly, we present specific treatments acting on CKD to prevent and treat the complications associated with secondary hyperparathyroidism (SHPT): control of hyperphosphatemia (with dietary restriction, intestinal phosphate binders, and adequate dialysis), the use of calcimimetic agents, vitamin D, and analogues, and the use of bisphosphonates or denosumab in patients with osteoporosis.

Prognostic significance of albumin to alkaline phosphatase ratio in critically ill patients with acute kidney injury

OBJECTIVE

No epidemiological evidence has investigated the effect of albumin to alkaline phosphatase ratio (AAPR) on the prognosis among critically ill patients with acute kidney injury (AKI). We aimed to explore the prognostic value of AAPR in these patients.

METHODS

We extracted all clinical data from MIMIC III. ROC curve analysis was used to evaluate the discrimination of AAPR for predicting in-hospital mortality. A generalized additive model was applied to identify a nonlinear association between AAPR and in-hospital mortality. The Cox proportional hazards models were used to determine the association between AAPR and in-hospital and 30-day mortality.

RESULTS

A total of 6894 eligible subjects were enrolled in this study. The relationship between AAPR and in-hospital mortality was nonlinear. Multivariate analysis demonstrated that lower AAPR (AAPR < 0.35) was an independent predictor of in-hospital and 30-day mortality after adjusting for potential confounders (HR 1.74, 95% CI 1.72-2.20, P < 0.001; HR 1.89, 95% CI 1.66-2.14, P < 0.001, respectively).

CONCLUSIONS

AAPR may serve as a potential prognostic biomarker in critically ill patients with AKI and lower AAPR was associated with increased risk of in-hospital and 30-day mortality among these patients.

The Relationship between Serum Sclerostin Levels and Bone Mineral Disorders and Vascular Calcification in Hemodialysis Patients

Background and aim of the study: Sclerostin is produced by osteocytes and has been shown to down-regulate the synthesis of many markers of bone formation by osteogenic cells. The aim of this study to investigate the relationship between serum sclerostin levels and bone mineral disorders and vascular calcification in hemodialysis patients (HD). Methods:This is a cross-sectional study of 70 patients with ESRD on regular HD for at least six months, Theodor Bilharz Research Institute, Giza, Egypt.Twenty-five subjects who matched the ages, genders, and demographics of the study patients were included as a control group.All patients and control groups included in the study underwent a full through history and clinical examination. Serum calcium, phosphorus, alkaline phosphatase and intact PTH (iPTH) levels were measured. Serum sclerostin was measured by an ELISA. Bone Mineral Densitometry Measurements BMD (g/cm2) was determined by dual-energy X-ray absorptiometry (DXA). CT scan was done to detect the presence or absence of vascular calcification and transthoracic echocardiogram to detect the presence or absence of  valvular calcification. Results:The mean seumscleostin levels was a statistically significant high in the HD patients when compared with the control group (156.8 ±121.4 Vs.29.38±0.84,  p =0.0001 ) and statistically significant high mean ALP in the HD patients when compared with the control group (147.2 ± 94.3      Vs.              38.8 ±23.4, p = 0.0001). The mean BMD  was statistically significant low in the HD patients when compared with the controls (0.839±0.086 g/ m2 Vs.1.306  ±0.153 g/ m2, p = 0.0001).The mean seumscleostin levels was statistically significant high in the HD patients with vascular and valvular  calcification  when compared with HD patients without calcification.Using spearman correlation coefficient analysis, there was  statistically significant negative correlations between serum sclerostin levels and iPTH(r=-0.362,   p =0.0021), ALP (r=-0.301, p =0.0114), and BMD (r=-0.469, p =0.0278 ), and there was a statistically significant positive correlation between serum sclerostin levels and phosphate(r=0.5829,  p =0.0001 ).Independent predictors of BMD in HD patients were determined using multi-variate regression analysis. Sclerostin levels, iPTH, ALP, and age  were found to be independent predictors of BMD. Conclusion: High sclerostin levels in patients with ESRD on HD were associated with high risk of vascular and valvularcalcification and were independent predictors of low BMD in such population.

Characteristics of atherosclerosis in femoropopliteal artery and its clinical relevance

Atherosclerosis is a systemic disease with different faces. Despite identical or similar pathogenetic mechanisms, atherosclerotic lesions and their clinical manifestations vary in different parts of the vascular system. Peripheral arterial disease (PAD) represents one of the most frequent clinical manifestations of atherosclerosis with predominant location in the superficial femoral artery (SFA). Morphological characteristics of atherosclerotic plaques in peripheral arteries differ from lesions in the coronary and carotid arteries. Plaques in SFA have more fibrotic components, less lipids and inflammatory cells, which makes them more stable and less prone to rupture. Factors that determine the different structure of plaques in SFA compared to coronary arteries include hemodynamic forces, vasa vasorum and calcification. Low shear stress in SFA in the adductor canal is one of the factors which determines frequent atherosclerotic lesions in this region. Lower lipid content and fewer inflammatory cells explain higher stability of SFA plaques. The specific structure of SFA plaques may require preventive and therapeutic measures, which to some extent differ from prevention of coronary atherosclerosis and may include inhibition of fibrotic proliferation in SFA plaques and calcification. Revascularization of PAD differs from procedures used in coronary arteries and requires specific technical expertise and devices.

Significance of acPWV for Survival of Hemodialysis Patients

BACKGROUND AND OBJECTIVES

Abnormal arterial stiffness (AS) is a major complication in end-stage kidney disease (ESKD) patients treated by dialysis. Our study aimed to determine the significance of AS for survival of prevalent dialysis patients, as well as its association with cardiovascular parameters or vascular calcification promoters/inhibitors or both and AS.

MATERIALS AND METHODS

The study involved 80 adult hemodialysis patients. Besides standard laboratory analyses, we also determined promoters and inhibitors of vascular calcification (bone biomarkers): serum levels of fibroblast growth factor 23 (FGF23), soluble Klotho, intact parathormone (iPTH), 1,25-dihydroxyvitamin D3, osteoprotegerin, sclerostin, AS measured as ankle carotid pulse wave velocity (acPWV), Ankle Brachial Index (ABI), and vascular calcification (VC) score. Patients were monitored for up to 28 months. According to the median acPWV value, we divided patients into a group with acPWV ≤ 8.8 m/s, and a group with acPWV > 8.8 m/s, and the two groups were compared.

RESULTS

Values for bone biomarkers were similar in both groups. Mean arterial blood pressure (MAP), central systolic and diastolic brachial blood pressure, heart rate, and pulse pressure were higher in the group with acPWV > 8.8 m/s than in the group with acPWV ≤ 8.8 m/s. The mortality was higher for patients with acPWV > 8.8 m/s at any given time over 28 months of follow-up. In multivariable analysis, predictors of higher acPWV were age >60.5, higher pulse rate, and higher central systolic or brachial diastolic blood pressure.

CONCLUSIONS

According to our results, we advise the measurement of acPWV preferentially in younger dialysis patients for prognosis, as well as intervention planning before the development of irreversible changes in blood vessels. In addition, measuring central systolic blood pressure seems to be useful for monitoring AS in prevalent hemodialysis patients.

Long-Term Cilostazol Treatment and Predictive Factors on Outcomes of Endovascular Intervention in Patients with Diabetes Mellitus and Critical Limb Ischemia

INTRODUCTION

Despite improvements in endovascular interventions and multidisciplinary approaches, improving clinical outcomes and increasing limb salvage have become increasingly challenging. This prospective study investigated the associations of cilostazol treatment with clinical outcomes and predictive factors in patients with diabetes mellitus (DM) and critical limb ischemia (CLI) after endovascular revascularization of the affected angiosome.

METHODS

In this study, 172 consecutive patients with CLI (Fontaine levels III-IV) received cilostazol treatment after successful endovascular intervention according to the angiosome concept, and their primary patency rates and cardiovascular and amputation events during a 24-month follow-up period were assessed.

RESULT

The 24-month primary patency rate, mortality rate, and amputation rate were better in the patients under long-term cilostazol treatment (P < 0.001, P = 0.029, and P = 0.014). Weighted multivariate Cox analyses with a propensity scoring-based method showed that long-term cilostazol treatment [hazard ratio (HR) 0.2, 95% confidence interval (CI) 0.11-0.36, P < 0.001], direct revascularization (DR) (HR 0.46, 95% CI 0.28-0.74, P = 0.002), and supervised exercise (HR 0.4, 95% CI 0.24-0.66, P < 0.001) were independently associated with primary patency. Patients with lower-extremity amputation (LEA) had a higher risk of coronary artery disease (CAD) and mortality. Cellulitis and neuropathy were independently associated with LEA events (cellulitis: HR 2.89, 95% CI 1.66-5.05, P < 0.001; neuropathy: HR 2.2, 95% CI 1.31-3.7, P = 0.003).

CONCLUSION

Our results showed that patients with DM who received cilostazol treatment for more than 3 months had significantly better outcomes and decreased amputation and mortality rates after DR, and cellulitis and neuropathy were highly associated with the risk of limb loss. A large-scale randomized trial should be conducted in the future to confirm these results.

TRIAL REGISTRATION

Taipei Veterans General Hospital (TVGH) IRB no. 2013-08-020B. Registered 30 August 2013.

Copeptin is independently associated with vascular calcification in chronic kidney disease stage 5

BACKGROUND

Vascular calcification (VC) is an independent predictor of cardiovascular disease (CVD) present in 30-70% of patients with chronic kidney disease (CKD). Copeptin is a sensitive surrogate marker of arginine vasopressin (AVP), which is involved in many pathophysiologic processes in CKD. The aim of the present study was to explore the association of copeptin with VC in CKD stage 5.

METHODS

Copeptin was investigated in conjunction with living donor kidney transplantation in 149 clinically stable CKD stage 5 patients (CKD5), including 53 non-dialyzed (CKD5-ND) and 96 dialysis patients treated by peritoneal dialysis (PD) (n = 43) or hemodialysis (HD) (n = 53). We analyzed the association of copeptin with presence and extent of VC ascertained both histologically in biopsies from the inferior epigastric artery (n = 137) and by coronary artery calcification (CAC) score measured by computed tomography.

RESULTS

Patients with higher copeptin were older, had higher systolic blood pressure, higher prevalence of CVD and their preceding time on chronic dialysis was longer. In Spearman's rank correlations (Rho), copeptin concentrations were significantly associated with CAC score (Rho = 0.27; p = 0.003) and presence of medial VC (Rho = 0.21; p = 0.016). Multivariate logistic regression analysis showed that 1-SD higher age, male gender, diabetes and 1-SD higher copeptin were significantly associated with the presence of moderate-extensive VC.

CONCLUSIONS

High circulating levels of copeptin in CKD5 patients are independently associated with the degree of medial calcification ascertained by histology of arterial biopsies. Thus, plasma copeptin may serve as a marker of the uremic calcification process.

Prognostic significance of pre-end-stage renal disease serum alkaline phosphatase for post-end-stage renal disease mortality in late-stage chronic kidney disease patients transitioning to dialysis

Background

Higher serum alkaline phosphatase (ALP) levels have been associated with excess mortality in patients with non-dialysis-dependent chronic kidney disease (NDD-CKD) and end-stage renal disease (ESRD). However, little is known about the impact of late-stage NDD-CKD ALP levels on outcomes after dialysis initiation.

Methods

Among 17 732 US veterans who transitioned to dialysis between October 2007 and September 2011, we examined the association of serum ALP levels averaged over the last 6 months of the pre-ESRD transition period ('prelude period') with all-cause, cardiovascular and infection-related mortality following dialysis initiation, using Cox (for all-cause mortality) and competing risk (for cause-specific mortality) regressions adjusted for demographics, comorbidities, medications, estimated glomerular filtration rate and serum albumin levels over the 6-month prelude period, and vascular access type at dialysis initiation.

Results

During a median follow-up of 2.0 (interquartile range, 1.1-3.2) years following dialysis initiation, a total of 9196 all-cause deaths occurred. Higher ALP levels were incrementally associated with higher all-cause, cardiovascular and infection-related mortality. Compared with patients in the lowest ALP quartile (<66.0 U/L), those in the highest quartile (≥111.1 U/L) had multivariable-adjusted hazard/subhazard ratios (95% confidence interval) of 1.42 (1.34-1.51), 1.43 (1.09-1.88) and 1.39 (1.09-1.78) for all-cause, cardiovascular and infection-related mortality, respectively. The associations remained consistent in various subgroups and after further adjustment for liver enzymes, serum phosphorus and intact parathyroid hormone levels.

Conclusions

Higher pre-ESRD serum ALP levels are independently associated with higher post-ESRD mortality risk. Further studies are warranted to determine if interventions that lower pre-ESRD ALP levels reduce mortality in incident dialysis patients.

Arterial Stiffness Assessed by Cardio-Ankle Vascular Index

Arterial stiffness is an age-related disorder. In the medial layer of arteries, mechanical fracture due to fatigue failure for the pulsatile wall strain causes medial degeneration vascular remodeling. The alteration of extracellular matrix composition and arterial geometry result in structural arterial stiffness. Calcium deposition and other factors such as advanced glycation end product-mediated collagen cross-linking aggravate the structural arterial stiffness. On the other hand, endothelial dysfunction is a cause of arterial stiffness. The biological molecular mechanisms relating to aging are known to involve the progression of arterial stiffness. Arterial stiffness further applies stress on large arteries and also microcirculation. Therefore, it is closely related to adverse outcomes in cardiovascular and cerebrovascular system. Cardio-ankle vascular index (CAVI) is a promising diagnostic tool for evaluating arterial stiffness. The principle is based on stiffness parameter β, which is an index intended to assess the distensibility of carotid artery. Stiffness parameter β is a two-dimensional technique obtained from changes of arterial diameter by pulse in one section. CAVI applied the stiffness parameter β to all of the arterial segments between heart and ankle using pulse wave velocity. CAVI has been commercially available for a decade and the clinical data of its effectiveness has accumulated. The characteristics of CAVI differ from other physiological tests of arterial stiffness due to the independency from blood pressure at the time of examination. This review describes the pathophysiology of arterial stiffness and CAVI. Molecular mechanisms will also be covered.

Activation of KEAP1/NRF2/P62 signaling alleviates high phosphate-induced calcification of vascular smooth muscle cells by suppressing reactive oxygen species production

Vascular calcification is a complication of diseases and conditions such as chronic kidney disease, diabetes, and aging. Previous studies have demonstrated that high concentrations of inorganic phosphate (Pi) can induce oxidative stress and vascular smooth muscle cell calcification. KEAP1 (Kelch-like ECH-associated protein 1)/NF-E2-related factor 2 (NRF2) signaling has been shown to play important roles in protecting cells from oxidative stress. The current study aims to investigate the possible involvement of the KEAP1/NRF2/P62 -mediated antioxidant pathway in vascular calcification induced by high Pi levels. Exposure of vascular smooth muscle cells (VSMCs) to high Pi concentrations promoted the accumulation of reactive oxygen species (ROS) and the nuclear translocation of NRF2, along with an increase in P62 levels and a decrease in KEAP1 levels. A classic NRF2 activator, tert-butylhydroquinone (tBHQ), significantly decreased ROS levels and calcium deposition in VSMCs by promoting the nuclear translocation of NRF2 and upregulating P62 and KEAP1 expression. In contrast, silencing NRF2 and P62 with siRNAs increased the levels of ROS and calcium deposition in VSMCs. In conclusion, VSMC calcification can be alleviated by the activation of the KEAP1/NRF2/P62 antioxidative pathway, which could have a protective role when it is exogenously activated by tBHQ.

Elevated levels of serum sclerostin are linked to adverse cardiovascular outcomes in peritoneal dialysis patients

PURPOSE

To investigate the correlation between elevated serum sclerostin levels and chronic kidney disease outcomes for patients receiving peritoneal dialysis (PD).

METHODS

We performed a prospective observational study in stable PD patients. Serum sclerostin levels were determined via enzyme immunoassay, and median levels of sclerostin were used to divide patients into high and low sclerostin groups. New-onset cardiovascular events (CVEs) and cardiovascular mortality were evaluated during a 6-year follow-up period.

RESULTS

Ninety-eight patients [mean age 52.5 ± 10.9 years, 49% males, 21.4% diabetic, median dialysis vintage 40.7 (range 17.9-72.2) months] were recruited. Compared with those in the low sclerostin group, patients in the high sclerostin group demonstrated higher levels of total-cholesterol, NT-proBNP, and osteoprotegerin (all P < 0.05). During the 6-year study period, 25 CVEs and 17 cardiovascular deaths occurred in the high sclerostin group, whereas 11 CVEs and four cardiovascular deaths occurred in the low sclerostin group. A Cox regression analysis determined that high sclerostin levels significantly increased the risk for CVEs (HR 2.475, 95% CI 1.116-5.489, P = 0.026) and cardiovascular death (HR 3.484, 95% CI1.134-10.706, P = 0.029), after multiple adjustments were made.

CONCLUSIONS

Our data suggest that high sclerostin levels may predict the onset of CVEs and cardiovascular mortality among PD patients.

Renocardiovascular Biomarkers: from the Perspective of Managing Chronic Kidney Disease and Cardiovascular Disease

Mortality among the patients with chronic kidney disease (CKD) and end-stage renal disease (ESRD) remains high because of the very high incidence of cardiovascular disease (CVD) such as coronary artery disease, cardiac hypertrophy, and heart failure. Identifying CVD in patients with CKD/ESRD remains a significant hurdle and the early diagnosis and therapy for CVD is crucial in these patients. Therefore, it is necessary for the better management to identify and utilize cardiovascular (CV) biomarkers in profiling CVD risk and enabling stratification of early mortality. This review summarizes current evidence about renocardiovascular biomarkers: CV biomarkers in patients with CKD as well as with ESRD, emphasizing on the emerging biomarkers: B-type natriuretic peptide, cardiac troponins, copeptin, the biomarker of renal injury (neutrophil gelatinase-associated lipocalin), and the mineral and bone disorder hormone/marker (fibroblast growth factor-23). Furthermore, it discusses their potential roles especially in ESRD and in future diagnostic and therapeutic strategies for CVD in the context of managing cardiorenal syndrome.

FGF-23 and Osteoprotegerin but not Fetuin-A are associated with death and enhance risk prediction in non-dialysis chronic kidney disease stages 3-5

AIM

Numerous biomarkers have been shown to associate with clinical endpoints in chronic kidney disease (CKD). There is limited evidence whether biomarkers improve risk prediction in relation to clinical outcomes. Our study investigates whether a small suite of key chronic kidney disease-mineral and bone disorder biomarkers could be used to enhance risk assessment in CKD.

METHODS

Fetuin-A, fibroblast growth factor-23 and osteoprotegerin were measured on baseline plasma samples from 463 patients recruited to the Chronic Renal Insufficiency Standards Implementation Study. The biomarkers were analysed in relation to progression to end stage kidney disease, death and major cardiovascular events.

RESULTS

Over a median follow up of 46 months (interquartile range 21-69), fibroblast growth factor-23 was associated with risk for renal replacement therapy (hazard ratio (HR) 1.35, P = 0.05, 95% confidence interval (CI) 1.001-1.820), cardiovascular events (HR 1.74 P < 0.001, 95% CI 1.303-1.305) and death (HR 1.4 P = 0.005, 95% CI 1.109-1.767). Osteoprotegerin was associated with risk for death (HR 1.06, P = 0.03, 95% CI 1.006-1.117). There was no clear association between Fetuin-A and any of the clinical endpoints. The addition of biomarkers to risk models led to marginal improvement in model discrimination and reclassification.

CONCLUSION

Biomarkers are often associated with clinical endpoints, and we observed such associations in our study of patients with advanced CKD. However, the markers analysed in our study were of limited benefit in improving the prediction of these outcomes. Any extra information biomarkers may provide to improve risk prediction in clinical practice needs to be carefully balanced against the potential cost of these tools.

Serum phosphate is an independent predictor of the total aortic calcification volume in non-hemodialysis patients undergoing cardiovascular surgery

BACKGROUND

A high serum phosphate level is a well-known risk factor for vascular calcification (VC) in patients on hemodialysis (HD). However, the association between the serum phosphate level and VC in non-HD patients is unclear. Our aim was to assess the impact of serum phosphate level on aortic calcification (AC) volume in non-HD patients undergoing cardiovascular surgery.

METHODS

A total of 117 patients who underwent thoracoabdominal computed tomography as a preoperative general evaluation before cardiovascular surgery were enrolled. The total AC volume was quantified using the volume-rendering method by extracting the area ≥130HU within the entire aorta. The total AC volume index (AC-VI) was estimated as the total AC volume divided by the body surface area.

RESULTS

In the 117 patients (64.7±13.1 years, 39% women), the median total AC-VI was 1.23mL/m(2). The mean estimated glomerular filtration rate (eGFR), adjusted serum calcium levels, and serum phosphate levels were 63.8±19.9mL/min/1.73m(2), 9.1±0.4mg/dL, and 3.6±0.6mg/dL, respectively. When the patients were classified into four quartiles based on their total AC-VI value, the serum phosphate level showed a positive correlation with a probability of being in the highest AC-VI quartile (R(2)=0.0146, p=0.0383) whereas the adjusted serum calcium level did not show a significant correlation (R(2)=0.0040, p=0.2615). A similar relationship between the serum phosphate level, adjusted serum calcium level, and AC-VI was confirmed when the total AC-VI was divided into the thoracic AC-VI and abdominal AC-VI. Multivariate analysis indicated that the serum phosphate level was an independent positive predictor of higher total AC-VI quartiles (β=0.8013, p=0.0160).

CONCLUSIONS

An increase in serum phosphate level was associated with an increased AC burden in non-HD patients undergoing cardiovascular surgery.

Fibroblast growth factor 23/klotho axis in chronic kidney disease

Fibroblast growth factor-23 (FGF23) is a bone-derived hormone that regulates phosphate and 1,25-hydroxyvitamin D [1,25(OH)2D] metabolism. FGF23 binds to FGF receptor 1 with its coreceptor Klotho and maintains serum phosphate levels within the normal range by increasing renal phosphate excretion. In addition, FGF23 reduces the synthesis and accelerates the degradation of 1,25(OH)2D to reduce intestinal phosphate absorption. Moreover, FGF23 acts at the parathyroid gland to decrease parathyroid hormone synthesis and secretion. In chronic kidney disease (CKD), serum FGF23 levels rise exponentially as renal function declines long before a significant increase in serum phosphate concentration occurs. Although there is room for argument, FGF23 and Klotho are recently reported contributors to vascular calcification. Finally, prospective observational studies have shown that serum FGF23 concentrations predict mortality not only among dialysis patients but among predialysis CKD patients. In addition to being a coreceptor for FGF23, Klotho circulates as an endocrine substance and exerts a multitude of effects. This review describes recent advances in research on the FGF23-Klotho axis in CKD. © 2014 S. Karger AG, Basel.

Circulating bilirubin and defense against kidney disease and cardiovascular mortality: mechanisms contributing to protection in clinical investigations

Unconjugated bilirubin is an endogenous circulating antioxidant, bound to albumin, and therefore is retained in the vascular compartment. Bilirubin has well-documented neurotoxic effects in infants; however, current evidence indicates mildly elevated bilirubin is associated with protection from cardiovascular disease and all-cause mortality in adults. Recent clinical studies show mildly elevated bilirubin is associated with protection from kidney damage and dysfunction, in addition to cardiovascular events and all-cause mortality in patients undergoing hemodialysis. This is the first review to examine the clinical evidence and summarize the potential mechanisms of action that link bilirubin to protection from kidney damage, subsequent kidney failure, and dialysis-related mortality. With this understanding, it is hoped that new therapies will be developed to prevent renal dysfunction and mortality from cardiovascular disease in at-risk individuals.

Association of serum phosphorus variability with coronary artery calcification among hemodialysis patients

Coronary artery calcification (CAC) is associated with increased mortality in patients on maintenance hemodialysis (MHD), but the pathogenesis of this condition is not well understood. We evaluated the relationship of CAC score (CACs) and variability in serum phosphorus in MHD patients. Seventy-seven adults on MHD at Huashan Hospital (Shanghai) were enrolled in July, 2010. CAC of all the patients were measured by computed tomography and CACs was calculated by the Agatston method at the entry of enrollment. Patients were divided into three categories according to their CACs (0∼10, 11∼400, and >400). Blood chemistry was recorded every 3 months from January 2008 to July 2010. Phosphorus variation was defined by the standard deviation (SD) or coefficient of variation (CV) and it was calculated from the past records. The ordinal multivariate logistic regression analysis was used to analyze the predictors of CAC. The mean patient age (± SD) was 61.7 years (±11.3) and 51% of patients were men. The mean CACs was 609.6 (±1062.9), the median CACs was 168.5, and 78% of patients had CACs more than 0. Multivariate analysis indicated that female gender (OR = 0.20, 95% CI = 0.07–0.55), age (OR = 2.31, 95% CI = 1.32–4.04), serum fibroblast growth factor 23 (OR = 2.25, 95% CI = 1.31–3.85), SD-phosphorus calculated from the most recent 6 measurements (OR = 2.12; 95% CI = 1.23–3.63), and CV-phosphorus calculated from the most recent 6 measurements (OR = 1.90, 95% CI = 1.16–3.11) were significantly and independently associated with CACs. These associations persisted for phosphorus variation calculated from past 7, 8, 9, 10, and 11 follow-up values. Variability of serum phosphorus may contribute significantly to CAC and keeping serum phosphorus stable may decrease coronary calcification and associated morbidity and mortality in MHD patients.

Peripheral arterial calcification: prevalence, mechanism, detection, and clinical implications

Vascular calcification (VC), particularly medial (Mönckeberg's medial sclerosis) arterial calcification, is common in patients with diabetes mellitus and chronic kidney disease and is associated with increased cardiovascular morbidity and mortality. Although, the underlying pathophysiological mechanisms and genetic pathways of VC are not fully known, hypocalcemia, hyperphosphatemia, and the suppression of parathyroid hormone activity are central to the development of vessel mineralization and, consequently, bone demineralization. In addition to preventive measures, such as the modification of atherosclerotic cardiovascular risk factors, current treatment strategies include the use of calcium-free phosphate binders, vitamin D analogs, and calcium mimetics that have shown promising results, albeit in small patient cohorts. The impact of intimal and medial VC on the safety and effectiveness of endovascular devices to treat symptomatic peripheral arterial disease (PAD) remains poorly defined. The absence of a generally accepted, validated vascular calcium grading scale hampers clinical progress in assessing the safety and utility of various endovascular devices (e.g., atherectomy) in treating calcified vessels. Accordingly, we propose the peripheral arterial calcium scoring system (PACSS) and a method for its clinical validation. A better understanding of the pathogenesis of vascular calcification and the development of optimal medical and endovascular treatment strategies are crucial as the population ages and presents with more chronic comorbidities.

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.

Prognostic importance of serum alkaline phosphatase in CKD stages 3-4 in a clinical population

BACKGROUND

Elevated total serum alkaline phosphatase (ALP) levels have been associated with mortality in the general population and in dialysis patients.

STUDY DESIGN

Retrospective cohort study.

SETTING & PARTICIPANTS

28,678 patients with chronic kidney disease (CKD) stages 3 and 4 (estimated glomerular filtration rate, 15-59 mL/min/1.73 m(2)) were identified using the Cleveland Clinic CKD Registry. CKD was defined as 2 estimated glomerular filtration rate values <60 mL/min/1.73 m(2) drawn more than 90 days apart using the CKD-EPI (CKD Epidemiology Collaboration) creatinine equation.

PREDICTOR

ALP levels measured using the calorimetric assay were examined as quartiles (quartile [Q]1, <66 U/L; Q2, 66-81 U/L; Q3, 82-101 U/L; and Q4, ≥102 U/L) and as a continuous measure.

OUTCOMES & MEASUREMENTS

All-cause mortality and end-stage renal disease (ESRD) were ascertained using the Social Security Death Index and US Renal Data System.

RESULTS

After a median follow-up of 2.2 years, 588 patients progressed to ESRD and 4,755 died. There was a graded increase in risk of mortality with higher ALP quartiles (Q2, Q3, and Q4) compared to the reference quartile (Q1) after adjusting for demographics, comorbid conditions, use of relevant medications, and liver function test results. The highest ALP quartile was associated with an HR for ESRD of 1.38 (95% CI, 1.09-1.76). Each 1-SD (42.7 U/L) higher ALP level was associated with 15% (95% CI, 1.09-1.22) and 16% (95% CI, 1.14-1.18) increased risk of ESRD and mortality, respectively.

LIMITATIONS

Single-center observational study; lack of complete data, including parathyroid hormone level, for all study participants, and attrition bias.

CONCLUSIONS

Higher serum ALP levels in patients with CKD stages 3-4 were associated independently with all-cause mortality and ESRD.

Angiotensin-(1-7) inhibits vascular calcification in rats

Angiotensin-(1-7) [Ang-(1-7)] is a new bioactive heptapeptide in the renin-angiotensin-aldosterone system (RAAS) with potent protective effects in cardiovascular diseases, opposing many actions of angiotensin II (Ang II) mediated by Ang II type 1 (AT1) receptor. It is produced mainly by the activity of angiotensin-converting enzyme 2 (ACE2) and acts through the Mas receptor. However, the role of Ang-(1-7) in vascular calcification (VC) is still unclear. In this study, we investigated the protective effects of Ang-(1-7) on VC in an in vivo rat VC model induced by vitamin D3 plus nicotine. The levels of ACE2 and the Mas receptor, as well as ACE, AT1 receptor, Ang II type 2 receptor and angiotensinogen, were significantly increased in calcified aortas, and Ang-(1-7) reversed the increased levels. Ang-(1-7) restored the reduced expression of lineage markers, including smooth muscle (SM) α-actin, SM22α, calponin and smoothelin, in vascular smooth muscle cells (VSMCs) and retarded the osteogenic transition of VSMCs by decreasing the expression of bone-associated proteins. It reduced alkaline phosphatase activity and calcium deposition in VC and alleviated the hemodynamic disorders of rats with VC. We provide the first in vivo evidence that Ang-(1-7) can inhibit the development of VC by inhibiting the osteogenic transition of VSMCs, at least in part by decreasing levels of the ACE/Ang II/AT1 axis. The increased expression of ACE2 and the Mas receptor in calcified aortas suggests the involvement of the ACE2/Ang-(1-7)/Mas axis during VC. Ang-(1-7) might be an efficient endogenous vasoprotective factor for VC.

Testicular angina during hemodialysis: an unusual complication of ultrafiltration

During hemodialysis, the development of hypotension or symptoms suggestive of ischemia is used as a surrogate marker for the establishment of dry weight. These symptoms manifest commonly as muscle cramps, chest pain or abdominal pain. Hemodialysis patients are also prone to vascular calcification which may be medial or intimal. We report the case of a 68-year-old male who developed testicular pain while attempting to establish dry weight. Computerized tomography scan of his abdomen showed extensive vascular calcification. The end result in this case was bilateral orchiectomy. Histopathology revealed hyperplastic arteriolosclerosis with intimal calcification contributing to ischemia.