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Biomedical subjects

J Levenson

Publications and source records attributed to J Levenson.

At least 181 records · Page 10Linked to original sources
PubMed1985

[Central and peripheral hemodynamic effects of nifedipine administered orally and sublingually in essential arterial hypertension].

The central and peripheral haemodynamic effects of the administration of 10 mg nifedipine sublingually in 6 patients with essential hypertension were compared with those observed after the administration of one 20 mg slow release tablet of nifedipine in 7 other hypertensive patients of the same age. The circulatory effects in the forearm were studied by pulsed Doppler velocimetry which allowed simultaneous measurement of the diameter of the brachial artery and of the velocity of blood flow. Both forms of administration significantly reduced the blood pressure by a significant reduction in total peripheral resistance. This reduction in total peripheral resistance was more significant (p less than 0.001 vs p less than 0.01) and more rapid with sublingual administration and was associated with a greater increase in heart rate and cardiac output. Both forms of administration induced an increase in brachial arterial blood flow due to a simultaneous increase in vessel calibre and velocity of blood flow. The results of this study show that both forms of administration act directly on the vessel wall of the arterioles and great arteries leading to a fall in blood pressure associated with an increase in peripheral blood flow. Sublingual nifedipine would seem to be the drug of choice for the treatment of hypertensive crises, whilst the slow release preparation with its lesser baroreflex stimulation would appear better suited for the long-germ treatment of essential hypertension.

Administration, Oral↗
PubMed1985

[Effect of arterial hypertension on pulse wave velocity and the diameter and compliance of the brachial artery in man].

The non invasive investigation of the brachial artery was performed in 51 mild to moderate essential hypertensive patients and 23 normal subjects of similar age. It included quantitative evaluation of arterial diameter (pulsed Doppler velocimetry), pulse wave velocity (strain gauge mechanography) and arterial compliance deduced from the former indices. Hypertensive patients exhibited higher pulse wave velocity (Pw 0.001) and arterial diameter (p less than 0.01) than normal controls. The strong correlation found in normal subjects between pulse wave velocity and the product of age and diastolic pressure (r = 0.88, p less than 0.001) was used as a nomogram for the analysis of those hypertensive arterial changes. Accordingly the projection of patients on this nomogram enables to distinguish two groups according to that pulse wave velocity was inside (Group 1) (37 patients) or above (Group II) (34 patients) the upper limit of the nomogram. The comparison of these two groups of hypertensive patients showed that despite a similar level of age and pressure, arterial compliance was lower and pulse pressure higher in Group II than in Group I. These results demonstrate that early alterations of brachial artery occur in hypertension: these arterial changes can be attributed in most of the patient to the exclusive effect of aging and pressure elevation; however, in some patients additional degenerative process, perhaps atherosclerotic in nature, is responsible for profound decrease in arterial compliance and increase in pulse pressure so that such patients may appear as especially predisposed to systolic hypertension and degenerative arterial complications.

Adult↗
PubMed1984

Peripheral hemodynamic effects of short-term nadolol administration in essential hypertension.

A study of forearm arterial and venous hemodynamics by pulsed Doppler velocimetry and plethysmography was performed in 21 patients with essential hypertension, aged 16 to 54 years, before and after short-term nadolol administration at a dose of 0.05 mg/kg. Because of a large intersubject variability in the responses of the hemodynamic parameters to nadolol, an unconventional statistic approach was used to divide the overall population of patients into two homogeneous groups. The first included nine patients (group 1) and the second 12 patients (group 2). In patients of group 1, nadolol significantly decreased the systolic blood pressure (p less than 0.001), venous tone (p less than 0.01), and brachial artery flow (p less than 0.05). In patients of group 2, nadolol did not affect any forearm parameters. Each group of patients was compared to an age- and pressure-matched group of patients receiving propranolol at equiblocking doses. Contrary to nadolol, propranolol was found to increase significantly the forearm vascular resistance in patients of groups 1 and 2 (90 +/- 19%, p less than 0.001; 63 +/- 10%, p less than 0.001, respectively). Thus the hemodynamic beta-blocking effects of nadolol in the forearm were less marked than those of propranolol, suggesting that the effects of acute beta blockade by nadolol could be offset by other effects, such as a peripheral partial-agonist effect.

Adolescent↗
PubMed1984

Post-synaptic alpha-blockade and brachial artery compliance in essential hypertension.

Central (six patients) and brachial (12 patients) haemodynamics were studied in men with sustained essential hypertension before and after intravenous administration of an alpha post-synaptic adrenergic blocking drug, urapidil. Brachial arterial compliance was evaluated non-invasively from the simultaneous measurement of pulse wave velocity and arterial diameter. In basal conditions, arterial compliance was reduced in hypertensives. Urapidil caused a significant drop in blood pressure, due to a significant decrease in total peripheral resistance with no change in cardiac output and heart rate. Brachial arterial diameter and compliance did not change significantly. The results show that the decreased arterial compliance in hypertensive patients was not due exclusively to the elevation of blood pressure or to a predominant activation of the autonomic nervous system, or both. Such observations suggest that, in men with sustained essential hypertension, the decreased compliance was probably related to structural alterations of large arteries.

Blood Flow Velocity↗
PubMed1984

Large arteries in hypertension: acute effects of a new calcium entry blocker, nitrendipine.

Acute effects of a new calcium entry blocker, nitrendipine, on large arteries of the forearm were studied by using arterial pulse strain gauge mecanography and pulsed Doppler velocimetry of the brachial artery in 13 mild to moderate essential hypertensive patients. Ninety minutes after nitrendipine ingestion, patients exhibited significant decreases in blood pressure without changes in heart rate; increases in brachial artery diameter and decreases in brachial to radial pulse wave velocity; increases in arterial compliance and decreases in characteristic impedance; and increases in brachial artery blood velocity and flow and decreases in forearm vascular resistance. Lastly, amplitude of pulse pressure was decreased by nitrendipine and negatively correlated to the level of arterial compliance. These results suggest that nitrendipine exerts a direct benefit effect on the hypertensive large arteries whose two main consequences are a decrease in pulsatility of arterial pressure and an increase in arterial flow.

Adult↗
PubMed1984

Adipose tissue cellularity and hemodynamic indexes in obese patients with hypertension.

Fat-cell weight, fat-cell number, and hemodynamic indexes were determined in 25 obese men with sustained elevation of BP. Fat-cell weight (and not fat-cell number) was positively correlated with overweight (r = .51) and mean arterial pressure (MAP) (r = .57) in basal conditions. After body weight reduction, BP decreased significantly through a decrease in cardiac index due to a predominant decrease in heart rate. Simultaneously, fat-cell weight decreased significantly. The ratio between the change in BP and the change in body weight, ie, the ability to decrease pressure per unit weight loss, was positively related to the level of initial BP (r = .80) and reached a plateau above 120 mm Hg of the initial MAP. We suggest that, in patients with obesity and hypertension, high BP is associated with hypertrophic obesity, and after body weight reduction, the simultaneous decrease in BP, heart rate, and fat-cell weight could be mediated by neurogenic mechanisms.

Adipose Tissue↗
PubMed1983

Thromboxane B2 in borderline and essential hypertensive patients.

Thromboxane B2 (TxB2) was measured in the venous and arterial plasma and in the urine of 15 borderline and 15 sustained essential hypertensive patients, and in the plasma and urine of 12 control normotensive age-matched subjects. Plasma and urine thromboxane B2 were significantly higher in both the borderline and sustained hypertensives than in the control normotensives. There was a significant positive correlation between urinary (i.e. renal)TxB2 excretion and the glomerular filtration rate, and between urinary TxB2 excretion and sodium excretion in the hypertensive but not in the normotensive subjects. Thromboxane A2 participates in pressure natriuresis.

Adolescent↗
PubMed1983

Comparative effects of beta-adrenergic blockade in systolic hypertension according to age.

Hemodynamic variables were measured in 34 patients with isolated systolic hypertension before and after acute administration of propranolol. The patients were separated into two groups, those younger than and those older than 45 years of age, respectively. After drug administration, systolic pressure decreased significantly (P less than 0.001) in younger subjects with a concomitant increase in rapid ejection time (P less than 0.001). In the older patients, cardiac and peripheral factors determining systolic pressure were each altered after beta-adrenergic blockade. The most striking result was the reduction in systemic arterial compliance (P less than 0.01) probably due to unmasked alpha-adrenergic vasoconstriction. This arterial effect explains the lack of systolic pressure reduction despite a decrease in cardiac performance.

Adrenergic beta-Antagonists↗
PubMed1982

[Pharmacokinetics of isosorbide dinitrate administered by intravenous infusion to hypertensive patients (author's transl)].

The pharmacokinetics of intravenous isosorbide dinitrate was investigated in 11 patients with labile hypertension and with normal renal and hepatic functions. The mode of administration (constant rate infusion without loading dose) was chosen in order to minimize side-effects and to approximate clinical conditions. Isosorbide dinitrate levels were measured by electron-capture gas chromatography. The volume of distribution during steady state (Vd beta = 318 +/- 117 I) and the elimination half-life (t1/2 beta = 64.8 +/- 30.5 min) were similar to those found after perlingual and oral administration. Systemic clearance (Cls = 3.80 +/- 1.48 I/min) was high for a drug given intravenously, presumably because of active hepatic extraction, intensive pre-systemic degradation and very active extra-hepatic metabolism. These findings should be compared with the considerable inter-individual variations observed in theoretical plasma concentrations during steady state and with the presence of two pharmacokinetic models (one -- and two -- compartments) in the patients under study. Comparison of the results obtained by the intravenous route with previously published results after perlingual and oral administration indicates the following bioavailability ratios: perlingual/i.v. = 31%, oral/i.v. = 20%, and oral/perlingual = 63%.

Female↗
PubMed1982

Effects of captopril on prostaglandin and natriuresis in patients with essential hypertension.

The antihypertensive, renal and hormonal effects of captopril were studied in 10 patients with essential hypertension. Captopril significantly decreased arterial blood pressure with a concomitant increase in glomerular filtration rate, natriuresis and kaliuresis and a significant selective increase in urinary (renal) prostaglandin E2; other plasma and urinary prostaglandin (F2 alpha, 6-keto-prostaglandin F1 alpha; thromboxane B2) were not significantly changed. The urinary prostaglandin E2 increase was observed even in patients with pretreatment subnormal prostaglandin E2 excretion. Increases in urinary prostaglandin E2 were significantly positively correlated with increases in urinary sodium concentration. It is concluded that the antihypertensive effect of captopril is mediated, at least partially, by prostaglandin E2 release from renal and extrarenal tissues. Captopril enhances natriuresis at a lower perfusion pressure.

Blood Pressure↗
PubMed1982

[Systolic arterial hypertension: demonstration and mechanism in obliterating arteriopathy of the lower extremities].

Hemodynamic parameters were measured in 24 patients with arteriosclerosis obliterans of the lower limbs, in comparison with 16 normal subjects of same age. Systemic arterial compliance was estimated from a simple visco-elastic model. In patients with arteriosclerosis obliterans, systolic pressure was significantly increased (P less than 0.001) while diastolic pressure remained within normal ranges. Arterial compliance was reduced (P less than 0.01) and was negatively correlated with systolic pressure (r = -0.72). Intravenous administration of nitroglycerin significantly decreased systolic pressure (P less than 0.05) and increased arterial compliance (P less than 0.01) without any change in mean arterial pressure. This study provided evidence that, in patients with arteriosclerosis obliterans of the lower limbs, the reduced systemic arterial compliance contributes in the increase in systolic pressure.

Arterial Occlusive Diseases↗
PubMed1982

[Comparative hemodynamic effects of 2 vasodilators: dihydralazine and diltiazem in permanent essential arterial hypertension].

Cardiac hemodynamic and diameter, blood flow velocity, volumic flow of the brachial artery measured by pulsed Doppler, were studied before and after diltiazem administration in comparison with dihydralazine in hypertensive patients. After diltiazem administration, blood pressure and total peripheral resistance significantly decreased (P less than 0.001) while cardiac index and heart rate increased (P less than 0.01). After 25 minutes perfusion cardiac output and heart rate returned toward control values, while blood pressure and total peripheral resistance remained decreased. The result contrasted with those observed after dihydralazine, which induced an increase in cardiac index and heart rate. The caliber of the brachial artery decreased significantly (P less than 0.001) after dihydralazine and increased after diltiazem (P less than 0.01). This study shows that 1). The antihypertensive effect of diltiazem was due to a fall in total peripheral resistance associated with a transient baroreflex mediated tachycardia, and 2) diltiazem dilated also large arteries.

Adult↗
PubMed1980

[Anti-hypertensive action of Captopril. Hemodynamic study (author's transl)].

Hemodynamic parameters were studied before and after administration of SQ 14 225, an orally active converting enzyme inhibitor, in 6 sustained essential hypertensive patients. Blood pressure and total peripheral resistance significantly decreased while cardiac output and heart rate remained unchanged. Systolic time intervals and plasma volume were not modified. No correlation was observed between the basal value of plasma renin activity and the decrease in blood pressure. The study demonstrated the vasodilatator effect of SQ 14 225 and questionned the role of the renin-angiotensin system in the mechanism of the pressure decrease.

Adult↗
PubMed1978

[Essential hypertension: long term haemodynamic effects of a diuretic combination (cyclothiazide-triamterene) (author's transl)].

The long terme hemodynamic effect of cyclothiazide 3 mg-triamterene 150 mg was studied in 10 patients with permanent essential hypertension. Diuretic therapy induced a significant fall in blood pressure (p less than 0.001) and total peripheral resistance (p less than 0.01), without significant change in cardiac index or blood volume. The result suggests that adaptative mechanisms of the circulatory system determine the decrease of blood pressure, independently of the pharmacological effect of the drug.

Adult↗