A Systematic Histopathologic Evaluation of Type-A Aortic Dissections Implies a Uniform Multiple-Hit Causation

Figure 1. Ratio dissection plane. Transverse histologic sections of the ascending aorta 4 µm stained with MOVAT pentachrome staining. (A) Overview ascending aorta I = intima, m = media, a = adventitia. (B) 1: Lamina elastica interna (LEI), 2: dissection plane (DP), and 3: lamina elastica externa (LEE). (C) 4: Distance between LEI and DP, 5: distance between LEI and LEE. Ratio dissection plane is defined as distance 4 divided by distance 5.

Figure 2. Ratio vasa vasorum. Transverse histologic sections 4 μm stained for CD31 (A,B,E) and MOVAT (C,D) in a control patient (A–E). A shows an overview of the ascending aorta, with the dashed lines indicating the lamina elastica interna (LEI), with a detailed view of the LEI in B in a CD31 stained section and in C in a MOVAT stained section. The second dashed line (A) indicates the lamina elastica externa (LEE), with a detailed view in the MOVAT stained section (D). The asterisk indicates the nearest vasa vasorum (A,E). The ratio of the vasa vasorum is calculated by dividing the distance between LEI and nearest vasa vasorum (indicated by 1 in A) by the distance between LEI and LEE (indicated by 2 in A). The location of the dissection plane is shown on the left and the vasa vasorum on the right in graph F. Each triangle and asterisk (F) represents one TAAD patient. The red line represents the median location of the dissection plane, and the green line represents the median location of vasa vasorum. The dashed lines are the borders between the inner, middle, and outer media.

Figure 3. Graph of median morphology scores comparing the dissection and control group. Boxplot of median morphological scores comparing the dissection and control group. Boxes represent median morphological score (bold horizontal lines) and interquartile ranges (75%; 25%). Extremes are presented as asterisks. Blue corresponds to the dissection group and red to the control group. EFF/L: elastic fiber fragmentation/loss; EFT: elastic fiber thinning; EFD: elastic fiber degeneration; OMD: overall medial degeneration; MEMA: mucoid extracellular matrix accumulation; SMCNL: smooth muscle cell nuclei loss.

Figure 4. Intimal thickness. Transverse histologic sections (4 μm) stained for Resorcin Fuchsin (RF), Haematoxylin Eosin (HE), and MOVAT. The intimal layer, indicated with the dashed line, is significantly thinner in the dissection group (a patient without Marfan or a bicuspid aortic valve) (A–D) than in the control group (E–H) (Graph I). Magnification (A,E) 1.5×, (B–D,F–H) 11.5×, *: p < 0.05.