High-resolution B-mode ultrasonography in evaluation of atherosclerosis in uremia

Strong association between malnutrition, inflammation, and atherosclerosis in chronic renal failure

BACKGROUND

Atherosclerotic cardiovascular disease and malnutrition are widely recognized as leading causes of the increased morbidity and mortality observed in uremic patients. C-reactive protein (CRP), an acute-phase protein, is a predictor of cardiovascular mortality in nonrenal patient populations. In chronic renal failure (CRF), the prevalence of an acute-phase response has been associated with an increased mortality.

METHODS

One hundred and nine predialysis patients (age 52 +/- 1 years) with terminal CRF (glomerular filtration rate 7 +/- 1 ml/min) were studied. By using noninvasive B-mode ultrasonography, the cross-sectional carotid intima-media area was calculated, and the presence or absence of carotid plaques was determined. Nutritional status was assessed by subjective global assessment (SGA), dual-energy x-ray absorptiometry (DXA), serum albumin, serum creatinine, serum urea, and 24-hour urine urea excretion. The presence of an inflammatory reaction was assessed by CRP, fibrinogen (N = 46), and tumor necrosis factor-alpha (TNF-alpha; N = 87). Lipid parameters, including Lp(a) and apo(a)-isoforms, as well as markers of oxidative stress (autoantibodies against oxidized low-density lipoprotein and vitamin E), were also determined.

RESULTS

Compared with healthy controls, CRF patients had an increased mean carotid intima-media area (18.3 +/- 0.6 vs. 13.2 +/- 0.7 mm2, P < 0.0001) and a higher prevalence of carotid plaques (72 vs. 32%, P = 0.001). The prevalence of malnutrition (SGA 2 to 4) was 44%, and 32% of all patients had an acute-phase response (CRP > or = 10 mg/liter). Malnourished patients had higher CRP levels (23 +/- 3 vs. 13 +/- 2 mg/liter, P < 0.01), elevated calculated intima-media area (20.2 +/- 0.8 vs. 16.9 +/- 0.7 mm2, P < 0.01) and a higher prevalence of carotid plaques (90 vs. 60%, P < 0.0001) compared with well-nourished patients. During stepwise multivariate analysis adjusting for age and gender, vitamin E (P < 0.05) and CRP (P < 0.05) remained associated with an increased intima-media area. The presence of carotid plaques was significantly associated with age (P < 0.001), log oxidized low-density lipoprotein (oxLDL; P < 0.01), and small apo(a) isoform size (P < 0.05) in a multivariate logistic regression model.

CONCLUSION

These results indicate that the rapidly developing atherosclerosis in advanced CRF appears to be caused by a synergism of different mechanisms, such as malnutrition, inflammation, oxidative stress, and genetic components. Apart from classic risk factors, low vitamin E levels and elevated CRP levels are associated with an increased intima-media area, whereas small molecular weight apo(a) isoforms and increased levels of oxLDL are associated with the presence of carotid plaques.

Large artery structure and function in hypertension and end-stage renal disease

The cardiovascular complications in hypertension are ascribed to two different but associated alterations, namely atherosclerosis and arteriosclerosis. Whereas the former disturbs principally the conduit function and the delivery of an adequate blood flow to peripheral organs and tissues, the latter disturbs the cushioning function of large arteries, inducing an inadequate increase in systolic and pulse pressure. Arteriosclerosis represents a clinical form of accelerated ageing process and is characterized by a diffuse dilation and hypertrophy of large conduit arteries and stiffening of arterial walls. Independently from the ageing, structural changes are associated with several haemodynamic alterations such as increased in blood flow and flow velocity, and increased parietal stress due to increased arterial diameters and/or intraarterial pressure. The principal consequences of arterial stiffening are: (1) an increased left ventricular afterload with development of left ventricular hypertrophy and increased myocardial oxygen demand; (2) altered coronary perfusion and blood flow distribution; and (3) decreased perfusion reserve during haemodynamic stress. In the absence of controlled studies, it is difficult to propose therapeutic interventions aimed to prevent or treat arterial abnormalities in hypertensive patients. It has been shown that long-term administration of either calcium channel blockers and angiotensin converting enzyme inhibitors led to an improvement of vessel wall elasticity. Nevertheless, these studies did not conclude whether the improvement of elastic properties were due only to decrease in blood pressure or to alterations in intrinsic properties of arterial walls. More investigations should be necessary to investigate this important problem.

Effect of hyperparathyroidism on arterial distensibility in renal transplant recipients

BACKGROUND

The cushioning function of the arterial system is altered in patients with end-stage renal failure. The role of hyperparathyroidism for the altered vessel wall properties of large arteries not known.

METHODS

To exclude the confounding effects of fluid volume changes and hypercirculation as well as uremic toxicity on vessel wall properties from those of hyperparathyroidism, the present study was conducted in 54 normotensive renal transplant recipients with good graft function, three to six months after transplantation. The vessel wall properties of the common carotid artery were investigated in 32 of them, who had increased plasma intact parathyroid hormone (iPTH) levels (136 +/- 12 ng/liter, SEM), and compared to those of 22 control recipients of same age with normal plasma iPTH levels (34 +/- 4 ng/liter). Arterial distension was measured by Doppler analysis of the vessel wall movements, blood pressure was determined by sphygmomanometry.

RESULTS

Blood pressure was 140 +/- 3/85 +/- 2 mm Hg in renal transplant recipients with hyperparathyroidism, 135 +/- 3/83 +/- 1 mm Hg in patients with normal plasma iPTH levels (NS). There was no difference in enddiastolic diameter of the common carotid artery (7.4 +/- 0.2 mm) in renal transplant recipients with hyperparathyroidism as compared with the control patients (7.3 +/- 0.2 mm; NS). Renal transplant recipients with hyperparathyroidism had a lower distension (389 +/- 27 microns vs. 486 +/- 28 microns, P < 0.05) and distensibility coefficient of the common carotid artery (15.1 +/- 1.1 10(-3)/kPa vs. DC 19.0 +/- 1.0 10(-3)/kPa, P < 0.001) when compared with the control patients. Multiple regression analysis showed that the distensibility coefficient of the common carotid artery was negatively correlated with age (P < 0.001), mean arterial blood pressure (P < 0.05) and plasma iPTH levels (P < 0.05). The effects of plasma iPTH levels were not related to serum calcium concentrations or to differences in the enddiastolic diameter of the common carotid artery.

CONCLUSIONS

The data suggest that secondary hyperparathyroidism can affect the cushioning function of larger arteries in patients with end-stage renal failure independently of high blood pressure.

Insulin resistance in non-obese, non-insulin-dependent diabetic patients with diabetic nephropathy

To investigate the association between insulin resistance and diabetic nephropathy, peripheral insulin sensitivity indices (M/I values) were evaluated via euglycemic-hyperinsulinemic clamp in 45 non-obese, non-insulin-dependent diabetic (NIDDM) subjects. The patients were divided into four groups: 18 with normoalbuminuria (urinary albumin excretion rate [AER] < 30 mg/24 h, stage I), 10 with microalbuminuria (30 < or = AER < or = 300 mg/24 h, stage II), seven with overt proteinuria (AER > 300 mg/24 h, stage III), and 10 with uremia (serum creatinine levels > 2.0 mg/dL, stage IV). There were no significant differences in age, body mass index (BMI), fasting plasma glucose, or hemoglobin A1c (HbA1c) among the four groups. No significant difference in M/I values was seen between stage I and stage II (6.30 +/- 0.73 and 5.95 +/- 0.85 mg/kg/(min per microU/mL) x 100, respectively). M/I values in the stage I and stage II groups were strongly correlated with BMI (r = -.790, P = .0001 and r = -.785, P = .007, respectively). M/I values in the stage III group (4.53 +/- 0.51) were lower than in the stage I group, although not significantly so. M/I values in the stage IV group (3.16 +/- 0.37) were significantly lower than in the stage I group (P = .025). In multiple regression analysis with a model in which age, sex, BMI, HbA1c, and creatinine clearance (Ccr) were included as independent variables, BMI and Ccr were demonstrated to be significant and independent contributors to insulin sensitivity indices as the dependent variable (beta = -0.716 and beta = 0.272, respectively, R2 = .564, P < .0001). In conclusion, the present cross-sectional study demonstrated in non-obese NIDDM patients with nephropathy that microalbuminuria did not affect peripheral insulin resistance, but uremia did, as in nondiabetic patients, and that the peripheral insulin resistance was significantly contributed to by the degree of obesity and uremia.

Cardiac disease in chronic uremia: pathogenesis

Cardiomyopathy in chronic uremia results from pressure and volume overload. The former causes concentric left ventricular [LV] hypertrophy, results from hypertension and aortic stenosis, and is also associated with diabetes mellitus and anemia. Volume overload causes LV dilatation, results from arteriovenous shunting, salt and water overload, and anemia, and is also associated with ischemic heart disease, hypertension, and hypoalbuminemia. Decreased major arterial compliance and an early return of arterial wave reflections are also associated with the extent of LV hypertrophy. Cardiomyopathy predisposes to diastolic and systolic dysfunction. The latter results from myocyte death, and predisposing factors include ischemic heart disease and the uremic environment. Ischemic heart disease may be atherosclerotic or nonatherosclerotic in origin. Multiple factors contribute to the vascular pathology of chronic uremia, including injury to the vessel wall, dyslipidemia, prothrombotic factors, increased oxidant stress, and hyperhomocysteinemia. Ischemic risk factors include hypertension, LV hypertrophy, hypoalbuminemia, and perhaps hyperparathyroidism. The clinical consequences of cardiomyopathy include heart failure, ischemic heart disease, dialysis hypotension, and arrhythmias. The adverse impact of ischemic heart disease is probably mediated through the development of cardiac failure.

Intrarenal hemodynamic abnormalities in diabetic nephropathy measured by duplex Doppler sonography

Intrarenal hemodynamics were studied by duplex Doppler sonography in 112 inpatients with type II diabetes mellitus (DM; 65 males, 47 females, 58 +/- 13 years old). The resistive index (RI) and pulsatility index (PI) of the interlobar arteries were calculated. The patients were divided into four groups: group I consisted of patients with urinary albumin excretion (UAE) < 20 micrograms/min (N = 42), group II with 20 < or = UAE < 200 (N = 28), group III with UAE > or = 200 (N = 25), and group IV with serum creatinine > or = 1.5 mg/dl (N = 17). Both RI and PI values in groups II, III, and IV were significantly higher than those in the controls (age- and sex-matched healthy persons, N = 37; P < 0.001), and those in group IV were significantly higher than those in groups I, II, and III (P < 0.0001). Multiple regression analysis revealed that RI values in DM patients were significantly affected by creatinine clearance, age, and duration of diabetes (R2 = 0.554, P < 0.0001). When intima-medial thickness (IMT) of the femoral and carotid arteries were measured by B-mode ultrasonography, RI values were significantly correlated with both the femoral and carotid arterial IMT. These results demonstrate that intrarenal hemodynamic abnormalities are present in type II DM patients with nephropathy, and that intrarenal hemodynamics are affected by decreased glomerular function and also probably by advanced arteriosclerosis.

Atherogenic lipoprotein changes in the absence of hyperlipidemia in patients with chronic renal failure treated by hemodialysis

We compared plasma lipid and lipoprotein parameters between 210 chronic renal failure patients treated by hemodialysis and 223 age- and sex-matched healthy control subjects to examine whether atherogenic lipoprotein changes were present in hemodialysis patients in the absence of hyperlipidemia. The hemodialysis group showed higher levels of plasma triglycerides, very low density lipoprotein (VLDL) cholesterol, and intermediate density lipoprotein (IDL) cholesterol and a lower level of high density lipoprotein (HDL) cholesterol. Low density lipoprotein (LDL) cholesterol of the hemodialysis group was not elevated but their LDL was significantly more triglyceride-enriched than that of controls. Subjects were then divided into five categories according to their plasma triglyceride levels at an interval of 50 mg/dl, and comparison was made between the two groups in the same range of plasma triglycerides. Hemodialysis patients again showed higher levels of VLDL- and IDL-cholesterol, and lower levels of HDL-cholesterol than the control group even in the plasma triglycerides-matched comparisons. Similarly, higher VLDL- and IDL-cholesterol levels in hemodialysis patients were significant in plasma total cholesterol-matched subgroup comparisons. Multiple regression analysis indicated that the relationship between plasma lipid concentrations and individual lipoprotein levels were substantially altered in uremic state. The 95th percentile level of IDL-cholesterol in the nonuremic controls was 15 mg/dl, and 45% of hemodialysis patients exceeded this level. Decreased HDL-cholesterol levels < or = 35 mg/dl were seen in 6% of the control and 38% of the hemodialysis group. Elevated IDL-cholesterol and decreased HDL-cholesterol were persistently found in hemodialysis patients with normal lipid levels. It is concluded that hemodialysis patients exhibited more atherogenic lipoprotein profile than nonuremic subjects with comparable levels of plasma triglycerides and total cholesterol. Especially, increased IDL- and decreased HDL-cholesterol levels in hemodialysis patients persisted even at very low levels of plasma lipids. Since elevated IDL and decreased HDL-cholesterol are implicated in the progression of atherosclerosis, these findings are of clinical importance in the diagnosis of lipoprotein disorder in chronic renal failure.

Echo color Doppler imaging of carotid vessels in hemodialysis patients: evidence of high levels of atherosclerotic lesions

Cardiovascular disease is the major cause of death in patients with end-stage renal disease, and the incidence of atherosclerosis-related complications is significantly higher in dialysis patients than in nonuremic controls. This study aimed at evaluating atherosclerotic involvement of carotid vessels in hemodialysis patients and in a group of subjects with a similar cardiovascular risk factor pattern using echo color Doppler ultrasonography. Carotid lesions have been evaluated, taking into account plaque characters (surface, echogenicity), the most severe luminal narrowing, and the number of vessels involved. A large number of vascular plaques has been observed in uremic patients: 73.8% versus 44% in the control group (chi square test = 10.98; P < 0.01). A high prevalence of carotid lesions has been found in both patients and controls with clinical evidence of cardiovascular complications. Finally, we have considered the presence of carotid lesions with a topographic evaluation. The presence of atheromatous lesions in hemodialysis patients compared with control subjects was statistically significant different in all the vessels except common carotid (internal carotid: chi-square test = 8.59, P < 0.01; external carotid; chi-square test = 13.46, P < 0.01; bulb chi-square test = 7.90; P < 0.01). Our data clearly show that the hemodialysis population suffers from a higher degree of atherosclerosis than age- and sex-matched controls with similar cardiovascular risk patterns, suggesting that the uremic state in conservative and substitutive treatment per se may contribute to "advanced" atherosclerosis. However, this does not enable us to state that hemodialysis accelerates atherosclerosis. In fact, the progression of atherosclerosis might be related to atherogenic factors operative before regular dialysis.

Angiotensin-converting enzyme gene polymorphism is associated with carotid arterial wall thickness in non-insulin-dependent diabetic patients

BACKGROUND

The insertion/deletion (I/D) polymorphism of the ACE gene has been shown to be associated with cardiovascular disease in healthy subjects as well as in patients with non-insulin-dependent diabetes mellitus (NIDDM). We investigated the relationship between the ACE gene polymorphism and the wall thickness of both carotid and femoral arteries in NIDDM patients.

METHODS AND RESULTS

We measured the intimal plus medial thickness (IMT) of both carotid and femoral arteries using high-resolution B-mode ultrasonography in 288 Japanese NIDDM patients (160 men, 128 women). No significant differences among the three genotypes were found with respect to age, sex, duration of diabetes, body mass index, blood pressure, plasma glucose, hemoglobin AIC, total cholesterol, triglycerides, HDL cholesterol, or cigarette-years. Plasma ACE levels were strongly associated with I/D polymorphism, with an additive effect of the D alleles. The carotid IMT of the patients carrying the D allele (DD+ID genotype) was significantly higher than that of the patients not carrying the D allele (II genotype) (P = .037), whereas the femoral IMT was not affected by the I/D polymorphism. Multiple regression analysis demonstrated that the risk factors for carotid IMT of patients with NIDDM were age, non-HDL cholesterol, and D allele of the ACE gene (R2 = .155, P < .0001).

CONCLUSIONS

The D allele of the ACE gene may be a risk factor for the development of wall thickening of the carotid but not the femoral artery in NIDDM patients.

Cardiac and arterial interactions in end-stage renal disease

Although cardiac hypertrophy is a frequent complication of end-stage renal disease (ESRD), relatively little is known about large arterial geometry and function in vivo in these patients, and the relationship between arterial changes and cardiac hypertrophy is unknown. Common carotid artery (CCA) intima-media thickness and internal diameter and left ventricular geometry and function were determined by ultrasound imaging in 70 uncomplicated ESRD patients and in 50 age-, sex-, and blood pressure-matched controls. Arterial distensibility and compliance were determined from simultaneously recorded CCA diameter and stroke changes in diameter and CCA pressure waveforms, obtained by applanation tonometry, and also by the measurement of carotid-femoral pulse wave velocity. Compared with control subjects, ESRD patients had greater left ventricular diameter (P < 0.01), wall thicknesses and mass (P < 0.001), increased CCA diameter (6.25 +/- 0.87 vs. 5.55 +/- 0.65 mm; P < 0.001), larger CCA intima-media thickness (777 +/- 115 vs. 678 +/- 105 microns; P < 0.001) and intima-media cross-sectional area (17.5 +/- 4.5 vs. 13.4 +/- 3.3 mm2; P < 0.001). In uremic patients, arterial hypertrophy was associated with decreased CCA distensibility (17.8 +/- 8.8 vs. 24.0 +/- 12.7 kPa-1.10(-3); P < 0.001) and compliance (5.15 +/- 2 vs. 6.0 +/- 2.5 m2.kPa-1.10(-7); P < 0.05), accelerated carotid-femoral pulse wave velocity (1055 +/- 290 vs. 957 +/- 180 cm/seconds; P < 0.001), early return and increased effect of arterial wave reflections (20.5 +/- 15.4 vs. 9.2 +/- 18.4%; P < 0.001). The latter phenomenons were responsible for increased pulsatile pressure load in CCA (58.3 +/- 21 vs. 48 +/- 17 mm Hg; P < 0.01) and were associated with a decreased subendocardial viability index (157 +/- 31 vs. 173 +/- 30%; P < 0.001). The CCA diameter was correlated with the left ventricular diameter (P < 0.01), and a significant correlations existed between CCA wall thickness or CCA intima-media cross-sectional area and left ventricular wall thicknesses and/or left ventricular mass (P < 0.01). In multivariate analysis, these relationships were independent regarding age, sex, blood pressure and body surface area. The present study documents parallel cardiac and vascular adaptation in ESRD, and demonstrates the potential contribution of structural and functional large artery alterations to the pathogenesis of left ventricular hypertrophy and functional alterations.