Insights From the Histopathologic Analysis of Acquired and Genetic Thoracic Aortic Aneurysms and Dissections

Fig. 1. Representative photomicrographs show mild, moderate, and severe medial degeneration in histologic sections stained with hematoxylin-eosin (A, C, E) and Verhoeff–van Gieson elastic tissue stain (B, D, F). A) Mild medial degeneration exhibits a mild increase in basophilic intralamellar MEMA (arrow) in a section stained with hematoxylin-eosin and (B) the mild loss of elastic fibers (arrow) in a section stained with elastic tissue stain. C) Moderate medial degeneration shows a multifocal increase in intralamellar MEMA (arrow) and (D) multifocal attenuation of elastic fibers (arrow). E) Severe medial degeneration exhibits multifocal translamellar MEMA (arrow) and (F) multifocal translamellar loss of elastic fibers (arrow). Each scale bar represents 100 μm; original magnification for all images is ×50. MEMA, mucoid extracellular matrix accumulation.

Fig. 2. Representative photomicrographs show the severity of medial degeneration in a patient with documented Marfan syndrome and type A aortic dissection compared with the severity of medial degeneration in a patient with sporadic type A aortic dissection with hematoxylin-eosin stain (A, C) and with Verhoeff–van Gieson elastic tissue stain (B, D). A) In the patient with Marfan syndrome, the outer and inner media adjacent to the dissection plane show abundant MEMA (arrow; ×50) and (B) extensive loss of elastic fibers (arrow; ×50). C) In the patient with sporadic aortic dissection, the outer and inner media adjacent to the dissection plane show minimal MEMA accumulation (×150) and (D) attenuation of elastic fibers (×150). Each scale bar represents 100 μm. MEMA, mucoid extracellular matrix accumulation.

Fig. 3. Histopathologic grading of medial degeneration is shown for 86 patients with thoracic aortic aneurysm and aortic dissection. Overall medial degeneration was significantly different between hereditary and sporadic aortopathy groups, with the hereditary group typically having higher severity levels than the sporadic group (P = .004). Significant differences were observed between the hereditary and sporadic aortopathy groups regarding the extent of elastic fiber fragmentation (P = .03) and translamellar MEMA (P = .04), with both being more severe in the hereditary aortopathy group. The medial degeneration score was not significantly different between patients with type A aortic dissection and with nondissected aortic aneurysms, but the medial degeneration score was significantly lower for patients with BAV than for patients with TAV (P = .03). P < .05 was considered statistically significant. BAV, bicuspid aortic valve; MEMA, mucoid extracellular matrix accumulation; TAV, tricuspid aortic valve.