Biomedical subjects

R Asmar

Publications and source records attributed to R Asmar.

At least 91 records · Page 5Linked to original sources

PubMed1994

Heterogeneity of the arterial tree in essential hypertension: a noninvasive study of the terminal aorta and the common carotid artery.

The diameter and the stiffness of the distal portion of the abdominal aorta and of the common carotid artery were evaluated noninvasively in 72 subjects with mild to moderate hypertension by comparing 39 normotensive controls of same age and sex distribution. For each arterial segment, pulsatile changes of diameter were determined by a newly described echotracking technique and pulse pressure was evaluated by applanation tonometry and oscillometric methods. In both territories, distensibility of hypertensive subjects was significantly reduced but compliance was reduced only at the aortic level. Diastolic diameter was increased at the carotid but not at the aortic site. Multiple regression analysis indicated that whereas compliance and distensibility were strongly influenced by BP in the terminal aorta, age was the predominant factor influencing carotid arterial stiffness. Following 30 days of converting enzyme inhibition, the decrease of BP was associated with a normalisation of aortic compliance and distensibility whereas no change was observed at the site of the carotid artery. The study provides evidence that the response of the arteries to the changes of BP differ in the various parts of the arterial tree. This factor may influence the drug effect produced by chronic converting enzyme inhibition.

Adult↗

PubMed1994

Sodium, large arteries, and diuretic compounds in hypertension.

Clinical and experimental data have shown that antihypertensive drugs do not cause the same change in arterial compliance for an equipotent blood pressure reduction. However, there is not clear data on the effect of sodium and diuretics on the visco-elastic properties of the hypertensive arterial wall. Cross-sectional epidemiologic studies suggest that, at any given value of age and blood pressure, pulse wave velocity is lower in the presence of decreased sodium intake. Longitudinal studies indicate that, in hypertensive subjects, low sodium intake is associated with a larger brachial artery diameter than is high sodium intake. In hypertension in the elderly and in severe hypertension with end-stage renal disease, sodium overload causes a reduction in arterial compliance and distensibility unrelated to blood pressure changes. In animal studies, the diuretic compounds cycletanine and indapamide were shown to increase systemic and carotid compliance independently of blood pressure changes. In contrast, a crossover study of hypertensive subjects showed that the diuretic agent hydrochlorothiazide did not change arterial compliance and pulse wave velocity, whereas the calcium entry blocker, felodipine, improved these parameters. Nevertheless, indapamide decreased the pulse pressure on stroke volume ratio, a parameter used as a marker of aortic distensibility. Taken together, such studies indicate that sodium may act on the arterial wall independently of blood pressure changes. The contribution of counter regulatory mechanisms, possibly related to the renin-angiotensin and sympathetic nervous systems, might explain the differences between the clinical and experimental changes observed with diuretic compounds. Of the various antihypertensive agents, diuretics seem to have the least effect on the arterial system.

Animals↗

PubMed1993

[Regional arterial hemodynamics and carotid circulation in essential arterial hypertension. Effect of nitrendipine in patients over 40 years of age].

Lesions of the arterial wall constitute one of the main complications of essential hypertension. The final objective of all antihypertensive drugs is to reduce the cardiovascular morbidity and mortality rates, but their short and medium term objectives must be to normalise blood pressure values and to correct the functional and structural abnormalities consecutive to arterial hypertension. In this double-blind drug versus placebo study conducted in 20 patients (14 men, 6 women) aged over 40, the effects of nitrendipine on regional arterial haemodynamics (aortic territory, upper limb, lower limb) and carotid circulation were evaluated. Nitrendipine was administered daily in doses of 20 mg during 1 month. After 4 weeks of treatment, the treated group showed a fall in blood pressure and an improvement in the pulse wave propagation (an index of arterial distensibility) in the carotido-femoral territory (11.4 +/- 1.7 vs 9.9 +/- 1.6 m/s; P < 0.01) and in the humero-radial territory (12.9 +/- 2.0 vs 11.6 +/- 2.1 m/s; P < 0.05); there was no change in the femoro-tibial territory (13.2 +/- 1.8 vs 12.5 +/- 1.7 m/s; NS). The haemodynamics of the common carotid artery showed no change in carotid diameter or blood velocity, and small lowering of local resistances (28.1 +/- 9.1 vs 24.6 +/- 4.9 mmHg.s.ml-1; P < 0.05). This study demonstrates that in patients older than 40 years a long-term treatment with nitrendipine lowers blood pressure, does not alter the common carotid flow and improves arterial distensibility. The arterial effects seem to vary according to the arterial territories considered.

Adult↗

PubMed1993

Ultrastructural connectivity of [leu]5-enkephalin-immunoreactive synapses in the guinea-pig stellate ganglion: involvement of spines and triads.

The ultrastructure of [leu]5-enkephalin-immunoreactive (ENK-IR) nerve fibres in the guinea-pig stellate ganglion was studied by means of pre-embedding immunohistochemistry. ENK-immunoreactivity was primarily contained within large dense core vesicles (91 +/- 21 nm in diameter; n = 259) but was absent from small clear vesicles (47 +/- 9 nm; n = 488) within the same nerve terminal that were concentrated at presynaptic regions. Thus, fast synaptic transmission mediated by ENK-IR terminals most probably does not involve [leu]5-enkephalin which may be released parasynaptically. Evaluating a total number of 123 synapses involving an ENK-IR presynaptic nerve ending, 47% terminated upon a spine, 46% upon a dendritic shaft, and 7% directly addressed a soma of a postganglionic neuron. In 30% of axo-dendritic synapses and 33% of axo-somatic synapses, non-immunoreactive dendrites or somata being postsynaptic to an ENK-IR terminal were in direct but non-synaptic contact to another dendrite/soma. Such arrangements are termed "triads". In view of the current hypotheses concerning the function of spines and triads, these findings indicate that ENK-IR terminals within the guinea-pig stellate ganglion may be involved in the generation of long-lasting synaptic events and modulation of non-synaptic intraganglionic communication.

Animals↗

PubMed1993

[Non-invasive ambulatory measurement of arterial pressure. Recommendations of the measurement group of the French Society of Arterial Hypertension].

Ambulatory blood pressure monitoring is being widely used now that relatively simple, reliable and well-tolerated, non-invasive blood pressure measuring devices have become available. The following recommendations are only to help physicians to use this technique in their daily practice: only use homologated devices; ambulatory monitoring should be performed during normal, everyday activities; at least one measurement of blood pressure should be taken every 1/4 hour during the day time (7 h-22 h) and every 1/2 hour during the night (22 h-7 h); the arm must be absolutely still and relaxed during the measurement; the function of the measuring device should be checked when the patient is fitted up and when the device is removed; data processing should provide at least: all values of blood pressure and heart rate, and their times of measurement, the mean values of systolic end diastolic blood pressure and heart rate during the day and during the night, the maximal and minimal systolic and diastolic blood pressure values, a chronogramme of the values. Reasonable indications of ambulatory blood pressure monitoring include: elimination of the "white coat" effect: to confirm the diagnosis of borderline hypertension; to demonstrate inversion of diurnal rhythm in severe hypertension; to demonstrate episodic hyper or hypotension; to confirm certain cases of toxaemia of pregnancy. It is also justified in the evaluation of antihypertension therapy, especially in cases of suspected drug resistance.

Ambulatory Care↗

PubMed1992

Arterial and antihypertensive effects of nitrendipine: a double-blind comparison versus placebo.

Arterial effects evaluated by carotid-femoral, brachial-radial, and femoral-tibial pulse wave velocity and antihypertensive effect evaluated by 24-h ambulatory blood pressure (BP) monitoring were measured in 17 hypertensive patients before and 24 h after once-daily nitrendipine (20 mg) administration. After a 15-day placebo period, a double-blind study of nitrendipine versus placebo was performed for 1 month. After nitrendipine dosing, BP measured by sphygmomanometer 24 h after the last drug intake showed a significant decrease as compared with the pretreatment period. Ambulatory BP mean values were also significantly decreased for systolic and diastolic BP (SBP, DBP). This decrease predominated during the day but was observed nocturnally only after 6 a.m. Twenty-four hours after the last tablet intake of nitrendipine, carotid-femoral and brachial-radial pulse wave velocities were significantly reduced, whereas femoral-tibial wave velocity was unchanged, indicating that markers of arterial rigidity might be substantially modified and that the modifications were partly unrelated to BP changes. The results provide evidence that in hypertensive subjects nitrendipine 20 mg given once daily for 1 month produces an arterial effect for 24 h, in association with BP reduction.

Adult↗

PubMed1992

[Comparative effects of angiotensin converting enzyme inhibitors and calcium inhibitors related to baseline ambulatory blood pressure. A French multicenter study].

OBJECTIVE: This multicenter study was aimed at determining whether the baseline ambulatory blood pressure (BP) level does influence the efficacy of angiotensin-converting enzyme inhibitors (CEI) and that of calcium antagonists (CA) to the same degree. METHODS: The BP recordings of 236 patients with mild to moderate hypertension were reviewed: these subjects previously entered clinical trials comprising a mean 2-week placebo period and a mean 6-week active treatment phase (CEI = 115, CA = 121). The 24-hour baseline ambulatory BP was considered as high when greater than 139/87 mmHg, according to Staessen's meta-analysis. RESULTS: In the patients with an high baseline ambulatory BP, CEI and CA have had roughly a similar effect (reduction in systolic = 9.5 +/- 7.8% vs 7.7 +/- 6.3%, NS; reduction in diastolic = 9.8 +/- 8.6% vs 8.3 +/- 5.8%, NS). Conversely, the patients with a baseline ambulatory BP level lower than or equal to 139/87 mmHg experienced a greater reduction in ambulatory BP with CEI than with CA (systolic = 7.9 +/- 7.0% vs 0.6 +/- 6.7%, p = 0.0001; diastolic: 5.0 +/- 7.4% vs 1.9 +/- 7.6%, p = 0.040). Finally, further analysis found the threshold of drug efficacy to be 120/80 and 135/85 mmHg in CEI and CA patients respectively. CONCLUSIONS: 1) CEI are more effective than CA in patients with a low ambulatory BP only. 2) The risk of a visceral hypoperfusion seems however to be limited, since CEI do not reduce diastolic ambulatory BP further, when its baseline level is lower than 80 mmHg.

Adult↗

PubMed1991

[Validation of Oscillomat, a device for self-measurement of blood pressure. Comparison with mercury sphygmomanometers].

Self-measurement of arterial blood pressure (BP) is a valuable aid in the follow-up of hypertensive patients. Unfortunately, the devices utilized are not subject to certification and therefore must be validated. In this study, the accuracy and precision of BP measurement with the Oscillomat device were measured and simultaneously compared with those of a standard mercury sphygomomanometer in 60 subjects and with a random zero mercury sphygmomanometer in 44 subjects. The Oscillomat device correctly explored systolic and diastolic BP within a 55 to 210 mmHg range. Compared with the auscultatory method, it tended to underestimate systolic BP values by + 3 to -15 mmHg and diastolic B.P. values by + 1 to -15 mmHg.

Adult↗

PubMed1991

Arterial distensibility and left ventricular hypertrophy in patients with sustained essential hypertension.

Reduced aortic distensibility and compliance may participate in the genesis of cardiac hypertrophy in patients with hypertension. In these patients the increase in end-systolic stress, a determinant factor contributing to the development of cardiac hypertrophy, is influenced not only by the geometric properties of the ventricle but also by the level of systolic pressure. In patients with sustained essential hypertension, the degree of cardiac hypertrophy correlates significantly with the increase in aortic rigidity, which is assessed by the calculation of the characteristic impedance, by the measurement of carotid-femoral pulse-wave velocity, or by the calculation of the Peterson elastic modulus at the level of the aortic arch. Dihydralazine-like substances are unable to modify arterial stiffness, whereas calcium-entry blockers and converting-enzyme inhibitors improve arterial stiffness when achieving the same degree of blood pressure reduction. Modifications in the stiffness of the aorta and other large arteries must be considered to understand reversion of cardiac hypertrophy as a result of antihypertensive treatment.

Antihypertensive Agents↗

PubMed1991

Long lasting arterial effects of the ACE inhibitor ramipril.

The aim of this study was to determine the acute and chronic arterial effects of the ACE inhibitor, ramipril. Fourteen patients (mean age 47 years) with mild to moderate essential hypertension completed the study. A first haemodynamic examination was performed at the end of a 15-day placebo period (D15) before and 3 hours after oral administration of ramipril, 5 mg. Then all the patients started a 4-week treatment with ramipril, 5 mg/day. At the end of this period (D42) the haemodynamic examination was repeated 24 hours after the last capsule intake, and then 3 hours after administration of ramipril 5 mg. Brachial and carotid artery haemodynamics were evaluated by a bidimensional pulsed Doppler system. Arterial distensibility was non-invasively studied in three different arterial segments (carotido-femoral, brachio-radial, femoro-tibial) by the evaluation of the pulse wave velocity. Ramipril significantly decreased BP after acute or chronic administration. Chronic treatment with ramipril was followed by a long lasting increase in brachial artery diameter, a decrease in forearm vascular resistance, and an improvement in aortic distensibility. The other investigated arterial segments did not show any significant changes. Our results suggest that long lasting arterial effects of the ACE inhibitor ramipril are partly pressure-independent and are related to an effect of this drug on arterial tone. These effects may be able to reduce the hypertensive cardiac and arterial abnormalities.

Adult↗

PubMed1990

Effects of sustained-release diltiazem on blood pressure and serum lipids: a multicenter, randomized, placebo-controlled study.

A randomized, double-blind dose-response study on the antihypertensive action of sustained-release diltiazem was performed in four parallel groups. The aim of the trial was to evaluate the antihypertensive efficacy of sustained-release diltiazem and its dose-dependent clinical and biological tolerance. The four homogeneous groups consisted of 25 patients each who had presented with mild to moderate hypertension (diastolic blood pressure of 95-115 mm Hg) in the supine position. The study protocol comprised three successive periods: a placebo period lasting 14 days to verify the persistence of arterial hypertension under placebo; a first therapeutic period during which each of the 25 patients of the four groups received a single daily dose every morning at 9 a.m. of a capsule containing 0.240, 300, or 360 mg of sustained-release diltiazem over a period of 28 days; and a second therapeutic period during which the patients of the four groups received 240, 300, 360, and 300 mg, respectively. All other antihypertensive treatment had been suspended at least 15 days before the initial period under placebo. The results were evaluated with respect to clinical parameters such as systolic blood pressure, diastolic blood pressure, and heart rate, which were measured at 9 a.m. 24 h after the last administration of the drug on days 14, 28, and 56. The plasma serum levels of diltiazem were measured on days 28 and 56, the biological parameters, including measurements of hepatic and renal function as well as lipid and glucose levels, on days 14 and 56, and electrocardiography was performed on days 14, 28, and 56.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Pressure↗

PubMed1990

[Non-invasive study of hemodynamics in peripheral arteries by pulsed Doppler associated with bidimensional echography. A preliminary study].

The purpose of this study is the validation of a 2D-echography and range-gated system to measure internal diameter, and instantaneous blood flow velocity, and to calculate the blood flow, in peripheral arteries (i.e. common carotid artery, femoral artery, and humeral artery). The artery is first visualized using the echographic array probe, its internal diameter (D) is determined and its cross sectional area (S) calculated; the array of the ultrasonic system and the doppler probe are attached and forme a fixed angle. The range-gated doppler system allows the measurement of instantaneous blood flow velocity, with a position of the sample volume covering the internal diameter. Instantaneous velocities are integrated on several cardiac cycles to calculate the mean velocity (Vm). (S. Vm) measures the blood flow. The echographic array probe allows a control of the doppler beam position. In vitro velocities have been measured (N = 20). The fixed angle is 38 degrees 30'; there is an obvious relationship between the calculated and the measured velocities (r = 0.982; p less than 0.0001). The intra-observer reproducibility of measures on common carotid arteries (CCA), femoral arteries (FA), and humeral arteries (HA). In 7 normal patients is, respectively: diameters: (4.9%, 4.12%, 10.2%); velocities: (8.9%, 10.6%, 10.2%). The inter-observers reproducibility is respectively: diameters: (5.6%, 5.4%, 11.4%); velocities: (6.5%, 5.7%, 6.3%). The comparison of 11 measures of diameters and velocities with 20 range-gated doppler gives an obvious relationship (respectively, r = 0.99 p less than 0.0001, r = 0.996, p less than 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1990

[Methods for studying vasodilator agents in arterial hypertension].

The concept of vasodilatation has evolved with regards to the treatment of hypertension. Large multicentre trials have shown that decreasing mean arterial pressure alone does not reduce coronary morbidity and mortality related to hypertension. The authors suggest that the haemodynamic abnormalities related to hypertensive disease were not totally reversed by the antihypertensive agents used in these trials. Regression of structural arterial changes, regression of LVH without altering systolic function, reduction of the variability of blood pressure and maintenance of regional blood flow should all be objectives of any antihypertensive vasodilator therapy. Methods of studying vasodilators are described and the effects of the main classes of antihypertensive drugs on these parameters are analysed.

Antihypertensive Agents↗

PubMed1989

[Hemodynamic effects of perindopril].

1. The effects of prolonged infusion of perindopril (1 mg/kg/d) were studied on Goldblatt rats and spontaneously hypertensive SHR rats compared to control animals. Perindopril increased significantly the arterial compliance in treated animals. Mechanical parameters of the carotid artery are normalized with perindopril infusion in renovascular hypertensive rats and improved in SHR rats. Perindopril reversed the thickness of aortic media in treated rats. After three months treatment the ratio elastine/collagen of the aortic media increased significantly. Perindopril reversed the majority of vascular alteration in both hypertensive groups. 2. Twenty one hypertensive patients received for 30 minutes an infusion of perindoprilat either at 1 mg/kg/min, or at 2.5 mg/kg/min, or dihydralazine at 4 mg/kg/min. It was shown that perindoprilat significantly reduced the blood pressure in the three groups. However the increase in arterial diameter and compliance were only recorded with perindoprilat (2.5 mg/kg/min) infusion. The results of this study pointed out that for the same antihypertensive effect, with two different antihypertensive drugs, the vascular effects can be different. Blood pressure, forearm hemodynamic parameters, echocardiography values were recorded on 16 sustained hypertensive patients before and after one year of perindopril treatment. The results showed that perindopril decreased significantly the SBP, DBP and the MBP, increased diameter and arterial compliance of the brachial artery, and decreased cardiac mass. Three months later, the treatment was stopped for four weeks: blood pressure and hemodynamic values returned toward basal values, whereas mass cardiac didn't increase significantly; then the treatment was continued over 9 months; during this period. The arterial compliance increased again on the cardiac mass remained reduced. (ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1989

[False and true hypertension in the aged subject. Diagnostic errors and potential solutions].

Arterial hypertension has the same definition in elderly people as in young adults. Epidemiologically, it has clearly been demonstrated that in the elderly it is a risk factor of morbidity and cardiovascular mortality. The international reference method for measuring blood pressure is by auscultation and mercury manometer. However, this indirect measurement is the source of many errors due to the material or the observer, or inherent in the method. A typical example of this is pseudohypertension in the elderly. Several solution are offered to improve the reliability of indirect blood pressure measurement, the most convincing one being the use of scientifically validated autonomous instruments relying on the oscillometry system. Ambulatory blood pressure measurement is interesting, being of diagnostic, therapeutic and probably prognostic value, but all this has to be confirmed in elderly subjects.

Aged↗

PubMed1989

[Arterial pressure--self measurement. Recommendations. French Society for Arterial Hypertension--the Measurement Group].

Self-measurement of blood pressure has become widespread in recent years. It may be defined as the measurement of arterial pressure by a conscious and free-willed subject. Self-measurement must remain a medical procedure, which means that doctors should be able to advise their patients (a) on the type of apparatus they should purchase and get validated at regular intervals; (b) on the method of using the apparatus in practice, and (c) on the circumstances, conditions and numbers of measurements to be performed. Doctors must remain responsible for the interpretation of the results obtained and for the diagnostic, pronostic an therapeutic applications of the method. Self-measurement of blood pressure naturally has advantages and disadvantages, but it must be noted that it may offer an alternative to hospitalization or to ambulatory arterial pressure measurement, avoid excessive or defective therapies and improve the patient's compliance with his treatment.

Blood Pressure Determination↗

PubMed1989

Angiotensin converting enzyme inhibition, pulse wave velocity and ambulatory blood pressure measurements in essential hypertension.

Ambulatory blood pressure measurements are better at predicting the outcome of hypertension than single measurements. Since cardiovascular morbidity and mortality are mainly related to large artery damage in hypertensive patients, non-invasive indices of arterial distensibility, such as pulse wave velocity, have been proposed for the evaluation of cardiovascular risk. Indeed, pulse wave velocity is positively correlated with blood pressure (BP) when measured by ambulatory recordings, while there is no correlation with clinical mercury sphygmomanometer readings. Angiotensin converting enzyme (ACE) inhibitors such as perindopril not only reduce high blood pressure, but also increase arterial compliance and distensibility. This latter effect could lead to a more marked decrease in systolic blood pressure than diastolic blood pressure following long-term treatment with ACE inhibitors. This has been demonstrated using ambulatory blood pressure monitoring in hypertensive patients treated with perindopril for three months. The correlation coefficient between ambulatory systolic and diastolic blood pressure before (r = 0.82) and after (r = 0.76) perindopril was significant. Comparison of the corresponding slopes indicated that, for any given value of diastolic blood pressure, systolic blood pressure was significantly lower after perindopril than before perindopril. The action of the drug on the arterial wall may therefore explain the more marked effect on systolic blood pressure than on diastolic blood pressure.

Angiotensin-Converting Enzyme Inhibitors↗

PubMed1988

Sodium and large arteries in hypertension. Effects of indapamide.

Epidemiologic studies evaluating arterial pulse wave velocity together with blood pressure indicate that: (1) salt intake has an independent effect on arteriolar tone and arterial wall properties, with the former indirectly and the latter directly contributing to increased arterial stiffness with age; and (2) normotensive adult subjects who follow a low sodium diet have reduced arterial stiffness and this effect is independent of blood pressure. Conversely, in elderly persons with isolated systolic hypertension, isotonic saline infusion causes a predominant increase in systolic pressure due to an increase in the stiffness of the arterial wall. The diuretic indapamide produces a decrease in blood pressure without significant change in brachial artery diameter. The result indicates a shift of the pressure-diameter curve, reflecting for the first time in humans a pharmacologic effect of the drug on arterial vessel. Furthermore, diuretic drugs may increase arterial distensibility and compliance in hypertensive patients, but this effect seems to be more pronounced in older than in younger subjects. In the latter, either activation of the sympathetic nervous system or potassium depletion, or both, might counteract the improvement in arterial distensibility caused by blood pressure reduction and sodium depletion. Based on epidemiologic, clinical, and pharmacologic studies, this critical review suggests that, in patients with essential hypertension, changes of sodium intake in diet or administration of diuretics, or both, affect the status of large arteries independently of blood pressure changes.

Aging↗