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Page 2 of 14 Squizzato et al. Vessel Plus 2023;7:16 https://dx.doi.org/10.20517/2574-1209.2023.05

provides low invasiveness, a low rate of perioperative complications, and satisfactory early and mid-term
results, and is accepted as a first-line option for the treatment of descending thoracic aneurysms, acute
[1,2]
aortic syndromes, and aortic traumatic injuries, in the presence of a suitable anatomy . One of the main
drawbacks of the endovascular treatment is that approximately 10%-20% of patients receiving TEVAR may
still require a reintervention during the long-term follow-up, mainly related to proximal endograft failure
[3,4]
leading to a type Ia endoleak .
Both the technical success and the long-term durability of TEVAR may depend on a proper selection of an
adequate proximal sealing zone. The instructions for the use of currently available thoracic endografts
recommend a proximal sealing length (PSL) of at least 2 cm. However, this may be controversial, as there
are many clinical, anatomical, hemodynamic, pathological, and procedural factors that may interact and
should be considered during the choice of the proximal sealing zone. This narrative review aims to
summarize the current knowledge on the factors that may influence the decision-making of the proximal
sealing length during the endovascular planning of TEVAR, in order to optimize the clinical outcomes after
thoracic endografting. In literature, aorta-related mortality after TEVAR varies upon the treated pathology,
specifically, 9.7% in blunt aortic trauma, 5.57% in elective aneurysm repair, 19% in ruptured aneurysm
repair, 2.6%-9.8% in acute type B aortic dissection, and 4.2% in chronic type B aortic dissection .
[2]

ANATOMICAL AND HEMODYNAMIC FEATURES
Classification of proximal landing zones
The aortic landing zones used during endovascular repair are classically described by Ishimaru’s anatomical
classification. This divides the aorta into consecutive segments primarily in relation to the emergence of
aortic side branches. Zone 0 includes the ascending aorta to the innominate artery (IA), zone 1 from the IA
to the left common carotid artery (LCC), zone 2 from LCC to the left subclavian artery (LSA), zone 3 goes
from the origin of LSA to the proximal thoracic descending aorta (2 cm), zone 4 from 2 cm below the LSA
to the mid portion of the descending thoracic aorta (usually identified by the level of the 6th thoracic
vertebrae), and zone 5 from the mid-thoracic aorta to the origin of the celiac artery [Figure 1]. The need to
[5]
reach a 2 cm-long proximal sealing may often require landing in the aortic arch (zones 0-3) . In recent
years, the endovascular approach has become more aggressive, and extension in the arch (after a surgical
supra-aortic vessels debranching) enables the expansion of the indication for thoracic endovascular repair
to patients with an unsuitable proximal landing zone below the LSA .
[6]
Classification of the aortic arch anatomy
The aortic arch is characterized by a complex curved anatomy and tortuosity along the three spatial planes.
The direct geometrical consequence is that the length of endograft-to-wall apposition, which reflects the
actual ability of sealing, is usually shorter along the inner curvature of the arch compared to the outer
[8]
curvature but it can also be anterior, posterior or cranial, depending on the tilt of the endograft . An
[7]
excessive aortic curvature may be responsible for the so-called bird beak configuration, which occurs when
the endograft does not adapt to the inner curve of the aorta and leads towards the outer curve, leaving a
triangular-shaped gap between the stent-graft and the aortic wall [Figure 2], that is associated with type Ia
endoleaks . Also, aortic curvature is associated with inaccurate deployment at the intended landing zone,
[9]
incomplete endograft apposition to the aortic wall, and wedge apposition [10-12] .

Aortic arch anatomy can be classified into three types based on its angulation and the take-off distribution
of the supra-aortic trunks (SAT) [Figure 3]. Type I aortic arch is characterized by the three SATs originating
in the same horizontal plane as the outer curvature of the arch. In type II aortic arch, the IA originates
between the horizontal planes of the outer and inner. In type III aortic arch, the IA originates below the