Longitudinal movements and resulting shear strain of the arterial wall

Abstract

Cinthio, Magnus, Å sa Rydén Ahlgren, Jonas Bergkvist, Tomas Jansson, Hans W. Persson, and Kjell Lindström. Longitudinal movements and resulting shear strain of the arterial wall. Am J Physiol Heart Circ Physiol 291: H394 -H402, 2006. First published February 10, 2006 doi:10.1152/ajpheart.00988.2005.-There has been little interest in the longitudinal movement of the arterial wall. It has been assumed that this movement is negligible compared with the diameter change. Using a new high-resolution noninvasive ultrasonic method, we measured longitudinal movements and diameter change of the common carotid artery of 10 healthy humans. During the cardiac cycle, a distinct bidirectional longitudinal movement of the intimamedia complex could be observed in all the subjects. An antegrade longitudinal movement, i.e., in the direction of blood flow, in early systole [0.39 mm (SD 0.26)] was followed by a retrograde longitudinal movement, i.e., in the direction opposite blood flow [Ϫ0.52 mm (SD 0.27)], later in systole and a second antegrade longitudinal movement [0.41 mm (SD 0.33)] in diastole. The corresponding diameter change was 0.65 mm (SD 0.19). The adventitial region showed the same basic pattern of longitudinal movement; however, the magnitude of the movements was smaller than that of the intimamedia complex, thereby introducing shear strain and, thus, shear stress within the wall [maximum shear strain between the intima-media complex and the adventitial region was 0.36 rad (SD 0.26). These phenomena have not previously been described. Measurements were also performed on the abdominal aorta (n ϭ 3) and brachial (n ϭ 3) and popliteal (n ϭ 3) arteries. Our new information seems to be of fundamental importance for further study and evaluation of vascular biology and hemodynamics and, thus, for study of atherosclerosis and vascular diseases. carotid artery; vascular mechanics; arterial wall movements; shearing strain in arteries; vascular ultrasound IN CARDIOVASCULAR RESEARCH, radial movement of the arterial wall, i.e., diameter change, has been the subject of extensive research. Measurement of radial movements of arteries is an established tool in cardiovascular research (8,13,17,23), forming the basis for estimation of arterial wall stiffness. Increased stiffness of large central arteries has recently been shown to be an independent risk factor for cardiovascular mortality (4). In contrast to radial movements, there has been little interest in longitudinal movements of the arterial wall, i.e., along the vessel. It has been assumed that the longitudinal movement of the arterial wall during the cardiac cycle is negligible compared with the radial movement (21). Longitudinal movement of the arterial wall has not been studied, because, until the most recent improvements in ultrasound systems, it has not been possible to detect longitudinal movement in vivo. In the 1950s, using cinematographic observations of beads sutured to the surface of exposed vessels, Lawton and Greene (15) measured the longitudinal movement of the abd...

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“…We have, however, shown that in both large predominantly elastic arteries and in large muscular arteries there is a distinct bi-directional displacement of the arterial wall during the cardiac cycle [18]. The intima-media of these arteries exhibits a longitudinal displacement that is larger than that of the adventitial region [18] and thus, there is shear strain and shear stress within the arterial wall [18][19][20][21]. We have recently reported that longitudinal movement and intramural shear strain undergo profound changes in response to the important circulatory hormones adrenalin and noradrenalin [22], indicating that the longitudinal movements and resulting intramural shear strain can constitute an important but overlooked mechanism in the cardiovascular system.…”

“…In contrast to the radial movement, the longitudinal movement of the arterial wall has gained less attention. We have, however, shown that in both large predominantly elastic arteries and in large muscular arteries there is a distinct bi-directional displacement of the arterial wall during the cardiac cycle [18]. The intima-media of these arteries exhibits a longitudinal displacement that is larger than that of the adventitial region [18] and thus, there is shear strain and shear stress within the arterial wall [18][19][20][21].…”

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“…It is also possible to measure motion in 2D, so both longitudinal and lateral motions are measured. 48,49 Multi-line systems that measure wall motion, along multiple lines simultaneously, allow measurement of wall motion as a function of distance along the vessel. Such systems may be used to identify local patterns of wall motion, for example to identify regions of high longitudinal strain in plaque.…”

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“…Remark 4.1. In [9] evidence of a significant longitudinal component of the motion of the arterial wall in some vessels (e.g., the carotid artery) was provided. In contrast to the current conjecture, they observed a distinct longitudinal movement of the arterial wall which is of the same magnitude as the local diameter change for a healthy patient.…”