Significant association between the progression of coronary artery calcification and dyslipidemia in patients on chronic hemodialysis

The Contribution of Extracellular Vesicles From Senescent Endothelial and Vascular Smooth Muscle Cells to Vascular Calcification

Vascular calcification is an irreversible pathological process associated with a loss of vascular wall function. This process occurs as a result of aging and age-related diseases, such as cardiovascular and chronic kidney diseases, and leads to comorbidities. During these age-related diseases, the endothelium accumulates senescent cells, which stimulate calcification in vascular smooth muscle cells. Currently, vascular calcification is a silent pathology, and there are no early diagnostic tools. Therefore, by the time vascular calcification is diagnosed, it is usually untreatable. Some mediators, such as oxidative stress, inflammation, and extracellular vesicles, are inducers and promoters of vascular calcification. They play a crucial role during vascular generation and the progression of vascular calcification. Extracellular vesicles, mainly derived from injured endothelial cells that have acquired a senescent phenotype, contribute to calcification in a manner mostly dependent on two factors: (1) the number of extracellular vesicles released, and (2) their cargo. In this review, we present state-of-the-art knowledge on the composition and functions of extracellular vesicles involved in the generation and progression of vascular calcification.

An Overview of the Pathophysiology of Vascular Calcification in Chronic Kidney Disease

Abnormalities of calcium–phosphate balance, with subsequent bone metabolism disorders, are among the key and earliest features of chronic kidney disease (CKD). Recently, another consequence of these abnormalities was brought to light—namely, vascular calcification. Most studies performed in patients on dialysis suggest that their vascular calcification is more advanced than that seen in the general population. Furthermore, the progression of vessel wall mineralization is much more dynamic in patients with CKD.

Apart from the commonly assessed factors that promote vascular calcification, such as age, duration of dialysis, or poor control of calcium–phosphate status, several other factors have recently been identified. In the spectrum of substances involved in the regulation of the process of soft-tissue calcification, the most extensively studied in the nephrology literature are bone morphogenetic protein 7, osteoprotegerin, matrix Gla protein, fetuin-A, and the phosphatonins. Better understanding of the mechanisms underlying excess vascular mineralization have led to the development of promising new therapies.

The Progression and Impact of Vascular Calcification in Peritoneal Dialysis Patients

Background

Progression of coronary artery calcification (CAC) has been described in hemodialysis patients, and severe CAC has been associated with the occurrence of cardiovascular events in this population. Little information is available regarding peritoneal patients.

Aim

To prospectively evaluate peritoneal dialysis patients in order to identify the variables associated with the rate of CAC progression, as well as to determine the impact that baseline CAC has on clinical outcomes over a 1-year follow-up period.

Methods

Using multislice coronary tomography, calcium scores were estimated at baseline and after 12 months in 49 peritoneal dialysis patients. Patients with and without CAC progression were compared with respect to clinical characteristics and biochemical variables, including lipid profile, parameters of mineral metabolism, and markers of inflammation. Cardiovascular events, hospitalizations, and all-cause mortality were recorded.

Results

At baseline, 29 patients (59%) presented CAC and a median calcium score of 234.7 (range 10.3 – 2351) Agatston units. Progression of CAC was observed in 13 patients (43%) who, in comparison with those presenting no CAC progression, were older, presented higher baseline calcium scores, and had higher mean glucose levels, lower mean high density lipoprotein cholesterol levels, and more months using low calcium peritoneal solution. We also observed a trend toward more often presenting with a history of hypertension, exhibiting more hyperphosphatemic and hyperglycemic events, and having lower albumin levels. In multiple logistic regression, only baseline calcium score was independently associated with progression of CAC. A shorter cardiovascular event-free time and a trend toward lower survival rates were observed in the group with CAC. Hospitalization event-free time did not differ between the groups.

Conclusion

Determining CAC provides important prognostic data in peritoneal dialysis patients. Baseline calcium score and disturbances in glucose, mineral, and lipid metabolism were indicative of higher risk of CAC progression in this population.

Diabetes Mellitus Modifies the Associations of Serum Magnesium Concentration With Arterial Calcification and Stiffness in Incident Hemodialysis Patients

Introduction

Magnesium (Mg) may protect against arterial calcification. We tested the hypotheses that a higher serum Mg concentration is associated with less arterial calcification and stiffness in patients on hemodialysis (HD) and that these associations are modified by diabetes mellitus.

Methods

We performed cross-sectional analyses of 367 incident HD patients from the Predictors of Arrhythmic and Cardiovascular Risk in End Stage Renal Disease (PACE) cohort. Measures of arterial calcification and stiffness included coronary arterial calcification (CAC) and thoracic aortic calcification (TAC) scores, ankle brachial index (ABI; high ABI: >1.4 or incompressible vessels), pulse wave velocity (PWV), and pulse pressure.

Results

Mean Mg was 1.8 ± 0.2 mEq/l and 58% had diabetes. Among nondiabetic individuals, per 0.1 mEq/l higher Mg, non-zero CAC score was lower (% difference: −15.4%; 95% confidence interval [CI]: −28% to −0.55%; P = 0.03), the odds of having TAC score >0 and the odds of having high ABI were lower (odds ratio [OR]: 0.66; 95% CI 0.47–0.93; P = 0.02, and 0.23; 95% CI: 0.06–0.83, P = 0.03, respectively) while adjusting for demographics, comorbidities, markers of mineral metabolism, and dialysis clearance. Among diabetic individuals, per 0.1 mEq/l higher Mg, the odds of having TAC score >0 was higher (OR: 1.57; 95% CI: 1.09–2.26; P = 0.02). Mg was not associated with CAC or high ABI among diabetic individuals. Mg was not associated with PWV or pulse pressure regardless of diabetes status.

Conclusion

Diabetes modified the associations of serum Mg with arterial calcification and stiffness in incident HD patients. Higher Mg was associated with less arterial calcification and less peripheral arterial stiffness among nondiabetic individuals, but Mg was only associated with TAC among diabetic individuals with higher Mg being associated with higher likelihood of having TAC score >0.

Supplementary nutrients for prevention of vascular calcification in patients with chronic kidney disease

Vascular calcification (VC) and malnutrition associated with cardiovascular disease are common in patients with chronic kidney disease (CKD) treated with dialysis. VC, which reflects vascular aging, and malnutrition are also encountered in the non-CKD elderly population. This similarity of clinical findings suggests that the progression of CKD is related to aging and the existence of a causal relationship between VC and malnutrition. To retard renal progression, a low- or very-low-protein diet is usually recommended for CKD patients. Dietary education may induce malnutrition and deficiency of important nutrients, such as vitamins K and D. Menaquinone-7, a type of vitamin K2, is under investigation for inhibiting VC in elderly patients without CKD, as well as for prevention of VC in patients with CKD. Nutritional vitamin D, such as cholecalciferol, may be considered to decrease the required dose of active vitamin D, which increases the risk of VC due to increased calcium and phosphate loads. Omega-3 fatty acids are important nutrients and their ability to inhibit VC needs to be evaluated in clinical trials. This review focuses on the ability of supplementary nutrients to prevent VC in patients with CKD, in whom dietary restriction is essential.

Magnesium: A Magic Bullet for Cardiovascular Disease in Chronic Kidney Disease?

Magnesium is essential for many physiological functions in the human body. Its homeostasis involves dietary intake, absorption, uptake and release from bone, swifts between the intra- and extracellular compartment, and renal excretion. Renal excretion is mainly responsible for regulation of magnesium balance. In chronic kidney disease (CKD), for a long time the general policy has been limiting magnesium intake. However, this may not be appropriate for many patients. The reference ranges for magnesium are not necessarily optimal concentrations, and risks for insufficient magnesium intake exist in patients with CKD. In recent years, many observational studies have shown that higher (in the high range of “normal” or slightly above) magnesium concentrations are associated with better survival in CKD cohorts. This review gives an overview of epidemiological associations between magnesium and overall and cardiovascular survival in patients with CKD. In addition, potential mechanisms explaining the protective role of magnesium in clinical cardiovascular outcomes are described by reviewing evidence from in vitro studies, animal studies, and human intervention studies with non-clinical endpoints. This includes the role of magnesium in cardiac arrhythmia, heart failure, arterial calcification, and endothelial dysfunction. Possible future implications will be addressed, which will need prospective clinical trials with relevant clinical endpoints before these can be adopted in clinical practice.

Vitamin D in Vascular Calcification: A Double-Edged Sword?

Vascular calcification (VC) as a manifestation of perturbed mineral balance, is associated with aging, diabetes and kidney dysfunction, as well as poorer patient outcomes. Due to the current limited understanding of the pathophysiology of vascular calcification, the development of effective preventative and therapeutic strategies remains a significant clinical challenge. Recent evidence suggests that traditional risk factors for cardiovascular disease, such as left ventricular hypertrophy and dyslipidaemia, fail to account for clinical observations of vascular calcification. Therefore, more complex underlying processes involving physiochemical changes to mineral balance, vascular remodelling and perturbed hormonal responses such as parathyroid hormone (PTH) and fibroblast growth factor 23 (FGF-23) are likely to contribute to VC. In particular, VC resulting from modifications to calcium, phosphate and vitamin D homeostasis has been recently elucidated. Notably, deregulation of vitamin D metabolism, dietary calcium intake and renal mineral handling are associated with imbalances in systemic calcium and phosphate levels and endothelial cell dysfunction, which can modulate both bone and soft tissue calcification. This review addresses the current understanding of VC pathophysiology, with a focus on the pathogenic role of vitamin D that has provided new insights into the mechanisms of VC.

Impact of Indoxyl Sulfate on Coronary Plaques in Patients on Hemodialysis

Serum indoxyl sulfate (IS; a uremic toxin) levels, which are significantly higher in patients with chronic kidney disease, including those undergoing hemodialysis, than in the robust, are associated with both cardiovascular disease (CVD) and CVD-related mortality. Furthermore, coronary artery calcium (CAC) is an independent predictor of cardiovascular events in patients undergoing hemodialysis. This study aimed to interpret the association between serum IS levels and coronary plaque burden (CPB) or CAC.A total of 30 consecutive patients on hemodialysis, who underwent 320-row coronary multidetector computed tomography (MDCT) angiography for suspected coronary artery disease, were enrolled in this prospective study. Coronary artery percent atheroma volume (a CPB marker) and percent calcium volume (a CAC marker) assessed using MDCT were evaluated. Furthermore, various oxidative and inflammatory markers typified by serum IS levels at a dialysis-free day were measured. Using these data, we investigated correlation between the inflammatory marker IS and CPB or CAC.Multivariable analysis indicated that serum IS levels were positively correlated with CAC [partial regression coefficient, 2.89; 95% confidence interval (CI), 0.35-5.43; P = 0.03] but not with CPB, even after adjustment for cofounders. Composite cardiovascular events, namely, as all-cause death, non-fatal myocardial infarction, disabling stroke, and hospital admission for other cardiovascular events, were reported to be 50% in all patients (95% CI, 32.1-67.9).In patients undergoing hemodialysis, serum IS levels were significantly associated with CAC but not with CPB.

Impact of Renal Functional/Morphological Dynamics on the Calcification of Coronary and Abdominal Arteries in Patients with Chronic Kidney Disease

Aim: Fast-progressing vascular calcification (VC) is accompanied by renal atrophy and functional deterioration along with atherosclerosis in patients with chronic kidney disease (CKD). However, the relationship between VC progression and renal functional and/or morphological changes remains unclear.

Methods: We included 70 asymptomatic patients with CKD without hemodialysis in our study. To identify temporal variations, the coronary artery calcification score (CACS), abdominal aortic calcification index (ACI), and renal parenchymal volume index (RPVI) were determined via spiral computed tomography scans taken during the study. We investigated significant factors related to annualized variations of CACS (ΔCACS/y) and ACI (ΔACI/y).

Results: During the follow-up period (4.6 years), median values of CACS [in Agatston units (AU)] and ACI increased from 40.2 to 113.3 AU (p = 0.053) and from 13.2 to 21.7% (p = 0.036), respectively. Multivariate analysis revealed that CACS at baseline (p < 0.001) and diabetes mellitus (DM) status (p = 0.037) for ΔCACS/y and ACI at baseline (p = 0.017) and hypertension (HT) status (p = 0.046) for ΔACI/y were significant independent predictors. Furthermore, annualized RPVI variation was significantly related to both ΔCACS/y and ΔACI/y (R = −0.565, p < 0.001, and R = −0.289, p = 0.015, respectively). On the other hand, independent contributions of the estimated glomerular filtration rate (eGFR) and annualized eGFR variation to VC progression were not confirmed.

Conclusion: The degree of VC at baseline, DM, HT, and changes in renal volume, but not eGFR, had a strong impact on VC progression in patients with CKD.

Low versus high dialysate calcium concentration in alternate night nocturnal hemodialysis: A randomized controlled trial

INTRODUCTION

Higher calcium dialysate is recommended for quotidian nocturnal hemodialysis (NHD) (≥6 nights/week) to maintain bone health. It is unclear what the optimal calcium dialysate concentration should be for alternate night NHD. We aimed to determine the effect of low calcium (LC) versus high calcium (HC) dialysate on cardiovascular and bone parameters in this population.

METHODS

A randomized controlled trial where participants were randomized to LC (1.3 mmol/L, n = 24) or HC dialysate (1.6 or 1.75 mmol/L, n = 26). Primary outcome was change in mineral metabolism markers. Secondary outcomes included change in vascular calcification (VC) scores [CT abdominal aorta (AA) and superficial femoral arteries (SFA)), pulse wave velocity (PWV), bone mineral density (BMD) and left ventricular mass index (LVMI) over 12 months.

FINDINGS

In the LC group, pre-dialysis ionised calcium decreased -0.12 mmol/L (-0.18-0.06, P = 0.0001) and PTH increased 16 pmol/L (3.5-28.5, p = 0.01) from baseline to 12 months with no significant change in the HC group. In both groups, there was no progression of VC in AA or SFA and no change in PWV, LVMI or BMD. At 12 months, calcimimetics were prescribed in a higher percentage in the LC vs. HC groups (45.5% vs. 10.5%) with a lower proportion of the HC group being prescribed calcitriol (31.5% vs. 72%).

DISCUSSION

Although dialysate calcium prescription influenced biochemical parameters it was not associated with difference in progression of VC between HC and LC groups. An important finding was the potential impact of alternate night NHD in attenuating progression of VC and inducing stabilisation of LVMI and PWV.

Different impact of hemodialysis vintage on cause-specific mortality in long-term hemodialysis patients

BACKGROUND

Although dialysis vintage is associated with increased mortality risk in patients receiving hemodialysis (HD), the association of dialysis vintage with cause-specific mortality is unclear.

METHODS

We conducted a nationwide registry-based retrospective cohort study of 216 246 patients receiving maintenance HD for > 1 year at the end of 2009. The associations of dialysis vintage categories (1 -< 2, 2 -< 5, 5 -< 10, 10 -< 15, 15 -< 20, 20 -< 25, 25 -< 30 and ≥ 30 years) with 1-year all-cause and cause-specific mortality, including cardiovascular diseases (CVDs) and infection-related mortality, were examined using logistic regression models.

RESULTS

During the 1-year study period, 18 614 deaths occurred from all causes, including 7263 and 3504 deaths from CVD and infection-related causes. From multivariate analysis, the dialysis vintage was incrementally associated with a higher risk for all-cause mortality, with worse outcome observed in the ≥ 30 years category {odds ratio [OR] = 2.43 (95% confidence interval (CI) 2.13-2.77}. A similar association was apparent between the dialysis vintage and infection-related mortality, with a higher risk than that of all-cause mortality in each vintage category [≥ 30 years, OR = 3.55 (95% CI 2.72-4.66)], while the dialysis vintage was associated with only a modest increase in risk of CVD mortality [≥ 30 years, OR = 1.64 (95% CI 1.30-2.08)].

CONCLUSIONS

Dialysis vintage has a different impact on cause-specific mortality, with a higher risk for infection-related mortality than CVD mortality. This impact is most pronounced in long-term HD survivors, to whom much attention should be devoted to prevent infectious complications.

Hyperphosphatemia as an independent risk factor for coronary artery calcification progression in peritoneal dialysis patients

Background

Coronary artery calcification (CAC) is associated with cardiovascular mortality in end-stage renal disease (ESRD) patients. The present study aimed to identify modifiable risk factors for CAC progression in peritoneal dialysis (PD) patients.

Methods

Adult patients who received regular PD for more than 6 months and underwent a series of coronary artery calcification score (CaCS) measurements by multislice spiral computed tomography (MSCT) with an interval of ≥ 6 months were included in this observational cohort study. The demographic characteristics and clinical data, including laboratory data and adequacy of PD, were collected. Curve estimation was used to fit the straight line and obtain the slope. Binary logistic regression was performed to identify the independent risk factors for CAC progression in the PD patients, and multivariate linear regression was conducted to identify factors associated with hyperphosphatemia.

Results

A total of 207 adult patients on PD (116 men, 56.0 %) with a mean age of 59.8 ± 15.9 years were recruited to this study, and 157 of them (75.8 %) received three or more CaCS assessments. The patients were divided into a slow group (n = 137) and a rapid group (n = 70) according to the linear regression slope or the average speed of development. The follow-up time was 33.0 ± 18.8 months. Multivariate logistic regression revealed that age and serum phosphate level were independent risk factors for CAC progression after adjustments. Multivariate linear regression revealed that hyperphosphatemia was associated with elevations in the transferrin and serum albumin levels and normalized protein catabolic rate (nPCR) and reductions in the hemoglobin level, residual Ccr, and PD Ccr.

Conclusions

Hyperphosphatemia is an independent risk factor for CAC progression, and the serum phosphate level may be associated with protein intake and PD adequacy. These results provide important information for the clinical management of ESRD patients.

High Parathyroid Hormone Level and Osteoporosis Predict Progression of Coronary Artery Calcification in Patients on Dialysis

Coronary artery calcifications (CACs) are observed in most patients with CKD on dialysis (CKD-5D). CACs frequently progress and are associated with increased risk for cardiovascular events, the major cause of death in these patients. A link between bone and vascular calcification has been shown. This prospective study was designed to identify noninvasive tests for predicting CAC progression, including measurements of bone mineral density (BMD) and novel bone markers in adult patients with CKD-5D. At baseline and after 1 year, patients underwent routine blood tests and measurement of CAC, BMD, and novel serum bone markers. A total of 213 patients received baseline measurements, of whom about 80% had measurable CAC and almost 50% had CAC Agatston scores>400, conferring high risk for cardiovascular events. Independent positive predictors of baseline CAC included coronary artery disease, diabetes, dialysis vintage, fibroblast growth factor-23 concentration, and age, whereas BMD of the spine measured by quantitative computed tomography was an inverse predictor. Hypertension, HDL level, and smoking were not baseline predictors in these patients. Three quarters of 122 patients completing the study had CAC increases at 1 year. Independent risk factors for CAC progression were age, baseline total or whole parathyroid hormone level greater than nine times the normal value, and osteoporosis by t scores. Our results confirm a role for bone in CKD-associated CAC prevalence and progression.

Osteoprotegerin, inflammation and dyslipidemia are associated with abdominal aortic calcification in non-diabetic patients on peritoneal dialysis

BACKGROUND AND AIMS

Abdominal aortic calcification (AC) has been reported to be associated with cardiovascular disease (CVD) in hemodialysis patients but is rarely discussed in peritoneal dialysis (PD) patients. We examined the independent predictors and predictive power for survival of AC in prevalent PD patients.

METHODS AND RESULTS

AC was detected by computed tomography (CT) and represented as the percentage of the total aortic cross-section area affected by AC (%AC). The predictors of %AC ≥ 15 were examined by multiple logistic regression analysis. Cox proportional hazard analysis was used to determine the hazard ratios associated with high %AC. A total of 183 PD patients were recruited to receive CT scans and divided into group 1 (%AC < 15, n = 97), group 2 (%AC ≥ 15, n = 41), and group 3 (diabetic patients, n = 45). Group 1 patients had lower osteoprotegerin (OPG) levels than group 2 patients (798 ± 378 vs. 1308 ± 1350 pg/mL, p < 0.05). The independent predictors for %AC ≥ 15 included the atherogenic index, OPG, and C-reactive protein (CRP). The age-adjusted hazard ratios associated with %AC ≥ 15 were 3.46 (p = 0.043) for mortality and 1.90 (p = 0.007) for hospitalization.

CONCLUSIONS

%AC can predict mortality and morbidity in non-diabetic PD patients, and 15% is a good cut-off value for such predictions. There are complex associations among mineral metabolism, inflammation, and dyslipidemia in the pathogenesis of AC.

Oxidised LDL/LDL-cholesterol ratio and coronary artery calcification in haemodialysis patients

BACKGROUND AND AIMS

Serum malondialdehyde-modified low-density lipoprotein (MDA-LDL) and MDA-LDL/LDL-cholesterol (LDL-c) ratio are risk factors for arteriosclerosis and cardiovascular disease (CVD). However, no information is available on these parameters or their associations with coronary artery calcification (CAC) in haemodialysis (HD) patients.

METHODS AND RESULTS

Fifty-seven HD patients and 26 control subjects were included in this cross-sectional study. Serum MDA-LDL concentrations and MDA-LDL/LDL-c ratios were examined. HD patients had significantly higher MDA-LDL/LDL-c ratios than the controls (105.1 ± 27.5 vs. 81.4 ± 18.9 mU/mg, P < 0.001); however, there was no significant difference in serum MDA-LDL levels between the 2 groups. CAC scores were examined only in HD patients and their possible associations with the clinical/laboratory data were analysed. Analysis of HD patients showed that MDA-LDL/LDL-c ratio has an association with presence of CVD, CAC score, HD duration, MDA-LDL, or haemoglobin A1C. In addition, the CAC score was positively correlated with serum MDA-LDL level (P = 0.048) and MDA-LDL/LDL-c ratio (P = 0.006). Furthermore, multivariate logistic regression analysis showed that MDA-LDL/LDL-c ratio (β = 0.04, P = 0.003) and HD duration (β = 0.16, P = 0.007) were independently associated with CAC score.

CONCLUSION

The MDA-LDL/LDL-c ratio of HD patients was significantly higher than that of non-HD subjects and was independently associated with the CAC score. Therefore, this ratio could be an important risk factor for CAC in HD patients.

Vascular calcification on plain radiographs is associated with carotid intima media thickness, malnutrition and cardiovascular events in dialysis patients: a prospective observational study

Background

Vascular calcification (VC) and carotid intima media thickness (CIMT) are strongly associated with cardiovascular (CV) disease. We hypothesized that significant VC on plain radiographs is associated with CIMT and CV events in dialysis patients. In addition, we evaluated risk factors for VC progression on plain radiographs in dialysis patients.

Methods

In this 2-year observational, prospective study, 67 dialysis patients were included. We checked plain radiographs at baseline and after 2 years. Laboratory tests and malnutrition score were obtained at baseline, after 12 months, and after 24 months.

Results

The mean age of patients was 56.3 ± 10.3 years and duration of dialysis was 41.3 ± 34.5 months. The prevalence of significant VC was 61.2% and the prevalence of carotid artery atheromatous plaques was 55.6%. Mean CIMT, malnutrition scores, CRP level and prevalence of carotid atheromatous plaques were significantly higher in patients with significant VC. Serum albumin and total iron binding capacity were significantly lower in patients with significant VC compared to patients without significant VC. During a mean observational period of 22 months, patients without significant VC showed lower CV events by the Kaplan-Meyer method (p = 0.010). Progression of VC was found in 35.7% among 56 patients followed up. Hemoglobin after 24 months was an independent factor for progression of VC (Exp(B) = 0.344, 95% Confidence Interval = 0.13 – 0.96, p = 0.034).

Conclusions

Significant VC on plain radiograph was associated with CIMT, malnutrition, inflammation, and CV events in dialysis patients. Conditions which increase hemoglobin level may retard progression of VC in dialysis patients.

Coronary artery calcification score is associated with mortality in Japanese hemodialysis patients

OBJECTIVE

Coronary artery calcification has been associated with higher mortality in coronary artery disease and chronic kidney disease. This study aimed to correlate coronary artery calcification score (CACS) with all-cause and cardiovascular mortalities in hemodialysis (HD) patients.

DESIGN, SETTING, SUBJECTS

A survival analysis was conducted in 200 HD patients. CACS was assessed by multidetector-row computed tomography and stratified as tertiles: group 1 (0∼105 U), group 2 (110∼1067 U), and group 3 (1094∼15481 U). The duration of follow-up was 7 years and 4 months. Kaplan-Meier method and Cox proportional hazard analysis adjusted for age and HD duration were performed to examine the impact of CACS on survival.

MAIN OUTCOME MEASURE

All-cause and cardiovascular mortalities were measured.

RESULTS

The cumulative all-cause and cardiovascular mortalities of group 1 were significantly lower than those of groups 2 and 3 (all-cause mortality: 7.6% vs. 43.3% and 52.2%, respectively, cardiovascular mortality: 3.0% vs. 22.4% and 26.9%, respectively). Cox proportional hazard analysis adjusted for age and HD duration revealed that all-cause and cardiovascular mortalities of group 1 were significantly lower than those of groups 2 and 3.

CONCLUSION

CACS is helpful to predict prognosis of HD patients independently of age and HD duration.

Relationship between glucose exposure via peritoneal dialysis solutions and coronary artery calcification in non-diabetic peritoneal dialysis patients

INTRODUCTION

Vascular calcification is frequent in dialysis patients and is associated with increased mortality. Impaired glucose metabolism is proposed as a contributing factor for vascular calcification. We investigated whether glucose exposure via dialysate may have a role in vascular calcification in non-diabetic peritoneal dialysis patients.

METHOD

We measured coronary artery calcification by multi-slice computerized tomography in 50 prevalent non-diabetic peritoneal dialysis patients and assessed its relations with fasting blood glucose, homeostasis model assessment of insulin resistance (HOMA-IR), and glucose exposure from peritoneal dialysis fluid.

RESULTS

Twenty-four patients (48%) had no coronary calcification. When patients were grouped according to the presence or absence of calcification, patients with calcification were mostly men and had higher burden of cardiovascular disease history, vitamin D dose intake, serum calcium, total glucose exposure from dialysis solution, and lower total weekly Kt/Vurea. In multivariate analysis, dialysate glucose exposure was an independent predictor of coronary artery calcification score, besides serum calcium and Kt/Vurea.

CONCLUSION

These data suggest that high glucose exposure from dialysis solution, which is potentially correctable, is a risk factor for vascular calcification in non-diabetic PD patients.

Noninvasive imaging for assessment of calcification in chronic kidney disease

Vascular calcification is highly prevalent in patients with chronic kidney disease and has a progressive course. Several cardiovascular and uremia-related risk factors, such as abnormalities in mineral metabolism, contribute to the development of vascular calcification, although the pathophysiological mechanisms are still unclear. The presence and extent of vascular calcification is associated with an increased risk of cardiovascular events and mortality. By contrast, patients who do not have calcification seem to have a good prognosis, with minimal or no calcification progression over an extended period of time. A number of noninvasive imaging methods are available to detect vascular calcification and may help clinicians to make therapeutic decisions. Cardiac CT remains the reference standard to detect and quantify coronary artery, aortic and cardiac valve calcification. However, the high cost of equipment, the inability to perform in-office testing and the expertise required limit its use on a routine basis. Other imaging methods, such as planar X-ray, ultrasound and echocardiography, are appropriate alternatives to evaluate vascular and valvular calcification. In this review, we discuss the noninvasive imaging methods most frequently used to assess vascular and valvular calcification, with their advantages and limitations.

Association between vascular calcification scores on plain radiographs and fatty acid contents of erythrocyte membrane in hemodialysis patients

OBJECTIVE

Vascular calcification (VC) scores determined by using simple plain radiographic films are known to be associated with coronary artery disease and mortality in patients undergoing hemodialysis (HD). Omega-3 fatty acid (FA) has been shown to reduce ectopic calcifications in an animal model, and it has also been shown that erythrocyte membrane omega-3 FA content is an independent discriminator of coronary artery disease. The present study was designed to demonstrate relations between VC scores and erythrocyte membrane FA contents in patients undergoing HD.

DESIGN

A cross-sectional study was carried out.

SETTING

The study was carried out at an outpatient hemodialysis unit at Dong-A University Hospital, Busan, Republic of Korea.

PATIENTS

A total of 31 patients undergoing HD were recruited. Patients with significant malnutrition, a short duration of dialysis (<12 months), a history of recent infection, malignancy, or liver disease were excluded.

MAIN OUTCOME MEASURES

Plain radiographic films of the feet, hands, pelvis, and lateral lumbar spine were examined and VC scores were determined using previously reported methods. Erythrocyte membrane FA contents were analyzed by gas chromatography.

RESULTS

The erythrocyte membrane contents of eicosapentaenoic acid and docosahexaenoic acid were not found to be related with VC on simple plain radiographic films. However, erythrocyte membrane contents of oleic acid and total monounsaturated FA (MUFA) were significantly higher in patients with significant VC scores. Furthermore, erythrocyte membrane contents of MUFA and oleic acid were found to be negatively associated with high-density lipoprotein cholesterol level and positively associated with triglyceride level.

CONCLUSION

Erythrocyte membrane contents of MUFA and oleic acid were found to be associated with VC scores determined using plain radiographs and with dyslipidemia in patients undergoing HD.

Glucose concentration in the dialysate does not contribute to lipid profiles in patients undergoing CAPD

The aim of this study was to investigate lipid profiles in patients with end-stage renal disease receiving hemodialysis (HD), continuous ambulatory peritoneal dialysis (CAPD), or no dialysis (nondialytic treatment group, NT), and to analyze the association between dyslipidemia in CAPD patients with glucose-containing dialysate dosages. Lipid profiles were determined in 64 NT patients, 62 HD patients, and 180 CAPD patients at a single time point. NT patients' samples were collected following hospitalization due to renal failure. HD and CAPD patients' samples were collected after 3 months of dialysis. The association between lipid profiles of 180 CAPD patients and glucose-containing dialysate was analyzed using Pearson methods; 76.56% of NT patients, 66.13% of HD patients, and 72.22% of CAPD patients had dyslipidemia. Compared with NT patients, CAPD patients had significantly altered levels of cholesterol, triglycerides, high-density lipoprotein, apolipoproein (Apo)-A1, and Apo-E (p < 0.05), but unchanged levels of low-density lipoprotein or Apo-B. There was no correlation between the three different concentrations of glucose in the dialysate with the lipid profile of CAPD patients. We concluded that patients on CAPD exhibit dyslipidemia, and that different concentrations of glucose in the dialysate do not affect lipid profiles in these patients.

Effects of sodium thiosulfate on vascular calcification in end-stage renal disease: a pilot study of feasibility, safety and efficacy

BACKGROUND AND OBJECTIVES

Vascular calcification is a major contributor to morbidity and mortality in hemodialysis. The objective of this pilot study was to determine the feasibility, safety and efficacy of sodium thiosulfate (STS) in the progression of vascular calcification in hemodialysis patients.

METHODS

Chronic hemodialysis patients underwent a battery of cardiovascular tests. Those with coronary artery calcium (Agatston scores >50) received intravenous STS after each dialysis for 5 months (n = 22) and the tests were repeated. Changes in MDCT-determined calcification were assessed as the mean annualized rate of change in 3 vascular beds (coronary, thoracic and carotid arteries) and in L1-L2 vertebral bone density.

RESULTS

Although individual analyses showed coronary artery calcification progression in 14/22 subjects, there was no progression in the mean annualized rate of change of vascular calcification in the entire group. The L1-L2 vertebral bone density showed no changes. There were no correlations between rates of progression of vascular calcification and phosphorus, fetuin or C-reactive protein levels. Changes in coronary artery calcification scores correlated with those of the thoracic aorta.

CONCLUSION

STS treatment is feasible, appears safe and may decrease the rate of progression of vascular calcification in hemodialysis patients. A large, randomized, controlled trial is warranted.

Evolution of coronary artery calcification in patients with chronic kidney disease Stages 3 and 4, with and without diabetes

BACKGROUND

The purpose of this study was to report the evolution of coronary artery calcification (CAC) in subjects with chronic kidney disease Stages 3 and 4 comparing those with and without diabetes. We previously reported prevalence in the same population.

METHODS

CAC was measured using multi-slice computer tomography. We prospectively followed up 103 patients for 2 years, 49 with diabetes and 54 without diabetes. Demographic, routine biochemistry, calcification inhibitors and bone mineral density data were collected and analysed. Evolution of CAC was defined as those with a difference of ≥ 2.5 U between baseline and final square root CAC scores.

RESULTS

There were more progressors in the group with diabetes, 24 compared to 12 in the group without diabetes (P= 0.004). When diabetes was present, CAC progressed equally in men and women. Risk factors for evolution of CAC included age, baseline CAC score and serum phosphate levels. Baseline CAC score, phosphate and body mass index were independent predictors for the increase of CAC score during the study period. Severity of CAC was greater in the diabetes group (median CAC score at baseline in the group with diabetes 154 increased to 258 2 years later, P < 0.001).

CONCLUSIONS

Evolution of CAC is greater in older patients and those with diabetes, where the gender advantage of being female is lost. Serum phosphate level, despite being within the normal range and virtually no use of phosphate binders, was also a risk factor. Further studies are required to determine the levels of serum phosphate required to minimize cardiovascular risk.

Evolution of coronary artery calcifications following kidney transplantation: relationship with osteoprotegerin levels

We prospectively assessed the evolution of coronary artery calcification (CAC) and osteoprotegerin (OPG) levels after renal transplantation (RT). Eighty-three recipients were followed-up prospectively during 1 year. Blood was collected before (baseline) and after RT for determination of mineral metabolism parameters including OPG. CAC was measured by multidetector computed tomography at transplantation (baseline) and 1 year later. Progression of CAC was defined as a difference between the follow-up square-root transformed volume (SRV) and the baseline SRV >or= 2.5. By multivariate analysis, baseline OPG level, age and low LDL levels were significantly associated with baseline CAC. RT was accompanied by mineral metabolism improvement with a decrease of OPG from 955 [395-5652] to 527 [217-1818] pg/mL and parathyroid hormone from 94 [1-550] to 62 [16-410] pg/mL. Thirty-one percent of patients did not exhibit CAC at baseline. CAC diminished in 14.5%, stabilized in 59.2% and progressed in 26.3% of patients. Baseline CAC was associated with progression (OR 2.92 [1.02-8.36]). No significant association was found between OPG and CAC progression despite a higher baseline OPG level in progressors (1046 [456-3285]) vs. non-progressors (899 [396-5952] pg/mL). CAC at baseline, but not 1 year after RT, is independently associated with baseline OPG; posttransplant CAC progression is predicted by baseline CAC score.

Relationship between severity of renal impairment and 2-year outcomes after sirolimus-eluting stent implantation

BACKGROUND

The presence of chronic kidney disease (CKD) is associated with an increased risk of restenosis and major adverse cardiac events (MACEs) after coronary interventions, especially in patients on hemodialysis (HD). The aim of this study was to assess the impact of varying degrees of renal impairment on angiographic and 2-year clinical outcomes after treatment with sirolimus-eluting stents (SESs).

METHODS

A total of 675 lesions of 593 patients treated with SES were analyzed. Patients were classified into 3 groups: 34 patients on HD; 337 patients with estimated glomerular filtration rate > or =60 mL min(-1) 1.73 m(-2) (non-CKD group); and 222 patients who had lower estimated glomerular filtration rate <60 mL min(-1) 1.73 m(-2) without HD dependency (CKD group).

RESULTS

At angiographic follow-up (201 +/- 73 days), in-segment late loss was markedly higher in the HD group versus the non-CKD and CKD groups (0.68 +/- 1.06 vs 0.11 +/- 0.45 and 0.15 +/- 0.50 mm, respectively, P < .001), resulting in a significantly higher in-segment restenosis rate (40.0% vs 10.4% and 11.5%, respectively, P < .001). At 2 years, HD vs non-CKD and CKD was associated with a significantly higher MACE rate (35.3% vs 10.4% and 12.6%, respectively, P < .001), mainly driven by significantly higher mortality (11.8% vs 0.6% and 2.3%, respectively, P < .001) and target-lesion revascularization (23.5% vs 9.2% and 8.1%, respectively, P = .016) rates. Multivariable analysis revealed that HD was the independent predictor of 2-year MACE (hazard ratio 4.70, 95% CI 2.40-9.20, P < .001).

CONCLUSIONS

Although angiographic and clinical outcomes after SES implantation were similarly favorable in non-HD-dependent CKD patients, regardless of renal function, in patients with end-stage CKD requiring HD, frequencies of restenosis and 2-year MACE were markedly higher than in non-HD-dependent patients.

Coronary calcification and its association with mortality in haemodialysis patients

AIM

Coronary artery calcification (CAC) has been associated with higher mortality in chronic renal disease. The purpose of this study was to assess coronary artery calcium score (CaCs) in haemodialysis patients and to correlate calcium scores with clinical parameters and mortality.

METHODS

A cross-sectional study was conducted in 59 haemodialysis patients. CaCs was assessed by multidetector-row computed tomography and stratified as: CaCs of less than 10 Agatston units (U), no calcification; CaCs of 10-400 U, mild-to-moderate; and CaCs of more than 400 U, severe calcification. The effects of age, haemodialysis duration and biochemical and inflammatory markers on CaCs logarithm were evaluated by multiple linear regression analysis. Cox regression analysis was used to measure the impact of CaCs of more than 400 on 2-year mortality.

RESULTS

Coronary calcifications were detected in 64.5% of patients, and the median of CaCs was 31.7 U (0-589.7) with a range of 0-5790.0 U. Twenty-one (35.5%) patients had mild-to-moderate and 17 (29%) severe CaCs. Patients with severe CaCs were older and showed a higher prevalence of ischaemic heart disease and a higher body mass index (P=0.04). A trend towards higher C-reactive protein levels was found in patients with severe CaCs. Advanced age was the only variable that influenced CaCs logarithm independently. The effect of severe CaCs on 2-year mortality did not persist after adjustment for other covariates.

CONCLUSION

Coronary calcification was highly prevalent in these uraemic patients on chronic haemodialysis. A correlation was evidenced between CaCs and advanced age, but severity of the CAC score did not have an impact on 2-year mortality of this cohort.

Validity and usefulness of aortic arch calcification in chest X-ray

BACKGROUND

Arterial calcification is associated with cardiovascular (CV) disease, to be leading to vessel wall stiffness and causing the management of hemodynamics in the elderly more difficult. Here, we compared the extent of calcification in the aortic arch by reviewing chest X-rays to that in the abdominal aorta as assessed by more detailed examinations. In addition, the validity of the grading and the relationship of this useful grading to clinical risk factors were evaluated.

METHODS AND RESULTS

The extent of aortic arch calcification (AAC) on a postero-anterior plain chest X-ray was divided into four grades (0 to 3). First, AAC grade was assessed in patients who underwent two quantitative examinations for abdominal aortic calcification; lateral radiograph of lumbar spine and/or computer tomography, and was positively correlated with the abdominal aortic calcification level. Subsequently, AAC grade in 239 out-patients (115 men; mean age, 61.9 years) was also evaluated, and was 0, 1, 2, and 3 in 46%, 22%, 29%, and 4% of the population, respectively, was significantly associated with pulse pressure and intima-media thickness. AAC grade in patients with diabetes or renal dysfunction was significantly higher than in those without each risk, but there was no association with other risk factors. In addition, AAC grade was positively correlated with risk factor clustering.

CONCLUSION

Assessment of AAC detectable on a chest X-ray is very useful and its grade reflects the magnitude of calcified change in the whole aorta. In addition, AAC evaluation may provide supportive information for atherosclerotic risk stratification.

Progression of coronary calcification in pediatric chronic kidney disease stage 5

Coronary artery calcification (CAC) is common in adults with chronic kidney disease (CKD) and progresses with time. However, data are limited for younger patients. We have previously reported CAC in eight of 53 children with CKD. After 2 years, CAC evaluation was repeated in 48 patients. The median CAC score (CACS) increased from 101.3 (1473.6 +/- 1978.6, range 8.5-4332) to 1759.2 (2236.4 +/- 2463.3, range 0-5858) Agatston units (AU). When the individual changes in CACS were evaluated one by one, we showed a mild decrease in two patients on hemodialysis (HD) and in one transplant (Tx) recipient, a moderate increase in one patient on HD, one on peritoneal dialysis (PD) and one Tx recipient, and a large increase in one HD patient. Also, CAC disappeared in one HD patient. All patients with no calcification at baseline remained calcification-free at follow-up. To obtain the individual cumulative exposure, we calculated time-averaged mean values, using the laboratory values from the beginning of dialysis to the first and second multidetector spiral computed tomography (MDCT) scans (baseline and final values, respectively). Final CACS was positively related to final calcium-phosphorus (CaxP) product, while CAC progression was inversely associated with final serum albumin level. This report is the first study with the largest number and the youngest cohort to document the natural history of coronary calcification.

Vascular and Other Tissue Calcification in Peritoneal Dialysis Patients

Cardiovascular disease is the leading cause of mortality in patients with end-stage renal disease (ESRD) and is attributed to a combination of traditional and non-traditional cardiovascular risk factors. In recent years, there has also been an increasing recognition of a very high prevalence of cardiovascular calcification in the ESRD population, including in patients receiving long-term peritoneal dialysis (PD). Numerous observational cohort studies have demonstrated the prognostic importance of cardiovascular calcifications in these patients. The mechanisms are not completely understood, but are likely multifactorial. The present article reviews the prevalence, clinical course, prognostic significance, and some contributing factors for vascular and valvular calcification in ESRD patients, including patients receiving PD therapy.

Associations between oxidized LDL to LDL ratio, HDL and vascular calcification in the feet of hemodialysis patients

Cardiovascular mortality is associated with vascular calcification (VC) in hemodialysis (HD) patients. The present study was designed to find factors related with medial artery calcification on the plain radiography of feet by comparing C-reactive protein (CRP), plasminogen activator inhibitor type 1 (PAI-1) and lipid profile including oxidized low density lipoprotein (ox-LDL) and to elucidate associations among these factors in HD patients. Forty-eight HD patients were recruited for this study. VC in the feet was detected in 18 patients (37.5%) among total patients and 12 patients (85.7%) among diabetic patients. Diabetes, cardiovascular disease (CVD), pulse pressure, ox-LDL/LDL were higher and high density lipoprotein (HDL) was lower in patients with VC than in patients without VC. Negative associations were found between HDL and CRP, PAI-1. PAI-1 had positive association with ox-LDL/LDL. History of CVD was the only determinant of vascular calcification on the plain radiography of feet. Ox-LDL/LDL, HDL, CRP, and PAI-1 were closely related with one another in HD patients. History of CVD is the most important factor associated with the presence of VC and low HDL and relatively high oxidized LDL/LDL ratio may affect VC formation on the plain radiography in the feet of HD patients.

Coronary artery calcification, ADMA, and insulin resistance in CKD patients

BACKGROUND AND OBJECTIVES

It is known that coronary artery calcification (CAC) develops in chronic kidney disease (CKD) before initiation of renal replacement therapy, and factors associated with CKD mineral and bone disorders (CKD-MBDs) are involved. However, little information is available about any association between plasma levels of asymmetric dimethylarginine (ADMA), insulin resistance, and CAC.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

A total of 111 CKD patients (79 men, 32 women; glomerular filtration rate [GFR] median, 33.7 ml/min per 1.73 m(2)), free of cardiovascular disease, were consecutively recruited along with 30 age-matched healthy subjects. Coronary artery calcification scores (CACS) were measured by multidetector-row CT according to Agatston score.

RESULTS

In CKD patients, CACS was distributed widely from 0 to 2901, while in age-matched, healthy control subjects (n = 30), CACS showed a range from 0 to 307. GFR had a significant negative correlation with CACS. Plasma ADMA levels were negatively correlated with GFR and positively correlated with CACS. When CACS was divided into quartiles (<50, n = 56; 50 to 300, n = 24; 300 to 600, n = 14; >600, n = 17), the patients with CACS >600 had significantly higher values of HOMA-IR, plasma ADMA levels, and fibrinogen along with serum levels of phosphorus, compared with those in patients having CACS <50. Multivariate regression analysis determined HOMA-IR as an independent contributing factor to CACS.

CONCLUSIONS

CAC becomes more prevalent and severe with a decline in GFR, and plasma ADMA levels and insulin resistance, independent of factors associated with CKD-MBD, are correlated with CAC.

Determinants of the intima-media thickness in children and adolescents with chronic kidney disease

The aim of the study was to evaluate changes in the arterial wall in children with chronic kidney disease (CKD). We studied 60 patients: 32 with stages 2-4 CKD [chronic renal failure (CRF)], 28 with stage 5 CKD [end-stage renal disease (ESRD)], and 43 controls (C). The evaluated parameters included intima-media thickness (IMT) of the carotid arteries, bone mineral density (BMD), serum lipid levels, and parameters of the calcium-phosphorus metabolism. Patients were divided into two groups: group 1 with normal arteries, and group 2 with arterial changes. The highest serum fetuin A level was found in group 1 compared with groups 2 and C. A negative correlation between IMT and fetuin A level was found. In patients with ESRD, a positive correlation of IMT with phosphorus level and age and a negative correlation with cyclase-activating parathyroid hormone and cyclase inhibiting parathyroid hormone (CAP/CIP) ratio was observed. Multiple linear regression showed that lower fetuin-A and alkaline phosphatase (AP) levels and higher lumbar spine BMD independently predicted higher IMT. Arterial wall changes in children with CKD were related to lower fetuin A and AP level and higher BMD. Low CAP/CIP and high phosphorus level may also be significant factors for arterial changes in patients with ESRD.

Effects of serum calcium, phosphorous, and intact parathyroid hormone levels on survival in chronic hemodialysis patients in Japan

Disturbances in bone mineral metabolism are common in chronic hemodialysis (HD) patients and often underlie morbid conditions and mortality; however, no large epidemiological study for Asian dialysis patients has been performed. We analyzed the database of the Japanese Society for Dialysis Therapy registry. In this study, data from patients who were on HD at the end of 2000 was compiled. The Cox's proportional hazard analysis was carried out to evaluate the significance of the impact of variables related to bone mineral metabolism on survival after adjusting for possible confounding variables. The study period was three years, and a cohort of 27 404 HD patients was studied. The hazard ratios were 1.098 (P = 0.0129) for serum calcium levels ranging 10.0-10.9 mg/dL, and 1.243 (P = 0.0001) for serum calcium levels >11.0 mg/dL when the reference serum calcium level range was 9.0-9.9 mg/dL. Similarly, the hazard ratios were significantly higher in a serum phosphorous level of 5.0 mg/dL than for the reference serum phosphorous level range of 4.0-4.9 mg/dL. For intact parathyroid hormone (iPTH), the hazard ratios were significantly small (<119 pg/mL) when the reference iPTH level range was 180-359 pg/mL. However, the hazard ratio did not increase when the iPTH level increased to >360 pg/mL. Results showed that disturbances in bone mineral metabolism, such as those involving serum calcium, phosphorous, and iPTH, have a significant impact on survival in Japanese dialysis patients.

Pharmacological control of secondary hyperparathyroidism in chronic hemodialysis patients: cinacalcet is coming to Japan

Secondary hyperparathyroidism has a significant impact on morbidity and mortality due to skeletal and extraskeletal manifestations. Cinacalcet, a newly developed calcimimetic, is reported to decrease parathyroidism, as well as serum levels of phosphorus (P) and calcium (Ca) and therefore Ca x P product. Available evidence has shown that cinacalcet decreases the rate of parathyroidectomy and bone fracture in hemodialysis patients, but the death rate remains the same. Although, it is not yet available in Japan, cinacalcet is expected to be available as a possible drug for patients undergoing hemodialysis due to secondary hyperparathyroidism associated with refractory hyperphosphatemia and hypercalcemia. Except for the high cost, cinacalcet will be a welcome therapeutic option for end-stage renal disease and probably also for pre-end-stage renal disease patients. Dietary phosphate restriction and adequate hemodialysis, however, are still the main strategy for the control of hyperphosphatemia and secondary hyperparathyroidism.

Thirty-month follow-up of coronary artery calcification in hemodialysis patients: different roles for inflammation and abnormal calcium-phosphorous metabolism?

BACKGROUND

Cardiovascular disease is the leading cause of death in hemodialysis (HD) patients. Coronary artery calcification (CAC) is considered a marker of atherosclerosis and coronary artery disease (CAD). The CAC progression and factors that influence it were evaluated during a 30-month period.

METHODS

Forty HD patients without a history of CAD were enrolled into the study. CAC score was assessed with conventional CT repeated every six months. The circulating factors of phosphorous, calcium, calcium-phosphorous product, intact parathyroid hormone, total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, triglycerides, lipoprotein-alpha, albumin, high sensitivity C-reactive protein, and fibrinogen were measured monthly. Hypertension and calcium intake during the study period were taken into account as well.

RESULTS

At baseline, CAC score was correlated with age and duration of HD therapy. From all evaluated factors, CAC initiation was influenced only by older age and C-reactive protein. CAC, when it was started, was aggravated continuously and was influenced only by elevated serum phosphorous and calcium-phosphorous product. Hypertension, lipid profile, and calcium intake did not affect CAC initiation or progression.

CONCLUSIONS

Once CAC progression starts, it is an uninterrupted process. The roles of inflammation and abnormal calcium-phosphorous metabolism in CAC differ. Inflammation is the major factor that contributes in CAC initiation. Elevated serum phosphorous and calcium-phosphorous product accelerates CAC progression.

The role of magnesium binders in chronic kidney disease

Magnesium is predominantly an intracellular cation that plays a critical role in cellular physiology. Serum levels are often slightly elevated in patients on chronic hemodialysis and older reports suggests that total body stores may also be increased, based on bone biopsies in patients treated with higher dialysate magnesium levels than are currently in use today. Several studies have shown that magnesium, particularly in the form of magnesium carbonate, is an effective phosphate binder and can decrease patients' exposure to calcium. Retrospective studies suggest that magnesium may prevent vascular calcification in dialysis patients, although this remains controversial and has not been evaluated prospectively. Magnesium may reduce arrhythmias postoperatively and, while it may theoretically reduce arrhythmic death in dialysis patients, this hypothesis has never been tested. While short-term or adjuvant use of magnesium carbonate appears safe and effective as a phosphate binder, more studies are needed to evaluate the long-term effects on vascular calcification, bone histology, and mortality.

The fallacy of the calcium-phosphorus product

Scattered through the practice of medicine are dogmas with little or no scientific basis. One of these is the product of the serum calcium and phosphorus concentrations, the so-called calcium-phosphorus product or Ca x P. The assumption that ectopic calcification will occur when the product of the serum calcium and phosphorus concentrations exceeds a particular threshold has become standard practice in nephrology even though there is little scientific basis. Experimental support is lacking, the chemistry underlying the use of the product is oversimplified and the concept that ectopic calcification is simply the result of supersaturation is biologically flawed. The evidence that the Ca x P is an independent risk factor for mortality and morbidity is also questionable. Although ectopic calcification can occur in many sites, this review will focus on vascular calcification, as it is the most common site and the site most likely to affect patient outcomes.