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Biomedical subjects

M Safar

Publications and source records attributed to M Safar.

At least 163 records · Page 9Linked to original sources
PubMed1992

[Absence of labetalol interference on urine metanephrine determination in hypertensive patients].

The dosage of urinary catecholamines and their metabolites is a main element of diagnosis in the research of a pheochromocytoma in patients with high blood pressure. The literature reports high values of these compounds in patients treated with labetalol (an alpha/beta-blocker). An analytical interference has been evoked to explain these misleading results, which have not been observed with other beta-blockers. The goal of this work was to look for this eventual analytical interference in the dosage of urinary metanephrine by reversed phase liquid chromatography coupled with electrochemical detection, in patients with high blood pressure. Eighteen hypertensive patients, 52 +/- 14 years old, were included in the study. In 8 patients, a dosage of metanephrine, normetanephrine and creatinine on a 24 hours urine sample was performed before (D1) and 24 hours after (D3) the prescription of labetalol (200 mg twice a day). In the other group, labetalol was not prescribed but dosage was made in the same conditions. Urinary excretion of these compounds (metanephrine+normetanephrine) divided by urinary creatinine was not modified in the treated group (0.16 +/- 0.08 vs 0.14 +/- 0.04), nor in the reference group (0.17 +/- 0.08 vs 0.17 +/- 0.08). This study shows that administration of labetalol in patients with essential hypertension does not interfere with urinary metanephrine and normetanephrine determination after 48 hours of treatment. This implies that research for a pheochromocytoma is possible in patients with hypertension and receiving labetalol, by using reversed phase liquid chromatography coupled with an electrochemical detector for the dosage of urinary metanephrine and normetanephrine.

Adrenal Gland Neoplasms↗
PubMed1992

[Nitrate derivatives and compliance of large arteries].

Nitrate derivatives are useful drugs because of their direct vasodilating properties even in the presence of abnormal endothelial function. This is particularly true of the great arteries, explaining the improvement in arterial compliance regularly observed. The corollary of this effect is an improvement in systolic blood pressure and arterial pulsatility with little change in mean arterial pressure. The improved systolic but unchanged mean blood pressures reduce myocardial systolic stress and ensure relative preservation of coronary perfusion pressure which is particularly important in the treatment of systolic hypertension of the elderly.

Blood Pressure↗
PubMed1992

[Non-invasive methods in the study of the elastic properties of the thoracic aorta. Effect of isosorbide dinitrate].

The role of the great arteries is to distribute and stock blood. Pulsatile discontinuous flow is transformed to a continuous flow system. The elastic properties of the aorta play a major role in these functions. It is generally agreed that changes in these elastic properties may lead to the development of left ventricular hypertrophy. The evaluation of the aorta has, until recently, depended on invasive hemodynamic and angiographic techniques. In addition, the measurement of pulse wave velocity, though useful, is a global and only an approximate method. Transoesophageal echocardiography (TEE) enables accurate measurement of the aortic diameter and its systolo-diastolic variations. The accuracy of these measurements has been validated in vitro and the reproducibility is much better than with previously used techniques. Previous studies have shown an improvement of the elastic properties of the great arteries with nitrate derivatives. In recent studies using TEE, isosorbide dinitrate caused dilatation of the descending thoracic aorta and thereby improved its elastic properties. The development of tonometry techniques in our department has resulted in the finding of excellent correlations between carotid and aortic pulse pressures measured non-invasively. The association of TEE and tonometry thereby provides a direct approach to the evaluation of aortic compliance. It has then become possible to study the effects of nitrate derivatives on the aortic compliance of elderly patients in whom it is the most reduced.

Aorta, Thoracic↗
PubMed1992

Potential role of the renal tubule in fixing the level of plasma sulfoconjugated catecholamines in the dog.

Plasma levels of sulfoconjugated catecholamines in human subjects and in dogs are usually much higher than those of native amines. Their origins and the mechanism(s) involved in fixing their plasma concentrations are not well known; however, several lines of clinical evidences indicate a major role for the kidney. Thus this study was undertaken to measure the renal fractional excretion--used as an overall index of kidney mechanisms involved in the handling of catecholamines and their sulfoconjugates in the dog--and to look for any possible relationships between plasma concentration and urinary excretion. This was carried out in 36 anesthetized hydropenic mongrel dogs. The mean values of the renal fractional excretion of sulfoconjugated dopamine, norepinephrine, and epinephrine were shown to be statistically greater than 100%, suggesting a predominant secretion by the renal tubules of hydropenic dogs. Statistically significant correlations between plasma concentration and urinary excretion of sulfoconjugates--independent of blood pressure, cardiac output, clearance of para-aminohippuric acid, glomerular filtration rate, and sodium excretion are reported. Thus any change in the tubular handling of sulfoconjugates is likely to have a direct consequence in the fixation of their plasma concentrations.

Animals↗
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

Central hypotensive effects of nicardipine in conscious freely moving spontaneously hypertensive rat.

The central cardiovascular effects of the calcium channel blocker nicardipine was studied in conscious freely moving normotensive Wistar Kyoto rats (WKY) and spontaneously hypertensive rats (SHR). Nicardipine was administered in a 1.5 microliters volume into the lateral ventricle of the brain (i.c.v.) or intravenously (i.v.). The injection of vehicle alone did not significantly change mean arterial pressure (MAP) or heart rate (HR). Nicardipine (10, 30, 100 and 300 micrograms/kg) intravenously administered, dose-dependently decreased MAP and increased HR in WKY and SHR. However, when administered i.c.v., nicardipine (10 micrograms/kg) increased MAP and HR in WKY and decreased MAP without any significant change in HR in SHR. These results are consistent with previous work reporting an exaggerated hypotensive response to i.c.v. administration of dihydropyridine calcium channel blockers in anesthetized SHR as compared to WKY. They suggest that a 1,4-dihydropyridine-sensitive pressor system is present in the SHR but not in the WKY.

Animals↗
PubMed1991

Effects of ramipril on arterial hemodynamics.

The acute and chronic arterial effects of the angiotensin-converting enzyme (ACE) inhibitor ramipril were studied in hypertensive patients. Hemodynamic and biological parameters were measured 3 h after the first dose of 5 mg of ramipril, and then again after 4 weeks of treatment, 3 and 24 h after drug administration. Brachial and carotid artery hemodynamics were evaluated using a two-dimensional pulsed Doppler system. Arterial distensibility was studied noninvasively in three arterial segments (carotidofemoral, brachioradial, and femorotibial) by evaluating the pulse wave velocity. Ramipril lowered the blood pressure significantly after acute and 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 arterial segments studied did not show any significant changes. Our results suggest that the long-lasting arterial effects of the ACE inhibitor ramipril are partly pressure independent and are related to effects on arterial tone that may reduce the cardiovascular abnormalities associated with hypertension.

Angiotensin II↗
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↗
PubMed1991

[Study of flow-dependent vasodilation of the femoral artery in hypertensive and normal subjects].

Flow dependent vasodilation of brachial artery is not significantly different in hypertensives as compared to normotensives. Since, in vitro, changes in vasomotor tone of large arteries in response to endothelial stimulation may differ depending on the territory, we re-examined phenomenon of flow-dependent vasodilation at the level of the femoral artery in 10 normotensives (NT) and 12 age matched (45 +/- 9 vs 43 +/- 4 yrs) hypertensives (HT). Systolo-diastolic variations of femoral artery diameter (D) were recorded using an original echo-tracking system based on doppler shift while blood flow velocity was measured at the same level using a bidimensional pulsed doppler system (V). A 10 min period of leg ischemia did not induce any significant change in D and V in each group but decreased foot skin blood flow (laser doppler). This decrease occurred to the same extent in NT and HT. During reactive hyperemia following release of the pneumatic cuff, V increased (from 2.1 +/- 0.3 to 12.5 +/- 2.4 cm/s in NT) and returned to control level at the 3rd min. Diastolic diameter (Dd) increased (max: 2nd min) in NT (9.3 +/- 0.8 vs 8.8 +/- 0.9 mm; p less than 0.001) and in HT (9.5 +/- 1.2 vs 8.4 +/- 1.2 mm; p less than 0.01). Dd increased to a greater extent in HT than in NT while reactive hyperemia (laser doppler) did not differ. Thus, a non-invasive method is able to demonstrate a flow-dependent vasodilation at the level of the femoral artery.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

[Visco-elastic properties of common carotid artery in treated hypertension].

It is now possible to measure clinically by a non-invasive method systolo-diastolic variations of the internal diameter of large arteries over 4 to 10 cardiac cycles with an original vascular echo-tracking device using Doppler shift. By the means of a transversal study of healthy subjects and patients followed up in the hypertension clinique, the authors set out to determine whether long-term non-specific antihypertensive treatment could, by correcting the blood pressure, also normalise the vascular changes encountered in hypertension. This study compared 46 normotensive subjects (Group I), 25 essential hypertensive patients with normal blood pressure recordings after at least 3 months' treatment (Group II) and 56 untreated essential hypertensive patients of the same average age (range 24 to 78 years). The common carotid artery was chosen for study of its geometry (internal diastolic diameter: Dd) and function (relative systolic expansion Ds-Dd/Dd; Perterson's elastic modulus; cross sectional compliance). The arterial diameter increased significantly with age in all three patients groups. In patients under 60 years of age, the diameter, corrected for age and sex, was significantly greater in Group II than in Group I, and similar in Groups II and III. This suggests that in spite of correcting blood pressure by long-term therapy (4.1 +/- 4.1 years), the internal diameter of a large artery such as the common carotid artery remains increased, which is in favour of the persistence of structural arterial changes rather than a prolonged vasodilator effect of the antihypertensive agents used.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

[Transesophageal echography in the investigation of left atrial ball thrombi. Apropos of a case of migration of a left atrial thrombus].

The authors report the case of a pediculated left atrial ball thrombus whose embolisation and ejection through the aortic valve was recorded during transesophageal echocardiography. The value and risks of transesophageal echocardiography for the diagnosis of left atrial masses are reviewed in the light of this case and a review of the literature. The prognosis and therapeutic implications of a left atrial ball thrombus are also described.

Aged↗