Histomorphometric and sympathetic innervation of the human internal thoracic artery

Abstract

INTRODUCTION:Internal thoracic artery (ITA) is an established arterial graft for the coronary artery by‐pass surgery. Special micro‐anatomical features of the ITA wall may protect it from age related pathological changes. One of the complications seen after coronary artery bypass grafting is vasospasm. Sympathetic nerves may be involved in vasospasm.OBJECTIVE:To ascertain the sympathetic innervation of the internal thoracic artery and to assess the effect of aging on this artery by histomorphometry.METHOD:Fifty‐four human internal thoracic artery samples were collected from 27 cadavers (19 male and 8 female) with ages of 19 to 83 years. Samples were divided into three age groups: G1, 19–40 years; G2, 41–60 years; G3, ≥61 years. Sections (thickness 5 µm) of each sample were taken and stained with hematoxylin–eosin and Verhoeff–Van Gieson stains. Five of fifty‐four samples were processed for tyrosine hydroxylase immunostaining.RESULTS:The thickness of the tunica intima was found to be constant in all age groups, whereas the thickness of the tunica media decreased in proportion to age. Verhoeff–Van Gieson staining showed numerous elastic laminae in the tunica media. Significant differences (p<0.0001) in the number of elastic laminae were found between G1 with G2 cadavers, between G2 and G3 cadavers and between G3 and G1 cadavers. Tyrosine hydroxylase immunostaining demonstrated sympathetic fibers, located mainly in the tunica adventitia and the adventitia–media border. The sympathetic nerve fiber area and sympathetic index were found to be 0.0016 mm2 and 0.012, respectively.DISCUSSION:Histology of the ITA showed features of the elastic artery. This may be associated with lower incidence of Atherosclerosis or intimal hyperplasia in ITA samples even in elderly cases. Low sympathetic index (0.012) of ITA may be associated with fewer incidences of sympathetic nervous systems problems (vasospasm) of the ITA.CONCLUSION:Sympathetic nerve fibers are present in the adventitia of the internal thoracic artery. This is an elastic artery, although anatomically it is considered to be medium‐sized. The sympathetic index may be used for analysis of sympathetic nerve fiber‐related problems of the internal thoracic artery.

Cardiology in Brazilian scientific journals: an overview

“…They concluded that preoperative peptide levels > 502 ng/ml predict mid-term mortality after isolated coronary artery bypass grafting and are associated with significantly higher hospital mortality and perioperative complications. Reddy et al [4] analyzed the sympathetic innervation of the internal thoracic artery to assess the effect of aging on this artery by histomorphometry using 54 human internal thoracic artery samples collected from 27 cadavers (19 male and 8 female) with ages of 19 to 83 years. Sympathetic nerve fibers are present in the adventitia of the internal thoracic artery.…”

Influence of spontaneously occurring bursts of muscle sympathetic nerve activity on conduit artery diameter

“…All muscular arteries appear to exhibit the necessary machinery (i.e., sympathetic perivascular nerves, ␣-adrenergic receptors, etc.) to participate in sympathetic vasoconstriction (11,16,18,28,29,33). Nevertheless, an overwhelming amount of evidence demonstrates that small arteries and arterioles actively respond to all levels of sympathetic activity, whereas it appears that only large reflex-mediated increases in MSNA and infusion of adrenergic agonists raise conduit artery tone (3,23,25,40).…”

“…muscle sympathetic nerve activity; blood pressure; large artery vasoconstriction SYMPATHETIC VASOCONSTRICTION is most effective in altering blood flow and blood pressure (BP) by influencing small arteries and arterioles (16, 18). However, conduit arteries also exhibit sympathetic perivascular nerve innervations (11,15,28,33), express ␣-adrenergic receptors (11, 29, 33), and significantly vasoconstrict in response to ␣-adrenergic agonists (3, 40). Indeed, the majority of evidence (2,4,6,23,25,26) suggests that large reflex-mediated increases in muscle sympathetic nerve activity (MSNA) decrease conduit artery diameter, although a few reports indicate only minimal changes (6, 30).…”

“…However, conduit arteries also exhibit sympathetic perivascular nerve innervations (11,15,28,33), express ␣-adrenergic receptors (11,29,33), and significantly vasoconstrict in response to ␣-adrenergic agonists (3,40). Indeed, the majority of evidence (2,4,6,23,25,26) suggests that large reflex-mediated increases in muscle sympathetic nerve activity (MSNA) decrease conduit artery diameter, although a few reports indicate only minimal changes (6,30).…”

Abnormal origin of internal thoracic artery from the thyrocervical trunk: surgical considerations

“…This anatomically medium-sized artery receives sympathetic fibers in its adventitia [28] and has routinely been harvested as a suitable conduit for the myocardium ischaemia relief, showing an increased patency compared to the saphenous vein grafts [34]. During CABG surgery it is important to reassure the conduit length, course, and mobility within the surrounding structures in order to prevent traction and angulation [4].…”