Biomedical subjects

X Girerd

Publications and source records attributed to X Girerd.

At least 73 records · Page 4Linked to original sources

PubMed1997

Increased stiffness of radial artery wall material in end-stage renal disease.

The incremental elastic modulus (Einc), which is the slope of the relationship between stress and strain of arteries, is a marker of vascular wall material stiffness. Isobaric Einc is reduced at the site of the radial artery in patients with essential hypertension and increased at the site of the common carotid artery in subjects with end-stage renal disease (ESRD). Whether the changes in Einc are influenced by the topography of the vessels, the composition of the arterial wall, and/or by the presence of ESRD is largely ignored. Radial artery Einc was measured in 19 patients with ESRD and compared with the Einc of 89 subjects with essential hypertension and 20 normotensive control subjects. Transcutaneous measurements of radial artery internal diameter and wall thickness (echo-tracking device) and digital pulse pressure (Finapres) were allowed to calculate Einc under operational (ie, at the mean arterial pressure of each group) and isobaric (100 mm Hg) conditions, as well as for a given wall stress. Internal diameter and pulsatile changes in diameter were identical in the three groups. Wall thickness and mean blood pressure were significantly elevated in subjects with hypertension but not in ESRD patients. Circumferential wall stress was identical in the three groups. For the same operational wall stress, and therefore at the operational mean arterial pressure of each group, Einc (kPa x 10[3]) was increased in patients with ESRD (5.53+/-4.0 versus 3.3+/-2.4 in control subjects; P<.05) and normal in subjects with essential hypertension (3.87+/-4.0). Under isobaric conditions, Einc was also significantly lower in subjects with hypertension and elevated in patients with ESRD. Thus, at the site of a medium-sized muscular artery constantly devoid of atherosclerosis, the stiffness of wall material is increased in patients with ESRD. The demonstrated alterations of the arterial wall are independent of the level of blood pressure and tensile stress and should be related to the status ESRD.

Blood Pressure↗

PubMed1996

[First intention treatment of arterial hypertension using a combination of two drugs].

The limited efficacy of single-drug regimens in the treatment of high blood pressure has led to an evaluation of combination regimens for first intention treatment. Two-drug regimens favor the hypotensive efficacy and reduce the frequency of certain side effects. Medications combining two drugs in a single formulation would allow use as first line treatment although marketing authorizations have not yet been obtained. In addition, current good clinical practice recommendations do not allow combination therapy in this situation. A complete assessment based on medical results and cost effectiveness will undoubtedly confirm the usefulness of two-drug therapies as first line treatment for moderate hypertension.

Antihypertensive Agents↗

PubMed1996

[Treatment of renal artery stenosis].

Management of renovascular disease can be based on surgical revascularization, medical therapy or interventional radiology. Results obtained with transluminal angioplasty, as compared to surgery, indicate that interventional radiology should be used as first treatment in patients with renovascular hypertension without renal failure. The best indications are treatments of fibrous dysplasia, and atherosclerotic stenosis complicated with pulmonary oedema. In case of restenosis, observed mainly with atherosclerotic stenosis, a second angioplasty eventually combined with stent implantation can be performed. Surgical repair is indicated when angioplasty has not been successful or when arterial lesions are too complex.

Arteriosclerosis↗

PubMed1996

Structural changes of large conduit arteries in hypertension.

BACKGROUND: Structural alterations of large conduit arteries are a common pathway for any complication of hypertensive vascular disease. Whether increased arterial wall thickness occurs at an early phase in uncomplicated hypertension has remained largely ignored until recent years. METHODS: Sophisticated echo-Doppler techniques with a high degree of resolution and reproducibility have been developed to obtain reliable non-invasive determinations of intima-media thickness of superficial arteries such as the radial and the common carotid arteries. RESULTS: In uncomplicated hypertension, a significant increase in intima-media thickness is observed at the sites both of the radial and of the carotid arteries. The former is known to be constantly undamaged by atheroscierosis and is composed almost exclusively of arterial smooth muscle; operational arterial stiffness is found to be normal. The latter is strongly affected by atheroscierosis and predominantly composed of elastin and collagen fibres; operational arterial stiffness is found to be increased. In old subjects with systolic hypertension, radial artery hypertrophy is significantly reversed by drug therapy involving diuretics, converting enzyme inhibitors or both. This change occurs in parallel with the reduction in blood pressure. CONCLUSION: In sustained essential hypertension, arterial wall hypertrophy can be demonstrated in the absence of organ damage. Operational arterial elasticity is maintained in peripheral but not in central arteries. Structural changes of the large conduit arteries are substantially reversed by drug therapy together with a reduction in blood pressure.

Animals↗

PubMed1996

Remodeling of the radial artery in response to a chronic increase in shear stress.

Chronic changes in large artery blood flow rates induce corresponding adjustments in arterial diameter, but little is known about structural adaptations of the vessel wall in humans. We used a high-resolution echo-tracking system to measure radial artery internal diameter, wall thickness, and mean blood flow on both arms of 11 patients with end-stage renal disease. Measurements were performed on the wrist side of the arteriovenous fistula. The contralateral radial artery was investigated as control. Wall cross-sectional area, circumferential wall stress, and mean wall shear stress were calculated. Results indicate a sixfold increase in blood flow on the side of the arteriovenous fistula compared with the control side, with a 1.4-fold increase in internal diameter. The diameter enlargement was sufficient to normalize wall shear stress. Changes in diameter were not associated with arterial wall hypertrophy because wall cross-sectional area was not increased and rather suggest a "remodeling" of the arterial wall. For the same level of blood pressure, circumferential wall stress was increased on the side of the arteriovenous fistula. These results suggest that the structural adaptations of the arterial wall to a chronic increase in blood flow normalize wall shear stress and overcome stretch-induced changes in the particular circumstance of arteriovenous fistula.

Adult↗

PubMed1996

Arterial stiffening: opposing effects of age- and hypertension-associated structural changes.

This article reviews the effects of aging and hypertension on geometrical (lumen and arterial wall thickness) and functional (distensibility) properties of large and medium-sized arteries in humans. Several clinical and animal studies show that arterial wall hypertrophy does not increase the elastic modulus of the arterial wall material during sustained essential hypertension. The structural changes associated with either hypertension or aging have opposing effects on arterial distensibility, under similar transmural conditions: the former increasing it, the latter decreasing it. Thus, hypertension cannot be assimilated to aging. The structural and functional changes of the arterial wall material that are associated with the hypertension-induced hypertrophy could be a means by which medium-sized arteries maintain their distensibility characteristics despite increased distending pressure, and large arteries compensate for the age-induced decrease in arterial compliance.

Aging↗

PubMed1996

[Arterial hypertension, aging and cardiac decompensation].

Cardiac function of hypertensive patients is normal, or even better than normal, despite the presence of cardiac hypertrophy. It is therefore difficult to explain the mechanism of decompensation phenomena, especially as clinicians are rarely able to observe the passage from the compensated phase to the phase of decompensated hypertensive heart failure. Various arguments suggest that cardiovascular ageing, independently of hypertension, exerts specific haemodynamic effects which can be responsible for decompensation. In the heart, extension of fibrosis can be responsible for a defect of diastolic expansion and the development of arrhythmias. In the vessels, increased aortic rigidity is responsible for a dissociation between cardiac and vascular functions, especially as the pressure reflection wave returns during the systolic phase rather than the diastolic phase of the pressure curve. These data suggest that Cardiac failure phenomena now justify thorough evaluation of arterial function, which can currently be investigated by noninvasive techniques.

Aging↗

PubMed1995

[Treatment of hypertension in the elderly].

Although an increase in the systolic pressure is a physiological phenomenon of the ageing process, the beneficial effect of treatment in the elderly, in terms of reducing risk of cerebral vascular events, heart failure and coronary artery disease, leads to a common definition of hypertension in adults. A subject is considered to have hypertension if the systolic pressure is greater than 160 mmHg or the diastolic pressure is greater than 95 mmHg. A subject whose blood pressure is less than 140/90 mmHg is considered to be normotensive. The rules and strategy for the prescription of antihypertensive drugs remain the same whatever the age of the patient. But, despite the large number of drugs available, it is often difficult to obtain normal levels in the elderly. Treatment should thus be based on a pragmatic strategy, setting the target level as a function of the initial blood pressure. A decrease of 20 to 30 mmHg in the systolic pressure should be considered as a satisfactory result. In the elderly patient, the rule should be to limit prescription to two drugs since these patients risk exposure to interactions with other pharmaceutical classes because of the multiple disease situations encountered. In case of "non-response" to a two-drug regimen, the physician should carefully question patient compliance, search for an unrecognized primary cause, and reconsider the validity of pressure assessment at consultation. A third drug cannot be justified unless non-response has been confirmed with ambulatory or self-measurement of blood pressure levels.

Age Factors↗

PubMed1995

Common carotid artery stiffness and patterns of left ventricular hypertrophy in hypertensive patients.

The aim of this study was to determine the relationship between the lumen diameter and function of the common carotid artery, a vessel representative of the capacitance portion of the circulation, and the different patterns of left ventricular hypertrophy in uncomplicated essential hypertensive patients. Carotid luminal diastolic cross-sectional area, distensibility, and compliance were derived from measurements by a high-definition echotracking system. Left ventricular dimensions were from echocardiography. The 86 hypertensive patients included 31 who had never been treated (group 1), 31 in whom treatment had been stopped for at least 2 weeks (group 2), and 24 treated patients (group 3). In multivariate analysis of the population as a whole, the following relations were statistically independent of age, blood pressure, gender, and group: Left ventricular end-diastolic volume index was positively correlated to carotid luminal cross-sectional area (r = .46, P < .0001) and compliance (r = .47, P < .0001); left ventricular mean wall thickness and mass-volume ratio were negatively correlated to distensibility (r = -.68, P < .0001; r = -.46, P < .0001, respectively) and compliance (r = -.40, P < .0001; r = -.37; P < .001, respectively); and left ventricular mass index was positively correlated to luminal cross-sectional area (r = .23, P < .02) and negatively to distensibility (r = -.26, P < .01). These results indicate that geometric and functional changes in the common carotid artery accompany geometric changes in the left ventricle. More specifically, they suggest that a reduction in distensibility paralleled cardiac concentric hypertrophy and remodeling, whereas an increase in arterial volume paralleled increased left ventricular cavity size.

Adult↗

PubMed1995

Aortic distensibility and structural changes in sinoaortic-denervated rats.

The purpose of the present study was to determine the effects of chronic sinoaortic denervation on the mechanical properties and composition of the abdominal aorta in Wistar rats. We used a high-resolution echotracking system to determine in situ under physiological conditions of blood flow and arterial wall innervation the aortic diameter-, compliance-, and distensibility-pressure curves in 16-week-old anesthetized rats that had been denervated at 10 weeks of age for 6 weeks (n = 8). Compared with sham-operated rats (n = 8) we observed a marked reduction of baroreflex response and increase in overall mean blood pressure variability as measured by standard deviation and spectral analysis in sinoaortic-denervated rats. Mean blood pressure was not affected by sinoaortic denervation in both conscious and anesthetized rats. Sinoaortic denervation significantly shifted the distensibility-pressure curve toward lower levels of distensibility, indicating a decreased aortic distensibility for a given level of arterial pressure. Sinoaortic denervation produced a significant increase of aortic wall cross-sectional area and collagen content, one of the less-distensible components of the arterial wall. These results suggest that intact arterial baroreceptors are necessary for maintaining normal functional and structural properties of large arteries in rats. The reduction in arterial distensibility in chronic sinoaortic-denervated rats may have resulted from different factors, including the initial hypertensive phase, aortic wall hypertrophy, and increase in collagen content. The changes in aortic wall structure and related reduction in aortic distensibility, in addition to other mechanisms, might have been direct consequences of an increased blood pressure variability.

Animals↗

PubMed1994

[Therapeutic approach in arterial hypertension with renal artery stenosis].

Screening for renal artery stenoses in hypertensive patients aims at detecting lesions whose treatment (renal revascularization) will normalize or reduce blood pressure and correct or prevent reduced glomerular filtration. Consequently, screening tests such as renal artery duplex Doppler scanning, renal scintigraphy or digital-subtraction angiography are used in patients in whom hypertension is severe, drug-resistant or associated with renal failure. Surgical repair or transluminal angioplasty is not warranted for all stenoses, however, particularly in atheromatous stenoses where these procedures have a 1% mortality, a 10% morbidity and a 30% failure rate to improve blood pressure despite adequate anatomical outcome. Predictors of favourable blood pressure outcome following revascularization are aetiological (fibrous dysplasia rather than atheroma), historical (young age, short duration of hypertension), physiological (renal ischaemia confirmed by scintigraphy, lateralizing renal vein renin ratio) and anatomical (truncal rather than ostial or branch stenoses). Outcome of surgery and transluminal angioplasty has only been documented in retrospective, uncontrolled reports in which blood pressure improvement is overestimated via the placebo effect, habituation to blood pressure readings and optimization of drug treatment, the latter being frequently required despite adequate revascularization. The first prospective randomized trials evaluating angioplasty in atheromatous stenoses are underway and should provide objective information concerning the risk/benefit ratio of this procedure.

Dilatation↗

PubMed1994

Noninvasive detection of an increased vascular mass in untreated hypertensive patients.

Structural changes of the arterial vasculature are of major pathophysiologic and prognostic significance in human hypertension. A high-resolution ultrasonic echotracking device was used to measure internal diameter and intima-media thickness of the radial artery, a medium-sized muscular conduit artery, in 60 hypertensive patients and in 40 age-matched control subjects. Of the 60 hypertensives, 33 were never treated and 27 were well-controlled by antihypertensive therapy. Radial artery mass and thickness/radius ratio were used to describe the radial artery structure. Radial artery mass was validated in vitro by comparing the weight of arterial segments to the ultrasonographic determination of their mass, calculated as: rho L(pi Re2-pi Ri2), where rho is the arterial wall density, L the length of the arterial segment, and Re and Ri the ultrasonic values of internal and external radii, respectively. Diastolic internal diameter did not differ among the three groups, but wall thickness, radial artery mass, and thickness/radius ratio were significantly higher in the untreated hypertensive group than in the control group. In treated well-controlled hypertensive subjects, radial artery mass and thickness/radius ratio were not different from that of control subjects. Among the population of untreated patients, significant univariate relations existed between radial artery mass and blood pressure and radial artery mass and age. In multivariate analysis, radial artery mass was independently predicted by mean blood pressure, age, and sex. Circumferential wall stress, calculated from diastolic internal diameter, wall thickness, and diastolic blood pressure, was not different in the three groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1994

Sympathetic activation decreases medium-sized arterial compliance in humans.

This study used a precise noninvasive method in normotensive humans to determine the effects of sympathetic activation on arterial compliance. A recently developed, high-resolution echo-tracking system capable of measuring systolic/diastolic variations of arterial diameter was coupled to a Finapres system and used to calculate instantaneous systolic/diastolic pressure-diameter and compliance-pressure curves for a muscular medium-sized artery, the radial artery. Two standardized tests of sympathetic system activation, a cold pressor test (2 min) and a mental stress test (2 min of mental arithmetic), were performed at an interval of 8 days in random order in nine healthy volunteers [30 +/- 9 (SD) yr]. Radial arterial parameters were recorded every 30 s for 9 min, which included 2 min of cold pressor test or mental stress test. During both tests, radial arterial mean diameter did not change despite t he increase in mean arterial pressure (P < 0.001); stroke change in diameter decreased (P < 0.01), whereas pulse pressure increased (P < 0.01). Arterial compliance, calculated for the instantaneous level of mean arterial pressure, decreased significantly (P < 0.01). Compliance (C) calculated at 100 mmHg (C100) was arbitrarily chosen as a reference point for comparing compliance among the different periods of the test. C100 decreased significant (P < 0.05) during both tests (from 2.93 +/- 1.27 to 2.04 +/- 0.94 and from 3.29 +/- 1.73 to 2.63 +/- 1.55 mm2.mmHg-1.10(-3) during mental stress and the cold pressor test, respectively). These results indicate that sympathetic activation is able to decrease radial arterial compliance in healthy subjects. The reduction in arterial compliance probably resulted from complex interactions between changes in distending blood pressure and changes in radial arterial smooth muscle tone.

Adult↗

PubMed1994

Elastic modulus of the radial artery wall material is not increased in patients with essential hypertension.

Hypertension is known to decrease arterial distensibility and systemic compliance. However, the arterial tree is not homogeneous, and it has been shown that the medium-size radial artery does not behave like the proximal, elastic, large, common carotid artery. Indeed, radial artery compliance in hypertensive patients (HTs) has been shown to be paradoxically increased when compared with that in normotensive control subjects (NTs) at the same blood pressure level. To determine whether this increase was due to hypertension-related hypertrophy of the arterial wall, radial artery functional and geometric parameters from 22 NTs (mean +/- SD, 44 +/- 11 years) were compared with those from 25 age- and sex-matched never-treated essential HTs (48 +/- 12 years) by using a high-precision ultrasonic, echo-tracking system coupled to a photoplethysmograph (Finapres system), which allows simultaneous arterial internal diameter, intima-media thickness, and finger blood pressure measurements. When the values for HTs were compared with those of NTs at their respective mean arterial pressures, HTs had similar internal diameter (2.50 +/- 0.56 versus 2.53 +/- 0.32 mm, mean +/- SD) and greater intima-media thickness (0.40 +/- 0.06 versus 0.28 +/- 0.05 mm, P < .001) measurements and increased arterial wall cross-sectional areas (3.79 +/- 1.14 versus 2.45 +/- 0.57 mm2, P < .001). Circumferential wall stress was not significantly different between the two groups. Compliance calculated for a given blood pressure, ie, 100 mm Hg (C100), was greater in HTs than NTs (3.46 +/- 2.41 versus 2.10 +/- 1.55 m2.kPa-1 x 10(-8), P < .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1994

Carotid artery distensibility and distending pressure in hypertensive humans.

Whether the decrease in large-artery distensibility observed in hypertensive patients is due primarily to an increase in distending pressure or to hypertension-induced changes in structural properties has been much debated. We determined noninvasively the diameter-pressure curve of the common carotid artery over the systolic-diastolic range by continuously recording both the pulsatile changes in internal diameter (high-resolution echo-tracking system) and, simultaneously on the contralateral artery, the pressure waveform (high-fidelity applanation tonometry). We then derived the distensibility/pressure curve and compared arterial distensibility in 14 normotensive subjects and 15 age- and sex-matched hypertensive subjects at their respective mean arterial pressures (MAP) and at a common distending pressure: 100 mm Hg. Distensibility decreased as blood pressure increased, and distensibility at MAP was significantly lower in hypertensive than in normotensive subjects (7.8 +/- 0.7 versus 11.7 +/- 1.7 kPa-1.10(-3), mean +/- SEM; P < .05). In hypertensive subjects, the distensibility-pressure curve was shifted toward higher levels of blood pressure, and a large part of the curve overlapped that of normotensive subjects. No significant downward shift of the distensibility-pressure curve was observed in hypertensive subjects, and distensibility at 100 mm Hg was not significantly different from that of normotensive subjects (10.0 +/- 1.0 versus 9.0 +/- 1.1 kPa-1.10(-3)). Distensibility at 100 mm Hg decreased with aging (P < .05) and was not reduced in hypertensive subjects compared with normotensive subjects after adjustment for age.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1994

[Measurement of the vascular mass of the human radial artery by ultrasonics].

OBJECTIVE: To determine the reproducibility of radial artery mass (RAM), in hypertensive patients. DESIGN AND METHODS: In 49 patients, RAM was measured using a high resolution echotracking device (Nius-02) which allows noninvasive measurement of diameter and wall thickness of the radial artery. RAM was validated in vitro by comparing weight of arterial segments to ultrasonographic measurement and determined as RAM = r (pi Re2-pi Ri2) where r is the arterial wall density (1.06 g/cm3), and Re and Ri are values of internal and external radii, respectively. Repeatability coefficient (RC2 = SDi2/n) was 1.3 mg. RESULTS: Blood pressure was (mean +/- SD) 146 +/- 19/85 +/- 15 mmHg, radial arterial diameter was 2,449 +/- 376 microns, radial wall thickness was 302 +/- 68 microns, RAM was 28 +/- 9 mg (range 13-43 mg). CONCLUSION: These results indicate that radial artery mass can be measured using a high resolution echotracking device.

Humans↗

PubMed1994

[Arterial compliance is not diminished in hypertensive patients when compared at the same level of blood pressure].

Whether the decrease in large artery compliance, observed in hypertensive patients (HT), is due to an increase in distending pressure or to intrinsic alterations of the vascular wall remains much debated. We determined the diameter-pressure curve of the common carotid artery over the systolic-diastolic range, then derived the compliance-pressure curve, in order to compare arterial compliance in normotensive subject (NT) and in HT, for a common level of distending blood pressure: 100 mmHg (isobaric compliance). Fourteen NT and 15 never treated essential HT were included in the study. The diameter-pressure curve of the common carotid artery was determined non-invasively by simultaneously and continuously recording the systolic-diastolic changes in internal diameter (using a high resolution echotracking system) and pressure waveform (using high fidelity applanation tonometry on the contralateral artery) over 4-6 cardiac cycles. The level of MAP of the carotid pressure waveform was determined electronically and set equal to mean brachial pressure. Compliance-pressure curve was then derived from the pressure-diameter curve in order to determine compliance (C) for any given level of blood pressure, particularly MAP (CMAP) and 100 mmHg (C100). Despite the considerable differences in blood pressure, the compliance-pressure curve of HT was not different from that of NT. CMAP decreased with aging (p < 0.001) and MAP (p < 0.001). According to age, CMAP was reduced in HT as compared to NT (84 +/- 49 vs 116 +/- 52 mm2.mmHg.10(-3) p < 0.01). C100 decreased with aging (p < 0.05) but not with MAP. According to age, C100 was not reduced in hypertensives.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1994

[Current status on the treatment of arterial hypertension in the elderly].

Hypertension in the elderly is a frequently encountered problem. When the permanent nature of such hypertension is confirmed, its treatment is justified. All types of drug can be used in the elderly but treatment must be started gradually and on an individual basis. In the majority of cases, one drug only should be sufficient to control hypertension in an elderly individual.

Aged↗