Cardiac disease in chronic uremia: epidemiology

Differences in peripheral microcirculatory blood flow regulation in chronic kidney disease based on wavelet analysis of resting near-infrared spectroscopy

Vascular impairment is closely related to increased mortality in chronic kidney disease (CKD). The objective of this study was to assess impairments in the regulation of peripheral microvascular perfusion in patients with CKD based on time-frequency spectral analysis of resting near-infrared spectroscopy (NIRS) signals. Total hemoglobin (tHb) concentration and tissue saturation index (TSI) signals were collected using NIRS for a continuous 5 mins at 10 Hz from the forearm of 55 participants (34 CKD including 5 with end-stage renal disease, and 21 age-matched control). Continuous wavelet transform-based spectral analysis was used to quantify the spectral amplitude within five pre-defined frequency intervals (I, 0.0095-0.021 Hz; II, 0.021-0.052 Hz; III, 0.052-0.145 Hz; IV, 0.145-0.6 Hz and V, 0.6-2.0 Hz), representing endothelial, neurogenic, myogenic, respiratory and heartbeat activity, respectively. CKD patients showed lower tHb average spectral amplitude within the neurogenic frequency interval compared with controls (p = 0.014), consistent with an increased sympathetic outflow observed in CKD. CKD patients also showed lower TSI average spectral amplitude within the endothelial frequency interval compared with controls (p = 0.046), consistent with a reduced endothelial function in CKD. These findings demonstrate the potential of wavelet analysis of NIRS to provide complementary information on peripheral microvascular regulation in CKD.

Pulmonary Hypertension in Patients Starting Peritoneal Dialysis

BACKGROUND

Cardiovascular complications are the major cause of morbidity and mortality in patients with chronic kidney disease (CKD). One such complication is pulmonary hypertension (PH). Its prevalence in patients in peritoneal dialysis (PD) varies from 12.6-41.7% and its related factors are not well known. The main objective of this multicenter study was to determine the prevalence of PH and its risk factors in patients starting in PD.

METHODS

Patients incident in PD were studied. Clinical, biochemical, and PD parameters were evaluated. A transthoracic echocardiography was performed and the evaluated according to the American Society of Echocardiography. Systolic pulmonary artery pressure (sPAP) was calculated with tricuspid regurgitation gradient and PH considered if pulmonary artery pressure was ≥35 mmHg.

RESULTS

There were 105 men and 72 women included in the study (aged 53.7 ± 12.8 vs. 52.9 ± 15.5 years). PH was found in 69 patients (38.98%), they had sPAP of 49.05 ± 13.80 vs. 18.81 ± 11.15 mmg, in patients without PH (p <0.001). Patients with PH tend to be more frequently men than women (42 vs. 35%, p = 0.33), and were younger (51.0 ± 14.9 vs. 55,1 ± 12.8 years; p = 0.05). Risk factor for PH were diastolic dysfunction of the left ventricle (LV) (OR = 1.46, 95% CI 1.094-1.973), left ventricular hypertrophy (LVF) (OR = 2.56, 95% CI 1.29-5.09); and residual renal function (RRF) was a protector factor (OR = 0.78, 95% CI 0.068-0.915).

CONCLUSIONS

Prevalence of PH in patient's incident in PD was 38%. The factors associated with PH were diastolic dysfunction of the LV and LV hypertrophy. RRF was a protector factor.

Low Calcium Dialysate Increases Cardiac Relaxation in CAPD Patients

Objective

To establish whether changes in serum calcium affect left ventricular (LV) function in continuous ambulatory peritoneal dialysis (CAPD) patients.

Methods

This study was conducted on 28 clinically stable CAPD patients (11 females, 17 males). Left ventricular relaxation and systolic function were echocardiographically examined in all patients during standard dialysate (containing 1.75 mmol/L calcium) treatment. All patients were then changed to low calcium dialysate (1.25 mmol/L calcium) for 1 month and all patients were re-examined echocardiographically. Decrement in isovolumic relaxation time (IVRT) and deceleration time (DT), and increment in the ratio of peak early to peak late diastolic velocities (E/Amax) were admitted as indexes showing improvement in LV relaxation. 17 age- and sex-matched controls were also echocardiographically examined.

Results

Deceleration time, interventricular septal thickness at systole (IVSTS) and diastole (IVSTD), and posterior wall thickness at systole (PWS) and diastole (PWD) were higher in CAPD patients using standard dialysate than in normal controls. With the use of low calcium dialysate, DTs were similar but IVSTS, IVSTD, PWS, and PWD values remained higher. In normal controls, E/Amax values were higher than those in CAPD patients using standard dialysate ( p < 0.001) and low calcium dialysate ( p = 0.009). Serum intact parathyroid hormone level, weight, clinical volume status, and blood pressure were similar throughout the study period. Serum ionized calcium levels were decreased significantly during low calcium dialysate treatment. The changes in IVRT, DT, and E/Amax suggest improvement in LV relaxation during low calcium dialysate treatment.

Conclusion

Left ventricular relaxation is increased with the use of low calcium dialysate compared with standard dialysate treatment. The idea of possible beneficial effects of increment in LV relaxation on cardiovascular morbidity and mortality deserves further studies.

Ferritin in Kidney and Vascular Related Diseases: Novel Roles for an Old Player

Iron is at the forefront of a number of pivotal biological processes due to its ability to readily accept and donate electrons. However, this property may also catalyze the generation of free radicals with ensuing cellular and tissue toxicity. Accordingly, throughout evolution numerous pathways and proteins have evolved to minimize the potential hazardous effects of iron cations and yet allow for readily available iron cations in a wide variety of fundamental metabolic processes. One of the extensively studied proteins in the context of systemic and cellular iron metabolisms is ferritin. While clinicians utilize serum ferritin to monitor body iron stores and inflammation, it is important to note that the vast majority of ferritin is located intracellularly. Intracellular ferritin is made of two different subunits (heavy and light chain) and plays an imperative role as a safe iron depot. In the past couple of decades our understanding of ferritin biology has remarkably improved. Additionally, a significant body of evidence has emerged describing the significance of the kidney in iron trafficking and homeostasis. Here, we briefly discuss some of the most important findings that relate to the role of iron and ferritin heavy chain in the context of kidney-related diseases and, in particular, vascular calcification, which is a frequent complication of chronic kidney disease.

Levocarnitine and Dialysis: A Review

Among the various metabolic abnormalities documented in dialysis patients are abnormalities related to the metabolism of fatty acids. Aberrant fatty-acid metabolism has been associated with the promotion of free-radical production, insulin resistance, and cellular apoptosis. These processes have been identified as important contributors to the morbidity experienced by dialysis patients. There is evidence that levocarnitine supplementation can modify the deleterious effects of defective fatty-acid metabolism. Patients receiving hemodialysis and, to a lesser degree, peritoneal dialysis have been shown to be carnitine deficient, as manifested by reduced levels of plasma free carnitine and an increase in the acyl:free carnitine ratio. Cardiac and skeletal muscles are particularly dependent on fatty-acid metabolism for the generation of energy. A number of clinical abnormalities have been correlated with a low plasma carnitine status in dialysis patients. Clinical trials have examined the efficacy of levocarnitine therapy in a number of conditions common in dialysis patients, including skeletal-muscle weakness and fatigue, cardiomyopathy, dialysis-related hypotension, hyperlipidemia, and anemia poorly responsive to recombinant human erythropoietin therapy (rHuEPO). This review examines the evidence for carnitine deficiency in patients requiring dialysis, and documents the results of relevant clinical trials of levocarnitine therapy in this population. Consensus recommendations by expert panels are summarized and contrasted with present guidelines for access to levocarnitine therapy by dialysis patients.

Associations of pulmonary function with serum biomarkers and dialysis adequacy in patients undergoing peritoneal dialysis

BACKGROUND

As lung impairment is an indicator of increased morbidity and mortality in patients receiving continuous ambulatory peritoneal dialysis (CAPD), the risk factors associated with impaired lung function are of great significance. The aim of this study is to elucidate the effects of inflammatory biomarkers and dialysis adequacy on pulmonary function, in CAPD patients.

METHODS

101 patients undergoing CAPD, 30 CKD5 patients and 30 healthy subjects were enrolled. Spirometry and serum biomarkers were evaluated in each subject. Pulmonary function was compared among patients and control groups. Pearson analysis was used to analyze the correlation between serum biomarkers, dialysis adequacy and pulmonary function.

RESULTS

Lower vital capacity, maximal voluntary ventilation (MVV), forced vital capacity (FVC), peak expiratory flow (PEF), maximal mid-expiratory flow rate (MMEF), and diffusing capacity of the lung for carbon monoxide (DLCO) were observed in the CAPD group (all P < 0.05) when compared with control subjects. DLCO % was negatively correlated with CRP (r = -0.349, P = 0.007) and positively correlated with albumin (r = 0.401, P = 0.002). Total Kt/V was associated positively with MMEF % (r = 0.316, P = 0.019), and MVV % (r = 0.362, P = 0.007). nPNA was positively correlated with FVC % (r = 0.295, P = 0.049) and MMEF % (r = 0.381, P = 0.010).

CONCLUSION

The results suggest that lung function decline was directly related to higher CRP level, hypoalbuminemia, and dialysis inadequacy. These findings provide the evidence that inflammation and dialysis adequacy play a role in predicting outcomes of CAPD patients with pulmonary impairment.

Does Omega-3 supplementation decrease carotid intima-media thickening in hemodialysis patients?

Objective:

A randomized, double-blind, placebo-controlled clinical trial was performed to assess the effect of omega-3 supplementation (3 g/day) on atherosclerosis progression by measuring carotid intima-media thickness (cIMT) in hemodialysis (HD) patients.

Methods:

A total of 54 HD patients were randomized into two groups: Intervention group (n = 27), in which patients were given 3 g/day omega-3 for 6 months and placebo group (n = 27), in which patients received placebo using the same administration protocol. All patients underwent a carotid artery ultrasound scan to measure cIMT at baseline and at 6 months.

Findings:

cIMT decreased significantly in omega-3 group (0.79 ± 0.21 mm at baseline vs. 0.65 ± 0.18 mm at 6 months, P < 0.001). On the other hand, a nonsignificant increase in cIMT was seen in placebo group (0.75 ± 0.17 mm at baseline vs. 0.79 ± 0.17 mm at 6 months, P = 0.12). Moreover, cIMT was statistically significantly different between omega-3 and placebo groups at 6 months (P < 0.001). After 6 months, a statistically significant increase was observed in high-density lipoprotein level in omega-3 group compared to placebo group (P = 0.03). Urea reduction ratio was also statistically significantly higher in omega-3 than placebo group at 6 months (P = 0.03). No significant difference was observed in terms of other variables between the two groups.

Conclusion:

These data suggested that omega-3 supplementation plays a protective role in the progression of atherosclerosis in HD patients.

Microvascular dilatation after haemodialysis is determined by the volume of fluid removed and fall in mean arterial pressure

BACKGROUND/AIMS

The effects of haemodialysis on the microcirculation are poorly understood. This study examined the changes in small vessel calibre.

METHODS

24 patients (including 12 males, median age 62.5 years, range 30-87) underwent digital retinal photography immediately before and after routine haemodialysis. Arteriolar and venular calibres were measured from the images by a trained grader using a highly reproducible, computer-assisted method.

RESULTS

Patients had an average 2.0 ± 0.3 litres of fluid removed with dialysis, and their mean arterial blood pressure fell by 6.8 mm Hg (CI 13.8-0.2, p = 0.06). Retinal arteriole calibre did not change (mean difference 2.3 µm, CI -1.1 to 5.7, p = 0.17) but the venules dilated (mean difference 12.7 µm, CI 7.3-18.3, p < 0.001). Calibre returned to baseline by 2 h. Venules dilated less in diabetics than non-diabetics (mean difference -6.2 µm, CI -9.6 to -2.9, p < 0.01). Retinal venular dilatation correlated positively with the volume of fluid removed per kilogramme body weight (5.9, CI 0.2-11.5, p = 0.04), and negatively with the fall in mean arterial pressure (-0.36, CI -0.72 to -0.01, p < 0.05) after adjusting for age, gender, diabetes and dyslipidaemia.

CONCLUSION

Haemodialysis is associated with systemic venular dilatation.

The microvasculature in chronic kidney disease

BACKGROUND AND OBJECTIVES

Individuals with chronic kidney disease (CKD) stages 3 to 5 have an increased risk of cardiac and other vascular disease. Here we examined the association of CKD 3 to 5 with small vessel caliber.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This was a cross-sectional observational study of 126 patients with CKD stages 3 to 5 (estimated GFR [eGFR] <60 ml/min per 1.73 m(2)) and 126 age- and gender-matched hospital patients with CKD 1 or 2. Retinal vessel diameters were measured from digital fundus images by a trained grader using a computer-assisted method and summarized as the central retinal artery equivalent (CRAE) and central retinal vein equivalent (CRVE).

RESULTS

Patients with CKD 3 to 5 had a smaller mean CRAE and CRVE than hospital controls (139.4 ± 17.8 μm versus 148.5 ± 16.0 μm, P < 0.001; and 205.0 ± 30.7 μm versus 217.4 ± 25.8 μm, respectively; P = 0.001). CRAE and CRVE decreased progressively with each stage of renal failure CKD1-2 to 5 (P for trend = 0.08 and 0.04, respectively). CKD and hypertension were independent determinants of arteriolar narrowing after adjusting for age, gender, diabetes, dyslipidemia, and smoking history. Patients with CKD 5 and diabetes had a larger mean CRAE and CRVE than nondiabetics (141.4 ± 14.9 μm versus 132.9 ± 14.2 μm; 211.1 ± 34.4 μm versus 194.8 ± 23.8 μm).

CONCLUSIONS

The microvasculature is narrowed in patients with reduced eGFR.

Intravenous Iron Gluconate Administration Increases Circulating PAPP-A in Hemodialysis Patients

BACKGROUND

Pregnancy-associated plasma protein-A (PAPP-A) is a proatherosclerotic molecule, interrelated with oxidative stress in hemodialysis (HD) patients. As intravenous (IV) iron might enhance oxidative stress in HD patients, this study investigates circulating PAPP-A during HD session and after IV iron administration.

METHODS

In 20 HD patients, plasma PAPP-A concentration was assessed immunochemically during 2 HD sessions (prior to HD and at 60, 130, and 240 min of HD session). Sodium ferric gluconate (62.5 mg) was given IV to all patients 65 min after the start of the second HD.

RESULTS

Sixty-five min after IV iron application, there was a significant increase in plasma PAPP-A (from 36.0+/-9.9 to 79.6+/-28.9 mU/L, p<0.0001). At the end of this HD session, PAPP-A decreased significantly (p<0.0001), but still remained 1.5-fold greater compared with predialysis levels (p<0.0005).

CONCLUSION

IV iron increases circulating PAPP-A, and in this way, it might contribute to more pronounced cardiovascular complications in HD patients.

Chronic kidney disease Markov model comparing paricalcitol to calcitriol for secondary hyperparathyroidism: a US perspective

OBJECTIVE

The objective of this study was to determine the cost effectiveness of paricalcitol versus calcitriol for the treatment of secondary hyperparathyroidism in patients with chronic kidney disease in the United States setting.

METHODS

A Markov process model was developed employing data sources from the published literature, paricalcitol clinical trials and observational studies, official US price/tariff lists and national population statistics. The comparator was calcitriol, a non-selective vitamin D receptor activator (VDRA) medication. The primary perspective of the study was that of the third-party payer in the US. The efficacy outcomes (reduction in secondary hyperparathyroidism (SHPT), reduction in proteinuria, complications and mortality) were extrapolated to: number of life-years gained (LYG) and number of quality-adjusted life-years (QALYs). Clinical and economic outcomes were discounted at 3.5%.

RESULTS

The reference case analysis was a 10-year time horizon based on a comparison of paricalcitol with calcitriol, which is started in chronic kidney disease (CKD) stage 3 and continued in CKD stage 4 and CKD stage 5. The use of paricalcitol leads to a cost saving of US$1941. The inclusion of indirect costs leads to a cost saving of US$2528. The use of paricalcitol leads to an increase in life-years gained (0.47 years) and a gain in QALYs (0.43). The use of paricalcitol results in a dominant outcome from the perspective of the third-party payer, as well as from the societal perspective. One-way sensitivity analyses and probabilistic sensitivity analyses confirmed the robustness of the model.

CONCLUSION

This model showed that the favorable clinical benefit of paricalcitol results in positive short and long-term health economic benefits. This study suggests that the use of paricalcitol in patients with early chronic kidney disease may be cost-effective from the third-party payer perspective in the US versus calcitriol. Additional comparative studies are necessary to validate these results.

Phosphate feeding induces arterial medial calcification in uremic mice: role of serum phosphorus, fibroblast growth factor-23, and osteopontin

Arterial medial calcification is a major complication in patients with chronic kidney disease and is a strong predictor of cardiovascular and all-cause mortality. We sought to determine the role of dietary phosphorus and the severity of uremia on vascular calcification in calcification-prone DBA/2 mice. Severe and moderate uremia was induced by renal ablation of varying magnitudes. Extensive arterial-medial calcification developed only when the uremic mice were placed on a high-phosphate diet. Arterial calcification in the severely uremic mice fed a high-phosphate diet was significantly associated with hyperphosphatemia. Moderately uremic mice on this diet were not hyperphosphatemic but had a significant rise in their serum levels of fibroblast growth factor 23 (FGF-23) and osteopontin that significantly correlated with arterial medial calcification. Although there was widespread arterial medial calcification, there was no histological evidence of atherosclerosis. At early stages of calcification, the osteochondrogenic markers Runx2 and osteopontin were upregulated, but the smooth muscle cell marker SM22alpha decreased in medial cells, as did the number of smooth muscle cells in extensively calcified regions. These findings suggest that phosphate loading and the severity of uremia play critical roles in controlling arterial medial calcification in mice. Further, FGF-23 and osteopontin may be markers and/or inducers of this process.

Pulmonary Hypertension in Peritoneal Dialysis Patients: Prevalence and Risk Factors

Aim

To investigate the prevalence of pulmonary arterial hypertension (PAH) and the possible contributing factors for PAH in patients receiving regular continuous ambulatory peritoneal dialysis (CAPD).

Patients and Methods

The study included 135 CAPD patients and 15 disease-free controls. Patients that had chronic obstructive pulmonary disease, severe mitral or aortic valve disease, connective tissue disease, history of pulmonary embolism, left ventricular ejection fraction <50%, or chest wall or parenchymal lung disease were excluded. All patients and controls were examined using echocardiography and bioelectrical impedance analysis. PAH was defined as systolic pulmonary artery pressure (PAP) >35 mmHg at rest.

Results

Mean systolic PAP was higher in the CAPD patients than in the controls (19.66 ± 11.66 vs 14.27 ± 4.55 mmHg, p = 0.001). PAH was detected in 17 (12.6%) of the 135 CAPD patients. Mean systolic PAP was significantly higher in patients with PAH than in those without PAH (42.00 ± 9.13 vs 16.44 ± 7.83 mmHg, p = 0.001). Serum albumin level and ejection fraction were lower in patients with PAH than in those without PAH ( p = 0.001 and 0.003 respectively). The ratio of extracellular water/total body water (ECW/TBW), which can reflect hydration status, was significantly higher in patients with PAH than in those without PAH ( p = 0.008). In the PD group, no patients were hypovolemic; 51 (37.8%) of the 135 PD patients were hypervolemic and 84 (62.2%) were normovolemic. Only 3 of the 17 patients with PAH were normovolemic; the rest were hypervolemic. Mean systolic PAP was significantly higher in hypervolemic PD patients (24.57 ± 14.19 mmHg) than in normovolemic PD patients (16.68 ± 7.61 mmHg) ( p = 0.001). PAP correlated with ECW/TBW ( r=0.317, p = 0.001) and left ventricular mass index (LVMI; r=0.286, p = 0.001). On the other hand, it inversely correlated with serum albumin level ( r = –0.281, p = 0.001), hemoglobin level ( r = –0.165, p = 0.044), and ejection fraction ( r = –0.263, p = 0.001). Serum albumin level, ECW/TBW, and LVMI were found in multivariate analysis to be independent risk factors for PAP.

Conclusion

PAH is a frequent cardiovascular complication in CAPD patients. Serum albumin level, hypervolemia, and LVMI are major risk factors for PAH. Therefore, strategies for treatment of hypervolemia, left ventricular hypertrophy, and hypoalbuminemia should be enhanced to prevent the development of PAH in CAPD patients.

Vitamin D Deficiency and Secondary Hyperparathyroidism Among Patients with Chronic Kidney Disease

BACKGROUND

Chronic kidney disease (CKD) is associated with morbid complications that lead to high mortality and costs. Vitamin D deficiency and secondary hyperparathyroidism (SHPT) are frequent complications of CKD.

METHODS

We reviewed the current literature regarding the prevalence, diagnosis, complications, and management of vitamin D deficiency and SHPT among patients with CKD.

RESULTS

There is a high prevalence of vitamin D deficiency among adolescents and adults in the United States (age and gender dependent). Patients with CKD or those who are dialysis-dependent are much more likely to have low levels of vitamin D in comparison to those without kidney disease. In order to avoid significant complications including SHPT and musculoskelatal diseases, vitamin D needs to be measured routinely by primary care physicians and nephrologists. In the majority of CKD patients, SHPT is not diagnosed until late, leading to advanced cardiovascular and bone diseases.

CONCLUSIONS

In conclusion, current management of vitamin D deficiency and SHPT is suboptimal. Early diagnosis of vitamin D deficiency and SHPT are integral to optimal management of CKD, and additional research is needed in this area.

Coronary-artery calcium scores using electron beam CT in patients with chronic renal failure

We evaluated the risk of coronary-artery disease in patients with chronic renal failure (CRF) by measuring the coronary-artery calcium scores with electron beam CT (EBCT). A total of 81 CRF patients were divided into three groups; pre-dialysis (group I, n = 35), hemodialysis (group II, n = 31) and peritoneal dialysis (group III, n = 15). The several serum biochemical markers and calcium score levels by EBCT were determined. The Ca x P products were significantly higher in groups II (p < 0.05) and III (p < 0.01) than in group I. The serum calcium levels were significantly higher in group III than in both group I (p < 0.01) and II (p < 0.05). The serum calcium level in 15 patients with a calcium score > 400 was significantly higher than the 66 patients with a score < or =400 (p < 0.01). The calcium score was significantly higher in the 15 patients with cardiovascular complications than in the 66 patients without cardiovascular complications (628.9+/-904.8 vs. 150.4+/-350.9, p < 0.01). EBCT seemed to be a good diagnostic tool for evaluating the risk of coronary-artery disease ''noninvasively'' in CRF patients who are at increased risk of cardiovascular morbidity and mortality.

Coronary calcification in hemodialysis patients: the contribution of traditional and uremia-related risk factors

BACKGROUND

Coronary artery calcification is a common feature of atherosclerosis, occurring in 90% of angiographically significant lesions. There is recent evidence that coronary artery calcification is frequent in hemodialysis patients and it has been suggested that this increased incidence may be associated to uremia-related factors. The development and progression of coronary artery calcification is similar to osteogenesis. The aim of this study was to evaluate the relationship between coronary artery calcification, uremia-related factors, and bone histomorphometry in hemodialysis patients.

METHODS

A total of 101 hemodialysis patients were assessed for biochemical markers of inflammation, oxidative stress, and bone metabolism. Subsequently, they were submitted to multislice coronary tomography (MSCT) and transiliac bone biopsy.

RESULTS

The median calcium score was 116.2 (range 0 to 5547). Fifty-two percent of the patients showed moderate and severe coronary artery calcification, 20% had calcium scores greater than 1000. In univariate analysis, age (r= 0.57, P < 0.000001), osteoprotegerin (OPG) (r= 0.44, P= 0.00002), and body mass index (BMI) (r= 0.24, P= 0.01) correlated positively with calcium score. Bone trabecular volume and trabecular thickness correlated negatively with calcium score (r=-0.24, P= 0.02; r=-0.22, P= 0.03). There was a correlation of borderline significance between calcium score and C-reactive protein (CRP) (r= 0.18, P= 0.062). The multiple linear regression analysis identified OPG as the only variable independently associated with coronary artery calcification.

CONCLUSION

Coronary artery calcification is highly prevalent in the hemodialysis population and is associated with older age, higher BMI, inflammation and reduced trabecular bone volume. Higher OPG is independently associated with coronary artery calcification and may represent an incomplete self-defensive response to the progression of atherosclerosis in hemodialysis patients.

Adverse effects of hyperphosphatemia on myocardial hypertrophy, renal function, and bone in rats with renal failure

BACKGROUND

Hyperphosphatemia and disturbances in calcium or parathyroid hormone (PTH) metabolism contribute to the high incidence of cardiovascular disease and renal osteodystrophy in chronic renal failure (CRF). We evaluated the effect of hyperphosphatemia on the cardiovascular system, on renal function, and on bone in experimental uremia.

METHODS

Wistar rats were submitted to parathyroidectomy (PTx) and 5/6 nephrectomy (Nx) with minipump implantation, delivering 1-34 rat PTH (physiologic rate), or were sham-operated and received vehicle. Only phosphorus content (low-phosphorus (LP) 0.2%; high-phosphorus (HP) 1.2%) differentiated diets. We divided the groups as follows: PTx +Nx +LP; sham + LP; PTx + Nx + HP; and sham + HP. Tail-cuff pressure and weight were measured weekly. After 2 months, biochemical, arterial, and myocardial histology and bone histomorphometry were analyzed.

RESULTS

Heart weight normalized to body weight (heart weight/100 g body weight) was higher in PTx + Nx + HP rats (PTx + Nx + HP = 0.36 +/- 0.01 vs. sham + HP = 0.29 +/- 0.01, PTx + Nx + LP = 0.32 +/- 0.01, sham + LP = 0.28 +/- 0.01) (P < 0.05). Serum creatinine levels were higher in PTx + Nx + HP rats than in PTx + Nx + LP rats (1.09 +/- 0.13 vs. 0.59 +/- 0.03 mg/dL) (P < 0.05). Levels of PTH did not differ significantly between the groups. Myocardial and arterial histology detected no vascular calcification or fibrosis. Bone histomorphometry revealed an association, unrelated to uremia, between HP diets and decreased trabecular connectivity.

CONCLUSION

Myocardial hypertrophy, impaired renal function, and adverse effects on bone remodeling were associated with hyperphosphatemia and were not corrected by PTH replacement. Although no vascular calcification was observed in this model, we cannot rule out an adverse effect of hyperphosphatemia on the vascular bed. Our finding underscores the importance of phosphorus control in reducing morbidity and mortality in CRF patients.

Serum cardiac troponin and subclinical cardiac status in pediatric chronic renal failure

BACKGROUND

Patients with uremia often have elevated serum cardiac troponin T (cTnT) even without clinical heart damage. Pediatric patients are ideal for studies of the relationship between uremia and heart disease because they are unlikely to have cardiac risk factors other than uremia.

OBJECTIVE

To determine the relationship between uremia and cTnT levels.

DESIGN

Echocardiograms and blood chemistry results were obtained from 50 pediatric patients with chronic renal failure and without clinical heart disease. Levels of cTnT were tested for correlation with cardiac dysfunction. In multivariate analysis, biochemical aspects of renal disease and its treatment were tested for correlation with cardiac dysfunction.

RESULTS

Forty-nine patients had cardiovascular abnormalities, including increased left ventricular function and mass, elevated heart rate and blood pressure, and reduced LV afterload. LV contractility was inversely correlated with cTnT level (r = -0.36). Higher cTnT also correlated with higher serum creatine kinase-MB mass, lower serum parathyroid hormone, higher blood urea nitrogen and bicarbonate levels, and the use of diuretics, but not with higher cardiac troponin I. Left ventricular contractility was inversely related to serum creatinine, phosphorus, and the use of beta-blockers.

CONCLUSIONS

Elevated cTnT levels are not artifactual, but are genuine indicators of cardiomyocyte damage. Cardiac damage, indicated by either elevated cTnT or low LV contractility, is related to uremia, deranged calcium and phosphorus metabolism, and bicarbonate levels. Serum cTnT and LV contractility identify subclinical cardiac damage that could be treated to hopefully reduce cardiovascular morbidity and mortality in this high-risk population.

Thrombosis in end-stage renal disease

Although renal failure has classically been associated with a bleeding tendency, thrombotic events are common among patients with end-stage renal disease (ESRD). A variety of thrombosis-favoring hematologic alterations have been demonstrated in these patients. In addition, "nontraditional" risk factors for thrombosis, such as hyperhomocysteinemia, endothelial dysfunction, inflammation, and malnutrition, are present in a significant proportion of chronic dialysis patients. Hemodialysis (HD) vascular access thrombosis, ischemic heart disease, and renal allograft thrombosis are well-recognized complications in these patients. Deep venous thrombosis and pulmonary embolism are viewed as rare in chronic dialysis patients, but recent studies suggest that this perception should be reconsidered. Several ESRD treatment factors such as recombinant erythropoietin (EPO) administration, dialyzer bioincompatibility, and calcineurin inhibitor administration may have prothrombotic effects. In this article we review the pathogenesis and clinical manifestations of thrombosis in ESRD and evaluate the evidence that chronic renal failure or its management predisposes to thrombotic events.

Differential effects of 19-nor-1,25-(OH)(2)D(2) and 1alpha-hydroxyvitamin D(2) on calcium and phosphorus in normal and uremic rats

BACKGROUND

Calcitriol, 1,25-(OH)(2)D(3) (1,25D), the most active metabolite of vitamin D, has been used in the treatment of secondary hyperparathyroidism (SH) because it controls parathyroid gland growth and suppresses parathyroid hormone (PTH) synthesis and secretion. Due to the calcemic and phosphatemic actions of 1,25D, two analogs with potentially less side effects, 19-nor-1,25-(OH)(2)D(2) (19-nor) and 1alpha(OH)D(2) (1alphaD(2)) are currently being used in the treatment of SH.

METHODS

This study compares the effects of these two analogs on calcium (Ca) and phosphorus (P) metabolism in normal, uremic, and parathyroidectomized (PTX) rats. Using doses of 50 to 250 ng of 19-nor or 1alphaD(2), experiments were conducted in normal and uremic rats.

RESULTS

In uremic rats, 19-nor did not increase plasma Ca or P while 1alphaD2 caused a dose-dependent increase in both. In addition, while the Ca x P product remained unchanged in 19-nor-treated rats, it increased progressively with 1alphaD(2)administration. In metabolic studies in normal rats treated with vehicle, 10 ng of 1,25D, 100 ng of 19-nor or 100 ng 1alphaD(2), intestinal calcium absorption and urinary calcium excretion were significantly higher in 1alphaD(2)-treated rats compared to those receiving 19-nor. Similar results were seen for intestinal phosphorus absorption and urinary phosphorus excretion. Finally, the skeletal response to these two analogs was tested in PTX rats fed a calcium-deficient diet and treated daily with 100 ng of 19-nor or 1alphaD(2). The increase in plasma calcium in 1alphaD2-treated rats was markedly higher than in those receiving 19-nor. Similar results were seen in plasma phosphorus when these studies were repeated using a phosphorus-deficient diet.

CONCLUSIONS

These studies demonstrate that when given in large doses to rats 19-nor is less calcemic and phosphatemic than 1alphaD(2). The lower Ca x P product in 19-nor treated rats may be an important consideration in patient therapy. Further studies in patients are necessary to define the clinical applicability of these differences.

Malnutrition in hemodialysis diabetic patients: evaluation and prognostic influence

BACKGROUND

This work aimed to evaluate the role of malnutrition in the increased mortality rate of hemodialysis diabetic patients from a French cooperative series.

METHODS

Body mass index (BMI), serum albumin, prealbumin, cholesterol, and pre-dialysis creatinine, normalized protein catabolic rate and lean body mass (LBM) were measured in 734 diabetic and 6389 non-diabetic patients (aged 63.4 +/- 12.2 and 62.0 +/- 15.9 years; 1.01 male to 1.40 female ratio). The outcome of 1610 of these patients, including 170 diabetics, was assessed during a 30-month follow-up.

RESULTS

Diabetic as compared to non-diabetic patients showed a significant (P < 10-4) increased BMI (25.9 +/- 5.2 vs. 23.1 +/- 4.3) and cholesterol (5.5 +/- 1.6 vs. 5.3 +/- 1.5 mmol/L), and decreased albumin (37.8 +/- 5.4 vs. 38.9 +/- 5.3 g/L), prealbumin (317 +/- 91 vs. 340 +/- 94 mg/L), creatinine (711 +/- 184 vs. 816 +/- 217 micromol/L) and LBM (76 +/- 18 vs. 87 +/- 21%). Normalized protein catabolic rate was similar in the two groups (1.11 +/- 0.31 vs. 1.13 +/- 0.32 g/kg/L). One and two-year survival was 83.7 +/- 2.9% and 65.5 +/- 3.8% in diabetic patients versus 90.3 +/- 0.8% and 79.9 +/- 1.1% in non-diabetics (relative risk 1.26, P < 0.01). Independent predictors of survival were age, albumin and prealbumin in non-diabetics and only age in diabetics.

CONCLUSION

Diabetic patients compared to non-diabetics were characterized by an increased incidence of protein malnutrition and decreased survival. However, the higher death risk associated with diabetes was not related to malnutrition.

Critical care issues in the patient with chronic renal failure

The metabolic abnormalities associated with chronic renal failure and complications of the dialysis procedure present unique challenges in critical care medicine. Understanding how renal failure impacts the development and management of cardiovascular disease, bleeding tendencies, infection, and malnutrition is necessary to provide optimal care for these patients. The recognition of ESRD as a state of chronic inflammation and increased oxidative stress ultimately should lead to more effective treatment approaches for several of the comorbid conditions common in this patient population.

Slowing the progression of chronic renal failure: economic benefits and patients' perspectives

Because of the predicted increase in end-stage renal disease (ESRD) incidence (projected increase from 1998 to 2010; 86,825 to 172,667), prevalence (projected increase from 1998 to 2010; 326,217 to 661,330), and cost (total cost based on 1998 ratio of Medicare versus non-Medicare cost; $16.74 billion in 1998 to $39.35 billion in 2010), a cohesive national effort is needed to develop strategies to slow the progression of chronic renal failure (CRF). The question arises to how much reduction in the progression of CRF would lead to a meaningful decrease in the prevalence and cost of ESRD. There are no objective data that show the economic impact of slowing the progression of CRF. We developed a mathematical model to assess the economic impact of decreasing the progression of CRF by 10%, 20%, and 30%. US Renal Data System (USRDS) projections were used to model the rate of increase in ESRD incidence and prevalence. Glomerular filtration rate (GFR) at the initiation of ESRD therapy and cost per patient-year were based on USRDS data. The average decline in GFR in subjects with CRF was estimated to be 7.56 mL/min/y. All dollar savings reflect 1998 costs, discounted for the future at 3% per annum. We also determined how much slowing of the progression of CRF is important from patients' perspectives by means of a written questionnaire (which inquired about willingness to go on a restricted diet, take six extra medications per day, and make six extra office visits per year) and calculation of the pre-ESRD time gained for different degrees of reduction in the progression of CRF. If the rate of decline in GFR decreased by 10%, 20%, and 30% after December 31, 1999, in all patients with GFRs of 60 mL/min or less, cumulative direct healthcare savings through 2010 would equal approximately $18.56, $39.02, and $60.61 billion, respectively. For a 10%, 20%, and 30% decrease in the rate of decline in GFR in all patients with a GFR of 30 mL/min or less, estimated cumulative savings through 2010 equal $9.06, $19.98, and $33.37 billion, respectively. Responses to the questionnaire showed that approximately 79% of subjects with CRF (n = 113) perceived a few weeks' dialysis-free period significant (P < or = 0.0001), a period corresponding to a 10% reduction in the rate of decline in GFR. Our data suggest that the cumulative economic impact of slowing the progression of CRF, even by as little as 10%, would be staggering. They provide strong support for the development and implementation of intensive reno-protective efforts beginning at the early stages of chronic renal disease and continued throughout its course.

Cardiovascular calcification in end-stage renal disease

Cardiovascular diseases are common in patients with end-stage renal disease (ESRD) and cardiovascular morbidity and mortality among dialysis patients are substantially higher than in the general population. The reasons for this high incidence are multiple. They include traditional factors such as hypertension, diabetes, dyslipidaemia, sodium overload, and elevated homocysteine levels as well as disturbances of mineral metabolism, specifically abnormalities in phosphorus and calcium homeostasis. This review will describe the specific cardiovascular complications related to calcifications in ESRD, the implications of the abnormalities of mineral metabolism in its pathogenesis and the current imaging techniques available for the detection of cardiovascular calcifications. Excess of calcium load contributes to the development of cardiac calcifications; therefore, alternative strategies to diminish exogenous calcium load should be considered in patients with ESRD.

Are lipid values and BMI related to hospitalizations in the hemodialysis population?

OBJECTIVE

To examine the relationship between lipid values and BMI (body mass index) on hospitalizations in hemodialysis (HD) patients.

DESIGN

Retrospective (2-year) study.

SETTING

Outpatient dialysis center in a large metropolitan city.

PATIENTS

This study used 158 HD patients stratified on the basis of ethnicity (non-Black and Black) and diabetic status (nondiabetic and diabetic).

INTERVENTION

Subjects were observed for 2 years. Body weight, BMI, lipid parameters, and hospitalization duration were determined 8 times (3-month intervals).

MAIN OUTCOME MEASURES

Body weight, BMI, lipid parameters (serum triglyceride concentration, serum total cholesterol, high-density lipoprotein [HDL]-, low-density lipoprotein [LDL]-, very low-density lipoprotein [VLDL]- cholesterol concentrations, serum Apo-protein A1 [Apo-A1] concentration, and serum Apo-protein B [Apo-B] concentration), and morbidity data were recorded.

RESULTS

Hemodialysis subjects were hospitalized 2.3 +/- 1.6 times over the 2-year experimental period. Length of hospital stay averaged 6.6 +/- 0.5 days/hospitalization. Length of hospital stay was inversely related to HDL concentration (r = -0.21, P <.05, n = 89), but not significantly related to BMI in HD subjects. BMI was positively associated with LDL concentration (r = +0.28, P <.01, n = 97). Cholesterol concentration was directly associated with LDL concentration (r = +0.52, P <.01, n = 138), VLDL concentration (r = +0.47, P <.01, n = 139), and triglyceride concentration (r = +0.54, P <.01, n = 155). Mean concentration of HDL-cholesterol was inversely related serum triglyceride concentration (r = -0.43, P <.01, n = 140). Although Apo-A1 concentration was directly associated with HDL level (r = +0.39, P <.01, n = 139), Apo-B was inversely related to HDL level (r = -0.37, P <.01, n = 138) and directly related to cholesterol concentration (r = +0.71, P <.01, n = 138), VLDL concentration (r = +0.87, P <.01, n = 138), and triglyceride concentration (r = +0.81, P <.01, n = 138).

CONCLUSION

Cardiac disease remains the primary cause of morbidity and mortality in HD patients, and results of the present study suggest that dyslipidemias present in the HD population negatively impact cardiovascular profiles which, in turn, influence the frequency/duration of hospitalizations. Among all lipid parameters analyzed in the present study, increased LDL and decreased HDL concentrations were more strongly related to length of hospital stay than was BMI.

Cardiovascular disease in chronic renal insufficiency

Cardiovascular illness is an important contributor to the morbidity of kidney disease. The spectrum of cardiovascular disease (CVD) in patients with chronic renal insufficiency (CRI) includes left ventricular hypertrophy (LVH) and dilatation, ischemic heart disease, and peripheral vascular disease. Both "traditional" and "uremia-specific" factors contribute to the occurrence and progression of cardiac disease in renal patients. A growing body of recent evidence indicates that the processes contributing to CVD commence early in CRI, leading to concentric LVH, left ventricular dilatation, congestive heart failure, and ischemic heart disease. Many of the coexisting conditions that have been identified consistently as contributing to the burden of cardiovascular illness in renal populations can be modified through medical interventions. Specific therapies exist for hypertension, anemia, hyperparathyroidism, and dyslipidemia. Studies to date have demonstrated that treatment of many of these factors-such as anemia and hypertension during end-stage renal disease-appear to benefit the cardiovascular system. Earlier intervention may offer the best opportunity to reduce the burden of illness in all groups of CRI patients. Identification of patients at the onset of kidney disease and attention to the known traditional and "uremic" risk factors are emerging as promising strategies. Long-term interventional studies are needed to determine costs, benefits, and risks of such strategies.

Early and long-term results of coronary artery bypass grafting in dialysis patients

BACKGROUND

Dialysis patients frequently present with debilitating coronary artery disease but are regarded as challenging patients for coronary artery bypass grafting.

METHODS

The operative, early postoperative, and late results of 44 dialysis patients undergoing coronary artery bypass grafting from 1984 to 1997 were retrospectively reviewed.

RESULTS

Compared with patients in The Society of Thoracic Surgeons database who underwent coronary artery bypass grafting, only cerebrovascular accident and postoperative cardiac arrest occurred more frequently in dialysis patients. However, 73% experienced some type of complication. Operative mortality was 11.4%. Decreased left ventricular ejection fraction and severe distal disease were predictive of increased operative mortality. New York Heart Association angina class fell from 2.8 to 1.5, and New York Heart Association congestive heart failure class fell from 2.6 to 1.8. Overall quality-of-life scores did not improve; however, walking distances remained consistently improved. Actuarial survival at 5 years was 32.0%+/-12.0%. Five-year survival was 0% for smokers and 83.6%+/-7.6% for nonsmokers (p = 0.0142). Causes of late death were myocardial infarction (4), sepsis (1), subdural hematoma (1), stroke (1), and unknown (6).

CONCLUSIONS

Coronary artery bypass grafting should be avoided in dialysis patients with severe diffuse disease. A smoking history is associated with poor outcome. Coronary artery bypass grafting in dialysis patients is associated with a higher incidence of complications but can be performed with an acceptable operative mortality and is associated with good symptomatic relief of angina and heart failure.

Re-evaluation of risks associated with hyperphosphatemia and hyperparathyroidism in dialysis patients: recommendations for a change in management

Hyperphosphatemia is a predictable consequence of chronic renal failure and is present in most patients on dialysis. Traditionally, the risk associated with elevated serum phosphorus has focused on its impact on renal osteodystrophy. A growing body of evidence, however, suggests that abnormalities in serum phosphorus, calcium-phosphorus product (CaxP), and parathyroid hormone (PTH) levels are resulting in vascular and visceral calcification, thereby contributing to the substantially increased risk of cardiovascular death in this population. In this analysis, we review in detail the literature that describes these associations. We show that the current treatment paradigm for serum phosphorus and secondary hyperparathyroidism is ineffective for a large segment of dialysis patients. Currently, 60% of hemodialysis patients have phosphorus greater than 5.5 mg/dL, and 40% have CaxP greater than 60 mg(2)/dL(2). It is our belief that prevention of uremic calcification, cardiac death, and vascular disease should assume primary importance when evaluating the risks associated with elevated levels of phosphorus, CaxP, and PTH. We recommend that target levels should become 9.2 to 9.6 mg/dL for calcium, 2.5 to 5.5 mg/dL for phosphorus, less than 55 mg(2)/dL(2) for CaxP product, and 100 to 200 pg/mL for intact PTH.

Renal replacement therapy in the elderly: medical, ethical, and psychosocial considerations

As patients over the age of 65 become the fastest growing segment of our treated end-stage renal disease (ESRD) population, nephrologists and allied healthcare workers who care for these patients must become well versed in the many issues specific to this group. Elderly patients contribute the greatest fraction to the incidence and prevalence of the United States ESRD population. Their life expectancy is greatly reduced compared with age-matched counterparts from the general population. Cardiac disease is the leading cause of death. Although renal transplantation remains the most successful form of renal replacement therapy, only a small fraction of elderly ESRD patients are transplanted. The renal research community has made great strides in improving patient outcomes on dialysis over the last decade in many areas; however, little attention has been focused on the elderly ESRD patient. The substantial mortality and comorbidity experienced by this population makes their management an ongoing challenge. Many unresolved issues remain for elderly ESRD patients in the timing of dialysis initiation, choice of dialytic therapy, use of renal transplantation, and management of cardiovascular disease. It is anticipated that future research in these areas will identify optimal treatment strategies for elderly ESRD patients starting on dialysis and improve patient outcomes.

Effect of end-stage renal disease on decreased heart rate variability

We compared short-term heart rate variability (HRV) in 60 patients with end-stage renal disease (ESRD) with 33 age-matched healthy controls and also assessed the contribution of known determinants of HRV in the ESRD patients. HRV was markedly decreased in the ESRD patients and the predictor variables of cardiac diseases, diabetes mellitus, age, heart rate, gender, and smoking explained only a small portion of HRV, suggesting that ESRD itself is an independent factor for decreased HRV.