Biomedical subjects

M Safar

Publications and source records attributed to M Safar.

At least 199 records · Page 11Linked to original sources

PubMed1989

Arterial compliance in uraemia.

Aortic and brachial pulse wave velocity were measured in 26 haemodialysis patients in order to assess the effect of uraemic waste-product retention on arterial compliance. Dialysis with a 'low-calcium' dialysate (1.50 mmol/l) did not change the pulse wave velocity, but dialysis with a 'high-calcium' dialysate (1.75 mmol/l) induced a significant increase in both aortic and brachial pulse wave velocity. The results indicate that (1) waste-product retention is not responsible for the increased arterial pulse wave velocity observed in uraemic patients and (2) the increase in serum ionized calcium decreases arterial compliance.

Arteries↗

PubMed1989

Endothelin has potent direct inotropic and chronotropic effects in cultured heart cells.

To determine whether endothelin, a highly potent vasoconstrictor peptide, may affect cardiac myocyte contractility directly, we studied the effects of synthetic porcine endothelin-1 in cultured chick embryo ventricular cells. Endothelin-1 had a potent chronotropic effect (EC50 0.17 nmol/l) in spontaneously beating cells. The increase in the beating rate was accompanied by a frequency-dependent decrease in the amplitude of contraction. In electrically driven cells (1 Hz), endothelin-1 increased the amplitude of contraction dose-dependently, with an EC50 of 0.3 nmol/l, smaller than that of the calcium channel blocker BAY K 8644 (EC50 3.3 nmol/l), and with an efficacy close to that of BAY K 8644 and isoproterenol. Nicardipine (100 nmol/l) shifted to the right, by two orders of magnitude, the dose-response curve of endothelin-1 for inotropism. These results indicate that endothelin-1 is one of the most potent inotropic agents in cultured cardiac myocytes, and suggest that this effect involves, at least in part, a calcium ion influx through voltage-sensitive calcium channels.

Animals↗

PubMed1989

Early arterial modifications in young patients with borderline hypertension.

Pulse wave velocity, used as an indicator of arterial distensibility, was recorded in 123 young male subjects, 63 untreated patients with borderline hypertension and 60 control subjects. The measurement was made with a continuous Doppler unit coupled to an ECG. In both groups mean age was similar, but mean arterial pressure was increased in borderline hypertensive compared with control patients. In comparison with controls, borderline hypertensives showed an increased pulse wave velocity. A significant correlation was observed between mean arterial pressure and pulse wave velocity in both populations, but the two regression lines were significantly different (covariance analysis). This result suggests that pulse wave velocity modifications in borderline hypertensives are not solely due to the elevated pressure, but also reflect structural or functional changes in the arterial tree.

Adolescent↗

PubMed1989

Increased vasodilator response during stimulation of cardiopulmonary baroreceptors in borderline hypertensives.

1. The effects of passive leg elevation on the forearm circulation were compared in 14 borderline hypertensive and 16 normotensive men. 2. In the supine position, mean arterial pressure (MAP), heart rate (HR) and forearm blood flow (FBF) were significantly greater in borderline hypertensives. 3. With leg raising, MAP and HR did not change significantly from basal values. FBF increased by +0.6 +/- 0.2 (s.e.m.) mL/min/100 mL (P less than 0.02) in normotensives and by + 1.3 +/- 0.2 mL/min/100 mL (P less than 0.001) in hypertensives (P for difference between groups less than 0.05).

Adolescent↗

PubMed1989

Pulsatile versus steady component of blood pressure: a cross-sectional analysis and a prospective analysis on cardiovascular mortality.

Studies on the prognostic significance of blood pressure on cardiovascular disease have essentially investigated the levels of diastolic or systolic blood pressure. However, blood pressure may also be divided into two other components: steady (mean arterial pressure) and pulsatile (pulse arterial pressure). The relations of these two components with cardiovascular risk factors and cardiovascular mortality were investigated in 18,336 men and 9,351 women aged 40-69 years, who were followed up for a mean period of 9.5 years. However, the interpretation of the relations is complicated by the strong correlation existing between these two components. A principal component analysis was performed to obtain two independent parameters: a steady and a pulsatile component index, strongly correlated with mean and pulse arterial pressure, respectively. In the cross-sectional analysis, relations were stronger with the steady component index than with the pulsatile component index; an association was found between left ventricular hypertrophy and the pulsatile component index in both sexes. The survival analysis was not performed in women under 55 as only 11 cardiovascular deaths occurred in this group. The steady component index was a strong prognostic factor of all types of cardiovascular death in both sexes. In women, the pulsatile component index was positively correlated to death from coronary artery disease and inversely correlated to stroke. In conclusion, the steady component of blood pressure is a strong risk factor for cardiovascular death in both sexes; the pulsatile component could be a risk factor independent of the steady component in women older than 55 years.

Adult↗

PubMed1989

[Central modulation of the baroreflex response to phenylephrine in rats. Lack of interaction between calcium channel modulators and the renin-angiotensin system].

We have previously shown that a calcium channel activator (BAY K 8644) can decrease the baroreflex control of heart rate in SHR when intracerebroventricularly (i.c.v.) administered. In pentobarbital anesthetized SHR, the inhibitory effect of BAY (3 micrograms/kg i.c.v.) on baroreflex sensitivity (BRS; ramp method: phenylephrine 2 micrograms i.v.; BAY: 0.14 +/- 0.05 vs control: 0.39 +/- 0.08 msec/mmHg; p less than 0.01) was fully suppressed after pretreatment with the muscarinic antagonist atropine methylnitrate (80 micrograms/kg i.c.v.) suggesting the involvement of cholinergic pathways in the inhibitory effect. Since A II was reported to centrally increase arterial pressure through an enhanced release of acetylcholine and to depress BRS, we tested whether the effect of BAY on BRS could involve central A II systems. The A II antagonist [Sar 1Ile8] A II (30 micrograms/kg/min i.c.v.) suppressed the inhibitory effect of A II on BRS (control: 0.32 +/- 0.09; A II: 0.10 +/- 0.02; Sar1 Ile8 + A II: 0.39 +/- 0.08 msec/mmHg) but not the inhibitory effect of BAY (3 mu g/kg i.c.v.) on BRS. These results suggest that the central inhibition of BRS by BAY unlikely involves central A II systems.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗

PubMed1989

[Increased vasodilation response to the stimulation of low pressure mechanoreceptors in borderline hypertension].

Passive lifting of the lower limbs (antitilt) is a simple manoeuvre which stimulates low-pressure mechanoreceptors. Patients with borderline hypertension have an alteration of the arterial baroreflex modulated by an increased inhibitory effect of cardiopulmonary mechanoreceptors on vasomotor centres. The repercussions of antitilt on mean arterial pressure (MAP), heart rate (HR) and blood flow rate in the forearm (FRFA) were studied in 30 male subjects aged 18 to 25 years: 14 with untreated borderline hypertension ("patients") and 16 controls. FRFA was measured with a plethysmograph by means of a mercury constraint gauge. MAP was recorded during exploration with a DINAMAP instrument. The parameters were measured in recumbent position, then within minutes of the antitilt manoeuvre. In recumbent position the differences between patients and controls were: MAP 94.7 +/- 6 vs 84.7 +/- 7 mmHg (p less than 0.001); HR 76 +/- 13 vs 63 +/- 9 beats/min (p less than 0.01); FRFA 4.6 +/- 1.5 vs 3.5 +/- 1.4 ml/min/100 ml (p less than 0.05). Following antitilt, MAP and HR remained unchanged in the two groups, but there was a significant increase of FRFA in both controls (+ 0.6 +/- 0.2 ml/min/100 ml; p less than 0.02) and patients (+ 1.3 +/- 0.2 ml/min/100 ml; p less than 0.001). This increase was significantly greater in patients than in controls (p less than 0.05). This study shows that antitilt produces an increase of blood flow rate in the forearm that is more pronounced in patients with borderline hypertension than in controls. The stability of MAP and HR is in favour of non-actuation of the high-pressure arterial baroreflex.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1989

[Ambulatory registration of arterial pressure during treatment with perindopril. Effects on systolic pressure and hemodynamic implications].

The effects of perindopril on the 24-hour arterial pressure levels were evaluated by ambulatory recording in 21 patients (mean age 48 +/- 2 years) with mild to moderate hypertension. At the end of a 3 months treatment with perindopril (4 to 8 mg per day in one dose), comparison by variance analysis of the mean values of arterial pressure over 24 hours before and after treatment showed a significant decrease of SAP (from 144 +/- 3 to 133 +/- 3 mmHg, p less than 0.01) and DAP (from 95 +/- 2 to 87 +/- 2 mmHg, p less than 0.01). The fall in arterial pressures was more pronounced during day-time (7 a.m. to 10 p.m.) than at night. Particular attention was paid to the reduction of systolic pressure owing to its relation with arterial compliance. There was a significant correlation between ambulatory recordings of SAP and DAP before and after treatment (r = 0.82 and 0.76 respectively, p less than 0.001). Calculation and comparison of the corresponding regression slope showed that for any given level of DAP, SAP was lower after than before treatment. This effect is related to the increase of arterial compliance observed after treatment with perindopril, as already reported by other authors.

Antihypertensive Agents↗

PubMed1989

[Arterial pressure--self measurement. Recommendations. French Society for Arterial Hypertension--the Measurement Group].

Self-measurement of blood pressure has become widespread in recent years. It may be defined as the measurement of arterial pressure by a conscious and free-willed subject. Self-measurement must remain a medical procedure, which means that doctors should be able to advise their patients (a) on the type of apparatus they should purchase and get validated at regular intervals; (b) on the method of using the apparatus in practice, and (c) on the circumstances, conditions and numbers of measurements to be performed. Doctors must remain responsible for the interpretation of the results obtained and for the diagnostic, pronostic an therapeutic applications of the method. Self-measurement of blood pressure naturally has advantages and disadvantages, but it must be noted that it may offer an alternative to hospitalization or to ambulatory arterial pressure measurement, avoid excessive or defective therapies and improve the patient's compliance with his treatment.

Blood Pressure Determination↗

PubMed1989

[Anomalies in the hemodynamic response to short lasting emotional stress in essential hypertensive subjects].

Systemic hemodynamics, brachial artery diameter (D) and blood flow velocity (v) were determined non-invasively in 26 normotensive subjects (NT) and 34 age- and sex-matched essential hypertensive patients (HT) using pulsed Doppler systems (4 and 8 MHz), at rest and during 2 min periods of mental arithmetic (MA) inducing reproducible changes in blood pressure. During MA in HT, v increased (from 5.3 +/- 1.1 to 8.4 +/- 1.6 cm/sec) to a greater extent (p less than 0.01) than in NT (from 4.9 +/- 0.7 to 6.3 +/- 1.4 cm/sec). Hand exclusion did not change the increase in v in HT and in NT. During MA, D did not change in both groups. Systolic and diastolic arterial pressure increased to a greater extent (p less than 0.01) in HT than in NT, while HR and pulse pressure increased to the same extent in both groups. Since cardiac output and D did not change during MA, instantaneous variations of v likely reflected modulation of arteriolar tone. These results suggest an enhanced vasodilatory response of muscle resistance vessels in HT as compared to NT. The lack of change in D suggest an increase in vascular tone of large arteries likely contributing to the rise in pulse pressure during MA in both groups.

Adult↗

PubMed1989

[Venous tone of the limbs. Methods and comparison of 2 areas].

The limb venous tone, index of local venous compliance, was studied with mercury strain gauge plethysmography on 28 male normal subjects (40 +/- 17 years, +/- SD) simultaneously on upper and lower limbs. Measurements were done after 20 mn rest in supine position. Venous tone (VT) equals the slope of the pressure-volume curve established by simultaneous recording of the forearm and calf relative volumes for successive steps of pressure lower than or equal to 30 mmHg. Limb venous capacitance was expressed by means of the maximal limb relative volume (V30) reached for a pressure of 30 mmHg applied through cuffs in standardized conditions. The upper limb venous tone was greater than the lower limb venous tone: 24.3 +/- 8.2 mmHg/ml/100 vs 17.5 +/- 7.9 mmHg/ml/100, p = 0.001. V30 was greater in lower limb than in upper limb: 1.5 +/- 0.5 ml/100 vs 1.1 +/- 0.4 ml/100, p = 0.001. In conclusion, it appears that upper and lower limbs venous distensibility and capacitance are different. They are greater in the lower limb in baseline conditions. Thus simultaneous studies of both these limb venous systems seems important for physiological experiments because of their baseline differences.

Adult↗

PubMed1989

[Effects of rilmenidine on arterial parameters in essential arterial hypertension].

Rilmenidine (RIL) is a new antihypertensive agent which lowers sympathetic tone, so reducing systemic peripheral resistance. The effects of a single dose of RIL (1 mg) on arterial function were the object of a preliminary randomised double-blind versus placebo trial in 14 patients with hypertension after a one month washout period on placebo. The following parameters were recorded before (T0) and 4 hours after administration (T4): blood pressure, heart rate (automatic recordings), diameter of the humeral artery (D), mean blood flow velocity (Vm) by an 8 MHz duplex pulsed Doppler system, local forearm resistances (LR = mean BP/D2 Vm/4), carotid-femoral pulse wave velocity (PWV) and humeral arterial wall tension (mean BP.D/2). The two groups were compared by statistical analysis of variance with two crossed factors. RIL significantly lowered systolic BP (p less than 0.02), diastolic BP (p less than 0.05) and mean BP (p less than 0.01) without changing the heart rate. The D and PWV were unchanged in the RIL group. There was a significant improvement in arterial wall tension (-6.7% vs + 1.1%; p = 0.02) associated with a tendency to increase the PWV (45% vs 4%; p = 0.097) and to decrease LR (46% vs 10%; p = 0.062) although those changes were not statistically significant compared with those observed with placebo. These initial results indicate that the hypotensive effect of RIL is accompanied by a reduction in humeral arterial wall tension which occurs without any change in arterial diameter. This also reflects a change in the pressure-volume relationship with RIL.(ABSTRACT TRUNCATED AT 250 WORDS)

Antihypertensive Agents↗

PubMed1989

[Electric left ventricular hypertrophy and pulsatile component of arterial pressure in a population study].

High systolic or diastolic blood pressure is a risk factor of left ventricular hypertrophy. However, haemodynamically speaking blood pressure is made of two components: continuous and pulsatile. Few authors have analysed the relationship between these two components and left ventricular hypertrophy. A horizontal study was conducted in 27, 687 subjects who volunteered for a medical check-up in Paris. A principal component analysis led to the estimation of two distinct parameters: a continuous pressure index (CPI) and a pulsed pressure index (PPI). The correlation between CPI and age was linear, whereas PPI was independent of age before 55 years and thereafter increased in a linear manner. This study also confirmed the importance of the relationship between the continuous component of blood pressure and electrocardiographic left ventricular hypertrophy. It is suggested that the pulsatile component might also be a risk factor of left ventricular hypertrophy independently of the continuous component level. Only a prospective study would confirm that an increase in the pulsatile component of blood pressure has a prognostic value as regards ventricular hypertrophy.

Adult↗

PubMed1989

[Therapeutic response to canrenone of patients with essential hypertension as a function of sodium transport anomalies and ouabain sensitivity of erythrocytes].

The presence of Na+ transport abnormalities (decreased affinity of the Na+/K+ pump or the Na+, K+ cotransport for internal Na+, increased Na+:Li+ countertransport, increased Na+ leak), Na+ content, Na+/K+ pump activity and sensitivity to ouabain were investigated in erythrocytes from 13 patients with essential hypertension. According to the presence or absence of Na+ transport abnormalities, the patients were divided into two groups: TrNa(+) (n = 9) and TrNa(-) (n = 4) respectively. Compared with TrNa(-) patients, TrNa(+) patients were characterized by: (i) a higher arterial pressure (131.4 +/- 11.8 vs 110.0 +/- 13.2 mmHg, p less than 0.05), (ii) an increased erythrocyte Na+ content (8.9 +/- 1.0 vs 6.3 +/- 0.8 mmol/l.cells, p less than 0.01) associated with (iii) a decreased rate constant of Na+/K+ pump activity (235 +/- 26 vs 309 +/- 45 h-1, p less than 0.05) and (iv) a higher sensitivity to ouabain (0.76 +/- 0.23 vs 1.12 +/- 0.26 microM, p less than 0.05). Oral administration of canrenone 50 mg per day during 7 weeks decreased mean arterial pressure by 10-30 mmHg in 6 out of the 9 TrNa(+) patients. Conversely, it decreased mean arterial pressure in only one out of the 4 TrNa(-) patients. The hypotensive effect of canrenone in TrNa(+) patients was not associated with normalization of their Na+/K+ pump activity. Canrenone did not modify the sensitivity to ouabain of either the TrNa(+) or the TrNa(-) patients. Before treatment, acute injection of ouabain provoked an inhibition of the erythrocyte Na+/K+ pump, without any change in Na+ content.(ABSTRACT TRUNCATED AT 250 WORDS)

Biological Transport↗

PubMed1989

[Evaluation of the effectiveness of a cicletanine-enalapril combination in hypertensive patients].

In this multicentre controlled single blind trial the effectiveness and safety of cicletanine (100 mg/day) were compared with those of enalapril (20 mg/day) and of the combination of both drugs in the same doses in 72 patients (41 men, 31 women, mean age 64.1 +/- 8.3 years) with permanent moderate essential hypertension without severe cardiovascular complications. In the course of the trial, one patient in each of the three therapeutic groups was excluded either for insufficient effectiveness in monotherapy or for photosensitization under the combined treatment. After two months of treatment, the fall in blood pressure and the number of patients with normalized BP were similar in the groups treated with cicletanine or enalapril alone. In contrast, the cicletanine-enalapril combination produced a significantly greater fall of diastolic arterial pressure than cicletanine alone. In addition, there was a greater reduction of functional symptoms associated with arterial hypertension. Apart from the lone case of photosensitization observed with the combined treatment, only minor side-effects were encountered, including an episode of diarrhoea and a case of extrasystoles with the combination, and a case or nausea with lipothymia under cicletanine alone. There were no significant variations of biochemical values.

Aged↗

PubMed1989

[Cardiac arrhythmia in moderate arterial hypertension. Epidemiologic survey of 251 cases. Effect of sotalol].

251 untreated patients with mild to moderate hypertension were included in a multicenter study aimed 1) to detect arrhythmias (24-H Holter recording) and 2) to assess the efficacy of sotalol on blood pressure and possible arrhythmias. Patients with coronary heart disease or previously documented arrhythmias were excluded. Atrial arrhythmias such as premature beats, fibrillation, flutter and paroxysmal atrial tachycardia were detected in 16% of patients. Monomorphic ventricular premature contractions (VPCs) (Lown I and II) were detected in 41% of patients and polymorphic VPCs or duplets/triplets (Lown III and IV) in 14%. A correlation seems to exist between the level of hypertensive cardiopathy, judged on electrocardiographic data (Tarazi classification), age of patients and severity of arrhythmias. Sotalol was administered during 2 months at a mean dose of 160 mg per day. The treatment was effective on blood pressure and arrhythmias (82% improvement of severe VPCs) and the drug was well tolerated. It was difficult to conclude if these good results are due to the betablocking properties or specific class II antiarrhythmic effects of sotalol or to the combined activity.

Adult↗

PubMed1989

[Spontaneous dissection of the renal artery].

In this paper we describe a case involving spontaneous dissection of the renal artery (DRA) successfully treated with an aorto-renal venous graft. DRA is a rare disorder which strikes men especially. Hypertension is the most frequent sign of its presence, which is usually of sudden onset, and with major adverse impact on the eye and brain. Arteriography is the key diagnostic examination. The most typical image is that of "cuffing". Treatment is surgical in nearly 50% of cases and should be as conservative as possible since these lesions may be bilateral.

Aortic Dissection↗

PubMed1989

[Calcium inhibitors and arterial hypertension].

Calcium inhibitors decrease blood pressure and improve different functional and structural cardiovascular parameters of heart and vessels. Thus different calcium antagonists lead to variable changes of cardiac flow with reduction of cardiac hypertrophy and modifications of heart rate and inotropism. Their peripheral action on large arteries and arterioles can create a vasodilation with elevation of blood velocity and flow. An improvement in arterial and venous compliance is also observed.

Arteries↗