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.

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.

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

Carotid remodeling in essential hypertension: role of blood pressure, indexed parameters, and association with cardiac mass and aortic stiffness.

The role of blood pressure on carotid remodeling, using no indexed and indexed parameters, was studied in essential hypertension. Carotid parameters were also compared to cardiac mass and aortic stiffness. Forty untreated hypertensive men had echocardiography, carotid ultrasonography and carotidfemoral pulse wave velocity measurements. Cross-sectional area index was associated essentially with the 24-hour systolic blood pressure whereas intima-media thickness was related especially to the 24-hour pulse pressure. Carotid intima-media thickness and cross-sectional area indexes were less related to blood pressure variables than non-indexed parameters. There is an independent association between 24-hour pulse pressure and left ventricular mass index and pulse wave velocity. To conclude, blood pressure, particularly pulse pressure, is associated with vascular and cardiac alterations. The indexation by the body surface area do not provide any additional information in the association between carotid and blood pressure parameters.

[Measurement of carotid artery intima-media thickness. Analysis and reproducibility]. / Mesure de l'épaisseur intima-média carotidienne. Analyse de la reproductibilité.

The intima-media thickness of the carotid artery is a cardiovascular risk factor, especially in hypertensive, diabetic or dyslipidemic patients. Very accurate tools of measurement are essential in order to optimise the analysis of the severity of the vascular lesions. Present methods use computer programmes for ultrasonic image enhancement and have already been shown to be very reproducible. However, there is still room for improvement in the detection of lesions at their initial stage of development and in the follow-up of their progression with or without antihypertensive or lipid lowering drugs.

[Heart malformations and vascular complications associated with Turner's syndrome. Prospective study of 26 patients]. / Malformations cardiaques et complications vasculaires associées au syndrome de Turner. Etude prospective chez 26 patientes.

Turner's syndrome is associated with congenital heart disease in a third of cases. Several reports of aortic dilatation and of death by dissection or rupture of the aorta have been published. The authors undertook a prospective study to assess the incidence of cardiac malformations and aortic dilatation in genetically confirmed Turner's syndrome. Twenty-six out of 34 patients recalled (76%), aged 7 to 30 years (average 17 +/- 6 years) accepted their inclusion in this study and underwent clinical examination, ECG, chest X-ray and echocardiography. Thirteen patients had a monosomy 45X and 13 a mosaic or structural abnormality. Six had a history of cardiovascular disease (operated coarctation: 2 cases, kinking: 2 cases, Hypertension: 2 cases). Eight patients (30%) had one or several anatomical cardiovascular abnormalities: bicuspid aortic valve (19.2%), abnormalities of the aortic isthmus (kinking or coarctation) (15.4%), aortic regurgitation (7.7%), mitral stenosis (3.8%), partial anomalous venous drainage (3.8%), patent ductus arteriosus (3.8%) and left superior vena cava (11.5%). Systematic evaluation of the aorta resulted in the diagnosis of dilatation of the ascending aorta in 1 case and dilatation of the sinus of Valsalva in 2 other cases. The authors conclude that echocardiographic evaluation is essential after the diagnosis of Turner's syndrome. It should be repeated regularly to detect dilatation of the aorta which carries the risk of serious complications, such as rupture or dissection of the aorta.

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.

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.

[Evaluation of the activity of the autonomic nervous system in "dipper" and "non dipper" essential hypertensives. Gender differences]. / Evaluation de l'activité du système nerveux autonome chez l'hypertendu essentiel dipper et non dipper. Recherche d'une influence du sexe.

OBJECTIVES: 1) To compare the autonomic nervous system activity parameters obtained from a photoplethysmographic recording in dipper and non dipper hypertensive. 2) To look for an interaction between dipper/non dipper status and gender. METHODS: Prospective study involving 245 untreated hypertensives (51 +/- 13 years, 146 men, 99 women). All of the patients underwent a 24-hour ambulatory blood pressure measurement (ABPM) as well as an echocardiography for left ventricular mass index determination (LVMI) and a photoplethysmographic recording of blood pressure (BP). Nondippers were defined as those whose nocturnal decrease in systolic BP (SBP) and/or diastolic BP (DBP) was < 10% of daytime BP. Spectral powers were obtained from the photoplethysmographic recording using a fast Fourier transform over the low frequency band (LF) and the high frequency band (HF). Baroreflex sensitivity (BRS) was evaluated by the sequences method. RESULTS: Of the 245 patients, 159 were dippers (98 men, 61 women) and 86 were non dippers (48 men and 38 women). Clinic BP was significantly higher in non dippers than in dippers (168/101 vs 161/98 mmHg; p < 0.01 for SBP and p < 0.05 for DBP) whereas daytime ABPM and LVMI were not different, whatever the gender. LF spectral powers were significantly lower in non dippers than in dippers for SBP (respectively 25 +/- 11% vs 30 +/- 13%; p < 0.01) for DBP (respectively 35 +/- 14% vs 41 +/- 15%; p < 0.01) and for HR (respectively 34 +/- 15% vs 38 +/- 15%; p = 0.03). They showed a positive correlation with the nocturnal SBP fall (r = 0.21, p < 0.001 for SBP and DBP spectral powers, r = 0.19; p < 0.005 for HR spectral power) and with the nocturnal DBP fall, too (r = 0.19; p < 0.005 for SBP spectral power, r = 0.20; p < 0.002 for DBP spectral power, r = 0.19; p < 0.005 for HR spectral power). HF spectral powers tended to be higher in non dippers than in dippers but in a non significative way. BRS was roughly the same in dippers and non dippers (7.5 +/- 2.7 vs 7.0 +/- 3.1 ms/mmHg, NS). The interaction between non dipper/dipper status and sex was non significant whatever the LF spectral power. CONCLUSIONS: 1) The greater the nocturnal BP fall, the higher the sympathetic activity indexes. 2) This relationship was found both in males and females.

[Evaluation of the ambulatory blood pressure monitor SAVE 33 model 2]. / Evaluation du moniteur de pression artérielle en ambulatoire save 33 modèle 2.

UNLABELLED: This work tests a new ambulatory blood pressure device: Save 33 II. The evaluation is conducted according to the phases II and IV of the British Hypertension Society (BHS) protocol: the phases I and III (before and after use) are not performed as this device has received the European quality label 'CE' that guarantees a +/- 3 mmHg accuracy before and after 10,000 simulated cycles. Two trained observers (hearing test and certification done according to the BHS recommendations) have performed 7 sequential BP measurements with conventional and automatic method, at the same arm, among 85 patients. The ranges of mean blood pressure are 78-203 mmHg, for SBP and 53-130 mmHg for DBP. RESULTS: The Save 33 II monitor satisfies the grade B of BHS evaluation for both systolic and diastolic pressures. This device also satisfies the Association for the Advancement of Medical Instrumentation (AAMI) protocol: mean difference between methods and standard deviation less than 5 +/- 8 mmHg: -2.7 +/- 6.8 mmHg for SBP and -0.86 +/- 6.6 mmHg for DBP. The in-use assessment is conform to BHS criteria for 20 recordings (less than 20% invalid values during day and night); the 5 other recordings have not enough night values, due to batteries failure (2 cases), sleeping discomfort (2 cases) and a cuff withdraw. CONCLUSION: This device, in the tested configuration, agrees the B grade of BHS and can be recommended for ambulatory blood pressure measurement.

[Kinetics of circadian variations in ambulatory arterial blood pressure and cardiovascular sequelae]. / Cinétique des variations nycthémérales de la pression artérielle en ambulatoire et retentissement cardiovasculaire.

OBJECTIVE: To study the relationships between evolution of changes in blood pressure (BP) over the 24 hour cycle and their cardiac and vascular consequences in mild to moderate hypertensive (HT) subjects (WHO criteria). MATERIAL AND METHODS: 151 patients presenting with mild to moderate essential HT (Age 49 +/- 12 yrs, 63 M 44W)--ambulatory measurement of BP over 24 hours (Spacelabs 90207) automatic determination of the diurnal cycle by Fourier analysis (5 harmonics) and calculation of the slope of BP variation (mmHg/hr) at the point of transition from day to night (nocturnal dip slope (NDS)), and at the change from night to day (morning rise slope (MRS). Patients with inversion of the day-night cycle were excluded, day-night being arbitrarily defined as 7 to 22 h and 22 to 7 h. Echography of left ventricular mass index (LVMI)/Penn convention, formula of Devereux, and carotido-femoral distensibility by pulse wave velocity (PWV, Complior Colson France). RESULTS: Ambulatory measures of BP and HR and of cardiovascular parameters were as follows. [table: see text] The slope of nocturnal fall (NDS) and morning rise in SBP (MRS) is significantly correlated with LVMI (NDP r = -0.02, p = 0.049, MPP r = 0.21, p = 0.029) and with PWV (MPP: r = 0.32, p = 0.005). No relationship was found with the DBP values. By multivariate analysis taking into account age, sex, 24 h SBP, MPP slope velocity was the only variable which was significantly related with the model of PWV and LVMI (p < 0.001). CONCLUSION: Dipper and non-dipper studies have been performed to examine the consequences of day night variations in BP. The evolution of diurnal changes in BP seems to have an effect on the vessels and heart and may be a simple analysis tool for assessing prognosis and therapeutic effects.

High prevalence and persistence of sleep apnoea in patients referred for acute left ventricular failure and medically treated over 2 months.

AIMS: Cardiac failure patients were studied systematically using polysomnography 1 month after recovering from acute pulmonary oedema, and again after 2 months of optimal medical treatment for cardiac failure. METHODS AND RESULTS: This prospective study of consecutive patients was conducted in a cardiac care unit of a university hospital. V o(2)measurements and left ventricular ejection fraction were recorded. Thirty-four patients, initially recruited with pulmonary oedema, improved after 1 month of medical treatment to NYHA II or III. They were aged less than 75 years and had a left ventricular ejection fraction less than 45% at the time of inclusion. Age was 62 (9) years, body mass index= 27 (5) kg x m(-2)and an ejection fraction= 30 (10)%. Eighteen of the 34 patients (53%) had coronary artery disease. Twenty-eight of the 34 had sleep apnoea syndrome with an apnoea+hypopnoea index >15 x h(-1)of sleep. Thus, the prevalence of sleep apnoea in this population was 82%. Twenty-one of 28 (75%) patients had central sleep apnoea and seven of 28 (25%) had obstructive sleep apnoea. Patients with central sleep apnoea had a lower Pa co(2)than those with obstructive sleep apnoea (33 (5) vs 37 (5) mmHg, P<0.005). Significant correlations were found between apnoea+hypopnoea index and peak exercise oxygen consumption (r= -0.73, P<0.01), and apnoea+hypopnoea index and Pa co(2)(r= -0.42, P = 0.03). When only central sleep apnoea patients were considered, a correlation between apnoea+hypopnoea index and left ventricular ejection fraction was also demonstrated (r= -0.46, P<0.04). After 2 months of optimal medical treatment only two patients (both with central sleep apnoea) showed improvement (apnoea+hypopnoea index <15 x h(-1)). CONCLUSIONS: We have demonstrated a high prevalence of sleep apnoea, which persisted after 2 months of medical treatment, in patients referred for acute left ventricular failure. Central sleep apnoea can be considered a marker of the severity of congestive heart failure.

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.

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.

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.

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.

[Heart rate and sympathetic risk]. / Fréquence cardiaque et risque sympathique.

A number of retrospective epidemiological and clinical arguments described in this article demonstrate that elevated heart rate (HR) is a predictive factor of cardiovascular risk due to activation of the sympathetic system which increases blood pressure and increases the risk of atherosclerosis and its complications. However, no epidemiological study has prospectively studied HR as the primary endpoint.

[Measurement of heart rate]. / Mesure de la fréquence cardiaque.

Like all laboratory parameters, measurement of heart rate must comply with certain theoretical conditions. In practice, it results from a compromises between the defined objectives, the material and the conditions of measurement. Effort are made to reproduce baseline conditions. The questions of the duration of measurement, it reproductibility, expression of the results, and the methods themselves are discussed. Standardization is required.

[Factors of variation of heart rate]. / Les facteurs de variation de la fréquence cardiaque.

Heart rate (HR), which participates in the short-term control of blood pressure and blood flow, depends on an intrinsic system and an extrinsic system via which the central nervous system processus and regulates the afferent stimuli of baroceptors and chemoreceptors. The situations responsible for short-term variations of HR include effort, the "white coat" effect, circadian rhythm, age, gender. The long-term maintenance of the HR level is dependent on nervous mechanisms, and haemodynamic and energetic conditions.

[Models of arterial pressure using a Windkessel type model: role of the functional arterial properties]. / Modélisation de la pression artérielle par un modèle de type Windkessel. Influence des propriétés fonctionnelles artérielles.

UNLABELLED: The Windkessel model is a linear model which does not take into account the structural and functional variations of the arteries related to the pulsatility of the blood pressure (BP) and its variations between systole and diastole. OBJECTIVE: To analyse the performance of a BP modelisation where the parameters of AC are adjusted in a dynamic fashion according to a curvilinear relationship of the arterial properties (compliance) in relationship to the BP between systole and diastole. DESIGN AND METHODS: 9 control subjects (age 25 +/- 3). The non invasive measures of the radial BP waveform (Millar tonometry) was compared to that constructed by an electric simulator reproducing the model in a sysmetrical network subdivised into 121 segments where we introduced for each subject: at cardiac level, the aortic stroke volume (Doppler echocardiography), and at the radial level, the dynamic values of compliance and diameter according to an arc-tangent model (measured by arterial echography NiUS02). RESULTS: The BP obtained by the adjusted model, where the AC parameter follows the curvilinear, relationship dV/dP measured experimentally, was not significantly different from the experimental, while in the constant model (AC at mean BP level) the systolic BP was different. CONCLUSION: This work shows in an experimental way the limits inherent in simplification in the Windkessel modelisation of the vascular system with constant parameters. It shows in a conduction artery the influence of the functional properties of the arterial wall on the level of systolic and diastolic BP.