Diabetes mellitus, aortic stiffness, and cardiovascular mortality in end-stage renal disease

Androgen deficiency and endothelial dysfunction in men with end-stage kidney disease receiving maintenance hemodialysis

OBJECTIVES AND METHODS

Two thirds of men with end-stage kidney disease (ESKD) have serum testosterone levels in the hypogonadal range. We examined if low serum testosterone levels were correlated with measures of endothelial dysfunction in ESKD. Bilateral common carotid artery (CCA) intima-media thickness (IMT) and atherosclerotic plaque occurrence, left ventricular mass index, flow- (FMD) and nitrate-mediated vasodilatation (NMD) of the brachial artery were determined by ultrasound imaging in 100 nondiabetic men with ESKD (50 men exhibited androgen deficiency; serum testosterone concentrations <300 ng/dl).

RESULTS

Left-ventricular mass index, CCA diameter, CCA-IMT and atherosclerotic plaque occurrence were all significantly increased in ESKD patients with androgen deficiency compared with patients without androgen deficiency (p < 0.05). Also, FMD and NMD measurements were significantly reduced in the former compared with the latter (p < 0.05). Testosterone levels were inversely correlated with age and duration of hemodialysis therapy (r = -0.44 and r = -0.55; p < 0.001). Testosterone levels were negatively correlated to CCA-IMT and atherosclerotic plaque occurrence in patients with androgen deficiency (r = -0.32, p < 0.003, and r = -0.23, p < 0.04, respectively). FMD and NMD measurements were positively correlated to total (r = 0.65 and r = 0.61; both p < 0.0001) and free (r = 0.52 and r = 0.48; both p < 0.001) testosterone levels in patients with low androgenicity.

CONCLUSION

The present results indicated that ESKD patients with androgen deficiency had increased CCA-IMT, atherosclerotic plaque occurrence and reduced FMD and NMD compared with patients without androgen deficiency. Testosterone serum levels were negatively correlated to CCA-IMT and positively correlated to endothelium-dependent vasodilatation in ESKD patients with androgen deficiency.

Plasma Lipoprotein Abnormalities in Hemodialysis Patients—Clinical Implications and Therapeutic Guidelines

Patients with advanced stages of chronic kidney disease (CKD) have an increased risk of death from cardiovascular disease (CVD). Dyslipidemias are associated with atherosclerotic vascular changes and the risk of occurrence of acute myocardial infarction in hemodialysis patients. However, management of dyslipidemia in hemodialysis patients does not appear to be actively carried out in routine practice. Presumably, there are three reasons for this reluctance to lipid-lowering in hemodialysis patients. First, there are epidemiological data showing the inverse relationship between cholesterol and mortality rate; a high cholesterol predicts a better survival. Second, lipids are not usually measured using standard fasting serum, but a non-fasting specimen. Third, although hypertriglyceridemia is the most common abnormality, fibrates are contraindicated in patients with renal failure because of a high risk of rhabdomyolysis. These issues are discussed in the current review article. Based on published work, lipid lowering would not increase the death rate if carried out without worsening malnutrition. The National Kidney Foundation K/DOQI Clinical Practice Guidelines recommend a reduction in fasting LDL-C below 100 mg/dL for the prevention of CVD in dialysis patients. Practically, however, the use of non-HDL-C measured by casual blood samples might be sufficient for the risk assessment in many hemodialysis patients. Statins are a good choice for lipid-lowering in dialysis patients. Furthermore, lipoprotein profile might be improved by an inventive use of dialyzer membranes, dialysate solutions, and other dialysis-related medications. For severe hypercholesterolemia, LDL-apheresis is another choice for consideration. Further studies are needed to clearly prove the benefit of lipid reduction in hemodialysis patients and those with CKD at earlier stages.

Body fat mass and lean mass as predictors of survival in hemodialysis patients

A higher body mass index (BMI) is a predictor of better survival in hemodialysis patients, although the relative importance of body fat and lean mass has not been examined in the dialysis population. We performed an observational cohort study in 808 patients with end-stage renal disease on maintenance hemodialysis. At baseline, fat mass was measured by dual-energy X-ray absorptiometry and expressed as fat mass index (FMI; kg/m2). Lean mass index (LMI) was defined as BMI minus FMI. During the mean follow-up period of 53 months, 147 deaths, including 62 cardiovascular (CV) and 85 non-CV fatal events, were recorded. In univariate analysis, LMI was not significantly associated with CV or non-CV death, whereas a higher FMI was predictive of lower risk for non-CV death. Analyses with multivariate Cox models, which took other confounding variables as covariates, indicated the independent associations between a higher LMI and a lower risk of CV death, as well as between a higher FMI and a lower risk of non-CV death. These results indicate that increased fat mass and lean mass were both conditions associated with better outcomes in the dialysis population.

Regional arterial stiffness associated with ischemic heart disease in type 2 diabetes mellitus

Arterial stiffness is increased in type 2 diabetes mellitus, and diabetes preferentially affects arterial stiffness of the central (elastic, capacitive) over peripheral (muscular, conduit) arteries. We hypothesized that arterial stiffness of the central artery may be more closely associated with ischemic heart disease (IHD) than stiffness of peripheral arteries in type 2 diabetes mellitus. The subjects were 595 type 2 diabetes patients including 70 with IHD. Arterial stiffness was measured as pulse wave velocity (PWV) in the heart-carotid, heart-femoral, heart-brachial, and femoral-ankle regions. The PWV values of the four segments correlated with each other in patients without IHD. However, the correlations were less impressive in those with IHD, suggesting unequal stiffening of regional arteries in IHD. As compared with patients without IHD, the IHD group showed significantly higher PWV values of the four arterial segments, particularly of the heart-femoral region. The presence of IHD was significantly associated with higher heart-femoral PWV, and this association remained significant and independent of other factors in a multiple logistic regression analysis. Pulse pressure was more strongly correlated with PWV of the heart-femoral than other arterial regions. Thus, diabetic patients with IHD have increased stiffness of arteries, particularly of the aorta, supporting the concept that central arterial stiffness plays an important role in the development of IHD.

Arterial wave reflections and mortality in haemodialysis patients--only relevant in elderly, cardiovascularly compromised?

BACKGROUND

Chronic kidney disease (CKD) patients have a 3-30-fold increased risk of death compared with the general population. This mortality difference is even more pronounced in younger subjects. Two markers of aortic stiffness--aortic pulse wave velocity (PWV) and augmentation index (AIx)--have been prospectively related to all-cause and cardiovascular (CV) mortality in end-stage renal disease (ESRD) populations. The aims of our study were first, to confirm the important deleterious effect of arterial stiffness in uraemia and second, to assess the impact on survival of increased AIx in a relatively young non-diabetic dialysis population, with minimal CV disease.

METHODS

Ninety-two patients (mean age 42.6 +/- 11.2 years) were included in the study and followed for a period of 61 +/- 25 months. None of the patients had diabetes mellitus, and only 3.3% had prior history of CV disease. AIx was determined by applantation tonometry using a SphygmoCor device (AtCor, PWV Inc., Westmead, Sydney, Australia).

RESULTS

Mean AIx in our study population was 19.9 +/- 13.7%; other significant haemodynamic parameters were: systolic blood pressure (SBP) 129 +/- 24 mmHg, pulse pressure 35.3 +/- 17.5 mmHg with 27.2% of the study population receiving angiotensin-converting enzyme inhibitors (ACE-I). On univariate analysis, in our group AIx correlated with: body weight (P < 0.001), radial SBP (P < 0.001) and haemoglobin levels (P < 0.05). There was no correlation between AIx and any of the echocardiographic parameters. In the stepwise multiple regression analysis, the only independent predictors for AIx were weight (P < 0.001), SBP (P < 0.001) and haemoglobin (P < 0.05) with the model explaining 33% of the AIx variability (adjusted R(2) = 0.33). During the follow-up period, 15 deaths were recorded. In the Cox analysis (P = 0.014; chi square 20.7 for the model) the only independent predictors for all-cause mortality were age (P = 0.001), left ventricular mass index (P = 0.032) and ACE-I therapy (P = 0.039) while AIx did not reach statistical significance. There was no difference in patients' survival when divided by AIx tertiles, assessed by the log rank test (P = 0.78).

CONCLUSION

Our results fail to support the notion that an increased effect of wave reflections on central arteries is a strong and independent predictor of mortality in all ESRD patients on haemodialysis. The effect of arterial wave reflections might be in fact dependent on patient age and concurrent comorbidity status.

Cardiovascular disease in the dialysis population: prognostic significance of arterial disorders

PURPOSE OF REVIEW

Cardiovascular disease is a major factor in the high mortality of patients with end-stage renal disease, and this population is particularly appropriate to analyse the impact of cardiovascular risk markers on outcome.

RECENT FINDINGS

Cardiovascular risk markers in end-stage renal disease include age, left ventricular mass, carotid intima-media thickness, blood pressure and aortic stiffness (pulse wave velocity). Aortic pulse wave velocity has been shown to be an independent predictor of cardiovascular mortality in patients with end-stage renal disease and the general population. Aortic pulse wave velocity has the highest sensitivity and specificity as a predictor of cardiovascular death in end-stage renal disease patients. Pulse wave velocity is an integrated index of vascular function and structure, and is a major determinant of systolic hypertension, thereby increasing left ventricular afterload, left ventricular hypertrophy and left ventricular oxygen consumption. Decreased diastolic blood pressure, another consequence of arterial stiffening, is associated with decreased coronary perfusion contributing to ischaemic heart disease and evolution of adaptive into maladaptive left ventricular hypertrophy.

SUMMARY

Aortic stiffness measurements could serve as an important tool in identifying end-stage renal disease patients at higher risk of cardiovascular disease. The ability to identify these patients would lead to better risk stratification and earlier and more cost-effective preventive therapy.

Regional arterial stiffness in patients with type 2 diabetes and chronic kidney disease

Increased arterial stiffness is an independent predictor of death from cardiovascular disease, and aortic stiffness is more predictive than stiffness of other arterial regions. Because little is known about the effect of chronic kidney disease (CKD) on regional arterial stiffness, pulse wave velocity (PWV) of four different arterial segments was measured in patients who had type 2 diabetes with and without various stages of CKD. A total of 434 patients had type 2 diabetes, and there were 192 healthy control subjects who were comparable in age and gender. GFR was estimated by the abbreviated Modification of Diet in Renal Disease equation. The patients with diabetes were classified into CKD stages by the definition of the Kidney Disease Outcomes Quality Initiative guidelines. PWV was measured in the heart-femoral, heart-carotid, heart-brachial, and femoral-ankle segments simultaneously using an automatic pulse wave analyzer. PWV of each arterial region was increased in patients who had diabetes without kidney damage and was increased further in a stepwise manner with the advanced stages of CKD. The increase in PWV was greater in the heart-femoral and heart-carotid regions than in the heart-brachial and femoral-ankle segments. However, after adjustment for age, BP, and other confounding factors using a multiple regression model, decreased GFR was independently associated with increased PWV of the heart-femoral region but not with PWV of other arterial segments. In type 2 diabetes, CKD was associated with increased stiffness of arteries, particularly of the aorta. The cross-sectional result may explain the increased risk for cardiovascular disease in CKD, although longitudinal studies are needed to confirm it.

Estimation of an age-specific reference interval for pulse wave velocity: a meta-analysis

OBJECTIVE

To estimate an age-specific reference interval for carotid-femoral pulse wave velocity (PWV), an index of aortic stiffness, and to determine the predictive values of the reference range for detecting those at moderate and high risk of cardiovascular disease (CVD).

DESIGN AND METHODS

We searched MEDLINE using PubMed from 1995 to 2005 for all studies in which Carotid-Femoral PWV was measured using a Complior (Colson, Paris, France) apparatus in Caucasian non-pregnant adults. Twenty-five studies were included, covering 30 groups of subjects; these groups were classified a priori into low (normal), moderate, and high CVD risk categories, with 2008, 5979, and 180 (total 8167) subjects, respectively. Individual-level data were simulated for each group, and an age-specific reference interval was calculated by using fractional polynomial functions.

RESULTS

We plotted an age-adjusted normal curve for PWV with 2.5, 5, 50, 90, 95, and 97.5 centile limits. Applying this reference interval to the moderate- and high-risk groups using simulations yielded sensitivities of 34.3 [95% confidence interval (CI) 33.2-35.3] and 57.2 (95% CI 55.2-59.3), respectively, specificities of 95.3 (95% CI 94.8-95.8) and 95.3 (95% CI 94.4-96.2), respectively, and positive likelihood ratios of 7.3 and 12.2, respectively.

CONCLUSION

We constructed an age-adjusted reference curve for PWV. Using the 95th centile of this curve as a threshold (e.g. 10.94, 11.86, and 13.18 m/s for 20, 40, and 60 years old) shows construct validity, as it appears to identify medium and high CVD risk groups reasonably accurately. This reference range needs to be tested using other datasets.

Osteopontin Expression in Vascular Smooth Muscle Cells in Patients With End-Stage Renal Disease

beta-glycerophosphate, a phosphate donor, and uremic sera induce osteopontin (OPN) expression in bovine vascular smooth muscle cells (VSMCs). However, the correlations of serum phosphorus level with OPN expression, and blood urea nitrogen (BUN) level with OPN expression in humans have not previously been reported. The purpose of the current study is to compare the expression of OPN in VSMCs with clinical data in patients with end-stage renal disease (ESRD). The radial arteries of 33 patients (21 male and 12 female patients) were examined to determine the expression of OPN and collagen type I (Col I) by immunohistochemistry. The correlation of the expression of bone matrix proteins with clinical data was analyzed. Between the low-serum phosphorus (<6 mg/dL) group and high-serum phosphorus (> or =6 mg/dL) group, significant differences were detected in the expression of OPN (P = 0.0049) and the levels of BUN (P = 0.0005), serum phosphorus (P < 0.0001) and calcium x phosphorus products (P < 0.0001). Moreover, between the low-BUN (<70 mg/dL, N = 19) group and high-BUN (> or =70 mg/dL) group, significant differences were detected in the expression of OPN (P = 0.0039) and the levels of BUN (P = 0.0002), serum phosphorus (P = 0.0002) and calcium x phosphorus products (P = 0.0003). We have shown that hyperphosphatemia or azotemia is associated with the expression of OPN in VSMCs in patients with ESRD.

Carotid Plaques and Their Predictive Value for Cardiovascular Disease and All-Cause Mortality in Hemodialysis Patients Considering Renal Transplantation: A Decade Follow-Up

BACKGROUND

Carotid plaque formation is very common in dialysis patients. The prognostic value of plaques, both calcified and noncalcified, rarely was investigated prospectively in these patients. By using a carotid plaque score, this study aims to determine the risk for combined cardiovascular disease (CVD) events and all-cause mortality in 165 hemodialysis patients in a long-term follow-up considering phases of renal transplantation.

METHODS

Baseline carotid ultrasonography was performed in 165 hemodialysis patients to screen for carotid plaques. Patients subsequently were followed up for a period up to 13 years (average, 86 months). Because of biases associated with renal transplantation, 3 methods of multivariate analysis were compared by using Cox proportional hazards regression models.

RESULTS

Plaques were present in 107 of 165 patients (65%). During the observation period, 50 patients (30%) experienced a combined CVD event, 95 patients (58%) died, and 79 patients (48%) underwent at least 1 renal transplantation. Mean plaque score differed significantly between patients who reached an end point and those who did not (CVD events, 3.1 +/- 2.7 versus 2.0 +/- 2.4; P = 0.01; all-cause mortality, 3.5 +/- 2.6 versus 0.9 +/- 1.3; P < 0.001). Plaque score entered all 3 tested Cox regression models for CVD events and all-cause mortality. The lowest statistical power was associated with censoring at the time of renal transplantation. Not considering transplantation at all neglected a major change in risk.

CONCLUSION

We identified carotid plaque score and treatment modality as highly significant predictors for CVD events and all-cause mortality.

Collagen type-I degradation is related to arterial stiffness in hypertensive and normotensive subjects

Although arterial stiffness is an independent cardiovascular risk factor associated with both aging and hypertension, relatively little is known regarding the structural changes in the vessel wall that occur with vessel stiffening. We determined if collagen type-I metabolism is related to arterial stiffening in both hypertensive and normotensive subjects. Arterial stiffness was assessed by aortic pulse wave velocity (PWV) and augmentation index (AIx) in 46 subjects (48.7 +/- 2 years, 32 hypertensives) and related to circulating markers of collagen type-I turnover. Collagen synthesis was assessed by the measurement of carboxy-terminal peptide of procollagen type-I (PIP) and collagen degradation by the measurement of carboxy-terminal telopeptide of collagen type-I (ICTP), by quantitative immunoassay. Matrix metalloproteinase-1 (MMP-1) and the tissue inhibitor of metalloproteinase-1 (TIMP-1) were also quantified by immunoassay. The ratio of collagen type-I synthesis to degradation was negatively correlated with both PWV (P<0.05) and AIx (P<0.05), whereas plasma MMP-1 levels displayed a positive correlation with both PWV (P<0.01) and AIx (P<0.01), after adjustment for age and mean arterial pressure. The relationship between collagen type-I turnover and arterial stiffness was similar in both the normotensive and hypertensive subjects. Although circulating markers of collagen synthesis were increased in the hypertensive subjects, this was not related to arterial stiffness. Collagen type-I degradation is increased in relation to collagen type-I synthesis in subjects with stiffer arteries. Matrix metalloproteinase-1, the enzyme responsible for collagen type-I degradation, is positively related to both large elastic and muscular artery stiffness in normotensive and hypertensive subjects.

Molecular mechanisms of vascular calcification: lessons learned from the aorta

Vascular calcification increasingly afflicts our aging and dysmetabolic population. Once considered a passive process, it has emerged as an actively regulated form of calcified tissue metabolism, resembling the mineralization of endochondral and membranous bone. Executive cell types familiar to bone biologists, osteoblasts, chondrocytes, and osteoclasts, are seen in calcifying macrovascular specimens. Lipidaceous matrix vesicles, with biochemical and ultrastructural "signatures" of skeletal matrix vesicles, nucleate vascular mineralization in diabetes, dyslipidemia, and uremia. Skeletal morphogens (bone morphogenetic protein-2 (BMP) and BMP4 and Wnts) divert aortic mesoangioblasts, mural pericytes (calcifying vascular cells), or valve myofibroblasts to osteogenic fates. Paracrine signals provided by these molecules mimic the epithelial-mesenchymal interactions that induce skeletal development. Vascular expression of pro-osteogenic morphogens is entrained to physiological stimuli that promote calcification. Inflammation, shear, oxidative stress, hyperphosphatemia, and elastinolysis provide stimuli that: (1) promote vascular BMP2/4 signaling and matrix remodeling; and (2) compromise vascular defenses that limit calcium deposition, inhibit osteo/chondrogenic trans-differentiation, and enhance matrix vesicle clearance. In this review, we discuss the biology of vascular calcification. We highlight how aortic fibrofatty tissue expansion (adventitia, valve interstitium), the adventitial-medial vasa, vascular matrix, and matrix vesicle metabolism contribute to the regulation of aortic calcium deposition, with greatest emphasis placed on diabetic vascular disease.

Arterial Stiffness, Isolated Systolic Hypertension, and Cardiovascular Risk in the Elderly

Isolated systolic hypertension is an important cardiovascular risk factor in the elderly. In addition to systolic blood pressure, pulse pressure, pulse wave velocity, and carotid wave reflections are also strong cardiovascular risk factors in the elderly, as a consequence of the two main determinants of systolic hypertension: increased arterial stiffness and early wave reflections. Taken together, all these findings should help to optimize drug treatment, which has been shown to produce important but thus far insufficient beneficial effects on cardiovascular morbidity and mortality.

Preventing end-stage renal disease in diabetic patients - dual blockade of the renin-angiotensin system (Part II)

Diabetic nephropathy is a major cause of diabetes related morbidity and mortality. The first part of the current review was published in the last issue of this journal and discussed the important role of the renin-angiotensin system (RAS) in diabetic nephropathy and the genetic influence on development of endstage renal disease (ESRD) in diabetic patients. This second part of the review focus on the potential improvement of the current treatment strategy to slow down the loss of kidney function using dual blockade of the RAS with both ACE-inhibitors (ACE-I) and angiotensin II receptor blockers (ARBs). Substantial evidence from short-term studies using surrogate endpoints indicates a beneficial impact of dual blockade of the RAS, not obtainable with single agent blockade alone, both in diabetic and non-diabetic renal disease. This conclusion has been confirmed and extended in a longterm trial with regard to prevention of ESRD in non-diabetic renal disease. Results indicate that dual blockade of the RAS may further slow down, but not arrest progressive loss of renal function. However, studies defining the optimal dose of ACE-I / ARBs without additional adverse effects are essential to ensure relevant comparison with dual blockade therapy. Trials using primary renal endpoints in diabetic nephropathy are still needed, and will finally establish the role of dual blockade of the RAS in a clinical setting.

A positive correlation between homocysteine and brachial–ankle pulse wave velocity in patients with systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is associated with premature atherothrombotic complications. Hyperhomocysteinemia is considered a cardiovascular risk factor. Increased vascular stiffness may increase cardiovascular mortality. Pulse wave velocity (PWV) is a noninvasive method of analyzing vascular stiffness in the assessment of atherosclerosis. The objective of this study was to identify the relationship between plasma homocysteine levels and brachial-ankle pulse wave velocity (baPWV) measurement in SLE. Plasma homocysteine, baPWV, ankle-brachial index, blood pressure, C3, C4, anticardiolipin antibody (aCL), and anti-double-stranded DNA antibodies were determined in a total of 58 female patients with SLE. The control group comprised 32 age-matched healthy females. In addition, all patients were further classified into subgroups according to the presence of aCL (SLE/aCL+, n=27 vs SLE/aCL-, n=31) to determine the effect of aCL on the tested variables. The mean values for plasma homocysteine and baPWV were 13.19 mumol/l and 1,482 cm/s, respectively. Plasma homocysteine levels were significantly elevated in SLE patients when compared with the healthy controls. SLE patients with aCL had a significantly higher plasma homocysteine level than those without aCL. A significant positive correlation between plasma homocysteine and baPWV was found in patients with SLE (r=0.335, P=0.028, n=58). Plasma homocysteine also significantly correlated with right baPWV in all SLE patients (r=0.371, P=0.014, n=58) and in the SLE/aCL+ group (r=0.523, P=0.031, n=27). These findings indicate a possible link between plasma homocysteine and baPWV in SLE. In conclusion, SLE patients had an increased level of plasma homocysteine, and this phenomenon appeared to be related to vascular stiffness.

Effect of atorvastatin on regional arterial stiffness in patients with type 2 diabetes mellitus

OBJECTIVE

A statin, a potent lipid-lowering drug, improves pain-free walking distance in patients with peripheral arterial disease (PAD) without increasing the ankle-brachial pressure index (ABI). Arterial stiffness affects the blood flow of peripheral arteries. The purpose of this study was to evaluate the effect of cholesterol-lowering with atorvastatin on regional arterial stiffness in patients with type 2 diabetes mellitus.

METHODS

The subjects were 22 type 2 diabetic patients with hypercholesterolemia, who received atorvastatin at a daily dose of 10 mg for 6 months. Before and after the treatment with atorvastatin, we measured pulse wave velocity (PWV) in the heart-brachial, heart-carotid, heart-femoral and femoral-ankle segments.

RESULTS

Following treatment with atorvastatin, femoral-ankle PWV showed a significant reduction. The PWV of other arterial segments tended to decrease, although the changes were not statistically significant. We found no significant changes in blood pressure, heart rate, ABI, or plasma concentrations of glucose, L-arginine and asymmetric dimethylarginine (ADMA), an endogenous inhibitor of endothelial function.

CONCLUSIONS

Atorvastatin treatment was associated with an improvement in the stiffness of leg arteries in type 2 diabetes mellitus. This may partly explain the statin-mediated improvement of walking performance in those with PAD.

Impact of Type A Behavior on Brachial-Ankle Pulse Wave Velocity in Japanese

Pulse wave velocity (PWV) is the velocity of a pulse wave traveling a given distance between 2 sites in the arterial system, and is a well-known indicator of arteriosclerosis. Brachial-ankle PWV (baPWV) is a parameter more simple to obtain, compared with the conventional PWV, and is an easy and effective means of evaluating arteriosclerosis. BaPWV can be obtained by only wrapping the four extremities with blood pressure cuffs, and it can be easily used to screen a large number of subjects. Type A behavior has been confirmed as an independent risk factor for the development of coronary heart disease. To examine the relationship between Type A behavior and arteriosclerosis, 307 normal Japanese subjects were classified into either a Type A group (n = 90) or a non-Type A group (n = 217) by using Maeda's Type A Scale. BaPWV was evaluated using a PWV diagnosis device. The baPWV in the Type A group was significantly higher than that obtained in the non-Type A group. The baPWV showed a positive correlation with age both in the Type A group and in the non-Type A group; however, the straight-line regression slope of baPWV versus age in the Type A group was significantly larger than that in the non-Type A group. Therefore, our results suggest that arteriosclerosis might be promoted earlier in subjects expressing the Type A behavior pattern. Type A behavior pattern is confirmed as a risk factor for arteriosclerosis, and may increase the risk of the cardiovascular disease related to arteriosclerosis.

Arteriosclerosis, vascular calcifications and cardiovascular disease in uremia

PURPOSE OF REVIEW

Arterial calcification in chronic kidney disease (CKD) is associated with increased cardiovascular risk. The mechanisms responsible for arterial calcification include alterations of mineral metabolism and expression of mineral-regulating proteins.

RECENT FINDINGS

Arterial calcification is similar to bone formation, involving differentiation of vascular smooth muscle cells (VSMCs) into phenotypically distinct osteoblast-like cells. Elevated phosphate and/or calcium trigger a concentration-dependent increase of calcium precipitates in VSMC in vitro. The calcification is initiated by VSMC release of membrane-bound matrix vesicles and formation of apoptotic bodies. The presence of serum prevents these changes, indicating the presence of calcification inhibitors. Arterial calcification occurs in two sites: the tunica intima and tunica media. Intimal calcification is a marker of atherosclerotic disease and is associated with arterial stenotic lesions. Medial calcification influences outcome by promoting arterial stiffening whose principal consequences are left-ventricular hypertrophy and altered coronary perfusion. Aortic stiffness is an independent predictor of all-cause and cardiovascular mortality in CKD patients. Age, duration of dialysis, smoking and diabetes are risk factors for the development of arterial calcification in end-stage renal disease. Oversuppression of parathyroid hormone and low bone turnover potentiate the development of arterial calcification.

SUMMARY

Arterial disease in CKD patients is characterized by extensive calcification. Evidence has accumulated pointing to the active and regulated nature of the calcification process. Elevated phosphate and calcium may stimulate sodium-dependent phosphate cotransport involving osteoblast-like changes in cellular gene expression. Arterial calcification is responsible for stiffening of the arteries with increased left-ventricular afterload and abnormal coronary perfusion as the principal clinical consequences.

Large-artery stiffness, hypertension and cardiovascular risk in older patients

Research studies on hypertension have, so far, generally focused on vascular resistance and small arteries. The high prevalence of systolic hypertension in patients older than 50 years and the development of noninvasive Doppler and echotracking techniques have made it possible to determine large-artery stiffness with a high degree of reproducibility. Increased arterial stiffness and disturbed wave reflections are the basis for understanding reduced aortic elasticity and systolic hypertension, particularly in older people. This hemodynamic pattern results from mechanical factors and other pressure-independent risk factors, such as diabetes mellitus, renal failure, obesity and severe atherosclerosis. Distinct phenotypes of arterial stiffness and pulse pressure result from specific gene polymorphisms, such as those related to the renin-angiotensin system. The roles of arterial stiffness and wave reflections in hypertension have been elucidated by modern interpretations of the blood-pressure curve in relation to its propagation, mechanisms of systolic-blood-pressure amplification, and the pulse-pressure amplitude. New predictors of cardiovascular risk have been identified, such as increased pulse pressure and pulse-wave velocity, and disturbed wave reflections, all of which are independent predictors of cardiovascular risk that are more powerful than either systolic or diastolic blood pressure alone. Therapeutic trials are investigating ways to reduce stiffness, and thereby allow the selective reduction of systolic and pulse pressure in hypertensive patients with or without advanced renal failure. Modern pharmacologic agents need to be identified, which could reduce systolic hypertension in patients older than 50 years. Here we discuss the structural and functional factors that influence arterial stiffness, wave reflections and pulse pressure in hypertension, as well as their related roles in cardiovascular risk.

Serum osteoprotegerin levels are associated with inflammation and pulse wave velocity

OBJECTIVE

We examined the association between serum osteoprotegerin (OPG) levels, systemic inflammation and arterial stiffness in normal and diabetic patients.

PATIENTS AND MEASUREMENTS

The study subjects comprised 49 newly diagnosed diabetic patients and 72 age- and sex-matched normal glucose controls. Anthropometric parameters, blood pressure, fasting blood glucose (FBG), lipid profiles, serum OPG, high-sensitive C-reactive protein (hsCRP), interleukin-6 (IL-6) and brachial-ankle pulse wave velocity (baPWV) were measured.

RESULTS

Serum OPG levels (6.1 +/- 1.4 vs. 5.4 +/- 1.3 pmol/l, P = 0.011) and baPWV (1562 +/- 354 vs. 1399 +/- 257 cm/s, P = 0.004) were significantly higher in the diabetic group than in the normal glucose group. Serum OPG levels in normal and diabetic patients correlated significantly with systolic blood pressure (r = 0.20, P = 0.035), FBG (r = 0.30, P = 0.002), right baPWV (r = 0.22, P = 0.021), left baPWV (r = 0.26, P = 0.006), homeostasis model assessment insulin resistance (HOMA-IR) (r = 0.19, P = 0.045), IL-6 (r = 0.32, P = 0.001) and hsCRP (r = 0.21, P = 0.027) after adjusting for age and sex. Multiple regression analysis showed that serum OPG level was significantly associated with age, FBG, IL-6, systolic blood pressure, triglyceride and hsCRP (R(2) = 0.299).

CONCLUSIONS

In summary, serum OPG and baPWV levels are elevated in diabetic patients and serum OPG levels are significantly associated with inflammation and arterial stiffness.

Arterial stiffness in renal patients: an update

According to recent data, arterial stiffness is a major independent risk factor for cardiovascular morbidity and mortality in both the general and renal populations. Because of several factors (vascular calcifications among them), large arteries are stiffer in patients with chronic kidney disease compared with the nonrenal population, contributing to the enormous cardiovascular mortality in renal patients. This review briefly analyzes methods for determination of arterial stiffness, focusing on 2 parameters, pulse wave velocity and the augmentation index, particularly useful in assessing arterial compliance in renal patients. Effects of different methods of renal replacement therapy on arterial wall properties also are discussed. Finally, the most promising novel and/or potential therapies regarding reduction of arterial stiffness in renal patients are reviewed.

Low doses of losartan and trandolapril improve arterial stiffness in hemodialysis patients

BACKGROUND

Hemodialysis patients have uremic dyslipidemia, represented by elevated serum intermediate-density lipoprotein cholesterol (IDL-C) levels, and an increased cardiovascular mortality rate. This study was performed to determine the low-dose effects of the angiotensin II receptor blocker losartan and the angiotensin-converting enzyme inhibitor trandolapril on pulse wave velocity (PWV), which predicts cardiovascular morbidity and mortality in hemodialysis patients.

METHODS

Serum lipid levels and PWV were monitored for 12 months in 64 hemodialysis patients who were administered low doses of losartan or trandolapril or a placebo.

RESULTS

At the start of the study, there were no differences in patient characteristics among the 3 groups. PWV tended to increase in the placebo group during the 12-month study period, but decreased significantly in the losartan and trandolapril groups, and decreases in PWV were similar in the losartan and trandolapril groups. There were no changes in blood pressure, hematocrit, erythropoietin dose, ankle-brachial index, serum lipid levels, serum 8-isoprostane levels, or serum C-reactive protein levels during the 12-month study period, but there was an increase in serum triglyceride levels in the losartan group and a decrease in serum IDL-C levels in the losartan and trandolapril groups.

CONCLUSION

In hemodialysis patients, trandolapril is as effective as losartan in decreasing PWV independent of its depressor effect and in suppressing elevated IDL-C levels. Long-term blockade of the renin-angiotensin system may have a beneficial effect on the acceleration of atherosclerosis and uremic dyslipidemia.

Stepwise increase in arterial stiffness corresponding with the stages of chronic kidney disease

BACKGROUND

Patients with end-stage renal disease on maintenance dialysis therapy have a high prevalence of cardiovascular risk factors and cardiovascular disease (CVD). A similar finding is noted in patients with chronic kidney disease (CKD). The important contributors are premature and accelerated atherosclerosis and vascular calcification. We assessed the severity of arterial stiffness in 102 patients with CKD by using pulse wave velocity (PWV) and sought to identify associated risk factors.

METHODS

PWV was measured by calculating the distance traveled by the flow wave and divided by the time delay. Correlations between PWV and traditional cardiovascular risk factors, estimated glomerular filtration rate (GFR) per 1.73 m2 , blood pressure (BP), and pulse pressure (PP) were analyzed.

RESULTS

PWV values in patients with CKD stages 1 to 2 and the age-matched control group were similar. There was a significant trend for a stepwise increase in PWV corresponding to advance in CKD stage (P < 0.0001). Univariate linear regression analysis showed that age, prior CVD, diabetes, hypertension, any high risk, estimated GFR per 1.73 m2 , systolic BP, and PP correlated with PWV. In the multivariate model, decreased estimated GFR per 1.73 m2 and increased systolic BP were independently associated with increased PWV in patients with CKD (model R 2 = 0.539; P < 0.0001).

CONCLUSION

This is the first study to show a greater PWV in patients with more advanced CKD from stages 1 to 5. Estimated GFR per 1.73 m2 and systolic BP were the major clinical determinants of arterial stiffness in patients with CKD independent of conventional risk factors for CVD.

Increased arterial stiffness in children on haemodialysis

BACKGROUND

Measures of aortic stiffness--aortic pulse wave velocity (PWV) and augmentation index (AIx)--have been shown to be powerful predictors of survival in adult haemodialysis (HD) patients. Very few data have been reported regarding arterial stiffness in paediatric renal populations.

METHODS

PWV and aortic AIx were determined from contour analysis of arterial waveforms recorded by applanation tonometry using a SphygmoCor device in 14 children on HD (age = 14.1 years) and in 15 age, height matched children controls.

RESULTS

Pre-HD AIx (29.7 +/- 15.4%) and PWV (6.6 +/- 1.0 m/s) were significantly higher compared with children controls (8.3 +/- 8.0% and 5.4 +/- 0.6 m/s, respectively, P < 0.0001). The only significant difference between normal and HD children was BP level: 103/61 vs 114/72 mmHg, P < 0.05. In children of HD patients, a multiple linear regression model including BP, age, height, weight, Ca and P levels as independent variables accounted for 57% of the variability in AIx. Dialysis had no impact on AIx (post-HD: 28.5 +/- 12.7%) or on PWV (post-HD: 6.7 +/- 0.8 m/s).

CONCLUSIONS

We show, in this first-ever report of increased arterial stiffness in children on dialysis, that end-stage renal disease is associated with abnormalities in arterial wall elastic properties, comparable with adult levels, even in childhood. Most importantly, the absence of a discernible amelioration with dialysis implies that purely structural and not functional alterations lie behind the increased arterial stiffness.

Impact of Brachial-Ankle Pulse Wave Velocity and Ankle-Brachial Blood Pressure Index on Mortality in Hemodialysis Patients

BACKGROUND

Pulse wave velocity (PWV) and ankle-brachial blood pressure index (ABPI) are markers for atherosclerosis, and each predicts mortality in patients undergoing hemodialysis. However, there have been no studies in the past that compared head-to-head the clinical validity of these 2 parameters. Compared with conventional aortic PWV, brachial-ankle PWV (baPWV) is considered simple and thereby easily applicable to clinical use.

METHODS

To clarify the relationship between baPWV and ABPI and assess their prognostic values, we analyzed 785 hemodialysis patients with a mean age of 60.2 +/- 12.5 (SD) years for whom ABPI and baPWV at baseline had been measured simultaneously and who were followed up for 33.8 +/- 10.8 months.

RESULTS

Of 785 patients, 131 deaths were recorded. In Kaplan-Meier analysis, all-cause mortality was progressively and significantly greater from the lowest quartile of baPWV onward (log-rank test, 41.8; P < 0.001). However, in Cox proportional hazards analysis, the impact of baPWV was insignificant when ABPI was included as a covariate. ABPI maintained strong predictive power in this model. When patients who had advanced peripheral arterial occlusive disease (ABPI < 0.9) were excluded from analysis, patients with the highest quartile of baPWV had significantly increased hazard ratios of all-cause (hazard ratio, 4.08; 95% confidence interval, 1.46 to 11.43; P < 0.007) and cardiovascular (hazard ratio, 7.03; 95% confidence interval, 1.49 to 33.08; P < 0.014) mortality. The predictive power of baPWV in this population was independent from other covariates associated with atherosclerotic disorders.

CONCLUSION

In a head-to-head comparison, ABPI, but not baPWV, showed strong power in predicting the mortality of hemodialysis patients. However, baPWV was useful to pick a high-risk population in patients with ABPI greater than 0.9. Thus, screening hemodialysis patients by means of baPWV and ABPI provides complementary information in identifying a high-risk population.

Higher brachial-ankle pulse wave velocity is associated with more advanced carotid atherosclerosis in end-stage renal disease

Brachial-ankle pulse wave velocity is a new measure of arterial stiffness. We examined whether higher brachial-ankle pulse wave velocity is associated with more advanced carotid atherosclerosis and left ventricular hypertrophy in patients with end-stage renal disease, and whether this effect would be mediated by the influence of wave reflection on central arterial pressure. In 68 patients with end stage renal disease, we examined blood pressures, brachial-ankle pulse wave velocity and the augmentation index of the left common carotid artery, a measure of the impact of wave reflection on the systolic peak in central arteries. The degree of carotid atherosclerosis was quantified by a plaque score and maximum intimal-medial thickness. Echocardiography was used to determine the left ventricular mass index. In simple regression analysis, brachial-ankle pulse wave velocity was correlated with both plaque score and maximum intimal-medial thickness (r = 0.420, p < 0.001 and r = 0.452, p < 0.0005, respectively) but not with left ventricular mass index. Multiple regression analysis was performed with the plaque score or maximum intimal-medial thickness as the dependent variable and brachial-ankle pulse wave velocity and known clinical risk factors as the independent variables. The brachial-ankle pulse wave velocity was an independent risk factor for both plaque score (beta = 0.006, p = 0.004) and maximum intimal-medial thickness (beta = 0.008, p = 0.04). Independent risk factors for left ventricular mass index were left ventricular diastolic dimension (beta = 3.509, p = 0.000007) and augmentation index (beta = 0.580, p = 0.04). The brachial-ankle pulse wave velocity was unrelated to augmentation index in patients with end stage renal disease. In conclusion, higher brachial-ankle pulse wave velocity was found to be a risk factor for carotid atherosclerosis in patients with end-stage renal disease; this effect was independent of the influence of wave reflection on central arterial pressure. The brachial-ankle pulse wave velocity was unrelated to left ventricular structure.

Validity and reproducibility of arterial pulse wave velocity measurement using new device with oscillometric technique: a pilot study

BACKGROUND

Availability of a range of techniques and devices allow measurement of many variables related to the stiffness of large or medium sized arteries. There is good evidence that, pulse wave velocity is a relatively simple measurement and is a good indicator of changes in arterial properties. The pulse wave velocity calculated from pulse wave recording by other methods like doppler or tonometry is tedious, time-consuming and above all their reproducibility depends on the operator skills. It requires intensive resource involvement. For epidemiological studies these methods are not suitable. The aim of our study was to clinically evaluate the validity and reproducibility of a new automatic device for measurement of pulse wave velocity that can be used in such studies.

METHODS

In 44 subjects including normal healthy control and patients with coronary artery disease, heart brachial, heart ankle, brachial ankle and carotid femoral pulse wave velocities were recorded by using a new oscillometric device. Lead I and II electrocardiogram and pressure curves were simultaneously recorded. Two observers recorded the pulse wave velocity for validation and one observer recorded the velocity on two occasions for reproducibility.

RESULTS AND DISCUSSION

Pulse wave velocity and arterial stiffness index were recorded in 24 control and 20 coronary artery disease patients. All the velocities were significantly high in coronary artery disease patients. There was highly significant correlation between the values noted by the two observers with low standard deviation. The Pearson's correlation coefficient for various velocities ranged from (r = 0.88-0.90) with (p < 0.0001). The reproducibility was also very good as shown by Bland-Altman plot; most of the values were lying within 2 SD. The interperiod measurements of pulse wave velocity were also significantly correlated (r = 0.71-0.98) (P < 0.0001). Carotid-femoral pulse wave velocity was found to correlate significantly with heart brachial, heart ankle, brachial ankle pulse wave velocity and arterial stiffness index values. Reproducibility of our method was good with very low variability in both interobserver and interperiod analysis.

CONCLUSION

The new device "PeriScope" based on oscillometric technique has been found to be a simple, non-invasive and reproducible device for the assessment of pulse wave velocity and can be used to determine arterial stiffness in large population based studies.

Silent cerebral infarction predicts vascular events in hemodialysis patients

BACKGROUND

Cardiovascular disease is the leading cause of death in hemodialysis (HD) patients. We have previously reported a higher incidence of silent cerebral infarction (SCI) in HD patients compared with the control group using MRI studies. In the present study, we examined whether or not SCI could predict vascular events in HD patients.

METHODS

Cranial magnetic resonance imaging (MRI) was performed on 119 HD patients without symptomatic cerebrovascular disease. SCI was detected by MRI, and the patients were prospectively followed up. The end points of the study were the incidence of major events related to vascular events (cerebral events, cardiac events, and sudden deaths). We investigated the prognostic role of SCI in cerebral, cardiac, and vascular events by using the Kaplan-Meier method and Cox proportional hazards analysis.

RESULTS

The prevalence of SCI was 49.6% in HD patients. During a follow-up period of maximum 60 months, vascular events, which included 13 cerebral events, 5 cardiac events, and 3 sudden deaths, occurred in 21 patients. The presence of SCI was predictive for a higher cerebral and vascular morbidity compared to the absence of SCI [18.6% (N= 11) vs. 3.3% (N= 2), P= 0.0169, and 30.5% (N= 18) vs. 5.0% (N= 3), P= 0.0006, respectively]. By multivariate Cox proportional hazards analysis, SCI remained a powerful independent predictor of cerebral and vascular events (hazard ratio for cerebral events 7.33, 95% CI 1.27-42.25: for vascular events 4.48, 95% CI 1.09-18.41).

CONCLUSION

The findings of the present study indicate that the presence of SCI is a new risk factor for vascular events in HD patients.

Increased aortic stiffness in the insulin-resistant Zuckerfa/farat

Accumulating clinical evidence indicates increased aortic stiffness, an independent risk factor for cardiovascular and all-cause mortality, in type 2 diabetic and glucose-intolerant individuals. The present study sought to determine whether increased mechanical stiffness, an altered extracellular matrix, and a profibrotic gene expression profile could be observed in the aorta of the insulin-resistant Zucker fa/fa rat. Mechanical testing of Zucker fa/fa aortas showed increased vascular stiffness in longitudinal and circumferential directions compared with Zucker lean controls. Unequal elevations in developed strain favoring the longitudinal direction resulted in a loss of anisotropy. Real-time quantitative PCR and immunohistochemistry revealed increased expression of fibronectin and collagen IVα3in the Zucker fa/fa aorta. In addition, expression of transforming growth factor-β and several Smad proteins was increased in vessels from insulin-resistant animals. In rat vascular smooth muscle cells, 12–18 h of exposure to insulin (100 nmol/l) enhanced transforming growth factor-β1 mRNA expression, implicating a role for hyperinsulinemia in vascular stiffness. Thus there is mechanical, structural, and molecular evidence of arteriosclerosis in the Zucker fa/fa rat at the glucose-intolerant, hyperinsulinemic stage.

Carbohydrate metabolism in uraemia

PURPOSE OF REVIEW

Most uraemic patients are insulin resistant. This review focuses on the occurrence, mechanisms and consequences of this insulin resistance. Hypoglycaemia is also possible in a minority of uraemic patients; its causes are discussed at the end of the review.

RECENT FINDINGS

Insulin resistance is detectable when the glomerular filtration rate is below 50 ml/min per 1.73 m in non-diabetic uraemic individuals. Uraemia can alter insulin sensitivity even in diabetic patients; familial insulin resistance may favour the occurrence of diabetic nephropathy. Although reduced glucose non-oxidative disposal is the most evident defect of carbohydrate metabolism, abnormal glucose oxidation, endogenous glucose production and insulin secretion are also contributors. The accumulation of nitrogenous compounds is the most important mechanism of a specific state of insulin resistance in uraemia. Their identification is progressing, particularly in the field of carbamoylated amino acids. The consequences of chronic renal failure such as anaemia, metabolic acidosis and secondary hyperparathyroidism also indirectly play a role.

SUMMARY

The treatment of uraemia by renal replacement therapies or low-protein diets improves insulin sensitivity. However, patients still have a high cardiovascular risk. The identification of the accumulating molecular species that specifically alter insulin sensitivity is therefore of great interest. The favourable effect of non-specific insulin sensitizers such as glitazone may also help to reduce this risk.

Calcaneal osteopenia is a new marker for arterial stiffness in chronic hemodialysis patients

BACKGROUND

A high frequency of simultaneous low estimated bone mineral density (BMD) and atherosclerotic vascular disease is found in chronic dialysis patients. The degree of BMD may be closely related to the severity of atherosclerosis in dialysis patients. The purpose of this study was to determine the association of estimated BMD with severity of atherosclerosis using popular economical non-invasive strategies in chronic dialysis patients.

METHODS

This cross-sectional design study included 58 subjects receiving maintenance hemodialysis (HD) therapy. The mean age was 68 +/- 12 years (range 39-93), 22 subjects were female, and 26 subjects (45%) had diabetic nephropathy. The brachial-ankle pulse wave velocity (baPWV) and estimated BMD, using calcaneal quantitative ultrasound measurements of the osteo-sono index (OSI) were measured in all of the subjects.

RESULTS

The mean levels of OSI and baPWV were 2.3 +/- 0.3 and 21 +/- 5 m/s, respectively. Based on single variable regression analysis, the C-reactive protein concentration correlated with baPWV (r = 0.272, p = 0.039), and the serum albumin concentration was inversely correlated with baPWV (r = -0.318, p = 0.015). In addition, OSI had a strong negative correlation with baPWV (r = -0.470, p = 0.0002). To identify the independent factors correlating with baPWV, multivariate regression analysis was performed using confounding variables which had significant association in univariate analysis. OSI and diabetic nephropathy were found to be significant independent parameters.

CONCLUSION

Calcaneal OSI, a surrogate marker for estimated BMD, has a strong ability to predict the severity of arterial stiffness independent of classical risk factors and markers of inflammation and malnutrition.

Carotid stiffness and the risk of new vascular events in patients with manifest cardiovascular disease. The SMART study

AIMS

To study whether arterial stiffness is related to risk of new vascular events in patients with manifest arterial disease and to examine whether this relation varies between patients who differ with respect to baseline vascular risk, arterial stiffness, or systolic blood pressure (SBP).

METHODS AND RESULTS

The study was performed in the first consecutive 2183 patients with manifest arterial disease enrolled in the SMART study (Second Manifestations of ARTerial disease), a cohort study among patients with manifest arterial disease or cardiovascular risk factors. Common carotid distension (i.e. the change in carotid diameter in systole relative to diastole) was measured at baseline by ultrasonography. With the distension, several stiffness parameters were determined. In the entire cohort, none of the carotid artery stiffness parameters was related to the occurrence of vascular events. However, decreased stiffness was related to decreased vascular risk in subjects with low baseline SBP. The relation of carotid stiffness with vascular events did not differ between tertiles of baseline risk and carotid stiffness.

CONCLUSION

Carotid artery stiffness is no independent risk factor for vascular events in patients with manifest arterial disease. However, in patients with low SBP, decreased carotid stiffness may indicate a decreased risk of vascular events.

Alteration of proximal aorta biophysical properties in patients with end stage renal disease

OBJECTIVE

To present a novel, non-invasive echocardiographic application to assess the structural and functional properties of the complex composition of the proximal aorta in patients with end stage renal disease (ESRD).

METHODS

71 haemodialysis patients (mean (SD) age 61.3 (9.3) years, dialysis duration 79.2 (51.6) months) and 62 age matched controls were studied. From the suprasternal view, the distance between ascending and descending aorta was measured with two dimensional ultrasound. The aortic flow wave transit time was measured with pulsed wave Doppler. M mode echocardiography, with simultaneous blood pressure estimates, was used to assess the diameters of the aortic annulus and of the ascending aorta. Pulse pressure, pulse wave velocity (PWV), pressure strain elastic modulus, characteristic impedance, and beta index were calculated.

RESULTS

Patients had increased pulse pressure (68.0 (7.2) v 51.4 (5.0) mm Hg, p < 0.001), PWV (6.1 (1.1) v 3.9 (0.6) m/s, p < 0.001), characteristic impedance (174 (58) v 111 (31) m/s.cm2, p < 0.001), pressure strain elastic modulus (872 (254) v 541 (140) mm Hg, p < 0.001), and beta index (8.9 (3.4) v 5.5 (1.4), p < 0.001) compared with controls. In patients PWV was correlated with age and time on haemodialysis (r = 0.44, p < 0.001, and r = 0.51, p < 0.001, respectively).

CONCLUSION

A novel application of duplex ultrasound of the proximal aorta showed that patients with ESRD have impaired proximal aortic function compared with controls. The data indicate that these non-invasive measurements can be used to describe status and change in aortic biophysical properties and may be used as a marker for cardiovascular disease risk.

C-reactive protein is a significant predictor of vascular calcification of both aorta and hand arteries

Although evidence has accumulated indicating a close relationship between inflammation and atherosclerosis, the relationship between inflammation and vascular calcification in patients with chronic renal failure is unclear. In the present study, the relationship between C-reactive protein (CRP) and vascular calcification in dialysis patients was examined. Vascular calcification of the aorta and hand arteries of 512 hemodialysis patients without significant infection (age 58.8 +/- 10.1 y; 305 men, 207 women) were examined by roentgenography of the lateral abdomen and hands, respectively. Patients with a mean CRP level greater than 1.0 mg/L (n = 254) were older than those with a CRP level less than or equal to 1.0 mg/L (n = 258) and had a longer duration of dialysis, lower serum albumin level, and higher phosphate level ( P < .01, P < .05, P < .001, and P < .01, respectively). Prevalence of vascular calcification of aorta and hand arteries in the former group was significantly higher than in the latter (65.0% versus 43.8% for aorta, P < .0001; and 25.0% versus 14.7% for hand arteries, P < .01). In a multivariate logistic regression analysis adjusted for age, hemodialysis duration, sex, levels of calcium and phosphate, and presence of diabetes, CRP level was a significant predictor for the presence of aortic calcification (odds ratio for highest versus lowest quartile, 2.669; 95% confidence interval, 1.539-5.421, P = .0010) and of calcification of hand arteries (odds ratio, 2.243; 95% confidence interval, 1.039-4.841; P = .0395). In conclusion, the present study shows that increased levels of CRP are significantly associated with the presence of vascular calcification in both aorta and hand arteries (ie, with both atheromatous and medial forms of calcification), indicating evidence for a relationship between inflammation and vascular calcification in hemodialysis patients.

Stiffness of capacitive and conduit arteries: prognostic significance for end-stage renal disease patients

The aorta is the principal capacitive element of the arterial tree and its increased stiffness, determined by measurement of aortic pulse wave velocity (PWV), is a strong independent predictor of cardiovascular mortality in the general population and end-stage renal disease (ESRD) patients. Whether stiffness of ESRD patients' peripheral arteries has the same prognostic value has never been investigated. A cohort of 305 ESRD patients was followed for 70+/-49 months (mean+/-SD). Ninety-six deaths of cardiovascular origin occurred. At entry into the study, together with standard clinical and biochemical analyses, patients' aortic, brachial artery, and femorotibial PWV were determined. Based on Kaplan-Meier survival curve analyses and Cox proportional hazards analyses, adjusted for age, pulse pressure, and clinical data, aortic PWV was a significant and independent predictor of outcome. Neither brachial artery nor femotibial artery stiffness was able to predict cardiovascular outcome. Receiver operating characteristic curve analysis of aortic PWV indicated the cutoff value of 10.75 m/s, with 84% sensitivity, 73% specificity, 87% negative predictive value, and 72% positive predictive value. These results provide evidence that, in ESRD, increased stiffness of capacitive arteries, like the aorta, is an independent strong predictor of cardiovascular mortality, whereas stiffness of peripheral conduit arteries had no prognostic value.

Aortic pulse wave velocity and albuminuria in patients with type 2 diabetes

Development of microalbuminuria increases the risk for cardiovascular disease (CVD) in type 2 diabetes. The nature of this relationship is unclear but may involve arterial stiffness, an independent risk marker for CVD mortality. Aortic pulse wave velocity (Ao-PWV) and albumin creatinine ratio (ACR) were measured in 134 consecutive patients with type 2 diabetes without overt renal impairment (serum creatinine <150 micromol/L). ACR ranged from 0.2 to 153 mg/mmol. Patients with raised ACR (>/=3 mg/mmol) had higher Ao-PWV, poorer diabetic control, and higher pulse pressure (PP) and systolic BP (SBP) (all P < 0.05) than those with normal ACR. The closest univariate associations of Ao-PWV were positively with age, duration of diabetes, SBP, PP, ACR, and insulin treatment and negatively with GFR and weight (all P < 0.01). In a multiple linear step-down regression analysis, the significant predictors of Ao-PWV were age, SBP or PP, duration of diabetes, gender, number of antihypertensive medications, and use of angiotensin-converting enzyme inhibitors or angiotensin receptor blockers, which together explained 55% of the variance of Ao-PWV. When ACR was offered in place of arterial pressure to a separate model, ACR emerged as a significant predictor of Ao-PWV. After age adjustment, patients with lower, below median GFR had higher Ao-PWV than those with GFR above the median (P = 0.043). In patients with type 2 diabetes without overt renal impairment, raised ACR is associated with higher Ao-PWV, a relationship most likely mediated by raised BP. The association of Ao-PWV with reduced GFR suggests that even modest renal dysfunction may affect the viscoelastic properties of large arteries.

Altered relationship between body fat and plasma adiponectin in end-stage renal disease

Patients with end-stage renal disease (ESRD) show an inverse association between body mass index and risk of death from cardiovascular disease. Paradoxical epidemiology may suggest some beneficial effects of body fat in ESRD. Because an antiatherogenic adipocytokine adiponectin is increased in uremic plasma, we tested a hypothesis that, in ESRD, plasma adipocytokine profile may be less atherogenic or that the relationship between body fat and adipocytokines may be altered. The subjects were 103 patients with ESRD undergoing hemodialysis and 166 healthy subjects comparable in age and sex. We measured body fat mass by dual-energy x-ray absorptiometry and plasma levels of adiponectin and leptin by enzyme-linked immunosorbent assay. The ESRD group showed a significant increase in plasma adiponectin, leptin, and adiponectin/leptin ratio than the healthy subjects. Although sex and fat mass were significant factors correlating with plasma adiponectin level in the healthy group, none of these were significantly associated with plasma adiponectin in the patients with ESRD. In contrast, leptin showed significant relationships with sex and fat mass regardless of the presence of ESRD. Plasma adiponectin correlated negatively with plasma triglycerides and positively with high-density lipoprotein cholesterol in both healthy and ESRD groups, suggesting that uremic adiponectin retains its actions in favor of its antiatherogenicity. Thus, plasma adipocytokine profile was altered in ESRD, and the effects of body fat and sex on adiponectin were less significant in the patients with ESRD.

Chronic kidney disease as a metabolic syndrome with malnutrition--need for strict control of risk factors

Patients with chronic kidney disease (CKD) have an increased risk for death from cardiovascular disease (CVD). They have multiple metabolic abnormalities that may accelerate atherosclerosis, such as hypertension, insulin resistance, and dyslipidemia, along with other CKD-related risk factors. In addition, a considerable proportion of patients with advanced stages of CKD are malnourished, presenting "metabolic syndrome with malnutrition". The presence of malnutrition/inflammation dramatically changes the apparent relationship between CVD death risk and some risk factors. For example, in stage 5 CKD patients on hemodialysis, a higher body mass index and a higher plasma cholesterol are predictors of better survival. To understand the paradoxic epidemiology, we should recognize risk factors for occurrence of CVD events and risk factors of fatality after an event. In this article, we review the unique situation of CKD, emphasizing the need of more strict control of both types of risk factors to improve survival of CKD patients.

The relation between hypoalbuminemia and compliance and intima-media thickness of carotid artery in continuous ambulatory peritoneal dialysis patients

The aim of this study was to identify the main factor affecting compliance and intima-media thickness of the elastic common carotid artery in continuous ambulatory peritoneal dialysis patients. Increased intima-media thickness and decreased arterial compliance are associated with elevated risk of cardiovascular disease. This study included 20 patients and 20 age- and sex- matched healthy control subjects. The compliance and intima-media thickness of the right common carotid artery within 1 cm to the bifurcation were measured three times using high-resolution B-mode echocardiography. Blood samples were obtained to measure levels of hemoglobin, phosphorus, total calcium, total CO2, serum albumin, C-reactive protein, serum total cholesterol, LDL- and HDL-cholesterol and triglycerides. We found that the compliance of common carotid artery was lower in the patient group than in the control group. In the patient group, the compliance of common carotid artery was positively correlated with serum albumin concentration, and intima-media thickness of common carotid artery was negatively correlated with serum albumin levels. Stepwise regression analysis showed that serum albumin concentration was independently related to the compliance of common carotid artery, suggesting hypoalbuminemia can independently give deleterious effects on the arterial wall in continuous ambulatory peritoneal dialysis patients.

Mechanisms, Significance and Treatment of Vascular Dysfunction in Type 2 Diabetes Mellitus

Endothelial dysfunction and increased arterial stiffness occur early in the pathogenesis of diabetic vasculopathy. They are both powerful independent predictors of cardiovascular risk. Advances in non-invasive methodologies have led to widespread clinical investigation of these abnormalities in diabetes mellitus, generating a wealth of new knowledge concerning the mechanisms of vascular dysfunction, risk factor associations and potential treatment targets. Endothelial dysfunction primarily reflects decreased availability of nitric oxide (NO), a critical endothelium-derived vasoactive factor with vasodilatory and anti-atherosclerotic properties. Techniques for assessing endothelial dysfunction include ultrasonographic measurement of flow-mediated vasodilatation of the brachial artery and plethysmography measurement of forearm blood flow responses to vasoactive agents. Arterial stiffness may be assessed using pulse wave analysis to generate measures of pulse wave velocity, arterial compliance and wave reflection. The pathogenesis of endothelial dysfunction in type 2 diabetes is multifactorial, with principal contributors being oxidative stress, dyslipidaemia and hyperglycaemia. Elevated blood glucose levels drive production of reactive oxidant species (ROS) via multiple pathways, resulting in uncoupling of mitochondrial oxidative phosphorylation and endothelial NO synthase (eNOS) activity, reducing NO availability and generating further ROS. Hyperglycaemia also contributes to accelerated arterial stiffening by increasing formation of advanced glycation end-products (AGEs), which alter vessel wall structure and function. Diabetic dyslipidaemia is characterised by accumulation of triglyceride-rich lipoproteins, small dense low-density lipoprotein (LDL) particles, reduced high-density lipoprotein (HDL)-cholesterol and increased postprandial free fatty acid flux. These lipid abnormalities contribute to increasing oxidative stress and may directly inhibit eNOS activity. Although lipid-regulating agents such as HMG-CoA reductase inhibitors (statins), fibric acid derivatives (fibrates) and fish oils are used to treat diabetic dyslipidaemia, their impact on vascular function is less clear. Studies in type 2 diabetes have yielded inconsistent results, but this may reflect sampling variation and the potential over-riding influence of oxidative stress, dysglycaemia and insulin resistance on endothelial dysfunction. Results of positive intervention trials suggest that improvement in vascular function is mediated by both lipid and non-lipid mechanisms, including anti-inflammatory, anti-oxidative and direct effects on the arterial wall. Other treatments, such as renin-angiotensin-aldosterone system antagonists, insulin sensitisers and lifestyle-based interventions, have shown beneficial effects on vascular function in type 2 diabetes. Novel approaches, targeting eNOS and AGEs, are under development, as are new lipid-regulating therapies that more effectively lower LDL-cholesterol and raise HDL-cholesterol. Combination therapy may potentially increase therapeutic efficacy and permit use of lower doses, thereby reducing the risk of adverse drug effects and interactions. Concomitant treatments that specifically target oxidative stress may also improve endothelial dysfunction in diabetes. Vascular function studies can be used to explore the therapeutic potential and mechanisms of action of new and established interventions, and provide useful surrogate measures for cardiovascular endpoints in clinical trials.

Relationship between brachial-ankle pulse wave velocity and cardiovascular risk factors of the metabolic syndrome

In this study, we investigated the association between brachial-ankle pulse wave velocity (baPWV), a novel non-invasive means of measuring atherosclerosis, and the cardiovascular risk factors of the metabolic syndrome. The study group comprised of 368 Koreans without history of diabetes or hypertension. Anthropometric parameters, blood pressure, fasting blood glucose (FBG), lipid profiles, ankle-brachial pressure index (ABI), and baPWV were measured in each subject. ABI and baPWV levels were higher in men than in women. ABI and baPWV levels were not correlated with each other. In women, baPWV was closely associated with the cardiovascular risk factors of the metabolic syndrome. Women with the metabolic syndrome showed higher baPWV levels compared to those without the metabolic syndrome (1540 +/- 281 versus 1312 +/- 223, P < 0.001). Multiple regression analysis showed that baPWV was significantly associated with systolic blood pressure, age, sex, waist circumference, and FBG (adjusted R2 = 0.548). The present study shows that baPWV is significantly associated with the features of the metabolic syndrome in Korean women.

Arterial stiffness and function in end-stage renal disease

Cardiovascular disease is a major cause of mortality in patients with end-stage renal disease, with damage to arteries as a major contributing factor. Arterial stiffness is a factor associated with high systolic and pulse pressure in these patients and is a strong independent factor associated with morbidity and mortality. Arterial stiffness is one of the principal factors opposing left ventricular ejection. The appropriate term to define the arterial factor(s) opposing left ventricular ejection is aortic input impedance. Aortic input impedance depends on TPR, arterial distensibility, and wave reflections. Distensibility defines the capacitive properties of arterial stiffness, whose role it is to dampen pressure and flow oscillations and to transform pulsatile flow and pressure in arteries into a steady flow and pressure in peripheral tissues. Stiffness is the reciprocal value of distensibility. These parameters are blood pressure dependent; arteries become stiffer at high pressure. While distensibility provides information about the elasticity of the artery as a hollow structure, the elastic incremental modulus characterizes the properties of the arterial wall biomaterials independent of vessel geometry. Alternatively, arterial distensibility can be evaluated by measuring pulse wave velocity, which increases with the stiffening of arteries. Arterial stiffening increases left ventricular afterload and alters the coronary perfusion. With increased pulse wave velocity, the wave reflections affects the aorta during systole, which increases systolic pressures and myocardial oxygen consumption and decreases diastolic blood pressure and coronary flow. The arterial stiffness is altered primarily in association with increased collagen content and alterations of extracellular matrix and calcification of the arterial wall. The arterial stiffening estimated by changes in aortic pulse wave velocity and intensity of wave reflections are independent predictors of survival in end-stage renal disease and in the general population. Improvement of arterial stiffening could be obtained by antihypertensive treatments as observed with calcium-channel blockers and angiotensin-converting enzyme inhibitors. Angiotensin-converting enzymes inhibitors increase AC and reduce wave reflections. It has been shown that reversibility of aortic stiffening and use of angiotensin-converting enzyme inhibitors had a favorable independent effect on survival in hypertensive patients with advanced renal disease.

Pulse wave velocity in lower-limb arteries among diabetic patients with peripheral arterial disease

OBJECTIVE

Patients with type 2 diabetes mellitus are at an increased risk of atherosclerosis including peripheral arterial disease (PAD). The purpose of this study was to examine the possible alteration in pulse wave velocity (PWV) in lower-limb arteries among diabetic patients with PAD.

METHODS

We measured brachial-ankle PWV (baPWV) using an automatic device in 101 healthy control subjects and 102 type 2 diabetic patients including those with PAD.

RESULTS

Diabetic patients without PAD showed a higher baPWV than the healthy control subjects. There was no significant difference in baPWV between the right and left legs in these groups. In contrast, among diabetic patients with PAD, baPWV was significantly lower in the affected legs than in the non-affected legs, and the reduction in baPWV was greater in those with lower ankle-brachial pressure index (ABI). In the patients with PAD who received percutaneous transluminal angioplasty, both baPWV and ABI were increased following successful vessel dilatation.

CONCLUSIONS

These results suggest that baPWV is increased in diabetic patients, whereas it is decreased in the affected legs in diabetic patients with PAD. Widening of the right-left difference in baPWV may be a novel marker of PAD.

Arterial stiffness in predialysis patients with uremia

BACKGROUND

Hemodialysis patients have advanced arterial wall stiffening as shown by increased aortic pulse wave velocity (PWV), an independent predictor of cardiovascular mortality. We compared aortic PWV of uremic patients before starting hemodialysis treatment with that of patients on maintenance hemodialysis.

METHODS

The subjects were 71 patients with end-stage renal disease (ESRD) before starting hemodialysis (predialysis group), 144 patients on maintenance hemodialysis, and 140 healthy control subjects. These three groups were all nondiabetic and comparable in age and gender.

RESULTS

The hemodialysis group had greater aortic PWV than the healthy subjects, and the predialysis patients showed a still higher value than the hemodialysis group. Multiple regression analysis in the total subjects revealed that the presence of renal failure was significantly associated with increased aortic PWV independent of age, gender, blood pressure, body mass index, smoking, high-density lipoprotein (HDL) and nonhigh-density lipoprotein (non-HDL) cholesterol levels. In contrast, hemodialysis was associated with decreased aortic PWV independent of renal failure and the other factors. Further analyses in the combined uremic patients again indicated the favorable impact of hemodialysis on aortic PWV independent of the classical risk factors, use of antihypertensive medications, including angiotensin-converting enzyme inhibitors and calcium channel blockers, hematocrit, serum calcium, phosphorus, parathyroid hormone levels, and the use of calcium carbonate. Insulin resistance using homeostasis model assessment (HOMA-IR) was associated with increased aortic PWV.

CONCLUSION

Aortic stiffening was present in uremic patients before starting hemodialysis treatment and no adverse effect of hemodialysis was observed, suggesting the important roles of renal failure and/or metabolic alterations secondary to renal failure in arterial stiffness in patients with uremia.

Effect of diabetes on uremic dyslipidemia

Elevated intermediate-density lipoprotein (IDL), a remnant lipoprotein, is an independent risk factor for atherosclerosis in patients with end-stage renal disease (ESRD). Since the presence of diabetes mellitus further increases the risk of cardiovascular mortality in ESRD, we examined the effect of diabetes on IDL among ESRD patients. The subjects were 330 healthy control subjects and 287 patients with end-stage renal disease including 80 patients with type 2 diabetes. As compared with the healthy subjects, the nondiabetic ESRD patients had increased plasma triglyceride and IDL cholesterol. Diabetic patients with ESRD showed a further increase in plasma triglyceride and IDL cholesterol compared with the nondiabetic group. However, the difference in IDL levels between the ESRD groups was no longer significant when subjects were stratified by plasma triglyceride. Plasma triglyceride was correlated with IDL cholesterol. Increased hemoglobin A(1c) was significantly associated with IDL cholesterol in a multiple regression model including age, gender, and the presence of ESRD. Such an association was no longer significant in another model including plasma triglyceride as an additional covariate. Further analysis indicated the positive effects of diabetes and hyperglycemia on plasma triglyceride. These results indicate that increased IDL in ESRD is further deteriorated in the presence of diabetes, and that the adverse effect is accounted for at least partly by hypertriglyceridemia associated with chronic hyperglycemia.

Rosiglitazone improves glucose metabolism in nondiabetic uremic patients on CAPD

BACKGROUND

Insulin resistance, a strong risk factor for atherosclerotic vascular disease, is present in uremic patients without diabetes on continuous ambulatory peritoneal dialysis (CAPD) therapy. Amelioration of insulin resistance may reduce associated long-term cardiovascular complications. The aim of the study is to investigate the effects of rosiglitazone (ROS), an insulin sensitizer, on glucose metabolism in CAPD patients without diabetes.

METHODS

Fifteen uremic patients without diabetes on CAPD therapy were enrolled. All were administered ROS, 4 mg/d, for 12 weeks. A control group consisted of 15 age- and sex-matched healthy subjects. Oral glucose tolerance test (OGTT) results, fasting glucose and insulin levels, related blood biochemistry results, and C-reactive protein (CRP), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-alpha) levels were determined before initiation and at 4 and 12 weeks of therapy. Insulin resistance was evaluated using the homeostasis model assessment method (HOMA-IR). A whole-body insulin sensitivity index (ISI) and insulinogenic index for insulin production were calculated from OGTT results.

RESULTS

CAPD patients showed significantly greater HOMA-IR and glucose intolerance compared with healthy controls. After 4 and 12 weeks of ROS therapy, there were no significant changes in body weight, blood pressure, dialysis adequacy, hemoglobin level, hemoglobin A(1c) level, liver function, lipid profile, or intact parathyroid hormone, CRP, IL-6, or TNF-alpha levels. There was a significant decrease in HOMA-IR (3.2 +/- 0.6, 2.2 +/- 0.4, and 2.1 +/- 0.4; P < 0.05). During the OGTT, there was a significant decrease in the area under the glucose curve and a significant increase in ISI (3.5 +/- 0.4, 5.0 +/- 0.7, and 5.3 +/- 0.7; P < 0.05), but no significant change in insulinogenic index.

CONCLUSION

ROS improved insulin resistance in CAPD patients without diabetes. Whether long-term use of ROS reduces cardiovascular risk needs further study.

Arterial wall stiffness is associated with peripheral circulation in patients with type 2 diabetes

The prevalence of peripheral vascular disease (PVD) in diabetic patients is manyfold higher than that of age- and sex-matched nondiabetic subjects. This study was designed to evaluate the relationship between quantitatively determined peripheral circulation in the lower extremities and arterial wall thickness or stiffness in 68 patients with type 2 diabetes. Peripheral circulation during treadmill-exercise was monitored by transcutaneous oxygen tension (TcPO2) and was expressed as percentage of post-exercise TcPO2 adjusted by that of pre-exercise (TcPO2 index). Arterial wall thickness (intima-media thickness; IMT) and stiffness (stiffness beta) were measured by ultrasonography. TcPO2 index was negatively (r=-0.350, P=0.0007) correlated with stiffness beta, not with IMT, of the femoral artery. In patients without insulin therapy (n=52), both fasting plasma insulin concentration (r=-0.323, P=0.0023) and HOMA IR, an insulin resistance index, (r=-0.281, P=0.0084) were negatively correlated with TcPO2 index. Multiple regression analyses showed that association of stiffness beta of the femoral artery or HOMA IR with the TcPO2 index was independent of other factors including age, smoking index, ankle brachial pressure index and IMT of femoral artery. Thus, arterial wall stiffness of femoral artery appears to be a major determinant of peripheral circulation in patients with type 2 diabetes.

Brachial-ankle pulse wave velocity and symptomatic cerebral infarction in patients with type 2 diabetes: a cross-sectional study

BACKGROUND

Recently a new automatic device that measures brachial-ankle pulse wave velocity using an oscillometric method has been developed. However, the practical significance of brachial-ankle pulse wave velocity measurement remains uncertain. The purpose of this study was to examine the association between brachial-ankle pulse wave velocity and symptomatic cerebral infarction in patients with type 2 diabetes.

METHODS

One thousand sixty six patients with type 2 diabetes were studied cross-sectionally. Measurements of brachial-ankle pulse wave velocity were made using the automatic device. Logistic regression analysis was used to calculate the odds ratio for cerebral infarction.

RESULTS

The presence of symptomatic cerebral infarction was confirmed in 86 patients. In these patients brachial-ankle pulse wave velocity was found to be significantly higher than in patients without cerebral infarction (18.94 +/-; 4.95 versus 16.46 +/-; 3.62 m/s, p < 0.01). The association between brachial-ankle pulse wave velocity and cerebral infarction remained significant after adjustment for traditional risk factors. There was an increasing odds ratio for each tertile of brachial-ankle pulse wave velocity, from the second tertile (odds ratio, 2.28; 95% confidence interval, 1.05 to 4.94), to the third (odds ratio, 2.53; 95% confidence interval, 1.09 to 5.86).

CONCLUSION

Overall, we conclude that an increase in brachial-ankle pulse wave velocity is associated with symptomatic cerebral infarction in patients with type 2 diabetes.