Reducing the burden of cardiovascular calcification in patients with chronic kidney disease

Unveiling Selected Influences on Chronic Kidney Disease Development and Progression

Currently, more and more people are suffering from chronic kidney disease (CKD). It is estimated that CKD affects over 10% of the population worldwide. This is a significant issue, as the kidneys largely contribute to maintaining homeostasis by, among other things, regulating blood pressure, the pH of blood, and the water-electrolyte balance and by eliminating unnecessary metabolic waste products from blood. What is more, this disease does not show any specific symptoms at the beginning. The development of CKD is predisposed by certain conditions, such as diabetes mellitus or hypertension. However, these disorders are not the only factors promoting the onset and progression of CKD. The primary purpose of this review is to examine renin-angiotensin-aldosterone system (RAAS) activity, transforming growth factor-β1 (TGF-β1), vascular calcification (VC), uremic toxins, and hypertension in the context of their impact on the occurrence and the course of CKD. We firmly believe that a deeper comprehension of the cellular and molecular mechanisms underlying CKD can lead to an enhanced understanding of the disease. In the future, this may result in the development of medications targeting specific mechanisms involved in the decline of kidney function. Our paper unveils the selected processes responsible for the deterioration of renal filtration abilities.

Below-the-Knee Endovascular Revascularization: A Position Statement

Patients with chronic limb-threatening ischemia, the terminal stage of peripheral artery disease, are frequently afflicted by below-the-knee disease. Although all patients should receive guideline-directed medical therapy, restoration of inline flow is oftentimes necessary to avoid limb loss. Proper patient selection and proficiency in endovascular techniques for below-the-knee revascularization are intended to prevent major amputation and promote wound healing. This review, a consensus among an international panel of experienced operators, provides guidance on these challenges from an endovascular perspective and offers techniques to navigate this complex disease process.

Framing Cause-Effect Relationship of Acute Coronary Syndrome in Patients with Chronic Kidney Disease

The main causes of death in patients with chronic kidney disease (CKD) are of cardiovascular nature. The interaction between traditional cardiovascular risk factors (CVRF) and non-traditional risk factors (RF) triggers various complex pathophysiological mechanisms that will lead to accelerated atherosclerosis in the context of decreased renal function. In terms of mortality, CKD should be considered equivalent to ischemic coronary artery disease (CAD) and properly monitored. Vascular calcification, endothelial dysfunction, oxidative stress, anemia, and inflammatory syndrome represents the main uremic RF triggered by accumulation of the uremic toxins in CKD subjects. Proteinuria that appears due to kidney function decline may initiate an inflammatory status and alteration of the coagulation—fibrinolysis systems, favorizing acute coronary syndromes (ACS) occurrence. All these factors represent potential targets for future therapy that may improve CKD patient’s survival and prevention of CV events. Once installed, the CAD in CKD population is associated with negative outcome and increased mortality rate, that is the reason why discovering the complex pathophysiological connections between the two conditions and a proper control of the uremic RF are crucial and may represent the solutions for influencing the prognostic. Exclusion of CKD subjects from the important trials dealing with ACS and improper use of the therapeutical options because of the declined kidney functioned are issues that need to be surpassed. New ongoing trials with CKD subjects and platelets reactivity studies offers new perspectives for a better clinical approach and the expected results will clarify many aspects.

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.

Risk Factors for Peritoneal Dialysis–Associated Peritonitis: The Role of Oral Active Vitamin D

Background

Peritonitis is a major complication of peritoneal dialysis (PD), being associated with hospitalization, catheter loss, technique failure, and increased mortality. Data on various risk factors for peritonitis are inconsistent, and no association with concomitant therapy has been shown.

Methods

We performed a retrospective analysis of all incident and prevalent PD patients ( n = 55) treated in Innsbruck, Austria, between 2000 and 2007. Data consisted of 1291 patient–months and 55 episodes of peritonitis. Patient demographic data, comorbidities, concomitant medication, laboratory parameters, and microbiology results were obtained from the medical records and from the hospital's electronic database.

Results

The mean peritonitis incidence rate was 0.51 episodes/patient–year (range: 0.24 – 0.73 episodes/patient–year) or 1 episode every 23.5 months (range: 16 – 50 months). In a primary analysis including demographic characteristics, comorbidities, laboratory parameters, and concomitant medication, only treatment with oral active vitamin D was associated with a significantly lower risk of peritonitis. Adjusted for time on PD and baseline serum albumin, oral active vitamin D therapy was associated with an 80% reduced relative risk of peritonitis [hazard ratio (HR): 0.20; 95% confidence interval (CI): 0.06 to 0.64; p = 0.007)]. The risk reduction was comparable in patients who received 0.25 μg or more of vitamin D daily (HR: 0.18; 95% CI: 0.05 to 0.65; p = 0.008) and in those who received less than 0.25 μg vitamin D daily (HR: 0.21; 95% CI: 0.06 to 0.77; p = 0.018).

Conclusions

Treatment with oral active vitamin D might be associated with a lower risk of peritonitis in PD patients.

Microvascular Parameters Help to Predict Stroke Risk in the Asian Diabetic Population in Taiwan: A Population Based Case-Control Study

Intensive glycemic control has not shown consistent findings in stroke prevention for diabetes patients, particularly for those with microvascular complications. This case-control study evaluates the risks of stroke in Asian diabetic population with microvascular complications. From the insurance claims of Taiwan, we identified 67,426 type 2 diabetic mellitus (DM) patients with newly diagnosed stroke in 2000–2011 and 134,852 randomly selected controls with DM but without stroke, matched by sex, age, and number of years since diagnosis of DM. Conditional logistic regression analysis measured crude odds ratios (OR) and adjusted odds ratio (aOR) of stroke and 95% confidence intervals (CI) for associations with demographic status, comorbidities, and microvascular complications: retinopathy (RetP), neuropathy (NeuP) or nephropathy (NepP). The aOR of stroke increased significantly associated with each complication: 1.47 with RetP, 1.73 with NeuP and 1.23 with NepP. The risk increased further when there was a combination of complications. The overall aOR of stroke was 2.83 (95% CI 2.58–3.09) for stroke patients with 3 microvascular complications. The corresponding aOR of ischemic stroke was 2.64 (95% CI 2.39–2.91) and that of hemorrhagic stroke was 4.12 (95% CI 3.25–5.22). The number of microvascular complications positively correlated to the prevalence of comorbidity (p < 0.01). This study suggests that microvascular complications are significant stroke predictors, with a greater involvement for ischemic stroke than for hemorrhagic stroke. Multiple microvascular complications interactively increase the stroke risk. Our study contributes to the identification of high-risk subjects for stroke prevention and adequate glycemic control.

Systemic Inflammation Is Associated With Coronary Artery Calcification and All-Cause Mortality in Chronic Kidney Disease

BACKGROUND

Presence of systemic inflammation in chronic kidney disease (CKD) is associated with advanced coronary artery calcification (CAC). The prognostic significance of this association, however, is unknown. We evaluated the associations between CAC, estimated glomerular filtration rate (eGFR) and all-cause mortality, to determine whether the associations differ according to the presence of systemic inflammation.

METHODS AND RESULTS

We followed 30,703 consecutive individuals who underwent CAC measurement for a median of 79 months (IQR, 65-96 months). Patients were categorized according to baseline CAC score (0, 1-99, 100-399 and ≥400), eGFR (<45, 45-59, 60-74, 75-89, 90-104, and ≥105 ml/min/1.73 m(2)) and high-sensitivity C-reactive protein (hsCRP; <2.0, and ≥2.0 mg/L). Prevalence and extent of CAC were greater in those with lower eGFR and higher hsCRP accordingly, even after adjustment. Lower eGFR was strongly associated with higher CAC score (≥400), and the association was more significant in patients with higher hsCRP. The greater CAC burden was associated with worse outcome in the CKD patients (eGFR <60 ml/min/1.73 m(2)) only in those with higher hsCRP.

CONCLUSIONS

Patients with low eGFR and more extensive CAC had greater risk of mortality, and associations differed according to the presence of systemic inflammation. Among the CKD patients, coronary evaluation may be considered for those with elevated hsCRP. (Circ J 2016; 80: 1644-1652).

Why do young people with chronic kidney disease die early?

Cardiovascular disease poses the greatest risk of premature death seen among patients with chronic kidney disease (CKD). Up to 50% of mortality risk in the dialysis population is attributable to cardiovascular disease and the largest relative excess mortality is observed in younger patients. In early CKD, occlusive thrombotic coronary disease is common, but those who survive to reach end-stage renal failure requiring dialysis are more prone to sudden death attributable mostly to sudden arrhythmic events and heart failure related to left ventricular hypertrophy, coronary vascular calcification and electrolyte disturbances. In this review, we discuss the basis of the interaction of traditional risk factors for cardiovascular disease with various pathological processes such as endothelial dysfunction, oxidative stress, low grade chronic inflammation, neurohormonal changes and vascular calcification and stiffness which account for the structural and functional cardiac changes that predispose to excess morbidity and mortality in young people with CKD.

Statins in chronic kidney disease and kidney transplantation

HMG-CoA reductase inhibitors (statins) have been shown to improve cardiovascular (CV) outcomes in the general population as well as in patients with cardiovascular disease (CVD). Statins' beneficial effects have been attributed to both cholesterol-lowering and cholesterol-independent "pleiotropic" properties. By their pleiotropic effects statins have been shown to reduce inflammation, alleviate oxidative stress, modify the immunologic responses, improve endothelial function and suppress platelet aggregation. Patients with chronic kidney disease (CKD) exhibit an enormous increase in CVD rates even from early CKD stages. As considerable differences exist in dyslipidemia characteristics and the pathogenesis of CVD in CKD, statins' CV benefits in CKD patients (including those with a kidney graft) should not be considered unequivocal. Indeed, accumulating clinical evidence suggests that statins exert diverse effects on dialysis and non-dialysis CKD patients. Therefore, it seems that statins improve CV outcomes in non-dialysis patients whereas exert little (if any) benefit in the dialysis population. It has also been proposed that dyslipidemia might play a causative role or even accelerate renal injury. Moreover, ample experimental evidence suggests that statins ameliorate renal damage. However, a high quality randomized controlled trial (RCT) and metaanalyses do not support a beneficial role of statins in renal outcomes in terms of proteinuria reduction or retardation of glomerular filtration rate (GFR) decline.

Vitamin K status in chronic kidney disease

The purpose of this review is to summarize the research to date on vitamin K status in chronic kidney disease (CKD). This review includes a summary of the data available on vitamin K status in patients across the spectrum of CKD as well as the link between vitamin K deficiency in CKD and bone dynamics, including mineralization and demineralization, as well as ectopic mineralization. It also describes two current clinical trials that are underway evaluating vitamin K treatment in CKD patients. These data may inform future clinical practice in this population.

Cardiac findings at necropsy in patients with chronic kidney disease maintained on chronic hemodialysis

Studies of multiple hearts at necropsy are lacking in patients who have been on chronic hemodialysis for chronic kidney disease (CKD). We studied at necropsy 120 patients who had been treated with hemodialysis for more than 1 year (mean, 5.25 ± 4.33 yr). Their ages ranged from 24 to 81 years (mean, 53 yr); 91 (76%) were men. Calcific deposits were present in the heart at necropsy in 74 (62%) patients: in the epicardial coronary arteries in all 74 (62%); in the mitral annular region in 52 (42%) patients, and in the aortic valve cusps in 42 (35%) patients. The frequency and quantity of the cardiac calcific deposits were significantly greater in the older compared with the younger patients, and in those with longer durations of hemodialysis compared with those with shorter durations. Despite the calcific deposits, which were sometimes huge, only 47 (39%) patients had 1 or more coronary arteries narrowed more than 75% in cross-sectional area by atherosclerotic plaques, apparently no patient had clinical evidence of mitral stenosis, and 9 patients had clinical evidence of aortic valve stenosis. Thus, we found that CKD treated with hemodialysis is a major producer of cardiac calcific deposits, some of which can be massive. Only a minority of the calcific deposits, however, appeared to lead to cardiac dysfunction or myocardial ischemia during life.

Vitamin K status and vascular calcification: evidence from observational and clinical studies

Vascular calcification occurs when calcium accumulates in the intima (associated with atherosclerosis) and/or media layers of the vessel wall. Coronary artery calcification (CAC) reflects the calcium burden within the intima and media of the coronary arteries. In population-based studies, CAC independently predicts cardiovascular disease (CVD) and mortality. A preventive role for vitamin K in vascular calcification has been proposed based on its role in activating matrix Gla protein (MGP), a calcification inhibitor that is expressed in vascular tissue. Although animal and in vitro data support this role of vitamin K, overall data from human studies are inconsistent. The majority of population-based studies have relied on vitamin K intake to measure status. Phylloquinone is the primary dietary form of vitamin K and available supplementation trials, albeit limited, suggest phylloquinone supplementation is relevant to CAC. Yet observational studies have found higher dietary menaquinone, but not phylloquinone, to be associated with less calcification. Vascular calcification is highly prevalent in certain patient populations, especially in those with chronic kidney disease (CKD), and it is plausible vitamin K may contribute to reducing vascular calcification in patients at higher risk. Subclinical vitamin K deficiency has been reported in CKD patients, but studies linking vitamin K status to calcification outcomes in CKD are needed to clarify whether or not improving vitamin K status is associated with improved vascular health in CKD. This review summarizes the available evidence of vitamin K and vascular calcification in population-based studies and clinic-based studies, with a specific focus on CKD patients.

Soy protein diet and exercise training increase relative bone volume and enhance bone microarchitecture in a mouse model of uremia

Soy protein consumption and exercise training have been widely studied for their effects on the vasculature and bone in healthy populations, but little is known about the effectiveness of these interventions in chronic kidney disease (CKD). Cardiovascular disease and bone fracture risk are significantly elevated in CKD, and current pharmacological interventions have been unsuccessful in treating these conditions simultaneously. The purpose of this study was to compare the effects of a soy protein diet and endurance exercise training, alone or in combination, on cardiovascular and bone health in a mouse model of renal insufficiency. At 8 weeks of age, 60 female apolipoprotein E(-/-) mice underwent a two-step surgical procedure to induce uremia. These mice were then randomized at 12 weeks of age to one of four treatment groups for the 16-week intervention period: sedentary, control diet (n = 16); sedentary, soy protein diet (n = 18); exercise, control diet (n = 14); and exercise, soy protein diet (n = 12). There were no significant treatment effects on atherosclerotic lesion areas or aortic calcium deposits. We demonstrated a significant main effect of both diet and exercise on relative bone volume, trabecular number, trabecular separation, and trabecular connective density in the proximal femur as measured by microcomputed tomography. There were no treatment effects on trabecular thickness. We also showed a main effect of diet on plasma urea levels. These data suggest that soy protein intake and exercise training exert beneficial effects on properties of bone and plasma urea levels in mice with surgically induced renal impairment.

Exposure to uremic serum induces a procalcific phenotype in human mesenchymal stem cells

OBJECTIVE

Medial artery calcification in patients with chronic kidney disease proceeds through intramembranous ossification resulting from osteoblast-induced calcification of the collagen extracellular matrix. The current study is based on the hypothesis that mesenchymal stem cells (MSC) constitute critical cells for procalcific extracellular matrix remodeling in patients with chronic kidney disease.

METHODS AND RESULTS

Human MSC were cultured in media supplemented with pooled sera from either healthy or uremic patients (20%). Exposure to uremic serum enhanced the proliferation of MSC (cell counting, BrdU incorporation) whereas apoptosis and necrosis were not affected (annexin V and 7-amino-actinomycin staining). Uremic serum-exposed MSC recapitulated osteogenesis by matrix calcification and expression of bone-related genes (bone morphogenetic protein [BMP]-2 receptor, alkaline phosphatase, osteopontin, and Runx2) in 35 days. The uremic serum-induced osteogenesis was completely blocked by a BMP-2/4 neutralizing antibody or the natural antagonist NOGGIN. Calcification and matrix remodeling were further analyzed in a collagen-embedded osteogenesis model recapitulating the vascular collagen I/III environment. The uremic serum-induced calcification was shown to occur along collagen fibers as shown by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and von Kossa staining and was accompanied by extensive matrix remodeling.

CONCLUSIONS

Uremic serum induced in a BMP-2/4-dependent manner an osteoblast-like phenotype in MSC accompanied by matrix remodeling and calcification.

Dialysis Outcomes and Practice Patterns Study estimate of patient life-years attributable to modifiable haemodialysis practices in Sweden

OBJECTIVE

To examine the association of adherence to Swedish Society of Nephrology guidelines on haemodialysis treatment and patient outcomes in Sweden.

MATERIAL AND METHODS

A prevalent cross-sectional sample of Swedish haemodialysis patients was obtained from the Dialysis Outcomes and Practice Patterns Study (DOPPS II, 2002-2004), an international, prospective, cohort study that investigates relationships between patient outcomes and haemodialysis practices. The sample was used to estimate life-years gained through adherence to six potentially modifiable practice patterns: dialysis dose, anaemia, serum phosphorus, serum calcium, serum albumin and catheter use for vascular access. Cox proportional hazards regression models were used to calculate the relative risk of mortality for all patients outside each guideline.

RESULTS

The practices resulting in the largest patient-year gains were increasing patient albumin above 35 g/l and reducing facility catheter use to below 10%. Compliance with the albumin target levels could save approximately 441 life-years (or as many as 904 years). Similarly, by 2010, 409 life-years (or as many as 837 years) could be saved if vascular access target levels were achieved.

CONCLUSION

The analysis suggests potential opportunities to improve haemodialysis patient care in Sweden. Estimates of life-years saved may serve as motivation for the improvement of patient care through adherence to published guidelines supported by international data from the DOPPS.

Improved survival of type 2 diabetic patients on renal replacement therapy in Finland

BACKGROUND

Survival of type 2 diabetes mellitus patients on maintenance dialysis therapy is poor mainly due to cardiovascular events. The aim was to examine whether survival of type 2 diabetes patients on renal replacement therapy (RRT) in Finland has improved during 1995-2005.

METHODS

Patients who entered RRT because of type 2 diabetes mellitus in 1995-99 (n = 314) and 2000-05 (n = 583) were identified within the Finnish Registry for Kidney Diseases. The two cohorts were followed up from start of RRT until death or end of follow-up on 31 December 2006. Survival probabilities and probabilities of receiving a kidney transplant were calculated using Kaplan-Meier curves. Multivariate modelling was performed using Cox regression.

RESULTS

Patients who entered RRT in 2000-05 had lower risk of dying than those who entered in 1995-99; hazard ratio (HR) was 0.76 (95% CI 0.65-0.89) and 0.74 (95% CI 0.63-0.87) with adjustment for age and gender. The decreased risk of death was most obvious in age groups 55-64 (HR 0.67, 95% CI 0.49-0.92) and 65-74 years (HR 0.69, 95% CI 0.56-0.87). Adjustment for albumin in addition to age and gender only slightly weakened the effect of study periods (HR 0.83, 95% CI 0.69-1.01). The patients in 2000-05 were more obese, had lower total and LDL cholesterol and higher HDL cholesterol and albumin concentration in serum than patients in 1995-99. Patients' probability to receive a kidney transplant was low in both groups.

CONCLUSIONS

Survival of type 2 diabetes patients on RRT improved during the time period 1995-2005 in Finland while the probability of receiving a kidney transplant remained low and unchanged.

A cut-off value of plasma osteoprotegerin level may predict the presence of coronary artery calcifications in chronic kidney disease patients

BACKGROUND

Expression of bone proteins resulting from transdifferentiation of vascular smooth muscle cells into osteoblasts suggests that vascular calcifications are a bioactive process. Osteoprotegerin (OPG) could play a key role in bone-vascular calcification imbalance and could be a marker of vascular calcification extent and progression. The purpose of this study was to evaluate relationships between vascular risk biomarkers (including classic risk factors and OPG) and coronary artery calcification (CAC) extent in chronic kidney disease (CKD) patients and to establish within the markers the appropriate cut-off value to predict CAC.

METHODS

A total of 133 non-dialyzed CKD patients at various stages of kidney disease [75 males/58 females, median age: 69.9 (27.4-94.6)] were enrolled, excluding extrarenal replacement therapy patients. All underwent chest multidetector computed tomography for CAC scoring. Blood samples were collected for measurement of vascular risk markers (kidney disease, inflammation, nutrition, calcium phosphate and OPG). A potential relationship between CAC and these biological markers was investigated, and a receiver-operating characteristic (ROC) curve was designed thereafter to identify a cut-off value of involved markers that best predicted the presence of CAC.

RESULTS

After adjustment for age, diabetes, smoking and gender, among biological markers, only low-estimated glomerular filtration rate using Modification of Diet in Renal Disease [OR = 3.63 (1.10-12.02)], high FEPO(4) [OR = 3.99 (1.17-13.6)] and high OPG levels [OR = 8.54 (2.14-34.11)] were associated with the presence of CAC. A protective effect of 1.25(OH)(2) vitamin D [OR = 0.20 (0.05-0.79)] and LDL cholesterol [OR = 0.27 (0.08-0.94)] on CAC was also observed. ROC curve analysis showed that the OPG best cut-off value predicting CAC was 757.7 pg/mL.

CONCLUSION

These results suggest that a CAC increase is strongly associated with a plasma OPG increase in CKD patients. The values of OPG >757.7 pg/mL allow us to predict the presence of CAC in these patients.

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.

Serum phosphorus levels associate with coronary atherosclerosis in young adults

Phosphorus levels correlate with atherosclerosis in both animal models and humans with advanced chronic kidney disease, but whether this relationship exists among individuals with normal kidney function is unknown. This study aimed to determine whether an association exists between phosphorus levels and coronary artery calcium levels in a community-based cohort of 3015 healthy young adults in the prospective Coronary Artery Risk Development in Young Adults (CARDIA) study. Phosphorus levels were measured at baseline, and presence of coronary artery calcium was assessed by computed tomography 15 yr later. Mean age at study inception was 25.2 yr, and the mean levels of phosphorus and calcium were 3.6 and 9.5 mg/dl, respectively. Only 0.2% of participants had estimated GFR <60 ml/min per 1.73 m(2). Phosphorus levels were associated with coronary artery calcium in unadjusted models. In multivariate models, however, phosphorus levels were significantly associated with the category of coronary artery calcium level. In conclusion, higher serum phosphorus levels, even within the normal range, may be a risk factor for coronary artery atherosclerosis in healthy young adults.

Calcium-phosphate levels and cardiovascular disease in community-dwelling adults: the Atherosclerosis Risk in Communities (ARIC) Study

BACKGROUND

Calcium-phosphate levels, linked to vascular dysfunction in chronic kidney disease, may represent novel risk factors for coronary heart disease, stroke, and death in community-dwelling adults.

METHODS

We tested this hypothesis over 12.6 years of follow-up in the prospective, community-based Atherosclerosis Risk in Communities Study (n = 15,732).

RESULTS

At baseline, mean (SD) values were 9.8 (0.4) mg/dL for serum calcium, 3.4 (0.5) mg/dL for serum phosphate, 33.6 (5.3) mg(2)/dL(2) for calcium-phosphate product, 54.2 (5.7) years for age, and 93.1 (21.5) mL/min per 1.73 m(2) for glomerular filtration rate (GFR). Shared associations of calcium, phosphate, and calcium-phosphate product included older age, female sex, African American race, cigarette-years, current cigarette smoking, low body mass index, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, triglycerides, low serum albumin, low GFR, low caloric intake, and phosphorus intake. With adjustment for age, demographic characteristics, comorbid conditions, albumin, and GFR, calcium-associated hazards ratios for coronary heart disease, stroke, and death were, respectively, 1.01 (95% confidence interval 0.96-1.06), 1.16 (1.07-1.26, P = .0005), and 1.03 (0.98-1.08); phosphate-associated hazards ratios were 1.03 (0.98-1.08), 1.11 (1.02-1.21, P = .0219), and 1.14 (1.09-1.20, P < .0001); calcium-phosphate product-associated hazards ratios were 1.03 (0.98-1.08), 1.15 (1.05-1.26, P = .0017), and 1.15 (1.09-1.20, P < .0001).

CONCLUSIONS

Although calcium, phosphate, and calcium-phosphate product levels exhibit complex associations with traditional cardiovascular risk factors and outcomes, they may be potentially modifiable risk factors for stroke and death in community-dwelling adults.

Abdominal aortic calcification in dialysis patients: results of the CORD study

Background. Patients with chronic kidney disease stage 5 have a high prevalence of vascular calcification, but the specific anatomical distribution and severity of abdominal aortic calcification (AAC), in contrast to coronary calcification, is less well documented. AAC may be recorded using plain radiographs. The present report is an analysis of baseline data on AAC in patients enrolled in the CORD (Calcification Outcome in Renal Disease) study.

Methods. A total of 47 centres in six European countries participated in this cross-sectional study. Inclusion criteria were age ≥18 years and duration of dialysis ≥3 months. Lateral lumbar radiography of the abdominal aorta was used to determine the overall AAC score, which is related to the severity of calcific deposits at lumbar vertebral segments L1–L4. The reliability of the method was tested by double reading of 64 radiographs (coefficient of correlation 0.9).

Results. A lateral lumbar radiograph was obtained in 933 patients. Calcification (AAC score ≥ 1) was present in 81% of the patients; its severity increased significantly from L1 to L4 (P < 0.0001) and affected all of these segments in 51% of patients. Independent predictors for the presence and severity of calcification were age (odds ratio [OR] 1.103/year; P < 0.0001), duration of dialysis (OR 1.110/year; P = 0.002) and history of cardiovascular disease (OR 3.247; P < 0.0001).

Conclusions. AAC detected by lateral lumbar radiograph is associated with several risk factors of uraemic calcification. This semi-quantitative method is more widely available and less expensive than the current procedures for studying calcification and could form part of a pre-transplant workup and cardiovascular risk stratification.

Arterial calcification increases in distal arteries in patients with peripheral arterial disease

The aim of this study was to determine if significant differences in plaque composition exist between the popliteal and tibial vessels in patients with severe peripheral arterial disease (PAD). Forty-four patients with PAD required either above-knee (n = 38), below-knee (n = 5), or through-knee (n = 1) amputation for pedal sepsis/gangrene. The 51 vessels (anterior tibial, n = 9; posterior tibial, n = 10; peroneal, n = 3; popliteal, n = 29) were obtained and underwent intravascular ultrasound (IVUS) evaluation ex vivo within 24 hr of amputation. Sequential IVUS data were obtained at known intervals throughout the vessel length and then analyzed with radiofrequency techniques for quantification of plaque composition, plaque volume, and total vessel volume. Plaque composition was categorized as fibrous, fibro-fatty, necrotic core, and dense calcium. Clinical data were obtained via review of electronic records at the time of amputation. Two-sided t-tests were performed to compare components within each plaque. Results are expressed as mean percentage +/- standard error of the mean. Tibial vessels had more dense calcium within these plaques than popliteal arteries (33.8 +/- 5.6% vs. 10.6 +/- 1.9%, p < 0.001). Consequently, distal vessels had less fibro-fatty and fibrous plaque than popliteal arteries (7.7 +/- 1.4% vs. 13.1 +/- 1.2%, p < 0.005; 42.4 +/- 4.7% vs. 61.4 +/- 2.2%, p < 0.001, respectively). Necrotic core plaque composition was found to be similar when comparing tibial versus popliteal arteries (16.1% vs. 14.9%, p = nonsignificant). Clinical factors including diabetes, hyperlipidemia, and chronic renal insufficiency were not associated with plaque composition differences using a univariate analysis. As we progress distally in the arterial tree of patients with PAD, calcium plaque content increases with decreasing burden of fibro-fatty plaque. Clinical and demographic factors, with the exception of smoking, were not found to be associated with atherosclerotic plaque composition.

A 1-year randomized trial of calcium acetate versus sevelamer on progression of coronary artery calcification in hemodialysis patients with comparable lipid control: the Calcium Acetate Renagel Evaluation-2 (CARE-2) study

BACKGROUND

Previous clinical trials showed that progression of coronary artery calcification (CAC) may be slower in hemodialysis patients treated with sevelamer than those treated with calcium-based phosphate binders. Because sevelamer decreases low-density lipoprotein cholesterol (LDL-C) levels, we hypothesized that intensive lowering of LDL-C levels with atorvastatin in hemodialysis patients treated with calcium acetate would result in CAC progression rates similar to those in sevelamer-treated patients.

STUDY DESIGN

Randomized, controlled, open-label, noninferiority trial with an upper bound for the noninferiority margin of 1.8.

SETTING & PARTICIPANTS

203 prevalent hemodialysis patients at 26 dialysis centers with serum phosphorus levels greater than 5.5 mg/dL, LDL-C levels greater than 80 mg/dL, and baseline CAC scores of 30 to 7,000 units assessed by means of electron-beam computed tomography.

INTERVENTIONS

103 patients were randomly assigned to calcium acetate, and 100 patients to sevelamer for 12 months to achieve phosphorus levels of 3.5 to 5.5 mg/dL. Atorvastatin was added to achieve serum LDL-C levels less than 70 mg/dL in both groups.

OUTCOMES & MEASUREMENTS

The primary end point was change in CAC score assessed by means of electron-beam computed tomography.

RESULTS

After 12 months, mean serum LDL-C levels decreased to 68.8 +/- 22.0 mg/dL in the calcium-acetate group and 62.4 +/- 23.0 mg/dL in the sevelamer group (P = 0.3). Geometric mean increases in CAC scores were 35% in the calcium-acetate group and 39% in the sevelamer group, with a covariate-adjusted calcium acetate-sevelamer ratio of 0.994 (95% confidence interval, 0.851 to 1.161).

LIMITATIONS

Treatment assignment was not blinded. The 1.8 a priori margin is large, CAC is a surrogate outcome, duration of treatment was short, and dropout rate was high.

CONCLUSIONS

With intensive lowering of LDL-C levels for 1 year, hemodialysis patients treated with either calcium acetate or sevelamer experienced similar progression of CAC.

Temporary worsening of renal function after aortic surgery is associated with higher long-term mortality

BACKGROUND

Little is known about acute changes in renal function in the postoperative period and the outcome of patients undergoing major vascular surgery. Specifically, data are scarce for patients in whom renal function temporarily decreases and returns to baseline at 3 days after surgery.

STUDY DESIGN

Retrospective cohort study.

SETTING & PARTICIPANTS

1,324 patients who underwent elective open abdominal aortic aneurysm surgery in a single center.

PREDICTOR

Renal function (creatinine clearance was measured preoperatively and on days 1, 2, and 3 after surgery. Patients were divided into 3 groups: group 1, improved or unchanged (change in creatinine clearance, +/-10% of function compared with baseline); group 2, temporary worsening (worsening > 10% at day 1 or 2, then complete recovery within 10% of baseline at day 3); and group 3, persistent worsening (>10% decrease compared with baseline).

OUTCOMES & MEASUREMENTS

All-cause mortality.

RESULTS

30-day mortality rates were 1.3%, 5.0%, and 12.6% in groups 1 to 3, respectively. Adjusted for baseline characteristics and postoperative complications, 30-day mortality was the greatest in patients with persistent worsening of renal function (hazard ratio [HR], 7.3; 95% confidence interval [CI], 2.7 to 19.8), followed by those with temporary worsening (HR, 3.7; 95% CI, 1.4 to 9.9). During 6.0 +/- 3.4 years of follow-up, 348 patients (36.5%) died. Risk of late mortality was 1.7 (95% CI, 1.3 to 2.3) in the persistent-worsening group followed by those with temporary worsening (HR, 1.5; 95% CI, 1.2 to 1.4).

LIMITATIONS

No steady state was achieved to assess renal function.

CONCLUSION

Although renal function may recover completely after aortic surgery, temporary worsening of renal function was associated with greater long-term mortality.

Chronic kidney disease: effects on the cardiovascular system

Accelerated cardiovascular disease is a frequent complication of renal disease. Chronic kidney disease promotes hypertension and dyslipidemia, which in turn can contribute to the progression of renal failure. Furthermore, diabetic nephropathy is the leading cause of renal failure in developed countries. Together, hypertension, dyslipidemia, and diabetes are major risk factors for the development of endothelial dysfunction and progression of atherosclerosis. Inflammatory mediators are often elevated and the renin-angiotensin system is frequently activated in chronic kidney disease, which likely contributes through enhanced production of reactive oxygen species to the accelerated atherosclerosis observed in chronic kidney disease. Promoters of calcification are increased and inhibitors of calcification are reduced, which favors metastatic vascular calcification, an important participant in vascular injury associated with end-stage renal disease. Accelerated atherosclerosis will then lead to increased prevalence of coronary artery disease, heart failure, stroke, and peripheral arterial disease. Consequently, subjects with chronic renal failure are exposed to increased morbidity and mortality as a result of cardiovascular events. Prevention and treatment of cardiovascular disease are major considerations in the management of individuals with chronic kidney disease.

Regression of warfarin-induced medial elastocalcinosis by high intake of vitamin K in rats

Arterial calcification (AC) is generally regarded as an independent risk factor for cardiovascular morbidity and mortality. Matrix Gla protein (MGP) is a potent inhibitor of AC, and its activity depends on vitamin K (VK). In rats, inactivation of MGP by treatment with the vitamin K antagonist warfarin leads to rapid calcification of the arteries. Here, we investigated whether preformed AC can be regressed by a VK-rich diet. Rats received a calcification-inducing diet containing both VK and warfarin (W&K). During a second 6-week period, animals were randomly assigned to receive either W&K (3.0 mg/g and 1.5 mg/g, subsequently), a diet containing a normal (5 microg/g) or high (100 microg/g) amount of VK (either K1 or K2). Increased aortic calcium concentration was observed in the group that continued to receive W&K and also in the group changed to the normal dose of VK and AC progressed. Both the VK-rich diets decreased the arterial calcium content by some 50%. In addition, arterial distensibility was restored by the VK-rich diet. Using MGP antibodies, local VK deficiency was demonstrated at sites of calcification. This is the first study in rats demonstrating that AC and the resulting decreased arterial distensibility are reversible by high-VK intake.