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Biomedical subjects

M Safar

Publications and source records attributed to M Safar.

At least 181 records · Page 10Linked to original sources
PubMed1991

[Vasomotor activity in the large arterial vessels and arterial hypertension].

Hypertension has long been considered to be a disease of the arterioles but it also concerns the great arteries. The hypothesis for this study was that the antihypertensive agents used in the large multicenter trials only partially correct the hemodynamic abnormalities of hypertension. The regression of the structural arterial changes responsible for the decreased arterial compliance, the regression of left ventricular hypertrophy without alteration of systolic function, the decrease in the variability of the blood pressure and the maintenance of regional blood flow should also be considered as therapeutic objectives for vasodilator antihypertensive therapy.

Arteries↗
PubMed1990

Peripheral haemodynamic effects of smoking in habitual smokers. A methodological study.

The effect of smoking on forearm haemodynamics was studied in four groups of healthy subjects, who had all smoked cigarettes (10-15 cigarettes/day) on average for 10 years. Changes in heart rate, blood pressure, forearm blood flow, forearm vascular resistance and pulse wave velocity were determined before and every 15 min for 75 min after smoking two cigarettes within 10 min. The inhaled nicotine was about 2.2 mg. There was no significant difference between the four groups in any haemodynamic variable before or after smoking, which indicated adequate reproducibility of the parameters studied and so made it possible to pool the results from all 30 subjects. Smoking significantly increased blood pressure, heart rate and pulse wave velocity and decreased forearm blood flow. Forearm vascular resistance remained unchanged. The rises in systolic blood pressure and pulse wave velocity were transient and both peaked (7% and 28%, respectively) 15 min after smoking. In contrast, heart rate and diastolic blood pressure remained significantly elevated and forearm blood flow was significantly decreased throughout the 75 min follow-up. The maximal changes were: heart rate +34%, diastolic blood pressure +17%, and forearm blood flow -24%. It is concluded that smoking produces statistically significant changes in forearm haemodynamics affecting both small and large arteries. The reproducibility of the study design means that it can be used to evaluate substances which may antagonize the haemodynamic effects of tobacco smoking.

Adult↗
PubMed1990

Effects of restraint stress on catecholamine concentrations in the glandular stomach of rats.

Restraint stress is known to induce gastric ulcers in rats. Peripheral sympathetic activity and catecholamines are involved in the pathogenesis of these gastric ulcers. The aim of the present study was to evaluate the effects of restraint on mucosal and muscle catecholamine concentrations in the glandular stomach of rats. In unrestrained rats, noradrenaline concentration was higher in the muscle than in the mucosa of the glandular stomach (629 +/- 106 vs 18 +/- 3 pg/mg and 217 +/- 37 vs 18 +/- 8 pg/mg, respectively in the corpus and the antrum, p less than 0.01). This can be explained by the existence of an abundant noradrenergic innervation in the muscle layer. After 20 hours of restraint, adrenaline and noradrenaline concentrations were significantly decreased in adrenals, in comparison with unrestrained animals (255 +/- 53 vs 638 +/- 160 ng/mg and 113 +/- 17 vs 198 +/- 37 ng/mg, respectively for adrenaline and noradrenaline, p less than 0.05). In the glandular stomach, noradrenaline and adrenaline concentrations in restrained rats were not significantly different from those in unrestrained rats. However, adrenaline concentrations in the muscle of restrained rats were higher than in the mucosa. Moreover, restraint induced a significant decrease in dopamine concentration in the antral mucosa (from 100 +/- 12 pg/mg in unrestrained rats to 15 +/- 5 pg/mg in restrained rats), suggesting that a depletion in dopamine in the antral mucosa could be one of the pathogenetic factors involved in antral gastric stress-induced ulcers in rats.

Animals↗
PubMed1990

Flow-dependent vasodilation of brachial artery in essential hypertension.

Brachial artery hemodynamics including brachial artery diameter (D) and local blood flow velocity (V) was studied in 15 normotensive subjects (NT) and 19 age-matched hypertensive patients (HT) at rest using a bidimensional pulsed Doppler system during a 2-min period of distal circulatory occlusion and during reactive hyperemia. Kinetics of changes in V and D were determined during successive and reproducible maneuvers. V and D decreased significantly during distal circulatory occlusion in both groups. During reactive hyperemia, V reached similar maximum values in both groups, and D increased significantly in NT and HT. Changes in D during reactive hyperemia were positively and significantly correlated with changes in V recorded at the same level. No significant difference was found between the two groups. These results demonstrate noninvasively that there are velocity-dependent variations in the diameter of a large artery in humans and suggest that velocity-dependent vasodilation of the brachial artery is not impaired in essential hypertension.

Adult↗
PubMed1990

Ageing and its effects on the cardiovascular system.

The study of the effect of ageing per se on cardiovascular structure and function is hindered by the occurrence of disease processes and lifestyle changes which are inextricably linked to the ageing process. Both autopsy data and non-invasive techniques such as echocardiography have revealed a progressive hypertrophic increase in left ventricular wall thickness from the third decade of life onwards, although ageing does not lead to wall thicknesses exceeding the upper limit of normal. However, ventricular cavity dimensions are relatively unaffected by age. Left ventricular hypertrophy is an adaptive response to the increase in cardiac afterload caused by age-related arterial dilatation and loss of vascular compliance. In the large arteries, clinically significant intimal thickening and loss of distensibility occur by the age of 60 years, resulting in increased pulse pressure through elevation of systolic pressure. By comparison, the contribution of increased peripheral resistance to the development of hypertension in the elderly is relatively small. With increasing age, prolongation of isovolumic cardiac relaxation and loss of ventricular compliance combine to reduce the efficacy of early ventricular diastolic filling, but an increased atrial contribution to late ventricular filling offsets this, and no loss of left ventricular end-diastolic volume results. Resting cardiac output declines with ageing in healthy subjects. With increasing age, alpha-adrenoceptor-mediated effects on the vasculature appear to predominate, resulting in net vasoconstriction. An age-related decline in cardiovascular performance under stress can be demonstrated by the measurement of maximal oxygen consumption during exercise.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
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

Haemodynamic aspects and serotonin.

Serotonin (5-HT) induced a transient decrease followed by an increase and then a longer-lasting decrease in blood pressure. The initial decrease in blood pressure results from a reduction in cardiac output as a result of the profound bradycardia. The secondary increase in blood pressure is caused by an increase in both cardiac output and total peripheral resistance. The final decrease in blood pressure is ascribed to a reduction in total peripheral resistance. The effects of 5-HT on regional haemodynamics are known to vary according to the vascular bed and even in the same vascular bed. Accordingly, 5-HT induced either vasoconstriction or vasodilatation. Vasoconstriction occurred in most cases in large arteries and is due to stimulation of 5-HT2 receptors. However, 5-HT1-like receptors are probably also implicated. 5-HT-induced vasodilatation is attributed to stimulation of 5-HT1-like receptors. However, limited evidence suggests also an implication of 5-HT3 and even 5-HT2 receptors in the dilator effects of 5-HT. 5-HT1A receptor agonists decreased blood pressure by a reduction in total peripheral resistance. This vasodilatation seems to be widespread. Other 5-HT1-like receptor agonists have differential effects according to the animal species used.

Animals↗
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↗
PubMed1990

Conjugated catecholamines in human plasma: where are they coming from?

The origins of conjugated catecholamines remain poorly known. The aim of the present study was to see whether a major contribution comes from the sympathetic nervous system. We have assumed some kind of parallelism between the activity of the sympathetic nervous system, the amount of catecholamines released and taken up, and the amount of conjugated catecholamines circulating in plasma. Accordingly, an increase in sympathetic activity should be followed by an increase in the plasma level of conjugated catecholamines. The plasma levels of sulfoconjugated and glucuroconjugated catecholamines were measured in 10 patients with mental disease resistant to drug treatment, before and after electroconvulsive therapy. As expected, blood pressure, norepinephrine concentration, and epinephrine concentration in plasma were transiently increased. Neither sulfoconjugated nor glucuroconjugated catecholamines were significantly changed. Conjugated catecholamines were measured in 10 volunteers before and at the nadir of insulin-induced hypoglycemia. As expected, plasma levels of norepinephrine and epinephrine were drastically increased. Plasma levels of sulfoconjugates were decreased and glucuroconjugates increased; these were narrow but statistically significant variations. Data reported in the present article do not support a major role for the activity of the sympathetic system in fixing the level of conjugated catecholamines in human plasma. This is a negative, but nonetheless important, observation. In human subjects, currently available information suggests an important role for the intestinal wall and renal function in determining the level of circulating sulfoconjugates.

Blood Glucose↗
PubMed1990

Haemodynamic effects of perindopril in essential hypertension.

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

Adult↗
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

Treatment of hypertension based on both systolic and diastolic pressure could influence the cost of therapy.

The decision to start antihypertensive treatment is based on the statistical results of therapeutic trials done in large populations. The application of statistical estimations may extend the indications for antihypertensive therapy to individual subjects who might be marginally improved by antihypertensive treatment. This problem is due to the well-known heterogeneity of the hypertensive population. One of the most common factors reflecting the heterogeneity of this population is the level of systolic pressure versus that of diastolic pressure. Disproportionate increases in systolic pressure in patients over 50 years reflect principally the arterial changes associated with elevated blood pressure. Arterial changes, as evidenced by the decreased compliance of large arteries, may require a specific therapeutic approach, which could influence the choice and consequently the cost of antihypertensive therapy.

Antihypertensive Agents↗
PubMed1989

Calcium blocker lacidipine and carotid arteriolar vasodilation in healthy volunteers.

Systemic and carotid hemodynamics were studied in 10 healthy male volunteers before and after short-term administration of a 4 mg dose of the calcium entry-blocker lacidipine in a placebo-controlled, double-blind, crossover study. Hemodynamic parameters of the right common carotid artery were measured before and at 1 1/2 and 3 hours after dose administration by means of pulsed Doppler flowmetry. In addition, systemic hemodynamic parameters were calculated from cardiac impedance measurements at the same time. In comparison with placebo, lacidipine produced a significant decrease in blood pressure, together with systemic and carotid arteriolar dilatation. Heart rate increased sharply, whereas carotid arterial diameter and tangential tension did not change. The study provided evidence that the calcium entry-blocker lacidipine produces systemic and carotid arteriolar vasodilation and that the heart rate baroreflex response after administration of calcium inhibitor is not associated with a significant modification of the geometry of carotid arterial wall.

Administration, Oral↗
PubMed1989

Vascular changes in hemodialysis patients in response to recombinant human erythropoietin.

The partial correction of anemia with recombinant human erythropoietin (rHuEpo) is frequently associated with an increase in arterial pressure and could oppose the beneficial effect of anemia correction on myocardial function. In order to analyze the influence of rHuEpo therapy on the vessels and the heart, we performed systemic and regional hemodynamics studies in 11 hemodialysis patients before and 10 to 35 weeks after initiation of rHuEpo therapy, when hemoglobin concentration was 6.8 +/- 0.9 and 10.6 +/- 0.66 g/dl (mean +/- SD), respectively. The mean arterial pressure remained unchanged during this period (88 +/- 21 vs. 88 +/- 15 mm Hg). Echocardiographic study showed that rHuEpo treatment led to a decrease in left ventricular end-diastolic diameter (4.9 +/- 0.5 vs. 5.1 +/- 0.6 cm; P less than 0.03), left atrial diameter (3.22 +/- 0.30 vs. 3.43 +/- 0.33; P less than 0.03), and left ventricular mass index (109.8 +/- 30.6 vs. 133 +/- 30.8 g/m2; P less than 0.05). Left ventricular ejection volume decreased from 86 +/- 24 to 75 +/- 19 ml (P less than 0.03) and heart rate from 76 +/- 9 to 70 +/- 10 beats/min (P less than 0.05). Cardiac index decreased from 4715 +/- 700 to 3635 +/- 444 ml/min/m2 (P less than 0.01) and peripheral resistances rose from 1480 +/- 162 to 1943 +/- 250 dynes.sec.cm-5.m2 (P less than 0.01). Fractional ejection and mean circumferential fiber shortening remained unchanged. The treatment with rHuEpo did not change the aortic diameters.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Effects of twenty-four hours of bed rest with head-down tilt on cardiopulmonary baroreflex control: preliminary study.

The cardiopulmonary baroreflex response was studied before and after 24 h bed rest with head-down tilt (-5 degrees) in six normal male subjects, through lower body negative pressure (-5, -10, -15 mmHg) and passive leg raising. The reflex response was assessed (using plethysmography) by changes in forearm vascular resistance. During the lower body negative pressure and leg raising, forearm vasoconstriction and vasodilation were similar before and after head-down tilt. The study shows that orthostatic intolerance following head-down tilt is not explained by an abnormality in the response of low pressure baroreceptors.

Adult↗
PubMed1989

Large and small forearm arteries of essential hypertensives are less reactive to angiotensin II than to noradrenaline.

In order to investigate the reactivity to angiotensin II (Ang II) in large and small arteries in situ, brachial artery diameter, blood flow velocity, local volumic blood flow and local vascular resistance (mean arterial pressure divided by local blood flow) were determined non-invasively, using a pulsed Doppler system. Increasing doses of Ang II (0.5, 1.0 and 2.0 ng/kg per min) were given intravenously and double-blind to nine normotensive subjects (group I) and 10 hypertensive patients (group III); placebo (glucose) was given to nine hypertensives (group II). Angiotensin II did not change the brachial artery diameter, blood flow velocity, local blood flow or local resistance. Mean arterial pressure was increased slightly but significantly (P less than 0.05) by Ang II at 2 ng/kg per min in groups I and III. In contrast, we had shown previously, following the same procedure, that subthreshold doses (for the increase in mean arterial pressure) of noradrenaline reduced branchial artery diameter, velocity and local blood flow and increased local resistance in hypertensives. These results indicate that in hypertensives the vascular reactivity of the brachial circulation (1) is lower than that of other territories in response to Ang II and (2) is lower in response to Ang II than in response to noradrenaline.

Angiotensin II↗