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Page 2 of 16 Trahanas et al. Vessel Plus 2022;6:49 https://dx.doi.org/10.20517/2574-1209.2021.125

chronic aortic dissections that involve the aorta distal to the left subclavian artery (type B).

In the past, open surgical management was the treatment of choice when intervention was required for
chronic type B aortic dissections (CTBAD). In 1999, endovascular stent grafting was first reported as a
therapy for this disease process. Since then, thoracic endovascular aortic repair (TEVAR) has become an
important component in the management of CTBAD, either as a stand-alone therapy or combined with
[1,2]
open surgery in a hybrid manner . Life-long clinical and imaging surveillance of patients with known
aortic dissection is necessary to identify those who may require intervention to prevent aortic catastrophe,
as well as to monitor for complications after a successful repair. In this manuscript, we will review the
classification, natural history, and imaging strategies for CTBAD, as well as describe the options available
for intervention to address these lesions.

CHRONIC TYPE B AORTIC DISSECTION
Anatomic classification
The original classification system proposed by DeBakey in 1965 was based on the longitudinal extent of the
anatomic involvement. A type I dissection involved the ascending aorta and descending aorta. A type II
involved the ascending only. A type IIIA involved only the descending thoracic aorta, while a type IIIB
[3]
involved both the thoracic and abdominal aorta distal to the left subclavian artery . The more commonly
used classification system is the Stanford Classification developed in 1970, in which dissections that involve
the ascending aorta are grouped as type A, and those not involving the ascending aorta are grouped as type
[3]
B . This classification system gained popularity over the DeBakey classification due to its simplicity and its
use in the International Registry of Acute Aortic Dissections (IRAD) database . However, the Stanford
[4]
system lacks a description of the longitudinal extent of the dissection and details about the location of the
entry tear. Furthermore, neither classification scheme addresses dissections that originate in the arch.

Because the management of dissection differs greatly depending on the location of the entry tear, it is
important to have an accurate classification scheme. For this reason, in 2020, the Society for Vascular
Surgery (SVS) and The Society of Thoracic Surgeons (STS) issued a reporting standards document to clarify
how lesions should be classified . Per this consensus, the distinction between type A and type B dissection
[3]
is predicated solely on the site of the entry tear. Any entry tear originating in Zone 0 of the aorta is a Type
A , with a subscript numeral designating the distal extent of the dissection. Any dissection with entry tear in
#
zone 1 or beyond is a type B with two subscript numerals: the first designating the proximal extent of the
#,#
lesion (e.g., retrograde involvement of the ascending), and the second numeral designating the distal extent
of the dissection [Figure 1]. If there is zone 0 involvement, but the location of the primary entry tear cannot
be determined, then it is type I indeterminate, with the subscript numeral again designating the distal
#
extent.

Chronologic classification
The reporting standards document issued by the SVS/STS also clarifies the way the chronicity of dissection
is classified. This new classification system incorporates data from both IRAD as well the European Society
of Cardiology. Dissections are considered: hyperacute, < 24 hours; acute, 1 to 14 days; subacute, 15 to 90
days; and chronic, > 90 days . Of note, the definition of acute and chronic dissection has changed over
[3]
time, and many studies in the literature published prior to this new classification will term dissections > 2
weeks from the inciting event as chronic . Thus, it is important to clarify how the term chronic was
[1,4]
defined when comparing studies.