Biomedical subjects

A C Simon

Publications and source records attributed to A C Simon.

At least 37 records · Page 2Linked to original sources

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

Arterial dynamics, cardiac hypertrophy, and antihypertensive treatment.

The relationship between cardiac hypertrophy, ventricular function, and aortic volume distensibility was studied in men with sustained essential hypertension by echocardiography and determination of pulse-wave velocity. The more reduced the aortic distensibility, the higher was the blood pressure response to exercise and the greater were the degree of cardiac hypertrophy and the modifications in systolic time intervals. Changes in cardiac performance as determined by vasodilators equipotent in relation to blood pressure reduction were found to have markedly different effects on aortic distensibility; volume distensibility was unchanged by cadralazine but was improved by calcium entry blockers and isosorbide dinitrate. Our findings suggest that alterations in the buffering function of the large arteries, as indicated by decreased volume distensibility, participate in the increased afterload in patients with essential hypertension and thus influence the degree of cardiac hypertrophy and changes in cardiac function and selective use of antihypertensive drugs may influence cardiovascular morbidity and mortality by their differential effect on large-vessel distensibility.

Antihypertensive Agents↗

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

[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↗

PubMed1986

Effect of cadralazine on brachial artery hemodynamics and forearm venous tone in essential hypertension.

Forearm venous tone and brachial artery hemodynamics, including determinations of the arterial diameter and compliance by the use of pulsed Doppler systems, were measured in 16 patients with sustained essential hypertension before and after acute oral cadralazine dosing. Systolic and diastolic blood pressures significantly decreased, whereas heart rate increased. Brachial artery diameter and vascular resistance decreased, respectively, from 0.501 +/- 0.015 to 0.485 +/- 0.015 cm (P less than 0.001) and from 124.8 +/- 13.8 to 99.3 +/- 11.9 mm Hg/ml . sec (P less than 0.01). Blood flow velocity increased (P less than 0.05) but volumic flow, pulse wave velocity, and brachial artery compliance did not change. Forearm venous tone increased but the increase was inversely related to the degree of arteriolar vasodilatation. Our results indicate that, with cadralazine, forearm vascular resistance decreased while forearm blood flow was unchanged, the dilatation of small arteries contrasted with a significant reduction in the diameter of the large brachial artery, and the decrease in blood pressure was associated with a lack of increase in arterial compliance and changes in venous tone. This suggests an overriding influence of the activation of the autonomic nervous system on the action of cadralazine on large arteries and veins.

Administration, Oral↗

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

Comparative effects of propranolol and pindolol on small and large arteries and veins of the forearm circulation in hypertensive man.

Brachial artery diameter (pulsed Doppler method), forearm vascular resistance, and venous tone (plethysmographic method) were studied in 18 patients with sustained essential hypertension. Hemodynamic parameters were reevaluated after 3 months of treatment by propranolol (9 patients) or pindolol (9 patients). For the same decrease in pressure, propranolol decreased heart rate significantly while pindolol did not, indicating the role of intrinsic sympathomimetic activity. After pindolol, forearm vascular resistance and venous tone significantly decreased while brachial artery cross-sectional area significantly increased. After propranolol, forearm vascular resistance and brachial artery cross-sectional area did not change significantly, while forearm venous tone increased markedly. The study shows that, in the long term, pindolol dilates small and large arteries and veins of the forearm circulation whereas Propranolol apparently does not.

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↗

PubMed1986

Haemodynamic effects of vasodilating drugs on the common carotid and brachial circulations of patients with essential hypertension.

The haemodynamic pattern of the common carotid artery was studied in men with sustained essential hypertension using pulsed Doppler methods before and after administration of vasodilating drugs. Captopril produced both a fall in vascular resistance and an increase in arterial diameter of the common carotid artery. Isosorbide dinitrate increased markedly the arterial diameter but did not change vascular resistance. Nitrendipine decreased vascular resistance with no change in the arterial diameter. In the common carotid circulation of patients with essential hypertension, vasodilating drugs may either dilate small arteries (nitrendipine), large arteries (isosorbide dinitrate), or both (captopril).

Administration, Oral↗

PubMed1986

Effects of beta-adrenergic blockade on the arterial vasculature in essential hypertension.

The effect of beta-blockade was studied in 3 different kinds of human hypertension: borderline, sustained and isolated systolic hypertension. Young patients with borderline hypertension had a similar decrease in cardiac output with both nonselective and selective beta-blockade. Only nonselective beta-blockade decreased brachial artery blood flow and increased forearm vascular resistance. In patients with sustained essential hypertension, chronic administration of 2 nonselective beta-blockers, propranolol and pindolol, caused a similar significant decrease in blood pressure with different effects on forearm circulation. Pindolol produced a significant vasodilation of both large and small arteries of the forearm while propranolol did not. In patients with isolated systolic hypertension, short-term beta-adrenergic blockade with propranolol had different effects according to age. In younger patients, propranolol significantly decreased systolic pressure with a concomitant increase in rapid ventricular ejection. In older patients, a lack of systolic pressure reduction was observed with an increase in total peripheral resistance and a decrease in systemic arterial compliance. The results suggested that beta-adrenergic blockade in hypertension may affect blood vessels with different effects, according to age, to the characteristics of hypertension and to the specific properties of the beta-blocking agent. The vascular effects involve not only resistive vessels but also large arteries.

Adrenergic beta-Antagonists↗

PubMed1986

Isosorbide dinitrate: relationship between pharmacokinetics and brachial artery hemodynamics in essential hypertension.

Pharmacokinetics of isosorbide dinitrate (ISDN) and brachial arterial hemodynamics have been studied in 15 patients with sustained essential hypertension. The hemodynamic study was performed by using a pulsed Doppler device enabling evaluation of the diameter of the brachial artery with an error of less than 10%. After intravenous administration until plateau concentrations were reached, the ISDN infusion was stopped in order to study the disappearance curve of the drug and the pharmacokinetic parameters. ISDN caused a significant decrease in systolic pressure, a significant increase in arterial diameter, and no change in heart rate. Brachial hemodynamics were not correlated with the plasma concentration in the steady state or the area under the disappearance curve. In contrast, the changes in arterial diameter during perfusion were significantly correlated with the apparent distribution volume, a finding that might indirectly reflect the affinity of ISDN for vascular tissues.

Adult↗

PubMed1986

Captopril and common carotid blood flow in patients with essential hypertension--a review.

The haemodynamic pattern of the common carotid artery was studied before and after administration of captopril isosorbide dinitrate and nitrendipine, in men with sustained essential hypertension. Pulsed Doppler methods were used. Captopril produced both a fall in vascular resistance and an increase in the arterial diameter of the common carotid artery. Thus, in the common carotid artery circulation of patients with essential hypertension only captopril dilated both small and large arteries.

Captopril↗

PubMed1985

Cardiac hypertrophy and arterial distensibility in essential hypertension.

Echocardiographic determinations, left ventricular mass-volume ratio (M/V), left ventricular end-systolic stress (ESS), carotidofemoral pulse wave velocity (PWV), and brachial artery compliance (BAC), deduced from pulsed Doppler measurements and from the Bramwell-Hill equation, were evaluated in 20 patients with sustained essential hypertension in comparison with 20 control subjects of the same age and sex. In hypertensive patients, M/V ratio, ESS, and PWV were significantly increased while BAC was reduced. In the overall population, ESS was directly correlated with PWV (r = 0.73), and M/V ratio was significantly correlated with PWV (r = 0.60), BAC (r = -0.70), and systolic arterial pressure (r = 0.71). No comparable results were observed with diastolic arterial pressure. PWV was unchanged after cadralazine, a dihydralazine-like substance, and was decreased with the same blood pressure reduction following nitrendipine, a new calcium-blocking agent. These results suggest that: (1) the distensibility of large arteries plays an important role in the maintenance of cardiac hypertrophy in hypertension, and (2) antihypertensive drugs may act differently on arterial distensibility with possible consequences on ESS and reversion of left ventricular hypertrophy.

Adult↗

PubMed1985

Blood pressure in the 'low-pressure system' and cardiac performance in essential hypertension.

Determinations of central venous pressure, cardiac haemodynamics and rapid volume expansion using iso-oncotic dextran were made in 49 men with sustained, uncomplicated essential hypertension and compared with those in 27 normotensive subjects of the same age and sex. In the hypertensives, central venous pressure was significantly increased in basal conditions while the cardiac index was normal and total blood volume was reduced. There was a positive and significant correlation of central venous pressure with age, arterial pressure and pulmonary wedge pressure. After rapid volume expansion, the slope of the curve relating cardiac output to central venous pressure was within the normal range, while the slope of the curve relating blood volume to central venous pressure was significantly reduced. The study provided evidence that in hypertensives: central venous pressure as well as arterial pressure is increased, the elevated central venous pressure is not due to an alteration in the cardiac 'pump function' or to hypervolaemia but rather to a decrease in the compliance of the venous bed or the left ventricle or both, and the strong correlation with age of the venous disturbances is similar to that found for the arterial side of the circulation.

Adult↗

PubMed1985

Effects of acute and chronic angiotensin-converting enzyme inhibition on large arteries in human hypertension.

The effects of angiotensin-converting enzyme inhibition on large arteries have been examined in uncomplicated essential hypertensive patients (grade 1-2 WHO). These effects were determined from (a) changes in arterial compliance as measured from the slope of the decline in arterial pressure during diastole and (b) alterations in diameter of the brachial artery and blood flow velocity within its lumen, as assessed by pulsed Doppler velocimetry. Both acute and chronic ACE inhibition were accompanied by a significant increase in arterial compliance and a dilation of the brachial artery. This response might be related to changes in plasma and/or intraarterial angiotensin and/or to changes in plasma potassium. Whatever their mechanism, the arterial dilatation and increase in compliance would improve the buffering and the conducting functions of the large arteries, and these in turn may, if persistent, prove beneficial in possibly preventing arterial complications of hypertension.

Angiotensin-Converting Enzyme Inhibitors↗

PubMed1985

Hemodynamic mechanisms of and therapeutic approach to systolic hypertension.

Using noninvasive measurements of arterial diameter, compliance, and distensibility permits the mechanisms of increased systolic pressure in hypertensive humans to be better understood. Reduced arterial compliance causing a disproportionate increase in systolic pressure is a characteristic feature not only of pure systolic hypertension in the elderly but also of sustained essential systolodiastolic hypertension, mainly in persons aged over 50 years. Antihypertensive drugs should improve the status of large vessels through an active effect on the tone of the vascular smooth muscle of large arteries, a field as yet poorly investigated in hypertensive humans.

Animals↗

PubMed1985

Vasodilatation of small and large arteries in hypertension.

In patients with essential hypertension, vasodilating antihypertensive drugs act differently on small and large arteries. For similar blood pressure reductions, the diameter of the brachial artery may be unchanged (alpha- and beta-blocking drugs), decreased (dihydralazine), or increased (nitrates, renin-angiotensin and calcium-entry inhibitors). Increase in blood flow is due preferentially to an increase in blood flow velocity and is caused additionally by an increase in the diameter of the large artery. Increase in arterial compliance is observed only with nitrates, calcium-entry, and renin-angiotensin inhibitors. It is concluded that blood pressure reduction due to arteriolar vasodilatation may have various effects on the conducting function and the buffering function of large arteries, a point of importance in the prognosis of hypertensive cardiovascular disease.

Arteries↗