Biomedical subjects

J Levenson

Publications and source records attributed to J Levenson.

At least 163 records · Page 9Linked to original sources

PubMed1987

The efficacy of a transdermal formulation of clonidine in mild to moderate hypertension and its effects on the arterial and venous vasculature of the forearm.

We have studied the efficacy of clonidine hydrochloride administered transdermally once a week for 9 to 15 weeks in 12 patients with mild to moderate hypertension. Clonidine reduced both supine and standing blood pressures on average, but only 8 subjects were responders, i.e. had a decrease in supine diastolic blood pressure to below 90 mm Hg or more than 10% from baseline. Supine heart rate was unchanged, but in the responders the orthostatic increase in heart rate was reduced by clonidine from baseline (p less than 0.05). Moreover, in all the patients the change in the orthostatic increase in heart rate was correlated with the change in supine diastolic pressure (p less than 0.05). Brachial artery blood flow, forearm arterial compliance, vascular resistance, and venous tone were not affected by clonidine. Thus, transdermal clonidine reduced blood pressure, probably by a baroreflex-mediated effect, but did not affect the vasculature of the forearm.

Administration, Cutaneous↗

PubMed1987

The role of antihypertensive drugs in counteracting adverse influence on large arteries.

Studies in humans have shown that chronic elevation of blood pressure induces early alterations in the large arteries, consisting mainly of increased diameter, increased pulse wave velocity, and decreased arterial compliance. Acute reduction of blood pressure, per se, does not necessarily correct these alterations homogeneously. For instance, cadralazine reduced brachial artery diameter and urapidil decreased pulse wave velocity, without accompanying changes in forearm arterial compliance. In contrast, acebutolol, isosorbide dinitrate, nicardipine, and nitrendipine, for the same acute decrease in blood pressure, improved forearm arterial compliance by a concomitant decrease in pulse wave velocity and increase in arterial diameter. To determine whether or not these vascular effects persist with long-term acebutolol therapy, nine hypertensive patients were treated for a period of 3 months. Forearm hemodynamic and cytosolic free calcium concentrations in platelets were simultaneously assessed before and after treatment. Compared with placebo baseline values, chronic acebutolol therapy significantly decreased mean arterial pressure (p less than 0.01), pulse wave velocity (p less than 0.01), and platelet free calcium concentration (p less than 0.05); forearm arterial compliance was increased (p less than 0.01), but brachial artery diameter did not change. Platelet calcium concentration correlated closely with pulse wave velocity even at constant mean arterial pressure. These findings suggest a relaxant effect of acebutolol on the smooth musculature of large arteries, which is independent of changes in blood pressure and arterial diameter, and possibly mediated by changes in cytosolic calcium levels.

Acebutolol↗

PubMed1987

Overview on atherosclerotic systolic hypertension.

Hypertension in older atherosclerotic patients is characterised by a disproportionate elevation of systolic and pulse pressure contrasting with a subnormal diastolic level. Increased systolic pressure is strongly related to the excess of cerebrovascular complications and congestive heart failure observed in these patients. The physiopathological pattern is marked by a strong reduction in compliance of large arteries directly responsible for the predominant high systolic pressure because of the impairment of the buffering function of the arteries on the cardiac pulse wave. Clinical management is directed to the elevation of athero-arteriosclerotic changes of large arteries by means of appropriate non-invasive ultrasonic techniques and specific lowering in systolic pressure. Antihypertensive treatment must specifically decrease systolic pressure without superimposing adverse effects on the generalized and focalized atherosclerotic process. In this respect, new pharmacological agents capable of direct actions on large arteries might be suitable.

Aged↗

PubMed1987

Haemodynamic basis of early modifications of the large arteries in borderline hypertension.

Quantitative evaluation of brachial artery diameter, blood velocity and flow (pulsed Doppler velocimetry) and of forearm arterial compliance (FAC)--mathematical analysis of the simultaneous diastolic pressure and flow according to a first-order arterial model--was carried out in 10 normotensive controls, and in 23 borderline hypertensive patients, of the same age. Using a value of 2 standard deviations above the average cardiac index of 20 normotensive subjects, enabled us to classify 12 patients as having a normal cardiac output and 11 patients as having a high cardiac output. Each group was of similar age and pressure. FAC was lower in patients with a normal cardiac output than in normal controls (P less than 0.01) and also lower than in patients with high output (P less than 0.01). Brachial artery diameter and flow were higher in patients with high output than in normal controls (P less than 0.01, P less than 0.001) and also higher than in patients with a normal output (P less than 0.001). A positive correlation (r = 0.55; P less than 0.01) was found between heart rate and brachial artery diameter in the 23 patients. These results demonstrate a non-homogenous pattern of brachial artery characteristics of patients with borderline hypertension. Patients with normal cardiac output exhibited a clear reduction of the distensibility of the forearm arteries while patients with high cardiac output had strong dilation of the brachial artery.

Adult↗

PubMed1987

Large arteries in hypertension: heterogeneous haemodynamic response to beta-adrenoceptor antagonists with and without intrinsic sympathomimetic activity.

1. Hypertension is associated with a distension of the large arteries and consequently a marked reduction in arterial compliance, which does not result merely from the mechanical effects of elevated arterial pressure but also from early functional and/or structural changes in the arterial walls. This suggests that one of the aims of antihypertensive therapy should be to reverse these arterial abnormalities in the hope of protecting the patient from the atherosclerotic complications of hypertension. 2. Studies have been carried out to compare the effects of equieffective antihypertensive doses of pindolol and propranolol on the arterial circulation in patients suffering from essential hypertension. After 3 months therapy pindolol produced a dilatation of the brachial artery with an increase in arterial compliance and blood flow. In contrast, propranolol, despite comparable antihypertensive effects, did not influence brachial artery circulation. 3. These different effects on the arterial circulation presumably reflect the differing pharmacological properties of the two beta-adrenoceptor antagonists and suggest that the intrinsic sympathomimetic activity of pindolol may be responsible for the qualitative differences in the arterial responses to the two drugs. 4. The results reviewed here reveal that even when two drugs of the same class are used to treat patients with essential hypertension the effects of these agents on arterial haemodynamics can vary greatly and are unrelated to the degree of blood pressure lowering. Thus, pindolol, in contrast to propranolol, not only lowers blood pressure but also reverses some of the changes in arterial haemodynamics which are characteristic of hypertensive disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic beta-Antagonists↗

PubMed1987

Brachial arterial changes in response to wrist occlusion in normotensive and hypertensive men.

Diameter, blood velocity, and flow of the brachial artery and vascular resistance of the brachial circulation were evaluated with a pulsed Doppler velocimeter before and after wrist occlusion in 8 younger and 8 older normotensive subjects and in 11 younger and 11 older hypertensive patients. Before occlusion, no differences existed between younger and older normotensives. However, in hypertensives, systolic peak velocity was higher in younger than in older hypertensives (P less than 0.001) and correlated to age in the overall patients (r = -0.57, P less than 0.01). Occlusion decreased velocity and flow and increased vascular resistance in all groups, but the change in resistance was not correlated with the base-line resistance. During occlusion, no differences existed between younger and older normotensives. However, in hypertensives mean and systolic peak velocity was higher (P less than 0.01), and vascular resistance was lower (P less than 0.01) in younger than in older patients. In hypertensive patients, during occlusion mean and systolic peak velocity were negatively correlated to age (r = -0.72, P less than 0.001; r = -0.59, P less than 0.01), and vascular resistance was positively related to age (r = +0.66, P less than 0.001). Thus wrist occlusion modified the brachial circulation in normotensive and hypertensive populations but revealed age-related differences only in hypertensive patients, suggesting a combined effect of age and hypertension on the muscle vascular bed.

Adult↗

PubMed1987

[Early changes in the circulation of the humeral artery in borderline arterial hypertension].

The brachial artery diameter and blood flow rate were measured by pulsed Doppler velocimetry in 9 healthy subjects and 24 patients of the same age group with borderline hypertension. To evaluate the results, the patients were divided into two groups according to their cardiac output: high cardiac output group (i.e. patients whose cardiac output was superior to the mean +/- 2 S.D. value in the control population), and normal cardiac output group (i.e. cardiac output lower than that value). Patients in both groups were of the same age and had the same level of blood pressure. The brachial artery diameter and blood flow rate values were the same in the normal cardiac output group and in the control population. However, these values were significantly higher in patients with high cardiac output than in controls (P less than 0.05 and P less than 0.001) and in patients with normal cardiac output (P less than 0.01). These results suggest that the haemodynamic profile in the brachial artery is not the same in all patients with borderline hypertension: there was a tendency to vasoconstriction in patients with normal cardiac output, whereas the brachial artery was clearly dilated in patients with high cardiac output.

Adult↗

PubMed1987

[Study of the visco-elastic response of the aortic wall to angiotensin and noradrenaline in the conscious dog by analysis of the instantaneous pressure-diameter relation in the descending aorta].

The viscoelastic behaviour of the aorta has been studied in 7 adult non-anesthesized mongrel dogs, chronically instrumented with a microtransducer pressure (Konigsberg P7) implanted inside the aortic lumen, and 2 ultrasonic crystals diametrically opposed and fixed in the adventitia of the thoracic aorta. Pressure and diameter were analysed in terms of mean values and of systolic diastolic variations, enabling to calculate the elastic modulus of Peterson. After recovery from surgery, and under autonomic blockade by atropine and propranolol, perfusions of angiotensin and norepinephrine were performed at incremental steps of doses. In individual dogs, instantaneous pressure-diameter relationships were formed by the different pressure diameter hysteris loops obtained at each dose of the same drug; the relationships obtained with the two drugs were curvilinear and were mixed at lower pressure ranges, but at highest levels of pressures it was found, that comparatively to angiotensin curve, that of norepinephrine had shifted toward lower diameter. The percent increase in mean diameter from baseline obtained at each dose of the same drug, was positively correlated to the corresponding per cent increase in mean pressure, with angiotensin (r = 0.83 P less than 0.001), and for norepinephrine (r = 0.82 P less than 0.001), but the slope of the relation was lower with angiotensin (22.3 +/- 3.2) than with norepinephrine (12.8 +/- 1.9) (P less than 0.001); likewise, the elastic modulus, for each dose of a same drug, was positively correlated to the corresponding mean pressure for angiotensin (r = 0.53 P less than 0.01), norepinephrine (r = 0.69 P less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin II↗

PubMed1987

[Effect of smoking on blood viscosity and arterial rigidity in normal and hypertensive subjects].

The purpose of the study was to assess whether cigarettes smoking could induce blood hyperviscosity and arterial rigidity in 30 normotensive and 70 hypertensive men aged from 24 to 65 years. Of those, 20 normotensive and 20 hypertensive were cigarettes smokers, while the remaining subjects were non smokers. Age and weight were similar in the 4 groups of subjects. A couette viscometer with coaxial cylinders allowed the measurements of blood viscosity over a wide range of shear rates (0.033 to 241 sec-1) mimicking the flow condition of the circulation, and two strain gauge transducers permitted the measurements of the brachial to radial pulse wave velocity as an index of arterial wall distensibility. In normotensive subjects cigarettes smoking increased pulse wave velocity from 7.1 + 1 to 9.2 + 0.6 m/sec. (P less than 0.05) as well as blood viscosity, which increased both at higher shear rates (+10% from 52 to 241 sec-1, P less than 0.05) and lower shear rates (+20% from 11.2 to 0.2 sec-1, P less than 0.02). In hypertensives, cigarettes smoking increased pulse wave velocity (9.8 + 0.3 to 11.3 + 0.4; P less than 0.05) and blood viscosity (4% at higher shear rate P less than 0.05 and 10% at lower shear rates P less than 0.02). Although hypertensive patients had increased pulse wave velocity and blood viscosity compared to normotensive controls, these variables were not significantly different when hypertensive non smokers were compared to normotensive. The present study demonstrated that cigarettes smoking produced in normotensive and hypertensive men significant rheological disturbances of flow and wall arteries.2

Adult↗

PubMed1987

Combined effects of sex and hypertension on the geometrical design of large arteries. Sexual differences in normal and hypertensive forearm arteries.

The effects of sex, hypertension, morphological status, and heart rate were assessed on the large arteries of 46 normotensive subjects (23 men and 23 women) and 50 hypertensive patients (25 men and 25 women) by means of pulsed Doppler determination of diameter and blood velocity of the brachial artery. Compared with men, women had lower height, weight, and forearm volume (p less than 0.001), higher heart rate (p less than 0.001), and lower brachial artery diameter (p less than 0.001), both in the normotensive and hypertensive groups. Compared with normotensive subjects, hypertensive patients of the same sex showed an increase in brachial artery diameter (only significant in men [p less than 0.001]) and an increase in heart rate (only significant in women [p less than 0.001]). The multiple regression analysis of brachial artery diameter showed significant coefficients for sex and hypertension (p less than 0.001) and for age and heart rate (p less than 0.05); the multiple regression analysis of blood velocity showed that only coefficient of hypertension was significant (p less than 0.05). The study of first-order interactions between the independent variables revealed that effect of sex on arterial diameter did not depend on the other variables. In contrast, the effects of age and heart rate were influenced by the presence or the absence of hypertension, and arterial caliber was positively related to age in normotensive subjects (p less than 0.05) but not in hypertensive patients and negatively related to heart rate in hypertensive patients (p less than 0.01) but not in normotensive subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1987

Platelet cytosolic free Ca2+ concentration and plasma cholesterol in untreated hypertensives.

It has been proposed that plasma cholesterol, a major risk factor for atherosclerosis, may modify cellular Ca2+. In particular, higher membrane cholesterol contents induce higher Ca2+ influx and decrease the activity of the Ca2+ pumps. Cellular Ca2+ may also control the number of accessible low density lipoprotein receptors. We investigated the question of whether plasma cholesterol influences cellular Ca2+ metabolism, by analysing the cytosolic free Ca2+ concentration [( Ca2+]i) in unstimulated platelets from 61 untreated hypertensive patients [systolic and diastolic arterial pressure: 157 +/- 3/95 +/- 2 mmHg (mean +/- s.e.m.), respectively, age 41.8 +/- 1.7 years, body mass index 24.7 +/- 0.6 kg/m2]. The subjects' plasma total cholesterol (5.5 +/- 0.5 mmol/l) and platelet [Ca2+]i concentration (228 +/- 7 nmol/l) were positively correlated (r = 0.375, P less than 0.003). This correlation persisted at constant age, arterial pressure or body mass index. Platelet [Ca2+]i tended to increase with plasma low-density lipoprotein concentration (n = 21, P = 0.01), and to decrease with the ratio of high-density lipoprotein cholesterol to total cholesterol (n = 21, P = 0.08). The observation that in normocholesterolaemic hypertensive patients [Ca2+]i concentration in unstimulated platelets was correlated with plasma cholesterol suggests that cell activation may be modulated by membrane fluidity or that cholesterol metabolism is influenced by cell Ca2+.

Adult↗

PubMed1986

[Does arterial compliance play a role in the physiopathology of hypertension?].

The buffering function of arteries consists of damping down cardiac pulsatility. This function can be evaluated by measuring arterial compliance using pulsed Doppler and pulse wave velocity measurements and analysis of pressure and flow waves in arteries. In human hypertension, the reduction of arterial compliance is well-documented; it is not only due to increased stretching of the arteries consecutive to the rise in blood pressure, but also to the fact that structural and/or functional changes in these vessels, as suggested by the fact that compliance is reduced in patients with borderline and mild hypertension and does not necessarily vary in parallel to drug-induced changes in blood pressure. Furthermore, arterial compliance is heterogeneously altered in borderline hypertension according to the level of cardiac output and in sustained hypertension according to the degree of arterial aging. Finally, reduced arterial compliance, by impairing the buffering function of arteries, increases arterial pulsatility and its adverse effects on cardiac load and on cyclic stress of arteries.

Arteries↗

PubMed1986

Chronic effects of pindolol on the arterioles, large arteries, and veins of the forearm in mild to moderate essential hypertension.

The effects of pindolol were studied on the large arteries, arterioles, and veins of the forearm in 13 patients with essential hypertension after 12 weeks of dosing. The methods used were pulsed Doppler velocimetry of the brachial artery and strain gauge mercury-in-silicone rubber plethysmography of the forearm. Compared with placebo baseline values, chronic pindolol significantly decreased systolic and diastolic blood pressure (P less than 0.001), pulse pressure (P less than 0.001), and pulse rate (P less than 0.05). A significant increase was observed in brachial artery diameter (P less than 0.01), brachial artery blood flow and velocity (P less than 0.001), and forearm arterial flow (P less than 0.001). Forearm vascular resistance and venous tone were decreased (P less than 0.001 and P less than 0.05, respectively), whereas forearm arterial compliance was increased (P less than 0.001). These results demonstrate a dilatory effect on large and small peripheral arteries and on veins of pindolol after chronic dosing, which leads to improvement in the conduction and buffering arterial function of the forearm.

Adult↗

PubMed1986

Isosorbide dinitrate and pulsatile arterial haemodynamic variables in hypertension.

The effect of a sustained-release oral isosorbide dinitrate (ISDN) preparation on cerebral and forearm circulation was determined in 16 patients with mild to moderate essential hypertension. Measurements were made by pulsed Doppler velocimetry in the common carotid and the brachial arteries. Pulse wave velocity of the forearm was simultaneously recorded by means of strain gauge arterial mechanography allowing non-invasive evaluation of compliance and characteristic impedance of the brachial artery. Four hours after ISDN ingestion, the patients exhibited a significant decrease in blood pressure without a change in heart rate. An increase in carotid and brachial artery diameter was shown whereas blood flow increased only in the forearm. Resistance decreased significantly in both carotid and brachial vascular beds but only in the brachial vascular bed was the baseline resistance directly correlated with the change in brachial bed resistance. Concerning pulsatile large artery parameters, pulse wave velocity and characteristic impedance diminished, and brachial artery compliance increased significantly. The tangential tension of carotid and brachial arteries did not change. An increase in plasma renin activity was observed and related to the vasodilating effect on small arteries of the brachial vascular bed. This study showed that the antihypertensive effects of ISDN were accompanied by a strong vasodilatory action on small and large arteries and by an improvement in the pulsatile behaviour of large arteries.

Adult↗

PubMed1986

Evidence of early changes of the brachial artery circulation in borderline hypertension.

Quantitative evaluation of brachial artery diameter and blood flow (pulsed Doppler velocimetry) was carried out in nine normal subjects and 24 borderline hypertensive patients of the same age. The analysis of patients according to their value of cardiac index compared with the normal mean value plus 2 SD (standard deviation) enabled us to subdivide the patients into those with normal cardiac output and those with high cardiac output of similar age and pressure. Brachial artery diameter and flow were not different in patients with normal output and in normal controls, but were higher in patients with high output than in normal controls (p less than 0.05; p less than 0.01) and lower in patients with normal output than those with high output (p less than 0.01). These results demonstrate a nonhomogeneous pattern of the brachial artery of patients with borderline hypertension. Patients with normal cardiac output exhibited a trend to vasoconstriction, while patients with high cardiac output had a strong dilatation of the brachial artery.

Adult↗

PubMed1985

Pulsed Doppler evaluation of diameter, blood velocity and blood flow of common carotid artery in sustained essential hypertension.

Diameter, blood flow velocity, and volumic flow of the common carotid artery were measured in 38 patients with sustained essential hypertension and compared with those of 38 age-matched normal subjects. Both hypertensive and control subjects were classified according to age into those younger and those older than 45 years. For the determinations, a pulsed Doppler velocimeter with an adjustable range-gated time system and a double transducer probe was used. In the younger group, the diameter of the common carotid artery had a similar value in hypertensive patients (0.639 +/- 0.014 cm) and in controls (0.651 +/- 0.015). The same level of blood flow velocity in hypertensive patients (19.7 +/- 0.9 cm/s) and in controls (21.2 +/- 0.9 cm/s) was observed. Therefore, the volumic flow was equal in the common carotid artery of the hypertensive patients (385 +/- 20 ml/min) and of the normotensive subjects (410 +/- 23 ml/min). In the older group, blood flow velocity was reduced in the common carotid artery of the hypertensive patients (19.4 +/- 1.0 cm/s vs. 15.6 +/- 0.6 cm/s; p less than 0.01), but the diameter was unchanged (0.653 +/- 0.018 cm in hypertensive patients and 0.665 +/- 0.018 cm in controls). Thus, there was a significant reduction of volumic blood flow in common carotid artery of the hypertensive patients over 45 years (321 +/- 14 ml/min). A negative relationship was observed between common carotid artery blood flow and age in elderly hypertensive patients (r = -0.42; p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1985

The effect of acute and chronic nicardipine therapy on forearm arterial haemodynamics in essential hypertension.

By using simultaneous recording curves obtained with pulsed Doppler velocimetry and strain gauge mechanography, forearm arterial haemodynamics were studied in 26 patients with mild to moderate essential hypertension. Fifteen patients received a single oral dose of nicardipine 40 mg, and 11 patients were treated with nicardipine 30 mg three times daily for 3 months. In both groups of patients there was a similar and significant (P less than 0.001) reduction in mean, systolic, and diastolic pressures. There was a slight increase in heart rate (P less than 0.05) after the single dose, but no change after 3 months of treatment. The diameter, blood velocity, and blood flow of the brachial artery increased significantly in both treatment groups. The decrease in forearm vascular resistance was significant for both treatment groups. Brachial artery compliance increased (P less than 0.01) and characteristic impedance decreased (P less than 0.01) after both single-dose and long-term therapy with nicardipine. In patients who received nicardipine for 3 months, there were close correlations between the baseline serum calcium level and the percent change in vascular resistance (r = -0.73, P less than 0.01), blood flow (r = 0.89, P less than 0.001), and blood velocity (r = 0.91. P less than 0.001) of the forearm. No correlation was found between the baseline serum calcium and the change in arterial pressure. This study provided evidence that the blood-pressure-lowering effect of nicardipine was accompanied by a direct vasodilatory action in the small and large arteries of the forearm. An increase in peripheral blood flow with concomitant improvement of arterial compliance are the consequences of these arterial actions.

Blood Pressure↗

PubMed1985

Elevation of brachial arterial blood velocity and volumic flow mediated by peripheral beta-adrenoreceptors in patients with borderline hypertension.

Simultaneous determinations of cardiac output and brachial arterial blood flow were performed in patients with hypertension and high cardiac output in comparison with normal subjects of the same age. Brachial arterial blood flow was measured with a previously described pulsed Doppler apparatus that permitted the noninvasive determination of arterial diameter and blood flow velocity. In patients with borderline hypertension, brachial blood flow was significantly increased (136 +/- 11 vs 72 +/- 8 ml/min; p less than .001). After short-term administration of indomethacin, cardiac output decreased while brachial blood flow remained constant. After short-term administration of a selective beta 1-receptor antagonist (primidolol) and nonselective blocker (propranolol), cardiac output decreased significantly in both cases but the decrease in brachial blood flow was significant only after the administration of the nonselective beta-blocking agent. The study strongly suggested that in patients with borderline hypertension, the increased cardiac output is related to a prostaglandin and beta 1-adrenergic mechanisms whereas the increased brachial blood flow depends mainly on beta 2-adrenergic mechanisms.

Adult↗