Showing papers by "Stéphane Laurent published in 1995"

Arterial Wall Hypertrophy and Stiffness in Essential Hypertensive Patients

Abstract: The purpose of this article is to review some clinical and fundamental evidence that hypertension-induced arterial wall hypertrophy at the site of large and medium-sized arteries is not necessarily associated with a decreased arterial distensibility and increased elastic modulus, and to demonstrate the opposing effects of aging and hypertension-induced hypertrophy on the arterial mechanics in vivo. in the studies reported here, the elastic properties of large and medium-sized arteries were noninvasively assessed from the simultaneous measurement of internal diameter and blood pressure inside the systolic-diastolic range. The distensibility of a medium-sized artery, the radial artery, in untreated essential hypertensive patients was not significantly different from that of normotensive control subjects when the two groups were compared at their respective mean arterial pressures. Despite increased wall thickness, the stiffness of the radial artery wall material, assessed by the incremental modulus of elasticity (Young's modulus), was not increased in hypertensive patients. At the site of a larger, more elastic artery, such as the common carotid artery, distensibility of hypertensive patients was significantly lower than that of normotensive subjects when the two groups were compared at their respective mean arterial pressures, but distensibility at 100 mm Hg was not significantly different between the two groups. Aging may alter distensibility independently of blood pressure, because carotid distensibility at 100 mm Hg was negatively correlated with age. In spontaneously hypertensive rats the elastic modulus of the common carotid artery wall material was not significantly different from that of Wistar-Kyoto rats at a given circumferential stress.(ABSTRACT TRUNCATED AT 250 WORDS)

Common Carotid Artery Stiffness and Patterns of Left Ventricular Hypertrophy in Hypertensive Patients

Abstract: 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 r =.47, P r =−.68, P r =−.46, P r =−.40, P r =−.37; P r =.23, P r =−.26, P

Aortic Distensibility and Structural Changes in Sinoaortic-Denervated Rats

Abstract: 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.

Structural changes and in situ aortic pressure-diameter relationship in long-term chemical-sympathectomized rats

Abstract: This study determined the effects of long-term chemical sympathectomy with guanethidine (GN) on the mechanical properties and composition of the distal abdominal aorta in Wistar rats. GN was daily administered for 3 mo (3M-GN, from 1 to 12 wk), 5 wk (5W-GN, from 7 to 12 wk), and 8 days (8D-GN, from 11 to 12 wk). All experiments were performed at 12 wk of age to avoid age differences at examination. We used a high-resolution echo-tracking system to determine in situ, in the systolic-diastolic range, the aortic diameter-, compliance-, and distensibility-pressure curves in anesthetized rats. We observed an equivalent significant fall in the tyramine pressor response in all conscious GN-treated rats. Blood pressure was not affected by sympathectomy after 8 days and 5 wk of treatment but was significantly reduced in 3M-GN rats. Chronic sympathetic denervation increased aortic diameter and compliance in 8D-GN rats, compared with those obtained at the same distending pressure in control rats, suggesting vascular smooth muscle relaxation. In contrast, in 5W-GN and 3M-GN rats, the distensibility pressure-curves were significantly shifted toward lower levels of distensibility and pressure, indicating a decreased aortic distensibility at the same level of arterial pressure. Sympathectomy produced a significant reduction in the content of elastin, one of the most distensible components of the arterial wall in 5W-GN and 3M-GN rats. These results suggest that intact sympathetic nerves are necessary to maintain normal functional and structural properties of large arteries in rat. The reduction in aortic distensibility, in long-term sympathectomized rats, could have resulted from complex interactions between local aortic denervation, change in the set point of distending pressure, and changes in aortic smooth muscle tone and/or wall composition.

Effects of antihypertensive drugs on large artery compliance

Abstract: The changes in arterial compliance following drug treatment have been studied mainly in hypertension. Physiologically, reduced arterial compliance independently affects blood pressure through an increase in systolic pressure and a decrease in diastolic pressure at any given value of mean arterial pressure. This review summarizes the pharmacological studies performed in recent years on the ability of antihypertensive drugs to modify arterial compliance. For the same decrease in mean arterial pressure, antihypertensive drugs may have differential effects improving arterial compliance (calcium channel blockers, converting enzyme inhibitors, alpha-blockers and some beta-blockers) or causing no change (dihydralazine, diuretics, propranolol) with resulting consequences on cardiac structure and function.