Segmental Arterial Mediolysis With Accompanying Venous Angiopathy: A Clinical Pathologic Review, Report of 3 New Cases, and Comments on the Role of Endothelin-1 in Its Pathogenesis

Abstract

The authors review 20 cases of segmental arterial mediolysis (SAM) including 3 newly reported cases. SAM developed in areas of vascular distention in 2 of the latter cases: 1 in utero in the heart of a recipient of a twin transfusion syndrome and the other in the jejunum secondary to partial venous obstruction. In the third case, it occurred in a patient with Raynaud disease. Characterizing SAM are injurious and reparative lesions that occur in the media and/or at the adventitial medial junction. Four distinctive alterations are recognized: (1) mediolysis, (2) a tearing separation of the outer media from adventitia, (3) arterial gaps, and (4) a florid reparative response that replaces zones of mediolysis and fills areas of medial adventitial separation. The repair can transform SAM into lesions indistinguishable from common types of fibromuscular dysplasia (FMD.) A venous angiopathy involving large and medium-sized veins accompanies SAM. It features medial muscle vacuolar change with lysis leading to apparent separation of residual muscle bundles. Immunostaining shows endothelin-1 (ET-1) decorating adventitial capillaries in SAM and neighboring arteries, in capillaries of adjoining tissues, and outlining smooth muscle cell membranes in adjacent veins including those of the venous angiopathy. The significance of these changes is uncertain. Vasospasm is believed to cause SAM, but ET-1 is not the direct pressor agent responsible for this condition. The reason(s) for synthesis and release of ET-1 in SAM are still hypothetical, but local perturbations in vascular tone may be an important factor. ET-1 may be indirectly play a role in SAM by cross-talking and potentiating the activities of other vasoconstrictors such as norepinephrine and by orchestrating its reparative phase.

Pathomorphometry of ruptured intracranial vertebral arterial dissection: adventitial rupture, dilated lesion, intimal tear, and medial defect

“…We speculated that medial defects, which resemble the vascular lesions found in patients with segmental arterial mediolysis, play a key role in the occurrence of intracranial VA dissections. 11,12 Segmental arterial mediolysis is usually found in abdominal arteries; 14 however, recently, segmental arterial mediolysis has been reported in intracranial arterial dissections with and without small arterial dissections in abdominal arteries. 4,13,18 We reported on cases of segmental arterial mediolysis affecting both the intraabdominal and intracranial VAs.…”

A Patient with Acute Kidney Pain and High Blood Pressure

“…Classically, FMD presents more commonly in middle-aged women and has a predisposition for the renal arteries, thereby causing premature hypertension (10). SAM may be a subclinical process, and silent cases with small or absent gaps and no dissection may evolve into FMD because fibrosis of the reparative granulation tissue can metamorphose into lesions identical to medial fibroplasia or perimedial dysplasia (the two most common forms of FMD) (11,12). The frequent involvement of renal arteries in SAM may be congruent with the notion that this is an evolving process in which patients initially present with vascular lesions with aneurysms and dissections consistent with SAM and that these lesions evolve and become fibrotic and stenosed over time, which is more consistent with FMD.…”

Segmental arterial mediolysis with mesangial cell hyperplasia; A review with supplementary comments concerning its pathogenesis

“…The figures utilized in this article are derived from the multiple cases of SAM reported by the authors in references [1][2][3][4][5][6][7][8][9][10]. Their journal origins are listed in the figure descriptions.…”

“…These stem from the florid proliferating granulation tissue that mends the arterial lesions created in the injurious phase-the shearing lesion formed at the adventitial-medial junction and media muscle loss created by mediolysis or apoptosis. Reparative changes create Review Article Slavin, Leifsson sequelae-dissecting hematomas, arterial stenosis and thrombosis, persistent aneurysms and if extensive fibromuscular dysplasia [2][3][4][5][6]. Significant hemorrhages can also occur in the reparative phase originating from dissecting hematomas but this event may be delayed for months to two or more years after the onset of SAM and have been provoked by the misplacement of stents into stenotic arteries [7].…”