Cardiovascular risk factors, cardiac function and vascular disease in children with CRF 785 42. Gabriel SB, Schaffner SF, Nguyen H et al. The structure of haplotype 46. Yang SP, Woolf AS, Yuan HT et al. Potential biological role of trans- blocks in the human genome. Science 2002; 296: 2225–2229 forming growth factor-β1 in human congenital kidney malforma- 43. Clark AT, Young RJ, Bertram JF. In vitro studies on the roles of trans- tions. Am J Pathol 2000; 157: 1633–1647 forming growth factor-β1 in rat metanephric development. Kidney Int 47. Stevens A, Soden J, Brenchley PE et al. Haplotype analysis of the 2001; 59: 1641–1653 polymorphic human vascular endothelial growth factor gene promoter. 44. Michael L, Davies JA. Pattern and regulation of cell proliferation Cancer Res 2003; 63: 812–816 during murine ureteric bud development. J Anat 2004; 204: 241 45. Karihaloo A, Nickel C, Cantley LG. Signals which build a tubule. Nephron Exp Nephrol 2005; 100: e40–e45 Received for publication: 21.7.09; Accepted in revised form: 16.9.09

Nephrol Dial Transplant (2010) 25: 785–793 doi: 10.1093/ndt/gfp570 Advance Access publication 23 November 2009 Downloaded from https://academic.oup.com/ndt/article/25/3/785/1912566 by guest on 23 September 2021 A comprehensive study of cardiovascular risk factors, cardiac function and vascular disease in children with chronic renal failure

Choni Rinat1,5, Rachel Becker-Cohen1,5, Amiram Nir2,5, Sofia Feinstein1,5, David Shemesh3, Nurit Algur4, Efrat Ben Shalom1,5, Benjamin Farber2 and Yaacov Frishberg1,5

1Pediatric Nephrology, Shaare Zedek Medical Center, Jerusalem, Israel, 2Pediatric Cardiology, Shaare Zedek Medical Center, Jerusalem, Israel, 3Vascular Laboratory and Surgery, Shaare Zedek Medical Center, Jerusalem, Israel, 4Clinical Laboratory, Shaare Zedek Medical Center, Jerusalem, Israel and 5Hadassah-Hebrew University School of Medicine, Jerusalem, Israel Correspondence and offprint requests to: Choni Rinat; E-mail: [email protected]

Abstract possible interventions to prevent cardiovascular morbidity Background. Cardiovascular disease causes major mor- and mortality in this high risk population are needed. bidity and is an important determinant of premature death in the paediatric chronic kidney disease (CKD) population. Keywords: arterial stiffening; CVS risk factors; myocardial dysfunction; renal failure; uric acid It is composed of three separate, although interrelated, dis- ease processes: atherosclerosis, arteriosclerosis (i.e. medial vascular calcifications) and myocardial disease. Myocardi- al consequences of atherosclerosis barely exist in children, thus providing a good opportunity to investigate the role Introduction that kidney disease plays in the development of cardiovas- cular disease. Improvement in therapeutic modalities in children with Methods. We assessed 70 patients, aged 4months to 18 chronic renal failure (CRF) and the consequent extension years, with chronic kidney disease stages 3–5, for known of their life expectancy have drawn more attention towards risk factors of cardiovascular disease and for additional secondary complications [1,2]. Cardiovascular (CVS) dis- laboratory and clinical variables which may have an impact ease is the leading cause of death in adults with chronic on this disease process. Carotid artery ultrasound was used kidney disease (CKD) [3,4] and has also been shown to to evaluate vascular structure and function, whereas myo- be a late complication in children with renal failure [5,6]. cardial disease was assessed by echocardiography. Early appearance of vascular disease in patients with Results. Traditional risk factors, although present in this CKD is attributed to the combination of two parallel pro- cohort, did not accumulate with progression of chronic kid- cesses: atherosclerosis and arteriosclerosis. High preva- ney disease. Non-traditional risk factors increased in num- lence of traditional cardiovascular risk factors, such as ber and severity in correlation with the stage of CKD. The hypertension and dyslipidemia, are responsible for the for- main myocardial abnormalities were left ventricular hyper- mation of the intimal atherosclerotic plaque. On the other trophy and diastolic dysfunction. Vascular function tests hand, there are newly emerging risk factors for the devel- correlated with calcium–phosphate metabolism variables, opment of medial arteriosclerosis, which are all related to homocysteine and time-averaged serum uric acid. calcium phosphorous metabolism. Importantly, it has been Conclusions. This study shows that children with CKD shown that the presence of CVS risk factors already in are exposed to risk factors and demonstrate signs of car- childhood may lead to atherosclerosis in adulthood [7– diovascular disease already at a young age. The possible 9]. Very long-standing haemodialysis starting in childhood role of uric acid and homocysteine in the evolution of car- results in a very high prevalence (87.5%) of coronary cal- diovascular disease is discussed. Further studies looking at cifications [10]. Furthermore, the majority of children with

© The Author 2009. Published by Oxford University Press on behalf of ERA-EDTA. All rights reserved. For Permissions, please e-mail: [email protected] 786 C. Rinat et al. CKD will need one or more renal transplantations during Estimated GFR (eGFR) was calculated using the Schwartz equation their lifetime, which carries its own risk for CVS disease and compared to normal values for age and gender. The same process [11]. Altogether, this particular population is at a very high of time-averaged eGFR was conducted. risk for vascular disease. This statement was recently sup- ported by the American Heart Association, stratifying Echocardiography these patients in the same high risk group together with Echocardiography was performed by a senior paediatric cardiologist using those having homozygous familial hypercholesterolaemia, HP Sonos 4500 and Vivid GE 7 machines. In patients undergoing haemo- type 1 diabetes mellitus and post-orthostatic heart trans- dialysis, the study was performed immediately following treatment once plantation [12]. they reached their dry weight. Left ventricular mass (LVM) was calculated It is therefore obvious that early recognition, identifica- using measurements obtained by two-dimensional echocardiography and the LVM index (LVMI) calculated to correct for patients' height: LVMI = tion and treatment of any risk factor are prudent. LV mass/height2.7 [18]. LVMI in infants and toddlers whose height is <1m A different aspect of cardiovascular disease in patients was compared to the normal range of this age group [19]. This was intended with CKD is the myocardial damage secondary to hyperten- to avoid false-positive values in the very young, as LVMI is expressed per height in metres to the power of 2.7, which could erroneously result in very

sion, volume overload [13,14] or the state of uraemia per se. Downloaded from https://academic.oup.com/ndt/article/25/3/785/1912566 by guest on 23 September 2021 high values. Left ventricular end diastolic diameter (LVEDD) was indexed In this comprehensive cross-sectional study, we eval- to the 90th percentile for the patients' age. Shortening fraction was mea- uated the prevalence of various traditional and non- sured using M-mode echocardiography to assess systolic function [20], traditional risk factors in a cohort of children with CKD and diastolic function was assessed by Doppler measuring the mitral inflow stage 3–5. Detailed echocardiography studies were per- e/a is the ratio between early (e; passive ventricular filling) and late (a; ac- formed in order to detect cardiac pathologic processes tive atrial contraction) diastolic flow velocities. A control group consisted of 27 children and young adults, aged 3–27years, who underwent echocar- and define their possible association with a number of diography for evaluation of an innocent murmur, with no abnormal struc- clinical and laboratory variables. Long-term clinical end- tural findings detected on the echocardiogram. points of vascular disease are not practical in children. We used, therefore, carotid ultrasound, an accepted sur- rogate method for evaluating various vasculopathies. It Carotid duplex examination included measuring carotid intimal–medial thickness Carotid duplex examination was performed by a registered vascular tech- nologist using Doppler ultrasound (Acuson Sequoia 512, Mountain View, (cIMT) and various measurements of the arterial biome- CA, USA) with a 6L3 multifrequency linear array transducer. The mea- chanical properties [15–17], and their correlation with sured variables were intimal–medial thickness and carotid diastolic and the clinical and laboratory variables. systolic diameter in a fixed point of the right common carotid artery, as previously described [21] with concomitant blood pressure measurement. Calculations of these measurements and how they are influenced by Methods changes in blood pressure determined the following parameters: distensi- bility (DC) = 2(ΔD/D)/(SBP−DBP), where D denotes diastolic diameter Patients and ΔD the change in artery diameter during systole. Stiffness (β) is de- Δ Seventy patients, aged 4months to 18years (27 <3years, 21 age 3≤ to fined as: (ln[SBP/DBP])/( D/D). The incremental modulus of elasticity <10, 22 age 10≤ to <18), from a single center, with estimated glomer- (Einc) is a marker of the intrinsic properties of the arterial wall material, ular filtration rate (GFR) of <60ml/min/1.73m2, were studied. Twenty independent of the arterial geometry [14]. It is calculated using the ratio π 2 three had end-stage renal disease (ESRD) treated with renal replacement of the lumen cross-sectional area (LCSA) = (D/2) and the wall cross- π 2−π 2 therapy—four with peritoneal dialysis and 19 with haemodialysis. Twen- sectional area (WCSA)= (D/2+cIMT) (D/2) : Einc =3(1+[LCSA/ ty six children were Jewish and 44 were Arabs. Patients' evaluation in- WCSA])/DC [22]. cluded the history of renal disease: age of onset, diagnosis, medications, the type of dialysis if needed, associated anomalies, known cardiac mal- formations or diseases, family history of CVS disease and active or en- Statistical analysis vironmental smoking. Physical examination was performed. Weight and Statistical analysis was performed using SPSS version 14 (SPSS Inc., height were recorded and body mass index (BMI) percentiles and Z Chicago IL). Parameters were normalized for age/gender/height as need- scores were calculated. Blood pressure was measured with an automated ed. Association between two continuous variables was assessed by ca- device at three consecutive clinic visits, and the average was calculated lculating the Pearson correlation coefficient or Spearman correlation and divided by the 95th percentile for the corresponding gender, age test for parametric and non-parametric values, respectively. Levene test and height percentile to determine the blood pressure index (BPI). Con- was used to define distribution width. For comparison of continuous vari- trolled hypertension was defined as BPI ≤1. Consent was given by pa- ables, the independent t-test was used when two groups were compared, tients or their parents. This study was approved by the Shaare Zedek and analysis of variance was employed when more than two groups were Medical Center ethics committee. compared. For abnormal, asymmetric distribution of non-parametric vari- ables, the Kruskal–Wallis test was used. Chi-square and Mann–Whitney tests were employed to compare groups of categorical parameters in large Laboratory data and small groups, respectively. Blood and urine samples were collected following an overnight fast, ex- Multiple stepwise linear regression analysis was performed to assess cept for water and regular medications. The following tests were per- potential predictors of left ventricular hypertrophy (LVH), diastolic dys- formed: serum electrolytes, glucose, lipid profile, homocysteine, function and arterial stiffening parameters. fibrinogen, C-reactive protein (CRP) and urine total protein (TP)/creat- inine ratio. For several parameters [calcium (Ca), phosphorous (Phos), uric acid, parathyroid hormone (PTH) levels and haemoglobin], a time-averaged level from the last 3years was calculated to assess the Results time-integrated burden instead of a single random value. The average for every quartile was initially recorded, followed by calculating the av- erage of all the time periods together. Patient characteristics and laboratory results Parameters such as serum haemoglobin and phosphate, in which the normal range vary with age and/or gender, were expressed as the number Patient characteristics are summarized in Table 1. There of standard deviations from the adjusted mean (Z score). This avoids the were no significant differences between groups of CKD inaccuracy of comparing raw data. stages. Cardiovascular risk factors, cardiac function and vascular disease in children with CRF 787 Table 1. Patient characteristics

CKD 3 CKD 4 CKD 5 Overall Variable (N = 30) (N = 17) (N = 23) (N = 70)

Age (years) Mean ± SD (range) 7.1 ± 5.7 (0.5–16.5) 9.5 ± 5.6 (0.3–17.5) 5.1 ± 4.3 (0.3–15) 7.0 ± 5.4 (0.3–17.5) Gender: Male 16 (53.3%) 11 (64.7%) 17 (73.9%) 44 (62.9%) Ethnic origin: Arab 18 (60%) 12 (70.6%) 14 (60.9%) 44 (62.9%) Jew 12 (40%) 5 (29.4%) 9 (39.1%) 26 (37.1%) Primary disease Dysplastic/obstructive 15 (45.7%) 5 (27.8%) 7 (30.4%) 27 (38.6%) Familial 7 (22.9%) 9 (50.0%) 2 (8.7%) 18 (25.7%) SRNSa 4 (14.3%) 0 (0%) 6 (26.1%) 10 (14.3%) Other 4 (17.1%) 3 (22.2%) 8 (34.8%) 15 (21.4%)

CRF years 3.42 ± 3.91 5.33 ± 3.57 2.16 ± 2.21 3.44 ± 3.51 Downloaded from https://academic.oup.com/ndt/article/25/3/785/1912566 by guest on 23 September 2021 Dialysis HD 19 (27.1%) PD 4 (5.7%) Dialysis vintage (years; mean±SD) HD 0.70 ± 2.48 PD 0.95 ± 2.45

a SRNS—steroid-resistant nephrotic syndrome. HD—haemodialysis, PD—peritoneal dialysis.

Table 2. Laboratory data according to CKD stages

CKD 3 CKD 4 CKD 5 Overall Laboratory variable N =30 N =17 N =23 P-valuea P-valueb N =70

Haemoglobin (time averaged, g/dl; mean±SD) 12.2 ± 1.5 11.6 ± 1.5 10.9 ± 0.9 NS 0.003 11.6 ± 1.3 Z score (mean±SD) −1.37 ± 1.61 −2.14 ± 3.42 −2.90 ± 1.99 NS 0.03 −2.06 ± 2.35 Anemia: number of patients with Z score <−2; n (%) 11 (36.7%) 12 (70.6%) 15 (65.2%) NS 0.03 38 (54.3%) PTH (time averaged, pg/ml; mean±SD) 148 ± 189 402 ± 314 467 ± 357 NS < 0.001 315 ± 317 Number of patients with PTH >88pg/ml; n (%) 20 (66.7%) 17 (100%) 21 (91.3%) 0.006 NS 58 (82.8%) Phosphorous (time averaged, mg/dl; mean±SD) 5.15 ± 0.56 5.01 ± 0.85 5.78 ± 1.22 0.02 NS 5.32 ± 0.94 Z score (mean±SD) 1.02 ± 1.85 1.31 ± 2.49 2.81 ± 4.29 NS 0.02 1.68 ± 3.07 Number of patients with Z score >2; n (%) 8 (26.7%) 6 (35.3%) 10 (43.5%) NS NS 24 (34.3%) Ca×P (time averaged, mg2/dl2; mean±SD) 47.5 ± 6.53 3 46.3 ± 9.48 3 53.5 ± 13.4 0.005 NS 49.2 ± 10.3 Number of patients with Ca×Phos >55; n (%) 3 (10.0%) 3 (17.6%) 8 (34.8%) 0.08 NS 14 (20.0%) Homocysteine μmol/l (mean±SD) 11.4 ± 16.2 10.3 ± 6.2 11.5 ± 8.9 NS NS 11.2 ± 12.0 Number of patients with Hcy >15μmol/l [n (%)] 5 (16.7%) 2 (11.7%) 5 (21.7%) NS NS 12 (17.1%) Uric acid (time averaged, mg/dl; mean±SD) 5.48 ± 1.38 6.52 ± 1.62 6.56 ± 1.21 NS 0.01 6.09 ± 1.47 Inflammatory state n (%) 12 (40.0%) 9 (52.9%) 14 (60.1%) NS NS 35 (50.0%) Proteinuria n (%) 26 (86.7%) 14 (82.3%) 15 (65.2%) NS NS 55 (78.6%) Average number of ;non-traditional risk factors 2.83 ± 1.42 3.70 ± 1.26 3.83 ± 1.34 NS 0.02 3.37 ± 1.42

Selected laboratory values in the different CKD stages; comparison between absolute levels, Z scores, where relevant, and percentage of patients with abnormal results. Time averaged, see text. NS—not significant. Ca×P—calcium phosphorous product. Hcy—homocysteine. a Between CKD 3 and either 4 or 5. b Between CKD 3 and 5.

It can almost exclusively be noted that wherever time- significantly increased in patients with CKD 5. Homocys- averaged and current laboratory variables were tested, ei- teine, inflammatory state (defined as either CRP >0.5mg/ ther only the time-averaged variables had significant corre- dl or fibrinogen >400mg/dl) and proteinuria [urine TP/cre- lations or they had better correlations than the current atinine >0.2 (mg/dl)/(mg/dl)] did not change significantly results. Only the time-averaged results and its statistical with stage of CKD. analysis are shown. Time-averaged haemoglobin levels and their age- and Only non-traditional risk factors accumulate with CKD gender-adjusted Z scores were significantly lower and stage. Risk factors for vascular disease were divided into anaemia (Z score <−2) was more prevalent among children traditional and non-traditional. The former (Table 3) in- with higher CKD stage (Table 2). Serum Phos levels with cluded positive family history, diabetes mellitus, smoking their respective Z scores, Ca×P product and the parathy- (either passive or active), hypertension and dyslipidaemia roid hormone levels were all higher and more prevalent (defined as high total serum cholesterol, increased LDL in advanced CKD stages. Uric acid concentrations were cholesterol or decreased HDL cholesterol; specific values 788 C. Rinat et al. Table 3. Traditional risk factors for cardiovascular disease in pediatric CKD patients

CKD 3 CKD 4 CKD 5 Overall Risk factor (N = 30) (N = 17) (N = 23)P-value (N = 70)

Family history of CVD 9 (30.0%) 4 (23.5%) 1 (4.3%) 0.04a 14 (20.0%) Smoking: Passive n (%) 8 (26.7%) 5 (29.4%) 8 (34.8%) 0.8 21 (30.0%) Active n (%) 1 (3.3%) 1 (5.9%) 0 (0%) 0.4 2 (6.3%) Hypertension Uncontrolled n (%) 9 (30.0%) 4 (23.5%) 17 (73.9%) 0.001a 30 (42.8%) SBPI (mean ± SD) 0.97 ± 0.18 0.91 ± 0.11 1.16 ± 0.23 <0.001a 1.01 ± 0.21 SBPI >1 [n (%)] 9 (30.0%) 3 (17.6%) 17 (73.9%) <0.001a 29 (41.4%) DBPI (mean ± SD) 0.86 ± 0.20 0.77 ± 0.17 1.12 ± 0.30 <0.001a 0.93 ± 0.27 DBPI >1 [n (%)] 6 (20.0%) 2 (11.8%) 15 (65.2%) <0.001a 23 (32.9%) Controlled hypertension 2 (6.7%) 4 (23.5%) 1 (4.3%) NS 7 (10.0%)

Diabetes 0 (0%) 1 (5.5%) 0 (0%) 0.1 1 (1.2%) Downloaded from https://academic.oup.com/ndt/article/25/3/785/1912566 by guest on 23 September 2021 Dyslipidaemia 21 (70.0%) 11 (64.7%) 19 (82.6%) 0.4 51 (72.9%) Cholesterol high 14 (46.7%) 6 (35.3%) 14 (60.9%) 0.3 34 (48.6%) LDL high 10 (35.7%) 5 (31.3%) 8 (38.1%) 0.8 23 (35.4%) HDL low 10 (33.3%) 7 (41.2%) 10 (43.5%) 0.7 27 (38.6%)

Average number of risk factors 1.67 ± 1.15 1.76 ± 1.03 2.00 ± 0.74 0.5 1.80 ± 1.00

LDL—low density lipoprotein cholesterol, HDL—high density lipoprotein cholesterol, NS—not significant. a Between CKD 5 and either CKD 3 or 4.

Table 4. Echocardiographic and carotid duplex data

CKD 3 CKD 4 CKD 5 Overall N =30 N =17 N =23 P-value N =70

Age (years) 7.1 ± 5.7 9.5 ± 5.6 5.1 ± 4.3 0.04a 7.0 ± 5.4 LVEDD index 0.82 ± 0.09 0.80 ± 0.09 0.82 ± 0.16 0.8 0.82 ± 0.12 LVMI (g/m2.7) 37.2 ± 23.8 32.5 ± 7.6 43.5 ± 13.2 0.2 38.2 ± 17.9 LVMI Z score 0.05 ± 2.95 −0.10 ± 0.75 0.96 ± 1.75 0.2 0.32 ± 2.22 Abnormal: N (%) 3 (10.0%) 1 (5.9%) 7 (30.4%) 0.07a 11 (15.7%) SF (%) 38.5 ± 5.5 37.5 ± 4.7 37.8 ± 4.9 0.8 38.0 ± 5.1 Abnormal: N (%) 1 (3.3%) 1 (5.9%) 3 (13.0%) 0.4 5 (7.1%) e/a 1.68 ± 0.49 1.87 ± 0.67 1.19 ± 0.38 0.001b 1.57 ± 0.57 Diastolic dysfunction: N (%) 0 (0%) 3 (17.6%) 10 (43.4%) 0.001b 13 (18.6%) IMT (mm) 0.39 ± 0.05 0.40 ± 0.06 0.43 ± 0.07 0.1 0.40 ± 0.06 Distensibility (kPa-1 ×10-3) 60.7 ± 27.1 58.6 ± 26.3 43.3 ± 11.5 0.09 55.6 ± 24.6 Stiffness 3.81 ± 2.01 4.13 ± 2.36 4.71 ± 2.11 0.5 4.13 ± 2.12 3 Einc (kPa × 10 ) 0.24 ± 0.13 0.26 ± 0.20 0.27 ± 0.11 0.8 0.25 ± 0.14

LVEDD—left ventricular end diastolic diameter, LVEDD index—(LVEDD/90th percentile of LVEDD for age), LVMI—left ventricular mass index = (LVM/height2.7), IVSD—interventricular septal diameter, PWD—posterior wall diameter, NS—not significant. e/a—see methods. a Between CKD 4 and 5. b Between both CKD 3 and 4 compared to CKD 5. vary with age [23]). Hypertension (controlled or uncon- CKD stages (2.83 ± 1.42 risk factors in CKD stage 3, trolled) was much more prevalent among CKD 5 pa- 3.70 ± 1.26 in CKD stage 4 and 3.83 ± 1.34 in CKD stage tients. All other risk factors, including dyslipidaemia, 5 patients; P = 0.02). were equally distributed among the three CKD stage groups. Similarly, there was no significant difference in Cardiac status. The two main findings identified were the mean number of risk factors per patient between LVH and diastolic dysfunction (15.7% and 18.6% of the these groups (1.67 ± 1.15 risk factors in CKD stage 3, patients, respectively; Table 4). Decreased systolic func- 1.76 ± 1.03 in CKD stage 4 and 2.00 ± 0.74 in CKD tion was detected in 7.1% of the patients. stage 5 patients; P = 0.5). Non-traditional risk factors included inflammatory state, LVH is associated with systolic BPI. Patients with LVH hyperphosphataemia, Ca×P product >55mg2/dl2,hyper- had higher systolic and diastolic BPIs compared to those parathyroidism (iPTH >88pg/ml), hyperhomocysteinaemia without LVH (SBPI 1.22 ± 0.25 vs 0.98 ± 0.18, P < 0.001 (>15μmol/l) and the presence of proteinuria or anaemia and DBPI 1.14 ± 0.28 vs 0.89 ± 0.25, P < 0.003, respective- (Table 2). Overall, there was a significant increase in the ly). LVH was more likely to be detected in patients with ar- mean number of these risk factors per patient with higher teriovenous (AV) fistula (100% vs 13.2%; P < 0.001). No Cardiovascular risk factors, cardiac function and vascular disease in children with CRF 789

A B Diastolic dysfunction and blood pressure Diastolic dysfunction in CKD stages index 50 1.6 p<0.0001 1.4 p<0.05 p<0.05

1.2 25 1 dysfunction

% with diastolic 0.8 Blood pressure index 0 0.6 345 Systolic Diastolic

CKD stage Downloaded from https://academic.oup.com/ndt/article/25/3/785/1912566 by guest on 23 September 2021

C Diastolic dysfunction and haemoglobin levels D Diastolic dysfunction and PTH levels 13.5 1000

NS p<0.005 750 12 NS p=0.005 500 10.5 PTH (pg/ml) 250

Haemoglobin levels (gr/dl) 9 0 Current Time averaged Current Time averaged Fig. 1. Diastolic dysfunction (DD) in paediatric CKD patients (black- DD present, stripes- DD absent). None of the CKD 3 patients had DD, but it was prevalent CKD 5 patients (A). DD is associated with both high SBPI and DBPI (B). Patients with DD have lower time-averaged but not current haemoglobin levels (C). Patients with DD have higher time-averaged but not current parathyroid levels (D). Both represent the importance of calculating the time-averaged rather than only the current values. statistically significant differences between those with or tolic BPI, inflammatory state and time-averaged haemo- without LVH were noted with respect to serum PTH levels, globin Z score (P < 0.05 for all). Ca×P product, age or CKD stage. Logistic regression anal- ysis showed that only systolic BPI correlated significantly Systolic dysfunction is associated with SBPI, DBPI and with LVH (P = 0.05). time-averaged anaemia. Systolic dysfunction was identi- fied in only five patients (7.1%; Table 4). Time-averaged Diastolic dysfunction is associated with SBPI, the presence haemoglobin levels and Z scores were significantly lower of time-integrated anaemia and inflammatory state. in patients with systolic dysfunction (10.2 ± 1.13 vs 11.7 Diastolic dysfunction (DD) increased in prevalence with ± 1.29g/dl, P <0.05and−4.40 ± 1.91 vs −1.88 ± 2.29, progression of kidney disease. Whereas none of the chil- P < 0.05, respectively). They also had higher SBPI and dren in CKD 3 group had DD, it was detected in 17.6% of DBPI (1.37 ± 0.33 vs 0.99 ± 0.17, P < 0.005 and 1.30 ± CKD 4 patients and in 43.4% of the CKD 5 group (P < 0.45 vs 0.90 ± 0.23, P < 0.005, respectively). 0.0001; Figure 1A). Patients with diastolic dysfunction had on average higher BPIs than those with normal dia- stolic function (SBPI 1.20 ± 0.30 vs 0.98 ± 0.16, P < Vascular structure and function 0.05; DBPI 1.15 ± 0.40 vs 0.87 ± 0.20, P < 0.05; Figure 1B). Lower time-averaged haemoglobin levels (Figure cIMT is not correlated with traditional risk factors but is 1C) and Z scores (10.5 ± 0.86 vs 11.8 ± 1.30g/dl, P < associated with Ca–P-related parameters. In this cohort 0.005 and −3.52 ± 2.02 vs. −1.72 ± 2.30, P =0.01,re- of patients, cIMT was overall found to be within normal spectively) were detected among children with diastolic range for age (97th percentile: 0.46mm at age 10years, dysfunction. An inflammatory state was also more com- 0.49mm at 20years; [24]). It did correlate, however, with mon among patients with DD (92% vs 40.4%; P < the number of years in ESRD (r = 0.316; P = 0.02) but 0.001). In addition, time-averaged PTH levels where no association was seen with any of the traditional athero- higher in patients with DD (532 ± 382pg/ml vs 265 ± sclerosis or non-traditional risk factors, nor with echocar- 261pg/ml; P < 0.05; Figure 1D). Average patients' age diographic findings. We found a tendency for thicker was similar in these two groups. Backward stepwise lo- cIMT in CKD 5 patients (0.43mm ± 0.05mm) compared gistic regression showed that the following parameters to patients in CKD 4 (0.40mm ± 0.06mm) and 3 (0.39 significantly correlated with diastolic dysfunction: sys- mm ± 0.05mm). 790 C. Rinat et al. A Distensibility and time averaged uric acid B levels Einc and time averaged Uric acid levels 150.00 0.90 r= -0.378 r=0.353 ) 3 100.00 0.60 x 10-3) 50.00 0.30 Einc (kPa x 10 Distensibility (kPa-1 0.00 0.00 2.0 4.0 6.0 8.0 10.0 2.0 4.0 6.0 8.0 Uric acid (mg/dl) Uric acid (mg/dl) Downloaded from https://academic.oup.com/ndt/article/25/3/785/1912566 by guest on 23 September 2021

Fig. 2. Time-averaged uric acid levels significantly correlated with distensibility (A) and Einc (B).

Table 5. Analysis of covariance for Einc and distensibility Discussion

Dependent variable Variable β P-value This is the first study on various CVS manifestations in

2 CKD involving very young patients and, to the best of Einc: r = 0.352 Homocysteine 0.247 0.05 our knowledge, the first time the role of uric acid as a risk Uric acid 0.259 0.05 Phos Z score 0.261 0.05 factor was investigated. In this study, we show that only Distensibility: r2 = 0.353 Homocysteine −0.252 0.05 non-traditional risk factors for vascular disease increase Uric acid −0.250 0.05 in number and severity with progression of kidney disease. PTH −0.296 0.05 High SBPI was significantly associated with worsening of all echocardiographic parameters. Low time-averaged hae- moglobin levels were associated with both diastolic and Arterial stiffening parameters correlate with some Ca–P systolic cardiac dysfunction, whereas inflammatory state metabolism-related variables. Various parameters descri- is associated with diastolic dysfunction only. cIMT was bing arterial stiffening were analyzed. Time-averaged se- only associated with the duration in ESRD. rum PTH concentrations correlated with decreased arterial Several parameters describing arterial stiffness were as- distensibility and with increased stiffness (r = −0.353, P = sessed with respect to potential risk factors. Hyperhomocys- 0.01 and r = 0.290, P = 0.03, respectively). Time-averaged teinaemia, time-averaged PTH and uric acid levels phosphorus Z score correlated with Einc (r = 0.297, P = significantly correlated with distensibility. Time-averaged 0.04). Other Ca–P-related parameters were not significantly PTH was also associated with arterial stiffness. Serum correlated. homocysteine concentrations, time-averaged uric acid and phosphorous Z scores were found to correlate significantly Uric acid, homocysteine levels and the presence of AV with Einc. fistula are correlated to arterial stiffening. Significant Vascular disease should be divided into two separate correlations were found between arterial stiffness and disease processes: intimal atherosclerosis and medial arter- time-averaged uric acid levels (distensibility: r = −0.378, iosclerosis. These two clinical entities differ with respect to P = 0.005; Einc: r = 0.353, P = 0.01; Figure 2A–B) and risk factors, pathophysiology, histological findings [25] serum homocysteine concentrations (distensibility: r = and clinical manifestations. Classical atherosclerosis is −0.267, P = 0.05; Einc 0.350, P = 0.01). caused by intimal plaque formation, secondary to tradition- Parameters of vascular function did not correlate with any al vascular disease risk factors. The clinical manifestations of the following: age, anaemia, blood pressure variables are due to alterations in the conduit function of the arteries. (SBPI, DBPI or pulse pressure), inflammatory state, eGFR, On the other hand, medial arteriosclerosis is caused by dif- duration of CRF or ESRD, total, HDL or LDL cholesterol. fuse mineral deposition in the tunica media of the arterial Similarly, no significant correlation was found between wall, as a result of high calcium–phosphate product, sup- vascular function and echocardiographic structural (e.g. pression of natural crystallization inhibitors [including ma- LVH) or functional (e.g. diastolic dysfunction) parameters. trix Gla protein (MGP), osteoprotegerin (OPG) and fetuin Analysis of covariance pointed at serum homocys- A] and vascular smooth muscle cell phenotypic changes teine levels, time-averaged uric acid and PTH levels leading to osteoblastic differentiation [26,27]. Together as significant independent variables which affect vascu- they create a permissive environment for nucleation of lar distensibility (all P < 0.05; r2 = 0.353; Table 5). Only Ca–P crystals. The known risk factors, in addition to time-averaged PTH levels were independently and signif- the Ca–P-related parameters, are cumulative doses of Ca icantly correlated with stiffness, whereas homocysteine containing Phos binders and vitamin D analogs. Clinically, levels, time-averaged uric acid and time-averaged phos- arteriosclerosis causes vascular stiffness and secondarily phorous Z score were determined as independent factors results in hypertension, increased pulse pressure and 2 affecting Einc (P < 0.05 for all; r = 0.352; Table 5). LVH [26]. Cardiovascular risk factors, cardiac function and vascular disease in children with CRF 791 The major factors leading to myocardial disease include that, in young children <1m in height, indexing the LVM volume overload, anaemia and the uremic milieu per se. Im- by dividing it by the height to the power of 2.7 may cause portant components of the latter are the endogenous cardio- artifactually high values. This was corrected in our study tonic steroids, digitalis-like substances whose secretion is by using age-adjusted LVMI normal values [19]. augmented in CRF patients as an adaptation to the uraemic We found homocysteine levels to correlate with vascular electrolyte–water imbalance [28–30]. Their action results in distensibility and Einc but not with cIMT. Serum homocys- LVH, myocardial fibrosis and diastolic dysfunction. teine levels were previously found to correlate with arterial In children with CKD, vascular disease rarely reaches stiffening in both the general population [37] and in haemo- clinical manifestations. On the other hand, myocardial dis- dialysis adult patients [38], and with coronary calcifications ease can cause symptomatic diastolic and/or systolic dys- in young adults with childhood onset CRF [39]. It remains function. When cardiac death occurs, it is rarely caused by controversial whether there is a direct influence on cardio- atherosclerosis or arteriosclerosis but rather by congenital vascular disease. Several trials failed to show that using cardiac anomalies or secondary to electrolyte imbalance, homocysteine-lowering agents reduces the risk for clinical

hypertensive crisis or fluid overload. A comprehensive CVS disease, even in CKD patients [40]. Other studies were Downloaded from https://academic.oup.com/ndt/article/25/3/785/1912566 by guest on 23 September 2021 study [6] pointed to cardiovascular-related diseases as the aimed at testing the hypothesis that lowering homocysteine main cause of death (overall 41%) in a cohort of patients levels would improve endothelial dysfunction in the general with an early onset of ESRD (0–14years of age). The list population and in CKD patients (both adults and pediatric), of aetiologies included cerebrovascular events, congestive but the results were not consistent [41–43]. heart failure, cardiac arrest and dissection of the aorta— Since classical atherosclerosis and arteriosclerosis are all of them, at least in part, are consequences of hyperten- different disease processes, one can argue that the effect sion, electrolyte anomalies and volume overload rather than of homocysteine is more on the arterial media, contributing secondary to vascular or myocardial disease per se. Never- to arteriosclerosis (and secondarily to arterial stiffness) and theless, three of the patients died of myocardial infarction at not to intimal atherosclerosis. This might solve the paradox a very young age (24–36years old). The high death rate de- between the consistent finding of positive correlation be- clined by 50% from the decade of 1972–1981 to 1982– tween arterial stiffness and hyperhomocysteinaemia and 1992, and the CVS mortality declined even further by 61%. the absence of a favorable effect of lowering homocysteine Overall, the cIMT was within the normal range in the levels on ischaemic heart disease or stroke. The absence of present study, although the average cIMT in CKD stage 5 obvious improvement in parameters of endothelial function (0.43 ± 0.05mm) was higher than the published normal following homocysteine lowering could potentially reflect mean values (0.39 ± 0.05mm and 0.40 ± 0.05mm at age irreversible damage or long-term effect of hyperhomocys- 10 and 20years, respectively [24]). Previous studies [31– teinaemia to the endothelium. If this is the case, treatment 33] demonstrated increased cIMT in paediatric CKD pa- can be still justified to avoid further damage. tients, especially in those receiving renal replacement ther- We have demonstrated good and significant correlations apy. The difference between our results and those described between time-averaged serum uric acid levels and both de- in previous studies may stem from the fact that we included creased distensibility and increased Einc. Hyperuricaemia children in CKD 3–5 rather than only those with ESRD or has many emerging deleterious effects; in children, it from dissimilarities in age groups. Our patients were signif- was found to be related to primary hypertension [44] and icantly younger (on average 7.0years compared with ~15 was suggested as having a role in its pathogenesis. In ad- years), and since cIMT increases with age [24], this proba- dition, since hyperuricaemia is strongly associated with bly impacts on the mean values for the entire cohort. pre-eclampsia, it was assumed that it is not merely an as- Lack of published normal values for cIMT during the sociation by chance but rather uric acid has a pathogenic first decade of life precluded Z scoring in this part of role in the development of hypertension and kidney disease the study (as was done by Litwin et al. [31]), and may have in this context [45]. A large epidemiological study conclud- compromised the interpretation of the results. ed that elevated uric acid levels increases the risk for new Of note, since cIMT measures both intima and media, it onset kidney disease, independent of eGFR, components reflects not only intimal atherosclerosis but also medial ar- of the metabolic syndrome, gender, age and antihyperten- teriosclerosis or other causes of medial thickening. In pedi- sive drugs [46]. Also, our findings are consistent with pre- atric CKD patients, when atherosclerosis is in its very early vious studies pointing to the deleterious effect of uric acid stages, cIMT seems to be more a marker of arteriosclerosis. on endothelial function and arterial stiffness, even when The main cardiac abnormalities detected in our study uric acid levels are within the normal range [47,48]. Mech- were LVH and diastolic dysfunction, with prevalence com- anistically, experimental animal models have suggested parable to that of previous publications. LVH was found to that high uric acid levels may induce primary hyperten- correlate with systolic and diastolic hypertension and with sion, probably by causing renal afferent arteriolopathy the presence of an AV fistula. Other studies have pointed at [49]. Another possible mechanism for vascular damage hypertension, anaemia and parameters associated with Ca– is through increased production of reactive oxygen species P metabolism as affecting LVH in patients with CKD. In and a decrease in the potent vasodilator nitric oxide [50]. the paediatric population, Mitsnefes et al. found LVH to Treatment of patients with allopurinol improved endothelial correlate with factors related to Ca–P metabolism and with dysfunction in both congestive heart failure and in type 2 haemoglobin levels and hypertension [34,35]. Matteucci et diabetes mellitus [51,52]. These data point to possible direct al. found anaemia, low GFR, high BMI and young age as deleterious effects of hyperuricaemia on arteries and may independent correlates with LVMI [36]. It can be argued provide explanation to our findings. 792 C. Rinat et al. Current indications for lowering uric acid with allopuri- sis, atherosclerosis and myocardial disease—with different nol are limited. It is widely accepted that patients with ur- risk factors, which together have an impact on morbidity icosuria, regardless of the blood uric acid levels, will and mortality. Studies should be undertaken with this con- benefit from such treatment to prevent nephrolithiasis or cept in mind to avoid misinterpretation of their results. nephrocalcinosis. On the other hand, asymptomatic pa- These disease processes start already in the first decade of tients with isolated hyperuricaemia are often not treated as life, from CKD stages 3 and on. Therapeutic measures di- they are at a very low risk for gout or for renal disease. The rected at risk factor reduction have to be intensively taken. risk of hyperuricaemia for CVS disease is not well estab- In this regard, controlling blood pressure and avoidance of lished, and frequently it is only regarded as a component anaemia are obvious, but other measures must be consid- of the metabolic syndrome [53]. Since arterial stiffening is ered. Guidelines concerning the optimal Ca–P level in chil- strongly associated with cardiovascular morbidity and mor- dren with CKD should be defined and consideration should tality [54], any factor directly causing arterial stiffness be given to the dilemma whether hyperuricaemia and hyper- should be considered as a potential target for treatment. homocysteinaemia should be treated. Further studies are –

Parameters related to calcium phosphorous metabolism needed to explore the long-term effects of these agents on Downloaded from https://academic.oup.com/ndt/article/25/3/785/1912566 by guest on 23 September 2021 have been shown to have an impact on arterial stiffening arterial stiffness. which is confirmatory of previous observations [34,35, 39]. Phosphor and calcium reference values are higher in Acknowledgements. This study was supported by the Mirsky Fund, younger ages [23]. Having Ca×P product above the re- Shaare Zedek Medical Center. commended level (>55mg2/dl2) often occurs with normal Ca/P concentration range for age. The physiology of this Conflict of interest statement. None declared. phenomenon is not known. Theoretically, higher concen- trations of the crystallization inhibitors at these ages could References have been an adequate explanation, but apparently young children have lower concentrations of fetuin A and OPG 1. McDonald SP, Craig JC. Long-term survival of children with end- (but not MGP; [55]). Better understanding is needed so ap- stage renal disease. N Engl J Med 2004; 350: 2654–2662 propriate guidelines can be established for this age group. 2. Mitsnefes MM. Pediatric end stage renal disease: heart as a target. J Pediatr 2002; 141: 162–164 In this study, we used several means to ensure gender, 3. Foley RN, Parfrey PS, Sarnak MJ. Clinical epidemiology of cardiovas- age and height corrections for variables, including Z scor- cular disease in chronic renal disease. Am J Kidney Dis 1998; 32: ing of laboratory and echocardiographic results, correction S112–S119 of LVMI for children <1m in height and calculating time- 4. Levey AS, Beto JA, Coronado BE et al. Controlling the epidemic of averaged values. This proved to be effective since stratify- cardiovascular disease in chronic renal disease: What do we know? ing the patients by age did not significantly change the da- What do we need to learn? Where do we go from here? Am J Kidney Dis 1998; 32: 853–906 ta analysis results. Although the use of time-averaged 5. Groothoff JW, Lilien MR, van de Kar MCAJ et al. Cardiovascular values for various laboratory variables was previously im- disease as a late complication of end-stage renal disease in children. plemented in a few studies [15,31], it is not yet a common Pediatr Nephrol 2005; 20: 374–379 practice. We believe this approach improves the accuracy 6. Groothoff JW, Gruppen MP, Offringa M et al. Mortality and causes of of the comparisons and provides better understanding of death of end-stage renal disease in children: a Dutch cohort study. – the pathological processes. Kidney Int 2002; 61: 621 629 7. Berenson JF, Srinivasan SR, Bao W et al. Association between mul- In the very young group, we encounter specific problems tiple cardiovascular risk factors and atherosclerosis in children and in achieving recommended therapeutic goals: hypertension young adults. N Engl J Med 1998; 338: 1650–1656 is more difficult to control—it was found in 42.8% of the 8. Li S, Chen W, Srinvasan S et al. Childhood cardiovascular risk fac- entire group, but was much more prevalent in the age group tors and carotid vascular changes in adulthood. The Bogalusa heart of 0.4–3years (66.7%) compared to 30.2% in the age group study. JAMA 2003; 290: 2271–2276 – 9. Raitakari O, Juonala M, Kähönen M et al. Cardiovascular risk factors in of 3 18years. This might stem from lower BP limits in – younger age, dependence on liquid feeding formulation, childhood and carotid artery intima media thickness in adulthood. The cardiovascular risk in young Finns study. JAMA 2003; 290: 2277–2283 which puts the patient at risk of chronic volume overload, 10. Goodman WG, Goldin J, Kuizon BD et al. Coronary artery calcifica- and the extreme burden of the treatment in general on the tions in young adults with end stage renal disease who are undergoing patients' parents that may result in inadequate compliance. dialysis. N Engl J Med 2000; 342: 1478–1483 In addition, statin use is limited to children >8years of age, 11. Becker-Cohen R, Nir A, Rinat C et al. Risk factors for cardiovascular thus there are no effective tools to combat hypercholestero- disease in children and young adults after renal transplantation. Clin J – laemia at lower age, although lowering cholesterol levels Am Soc Nephrol 2006; 1: 1284 1292 12. Cardiovascular risk reduction in high-risk pediatric patients: a scien- was not shown to be effective in reducing CVS events or tific statement from the American Heart Association Expert Panel on mortality in adult haemodialysis patients [56,57]. Population and Prevention Science; the Councils on Cardiovascular Limitations of this study include the following: this is a Disease in the Young, Epidemiology and Prevention, Nutrition, Phys- cross-sectional and single-centered study, and some of the ical Activity and Metabolism, High Blood Pressure Research, Car- patients had short follow-up. For all vascular measurement diovascular Nursing, and the Kidney in Heart Disease; and the variables, there are no published normal values, so adjust- Interdisciplinary Working Group on Quality of Care and Outcomes Research: endorsed by the American Academy of Pediatrics. Circu- ment for age was impossible. In addition, only 53 of 70 lation 2006; 114: 2710–2738 (75.7%) patients had carotid artery duplex examination. 13. Mitsnefes MM, Kimbal TR, Witt SA et al. Left ventricular mass and In summary, CVS disease in CKD patients is a combina- systolic function in pediatric patients with chronic renal failure. Cir- tion of three interrelated disease processes—arteriosclero- culation 2003; 107: 864–868 Cardiovascular risk factors, cardiac function and vascular disease in children with CRF 793 14. Mitsnefes MM, Daniels SR, Schwartz SM et al. Changes in left ven- 37. Mayer O, Filipovsky J, Doljesová M et al. Mild hyperhomocysteine- tricular mass in children and adolescents during dialysis. Pediatr Ne- mia is associated with increased aortic stiffness in general population. phrol 2001; 16: 318–323 J Hum Hypertens 2006; 20: 267–271 15. O'Leary DH, Polak FJ, Kronmal RA et al. Carotid-artery intima and 38. Jer-Chia T, Hung Tien K, Yi-Wen C et al. Correlation of plasma media thickness as a risk factor for myocardial infarction and stroke homocysteine level with arterial stiffness and pulse pressure in hemo- in older adults. N Engl J Med 1999; 340: 14–22 dialysis patients. Atherosclerosis 2005; 182: 121–127 16. Blacher J, Guerin AP, Pannier B et al. Arterial calcifications, arterial 39. Oh J, Wunsch R, Turzer M. Advanced coronary and carotid arterio- stiffness, and cardiovascular risk in end stage renal disease. Hyper- pathy in young adults with childhood-onset chronic renal failure. Cir- tension 2001; 38: 938–942 culation 2002; 106: 100–105 17. Oh J, Wunsch R, Turzer M et al. Advanced coronary and carotid ar- 40. Bonaa KH, Njolstad I, Ueland PM et al. Homocysteine lowering and teriopathy in young adults with childhood-onset chronic renal failure. cardiovascular events after acute myocardial infarction. N Engl J Med Circulation 2002; 106: 100–105 2006; 354: 1578–1588 18. De Simone G, Daniels SR, Devereux RB et al. Left ventricular mass 41. van Guldener C, Janssen MJFM, Lambert J et al. No change in im- and body size in normotensive children and adults: assessment of al- paired endothelial function after long term folic acid therapy of hy- lometric relations and impact of overweight. J Am Coll Cardiol 1992; perhomocysteinemia in haemodialysis patients. Nephrol Dial 20: 1251–1260 Transplant 1998; 13: 106–112 19. Khoury PR DS, Gidding SS, Kimball TR. Left ventricular mass in- 42. Title LM, Cummings PM, Giddens K et al. Effect of folic acid and Downloaded from https://academic.oup.com/ndt/article/25/3/785/1912566 by guest on 23 September 2021 dex in children: what is the right index? Poster presented at echo antioxidant vitamins on endothelial dysfunction in patients with cor- meeting in San Diego CA. Am Soc Echo 2004; 555 onary artery disease. J Am Coll Cardiol 2000; 36: 758–765 20. Colan SD, Parness IA, Spevak PJ et al. Developmental modulation of 43. Bennet-Richards K, Kattenhorn M, Donald A et al. Does folic acid myocardial mechanics: age and growth related alterations in afterload lower total homocysteine levels and improve endothelial function in and contractility. J Am Coll Cardiol 1992; 19: 619–629 children with chronic renal failure? Circulation 2002; 105: 1810– 21. Sorof JM, Alexandrov AV, Garami Z et al. Carotid ultrasonography 1815 for detection of vascular abnormalities in hypertensive children. Pe- 44. Feig DI, Johnson RJ. Hyperuricemia in childhood primary hyperten- diatr Nephrol 2003; 18: 1020–1024 sion. Hypertension 2003; 42: 247–252 22. Groothoff JW, Gruppen MP, Offringa M et al. Increased arterial stiff- 45. Kang DH, Finch J, Nakagawa T. Uric acid, endothelial dysfunction ness in young adults with end stage renal disease since childhood. J and pre-eclampsia: searching for a pathogenic link. J Hypertension Am Soc Nephrol 2002; 13: 2953–2961 2004; 22: 229–235 23. Custer JW, Rau RE. Custer JW, Rau RE. Blood chemistries and body 46. Obermayr RP, Temml C, Gutjahr G et al. Elevated uric acid increases fluids. In: JW Custer, RE Rau (eds). The Harriet Lane handbook. the risk for kidney disease. J Am Soc Neph 2008; 19: 2407–2413 (18th ed). Philadelphia, PA: Elsevier Mosby, 2005: 677–688 47. Ishizaka N, Ishizaka Y, Toda EI et al. Higher uric acid is associated 24. Jourdan C, Wühl E, Litwin M et al. Normative values for intima– with increased arterial stiffness in Japanese individuals. Atherosclero- media thickness and distensibility of large arteries in healthy adoles- sis 2007; 192: 131–137 cents. J Hypertens 2005; 23: 1707–1715 48. Erdogan D, Gullu H, Caliskan M et al. Relation of serum uric acid to 25. Gross ML, Meyer HP, Ziebart H et al. Calcification of coronary in- measures of endothelial function and atherosclerosis in healthy tima and media: immunohistochemistry, backscatter imaging, and X- adults. Int J Clin Pract 2005; 59: 1276–1282 ray analysis in renal and non-renal patients. Clin J Am Soc Nephrol 49. Mazzali M, Kanellis J, Han L et al. Hyperuricemia induces a primary 2006; 2: 121–134 renal arteriolopathy in rats by a blood pressure-independent mecha- 26. London GM, Marchais SJ, Mtivier F et al. Cardiovascular risk in end nism. Am J Physiol Renal Physiol 2002; 282: F991–F997 stage renal disease: vascular aspects. Nephrol Dial Transplant 2000; 50. Khosla UM, Zharikov S, Finch JL et al. Hyperuricemia induces en- 15: 97–104 dothelial dysfunction. Kidney Int 2005; 67: 1739–1742 27. Shanahan CM. Vascular calcification—a matter of damage limita- 51. Farquharson CA, Butler R, Hill A et al. Allopurinol improves endo- tion? Nephrol Dial Transplant 2006; 21: 1166–1169 thelial dysfunction in chronic heart failure. Circulation 2002; 106: 28. Kennedy DJ, Vetteh S, Periyasamy SM et al. Central role of the car- 221–226 diotonic steroid marinobufagenin in the pathogenesis of experimental 52. Butler R, Morris AD, Belch JJ et al. Allopurinol normalizes endothe- uremic cardiomyopathy. Hypertension 2006; 47: 488–495 lial dysfunction in type 2 diabetes with mild hypertension. Hyperten- 29. Stelia P, Manunta P, Mallamci F et al. Endogenous ouabain and car- sion 2000; 35: 746–751 diomyopathy in dialysis patients. J Intern Med 2008; 263: 274–280 53. Yu ASL, Brenner BM. Fauci AS, Braunwald E, Kasper DL, Hauser 30. Schoner W, Scheiner-Bobis G. Role of endogenous cardiotonic ster- SL, Longo DL, Jameson JL, Loscalzo J. Tubulointerstitial diseases of oids in sodium hemostasis. Nephrol Dial Transplant 2008; 23: 2723– the kidney, and Shumacher HR, Chen LX. Gout and other crystal 2729 associated arthropathies. In: AS Fauci, E Braunwald, DL Kasper, 31. Litwin M, Wűhl E, Jourdan C et al. Altered morphologic properties SL Hauser, DL Longo, JL Jameson, J Loscalzo (eds). Harrison's of large arteries in children with chronic renal failure and after renal principles of internal medicine (17th ed). New York NY: McGraw transplantation. J Am Soc Nephrol 2005; 16: 1494–1500 Hill, 2005: 1806–1809, 2165–2167 32. Mitsnefes MM, Kimbal TR, Witt SA et al. Abnormal carotid artery 54. Pannier B, Guérin AP, Marchais SJ et al. Stiffness of capacitive and structure and function in children and adolescents with successful re- conduit arteries: prognostic significance for end stage renal disease nal transplantation. Circulation 2004; 110: 97–101 patients. Hypertension 2005; 45: 592–596 33. Shroff RC, Donald AD, Hiorns MP et al. Mineral metabolism and 55. Shroff RC, Shah V, Hiorns MO et al. The circulating calcification vascular damage in children on dialysis. J Am Soc Nephrol 2007; inhibitors, fetuin-A and osteoprotegerin, but not matrix Gla protein, 18: 2996–3003 are associated with vascular stiffness and calcification in children on 34. Mitsnefes MM, Kimbal TR, Kartal J et al. Cardiac and vascular ad- dialysis. Nephrol Dial Transplant 2008; 23: 3263–3271 aptation in pediatric patients with chronic kidney disease: role of Ca– 56. Wanner C, Krane V,März Wet al. Atorvastatin in patients with type 2 P metabolism. J Am Soc Nephrol 2005; 16: 2796–2803 diabetes mellitus undergoing hemodialysis. N Eng J Med 2005; 353: 35. Mitsnefes MM, Kimbal TR, Kartal J et al. Progression of left ventric- 238–248 ular hypertrophy in children with early chronic kidney disease: 2year 57. Fellström BC, Jardine AG, Schmieder RE et al. Rosuvastatin and car- follow-up study. J Pediatr 2006; 149: 671–375 diovascular events in patients undergoing hemodialysis. N Eng J Med 36. Matteucci MC, Wühl E, Picca S et al. Left ventricular geometry in 2009; 360: 1395–407 children with mild to moderate chronic renal insufficiency. J Am Soc Neph 2006; 17: 218–226 Received for publication: 1.3.09; Accepted in revised form: 30.9.09