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Trahanas et al. Vessel Plus 2022;6:49 https://dx.doi.org/10.20517/2574-1209.2021.125 Page 3 of 16

[3]
Figure 1. SVS/STS guidelines on anatomic reporting of dissections from Lombardi et al. (with permission). SVS: Society for Vascular
Surgery. STS: The Society of Thoracic Surgeons.

Distinguishing the chronicity of dissection can sometimes be aided by cross-sectional imaging. Typical
features of a more acute process on CT include periaortic confluent soft tissue opacity, and a curved and
mobile dissection flap . Features more suggestive of a chronic dissection include a thick flap, false lumen
[5]
outer wall calcification and thrombus, false lumen dilatation, and tear edges curling in to the false lumen .
[5]
Figure 2 demonstrates the changing pathology of aortic dissection in a patient longitudinally over 4 years .
[6]
Natural history
Type B dissections represent 25%-40% of all dissections . The leading cause of death in patients with acute
[4]
[7]
type B dissection is aortic rupture, and the second leading cause of death is malperfusion . Fortunately, 91%
of patients with acute Type B aortic dissection will survive the initial event. Of these survivors, 66% will have
an initially uncomplicated course with proper medical management (see Medical Management). While not
all will require intervention, 60% of survivors will develop late aneurysmal dilation of the affected
segment(s) of the aorta over the next five years . This dilation tends to predominantly affect the upper
[8]
descending thoracic aorta adjacent to the primary tear but can affect the abdominal and visceral segments as
well . Dissected descending thoracic aortas tend to grow at a rate faster than aneurysms of the ascending
[7]
[9]
and abdominal aorta. Additionally, the greater the size of the aorta, the faster it grows . As with
atherosclerotic aneurysms, size plays a major role in the risk of rupture. Aneurysmal dilation > 6 cm carries
a yearly rupture rate of 6.9%, and repair should be considered as this size is approached . Once 7 cm in size
[10]
[9]
is reached, the lifetime rupture risk is 43% .
The growth of a CTBAD can vary from 0.1 cm to 0.7 cm per year but is strongly dependent on the initial
aortic size and control of hypertension . Despite optimal medical management, at least one-third of
[9]
patients will require surgery for aortic-related complications within five years of the dissection event, with
the greatest risk being in the first few months .
[2]

After an intervention on CTBAD, positive or negative aortic remodeling can be detected with imaging.
Positive aortic remodeling in a segment of the aorta is defined as any one of the following: reduction in false
lumen diameter/volume with no change in total aortic diameter/volume; true lumen diameter/volume
expansion with no change in total aortic diameter/volume; or total aortic maximal diameter reduction with
variable changes in true and false lumen diameters. Negative aortic remodeling would represent the