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Biomedical subjects

N P Chau

Publications and source records attributed to N P Chau.

At least 19 recordsLinked to original sources

Blood pressure and serum lipids in hypertensive men and women aged 60-97 years.

OBJECTIVE: To report a large set of observations on blood pressure and blood lipids including high-density lipoprotein cholesterol in male and female hypertensive subjects aged 60 years or above. METHODS: Data on blood pressure (BP), total cholesterol (C), and high-density lipoprotein cholesterol (HDL-C) were made available on 5310 hypertensive subjects aged 60-97 years, from a European study on the effects of urapidil, a multifactorial antihypertensive agent (alpha 1-adrenoceptor antagonist+control 5HT1A-receptor stimulant). Observations before treatment were analysed to assess the male-female difference and the changes with age of BP and serum lipids. The subjects were divided into 7 groups, aged 60-62, 63-65, 66-68, 69-71, 72-76, 77-79, and 80+, respectively, and a 2-factor ANOVA (sex and age groups) was used. RESULTS: Systolic BP increased with increasing age in both sexes (p < 0.0001). Over the whole age range, SBP was higher in women than in men (p < 0.0001). Diastolic BP remained unchanged in men and decreased with increasing age in women (p < 0.001). The C level was almost the same in men as in women, but tended to decrease with increasing age in women (p < 0.05). HDL-C was unchanged in men, but increased with increasing age in women (p < 0.006). In all age ranges, the HDL-C level was higher in women than in men (p < 0.0001). CONCLUSION: This study reports observations on BP and serum lipids in a large sample of hypertensives subjects aged 60-97 years. This type of data, especially on high-density lipoprotein cholesterol, is rare in the elderly.

Aged

Pharmacokinetic-pharmacodynamic modeling between pinacidil or pinacidil-N-oxide plasma levels and systemic and regional hemodynamic effects in healthy volunteers.

Pinacidil (P) lowers blood pressure through peripheral vasodilation, but also induces dose-dependent side-effects. In a previous placebo-controlled, randomized, double-blind and crossover study, performed in six healthy male volunteers, we investigated the systemic and regional hemodynamic effects of a single oral administration of 25 mg of P (sustained-release form) and measured the plasma concentrations of P and of its active metabolite, pinacidil-N-oxide (PO). In the present study, our goal has been to investigate the relationships between P and/or PO plasma concentrations and P administration effects on systolic, diastolic and mean arterial pressures (SAP, DAP, MAP), heart rate (HR), cardiac output (CO), total peripheral resistance (TPR), brachial and carotid arteries' diameters (BAD, CAD), flows (BAF, CAF) and vascular resistances (BVR, CVR) which were assessed before and at different time intervals after drug intake. Concentration-effect relationships were investigated using both linear and log-linear multiple regression models with P, PO or both P and PO as independent variables (six models). Significant linear relationships were observed between P and/or PO and SAP, DAP, MAP, TPR, BAD, BAF, BVR, CAD and CVR. For example, TPR (dynes.s/cm5) = 1308-3.031 x P (ng/ml), R = 0.57, P = 0.0037; BVR (mmHg.s/ml) = 58-0.261 x P (ng/ml), R = 0.56, P = 0.0042. Almost similar R values were obtained using P, PO, or both P and PO. The use of log-linear models did not improve the fittings.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult

Use of runs test to assess cardiovascular autonomic function in diabetic subjects.

OBJECTIVE: We suggest a simple, noninvasive method to assess the autonomic function in diabetic subjects. The method requires only a monitoring of heart rate (HR) with subjects in the sitting position. RESEARCH DESIGN AND METHODS: Sixty diabetic subjects, 44 men and 16 women, between 20-80 years of age, were recruited, chronologically, for this study. Subjects treated for high blood pressure were not included. Their autonomic function was assessed by the total score of five classical cardiovascular function tests. In the same subjects and in 44 healthy subjects, blood pressure and HR were determined from beat to beat by the Finapres system with subjects in the sitting position. We examined the randomness of the HR changes by calculating the zeta statistic of the runs test on 1,000 successive HR readings (the zeta value is low if the HR changes are random). When the HR changes are random, we consider that the autonomic control of HR is impaired. RESULTS: The zeta values of HR changes were significantly lower in diabetic subjects compared with normal subjects (2.98 +/- 0.97 vs. 3.54 +/- 0.97, P < 0.004). In diabetic subjects, the zeta value was closely correlated to the total score of disautonomy (r = -0.66, P < 0.0001, after correction for age effect) and to the office systolic blood pressure (r = -0.43, P < 0.001). CONCLUSIONS: The zeta value of HR changes might be a marker of the autonomic function in diabetic subjects.

Adult

Ambulatory blood pressure in diabetic subjects.

Ambulatory blood pressure (ABP) was measured every 15 min for 24 h in 82 diabetic subjects aged 35 to 79 years and in 66 healthy controls having the same age and office blood pressure. The autonomic control in diabetic subjects was evaluated by the total score of five cardiovascular function tests (a high score means an autonomic neuropathy). The diurnal cycle of BP was assessed by the difference of BP between daytime and nighttime (delta BP = BP in the day - BP in the night). The variability of BP was evaluated by the standard deviations of the readings. Compared with control subjects, diabetic subjects had the same 24-h mean level of BP, a smaller delta BP, and an increased variability during the daytime; however, the differences were in the limit of statistical significance. Clearcut results were obtained in diabetic subjects with autonomic neuropathy. In the latter, the score of autonomic neuropathy was (1) negatively correlated to delta SBP (systolic) and delta DBP (diastolic) (r = 0.44, P = .0004 and r = 0.46, P = .0004, respectively) and (2) positively correlated to the variability of SBP and DBP during the daytime (r = 0.46, P .0004 and r = 0.29, P = .03, respectively). In diabetic subjects, mean level and variability of ABP were positively correlated to urinary microalbumin. The relationships were the most significant when one relates microalbuminuria to the level of SBP in the night (r = 0.42, P < .0003) and to the variability of SBP in the day (r = 0.32, P = .008).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult

Home blood pressure: variability, comparison with office readings and proposal for reference values. Groupe de la Mesure, French Society of Hypertension.

PURPOSE: A multicentre study was performed on 390 healthy subjects (210 male, 180 female) to evaluate home blood pressure versus office blood pressure. METHODS: The patients, aged 20-59 years, not on antihypertensive treatment, were not preselected by blood pressure levels. Blood pressure was measured in the doctor's office, using a mercury manometer at the fifth, sixth and seventh minute of rest, and at home by self-measurement using a validated electronic oscillometric device at the fifth, sixth and seventh minute of rest, in the morning and evening, on three consecutive days. RESULTS: The analysis of office and home measurements at the fifth, sixth and seventh minute of rest showed a significant decrease in blood pressure, mostly between the fifth and sixth minute. There was no significant variation in home pressure over the three consecutive days of measurement. Blood pressures were significantly higher in the evening than in the morning; the mean differences were 3 mmHg for systolic and 1.5 mmHg for diastolic blood pressure. Compared with office blood pressure measurement, home measurement provided significantly lower systolic and diastolic blood pressure means. Of the subjects, 78% showed a higher systolic and 69.9% a higher diastolic blood pressure with office measurement than with home measurement. Systolic and diastolic blood pressure differences were non-significantly higher for females than for males and did not differ with age. CONCLUSIONS: The comparison of the office and home measurement distributions allowed us to propose reference values for home blood pressure measurement. These were established by choosing blood pressure at the identical percentile for home measurement as we found for office measurement using the World Health Organization criteria (140/90 and 160/95 mmHg). Using this approach, the upper limit for normotension by home measurement would be 127/83 mmHg and for hypertension 147/86 mmHg. Although this approach has no prognostic value, it could be useful for the interpretation of home blood pressure.

Adult

Active ambulatory blood pressures and urinary electrolytes in young male subjects with normal blood pressure or borderline hypertension.

OBJECTIVES: To examine the relationship between ambulatory blood pressure (ABP) and 24-h urinary electrolytes in young subjects with normal blood pressure or borderline hypertension. DESIGN: ABP shows a circadian profile. We question whether high- and low-level pressure spans might have a relationship with urinary salt output. METHODS: ABP was monitored by the SpaceLabs 5200 system in 182 young male subjects (aged 17-25 years) with normal or borderline office blood pressure. In all subjects, 24-h urinary sodium, potassium and chloride were measured. The mean values and SD of ABP during 24 h, or during the daytime (0900-2100 h) and night-time (2115-0845 h), were estimated. In addition, using a 'cumulative sum' method, 'active' (high-level) and 'passive' (low-level) spans of APB were identified in each subject. RESULTS: No relationship was found between 24-h urinary sodium, potassium or chloride and office systolic blood pressure. Also, no relationship was found between the electrolytes and mean value or SD of ABP during 24 h, daytime or night-time. In contrast, significant positive correlations were found between 24-h urinary sodium and active systolic and diastolic blood pressure. The present study suggests that the active blood pressure span is associated with salt intake in normal and borderline blood pressure groups.

Adult

Fractal dimension of heart rate and blood pressure in healthy subjects and in diabetic subjects.

Beat-to-beat heart rate (HR) and blood pressure (BP) were measured by the Finapres system in 28 healthy subjects and 64 diabetic subjects. Autonomic controls in diabetic subjects were assessed by scoring 5 cardiovascular function tests (high score = abnormal control). The fractal dimension (FD) of HR (or SBP) was estimated as follows: Measuring the curve of 500 successive HRs with a rule of length L, one obtains N times L. The FD is the slope of the regression line of Log(N) versus Log(1/L) for different L. We found a lower FD of HR in diabetic subjects than in healthy subjects (1.35 +/- 0.10/1.44 +/- 0.09, p = 0.0002) and a similar FD of SBP in the 2 groups. In diabetic subjects, the FD of HR was negatively correlated with age (r = -0.27, p = 0.03), duration of diabetes (r = -0.33, p = 0.0078) and score of disautonomy (r = -0.43, p = 0.0007). So, heartbeat is more fractal in healthy status: a low fractal fluctuation is a sign of pathology.

Adult

[Comparative evaluation of diabetic cardiac autonomic neuropathy by spectrum analysis and Ewing's tests].

METHODS: 62 diabetic patients of both sex (age: 46 +/- 16 yr, BMI: 26.1 +/- 4 kg/m2, casual blood pressure: 134 +/- 17/81 +/- 11 mmHg, mean age of diabetes: 11 +/- 9 yr) without cardiovascular medications were recruited. Autonomic involvement was based on the results from a battery of five cardiovascular tests as suggested by Ewing. The result of each test and a scoring system was considered. All patients underwent power spectral analysis (PSA) of digital blood pressure (BP) and RR intervals recorded in the recumbent position and after tilting with a Finapres monitor. The percentage of total power (0.025-0.4 Hz) computed in the low-frequency band (0.070-0.139 Hz) computed in the low-frequency band (0.070-0.139 Hz) was chosen as a sympathetic index (sigma Ind). Results of tests were correlated with sigma Ind. RESULTS: 24 patients (39%) have an autonomic involvement. The most affected tests are: the Valsalva maneuver (VAL): 16% RR response from lying to standing (LS): 25%, sustained handgrip (SHG): 30%, postural hypotension (PH); 57%, deep breathing (DB): 87%. Correlations coefficients of cardiovascular tests and sigma Ind are: VAL/sigma Ind (SBP tilt): r = 0.277, p = 0.029; Val/sigma Ind (DBP tilt): r = 0.318, p = 0.012; VAL/sigma Ind (RR tilt): ns. PH/Ind sigma (SBP tilt): r = 0.391, p = 0.0017; PH/sigma Ind (DBP tilt): r = -0.296, p = 0.019; PH/sigma Ind (RR tilt): r = -0.308, p = 0.015, DB/sigma Ind (SBP tilt): r = 0.417, p = 0.0007; DB/sigma Ind (DBP tilt): r = 0.361, p = 0.0039; DB/sigma Ind (RR tilt): ns. Results of LS and SHG show no correlation with Ind sigma. Correlations between global autonomic score (GAS) and sigma Ind during tilting have the following values: GAS/sigma Ind (SBP tilt): r = -0486, p = 0.0001; GAS/sigma Ind (DBP tilt): r = -0.385, p = 0.002; GAS/sigma Ind (RR tilt): r = -0.411, p = 0.0009. CONCLUSIONS: The so-called sympathetic index computed from PSA are well correlated with autonomic tests. They allow an early detection of sympathetic involvement in diabetics patients. These results are to consider while managing these subjects.

Autonomic Nervous System Diseases

[Cardiovascular autonomic neuropathy and blood pressure variability in insulin-dependent diabetes].

The aim of this study was to analyse the role of cardiac autonomic neuropathy (CAN) in the changes of Blood-Pressure (BP) variability among insulin-dependent diabetics and to determine the relationship between BP variability and diabetic complications. Ambulatory BP monitoring was performed during 24 hours on 93 insulin-dependent diabetics and 77 normal subjects of similar age (Group 1). CAN was assessed by the cardiovascular autonomic function tests described by Ewing and the diabetics were divided in two groups: Group 2 including patients without CAN (n = 46) and Group 3 including patients with CAN (n = 47). The 24 h standard deviation (variability) and the day/night difference for systolic and diastolic BP were calculated for each subjects. Systolic and diastolic BP variability is more elevated in Group 3 than in the other groups during the diurnal period. Furthermore, the day/night difference of systolic and diastolic BP is lower in Group 3 compared to groups 2 and 3. Diabetic complications are also more frequently observed among diabetic patients with CAN (p < 0.001). So CAN seems to have two types of consequences on BP curve among diabetic patients: a decrease of day/night BP difference which can be responsible of relative hypertension during the night and an increase of BP variability. As frequency of diabetic retinopathy and nephropathy is more elevated among diabetic patients with CAN, it is possible that CAN plays a role in the occurrence of these complications. Therefore, a simple juxtaposition of these facts is also possible.

Adult

[Is placebo necessary in a clinical trial on ambulatory blood pressure?].

Placebo has only a slight effect on ambulatory blood pressure (ABP). Some authors have suggested that the use of a placebo is not necessary in a study on the drugs effect on ABP. We demonstrate that even if placebo effect is small, the use of a placebo group is still necessary. Effects of one daily dose of 50 mg atenolol + 20 mg slow-released nifedipine (AN) were investigated. Patients with office DBP 90-110 mmHg received, in a double-blind protocol, either AN (group AN, n = 31) or a placebo (group P, n = 26). Ambulatory BP (ABP) and HR were measured (Spacelabs or Diasys systems) for 24 h before and one month after treatment. The 2 groups were comparable before treatment. After 1 month under treatment, ABP was significantly lower in the AN group, compared to the P group, and this over the whole day (p = 0.03 to p < 0.0001). The effect was the most important between 10-17 h (p < 0.0001). HR was significantly lower in the AN group during daytime (6-22 h), but not during the night (22-6 h). Over the whole group, placebo effect was not significant. However, ABP did decrease under placebo in subjects with high initial pressure. As a result, an analysis without data from the placebo group led to an overestimation of the effects of the drug.

Adult

Relationship between autonomic dysfunction and BP variability in subjects with diabetes mellitus.

Autonomic vagal heart rate (HR) control, office BP and ambulatory BP were examined in 54 diabetic subjects, aged 63 +/- 6 years. Sixteen subjects were insulin-dependent. The HR response to deep breathing (the bradypnoea test) was used to evaluate the vagal HR control, and ambulatory BP was determined by the Spacelabs 5200 system (one determination every 15 minutes, for 24 hours). Twenty-seven subjects had normal office BP (SBP < or = 140 mmHg and DBP < or = 90 mmHg), seven had established hypertension (SBP > or = 160 mmHg and DBP > or = 95 mmHg) and 30 were borderline hypertensives. Over the total group, office systolic/diastolic BP (mean +/- SD) was 142 +/- 20/85 +/- 10 mmg. Systolic/diastolic ambulatory BP was 123 +/- 13/77 +/- 10 mmHg and ambulatory HR was 70 +/- 8 beats/min. Because of the small age range of our subjects, the HR score was not correlated with age (r = 0.19, NS). The HR score was not correlated with the levels of office and ambulatory pressures. In contrast, it was significantly correlated with the variability of ambulatory SBP, whether the variability was defined by the pressure standard deviation, or by the ratio SD/mean value (r = 0.40, P = 0.005 and r = 0.33, P < 0.017, respectively). We suggest that an impairment of the autonomic control in diabetics might induce an increase in variability of SBP. BP variability might play a role in the cardiovascular complications observed in diabetics.

Aged

Cholesterol and other cardiovascular risk factors in a working population in Ile-de-France (France): first results of the PCV-METRA study.

In 1989, the French PCV-METRA Group (PCV-METRA = Prevention Cardio-Vasculaire en Médecine du Travail) started a large prospective survey of cardiovascular (CDV) morbidity and mortality and of CVD risk factors, especially cholesterol, in a working population in Ile-de-France, a region including Paris. This report presents the first results of this study, based on a sample of 5758 men and 2603 women, aged 18-65 years. The variables examined included the levels of total cholesterol 1/2 (TC), High-density-lipoprotein cholesterol (HDL-C), low-density-lipoprotein cholesterol (LDL-C), and the other major CVD risk factors (smoking, sedentary way of life, hypertension, hypercholesterolemia, use of oral contraceptives and familial history of CVD risks). TC and LDL-C significantly increased with age. The changes with age were significantly different in men and women. The levels were similar in both sexes at less than 30 yrs, increased sharply for men after age 30 and were significantly higher in men than in women from 30 to 55 yrs. Beyond 55 yrs, no difference was observed between the two sexes. In contrast, HDL-C was higher in women at all age ranges. In the total sample, 35% of men and 21% of women were hypercholesterolemic (TC > or = 2.4 g/L). Our observations fully confirm and refine previous findings in the US and in other European countries. In addition, a substantial set of data on CVD risk factors for the working population in France, especially for female subjects for whom data are scanty, is now available.

Adolescent

Short-term representatives of daytime and night-time ambulatory blood pressures.

OBJECTIVE: To see whether measurements of ambulatory blood pressure during short-term daytime and night-time periods can represent complete daytime and night-time pressures accurately. DESIGN: Short-term measurements would be less uncomfortable for patients, easier to perform and could lead to fewer missing values, outliers or artefacts than full-day measurements, especially when repeated monitorings are required. METHOD: Ambulatory blood pressure was measured every 15 min for 24 h in 254 subjects with normal or borderline office blood pressure. Each pressure profile included at least 80 valid readings. Mean blood pressures for different 1-, 2-, 3-, 4-, 5- and 6-h spans were calculated and compared with mean daytime and night-time values using paired Student's t-test. RESULTS: One or two-hour spans of daytime blood pressure poorly represented mean daytime pressure. In contrast, 4-h readings, selected between 1000-2200 h represented daytime blood pressure with good accuracy. Over the total sample, 4-h mean blood pressure readings from 1000-2200 h differed from daytime readings by less than 2 mmHg and 2-h mean readings from 0300-0700 h differed from mean night-time readings by less than 1 mmHg. CONCLUSION: We suggest that 4-h measurements of ambulatory blood pressure during the daytime and 2-h measurements at night (with time spans selected as indicated as above) may be of value.

Adolescent

Ambulatory blood pressure monitoring: a critical review of the current methods to handle outliers.

OBJECTIVES: To examine the methods to handle marginal readings in the analysis of ambulatory blood pressure. DESIGN: Data obtained from automatic ambulatory blood pressure monitoring include several 'outliers', i.e. readings at the frontier of physiologically acceptable ranges. Several methods have been used to handle these readings. We need to know whether using different methods to reject outliers leads to different results in the analysis of the data. If so, then it is important that a common method be used by different authors. METHODS: Ten reported methods to handle outliers were selected and applied to a large set of unpublished blood pressure profiles (Novacor Diasys system). We compared the effects of data rejection by these methods on the mean values and standard deviations (calculated over 24 h, daytime and night-time) of the remaining data. RESULTS: The different methods had quite different effects on the same data set. Depending on the method used, the discarded data varied from 1 to 17% of the total number of readings. Among the rejected data, readings that occurred in the daytime varied from 14 to 56%. Also, 'high-value' outliers varied from 1 to 60% of the rejected data. On average over the total sample, the rejection of outliers had only a small effect on the mean values of blood pressure. In contrast, it may strongly reduce the standard deviation of the readings. CONCLUSION: The study emphasized the need to use a common method to handle outliers in the analysis of ambulatory blood pressure data.

Adult

Active and passive effects of antihypertensive drugs on large artery diameter and elasticity in human essential hypertension.

The effects of antihypertensive drugs on the large arteries consist of two parts: the passive effect due to the change in pressure and the active effect, the drug action per se. This study proposes a method of dissociating the passive effect from the active effect. The diameter of the arterial artery was determined by the pulsed Doppler method and the pulse wave velocity of the brachioradial artery by mecanography. Arterial compliance was calculated by the Bramwell-Hill formula. Active and passive effects were determined by a logarithmic pressure-diameter model. This model was supported by in situ direct measurements of blood pressure and diameter in a segment of the femoral artery in dogs. Six drugs, cadralazine, ketanserin, medroxalol, nitrendipine, captopril, and isosorbide dinitrate, administered orally, were tested in 70 essential hypertensive patients. For all drugs, the pressure reduction induced a passive decrease in arterial diameter (p less than 0.02 to p less than 0.01). Cadralazine actively decreased arterial diameter (p less than 0.01), ketanserin had no active effect on diameter, and medroxalol, nitrendipine, captopril, and isosorbide dinitrate actively increased arterial diameter (p less than 0.05, p less than 0.01, p less than 0.01, and p less than 0.01, respectively). For all drugs, the pressure reduction also induced a passive increase in arterial compliance (p less than 0.05 to p less than 0.01). However, only nitrendipine, captopril, and isosorbide dinitrate actively increased arterial compliance (p less than 0.01, p less than 0.05, and p less than 0.01, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult

Prevalence of obesity: a comparative survey in France, the United Kingdom and the United States.

We investigated the differences in the prevalence of obesity between France, the United Kingdom and the United States in 1988. The analysis was made on a total sample of 5580 subjects, representative of the population aged 16-50 years in the three countries. The same questionnaire was used in all three countries. Body mass index (kg/m2) was used to assess corpulence. Significant differences in the prevalence of obesity were observed among the three countries: 7% of the population in France was obese, 9% in the UK and 15% in the USA (P less than 0.001). There was a strikingly high percentage of very obese women (more than 50% overweight) in the USA (8% of the population) as compared to the two European countries (2% in France and 3% in the UK). In all three countries, obesity was related to sex, age, level of education, marital status, physical exercise and smoking. An inverse association was found between obesity and alcohol consumption in the USA, but not in France nor in the UK. In men, prevalence of obesity remained significantly higher in the USA than in France or in the UK when adjusting for the obesity-related factors. In women, differences in prevalence of obesity between the three countries varied according to the level of exercise, income and alcohol consumption.

Adolescent

Role of arterial compliance in the physiopharmacological approach to human hypertension.

Arterial compliance in humans is generally measured by modeling analysis of pulse tracing or of pulse wave propagation in the arterial tree. It is decreased in hypertension in part because elevation of blood pressure stiffens the arteries by stretching the rigid collagen fibres of their walls. Using a modeling evaluation of the compliance-pressure relationship in large arteries, it is possible to correct compliance from the mechanical effect (passive effect) due to pressure elevation. This makes it possible to show that, at the same pressure as in normal controls, hypertensive patients maintain decreased arterial compliance. This finding suggests that functional and/or structural changes other than pressure-mediated stretching of arteries (active effect) contribute toward reducing arterial compliance. Thus, the response of compliance to antihypertensive drugs must be studied by differentiating between passive and active effects. The diameter and compliance-pressure relationship in arteries allow differentiation of a passive arterial effect due to the pressure-lowering action of the drug, and an active pharmacological effect calculated at the same pressure before and after drug administration. Four drugs--ketanserin, urapidil, nitrendipine, and nicardipine (acute administration)--are given as examples. No active or passive compliance changes are observed with urapidil and ketanserin. In contrast, an active increase in compliance is observed in isobaric conditions with calcium antagonists, together with large-artery dilation due to a potent smooth muscle-relaxing effect. This active increase in compliance is potentiated by a passive increase due to the pressure-lowering effect that reduces the mechanical stretch exerted by blood pressure on arterial bioelastomers. Finally, an optimum increase in arterial compliance is achieved by drugs that vasodilate large arteries by smooth muscle relaxation and concomitantly decrease blood pressure. This may be of importance because low compliance has adverse effects on the cardiovascular system by contributing to the pathogenesis of systolic hypertension and left ventricular hypertrophy. Loss of arterial compliance may also be an early marker of atherosclerosis.

Antihypertensive Agents