Endothelium-derived nitric oxide regulates arterial elasticity in human arteries in vivo

Exercise frequency and arterial compliance in non-diabetic and type 1 diabetic individuals

BACKGROUND

The role of exercise in preventing cardiovascular disease (CVD) has been well documented. To determine whether this benefit could be related to effects on vascular endothelial function and vessel wall elasticity, thereby preserving arterial compliance, we examined the relationship between habitual exercise and arterial compliance as measured by pulse wave analysis.

DESIGN

A cross-sectional study of healthy volunteers and patients with type 1 diabetes.

METHODS

Non-diabetic individuals not taking cholesterol or blood pressure-lowering medication (n=176) and patients with type 1 diabetes (n=105), aged 17-70 years, were recruited. Small and large artery compliance and other haemodynamic variables were measured using the PulseWave CR-2000 cardiovascular profiling system. A questionnaire was completed to assess the frequency of physical activity.

RESULTS

In multivariate analysis, undertaking three or more episodes of vigorous activity per week was associated with having a 1 unit greater small artery compliance, independent of age, sex, height, diabetes status and blood pressure. The effect was especially marked in non-diabetic women.

CONCLUSIONS

The results support other findings that regular physical activity protects against CVD, through the preservation of vascular compliance.

Effects of resuming endurance training on arterial stiffness and nitric oxide production during exercise in elite cyclists

Exercise training improves arterial compliance due to increases in blood flow to skeletal muscle during repeated bouts of daily exercise. The effect of resuming training on arterial stiffness in previously well-trained subjects is poorly documented. Hence, the purpose of this study was to determine the vascular effects induced by return to exercise in highly trained cyclists. Pulse wave velocity (PWV), an index of arterial stiffness, was assessed at rest and during constant moderate-intensity cycle exercises before and after 16 weeks of endurance training. The impact of daily exercise on the concentration of nitric oxide (NO) measured as nitrate in plasma was examined at rest and during maximal exercise before and after the training period. At rest, PWV was significantly lower in the subjects after a training session (6.4 +/- 0.4 vs. 8.1 +/- 0.4 m x s(-1), p < 0.05). During constant exercise, PWV was significantly and positively correlated with increases in blood pressure. The increased PWV induced by exercise was, however, significantly lower after training (9.8 +/- 0.6 vs. 11.4 +/- 0.6 m x s(-1), p < 0.05). After the training program, nitrate plasma levels at rest were higher. During the maximal test, the plasma nitrate concentration was increased in the subjects studied before the training period, but not after. These results show that resumption of chronic endurance training rapidly induces adaptive changes in arterial stiffness and NO release that may contribute to improved physical fitness in athletes.

Aortic correlates of clinical markers of large artery structure and function. Effects of aging and hypertension

BACKGROUND AND AIMS

Non-invasive measures of large artery structure and function--such as aorto-femoral pulse wave velocity (PWV), arterial compliance (AC) and common carotid intima-media thickness (CCA IMT)--can predict new CV events, independently of traditional CV risk factors. However, neither their relations with aorta properties nor the effects of aging and hypertension on those relations are yet clear.

METHODS AND RESULTS

40 subjects (18 M, 22 F; mean age 60+/-16 yrs, range 21-83 yrs) free of any acute CV event, valve disease or atrial fibrillation, were studied. Aortic IMT, diastolic diameter (D) and distensibility (Dist) were measured by transesophageal echocardiography at three different levels: ascending aorta (AA), distal aortic arch (Aarc) and descending aorta (DA). PWV was measured by Complior. AC was measured as the ratio of stroke volume to pulse pressure. CCA IMT was measured by ultrasonography in diastole. The Dist, IMT, and D of each aortic segment were introduced alternatively into the regression models. After controlling for age, sex, traditional risk factors and prevalent CV disease, AC showed a significant positive association with the distensibility of proximal aortic segments, but no significant association with properties of distal aorta; PWV showed a significant positive association with proximal aorta wall thickness and a negative association with distal aorta distensibility; CCA IMT was positively associated with distal aorta wall thickness, but not with any explored property of the proximal aorta. None of these relationships differed between younger or older, normotensive or hypertensive subjects.

CONCLUSIONS

Non-invasive measures of large artery structure and function are not equivalent with respect to their relations with aortic properties, so that AC seems to reflect proximal aorta function, PWV proximal aorta structure and distal aorta function, and CCA IMT distal aorta structure. Future studies are needed to confirm whether these relations identify a common pathogenetic mechanism, which may be the target for new therapeutic strategies.

Vascular endothelium-derived factors and arterial stiffness in strength- and endurance-trained men

Arterial stiffness is higher in strength-trained humans and lower in endurance-trained humans. However, the mechanisms underlying these different adaptations are unclear. Vascular endothelium-derived factors, such as endothelin-1 (ET-1) and nitric oxide (NO), play an important role in the regulation of vascular tonus. We hypothesized that endogenous ET-1 and NO participate in the adaptation of arterial stiffness in different types of exercise training. The purpose of this study was to investigate plasma ET-1 and NO concentrations and arterial stiffness in strength- and endurance-trained men. Young strength-trained athletes (SA; n = 11), endurance-trained athletes (EA; n = 12), and sedentary control men (C; n = 12) participated in this study. Maximal handgrip strength in SA and maximal oxygen uptake in EA were markedly greater than in C. Aortic pulse-wave velocity, which is an established index of arterial stiffness, was higher in SA and lower in EA than in C. Additionally, we measured systemic arterial compliance (SAC) using carotid artery applanation tonometry and Doppler echocardiography, because arterial stiffness is a primary determinant of the compliance. SAC was lower in SA and higher in EA compared with that in C. Plasma ET-1 concentrations were higher in SA compared with C and EA. We did not find significant differences in plasma NO concentrations (measured as the stable end product of NO, i.e., nitrite/nitrate). The relationships of plasma ET-1 concentrations to aortic pulse-wave velocity and SAC were linear. These results suggest that differences in endogenous ET-1 may partly participate in the mechanism underlying different adaptations of arterial stiffness in strength- and endurance-trained men.

Vascular compliance versus flow-mediated vasodilation: correlation with cardiovascular risk factors

Cardiovascular risk factors are associated with impaired endothelium dependent vasodilation and reduced vascular compliance. In this study, the correlation with cardiovascular risk factor score of two common techniques for assessing vascular function was compared. Risk factors and vascular function were evaluated in a study population of 122 people with peripheral arterial disease (PAD) or with risk factors for PAD (73 men and 49 women; mean age 69 years). A risk factor score was determined using Framingham criteria. Vascular compliance was assessed by pulse waveform analysis and simultaneous blood pressure measurement. Flow-mediated vasodilation of the brachial artery was measured using duplex ultrasonography. Participants with a high risk factor score had significantly reduced vascular compliance of large and small vessels. By contrast, the difference in flow-mediated vasodilation between those with a high or low risk factor score did not reach statistical significance. There was a significant negative correlation between vascular compliance and risk factor score. There was a similar trend between flow-mediated vasodilation and risk factor score, but this did not reach statistical significance. A measure of vascular compliance was more significantly correlated with cardiovascular risk factor score than was a measure of flow-mediated vasodilation in the study population. Neither technique provided values that were highly correlated with risk factor burden. Although flow-mediated vasodilation is a preferred research tool for assessing vascular function, technical limitations and biological variability may reduce its clinical application in assessing individual cardiovascular risk.

Effect of single-leg resistance exercise on regional arterial stiffness

To examine the effects of lower-limb unilateral resistance exercise on central and peripheral arterial stiffness, thirteen participants (7 male and 6 female, mean age = 21.5 +/- 0.7 years) performed leg press exercise using their dominant leg. Pulse wave velocity (PWV) was used to measure central (carotid to femoral) and peripheral (femoral to dorsalis pedis of both legs) arterial stiffness before, 5 min post, and 25 min post exercise. No change was found in central PWV. A leg-by-time interaction was found as peripheral PWV in the non-exercised leg did not change (7.9 +/- 0.3 m/s to 7.9 +/- 0.3 m/s to 8.0 +/- 0.3 m/s, P = 0.907) while peripheral PWV in the exercised leg significantly decreased from pre (8.7 +/- 0.4 m/s) to 5 min post exercise (7.5 +/- 0.3 m/s, P = 0.008) and 25 min post exercise (7.8 +/- 0.3 m/s, P = 0.031). Systolic blood pressure (BP) increased significantly from pre (126.9 +/- 3.4 mmHg) to 5 min post exercise (133.7 +/- 4.3 mmHg, P = 0.023) and was not different than resting values 25 min post exercise (123.2 +/- 3.1 mmHg). There was no change in diastolic BP. Compared to heart rate (HR) pre-exercise (55.4 +/- 1.4 bpm), HR was significantly increased 5 min post exercise (70.7 +/- 3.0 bpm, P = 0.001) and 25 min post exercise (69.1 +/- 2.0, P = 0.001). Acute resistance exercise appears to decrease arterial stiffness in the exercised leg while having no effect on central arterial stiffness or arterial stiffness of the non-exercised leg. These findings suggest that regional changes rather than systemic alterations may influence arterial stiffness following acute resistance exercise.

Nebivolol: a third-generation beta-adrenergic blocker

OBJECTIVE

To describe the pharmacologic and pharmacokinetic properties of a new beta-adrenergic blocker, nebivolol, and review the literature evaluating its efficacy in the treatment of hypertension and heart failure.

DATA SOURCES

Articles were identified through searches of MEDLINE (1996-May 2006) and International Pharmaceutical Abstracts (1970-May 2006), using the key word nebivolol. Additional references were selected from the bibliographies of the articles cited. Searches were not limited by language, time, or human subject.

STUDY SELECTION AND DATA EXTRACTION

Preclinical studies evaluating the pharmacologic and pharmacokinetic properties of nebivolol in humans were selected for review. Randomized, controlled, blinded clinical trials assessing the efficacy of nebivolol for the treatment of hypertension and heart failure were also included.

DATA SYNTHESIS

Preclinical data have established nebivolol as a third-generation beta-adrenergic blocker, as it possesses vasodilatory properties that contribute to its hemodynamic effects beyond those achieved at beta-adrenergic receptors. Short-term, randomized, controlled clinical trials have shown nebivolol to be as effective as other antihypertensive therapies at lowering blood pressure. One long-term trial showed a significant reduction in death and hospital admissions for cardiovascular causes when nebivolol was compared with placebo in patients with heart failure (31.1% vs 65.3%; HR 0.86; 95% CI 0.74 to 0.99).

CONCLUSIONS

Nebivolol is a novel beta-adrenergic blocker that possesses unique pharmacologic properties, compared with other agents in its class. Nebivolol appears to be as effective as other antihypertensive agents at lowering blood pressure and possesses benefits for patients with heart failure. Additional studies are needed to address the long-term benefits of nebivolol for hypertension, to compare nebivolol with other beta-adrenergic blockers for heart failure, and to investigate the clinical relevance of nitric oxide-mediated vasodilation.

Circulating endothelial progenitor cell deficiency contributes to impaired arterial elasticity in persons of advancing age

Reduced arterial elasticity is a hallmark of ageing in healthy humans and appears to occur independently of coexisting disease processes. Endothelial-cell injury and dysfunction may be responsible for this fall in arterial elasticity. We hypothesized that circulating endothelial progenitor cells (EPCs) are involved in endothelial repair and that lack of EPCs contributes to impaired arterial elasticity. A total of 56 healthy male volunteers were divided into young (n=26) and elderly (n=30) groups. Large and small artery elasticity indices were noninvasively assessed using pulse wave analysis. The number of circulating EPCs was measured by using flow cytometry. Cells demonstrating DiI-acLDL and FITC-ulex lectin double-positive fluorescence were identified as EPCs. C1 large artery elasticity and C2 small artery elasticity indices were significantly reduced in the elderly group compared with the young group (11.73+/-1.45 vs 16.88+/-1.69 ml/mm Hg x 10, P<0.001; 8.40+/-1.45 vs 10.58+/-1.18 ml/mm Hg x 100, P<0.001, respectively). In parallel, the number of circulating EPCs was significantly reduced in the elderly group compared with the young group (0.13+/-0.02 vs 0.17+/-0.04%, P<0.05). The number of circulating EPCs correlated with C1 large and C2 small artery elasticity indices (r=0.47, P<0.01; r=0.4, P<0.01). The present findings suggest that the fall in circulating EPCs with subsequently impaired endothelial-cell repair and function contributes to reduced arterial elasticity in humans with ageing. The decrease in circulating EPCs may serve as a surrogate biologic measure of vascular function and human age.

Effect of cigarette smoking on nitric oxide, structural, and mechanical properties of mouse arteries

Cigarette smoking (CS) is a major risk factor for vascular disease. The aim of this study was to quantitatively assess the influence of CS on mouse arteries. We studied the effect of short-term (6 wk) and long-term (16 wk) CS exposure on structural and mechanical properties of coronary arteries compared with that of control mice. We also examined the reversibility of the deleterious effects of CS on structural [e.g., wall thickness (WT)], mechanical (e.g., stiffness), and biochemical [e.g., nitric oxide (NO) by-products] properties with the cessation of CS. The left and right coronary arteries were cannulated in situ and mechanically distended. The stress, strain, elastic modulus, and WT of coronary arteries were determined. Western blot analysis was used to analyze endothelial NO synthase (eNOS) in the femoral and carotid arteries of the same mice, and NO by-products were determined by measuring the levels of nitrite. Our results show that the mean arterial pressure was increased by CS. Furthermore, CS significantly increased the elastic modulus, decreased stress and strain, and increased the WT and WT-to-radius ratio compared with those of control mice. The reduction of eNOS protein expression was found only after long-term CS exposure. Moreover, the NO metabolite was markedly decreased in CS mice after short- and long-term exposure of CS. These findings suggest that 16 wk of CS exposure can cause an irreversible deterioration of structural and elastic properties of mouse coronary arteries. The decrease in endothelium-derived NO in CS mice was seen to significantly correlate with the remodeling of arterial wall.

NADPH oxidases are in part responsible for increased cardiovascular superoxide production during aging

The aim of our study was to examine in rats, age-related differences in myocardial ischemic recovery and to determine the possible relationship with modification of cardiac and vascular oxidative stress. Isolated perfused hearts from young (2 months), adult (6 months), and old (21 months) Wistar rats were subjected to a ischemia-reperfusion sequence. Vascular histomorphological analyses were performed and NADPH oxidase was studied. The expression of angiotensin AT(1) receptors was evaluated using immunostaining. During the preischemic period, but also after ischemia, an aged-related decrease in myocardial functional parameters was observed, and was associated with an increased release of reactive oxygen species. In aortas, the activity and expression of NADPH oxidase increased with age according to the ESR, fluorescence microscopy, and immunohistochemistry; the NADPH oxidase involved was localized in endothelial cells. We found an age-related increase in the expression of endothelial angiotensin AT(1). Our study suggests that myocardial function and adaptation to ischemia-reperfusion declined during aging and are related to a higher level of oxidative stress. Endothelial NADPH oxidase is a major contributor to age-related cardiovascular deterioration. One of the regulators of vascular NADPH oxidase activity, the renin-angiotensin system, may be involved in the modulation of vascular superoxide production during the aging process.

A comparison of three different methods to determine arterial compliance in the elderly: the Prospective Investigation of the Vasculature in Uppsala Seniors (PIVUS) study

BACKGROUND

Several different techniques to evaluate arterial compliance have been described but have not been simultaneously tested in a large-scale, population-based setting. This study aimed to evaluate the feasibility and relation to cardiac risk of three of these techniques in the Prospective Study of the Vasculature in Uppsala Seniors (PIVUS) study.

METHODS AND RESULTS

In the population-based PIVUS study (1016 participants aged 70), assessment of arterial distensibility by ultrasound in the carotid artery, by pulse wave analysis (augmentation index) and the stroke volume to pulse pressure ratio by echocardiography were successfully employed in 86, 92, 91 and 77% of the sample, respectively. All three indices of arterial compliance were inter-related (r = 0.19-0.34, P < 0.0001 for all). Although all three indices were significantly related to the Framingham risk score (r = 0.12-0.32, P = 0.0005-0.0001), only carotid artery distensibility and the stroke volume to pulse pressure ratio were independently associated with the Framingham score in multiple regression analysis (P < 0.0001 for both).

CONCLUSIONS

All three indices to evaluate arterial compliance were feasible to obtain in a general elderly population and were inter-related. Although all of the techniques were correlated to Framingham risk score, only carotid artery distensibility and the stroke volume to pulse pressure ratio were independently related to coronary risk, suggesting complementary use of these two indices of arterial compliance in the future.

Different Effects of Atherogenic Lipoproteins and Blood Pressure on Arterial Structure and Function: The Bogalusa Heart Study

Differential impact of non-high-density lipoprotein cholesterol (total cholesterol minus high-density lipoprotein cholesterol) and blood pressure on arterial wall thickness and stiffness was examined in 900 black and white adults aged 24-43 years. Blacks compared with whites had greater values of pulse wave velocity (5.4 m/sec vs. 5.2 m/sec; p<0.01) and carotid artery intima-media thickness (0.83 mm vs. 0.80 mm; p<0.01). Non-high-density lipoprotein cholesterol was significantly associated with carotid intima-media thickness (standardized regression coefficient [b]=0.21; p<0.01), but not with pulse wave velocity (b=0.03; p=0.37), after adjusting for race, sex, age, body mass index, insulin, glucose, and smoking. Systolic blood pressure was associated significantly stronger with pulse wave velocity (b=0.36; p<0.01) than with carotid intima-media thickness (b=0.15; p<0.01). No race difference in these relationships was found. The results of this study indicate that atherogenic lipoproteins and blood pressure may play different roles in the development of arterial wall stiffness and atherosclerosis.

Endothelial dysfunction: a multifaceted disorder (The Wiggers Award Lecture)

Endothelial cells synthesize and release various factors that regulate angiogenesis, inflammatory responses, hemostasis, as well as vascular tone and permeability. Endothelial dysfunction has been associated with a number of pathophysiological processes. Oxidative stress appears to be a common denominator underlying endothelial dysfunction in cardiovascular diseases. However, depending on the pathology, the vascular bed studied, the stimulant, and additional factors such as age, sex, salt intake, cholesterolemia, glycemia, and hyperhomocysteinemia, the mechanisms underlying the endothelial dysfunction can be markedly different. A reduced bioavailability of nitric oxide (NO), an alteration in the production of prostanoids, including prostacyclin, thromboxane A2, and/or isoprostanes, an impairment of endothelium-dependent hyperpolarization, as well as an increased release of endothelin-1, can individually or in association contribute to endothelial dysfunction. Therapeutic interventions do not necessarily restore a proper endothelial function and, when they do, may improve only part of these variables.

Role of nitric oxide in the regulation of digital pulse volume amplitude in humans

Measurement of the increase in digital pulse volume amplitude (PVA) during reactive hyperemia relative to baseline (PVA-RH) is being applied widely as a convenient test of nitric oxide bioavailability. However, evidence linking digital PVA-RH to nitric oxide is currently lacking. Accordingly, we investigated whether nitric oxide is responsible for the increase in digital PVA. During reactive hyperemia, we used a peripheral arterial tonometer to record digital PVA at baseline and during reactive hyperemia. The role of nitric oxide in these responses was investigated in 19 healthy subjects by inhibiting nitric oxide synthesis with N(G)-nitro-L-arginine methyl ester (L-NAME). Ten subjects underwent the identical protocol with saline and five with phenylephrine, a nonspecific vasoconstrictor, instead of L-NAME. The change in digital PVA after drug administration was compared between the three groups. Relative to the response with saline (-5 +/- 2%), baseline PVA was unchanged by L-NAME infusion (-10 +/- 2%), but it decreased significantly with phenylephrine (-50 +/- 12%; P = 0.003). PVA-RH increased slightly with saline infusion (9 +/- 4%). In comparison, PVA-RH was significantly blunted by L-NAME administration (-46 +/- 21%; P = 0.002) and was relatively unchanged by phenylephrine (20 +/- 9%). The present study establishes a central role for nitric oxide in the augmentation of PVA during reactive hyperemia. The measurement of digital PVA-RH may indeed provide a simple means of assessing endothelial function in humans.

Effects of stimulation of nitric oxide synthesis on large artery stiffness in patients with peripheral arterial disease

The role of endothelium-derived nitric oxide (NO) in modulation of large artery stiffness in patients with peripheral arterial disease (PAD) is unexplored. The aim of this study was to evaluate, using pulse wave analysis (PWA), changes in aortic and systemic arterial stiffness following administration of nitroglycerin and beta(2)-agonist salbutamol in PAD patients (n = 24) and in healthy controls (n = 24). Changes in estimated aortic pulse wave velocity (T(r)) and in augmentation index (AIx), following administration of nitroglycerin and salbutamol, were assessed using PWA. Salbutamol-induced changes in T(r) and in AIx were significantly reduced in PAD patients (P < 0.001 and < 0.001, respectively), while nitroglycerin-produced changes were not different (P = 0.25 and 0.35, respectively). Changes in T(r) after salbutamol administration were independent of changes in mean arterial pressure (MAP) (R = -0.21, P = 0.16). This study shows that stimulation of NO synthesis fails to modify stiffness of the large arteries in PAD patients and changes in aortic stiffness are independent of changes in MAP. Our data support the utility of PWA as a non-invasive method for assessment of NO-mediated vascular changes.

The endothelin system and its antagonism in chronic kidney disease

The incidence of chronic kidney disease (CKD) is increasing worldwide. Cardiovascular disease (CVD) is strongly associated with CKD and constitutes one of its major causes of morbidity and mortality. Treatments that slow the progression of CKD and improve the cardiovascular risk profile of patients with CKD are needed. The endothelins (ET) are a family of related peptides, of which ET-1 is the most powerful endogenous vasoconstrictor and the predominant isoform in the cardiovascular and renal systems. The ET system has been widely implicated in both CVD and CKD. ET-1 contributes to the pathogenesis and maintenance of hypertension and arterial stiffness and more novel cardiovascular risk factors such as oxidative stress and inflammation. Through these, ET also contributes to endothelial dysfunction and atherosclerosis. By reversal of these effects, ET antagonists may reduce cardiovascular risk. In particular relation to the kidney, antagonism of the ET system may be of benefit in improving renal hemodynamics and reducing proteinuria. ET likely also is involved in progression of renal disease, and data are emerging to suggest a synergistic role for ET receptor antagonists with angiotensin-converting enzyme inhibitors in slowing CKD progression.

Arterial stiffness in preeclamptic and chronic hypertensive pregnancies

OBJECTIVE

To assess arterial stiffness in pregnancies complicated by hypertensive disorders: preeclampsia and chronic hypertension.

STUDY DESIGN

Twenty preeclamptic and 18 chronic hypertensive parturients were studied. The reference data were obtained from 29 healthy pregnant women and 29 non-pregnant women. Systolic blood pressure (SAP), diastolic blood pressure (DAP), mean arterial pressure (MAP) and pulse pressure (PP) were measured. Stroke index (SI), heart rate (HR), cardiac index (CI), systemic vascular resistance index (SVRI) and pulse wave velocity (PWV) were derived by whole-body impedance cardiography. Arterial compliance was defined as the SI to PP ratio (SI/PP).

RESULTS

Significantly higher PP and PWV and lower SI/PP were observed in preeclamptic compared to uncomplicated pregnancies. Preeclamptic pregnancies also differed from chronic hypertensive pregnancies by higher PP and lower SI/PP. Women with chronic hypertension had significantly higher PWV than the control group, but PP and SI/PP were not different. In both hypertensive groups SVRI was exceptionally high.

CONCLUSIONS

Besides the vasoconstriction of smaller peripheral arteries, our finding of increased arterial stiffness in preeclamptic pregnancies suggests that also larger arteries with altered viscoelastic properties are involved in the aberrant hemodynamics of preeclampsia. Compared to preeclamptic subjects, women with chronic hypertension shared a common feature of high systemic vascular resistance, but changes in arterial stiffness were less than in preeclampsia.

Influence of the metabolic syndrome on aortic stiffness in never treated hypertensive patients

BACKGROUND AND AIM

Metabolic syndrome (MS) carries an increased risk for cardiovascular events and there is a growing awareness that large artery stiffening is a powerful predictor of cardiovascular morbidity and mortality. Little is known about the relationship of MS with aortic stiffness. The aim of our study was to analyze, in patients with essential hypertension, the influence of MS, defined according to the criteria proposed by the Third Report of the National Cholesterol Education Program Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (NCEP-ATP III), on carotid-femoral pulse wave velocity (PWV), a measure of aortic stiffness.

METHODS

Ninety-three untreated essential hypertensives, aged between 23 and 61 years, without diabetes mellitus, were studied. All subjects underwent routine blood chemistry, oral glucose tolerance test with glucose and insulin determinations, albumin excretion rate (AER) measurement, 24-h ambulatory blood pressure monitoring, and measurement of carotid-femoral PWV, by means of a computerized method.

RESULTS

Patients with MS (n = 28) showed higher age-adjusted carotid-femoral PWV (10.1 +/- 1.4 vs 9.3 +/- 1.4 m/s; p = 0.01) when compared to subjects without MS. This difference held after controlling for gender and for 24-h mean blood pressure (MBP) (p = 0.02) and lost its statistical significance after further adjustment for AER. In a multiple regression model, excluding the individual components of MS, in which metabolic syndrome was added along with age, gender, smoking habit, LDL cholesterol, HOMA index, 24-h MBP and 24-h heart rate, MS remained independently associated with carotid-femoral PWV (beta = 0.29; p = 0.002). The statistical significance of this association disappeared after the inclusion into this model of AER.

CONCLUSIONS

Metabolic syndrome is associated with an increased aortic stiffness. Main explanatory factors of this association are age, systolic blood pressure and albumin excretion rate.

Increased circulating concentrations of asymmetric dimethylarginine (ADMA) in white coat hypertension

Elevated plasma levels of the endogenous nitric oxide (NO) synthase inhibitor asymmetric dimethylarginine (ADMA) contribute to endothelial dysfunction and seem to be a predictor for cardiovascular mortality. Elevated ADMA plasma concentrations have been demonstrated in patients with hypertension. However, the plasma concentrations of ADMA in white coat hypertension (WCH) has not been previously studied. The aim of this study was to evaluate ADMA in WCH and compare with normotensive (NT) and hypertensive (HT) patients. We also evaluated the relation between ADMA and NO in these three groups. For this purpose, 34 NT, 34 white coat hypertensive (clinical hypertension and ambulatory daytime blood pressure <135/85 mmHg) and 34 HT patients were recruited in this study. The subjects were matched for age, gender, body mass index (BMI) and the patients with smoking habit, dyslipidaemia and diabetes mellitus were excluded. The ADMA levels were determined by high performance liquid chromatography. Plasma ADMA levels were significantly higher in WCH group than in the NT group (3.21+/-0.49 micromol/l vs 2.84+/-0.58 micromol/l, P=0.046). It was significantly higher in the HT group than in the NTs (4.24+/-0.38 micromol/l, P<0.001). There was also a significant difference between the HT and WCH groups (P<0.001). The WCH subjects had significantly higher levels of NO than the HTs (41.68+/-2.23 vs 32.18+/-2.68 micromol/l; P<0.001) and significantly lower values than the NTs (48.24+/-4.29 micromol/l; P<0.001). In WCH and HT group, there was a negative correlation between ADMA and NO (r=-0.515, P=0.003 and r=-0.389, P=0.034, respectively). In NT subjects, there was no correlation between these two parameters (r=-0.287, P=0.124). The correlation between ADMA and NO was stronger in WCH group than in HT group. Although NO levels in HT patients were lower than WCHs and ADMA levels were higher in HT patients than WCHs, the negative correlation of these two parameters were more pronounced in WCH group. Decreased NO and increased ADMA levels in WCH may indicate endothelial dysfunction. Our data indicate also that WCH represent an intermediate group between NT and HT when endothelial dysfunction is concerned.

A short-term admission improved brachial-ankle pulse wave velocity in type 2 diabetic patients

Brachial-ankle pulse wave velocity (baPWV) is a non-invasive method for assessing arterial stiffness associated with atherosclerosis. We examined whether baPWV could improve during a 2-week hospital-based education program in patients with type 2 diabetes and whether improvement associates with changes in known atherogenic risk factors. Body mass index (BMI), blood pressure (BP), fasting plasma glucose (FPG), insulin, lipid profiles and baPWV were measured in 32 type 2 diabetic patients before and after an educational program that included advice about nutrition and exercise. Relationship between the changes in baPWV and additional parameters, 24h-urinary excretion of C-peptide, visceral and subcutaneous fat area by abdominal computer tomography and intima-medial thickness (IMT) of the carotid artery by ultrasonography, were also evaluated. Baseline values of baPWV significantly correlated with age, duration of diabetes, BP, IMT and FPG. BaPWV significantly decreased after the program (-120+/-108.4 cm/s, P<0.0001) and this change significantly correlated with that of systolic BP (r=0.697, P<0.0001) and FPG (r=0.452, P<0.05). These results indicate that short-term hospitalization with an educational program can improve arterial wall stiffness, perhaps due to improvements in BP and glycemic control.

Flow-mediated changes in pulse wave velocity: a new clinical measure of endothelial function

AIMS

To test whether measuring hyperaemic changes in pulse wave velocity (PWV) could be used as a new method of assessing endothelial function for use in clinical practice.

METHODS AND RESULTS

Flow-mediated changes in vascular tone may be used to assess endothelial function and may be induced by distal hyperaemia, while endothelium-mediated changes in vascular tone can influence PWV. These three known principles were combined to provide and test a novel method of measuring endothelial function by the acute effects of distal hyperaemia on upper and lower limb PWV (measured by a recently developed method). Flow-mediated changes in upper and lower limb PWV were compared in 17 healthy subjects and seven patients with stable chronic heart failure (CHF), as a condition where endothelial function is impaired but endothelium-independent dilator responses are retained. Corroborative measurements of PWV and brachial artery diameter responses to endothelium-dependent and -independent pharmacological stimuli were performed in a further eight healthy subjects. Flow-mediated reduction of PWV (by 14% with no change in blood pressure) was found in normal subjects but was almost abolished in patients with CHF. PWV responses appear to be inversely related to and relatively greater than brachial artery diameter responses.

CONCLUSION

The method may offer potential advantages of practical use and sensitivity over conduit artery diameter responses to measure endothelial dysfunction.

Measurement of flow-mediated dilatation of the brachial artery is affected by local elastic vessel wall properties in high-risk patients

OBJECTIVES

To assess whether the validity of endothelial function measurement by flow-mediated dilatation (FMD) is affected by local brachial artery stiffness (distensibility coefficient; DC) and arterial wall thickness (intima-media thickness, IMT).

BACKGROUND

FMD measurement relies on assessment of arterial diameter change. Increased IMT and decreased DC might physically limit dilatation of the brachial artery in spite of healthy endothelium.

METHODS

DC, IMT and FMD of the brachial artery were simultaneously measured in 349 patients with advanced atherosclerosis or cardiovascular risk factors. The relations between FMD and age, and FMD and current smoking were regarded as a proxy for the relation between FMD and true endothelial function.

RESULTS

The relations between FMD and age, and FMD and smoking, were significantly modified by brachial artery DC. No modification was found for IMT. The interaction terms were statistically significant (p=0.03 and 0.04, respectively). The relation between FMD and age, and FMD and smoking was progressively more pronounced in patients with more elastic arteries.

CONCLUSION

The results of our study indicate that increased arterial stiffness may interfere with valid measurement of FMD and that patients with stiff arteries may be considered for exclusion from analyses involving FMD to ensure its validity.

Nocturnal hemodialysis increases arterial baroreflex sensitivity and compliance and normalizes blood pressure of hypertensive patients with end-stage renal disease

BACKGROUND

Impaired neural control of heart rate, elevated arterial stiffness, and hypertension place patients with end-stage renal disease (ESRD) at increased risk of cardiovascular mortality. Nocturnal hemodialysis (6 x 8 hours/week), a more intense program than conventional hemodialysis (3 x 4 hours/week), lowers blood pressure and restores brachial dilator responses to hyperemia and nitrates.

METHODS

We hypothesized that nocturnal hemodialysis would increase arterial baroreflex sensitivity for heart rate of hypertensive ESRD patients by an afferent vascular mechanism. Ten consecutive hypertensive ESRD patients (age 42 +/- 4) (mean +/- SEM) receiving conventional hemodialysis were studied before and 2 months after conversion to nocturnal hemodialysis. Regression slopes relating RR interval responses to rises or falls in systolic blood pressure were averaged to derive spontaneous baroreflex sensitivity for heart rate for each patient, and the stroke volume/pulse pressure ratio was used to estimate total arterial compliance.

RESULTS

Dialysis dose (Kt/V per session) increased from 1.2 +/- 0.05 to 2.1 +/- 0.1 (P < 0.05). Despite withdrawal of antihypertensive medications (from 2.9 to 0.1 drugs/patient), nocturnal hemodialysis lowered systolic blood pressure (from 143 +/- 4 to 120 +/- 6 mm Hg) (P= 0.001). Both baroreflex sensitivity (from 4.76 +/- 1.1 msec/mm Hg to 6.91 +/- 1.1 msec/mm Hg) (P= 0.04) and total arterial compliance (from 0.98 +/- 0.13 mL/mm Hg to 1.43 +/- 0.2 mL/mm Hg) (P= 0.02) were higher following conversion to nocturnal hemodialysis. Increases in baroreflex sensitivity correlated with increases in stroke volume/pulse pressure (r= 0.845, P= 0.002).

CONCLUSION

These findings are consistent with the concept that nocturnal hemodialysis increases baroreflex sensitivity via greater afferent baroreceptor responsiveness to pulsatile pressure. A more favorable risk profile, due to enhanced baroreflex regulation of the circulation and vascular compliance, may translate into lower cardiovascular event rates in ESRD patients receiving nocturnal hemodialysis.

Repeated pregnancies (multiparity) increases venous tone and reduces compliance

In humans, multiparity (repeated pregnancy) is associated with increased risk of cardiovascular disease. In rats, multiparity increases the pressor response to phenylephrine and to acute stress, due in part to changes in tone of the splanchnic arterial vasculature. Given that the venous system also changes during pregnancy, we studied the effects of multiparity on venous tone and compliance. Cardiovascular responses to volume loading (2 ml/100 g body wt), and mean circulatory filling pressure (MCFP, an index of venomotor tone) were measured in conscious, repeatedly bred (RB), and age-matched virgin rats. In addition, passive compliance and venous reactivity of isolated mesenteric veins were measured by pressure myography. There was a greater increase in mean arterial pressure after volume loading in RB rats (+7.2 ± 2.5 mmHg, n = 8) than virgin rats (−1.4 ± 1.7 mmHg, n = 7) ( P < 0.05). The increase in MCFP in response to norepinephrine (NE) was also greater in RB rats [half maximal effective dose (ED50) 3.1 ± 0.5 nmol·kg−1·min−1, n = 6] than virgins (ED50: 12.1 ± 2.7 nmol·kg−1·min−1, n = 6) ( P < 0.05). Pressure-induced changes in passive diameter were lower in isolated mesenteric veins from RB rats (29.3 ± 1.8 μm/mmHg, n = 6) than from virgins (36.9 ± 1.3 μm/mmHg, n = 6) ( P < 0.05). Venous reactivity to NE in isolated veins was also greater in RB rats (EC50: 2.68 ± 0.37×10−8 M, n = 5) than virgins (EC50: 4.67 ± 0.93 × 10−8 M, n = 8). We conclude that repeated pregnancy induces a long-term reduction in splanchnic venous compliance and augments splanchnic venous reactivity and sympathetic tonic control of total body venous tone. This compromises the ability of the capacitance (venous) system to accommodate volume overloads and to buffer changes in cardiac preload.

An updated clinical primer on large artery mechanics: implications of pulse waveform analysis and arterial tonometry

PURPOSE OF REVIEW

The use of pulse wave analysis with arterial tonometry has accelerated over the last year. Despite approval from the US Food and Drug Administration in 2001 on the use of generalized transfer function to generate the central (aortic) pressure wave from the radial waveform, this technique is still questioned. This review summarizes major findings on (a) value of arterial tonometry in determining indices of cardiovascular function, (b) use of these indices in outcome and drug studies, (c) relevance to major trials on blood pressure reduction.

RECENT FINDINGS

Pulse pressure has emerged as a better predictor of cardiac ischemic events than systolic, diastolic, and mean brachial pressure. Central systolic and pulse pressure and augmentation index have shown an even better relation with cardiovascular events and with outcomes. The claim by specific angiotensin-converting enzyme inhibitor and angiotensin receptor blocker drugs of their benefits "beyond blood pressure lowering" has been challenged on the basis of greater reduction in central and aortic pressure compared with brachial pressure measured by cuff sphygmomanometer, as shown by the pREterax in regression of Arterial Stiffness in a contrOlled double-bliNd study. Augmentation index is higher in hypertension, is inversely related to body height, and can be reduced by exercise. Augmentation index shows a linear relation with age up to 60 years. Regrettably, recent major trials such as the Comparison of Amlodipine versus Enalapril to Limit Occurrences of Thrombosis, Prevention of Events with Angiotensin Converting Enzyme Inhibition, and Valsartan Antihypertensive Long-term Use Evaluation studies have not included pulse wave analysis to distinguish the relative benefit of different drugs.

SUMMARY

Pulse wave analysis will assist in a better understanding of hypertension as well as in establishing the extent of cardiovascular disease and for monitoring therapy.

Oral vitamin C ameliorates smoking-induced arterial wall stiffness in healthy volunteers

We have investigated whether the oral administration of vitamin C could prevent smoking-induced acceleration of arterial stiffness in healthy volunteers. Subjects were pretreated with 2 g vitamin C and their heart rate (HR), mean blood pressure (MBP), and brachial-ankle pulse wave velocity (baPWV) were measured before and after smoking. Smoking significantly increased the HR, MBP, baPWV (13, 6.4, 7.0%). Vitamin C treatment significantly reduced the smoking-induced elevation in baPWV at 0 min (- 58.5%, p = 0.0002) without affecting HR or MBP. These findings suggest that oral vitamin C treatment prevents smoking-induced acceleration in arterial stiffness through reducing endothelial dysfunction.

Simvastatin improved arterial compliance in high-risk patients

Reduced arterial compliance is associated with arteriosclerosis. In some arteries, this is due in part to abnormal vascular tone, which can be altered by low-density lipoprotein (LDL) cholesterol reduction and statin therapy. We tested the effectiveness of statin therapy in improving arterial compliance in patients with manifest coronary disease (CAD) and/or diabetes. Simvastatin (40 mg/day) was administered to 10 patients with proven CAD for 4 months. As measured by air plethysmography, compliance of the arterial segments in the thigh improved in every patient after 2 months, increasing by 34% by the fourth month. Compliance at the calf was not affected. These results suggest that compliance in the thigh is controlled by smooth muscle tone. Compliance measurements in the thigh and calf may be a useful measurement in evaluating high-risk patients and monitoring cholesterol-lowering therapy.

Effects of maternal hypoxia or nutrient restriction during pregnancy on endothelial function in adult male rat offspring

Compromised fetal growth impairs vascular function; however, it is unclear whether chronic hypoxia in utero affects adult endothelial function. We hypothesized that maternal hypoxia (H, 12% O2, n= 9) or nutrient restriction (NR, 40% of control, n= 7) imposed from day 15-21 pregnancy in rats would impair endothelial function in adult male offspring (relative to control, C, n= 10). Using a wire myograph, endothelium-dependent relaxation in response to methacholine was assessed in small mesenteric arteries from 4- and 7-month-old (mo) male offspring. Nitric oxide (NO) mediation of endothelium-dependent relaxation was evaluated using N(omega)-nitro-L-arginine methyl ester (L-NAME; NO synthase inhibitor). Observed differences in the NO pathway at 7 months were investigated using exogenous superoxide dismutase (SOD) to reduce NO scavenging, and sodium nitroprusside (SNP; NO donor) to assess smooth muscle sensitivity to NO. Sensitivity to methacholine-induced endothelium-dependent relaxation was reduced in H offspring at 4 months (P < 0.05), but was not different among groups at 7 months. L-NAME reduced methacholine sensitivity in C (P < 0.01), H (P < 0.01) and NR (P < 0.05) offspring at 4 months, but at 7 months L-NAME reduced sensitivity in C (P < 0.05), tended to in NR (P= 0.055) but had no effect in H offspring. SOD did not alter sensitivity to methacholine in C, but increased sensitivity in H offspring (P < 0.01). SNP responses did not differ among groups. In summary, prenatal hypoxia, but not nutrient restriction impaired endothelium-dependent relaxation at 4 months, and reduced NO mediation of endothelial function at 7 months, in part through reduced NO bio-availability. Distinct effects following reduced maternal oxygen versus nutrition suggest that decreased oxygen supply during fetal life may specifically impact adult vascular function.

Benefit of glyceryl trinitrate on arterial stiffness is directly due to effects on peripheral arteries

OBJECTIVE

To determine how the vasodilator glyceryl trinitrate (GTN) alters arterial stiffness and improves left ventricular afterload.

METHODS

Ascending aortic pressure waves were measured with fluid filled catheters of high fidelity in 50 patients undergoing cardiac surgery, before cardiopulmonary bypass, both before and after intravenous infusion of GTN. In all 50 patients, wave reflection was identifiable as a secondary boost to late systolic pressure, permitting the pressure wave to be separated into a primary component, attributable to left ventricular ejection and properties of the proximal aorta, and a secondary component, attributable to reflection of the primary wave from the peripheral vasculature.

RESULTS

GTN infusion caused no change in amplitude of the primary wave (mean (SD) 0.0 (1.4) mm Hg, not significant) but substantial reduction (14.6 (9.6) mm Hg, p < 0.0001) in amplitude of the secondary reflected wave. Fall in mean pressure was attributable to a mix of arteriolar and venous dilatation, with relative contributions unable to be separated.

CONCLUSION

Favourable effects of GTN on arterial stiffness can be attributed to effects on peripheral muscular arteries, causing reduction in wave reflection. Results conform with previous invasive studies on vasodilator agents and their known effects on calibre and compliance of muscular arteries.

Nebivolol: a review

Nebivolol is a vasodilating beta-blocker, which can be distinguished from other beta-blockers by its haemodynamic profile. It combines beta-adrenergic blocking activity with a vasodilating effect mediated by the endothelial L-arginine nitric oxide (NO) pathway. The blood pressure lowering effect of nebivolol is linked to a reduction in peripheral resistance and an increase in stroke volume and preservation of cardiac output. The effects of nebivolol have been compared with other beta-blockers and also with other classes of antihypertensive agents. In general, response rates to treatment are higher and the frequency and severity of adverse events are either comparable or lower with nebivolol. Endothelium-derived NO is important in the regulation of large arterial stiffness, which in turn is a major risk factor for cardiovascular disease. Therefore, antihypertensive drugs, such as nebivolol, that also improve endothelial function and decrease arterial stiffness, may contribute to a reduction in cardiovascular risk.

Endothelium and angiogenesis in white coat hypertension

Hypertensive patients are at particular risk of cardiovascular complications, possibly related to endothelial damage or dysfunction, or to abnormal angiogenesis. The aim of this study was to compare the risk conferred by white coat hypertension (WCH) vs sustained hypertension in the development of the endothelial dysfunction and abnormal angiogenesis by evaluating nitric oxide (NO=NO2+NO3), endothelin-1 (ET-1), vascular endothelial growth factor (VEGF), and E-selectin levels in plasma. The study group included 102 subjects, 34 with WCH (17 male and 17 female patients) aged 49+/-11 years, 34 sustained hypertensives (HT) (15 male and 19 female patients) aged 47+/-11 years and 34 normotensive control subjects (NT) (16 male and 18 female patients) aged 48+/-10 years. WCH was defined as clinical hypertension and daytime ambulatory blood pressure less than 135/85 mmHg. The subjects were matched for age, gender, body mass index and the patients with smoking habit, dyslipidaemia, and diabetes mellitus were excluded from the study. The NO, ET-1, VEGF and E-selectin levels were analysed by ELISA technique. The WCH subjects had significantly higher levels of NO than the HT (41.68+/-2.23 vs 32.18+/-2.68 micromol/l; P<0.001) and significantly lower values than the NT (48.24+/-4.29 micromol/l; P<0.001). ET-1 levels of the WCH group were significantly higher than the NT (8.10+/-0.92 vs 5.95+/-0.26 ng/ml; P<0.001) and significantly lower than the HT (11.46+/-0.59 ng/ml; P<0.001). Considering with VEGF, the WCH group had significantly higher levels than the NT (195.88+/-11.84 vs 146.26+/-18.67 pg/ml; P<0.001), but the difference from the HT group was not significant (203.35+/-7.48 pg/ml; P=0.062). E-selectin in the WCH group was significantly lower than the HT (4.77+/-0.52 vs 8.49+/-2.85; P<0.001), but the difference from the NT group was not significant (3.86+/-0.67; P=0.077). Our data demonstrate that WCH is associated with endothelial dysfunction and abnormal angiogenesis. The degree of these changes is not as severe as observed in hypertensive population.

Aerobic exercise performance correlates with post-ischemic flow-mediated dilation of the brachial artery in young healthy men

In older healthy men, aerobic exercise capacity is related to postischemic flow-mediated dilation of the brachial artery (FMD), but corresponding data in a younger population is not available. In addition, whether submaximal aerobic exercise performance also correlates with this kind of vasomotor reactivity is not known. Therefore, in 15 nonsmoking young healthy men [age 27 (5) years; body mass index: 24 (2) kg/m(2); mean (SD)] with different levels of ordinary physical activity, but not performing upper-extremity training, we measured FMD at 1 min after reactive hyperemia, and pulmonary oxygen uptake (VO(2)) at ventilatory anaerobic threshold (VO(2)AT) and at peak effort (peak VO(2)) during an incremental exercise on a treadmill. In our participants, FMD was 9.1 (3.4)%, VO(2)AT was 40.72 (5.92) ml/kg per min, and peak VO(2) was 52.95 (8.13) ml/kg per min. Using bivariate Pearson's correlation, and in separate multivariate regression analyses, VO(2)AT and peak VO(2) showed a significant and reasonably good correlation with FMD (r = 0.84, P < 0.001 and r = 0.77, P = 0.001, respectively), independent of age, body mass index and serum total cholesterol (beta = 0.77, P < 0.001, R(2) of the overall model = 0.79 and beta = 0.70, P < 0.005, R(2) of the overall model = 0.69, respectively). Our data provide evidence suggesting that in young healthy men a higher submaximal and maximal aerobic exercise performance is associated with a greater FMD of peripheral conduit arteries.

Marinobufagenin may mediate the impact of salty diets on left ventricular hypertrophy by disrupting the protective function of coronary microvascular endothelium

Individuals who eat salty diets and who are "salt-sensitive" tend to have increased left ventricular mass, independent of blood pressure; this phenomenon awaits an explanation. It is clear that local up-regulation of angiotensin II (AngII) production and activity play a key role in the induction of left ventricular hypertrophy (LVH). Recent evidence suggests that a healthy coronary microvascular endothelium opposes this effect by serving as a paracrine source of nitric oxide (NO), a natural antagonist of AngII activity, and that up-regulation of this mechanism can account for the protective role of bradykinin with respect to LVH. The coronary microvasculature also possesses NAD(P)H oxidase activity that can generate superoxide, inimical to the bioactivity of endothelial NO. There is now good reason to believe that the triterpenoid marinobufagenin (MBG), a selective inhibitor of the alpha-1 isoform of the sodium pump, mediates the impact of salty diets on blood pressure; production of MBG by the adrenal cortex is boosted when salt-sensitive animals are fed salty diets. It is hypothesized that coronary microvascular endothelium expresses the alpha-1 isoform of the sodium pump, and that MBG thus can target this endothelium. If that is the case, MBG would be expected to decrease membrane potential in these cells; as a consequence, superoxide production would be up-regulated, NO synthase activity would be down-regulated, and myocardial NO bioactivity would thus be suppressed. This would offer a satisfying explanation for the impact of salt and salt-sensitivity on risk for LVH. If expression of the alpha-1 isoform of the sodium pump is a more general property of vascular endothelium, MBG may suppress NO bioactivity in other regions of the vascular tree, thereby contributing to other adverse effects elicited by salty diets: reduced arterial compliance, medial hypertrophy, impaired endothelium-dependent vasodilation, hypertensive/diabetic glomerulopathy, increased risk for stroke, and hypertension.

Atorvastatin reduces arterial stiffness in patients with rheumatoid arthritis

BACKGROUND

Chronic systemic inflammation may contribute to accelerated atherosclerosis and increased arterial stiffness in patients with rheumatoid arthritis (RA). In addition to lowering cholesterol, statins have immunomodulatory effects which may be especially beneficial in patients with RA who have systemic immune activation.

OBJECTIVE

To investigate the effect of atorvastatin on the augmentation index (AIx: a measure of arterial stiffness) and systemic inflammation in RA.

METHODS

29 patients with RA (mean (SD) age 55 (13) years) with moderately active disease of long duration were studied. AIx, lipid levels, serum inflammatory markers, and disease activity score were measured before and after 12 weeks of atorvastatin 20 mg daily.

RESULTS

AIx improved significantly from 34.1 (11.6)% to 29.9 (11)% (p = 0.0002), with the greatest improvements in AIx occurring in those subjects with the highest disease activity scores (r = -0.5, p = 0.007). Total and LDL cholesterol were reduced from 5.5 (0.9) to 3.9 (0.7) mmol/l and 3.3 (0.8) to 1.9 (0.6) mmol/l, respectively (p = 0.0001). Serum inflammatory markers remained unchanged during the study.

CONCLUSIONS

Atorvastatin significantly reduced arterial stiffness in patients with RA. The greatest improvements were seen in patients with more active disease, suggesting that, in addition to the beneficial effects of cholesterol reduction, immune modulation may contribute to the cardioprotective effect of statins.

Effects of nitric oxide synthase inhibitor on decrease in peripheral arterial stiffness with acute low-intensity aerobic exercise

We previously reported that even low-intensity, short-duration acute aerobic exercise decreases arterial stiffness. We aimed to test the hypothesis that the exercise-induced decrease in arterial stiffness is caused by the increased production of NO in vascular endothelium with exercise. Nine healthy men (age: ∼22–28 yr) performed a 5-min single-leg cycling exercise (30 W) in the supine position under an intravenous infusion of NG-monomethyl-l-arginine (l-NMMA; 3 mg/kg during the initial 5 min and subsequent continuous infusion of 50 μg·kg−1·min−1 in saline) or vehicle (saline) in random order on separate days. The pulse wave velocity (PWV) from the femoral to posterior tibial artery was measured on both legs before and after the infusion at rest and 2 min after exercise. Under the control condition, exercised leg PWV significantly decreased after exercise ( P < 0.05), whereas nonexercised leg PWV did not show a significant change throughout the experiment. Under l-NMMA administration, exercised leg PWV was increased significantly by the infusion ( P < 0.05) but decreased significantly after the exercise ( P < 0.05). Nonexercised leg PWV increased with l-NMMA administration and maintained a significantly higher level during the administration compared with baseline (before the infusion, all P < 0.05). The NO synthase blockade × time interaction on exercised leg PWV was not significant ( P = 0.706). These results suggest that increased production of NO is not a major factor in the decrease of regional arterial stiffness with low-intensity, short-duration aerobic exercise.

Arterial stiffness and wave reflection in hypertension: Pathophysiologic and therapeutic implications

Numerous studies performed in the past decade have shown that increased pulse pressure, an indicator of arterial stiffening, is associated with adverse clinical outcomes. Research is now focused on better defining the anatomic and physiologic determinants of increased pulse pressure. Early work considered aortic stiffening to be a passive, irreversible consequence of aging that was accelerated by hypertension. Recent studies suggest that aortic stiffening is dynamic and reversible and that abnormalities in aortic function may play a primary role in the pathogenesis of hypertension. This review summarizes current work on the genesis of increased pulse pressure and abnormal pulsatile load in hypertension, and underscores areas for future research.

Role of natriuretic peptides in regulation of conduit artery distensibility

Arterial distensibility, assessed by the pulse-wave velocity (PWV), is an independent predictor of cardiovascular risk. We investigated whether natriuretic peptides, acting locally, modify conduit artery distensibility in vivo. All studies were conducted in anesthetized sheep ( n = 18) by using a validated ovine hindlimb model. In brief, the PWV was calculated, with the use of the foot-to-foot methodology, from two pressure waveforms recorded simultaneously with a high-fidelity dual pressure-sensing catheter placed in the common iliac artery. Drugs were infused either proximally, via the catheter to perfuse the segment of artery under study, or distally, via the sheath to control for any reflex changes in flow or sympathetic activation. First, the effects of atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), and c-type natriuretic peptide (CNP) were studied. Second, the role of endogenous ANP was investigated by infusing the natriuretic peptide receptor type A (NPRA)-selective receptor antagonist A71915. Third, A71915 was coinfused with ANP. Fourth, the NPRC-selective agonist cANF was infused. Infusion of CNP or des-[Gln18Ser19Gly20Leu21Gly22]-ANF-(4-23)-NH2 (cANF) had no effect on iliac PWV. However, infusion of ANP, and to a lesser degree BNP, resulted in a reduction in PWV (−9%; P < 0.01 and −6%; P < 0.05, respectively). A71915 increased iliac PWV from 2.97 ± 0.13 to 3.06 ± 0.13 m/s; P < 0.01. Coinfusion of A71915 with ANP completely abolished the effects of ANP ( P < 0.01). Importantly, ANP-BNP infusion via the sheath did not alter PWV. In conclusion, ANP, and to a lesser extent BNP, modify large artery distensibility via the NPRA receptor. Neither CNP nor cANF altered PWV, suggesting that the NPRB and NPRC receptors do not acutely influence distensibility in vivo.

Relationship between albumin excretion rate and aortic stiffness in untreated essential hypertensive patients

OBJECTIVES

To evaluate, in a group of nondiabetic essential hypertensive patients with normal renal function, the relationship between albumin excretion rate (AER) and carotid-femoral pulse wave velocity (PWV), as an index of aortic stiffness.

DESIGN

Cross-sectional study.

SETTING

Outpatient hypertension clinic.

SUBJECTS

Seventy patients with mild-to-moderate essential hypertension, aged 42 +/- 8 years, never pharmacologically treated. All subjects underwent routine laboratory tests, 24-h ambulatory blood pressure (BP) monitoring, measurement of carotid-femoral PWV, by means of a computerized method, and AER.

RESULTS

Microalbuminuric patients (AER > or = 20 microg min(-1); n = 19), when compared with normoalbuminuric subjects, showed more elevated 24-h BP (136/88 +/- 10/10 vs. 128/83 +/- 7/6 mmHg; P < 0.001 and P = 0.013, for systolic and diastolic BP respectively) and higher values of carotid-femoral PWV (10.4 +/- 2 m s(-1) vs. 9.2 +/- 1.3; P = 0.006). This latter difference remained statistically significant, even after correction by ancova for 24-h systolic and diastolic BP, and body mass index (BMI, P = 0.016). Univariate regression analysis disclosed a tight correlation between AER and carotid-femoral PWV (r = 0.42; P = 0.0003). This association was confirmed in a multiple regression model (beta = 0.35; P = 0.009) in which, as independent variables, besides PWV, 24-h BP, age, serum glucose values, smoking status, gender and BMI, were added.

CONCLUSIONS

Our results seem to confirm that microalbuminuria may represent the early renal manifestation of a widespread vascular dysfunction, and therefore it is an integrated marker of cardiovascular risk.

Confounding effects of heart rate on pulse wave velocity in paced patients with a low degree of atherosclerosis

BACKGROUND

Pulse wave velocity (PWV), an index of arterial wall stiffness, is modulated by blood pressure (BP). Whether heart rate (HR) is also a modulator of PWV is controversial. Recent research involving mainly patients with high aortic PWV have found either no change or a positive correlation between the two. Given that PWV is increasingly being measured in cardiovascular studies, the relationship between HR and PWV should be known in patients with preserved arterial wall elasticity.

OBJECTIVE

The aim of this study was to evaluate the importance of HR as a determinant of the variability in PWV in patients with a low degree of atherosclerosis.

DESIGN AND METHODS

Fourteen patients (five female, nine male; aged 68 +/- 8 years) were evaluated post pacemaker implantation due to sick sinus or carotid hypersensitivity syndromes. Carotid-femoral PWV was measured at rest and during atrial pacing at 80, 90 and 100 bpm (paced HR). Arterial femoral blood flow (AFBF) was measured by echodoppler.

RESULTS

PWV increased from 6.2 +/- 1.5 m/s (mean +/- SD) during resting sinus rhythm (HR 62 +/- 8 bpm; mean +/- SD) to 6.8 +/- 1.0, 7.0 +/- 0.9, and 7.6 +/- 1.1 m/s at pacing rates of 80, 90 and 100 bpm, respectively (P < 0.0001). Systolic (SBP) and mean blood pressure (MBP) remained constant at all HR levels, whereas AFBF increased in a linear fashion.

CONCLUSIONS

These results demonstrate that even in patients with a low degree of atherosclerosis, HR is a potential modulator of carotid-femoral PWV.

Soluble CD14 and aortic stiffness in a population-based study

OBJECTIVE

Soluble CD14 (sCD14), an effective mediator for the activation of monocytes by bacterial endotoxin is involved in the release of substances able to modify the characteristics of the arterial wall. The aim of this study was to investigate, in humans, the relationship of sCD14 with aortic stiffness and to analyse the influence of arterial structure and endothelial function on this relationship.

DESIGN

Cross-sectional population-based study.

PARTICIPANTS

One thousand and fifteen subjects randomly selected from the polling lists, were recruited by the Toulouse MONICA centre between 1995 and 1997.

METHODS

Carotid-femoral pulse wave velocity (PWV) and blood pressure (BP) were measured in the supine position. Common carotid intima-media thickness (IMT) and the presence of plaques were assessed by ultrasonography. sCD14 was measured using an immunoenzymatic method.

RESULTS

The results concern the 891 subjects with complete data for all the variables. In the bivariate analyses, PWV (P < 0.001), systolic BP (P < 0.05), pulse pressure (PP) (P < 0.01), IMT (P < 0.001), the number of plaques (P < 0.05) and von Willebrand factor activity (vWFa) (P < 0.001) were positively associated with sCD14, whereas no significant relationship was observed between sCD14 and diastolic BP. After adjustment for age and sex, no significant relationship remained between IMT, the number of plaques, SBP, PP and sCD14. A significant and positive relationship was observed between sCD14 and PWV (trend P < 0.05) after adjustment for numerous confounders.

CONCLUSION

This population-based study yields first evidence that sCD14 is associated with aortic stiffness independently of age, BP and atherosclerosis in humans.

Tamoxifen improves endothelial function and reduces carotid intima-media thickness in postmenopausal women

BACKGROUND

Tamoxifen is a selective estrogen-receptor modulator shown to improve several cardiovascular risk factors in postmenopausal women with breast cancer. In animal studies tamoxifen inhibits the progression of atherosclerosis. Although the presence of a history with tamoxifen treatment is related to a lower intima-media thickness (IMT) of the common carotid artery, data from controlled follow-up studies are lacking to support this observation.

METHODS

We examined 14 postmenopausal women with early stage breast cancer with indication for tamoxifen treatment (20 mg/d) and 13 healthy postmenopausal women. Flow-mediated dilatation (FMD) of the brachial artery, combined carotid IMT, and aortic pulse wave were measured before and 6 months after treatment in the tamoxifen group and at the same times in the control group.

RESULTS

FMD and IMT were significantly increased and decreased, respectively, in the treatment group compared to the control group (FMD: +2.2% +/- 0.9% vs +0.085% +/- 1%, P =.012; IMT: -0.088 +/- 0.03 mm vs +0.04 +/- 0.03 mm, P =.018, mean +/- standard error of the mean, treatment vs control group). These differences remained significant even when adjusted for age, duration of menopause, and cardiovascular risk factors. Low-density lipoprotein cholesterol was also significantly reduced after tamoxifen treatment.

CONCLUSIONS

Tamoxifen treatment slows the progression of atherosclerosis in postmenopausal women with breast cancer as assessed by changes in carotid IMT. An improvement in endothelial function and blood lipid profile may be the reason for this beneficial effect.

Marinobufagenin may mediate the impact of salty diets on left ventricular hypertrophy by disrupting the protective function of coronary microvascular endothelium

Individuals who eat salty diets and who are "salt-sensitive" tend to have increased left ventricular mass, independent of blood pressure; this phenomenon awaits an explanation. It is clear that local up-regulation of angiotensin II (AngII) production and activity play a key role in the induction of left ventricular hypertrophy (LVH). Recent evidence suggests that a healthy coronary microvascular endothelium opposes this effect by serving as a paracrine source of nitric oxide (NO), a natural antagonist of AngII activity, and that up-regulation of this mechanism can account for the protective role of bradykinin with respect to LVH. The coronary microvasculature also possesses NAD(P)H oxidase activity that can generate superoxide, inimical to the bioactivity of endothelial NO. There is now good reason to believe that the triterpenoid marinobufagenin (MBG), a selective inhibitor of the alpha-1 isoform of the sodium pump, mediates the impact of salty diets on blood pressure;production of MBG by the adrenal cortex is boosted when salt-sensitive animals are fed salty diets. It is hypothesized that coronary microvascular endothelium expresses the alpha-1 isoform of the sodium pump, and that MBG thus can target this endothelium. If that is the case, MBG would be expected to decrease membrane potential in these cells;as a consequence, superoxide production would be up-regulated, NO synthase activity would be down-regulated, and myocardial NO bioactivity would thus be suppressed. This would offer a satisfying explanation for the impact of salt and salt-sensitivity on risk for LVH. If expression of the alpha-1 isoform of the sodium pump is a more general property of vascular endothelium, MBG may suppress NO bioactivity in other regions of the vascular tree, thereby contributing to other adverse effects elicited by salty diets: reduced arterial compliance, medial hypertrophy, impaired endothelium-dependent vasodilation, hypertensive/diabetic glomerulopathy, increased risk for stroke, and hypertension.

Endothelial function and mechanical properties of the common carotid artery in children on parenteral nutrition

Intravenous administration of nutrition mixtures induces endothelial damage and arterial wall remodeling in animal models. To study endothelial function and common carotid artery mechanical properties in children receiving parenteral nutrition, we used noninvasive ultrasonic measurements in 18 children on parenteral nutrition and 18 controls. No difference appeared in the geometry of the common carotid artery (intima media thickness, systolic and diastolic diameters) between the patients on parenteral nutrition and the controls. The incremental elastic modulus was significantly higher in the patients on parenteral nutrition (1.8 +/- 0.4 versus 1.4 +/- 0.5 4 mm Hg x 10(3), p < 0.05) reflecting alteration of the elastic properties of the arterial wall independent of the vessel geometry. The flow-mediated dilatation of the brachial artery was significantly lower in the patients on parenteral nutrition (6 +/- 3 versus 8 +/- 3%, p < 0.05), whereas the dilatation after glyceryl trinitrate administration was similar (22 +/- 9 versus 25 +/- 9%). Children on parenteral nutrition exhibit endothelial dysfunction and altered stiffness of the common carotid artery. The noninvasive methods used in this study may prove useful for objectively determining the effects of various preventive methods.

Acute hyperhomocysteinemia induces a reduction in arterial distensibility and compliance

OBJECTIVE

The aim of the study was to evaluate the effects of acute hyperhomocysteinemia on distensibility and compliance of large peripheral arteries. Isoprostanes generation and antioxidant vitamins were used to assess the role of oxidative stress.

DESIGN

A cross-over, double-blind study on distensibility (DC: distensibility coefficient) and compliance (CC: cross-sectional compliance) of common femoral and brachial arteries was performed in 12 healthy young male volunteers by means of a wall track system before and 4 h after a single oral methionine (100 mg/kg) or placebo administration. The effects of methionine load were investigated also after oral administration of vitamin C (1g/day) and vitamin E (800 mg/day) for 8 consecutive days.

RESULTS

Oral methionine induced a significant increase in plasmatic levels of homocysteine. Distensibility and compliance of brachial and femoral arteries were significantly reduced after methionine load in comparison to placebo. This acute impairment of arterial wall mechanical properties was associated to endothelial dysfunction, since altered flow-dependent vasodilatation (P < 0.05 versus placebo) was observed in the same arterial districts. A significant increase in urinary 8-iso-prostaglandin F2alpha was observed after methionine. Pretreatment with vitamins C and E prevented the effects of methionine on femoral and brachial arteries as well as on urinary 8-iso-prostaglandin F2alpha excretion.

CONCLUSIONS

Hyperhomocysteinemia seems responsible for altered arterial wall elasticity and for endothelial dysfunction. A pivotal role can be attributed to oxidative stress.

Inflammation and arterial stiffness in systemic vasculitis: a model of vascular inflammation

OBJECTIVE

Arterial stiffness, an independent determinant of cardiovascular risk, is regulated by both structural and functional factors, including endothelium-derived nitric oxide. Endothelial dysfunction is associated with acute and chronic systemic inflammation. However, the role of systemic inflammation in arterial stiffening has not been determined. The aim of this study was to investigate the relationship between inflammation and arterial stiffness in patients with antineutrophil cytoplasmic antibody-associated systemic vasculitis (AASV) as a model of systemic inflammation.

METHODS

Thirty-one patients with AASV (15 with active disease) and 32 age-matched controls were studied. Pulse wave velocity (PWV) and the augmentation index (AIx) were assessed noninvasively and related to serum levels of C-reactive protein (CRP), interleukin-6, and tumor necrosis factor alpha.

RESULTS

In subjects with active disease, the AIx, PWV, and level of CRP were elevated compared with that in controls (mean +/- SEM 31 +/- 3% versus 22 +/- 2% [P = 0.003], 9.2 +/- 0.7 versus 7.5 +/- 0.3 meters/second [P = 0.03], and 16.0 +/- 4.0 versus 1.1 +/- 0.1 mg/liter [P < 0.001], respectively). However, PWV and the AIx were not significantly different between patients with disease in remission and controls (8.0 +/- 0.5 versus 7.5 +/- 0.3 meters/second and 19 +/- 3% versus 22 +/- 2%, respectively). The CRP level was positively correlated with both PWV and the AIx. Multiple regression analysis indicated that age, mean arterial pressure (MAP), and CRP were independently related to PWV, and that age, MAP, CRP, sex, and heart rate were associated with the AIx.

CONCLUSION

These data indicate that AASV is associated with increased arterial stiffness, and that stiffness correlates with the degree of active inflammation.

Interrelationship between non-invasive measurements of atherosclerosis: flow-mediated dilation of brachial artery, carotid intima-media thickness and pulse wave velocity

Flow-mediated dilation (FMD) of the brachial artery, carotid intima-media thickness (IMT) and pulse wave velocity (PWV) have been shown to be good surrogate markers of clinical atherosclerosis. We determined the interrelation between these measurements, and examined whether their combination would be of clinical significance. One hundred and thirty-five consecutive subjects (79 women/56 men) were enrolled, including 110 patients with risk factors for atherosclerosis, and 33 patients with atherosclerotic disease such as coronary heart disease, stroke or arteriosclerosis obliterans. IMT and plaque formation of the carotid artery and FMD of the brachial artery were assessed using ultrasonography. Brachial-ankle PWV (baPWV) was measured using an automated device (form ABI/PWV, Colin). Age, FMD, IMT and PWV were significantly correlated with each other. Multivariate analysis revealed an independent correlation between the parameters except for FMD, and all four parameters were independently correlated with each other in subjects <70 years. Next, we classified the subjects by tertile according to the values of FMD, IMT and PWV. Each of the worst tertiles was associated with a higher prevalence of atherosclerotic disease and carotid plaques compared to the other tertiles. Moreover, subjects with the worst tertiles of all three measurements had a markedly higher prevalence of atherosclerotic disease and carotid plaques. These results suggest that FMD, IMT and PWV are related to each other, but the combination of these measurements will be of stronger clinical relevance.