Trends in coronary artery calcification in peritoneal dialysis and transplant patients

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.

Prevalence and correlates of mitral annular calcification in adults with chronic kidney disease: Results from CRIC study

BACKGROUND

Risk factors for mitral annular calcification (MAC) and cardiovascular disease (CVD) demonstrate significant overlap in the general population. The aim of this paper is to determine whether there are independent relationships between MAC and demographics, traditional and novel CVD risk factors using cardiac CT in the Chronic Renal Insufficiency Cohort (CRIC) in a cross-sectional study.

METHODS

A sample of 2070 subjects underwent coronary calcium scanning during the CRIC study. Data were obtained for each participant at time of scan.

SUBJECTS

were dichotomized into the presence and absence of MAC. Differences in baseline demographic and transitional risk factor data were evaluated across groups. Covariates used in multivariable adjustment were age, gender, BMI, HDL, LDL, lipid lowering medications, smoking status, family history of heart attack, hypertension, diabetes mellitus, phosphate, PTH, albuminuria, and calcium.

RESULTS

Our study consisted of 2070 subjects, of which 331 had MAC (prevalence of 16.0%). The mean MAC score was 511.98 (SD 1368.76). Age and white race remained independently associated with presence of MAC. Decreased GFR was also a risk factor. African American and Hispanic race, as well as former smoking status were protective against MAC. In multivariable adjusted analyses, the remaining covariates were not significantly associated with MAC. Among renal covariates, elevated phosphate was significant.

CONCLUSION

In the CRIC population, presence of MAC was independently associated with age, Caucasian race, decreased GFR, and elevated phosphate. These results are suggested by mechanisms of dysregulation of inflammation, hormones, and electrolytes in subjects with renal disease.

Advanced abdominal arterial calcification sparing kidney allograft--case report

Excess and progressing arterial calcification is a frequent finding in patients with chronic kidney disease and in diabetics. Vascular calcification present in patients on dialysis, usually continues to progress (although possibly with slower rate) in patients after kidney transplantation. These observations are limited mostly to aorta and coronary arteries; virtually no data exist on progression in vascular calcification within the vasculature of transplanted kidney. The case report presents the patient with diabetes and non-functioning renal transplant back on dialysis with extremely severe intra-abdominal artery calcification, sparing renal artery of transplanted kidney. Calcification did not develop within transplanted kidney despite 10 years of exposition to diabetic environment and a few years of chronic kidney disease after transplantation, including CKD-T stage 5 for at least one year after re-starting of dialysis. To the best of our knowledge, this is the second report ever describing sparing of kidney graft from calcification despite disseminated calcification in other vascular beds. It is tempting to speculate that some "intrinsic" factors exist within the transplanted kidney that protects it from calcification despite exposure to procalcifying milieu of diabetes and uremia.

Prevalence and progression of cardiovascular calcifications in peritoneal dialysis patients: A prospective study

BACKGROUND

Patients on dialysis may have abnormal serum levels of Ca, P and parathyroid hormone, with related bone diseases. This population has an increased risk of death, with cardiovascular calcification (CC) a contributing factor. Patients on peritoneal dialysis appear to be at increased risk of hyperlipidemia, a contributing factor to atherosclerotic plaque formation. Although several studies have described the presence and progression of CC in hemodialysis populations, there are fewer data in patients on peritoneal dialysis.

STUDY DESIGN

The Renal Osteodystrophy and Calcifications: Key factors in Peritoneal Dialysis (ROCK-PD) study was a 36-month, prospective observational study conducted in Italy. The study examined the presence and progression of CC in two cardiac valves and five arterial sites. The potential associations of serum Ca and P with mortality and cardiovascular morbidity, demographic, clinical and blood chemistry variables was investigated.

RESULTS

CC was present in 77% of patients at baseline (N=369) and in 90% of patients by study end (N=145), progressing in 73% of patients. There were 42 deaths (11%). Analyses showed a marked correlation between baseline P levels and the presence of left ventricular hypertrophy. However, there were no consistent correlations between serum Ca or P with mortality or morbidity.

CONCLUSIONS

CC was common in peritoneal dialysis patients and progressed in a majority of 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.

Phosphate Balance on Peritoneal Dialysis

Hyperphosphatemia is an independent predictor of mortality in end-stage renal disease patients, and 40% – 50% of peritoneal dialysis (PD) patients have suboptimal control of serum phosphate. Systematically addressing this problem requires an understanding of phosphate balance on PD. The present review discusses the determinants of daily phosphate load and focuses on the factors influencing renal and peritoneal clearance of phosphate.

Determinants of coronary artery calcification progression in renal transplant recipients

Coronary artery calcification (CAC) is associated with increased atherosclerotic burden and cardiovascular events. The objective of this study was to determine the natural history and risk factors associated with CAC progression in a cohort of incident asymptomatic renal transplant recipients with no history of coronary revascularization. Electron-beam computed tomography was performed in 82 subjects at time of transplantation and at least 1 year later. Mean (SD) and median CAC score increased for all subjects from 392.4 (747.9) and 75.8 at time of transplant to 475.3 (873.5), (p = 0.002[log]) and 98.9 (p < 0.001), respectively. Most subjects (89%) with no calcifications remained without calcification. Mean annualized rate (SD) of CAC score change was 52.5 (150) with a median of 0.5. Average yearly percent change was 67.3 (409.6) with a median of 1.4. In multivariate analysis, diastolic blood pressure at 3 months post-transplant, Caucasian race, glomerular filtration rate at 3.0, months post-transplant, body mass index and baseline CAC score were independent predictors of annualized rate of CAC change. There is significant progression of CAC post-renal transplantation in most subjects. Progression is most likely to occur in white patients and is associated with clinical factors such as blood pressure, body mass index, renal function and baseline CAC score.

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

Patients with chronic kidney disease (CKD) have a higher burden of atherosclerotic coronary artery disease compared with age- and gender-matched individuals with normal renal function. Cardiovascular calcification (CVC), a marker of atherosclerosis, is also more prevalent in these patients and is associated with serious clinical consequences. The pathogenesis of CVC is complex and includes factors that promote calcification and others that inhibit calcification. Thus, multiple therapeutic interventions should be used simultaneously to reduce the burden of calcification in patients with CKD. Thus far, interventional attempts have focused on curtailing the effects of factors that promote calcification such as management of known traditional factors for atherosclerotic coronary artery disease and on adopting specific approaches to normalize mineral metabolism, deliver adequate dialysis, and control serum cholesterol level. By contrast, interventions that may bolster the effects of inhibitors of calcification have not yet been studied well but are beginning to attract attention. Ideally, the goal of interventions is not only to slow or halt progression of calcification but also to reverse pre-existing calcification. Whether this goal is achievable is not currently known. This review examines the potential of various therapeutic interventions in reducing the CVC burden in patients with CKD. Moreover, the review is intended to stimulate more research in this area because the efficacy of these interventions has not been examined in controlled clinical trials.