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Rinaldi et al. Vessel Plus 2024;8:21 https://dx.doi.org/10.20517/2574-1209.2023.65 Page 3 of 19

Similarly, in the past, aortic dissections were divided into acute (occurring within 2 weeks of the onset of
symptoms) and chronic (occurring more than 2 weeks after symptom onset). Additionally, acute type B
aortic dissections (aTBAD) were traditionally classified as complicated or uncomplicated;major
complications included impending rupture and malperfusion. Distinguishing between complicated and
uncomplicated aTBAD holds significance in terms of prognosis, with reported in-hospital mortality rates of
18%-50% for complicated cases compared to only 1.2%-10% for uncomplicated cases [10-12] . Aortic rupture is
associated with high mortality regardless of the treatment type, while visceral ischemia, present in 7%-8% of
aTBAD cases, is another devastating complication and the leading cause of death, accounting for 15% of
mortality [13-15] . Therefore, timely diagnosis is crucial to improve survival chances.

In terms of clinical management, traditional strategies involving surgical intervention and medical therapy
dictate distinct approaches for complicated and uncomplicated aTBAD cases. However, advancements in
our understanding of the disease and the emergence of endovascular techniques have sparked a re-
evaluation and debate regarding all aspects of the previously used TBAD classification. This includes a
rethinking of what constitutes an “uncomplicated” patient with aTBAD. As a result, numerous position
papers have been published, and new classifications have recently been proposed to better evaluate
therapeutic options and predict outcomes. The Society for Vascular Surgery/Society of Thoracic Surgeons
(SVS/STS) has put forth a different temporal classification for aortic dissection, which is outlined in
[16]
Table 1 .
The TEM classification, introduced by the group of Czerny, provides a detailed description of aortic
dissection based on the Type of dissection (T), the location of the Entry tear (E), and the presence of
Malperfusion (M). This classification is outlined in Table 2 . In addition to the widely recognized Type A
[17]
and Type B dissections, the TEM classification introduces a distinct category known as “non-A-non-B”.
This category describes a dissection with involvement of the proximal aortic arch but without extension into
the ascending aorta.

Recently, Lombardi et al. introduced a new classification in the SVS reporting standards for TBAD. This
classification considers clinical signs and radiographic features to divide patients with aTBAD into three
categories: uncomplicated, complicated, and high-risk. The details of this classification are outlined in
[16]
Table 3 .

The new classification proposed by Lombardi et al. incorporates the clinical presentation of patients. In this
classification, uncomplicated patients are characterized by the absence of rupture and/or end-organ
malperfusion. On the other hand, complicated patients are those who exhibit rupture and/or malperfusion
affecting organs such as the kidneys, viscera, limbs, or spinal cord. It should be noted that aTBAD without
immediate rupture or malperfusion may still pose a significant risk of subsequent complications. Factors
such as aortic diameter exceeding 40 mm, diameter of the proximal entry tear exceeding 1 cm, as well as
clinical features like persistent pain and hypertension, are now recognized as potential causes of late
complications. As a result, a new group has been introduced in the classification called “high-risk” patients,
who exhibit these specific characteristics [Figure 1].
[16]

A significant update introduced by the new classification proposed by Lombardi et al. is the incorporation
of a modified anatomical classification. This classification considers the location of the proximal entry tear,
as well as the proximal and distal extensions of the dissection. While this classification offers exceptional
accuracy in describing the anatomical characteristics of the dissection, its adoption in urgent or emergent
[16]
settings remains limited due to the preference for simpler classifications .