Longitudinal displacement and intramural shear strain of the porcine carotid artery undergo profound changes in response to catecholamines

Abstract

Ahlgren ÅR, Cinthio M, Steen S, Nilsson T, Sjöberg T, Persson HW, Lindström K. Longitudinal displacement and intramural shear strain of the porcine carotid artery undergo profound changes in response to catecholamines. Am J Physiol Heart Circ Physiol 302: H1102-H1115, 2012. First published December 23, 2011 doi:10.1152/ajpheart.00470.2011The effects of catecholamines on longitudinal displacements and intramural shear strain of the arterial wall are unexplored. Therefore, the common carotid artery of five anaesthetized pigs was investigated using an in-house developed noninvasive ultrasonic technique. The study protocol included intravenous infusion of low-dose epinephrine (␤-adrenoceptor activation), as well as intravenous boluses of norepinephrine (␣-adrenoceptor activation). Further, the effects of ␤-blockade (metoprolol) were studied. There were significant positive correlations between pulse pressure and longitudinal displacement of the intima-media complex (r ϭ 0.72; P Ͻ 0.001), as well as between pulse pressure and intramural shear strain (r ϭ 0.48; P Ͻ 0.001). Following administration of norepinephrine, the longitudinal displacement of the intimamedia complex and intramural shear strain profoundly increased (median 190%, range 102-296%, and median 141%, range 101-182%, respectively, compared with baseline), also when given during ␤-blockade (median 228%, range 133-266%, and median 158%, range 152-235%, respectively). During infusion of low-dose epinephrine, the longitudinal displacement of the intima-media complex and intramural shear strain decreased (median 88%, range 69 -122%, and median 69%, range 47-117%, respectively, compared with baseline). In conclusion, the present study shows, for the first time, that the longitudinal displacement and intramural shear strain of the porcine carotid artery undergo profound changes in response to catecholamines. Increase in longitudinal displacements seems to be strongly related to ␣-adrenoceptor activation. Thus metoprolol is insufficient to counteract a profound increase in longitudinal displacement and intramural shear strain following a surge of norepinephrine. longitudinal movements; epinephrine; norepinephrine; metoprolol; vascular mechanics; ultrasound CARDIOVASCULAR DISEASE IS a leading cause of morbidity and mortality in the industrialized countries. Mental stress is considered a risk factor for cardiovascular disease both acutely, following strong emotional stress, and chronically. The mechanisms behind this association still remain unclear.In cardiovascular research, the radial movement of the arterial wall, the diameter change, has been the subject of extensive research; measurement of the diameter change of arteries is now an established tool in cardiovascular research (2,21,26), forming the basis for estimation of arterial wall stiffness. Increased stiffness of large central arteries has been shown to be an independent risk factor for cardiovascular mortality (5, 19). In contrast, there are few studies on the longitudinal movement of the arterial wa...

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“…2). The administration of an alternative drug to induce hypertension may have induced larger longitudinal strains than Phenylephrine, since arterial longitudinal motion has showed to increase in response to catecholamines [16]. However, the inner-most layer of the artery wall showed to increase more in longitudinal motion than the adventitia, resulting in an increased longitudinal shear strain.…”

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“…We also found that the outer part of the arterial wall, the adventitial region, in these arteries exhibit the same basic pattern of longitudinal movement, but the magnitude of movement is smaller than that of the intima-media complex, thereby indicating the presence of previously unknown substantial shear strain and, thus, shear stress intramurally (Cinthio et al 2006). In addition, we found that the major circulating hormones that play a role in vascular tone, adrenaline and noradrenaline, can dramatically increase longitudinal movement ), suggesting that the longitudinal movement can be a missing link between mental stress and cardiovascular disease (Ahlgren et al 2012b). It has been hypothesized that the pattern and/or magnitude of longitudinal arterial wall movement can be used as a biomarker for cardiovascular disease (Ahlgren et al , 2012a(Ahlgren et al , 2012bCinthio et al 2006;Svedlund and Gan 2011a;Svedlund et al 2011;Zahnd et al 2011Zahnd et al , 2012a.…”

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“…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. Studies have indicated that the maximal amplitude of the longitudinal displacement of the common carotid artery is reduced in subjects with cardiovascular risk factors [23], and suspected and manifest atherosclerotic disease [24,25].…”