Early disturbances of ambulatory blood pressure load in normotensive type I diabetic patients with microalbuminuria.

OBJECTIVE: To compare 24-h ABP in normotensive type 1 diabetic patients with and without microalbuminuria. RESEARCH DESIGN AND METHODS: The study was a retrospective comparison of cases and matched control subjects. The first phase included 35 type 1 diabetic patients, normotensive by OMS criteria. The 23 patients with normoalbuminuria (< 15 micrograms/min) were compared with 12 patients with microalbuminuria (> or = 15 micrograms/min). In the second phase, the 12 microalbuminuric patients were paired by sex- and age-matched with 12 normoalbuminuric patients and 12 nondiabetic healthy control subjects. We measured casual systolic and diastolic BP and HR, 24-h ABP and AHR (recorded with a Spacelabs automatic recorder), and microalbuminuria. RESULTS: No correlation between microalbuminuria and casual BP was observed. Microalbuminuria was correlated significantly with diastolic 24-h APR and nocturnal systolic and diastolic ABP (r = 0.35, 0.38, and 0.33, respectively; P < 0.05) and with AHR during all time periods (24-h, r = 0.46; day, r = 0.39; night, r = 0.39; P < 0.05). Normo- and microalbuminuric patients did not differ in casual BP and HR. However, microalbuminuric patients had a significant increase in systolic 24-h ABP (119.1 +/- 8.2 vs. 113.1 +/- 8.1, P = 0.05), diastolic 24-h ABP (74.9 +/- 7.5 vs. 70.2 +/- 5.7, P = 0.04), nocturnal systolic ABP (112.8 +/- 7.1 vs. 105.8 +/- 7.9, P = 0.01), and AHR during all time periods. The same results were observed when patients were paired by age and sex. CONCLUSIONS: Normotensive microalbuminuric type 1 patients, although strictly comparable with normoalbuminuric patients for casual BP and HR, have an increased ABP and HR, especially during the night. This difference might reflect dysautonomia. Ambulatory measurement of BP and HR is more appropriate than casual measurements in hemodynamic studies of incipient diabetic nephropathies and could be proposed as an interesting tool for an early prediction of diabetic nephropathy.

Examination of variability in arterial blood pressure at rest using spectral analysis in hypertensive patients.

INTRODUCTION: We hypothesize that in essential hypertension sympathetic nervous activity is related to the development of left ventricular hypertrophy, which can be regarded as a measure of the severity of hypertension. METHODS: Using spectral analysis, we studied the short-term variability in resting blood pressure and heart rate in essential hypertensive subjects. We measured blood over 10 min using a Finapres in 88 subjects after 20 min rest. We performed echocardiography to evaluate left ventricular hypertrophy and thereby identified three groups: 23 control subjects (group I), 29 hypertensive subjects (World Health Organization criteria) without left ventricular hypertrophy (group II) and 36 hypertensive subjects with left ventricular hypertrophy (group III). None had been treated for hypertension before the study. RESULTS: The variability in blood pressure over a low-frequency period considered to be a marker of sympathetic activity was significantly increased in group II compared with groups I and III (analysis of covariance taking into account blood pressure and age). The variability in heart rate was similar in groups II and III, but both groups had a significantly reduced variability in heart rate compared with group I. CONCLUSION: These data, which examine globally, using a non-invasive method, all neurohormonal factors associated with the development of left ventricular hypertrophy, demonstrate that, in the time course of hypertension, low-frequency oscillations in blood pressure and heart rate are shifted to a lower level, presumably reflecting altered function of the sympathetic nervous system. We suggest that spectral analysis of blood pressure at rest in hypertensive patients can lead to complementary information to single measures of blood pressure and detect differences in the cardiovascular regulatory system.

Autonomic nervous system activity in dipper and non-dipper essential hypertensive patients. What about sex differences?

OBJECTIVES: To compare the autonomic nervous system activity indexes obtained from photoplethysmography in dipper and non-dipper hypertensive patients and to seek a potential influence of sex on the relation between autonomic nervous system and the nocturnal decrease in blood pressure. METHODS: We studied 245 hypertensive patients, who underwent 24 h ambulatory blood pressure monitoring (ABPM), photoplethysmographic blood pressure recording, and echocardiography. Non-dipping patients were defined as those whose nocturnal decrease in systolic blood pressure (SBP), diastolic blood pressure (DBP), or both was less than 10% of the daytime blood pressure. Spectral powers of SBP, DBP and heart rate were obtained from photoplethysmographic recordings over three main frequency bands: very low frequency (0.005-0.05 Hz), low frequency (0.05-0.14 Hz) and high frequency (0.14-0.40 Hz). RESULTS: Because their ABPM were normal (less than 135/85 mmHg; n = 33), of poor quality (n = 22) or performed at a period too far from the photoplethysmographic recording (n = 17), 66 patients were excluded from the analysis. The remaining 179 patients comprised 117 dippers and 62 non-dippers. The groups did not differ regarding clinical and echocardiographic characteristics, irrespective of sex. Low-frequency spectral powers were significantly lower in non-dippers than in dippers, whatever the signal, whereas high-frequency spectral powers did not differ significantly between the groups. The nocturnal decrease in blood pressure increased with increasing low-frequency spectral powers, but was negatively correlated with high-frequency spectral powers. Multivariate linear regression analysis identified low-frequency spectral power of SBP and clinic DBP as independent factors determining the decrease in blood pressure. After adjustment for all significant covariates, the odds of being a non-dipper did not differ between men and women. CONCLUSION: A non-dipper profile seemed to be associated, in both men and women, with lower low-frequency spectral powers compared with those in dippers, suggesting impaired sympathetic arterial modulation.

Arterial mechanics predict cardiovascular risk in hypertension.

Systolic and diastolic blood pressures are the exclusive mechanical factors considered as predictors of cardiovascular risk for members of populations of normotensive and hypertensive subjects. However, if hypertension is considered as a mechanical factor acting on the arterial wall with deleterious consequences, the totality of the blood pressure curve should be considered in order to investigate the risk. The purpose of this review is to show that in addition to systolic and diastolic blood pressures, other hemodynamic indexes with particular relevance for cardiac complications and that originate from pulsatile pressure should be taken into account, namely brachial pulse pressure, pulse pressure amplification, early wave reflections, and pulse wave velocity.

Clinical value of ambulatory blood pressure monitoring.

Ambulatory blood pressure monitoring (ABPM) has now become an established clinical tool. It is appropriate to take stock and assess the situation of this technique. UPDATE ON EQUIPMENT: Important improvements in equipment have occurred, with reductions in weight, in awkwardness and in noisiness of the machines, better acceptability and tolerance by the patients, and better reliability. Validation programmes have been proposed and should be referred to. Limitations of the technique persist with intermittent recording in current practice. The reproducibility is limited in the short-term while recording over 24 h is acceptable. DIAGNOSIS AND PROGNOSIS: White-coat effect (WCE) is manifested as a transient elevation in blood pressure during the medical visit The frequency of this phenomenon, the size of the effect, age, sex and level of blood pressure (BP) or the situation of occurrence (general practitioner, specialist or nurse) have been interpreted differently. It does not seem that WCE predicts cardiovascular morbidity or mortality. White-coat hypertension (WCH) is diagnosed on the evidence of abnormal clinical measures of BP and normal ABPM. The latest upper limits of normality by ABPM recommended by the JNCVI are < 135/85 mmHg while patients are awake and < 120/75 mmHg while patients are asleep. If we accept these upper limits of normality in ABPM, WCH does not appear to be a real problem as regards risk factors or end-organ effects. In terms of prognosis, data are limited. Cardiovascular morbidity seems low in WCH but identical to that of hypertensive subjects in these studies. However, further studies are needed to confirm these results. WCH does not appear to benefit from anti-hypertensive treatment. It is obvious that the lower the BP regarded as the limit of normality, the less likely the occurrence of secondary effects of metabolism, or end-organ effects or complications in those classified as hypertensive. 24 HOUR CYCLE: One of the most specific characteristics of ABPM is the possibility of being able to discover modification or alteration of the 24 h cycle of BP. Non-dippers are classically defined as those who show a reduction in BP of less than 10/5 mmHg or 10% between the day (06.00-22.00 h) and the night, or an elevation in BP. In contrast, extreme dippers are those in whom the BP reduction is greater than 20%. CARDIOVASCULAR SYSTEM: The data remain inconclusive with regard to the existence of a consistent relationship between the lack of a nocturnal dip in blood pressure and target organ damage. As regards prognosis, it seems that an inversion of the day-night cycle is of pejorative significance. CEREBROVASCULAR SYSTEM: Almost all studies have shown that non-dippers had a significantly higher frequency of stroke than dippers. In contrast, too great a fall in nocturnal BP may be responsible for more marked cerebral ischaemia. RENAL SYSTEM: Non-dippers have a significantly elevated median urinary excretion of albumin. There is a significant correlation between the systolic BP and nocturnal diastolic BP, and urinary excretion of albumin. Various studies have confirmed the increased frequency of change in the 24 h cycle in hypertensive subjects at the stage of renal failure. DIABETES: BP abnormalities should be considered as markers of an elevated risk in diabetic subjects but cannot be considered at present as predictive of the appearance of micro-albuminuria or other abnormalities. ABPM is thus of interest in type I or type II diabetes both in the initial assessment and in the follow-up and adaptation of treatment. PHARMACO-THERAPEUTIC USES: The introduction of ABPM has truly changed the means and possibilities of approach to the study of the effects of anti-hypertensive medications, with new possibilities of analysis such as trough-peak ratio smoothness index, etc.

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.

Association between high heart rate and high arterial rigidity in normotensive and hypertensive subjects.

BACKGROUND: The dynamic elastic modulus of central arteries is very frequency-dependent Although resting heart rate is a potent independent risk factor for morbidity and mortality both from cardiovascular and from noncardiovascular disease, no link between tachycardia and arterial stiffness has ever been established. OBJECTIVE: To relate arterial stiffness to heart rate in a population with relatively low cardiovascular risk. METHODS: Pulse-wave velocity measurements and high-resolution echo-tracking techniques were used to determine the degree of arterial distension (of carotid and femoral arteries, and terminal aorta) and the velocity of the pulse wave (aorta and upper and lower limbs) at the same time as heart rate, in members of a large population of normotensive and hypertensive subjects in a multicenter study in Paris, Fleury-Merogis and Grenoble (France). RESULTS: A high heart rate was strongly associated with reduced distension and elevated pulse-wave velocity, even after adjustment for age and blood pressure. A high aortic pulse-wave velocity was also negatively associated with a low baroreflex sensitivity. The most significant associations between high heart rate and high arterial rigidity were found for the carotid artery, the thoracic aorta, and the lower limbs, but there was no significant result for the terminal aorta and the arm arteries. CONCLUSION: This study demonstrates that there is a statistically significant positive link between high heart rate and high arterial stiffness measured at the site of central and lower limb arteries. Since an elevated heart rate has been shown to be associated with cardiovascular risk, such findings may be relevant for future cardiovascular studies in epidemiology.

Use of ambulatory blood pressure monitoring in the management of antihypertensive therapy.

The recent development of ambulatory blood pressure (ABP) monitoring techniques has improved recording of blood pressure in therapeutic trials and in the clinical setting. The application of ABP differs according to which of these 2 applications is being considered. In therapeutic trials, a placebo control is required. The large quantity of precise data acquired with ABP monitoring allows the study of a limited number of patients; it also allows individual study of patients with a 'white coat' response (i.e. elevated blood pressure in response to examination by the clinician). Analysis of data from ABP monitoring may include the following: comparison of mean blood pressure values over 24 hours, daytime or night-time, or over any other selected time period; 24-hour blood pressure profiles, or analysis hour-by-hour, giving true chronotherapy, and providing data regarding the wearing-off of a drug effect or loss of therapeutic control; analysis of blood pressure at particular times, such as on waking; or specific examination of nonresponders. In individual patients, ABP monitoring should be reserved for specific indications. It can be used before initiation of treatment to confirm the necessity for treatment, especially in the context of hypertension at rest or the 'white coat' effect. With established treatment, ABP monitoring can be used in patients with resistant hypertension, in severe hypertension to examine loss of blood pressure control over time or inversion of the day/night cycle, and in patients with a specific illness, e.g. diabetes, in order to obtain the lowest blood pressure readings possible. Examination of these factors assists clinicians to accurately decide upon the timing and frequency of antihypertensive therapy.

Effects of amlodipine on baroreflex and sympathetic nervous system activity in mild-to-moderate hypertension.

To investigate the effect of amlodipine on baroreflex sensitivity and sympathetic system activity, 36 patients with essential hypertension were randomized to once-daily, double-blind treatment with amlodipine 5 mg or placebo 5 mg for 60 days. Measurements with a Finapres device allowed calculation of baroreflex sensitivity and blood pressure (BP) variability. Adrenergic activity was assessed via measurements of lymphocyte beta2-adrenoceptors and plasma catecholamine concentrations. Compared with placebo, amlodipine significantly decreased BP, but did not significantly alter baroreflex sensitivity. Spectral analysis of Finapres data showed that, compared with placebo, amlodipine decreased the variability of systolic blood pressure, diastolic blood pressure, and RR interval in the low frequency band. There were no simultaneous changes in adrenergic function, however, suggesting that these effects of amlodipine were not mediated via sympathetic nervous system activation.

Cardiac and vascular remodelling: effect of antihypertensive agents.

The 1996 World Health Organization (WHO) recommendations for mild hypertension stressed the need to evaluate target-organ lesions as treatment criteria. The effects of both vascular and heart remodelling on hypertension must to be taken into account, as they adversely influence the prognosis of patients with hypertension. It was previously demonstrated that at least three classes of antihypertensive agents were able to decrease morbidity and mortality in patients with hypertension. Meta-analyses have shown that angiotensin-converting enzyme inhibitors seem to have a marked effect on regression of left ventricular hypertrophy (LVH). However, the relationship between drug-induced LVH regression and reduced morbidity and mortality remains to be confirmed. The effect of antihypertensive agents on vascular hypertrophy, as assessed by intima-media thickness, and their involvement in reducing morbid events, also have to be determined at the vascular level. As experimental data have highlighted the involvement of angiotensin II in animal models of LVH and vascular hypertrophy development, the role of angiotensin II AT1 receptor blockers should also be assessed in this indication.

Relationship between short-term and long-term blood pressure variabilities in essential hypertensives.

This study was designed to analyse the relationship between the different blood pressure (BP) variabilities obtained in a non-invasive way and to determine the potential contribution of aging, severity of hypertension and increased ventricular mass to these different BP variabilities. Two hundred and six hypertensive patients underwent a 24-h ambulatory BP measurement (ABPM) as well as a photoplethysmographic BP recording and a standard echocardiography. Nocturnal BP fall and standard deviations of hourly mean BP levels as well as post-prandial fall in BP were calculated from the 24-h ABPM and were considered as indexes of long-term variability. Baroreflex sensitivity (BRS) and spectral powers of systolic BP, diastolic BP and heart rate (HR) over the low frequency band (LF: 0.05--0.14 Hz) were obtained from photoplethysmographic recording and were used as indexes of short-term variability. Short-term variability indexes were shown to be significantly related to those of long-term variability. A decrease in LF spectral powers was associated with a particular profile characterised by an attenuation of nocturnal BP fall, an increase of daytime BP standard deviations, an increase in post-prandial BP fall, a decrease in BRS and to a lesser extent, a diminution in night-time HR standard deviation. Moreover, a negative significant relationship was found between standard deviation of daytime systolic BP and both night systolic BP fall and BRS. Age and nocturnal BP level were associated with all BP variability disorders, whereas left ventricular hypertrophy was associated only with a decrease in LF spectral powers and in night BP fall, and an increase in standard deviation of daytime BP. Finally, LF spectral power of SBP was identified as independently predicted by age and night SBP fall. Journal of Human Hypertension (2001) 15, 41-48

Relationships between cardiovascular remodelling and the pulse pressure in never treated hypertension.

The role of pulse pressure (PP) in cardiovascular remodelling was studied in 61 never treated hypertensive subjects who were selected on the criteria of ambulatory blood pressure (BP) monitoring (mean BP over 24 h: 147 +/- 14/96 +/- 10 mm Hg). Echocardiography and carotid ultrasonography were performed and the vascular images analysed using a specific automatic measuring program. Thirty percent of subjects had left ventricular hypertrophy (LVH). Left ventricular mass index (LVMI) was related to the clinic (r = 0.35) and ambulatory (r = 0.41 over 24 h, r = 0.38 daytime and r = 0.42 night-time) PP and to the systolic BP. PP was higher when there was LVH. Vascular thickening was found in 6.6% of subjects (carotid intima-media thickness (IMT) >/=1.0 mm). Among the BP parameters, IMT and cross-sectional area (CSA) were related only to the clinic PP (r = 0.27, r = 0.29 respectively) and to the ambulatory PP (over 24 h: r= 0.29, r = 0.28; daytime: r = 0.22, r = 0.23; night-time: r = 0.32, r = 0.30). In men, the relationship between CSA and PP (clinic and over 24 h) was independent of age. A total of 16.7% of subjects with LVH had intima-media thickening in contrast to 2.3% in the group without LVH. LVMI was related to the CSA (r = 0.37) and to the IMT (r = 0.31). However, after multivariate analysis taking into account the PP, relationships between IMT or CSA and LVMI disappeared. Our data showed that the PP was the most important BP parameter in the development of cardiac and arterial remodelling in hypertension. Journal of Human Hypertension (2000) 14, 23-30.

Circadian changes of left ventricular ejection fraction in normal subjects.

Sleep has a specific physiology with related cardiovascular changes. We have previously found in respiratory patients [chronic obstructive pulmonary disease (COPD) and sleep apnea syndrome (OSAS)] an unexpected decrease in left ventricular ejection fraction (LVEF) at waking in the morning when compared with the rest period during the day. Whether this observation was linked to the consequences of the respiratory abnormalities or reflected physiological fluctuations related to the changes in autonomic nervous system tone remained unknown. Thus, we have set out to analyze the changes in LVEF with sleep in normal individuals. Eight healthy young men had LVEF measured before and after submaximal exercise, at rest before bedtime, and on waking in the morning. Technetium-99m with in vivo red cell labelling was used. Sleep parameters were assessed using classical polysomnography. In order to detect any influence of autonomic nervous system stimulation on LVEF, sympathovagal tone (SVT) was also assessed during night-time LVEF measurements using spectral analysis of RR intervals. LVEF at rest was within the normal limits for all the subjects (range 51-62%). On submaximal exercise, the LVEF increased in four subjects, was unchanged in two, and decreased in two. The main result concerns the changes in LVEF overnight. In the morning, LVEF decreased dramatically in three subjects and reached a level of < 30% in four. These decreases in LVEF were not related to changes in SVT or sleep structure. LVEF values returned to normal in 30 min. The LVEF changes during exercise are in accordance with previous data in the literature. The dramatic decrease in LVEF observed in the morning could be related either to vascular resistance changes or to nocturnal variations in cardiac contractility, which both need further studies to be established.

Use of ambulatory blood pressure monitoring data to predict left ventricular mass in hypertension.

BACKGROUND: Many studies have shown definite but weak correlations between 24h blood pressure and left ventricular mass in hypertension. OBJECTIVE: The present study applied an original multivariate analysis of parameters from ambulatory blood pressure monitoring to predict left ventricular mass in hypertension. METHODS: Two hundred untreated hypertensive subjects (age=51+/-13 years, clinic blood pressure=163/98mmHg) had echocardiography and 24h recording of blood pressure. Data from 102 subjects were used to construct a mathematical model for prediction of left ventricular mass. The remaining 98 subjects were used to validate the model. RESULTS: The model included age, weight, height, 24h systolic blood pressure, heart rate over 24h, standard deviations of systolic blood pressure and of heart rate over 24h. Using this model, we explained 63% of the variance of left ventricular mass. Moreover, the model was validated for the correlation (r=0.70) between measured and the estimated left ventricular mass. CONCLUSIONS: Systolic blood pressure, heart rate and their standard deviations over 24h contribute to left ventricular mass in hypertensive subjects. Thus, it is important to take into account not only blood pressure but also heart rate in clinical studies.

Left ventricular hypertrophy and arterial hypertrophy.

In the most recent WHO recommendations of 1996 it was reiterated that the classification of HT still remains based on the actual BP figures but also on the importance of target organ lesions. Thus the study of cardiac and vascular function and in particular the presence of hypertrophy or remodeling is of importance. A limited number of studies have examined the prevalence, the association and the correlation between modifications and remodeling in the heart and in the vasculature. It is important to distinguish compliance vessels such as the carotid from resistance vessels such as the radial. For compliance vessels the prevalence of cardiac and vascular hypertrophy are nearly identical being around 5% for normotensive subjects and around 12% for hypertensive subjects. This prevalence of thickening in the intima-media is more evident in subjects with left ventricular hypertrophy (LVH). The left ventricular geometric pattern is also an element to take into account. The presence of concentric remodeling of the left ventricle without LVH has already been associated with an increase in intima-media thickness (IMT). When there is an LVH this IMT is similar in severity to the LVH and in particular concentric. For resistance vessels such as the radial artery the number of studies is limited but a significant correlation between left ventricular mean wall thickness and common carotid artery distensibility and compliance has been found. There is also a significant correlation between the radial median lumen ratio and the relative wall thickness but this correlation disappears when age and systolic BP are taken into account. Thus for this type of vessel it is too early to conclude the elements contributing to structural changes. The determinant factors for these structural changes in the heart and the carotid arteries associated with hypertension are certainly multiple be they haemodynamic, hormonal or genetic. The observation establishing an association between anomalies at cardiac and vascular level may have undoubted diagnostic, prognostic and therapeutic implications which are all intimately related and which require refinement and confirmation.

Toward a portable blood pressure recorder device equipped with an accelerometer.

The 24-h ambulatory systolic blood pressure (ASBP) recording has become a helpful tool in the diagnosis of hypertension and evaluation of the efficiency of anti-hypertensive drugs. Yet, the very high variability of ASBP makes the analysis of the recording rather difficult. A potential solution to reduce ASBP variability has been studied and is presented in this article. It consists of equipping the portable ASBP recorder device with other sensors, a three axes accelerometer and a heart rate recorder, so as to enable an analysis to be undertaken of the arterial pressure profile in the light of these concomitant data. A database has been collected, and a model linking ASBP variations with body acceleration and heart rate measurements is developed. Its performance is tested in prediction and the results compared with those obtained from one of the solutions currently used by physicians to deal with ASBP variability. The results obtained with 16 young subjects from the database, for whom two 24-h recordings are available, are significantly improved and very encouraging.

Study of arterial blood pressure by a Windkessel-type model: influence of arterial functional properties.

OBJECTIVE: To analyse the performance of a Windkessel blood pressure (BP) modeling of arterial compliance adjusted in a dynamic fashion according to a non-linear relationship between the arterial compliance (AC) and BP. Non invasive measurements of the radial BP waveform (MILLAR tonometry) were compared to those constructed by an electric simulator reproducing the model in a symmetrical network subdivided into 121 segments. We introduced at cardiac level the aortic stroke volume (Doppler echocardiography) and the dynamic values of compliance (relation of compliance-to pressure, constant or variable) whether the model was linear or non linear, measured by high resolution Doppler (NIUS 02) for each subject. RESULTS: At the radial artery segment the modelled BP obtained by the non linear model of AC was not significantly different from the measured BP wave, while in the linear model (AC constant at mean BP level) the systolic BP was significantly underestimated. (*P < 0.05). CONCLUSION: This work shows the limits inherent in simplification of arterial compliance in the Windkessel model using constant parameters. This demonstrates the influence of the dynamic properties of the arterial wall in a conduction artery on the level of systolic and diastolic BP.

[Short-term variability of blood pressure]. / Variabilité à court terme de la pression artérielle.

The regulation of blood pressure (BP) is traditionally described in terms of homeostasis, and indicates that BP although being continuously perturbed by external stimulations always displays the tendency to come back toward a reference set point. Experimental and clinical studies indicate that these fluctuations occurring around the average present a source of complementary information on the mechanism of cardiovascular control. Recently a wide variety of algorithm and models have been proposed to study the cardiovascular system through new technics of continuous non invasive BP or heart rate (HR) measurements. They give new insites for the evaluation of hypertensive patients and relevance to the understanding of the role of the disorder of the tonic regulation of BP, rather than its short-term variability or reactivity. However, if available data unequivocally indicate that the analysis of variability is a useful tool, the interpretation of those data in clinical trials is not always optimal because there is lot of interaction between BP, HR and other biological signals, and furthermore the use of laboratory data introduces problems to predict what happens on daily life ambulatory conditions.

[Reproducibility of echocardiographic parameters by automatic detection of contours in hypertensive patients]. / Reproductibilité des paramètres enregistrés en échographie cardiaque par la détection automatique de contours chez l'hypertendu.

The reproducibility of automatic outline detection is a echocardiographic reproducibility which has been poorly evaluated in patients with cardiomyopathy. Two independent observers identified the systolic surface and mid and end diastolic surfaces of 27 hypertensive patients, who had been referred to the laboratory for the measurement of left ventricular mass. Each observer examined on two occasions all parameters and all parameters were measured at least 2 hours apart. The coefficient of variation (CV) expresses the reproducibility of each measurement. The intra observer was 10 to 15% and the inter observer 15 to 22% for the measurement of surface area. The coefficient of variation is regularly greater than 20% for measures of maximum speed, which characterise surface changes in diastole. The automatic detection of contours is a echocardiographic tool whose potential is great for evaluating left ventricular function but the current versions can only be applied to very selective group of patients depending on the quality of their echographic window for acoustic quantitation. This technique is very operator dependent, in particular as regards setting the gains and this explains its poor reproducibility and its limited interest in daily clinical practice.

[Reproducibility and development of pulse wave velocity at rest and during exertion]. / Etude de la reproductibilité et de l'évolution de la vitesse de propagation de l'onde de pouls au repos et à l'effort.

PURPOSE: to search in which situation the PWV is the most reproducible. METHODOLOGY: PWV is measured with a continuous doppler technique along the subclavial radial arterial segment on the right forearm. 30 normotensive subjects (20-30 years) are studied twice running at 24-hour interval at rest and during stress (ergometric bicycle, stress levels: 50, 75, 100 watts/mn). STATISTICS: Student test and correlation when the data are normally distributed. RESULTS: mean PWV increases progressively with blood pressure during stress. REST: 10.0, 50W: 11.3, 75W: 12.33, 100W: 13.32, 4 mn rest: 10.6. Mean differences (MD) with standard deviations (SD) and correlation (COR) are as following: (Table: see text). If we take into consideration MD, SD and COR between the 2 stress tests, 75W level appears to be the most reproducible. CONCLUSION: these data must be taken into account when using PWV to appreciate the vascular effect of some medications especially in hypertension.