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Biomedical subjects

M Safar

Publications and source records attributed to M Safar.

At least 145 records · Page 8Linked to original sources
PubMed1993

[Regional arterial hemodynamics and carotid circulation in essential arterial hypertension. Effect of nitrendipine in patients over 40 years of age].

Lesions of the arterial wall constitute one of the main complications of essential hypertension. The final objective of all antihypertensive drugs is to reduce the cardiovascular morbidity and mortality rates, but their short and medium term objectives must be to normalise blood pressure values and to correct the functional and structural abnormalities consecutive to arterial hypertension. In this double-blind drug versus placebo study conducted in 20 patients (14 men, 6 women) aged over 40, the effects of nitrendipine on regional arterial haemodynamics (aortic territory, upper limb, lower limb) and carotid circulation were evaluated. Nitrendipine was administered daily in doses of 20 mg during 1 month. After 4 weeks of treatment, the treated group showed a fall in blood pressure and an improvement in the pulse wave propagation (an index of arterial distensibility) in the carotido-femoral territory (11.4 +/- 1.7 vs 9.9 +/- 1.6 m/s; P < 0.01) and in the humero-radial territory (12.9 +/- 2.0 vs 11.6 +/- 2.1 m/s; P < 0.05); there was no change in the femoro-tibial territory (13.2 +/- 1.8 vs 12.5 +/- 1.7 m/s; NS). The haemodynamics of the common carotid artery showed no change in carotid diameter or blood velocity, and small lowering of local resistances (28.1 +/- 9.1 vs 24.6 +/- 4.9 mmHg.s.ml-1; P < 0.05). This study demonstrates that in patients older than 40 years a long-term treatment with nitrendipine lowers blood pressure, does not alter the common carotid flow and improves arterial distensibility. The arterial effects seem to vary according to the arterial territories considered.

Adult↗
PubMed1993

Positive correlation between the blood pressure and heart rate response to the cold pressor test and the environmental temperature in older hypertensives.

The aims of our study were to evaluate whether there is any relationship between the environmental temperature and the response to the cold pressor test and if this relationship is different in younger and older hypertensive patients. We studied 100 mild-to-moderate hypertensives, aged 21 to 75 years. In the > or = 45 years group (46 patients) a significant positive correlation between the environmental temperature and the heart rate and blood pressure response to the cold pressor test was found. The relative humidity was not correlated with the response to the cold pressor test, but multiplying the mean temperature and the mean relative humidity enhanced the correlations of the environmental temperature. An increase in the mean temperature for the 20 days before the cold pressor test (the best correlated period) by 10 degrees C correlated with increases in the systolic blood pressure response by 10.5 mm Hg (P = .0195), the diastolic blood pressure response by 8 mmHg (P = .0079), the mean blood pressure by 9 mmHg (P = .0058), and the heart rate response by 3.8 beats/min (P = .0134). In < 45 years patients no environmental relationship of the response to cold pressor test was found. A chronic exposure to low temperatures is correlated with higher blood pressure levels--as previously reported--and, in contrast (but only in elderly), with a lower blood pressure response to acute cold stress. Our findings confirm the higher meteorological dependence of hemodynamics in the elderly, and suggest that the research protocols using the cold pressor test should adjust the response for the previous environmental temperature.

Adult↗
PubMed1993

Isobaric compliance of the radial artery is increased in patients with essential hypertension.

OBJECTIVES: Hypertension is known to decrease arterial elasticity and systemic compliance. However, the arterial tree is not a homogeneous system, and whether a distal medium-sized artery such as the radial artery behaves like proximal arteries has not been determined. The aims of the present study were, first, to characterize non-invasively the mechanical properties of the radial artery through the determination of the pressure-diameter curve, the distensibility-pressure curve and the compliance-pressure curve, and, secondly, to compare untreated hypertensive patients with normotensive subjects. METHODS: A new high-precision echo-tracking device was developed which allows the diameter of peripheral arteries to be measured continuously. By relating the changes in internal diameter (cross-sectional changes) to those in blood pressure, the cross-sectional arterial compliance could be determined. PARTICIPANTS: Seventy-eight untreated mild or moderate essential hypertensive patients aged 24-78 years were compared with 44 normotensive subjects aged 22-81 years. In order to increase the database and provide independent assessments of the variables examined, the cross-sectional study was performed independently using a standardized procedure in three different research centres. RESULTS: The major finding was that diameter, distensibility and compliance of the radial artery of hypertensive patients were not significantly different from those of normotensive controls when the two populations were studied at their mean arterial pressure. Furthermore, when the two populations were compared for the same level of blood pressure, using distensibility--and compliance--pressure curves, it was clear that isobaric distensibility and compliance of hypertensives were not significantly lower than those of normotensives, being either unchanged or higher. CONCLUSIONS: These findings are in contrast with the well-known decrease in compliance of proximal large arteries due to hypertension. Whether such a difference between proximal large arteries and distal medium-sized arteries may be related to the structural vascular changes observed with long-standing hypertension is still difficult to analyse in humans, and requires further investigation.

Adult↗
PubMed1993

Endogenous bradykinin activity in Dahl rats.

We assessed the participation of endogenous bradykinin (BK) on basal blood pressure (BP) regulation in anesthetized Dahl-sensitive (DS) and Dahl-resistant (DR) rats receiving different NaCl diets. Four groups of Dahl rats were studied after 5 weeks of high (H) = 7% or low (L) = 0.4% NaCl diet (DSH, n = 9; DSL, n = 11; DRH, n = 9; DRL, n = 10). Endogenous BK activity was assessed with a continuous intraarterial (i.a.) infusion of the specific BK antagonist (B4146 100 micrograms/kg/min) for 10 min. Sensitivity to exogenous BK was tested 30 min after the end of the infusions, with bolus intraarterial (i.a.) injections of BK (0.1, 0.5, 1, and 5 micrograms). DSH had a significantly higher (p < 0.0001) basal mean BP (MBP) as compared with the three other groups: DSH = 185 +/- 7 mm Hg (mean +/- SEM), DSL = 143 +/- 5 mm Hg, DRH = 132 +/- 10 mm Hg, and DRL = 134 +/- 6 mm Hg. BK antagonist infusion increased MBP by 13.2 +/- 1.5 mm Hg in DSL rats, by 6.8 +/- 1.6 mm Hg in DRL, by 4.7 +/- 1.6 mm Hg in DRH, and by 1.1 +/- 8 mm Hg in DSH. Statistical analysis showed that the high NaCl diet significantly decreased the response to the BK antagonist in DS (p < 0.001) but not in DR rats. MBP response to exogenous BK was similar in all groups. These results show that endogenous BK has a vasodepressor effect on DS rats fed a low NaCl diet. This effect is suppressed after a high-salt diet.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1993

Effects of clonidine on plasma catecholamines and neuropeptide Y in hypertensive patients at rest and during stress.

Neuropeptide Y (NPY), a potent vasoconstrictor agent reported to be released, in addition to norepinephrine (NE), by sympathetic nerve endings during stress, may contribute to the pressor response to various stimuli. The objectives of this study were to determine (a) whether plasma NPY concentrations are altered during different types of stress (cold pressor test, mental stress, and active orthostatism) and (b) whether clonidine, via its central sympatholytic effect, affects the stress-induced blood pressure, NPY, and/or catecholamine changes. Eighteen untreated patients with mild essential or borderline hypertension participated in an acute randomized, double-blind, parallel study. The blood pressure and heart rate were recorded during three control periods, each followed by either a cold pressor test (CPT), a mental stress test (MS: mental arithmetic), or active orthostatism (AO), performed in a random order. Venous blood samples for catecholamines and NPY determination were taken at the end of each control and test period. This entire procedure was repeated after oral clonidine (150 micrograms) or placebo. Before treatment, a CPT, MS, or AO increased the blood pressure to the same extent. The stress-induced increase in plasma NE was greater during AO (+99 +/- 23%) than during CPT (+35 +/- 8%) and MS (+55 +/- 12%). The stress-induced increase in plasma epinephrine was only significant during MS (+142 +/- 69%). A small but significant increase in NPY (p < 0.05) was observed during AO only (+10 +/- 7%). Compared to placebo, clonidine significantly decreased the basal blood pressure and the pressor response to CPT, but did not change the pressor response to MS and AO.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

The vibratory pattern of ultrasonic files driven piezoelectrically.

The pattern of oscillation of a Piezon-Master 400 ultrasonic file driven by a piezoelectric transducer was studied in air and on water. In addition, the displacement amplitudes of the files were measured. The findings were compared with those observed with the Cavi-Endo unit reported in another study (Ahmad 1969). It was observed that the file vibrated such that a standing wave was formed on the file and it exhibited points of maximum deflection (antinode) and points of minimum deflection (node) with the largest deflection occurring at the apical end. This pattern of oscillation was similar to that exhibited by the Cavi-Endo file which employed a magnetostrictive transducer. However, the displacement amplitudes were very much higher than those exhibited by the Cavi-Endo. It is considered that the 120 degrees angle of the file holder inherent in the Piezon-Master 400 unit and the more effective power transmission with the piezoelectric transducer may have contributed to the large amplitudes.

Dental Cavity Preparation↗
PubMed1993

Hypocaloric diet and antihypertensive drug treatment. A randomized controlled clinical trial.

OBJECTIVE: To compare the amount of drug quantified by a score needed to control blood pressure in two groups of overweight hypertensive patients, receiving or not receiving a hypocaloric diet. DESIGN: Randomized controlled clinical trial. SETTING: Two hospital outpatient hypertension clinics. PATIENTS: Fifty-four subjects with a DBP between 95 and 110 mmHg and a weight > or = 110% of the ideal weight. INTERVENTION: Allocation to either drug treatment (DT) or hypocaloric diet (HD). In the HD group, after 2 months, an antihypertensive drug was administered to the subjects with a DBP > or = 90 mmHg, following the same scheme protocol as in the DT group. Subjects were followed during 10 months by a clinician only in the DT group and by a clinician and a dietician in the HD group. MAIN OUTCOME MEASURES: Score of treatment: hydrochlorothiazide 25 mg [score = 1] with, as needed to obtain a DBP < 90 mmHg, the addiction of enalapril 10 mg [score = 2], 20 mg [score = 3], and nifedipine 40 mg [score = 4]. RESULTS: At the end of the trial, 5 subjects were lost to follow-up in the HD group and 1 in the DT group (p > 0.05). Mean weight loss was 5.9 kg (sd = 1.2) in the HD and 2.3 kg (sd = 0.7) in the DT group (p = 0.02). Mean decrease in DBP was 18 mmHg (sd = 7) and 15 mmHg (sd = 8) in HD and DT groups respectively (p = 0.36). Mean DBP was 84 mmHg (sd = 7.8) in the HD group and 85 mmHg (sd = 7.2) in the DT group. In the HD group, 8 (38.1%) subjects had a DBP < 90 mmHg without any drug treatment. The mean drug treatment score was 0.86 (sd = 0.91) in the HD and 1.52 (0.70) in the DT group (p = 0.01). CONCLUSION: This study shows that in overweight hypertensives, the quantity of drug needed to achieve an acceptable level of BP is nearly reduced by 50% when an efficient hypocaloric diet is prescribed simultaneously.

Adult↗
PubMed1993

[Peripheral and central participation in hemodynamic effects of serotonin2 receptor stimulation].

The systemic and regional haemodynamic effects of DOI were investigated in the anaesthetized rat. DOI (1-300 micrograms/kg i.v.) increased mean arterial pressure (MAP), total peripheral resistance (TPR) and all regional vascular resistances studied (hindquarters, mesenteric and renal). DOI was more effective on renal vascular bed. Cardiac output (CO) and heart rate (HR) did not change. The effects of DOI were antagonized by LY 53857 (10 micrograms/kg i.v.) and spiperone (10 or 100 micrograms/kg i.v.), selective 5-HT2 receptor antagonists. Intracerebroventricular administration of DOI (100 micrograms/kg) increased MAP, TPR, regional vascular resistances and did not change HR and CO. Pretreatment with xylamidine (10 micrograms/kg i.v.), a selective peripheral 5-HT2 receptor antagonist, blocked i.v. and i.c.v. effects of DOI. These results suggest that: 1) the increase in MAP induced by the stimulation of 5-HT2 receptors is due to an increase in TPR. All regional vascular resistances participate in the increase of TPR. 2) Peripheral and central 5-HT2 receptors seem to be implicated in the control of regional vascular resistances.

Amphetamines↗
PubMed1992

[Effects of aging on arterial function in man].

The structure of arteries changes with age. Gradual disappearance of elastic fibres facilitates dilatation of the arterial lumen and increase in length of the vessels. Simultaneously, the arterial wall becomes thicker, but it is often difficult to distinguish the changes due to ageing from those caused by atherosclerosis. These structural alterations result in a greater rigidity of the arteries, which can now be evaluated by non-invasive segmental methods. This shows that ageing does not have the same functional effects on wide-caliber elastic arteries and on middle-sized muscular arteries. The increase of systolic arterial pressure observed in the elderly is a consequence of structural and functional changes in the arterial system.

Aged↗
PubMed1992

Acute changes in forearm haemodynamics produced by cigarette smoking in healthy normotensive non-smokers are not influenced by propranolol or pindolol.

The aim of the present study was to examine the effect of cigarette smoking in healthy non-smokers on blood pressure and forearm haemodynamics after acute oral administration of non-selective beta-adrenoceptor blockers with and without intrinsic sympathomimetic activity, viz. pindolol 15 mg and propranolol 80 mg. A preliminary study was done to compare cigarette smoking and sham smoking to evaluate the time-course of the haemodynamic effects of cigarette smoking. The second experiment was then carried out in the same six volunteers, according to a double-blind randomized placebo-controlled crossover design, to evaluate the possible effect of pre-treatment with beta-adrenoceptor blockers on blood pressure, heart rate and forearm haemodynamics (forearm blood flow, brachial artery diameter and brachio-radial pulse-wave velocity) measured at baseline, during smoking and every five minutes up to 1 h afterwards. No major difference from placebo in blood pressure or forearm haemodynamics was found and pre-treatment with beta-blockers did not prevent the acute vascular effects of cigarette smoking.

Adult↗
PubMed1992

Rilmenidine: a novel approach to first-line treatment of hypertension.

Rilmenidine (RIL) is a novel antihypertensive drug selectively acting at the sites of imidazoline receptors. Compared with diuretics, beta-blockers, Ca2+ antagonists and angiotensin converting enzyme inhibitors, the four major groups recommended by the US Joint National Committee as first-line antihypertensive drugs, RIL appears to meet the same criteria of efficacy, safety, and acceptability. Rilmenidine dose-dependently decreases blood pressure (BP), acting as a vasodilator by decreasing vascular resistance through inhibition of the adrenergic nervous system, even while the BP changes due to standing and exercise. In comparison with placebo, RIL significantly decreased BP. In double-blind comparative trials versus first-line diuretics and beta-blockers, RIL normalized BP in approximately 60% patients, showing a similar efficacy to other drugs. In contrast with hydrochlorothiazide, RIL decreased total cholesterol and did not change plasma potassium levels. No tachyphylaxis was observed during long-term treatment. Central side effects, which have contributed to the limitation of the use of alpha 2-agonists as second- or third-line therapy for hypertension, were significantly less frequent with RIL than with clonidine or methyldopa. Indeed, the incidence of dry mouth and drowsiness during double-blind comparative trials versus clonidine and methyldopa was significantly lower with RIL. This absence of central side-effects was confirmed in double-blind comparative trials versus hydrochlorothiazide and atenolol. In contrast with clonidine, no sodium retention or weight gain were observed during chronic treatment with RIL.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic alpha-Agonists↗
PubMed1992

Arterial effects of salt restriction in hypertensive patients. A 9-week, randomized, double-blind, crossover study.

OBJECTIVE: To investigate the hemodynamic effects of a moderately low-salt diet in a 9-week, randomized, double-blind, crossover study in 20 hypertensive, ambulatory patients. METHODS: All subjects followed a 9-week, low-salt diet. During this period, they received capsules containing either lactose or salt in 4-week treatment periods, separated by a 1-week washout period. Hemodynamic and biological parameters were evaluated on the day of randomization and at the end of weeks 4 and 9. We defined a low-sodium diet (LSD) as a salt-restriction period with lactose capsules, and a normal-sodium diet (NSD) as a salt-restriction period with capsular salt supplementation. RESULTS: Blood pressure was significantly lower during LSD compared with NSD. This fall in blood pressure was associated with a decrease in peripheral resistance in carotid and forearm circulation. Brachial artery diameter was larger during LSD whereas carotid artery diameter remained unchanged. The changes in brachial artery were: (1) not related to blood pressure changes; (2) positively related to age, and (3) negatively correlated with baseline intracellular sodium content. CONCLUSIONS: These results suggest that moderate low-salt restriction is capable of decreasing blood pressure and peripheral resistance in carotid and forearm circulation. The increase in brachial, but not carotid, artery diameter following salt restriction suggests a difference in salt dependence among different arteries.

Adult↗
PubMed1992

Mechanism of nitrate-induced improvement on arterial compliance depends on vascular territory.

The link between arterial caliber and distensibility has been studied extensively, with conflicting results. As have other researchers, we previously showed evidence of an increase in arterial diameter and a decrease in arterial stiffness with use of nitrates at the site of the brachial artery (BA) and the aorta. Whether these results would apply to other large superficial arteries remained to be established. In the present study, by means of an original pulsed ultrasound echo-tracking system based on Doppler shift, we measured internal diastolic diameter and stroke change in diameter of the common carotid artery (CCA), the femoral artery, and the BA in patients with essential hypertension and determined the acute effects of administration of isosorbide dinitrate (ISDN 20 mg). Twenty untreated hypertensive patients entered this randomized, placebo-controlled, double-blind, parallel study. No significant change occurred during placebo. During ISDN therapy, blood pressure (BP) decreased significantly; cross-sectional compliance increased at the site of the CCA, the BA, and the common femoral artery (CFA). The increase in cross-sectional compliance was mainly due to an increase in internal diameter for CCA and to an increase in distensibility coefficient (DC) for BA. The pattern of cross-sectional compliance was intermediate for CFA. During ISDN therapy, the augmentation index of the CCA distension waveform was significantly reduced, whereas no change occurred during placebo, suggesting a reduction in wave reflection by nitrates.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Arterial and antihypertensive effects of nitrendipine: a double-blind comparison versus placebo.

Arterial effects evaluated by carotid-femoral, brachial-radial, and femoral-tibial pulse wave velocity and antihypertensive effect evaluated by 24-h ambulatory blood pressure (BP) monitoring were measured in 17 hypertensive patients before and 24 h after once-daily nitrendipine (20 mg) administration. After a 15-day placebo period, a double-blind study of nitrendipine versus placebo was performed for 1 month. After nitrendipine dosing, BP measured by sphygmomanometer 24 h after the last drug intake showed a significant decrease as compared with the pretreatment period. Ambulatory BP mean values were also significantly decreased for systolic and diastolic BP (SBP, DBP). This decrease predominated during the day but was observed nocturnally only after 6 a.m. Twenty-four hours after the last tablet intake of nitrendipine, carotid-femoral and brachial-radial pulse wave velocities were significantly reduced, whereas femoral-tibial wave velocity was unchanged, indicating that markers of arterial rigidity might be substantially modified and that the modifications were partly unrelated to BP changes. The results provide evidence that in hypertensive subjects nitrendipine 20 mg given once daily for 1 month produces an arterial effect for 24 h, in association with BP reduction.

Adult↗
PubMed1992

Hemodynamic effects of carvedilol after acute oral administration in hypertensive and normal subjects.

Forearm hemodynamics using pulsed Doppler flowmetry were studied in nine healthy volunteers and 12 patients with mild-to-moderate hypertension before and after acute oral administration of the beta-blocking and vasodilating agent carvedilol. Both the 25- and the 50-mg dose produced a significant blood pressure reduction by comparison with placebo in normotensive and hypertensive subjects. Only the 50-mg dose caused a decrease in forearm vascular resistance in hypertensive subjects. The decrease disappeared after wrist occlusion. Although brachial artery diameter did not change, a significant decrease in tangential tension was observed. This study provides evidence that carvedilol produced arteriolar dilation within the forearm of hypertensive subjects in association with a decrease in brachial artery tangential tension.

Administration, Oral↗
PubMed1992

Increased systolic pressure in chronic uremia. Role of arterial wave reflections.

To assess the role of arterial wave reflections in the mechanism of systolic hypertension and altered pulsatile arterial dynamics in patients with end-stage renal disease (ESRD), 79 ESRD patients were compared with 73 age-matched control subjects with normal renal function and similar mean blood pressure. Wave reflections were investigated from the carotid pulse contour recorded by applanation tonometry using a Millar micromanometer-tipped probe. Wave reflections were quantified as the ratio (augmentation index, %) of the height of the late systolic peak to the total height of carotid pulse wave. Travel time of the reflected wave was timed from the foot of the pressure wave to the foot of the late systolic peak. Systolic and pulse pressure were increased in ESRD patients (p less than 0.001) and was not attributable to differences in left ventricular ejection pattern. The augmentation index was increased in ESRD patients (23.2 +/- 15.0 versus 9.8 +/- 15.6%; p less than 0.001) in association with a shorter travel time of reflected wave (109 +/- 24 versus 131 +/- 30 msec; p less than 0.001). Multiple regression analysis showed two principal factors associated (p less than 0.001) with the increase in augmentation index and shortened travel time of reflected wave: increased aortic pulse wave velocity and smaller stature with shorter body height in ESRD patients. The study points to the role of arterial wave reflections in the mechanisms producing alterations in pulsatile arterial dynamics in ESRD and is the first, through the mechanisms of early wave reflections, to show in humans that the increase in systolic and pulse pressures is associated with lesser body size.

Adult↗
PubMed1992

Effects of antihypertensive agents on carotid pulse contour in humans.

The aim of this study was to assess the influence of antihypertensive agents on arterial wave reflections (AWR) and carotid pulse pressure (PP) in humans. Twenty patients with hypertension (predominantly systolic) were studied. After one month of placebo therapy they were randomly assigned to atenolol (At) 50 mg/day or to nitrendipine (Ni) 40 mg/day. Carotid pressure waveform was recorded noninvasively by applanation tonometry using a Millar micromanometer-tipped probe. Arterial wave reflections were quantified as the ratio of the height of the late systolic peak (delta P) to the total height of carotid pulse pressure wave as an augmentation index (delta P/PP). Travel time of the reflected wave (delta tp) was timed from the foot of the pressure wave to the foot of the late systolic peak. Atenolol and Ni were equally effective in reducing sphygmomanometric brachial artery blood pressure (BP). Whereas At (p < 0.05) and Ni (p < 0.01) reduced the carotid PP, Ni (p < 0.01) but not At significantly reduced delta P/PP. Both agents increased the delta tp (p < 0.01) and decreased aortic PWV (p < 0.01). Nitrendipine was associated with a decrease in left ventricular ejection time (LVET) (p < 0.01), while At increased heart period (p < 0.01) and LVET. The LVET/delta tp ratio decreased after Ni (from 3.25 +/- 0.77 to 2.42 +/- 0.73; p < 0.01) but did not change after At. The study shows, that for the same effect on peripheral BP, Ni has a more pronounced effect on pressure wave in central arteries, resulting from an improvement in the timing between the ventricular ejection and AWRs.

Antihypertensive Agents↗