Comparative effects of aging in men and women on the properties of the arterial tree.

OBJECTIVES: We measured the properties of the arterial tree, seeking differences between men and women as they aged. BACKGROUND: There are many differences between men and women, besides menopause, which might account for such disparities. These include body height, heart rate, stroke volume and smaller arterial diameters. Any gender differences in arterial stiffness could influence pulse pressure (PP), now recognized as a cardiovascular risk factor. METHODS: A total of 530 patients (347 men and 183 women) were classified by age into quartiles: < or = 40, 41-47, 48-54 and > or = 55 years. The middle groups represented the menopausal years. Studies included brachial artery blood pressure (BP), aortic pulse wave velocity (PWV), B-mode ultrasonography and wave form analysis of the common carotid artery (CCA), with its conversion to the aortic wave formin. Standard echocardiography provided left ventricular dimensions and flows. Calculated values included CCA compliance and distensibility, systemic compliance, stroke volume and peripheral resistance. RESULTS: At all ages, women had higher heart rates but lower BP than men. Pulse pressure, however, was lower in young women and higher in older women. Measurements influenced by body size, such as CCA diameter, compliance and systemic compliance, were lower in women. Those related to arterial wall properties, such as CCA and aortic distensibility, were the same. Although aortic PWV rose similarly with aging, PWV had more of an influence on PP in women than did mean BP. The reverse was true in men. CONCLUSIONS: Despite lower mean BP and similar arterial distensibilitvy, women develop a higher degree of pulsatility with aging, as compared with men. This is mainly due to their smaller physical characteristics, independent of the role of menopause and its related hormonal changes.

An indirect approach for the study of the elastic modulus of the brachial artery in patients with essential hypertension.

An indirect approach for the study of the changes in the incremental circumferential modulus (E) of the brachial artery after arteriolar vasodilatation was undertaken in patients with sustained essential hypertension. The product of E and the thickness (h) of the arterial wall was evaluated by means of the Moens-Korteweg equation using determinations of brachioradial pulse wave velocity and brachial artery diameter with pulsed Doppler methods. In three homogeneous groups of patients with hypertension the Eh product was studied after vasodilatation caused either by nitrendipine, a calcium entry blocking agent, or by medroxalol, an alpha and beta blocking agent, or by isosorbid dinitrate. The three drugs caused similar reductions in blood pressure and increases in arterial diameter and hence decreases in wall thickness. Variance analysis for multigroups indicated that the decrease in Eh after vasodilatation was significant for nitrendipine but not for medroxalol and isosorbid dinitrate. Covariance analysis showed that for any level in Eh product the decrease in Eh was higher for nitrendipine than for isosorbid dinitrate and medroxalol. Since the three drugs had comparable mechanical and geometrical effects, the study provided evidence that, in men with essential hypertension, the smooth muscle tone of the brachial artery was significantly more sensitive to calcium inhibition than to autonomic blockade, causing a more important decrease in elastic modulus.

Large artery dilation produced by converting enzyme inhibition in hypertension: therapeutic aspects.

Large artery dilation is produced by angiotensin-converting enzyme inhibition in hypertensive subjects despite a significant blood pressure reduction. The resulting increase in arterial compliance may be due both to blood pressure decrease and to arterial smooth muscle relaxation. In healthy volunteers and in hypertensive subjects, dosages causing large artery dilation seem to be higher than those causing pure arteriolar dilation with resulting blood pressure reduction. Similar findings have been noted to obtain compliance enhancement. Such results may be important in considering antihypertensive therapy, particularly when remodeling of the cardiovascular system is considered in long-term treatment.

Ambulatory blood pressure measurement, smoking and abnormalities of glucose and lipid metabolism in essential hypertension.

OBJECTIVE: Casual (mercury sphygmomanometer) and ambulatory blood pressure measurements were determined in 61 subjects with sustained essential hypertension. DESIGN: Patients were classified into three subgroups: smokers or non-smokers; patients with or without hyperglycemia; and patients with or without plasma lipoprotein abnormality. Mean casual blood pressure were shown to be identical in these three subgroups. RESULTS: When ambulatory blood pressure was analyzed, smokers exhibited a significant increase in pulse pressure exclusively during the activity period, whereas diastolic blood pressure and mean arterial pressure (MAP) were not modified in comparison with controls. Patients with abnormal plasma glucose showed a significant increase in systolic and pulse pressure during both activity and non-activity periods, with a slight increase in MAP during the activity period. Patients with and without plasma lipid abnormality displayed similar ambulatory blood pressure. CONCLUSION: The study provides evidence that, in spite of similar casual blood pressure levels among smokers and non-smokers, as well as among those with elevated fasting glucose levels, smokers and patients with hyperglycemia have a higher systolic and pulse pressure during 24-h monitoring, pointing to the possible role of cyclic stress in the deterioration in the structure of the hypertensive arterial wall.

Racial differences in aortic stiffness in normotensive and hypertensive adults.

OBJECTIVE: To investigate whether differences exist in the mechanical properties of large arteries between white and black subjects. DESIGN: Eighty-two white (49 normotensive and 33 untreated hypertensive) and 38 black (24 normotensive and 14 untreated hypertensive) adult male volunteers were studied in a cross-sectional study. METHODS: Carotid-femoral pulse wave velocity was measured as an index of arterial stiffness, using a recently developed non-invasive automatic device, and compared between white and black subjects before and after the adjustment for age. The slope of regressions for pulse wave velocity and systolic blood pressure were also compared between racial groups. RESULTS: In the normotensive group, white subjects presented higher mean values of pulse wave velocity than blacks while the opposite behavior was found in the hypertensive group. After adjustment for age, significant differences in pulse wave velocity between whites and blacks became evident in the normotensive (whites 8.15 +/- 0.04 versus blacks 7.75 +/- 0.02 m/s; P < 0.001) and hypertensive (whites 8.88 +/- 0.02 versus blacks 9.30 +/- 0.17 m/s; P < 0.001) groups. Linear regression analysis for age-adjusted pulse wave velocity and systolic blood pressure showed that the slope was significantly greater in blacks than in whites (0.040 +/- 0.002 versus 0.019 +/- 0.001 m/s; P < 0.001). CONCLUSION: These data indicate that there is a greater pressure-dependent increase in aortic stiffness in blacks than in whites. This finding points towards major differences in mechanical properties of large arteries between these racial groups.

Non-invasive ambulatory blood pressure variability and cardiac baroreflex sensitivity.

AIM: The objective of this study was to evaluate the relationship between non-invasive ambulatory blood pressure variability and cardiac baroreflex sensitivity in hypertensive patients. SUBJECTS AND METHODS: Ambulatory blood pressure measurements (15-min intervals for 24 h) and continuous blood pressure measurements (Finapres, 20 min at rest after a 10-min resting period) were performed in 123 untreated hypertensives (resting diastolic blood pressure > or = 90 mmHg; 80 males, 43 females; mean +/- SD age 49 +/- 12 years, range 19-73). Fourier series were used to model 24-h blood pressure profiles (four harmonics). Ambulatory blood pressure variability was assessed by determination of the residuals in each 24-h blood pressure profile (measured minus predicted pressures). Resting blood pressure variability was defined as the SD of the mean Finapres value. Baroreflex sensitivity was evaluated by automatic detection of blood pressure and pulse interval sequences of > or = 3 beats when systolic blood pressure and pulse interval sequences changed in the same direction (increase or decrease: 1 mmHg for systolic blood pressure and 4 ms for RR interval), and was assessed as the slope of the regression line for each sequence. RESULTS: Ambulatory systolic blood pressure variability increased with age (r = 0.28*) and systolic pressure (r = 0.44**). Baroreflex sensitivity (increasing systolic pressure/pulse interval) decreased significantly with age (r = -0.48**) and systolic pressure (r = -0.23**), and was significantly related to increased ambulatory blood pressure variability (r = -0.33**). In a multivariate stepwise analysis the relationship between ambulatory blood pressure variability and baroreflex sensitivity (increasing systolic pressure/pulse interval) was statistically independent of age and systolic pressure (R = 0.55, P<0.001); this relationship was not observed with the corresponding decreasing sequence. CONCLUSIONS: This study shows that in uncomplicated hypertension, ambulatory blood pressure variability is related to baroreflex sensitivity independently of the blood pressure level. This finding has prognostic implications for this non-invasive measurement, which needs to be confirmed by large longitudinal studies.

Ambulatory blood pressure profile after carotid endarterectomy in patients with ischaemic arterial disease.

OBJECTIVE: To assess the circadian blood pressure profile observed 3 months after endarterectomy. DESIGN: Twenty-five patients undergoing unilateral or bilateral carotid endarterectomy were compared with a control population of 20 patients, matched for age, sex, weight and drug therapy. Casual mean blood pressure measured by mercury sphygmomanometry was similar in both groups. RESULTS: Non-invasive ambulatory blood pressure monitoring showed that, whereas mean arterial pressure was identical in both groups, the group undergoing surgery had a significant increase in pulse pressure and its variability over 24 h. Such abnormalities predominated during the nocturnal period, in which the reduction in systolic blood pressure was less pronounced in the operated group than in controls. For all parameters there was no significant difference between subjects with unilateral or bilateral endarterectomy. CONCLUSION: This study provides evidence that patients with carotid endarterectomy were characterized in the long term by an increase in the pulsatile component of blood pressure and its variability, in association with a disturbance in the physiological circadian rhythm. Such findings were not identified using casual blood pressure measurements.

Comparison of effects of felodipine versus hydrochlorothiazide on arterial diameter and pulse-wave velocity in essential hypertension.

In a double-blind cross-over study, the arterial changes produced by hydrochlorothiazide were compared with those observed after the calcium antagonist felodipine in 16 patients with mild to moderate systemic hypertension. Diameter changes at the site of the common carotid and brachial arteries were investigated using pulsed Doppler velocimetry, and pulse-wave velocities of the aortic, brachial and femorotibial areas were measured using standard noninvasive techniques. Whereas hydrochlorothiazide and felodipine similarly decreased blood pressure, hydrochlorothiazide did not change pulse-wave velocity, and the diameters of the brachial and common carotid arteries. Felodipine significantly decreased pulse-wave velocity, and increased brachial arterial diameter and compliance, with no change in carotid arterial diameter. Evidence was found that although felodipine had specific effects on the arterial system of hypertensive subjects, hydrochlorothiazide did not produce any sizable arterial change. These differential effects may influence specifically the heart afterload, with important consequences for diuretics that are known to cause minimal changes in cardiac structure and function.

Effect of bisoprolol on blood pressure and arterial hemodynamics in systemic hypertension.

Blood pressure, heart rate, common carotid and brachial arterial hemodynamics using pulsed Doppler flowmetry and pulse wave velocity determinations were evaluated using a double-blind crossover design versus placebo in 14 patients with sustained essential hypertension treated by the selective beta 1 blocking agent bisoprolol. Blood pressure and heart rate significantly decreased after bisoprolol, whereas no significant change occurred in the diameter, the blood flow and in the vascular resistance of the carotid and brachial circulations. Pulse wave velocity significantly decreased in the brachioradial and the carotid femoral areas. The decrease in the latter was -1.6 +/- 0.8 m/s with bisoprolol and -0.06 +/- 0.80 m/s with placebo (p = 0.001). Brachial artery compliance significantly increased from 117 +/- 49 to 205 +/- 84 cm4 x dynes-1 x 10(9) (p = 0.001), indicating that the antihypertensive effect of beta 1 blockade is associated with an improvement in the viscoelastic properties of the brachial artery wall.

Arterial distensibility and ambulatory blood pressure monitoring in essential hypertension.

Arterial distensibility estimated by carotid femoral pulse wave velocity was evaluated in 22 patients with sustained essential hypertension, together with 3 different methods of blood pressure (BP) measurement: mercury sphygmomanometer, semiautomatic BP recording using the Dinamap apparatus and 24-hour ambulatory BP monitoring using a Spacelabs monitor. Although pulse wave velocity did not correlate with BP measured by mercury sphygmomanometer, it strongly and positively correlated with BP measurements using the other 2 procedures. The best correlation was observed with ambulatory BP with respect to systolic BP only (r = 0.685, p less than 0.001). Since cardiovascular morbidity and mortality in hypertensive patients is mainly related to lesions of the large arteries, the determination of pulse wave velocity together with ambulatory BP measurements is proposed for the evaluation of cardiovascular risk.

Distension capacity of the carotid artery and ambulatory blood pressure monitoring. Effects of age and hypertension.

In hypertension, the principal components of the mechanical stress acting on the arterial wall may be evaluated not only from the level of peak systolic and end-diastolic blood pressure but also by the level of pulse pressure and variability of blood pressure measured by ambulatory monitoring. The purpose of the present study was, in a population of 51 subjects with essential hypertension, to determine the influence of these parameters and of heart rate on the distension capacity of the common carotid artery, measured noninvasively by high-resolution echo-tracking techniques. The pulsatile change in diameter of the carotid artery diameter, estimated either in absolute or relative values, was shown to be significantly and independently correlated with four mechanical parameters deduced from daytime ambulatory blood pressure measurements: baseline diastolic blood pressure (the lower the diastolic blood pressure, the higher the distension capacity; r = -0.44; P < .001); pulse pressure (the higher the pulse pressure, the higher the distension capacity; r = 0.32; P < .024); variability of diastolic blood pressure (the higher the variability, the higher the distension capacity; r = 0.37; P < .008); and mean heart rate (the higher the heart rate, the more reduced the distension capacity; r = -0.28; P < .05). Multiple regression analysis indicated that mean diastolic blood pressure and its variability, mean heart rate, and pulse pressure acted independently on carotid artery distension, even after adjustment for age. The present study suggests for the first time that, in humans, hypertension may act on the arterial wall not only through the amplitude of peak systolic and end-diastolic blood pressure but also through several other mechanical factors involving the level of pulse pressure and heart rate and also blood pressure variability. Thus, in addition to the level of blood pressure, carotid artery distension is specifically influenced by two factors independently implicated in the epidemiologic cardiovascular risk: pulse pressure and heart rate.

Enhanced brachial artery compliance following perindopril in essential hypertension.

Brachial artery mean arterial pressure (MAP), blood flow velocity (BFV), blood flow (BF), and arterial compliance (AC) were measured using pulsed Doppler systems in patients with sustained essential hypertension. The hemodynamic investigation was performed before (T0) and after 3 months (T1) of chronic treatment with the converting enzyme inhibitor Perindopril and after a further month with placebo (T2). Following treatment with Perindopril, BFV, BF, and AC significantly increased while MAP significantly decreased. The changes in AC and BFV were negatively and significantly correlated both between T0 and T1 and between T1 and T2. The study showed that the increase in arterial compliance produced by Perindopril was inversely related to the extent of arteriolar dilatation, indicating that factors other than the blood pressure reduction itself were involved in the brachial artery changes.

Converting enzyme inhibition: dissociation between antihypertensive and arterial effects.

In this study the dose-response curves reflecting the arterial and the antihypertensive effects of converting enzyme inhibition were analysed. The BP measurement (using a random zero sphygmomanometer) and its decrease following converting enzyme inhibition were used as a marker of the arteriolar effect of the drug. The effect on conduit arteries was evaluated through determination of carotid-femoral pulse wave velocity used as an index of arterial distensibility. We compared the dose-response curves of these two parameters in a double-blind study carried out in 24 patients with essential hypertension, who were randomised between placebo and 2, 4 and 8 mg of the converting enzyme inhibitor trandolapril given for 8 days. The antihypertensive effect was observed from 2 mg, at which dose the plateau of BP reduction was already achieved. No significant correlation was found between dose and BP reduction (r = -0.34), whereas the dose was significantly related to the change in pulse wave velocity (r = -0.56, P < 0.01). No significant correlation was found between changes in BP and change of pulse wave velocity. The study provides evidence that the effect on the conduit artery was obtained for higher doses than the BP effect in patients treated for hypertension by the converting enzyme inhibitor trandolapril.

Haemodynamic effects of perindopril in essential hypertension.

Blood pressure, forearm arterial haemodynamics and echocardiographic parameters were studied in patients with sustained essential hypertension before and after administration of the ACE inhibitor, perindopril. In a single blind study versus placebo, perindopril significantly reduced BP and at the same time increased brachial artery diameter, blood flow and compliance. As part of the haemodynamic investigation, a 5 minute wrist occlusion was performed. During this period, blood flow velocity and arterial diameter decreased but the reduction in diameter was smaller with perindopril after one year's treatment showing an increase in brachial artery diameter. This result indicates that the increase in brachial arterial diameter following perindopril could not be explained solely on the basis of a flow dependent dilation. When perindopril was withdrawn after three months of treatment and replaced by placebo for four weeks, BP and forearm arterial haemodynamics returned towards baseline values. However, cardiac mass which was significantly decreased after perindopril remained decreased four weeks after cessation of treatment. In the seven normalised patients, perindopril was continued for one year; arterial compliance remained increased and cardia mass diminished. The study showed that the arterial changes caused by perindopril involved a drug-related relaxation of arterial smooth muscle and that there was a differential response in cardiac and arterial changes following long term treatment.

Age- and sex-related changes in the ratio between ankle and brachial systolic pressure in normal subjects.

The ratio between ankle (ASP) and brachial (BSP) systolic pressure was studied by using Doppler ultrasound in 198 normal subjects aged between twenty and ninety years: 97 males and 101 females. The ASP/BSP ratio decreased significantly with age both in males (r = -0.64; p less than 0.001) and in females (r = -0.72; p less than 0.001). In males, the decrease in the ratio with age was due to a significant decrease in ASP with age (r = -0.52; p less than 0.001), whereas BSP did not increase significantly with age. In females, a different result was observed, since only BSP (and not ASP) was significantly (and positively) correlated with age. In both sexes, the diameter of the terminal abdominal aorta measured by echocardiography was significantly increased with age, and full examination with Doppler ultrasound excluded any significant arterial stenosis of the lower limbs. The study provided evidence that age- and sex-related changes in arterial wave transmission do exist in normal subjects.

[Cardiac hypertrophy and arterial compliance after antihypertensive treatment]. / Hypertrophie cardiaque et compliance artérielle après un traitement antihypertenseur.

Cardiac hypertrophy in hypertension is related to increased peripheral vascular resistance and reduced aortic compliance. Non-invasive measurement of pulse wave velocities and systolo-diastolic variations of the diameter of the aortic arch show that an increase in the elastic modulus of the aorta is closely related to the increase in cardiac mass. This relationship holds even after correction for mean arterial pressure. Therefore, it has been suggested that, in hypertension, the decreased aortic compliance leads to a disproportionate increase in systolic blood pressure and end systolic wall stress, predisposing to cardiac hypertrophy. The blood pressure, arterial haemodynamics of the forearm (by pulsed Doppler flow measurement) and echocardiographic parameters were studied in 16 patients with permanent essential hypertension, before and 3 months after treatment with perindopril, an ACE inhibitor. In a simple blinded study versus placebo, perindopril was shown to significantly reduce the blood pressure (p less than 0.01) while brachial blood flow increased (p less than 0.01) because of a simultaneous increase in blood flow velocity and arterial diameter. During 5 minutes' occlusion at the wrist, blood flow velocity decreased more in patients taking perindopril than those on placebo (p less than 0.01) whilst the reduction in arterial diameter was equivalent, indicating that the increase in arterial diameter with perindopril could not be explained by flow-dependent dilatation alone but by a direct effect of the drug on the artery. During the treatment phase, brachial arterial compliance increased (p less than 0.01) and pulse wave velocity decreased (p less than 0.01) and there was no change in arterial shear stress defined as the product of mean blood pressure and arterial diameter.(ABSTRACT TRUNCATED AT 250 WORDS)

[Ambulatory registration of arterial pressure during treatment with perindopril. Effects on systolic pressure and hemodynamic implications]. / Enregistrement ambulatoire de la pression artérielle lors d'un traitement par le perindopril. Effets sur la pression systolique et implications hémodynamiques.

The effects of perindopril on the 24-hour arterial pressure levels were evaluated by ambulatory recording in 21 patients (mean age 48 +/- 2 years) with mild to moderate hypertension. At the end of a 3 months treatment with perindopril (4 to 8 mg per day in one dose), comparison by variance analysis of the mean values of arterial pressure over 24 hours before and after treatment showed a significant decrease of SAP (from 144 +/- 3 to 133 +/- 3 mmHg, p less than 0.01) and DAP (from 95 +/- 2 to 87 +/- 2 mmHg, p less than 0.01). The fall in arterial pressures was more pronounced during day-time (7 a.m. to 10 p.m.) than at night. Particular attention was paid to the reduction of systolic pressure owing to its relation with arterial compliance. There was a significant correlation between ambulatory recordings of SAP and DAP before and after treatment (r = 0.82 and 0.76 respectively, p less than 0.001). Calculation and comparison of the corresponding regression slope showed that for any given level of DAP, SAP was lower after than before treatment. This effect is related to the increase of arterial compliance observed after treatment with perindopril, as already reported by other authors.

Large artery stiffness in hypertension.

EFFECTS OF HYPERTENSION ON LARGE ARTERIES: The mechanical properties of large arteries make a major contribution to cardiovascular haemodynamics through the buffering of stroke volume and by propagation of the pressure pulse. A sustained increase in blood pressure often leads to stiffness of the large arteries, especially when other risk factors are present. The increased stiffness, in turn, aggravates hypertension by increasing systolic blood pressure and can induce cardiac hypertrophy and arterial lesions. Epidemiological studies strongly suggest that subjects with stiffer arteries have a high pulse pressure, and that stiffening of large arteries is associated with excess morbidity and mortality independently of other cardiovascular risk factors. ENVIRONMENTAL AND GENETIC FACTORS: Apart from high blood pressure and ageing, various environmental and genetic factors that influence the composition of the extracellular matrix of the arterial wall can increase arterial stiffness. Clinical studies suggest that the presence of some genotypes may be a particularly important risk marker for arterial stiffness, and may modulate the effects of hypertension, ageing and lipids on large arteries. EFFECTS OF ANTIHYPERTENSIVE DRUGS: The development of accurate, non-invasive methods has now made it possible to detect alterations of the large arteries. Among antihypertensive drugs, angiotensin converting enzyme inhibitors and calcium channel blockers have proved to be highly effective in improving large artery compliance, and have shown no adverse effects on metabolic factors that can alter arterial structure and function such as lipids, plasma glucose and insulin tolerance. Therefore these drugs may be particularly suitable for treating patients with increased arterial stiffness. Finally, a determination of genotypes may be helpful in the future in choosing antihypertensive therapy.

Dose optimization study of arterial changes associated with angiotensin converting enzyme inhibition in hypertension.

BACKGROUND: In treating hypertension the optimal dose of angiotensin converting enzyme (ACE) inhibitor is derived from dose-response curves that relate the quantity of drug taken to the resulting fall in blood pressure; the blood pressure fall reflects a decrease in vascular resistance and hence, a degree of arteriolar vasodilation. However, ACE inhibition dilates not only the small arteries but also the larger calibre arteries, which increases compliance. Given the differences in structure and function of large and small arteries, the optimal drug dose for a given vessel may differ according to the size and structure of the vessel. DOSE-RESPONSE EFFECTS IN CLINICAL STUDIES: Clinical studies indicate that in the brachial artery territory, larger doses are required to obtain arterial dilation than to produce a decrease in vascular resistance. In the aorta, an improvement in arterial compliance and distensibility is governed both by the fall in blood pressure and the drug dose. Finally, for the femoral artery, the degree of arterial dilation is influenced markedly only by the drug dose. APPLICATION TO TREATMENT: An understanding of the drug dose required to produce a given change in the hypertensive arterial system may have important implications for the control of blood pressure. For a given mean arterial pressure, systolic blood pressure is lower and diastolic blood pressure higher when aortic compliance is increased, a haemodynamic change commonly seen following ACE inhibition. Recent double-blind studies have shown that ACE inhibitors produced a more pronounced decrease in systolic than diastolic blood pressure. CONCLUSION: These findings indicate that the optimum doses required to improve the arterial wall in large arteries must be evaluated by long-term antihypertensive therapy.

Sodium, large arteries and diuretic compounds in hypertension.

BACKGROUND: Clinical and experimental data have shown that different antihypertensive drugs do not cause similar changes in arterial compliance for an equipotent blood pressure reduction. There are no clear data on the effects of sodium and diuretics on the visco-elastic properties of the hypertensive arterial wall. DATA ANALYSIS: Cross-sectional epidemiological studies suggest that for given values of age and blood pressure, pulse wave velocity is lower in the presence than in the absence of a low sodium intake. Longitudinal studies indicate that in hypertensive subjects, a low sodium intake is associated with a larger brachial artery diameter than that seen with a high sodium intake. In hypertension in the elderly and in severe hypertension with end-stage renal disease, a sodium overload reduces arterial compliance and distensibility independently of blood pressure changes. In animal studies, the diuretic compounds cycletanine and indapamide increase systemic and carotid compliance independently of blood pressure changes. In contrast, in a crossover study in hypertensive subjects, the diuretic agent hydrochlorothiazide did not change arterial compliance and pulse wave velocity while the calcium entry-blocker felodipine did improve these hemodynamic parameters. CONCLUSION: The studies reviewed indicate that sodium may act on the arterial wall independently of blood pressure changes. the contribution made by counter-regulatory mechanisms, which may be related to the renin-angiotensin and the sympathetic nervous systems, might explain the differences between the clinical and the experimental changes observed with diuretic compounds.