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Di Marco et al. Vessel Plus 2020;4:32 I http://dx.doi.org/10.20517/2574-1209.2020.23 Page 5 of 7

We prefer to use the Thoraflex graft when the arch vessels originate widely separately from each other or
when they are severely dissected.

[10]
As already suggested by Tsagakis , we routinely use angioscopy both to analyze the anatomy of the aorta
before graft deployment, and to verify afterwards the correct positioning and expansion of the stent-graft.

DISCUSSION
FET technique is an elaborate procedure aimed to simplify the treatment of complex thoracic aortic lesions,
which combines the classic elephant trunk technique features with the endovascular stent technology.
The evolution from the classic ET to FET started at the end of the 1990s, with the “open stent-grafting
[2-4]
technique”, combining antegrade endovascular stenting with classic arch repair . This technique was then
modified by the Hannover group, with the development of a custom-made hybrid prosthesis, giving birth
[5]
to the “Frozen Elephant Trunk” technique . Over the last few years, hybrid prosthesis technology has
evolved, until the latest introduction of branched grafts in 2012.

Outcomes of FET procedure are variably reported in the literature. In the previous EACTS 2015 position
statement on the use of FET technique, analyzing data extracted from 97 focused publications available
[11]
in the literature, in-hospital mortality rates of 1.8% to 17.2% have been described . Similarly, Ma and
colleagues showed an early mortality rate of 6.4% to 15.8% in a review article .
[12]
Mortality and complication rates of FET procedure are comparable to those of classic aortic arch surgery,
except for spinal cord injury (SCI), with variable rates from 0% to 21% as reported in the EACTS 2015
position statement. The most recent single-centre experience report by Shrestha and colleagues showed an
[13]
in-hospital mortality of 11% (12% in acute type A aortic dissection) and a 2% incidence of SCI . Higher
rates of SCI are found in patients who underwent FET procedure due to chronic aortic dissection .
[11]
Presumably, the mechanisms involved in the pathophysiology of SCI are coverage of descending thoracic
aorta beyond T7-T8 level, longer spinal cord ischemia times, and thromboembolic events. We therefore
assume that the incidence of SCI could be reduced with a shorter descending aorta coverage and spinal
cord ischemia time, in addition to the validated use of CSF drainage, which we strongly recommend.

In acute and chronic aortic dissection, FET technique promotes flow restoration in the true lumen,
coverage of the proximal entry and re-entry tears and thrombosis of the false lumen, either partial or
complete. On this regard, the Essen group reported rates of false lumen thrombosis of 90% in acute
[13]
aortic dissection and 78% in chronic dissection . This induces positive aortic remodeling, with a drastic
reduction of the risk of aneurysmal dilatation and rupture. Nonetheless, complete thrombosis of the false
lumen could be the trigger for visceral ischemia when the visceral arteries originate from the false lumen
and there are no re-entry tears located in the distal aorta. Therefore, our opinion is that FET procedure
should be contraindicated in absence of re-entries in the distal thoracic, thoracoabdominal, and abdominal
aorta when the visceral vessels originate from the false lumen.

In conclusion, FET technique represents a safe and effective procedure for the treatment of complex
descending thoracic aortic lesions, allowing a one-stage repair and, when necessary, endovascular extension
with a secure proximal landing zone. Early and late outcomes have been improving thanks to novel
technologies and standardization of the surgical approach.

OUR “IDEA” ABOUT FET
Our experience with the FET technique started with the use of Jotec E-vita open prosthesis, but some years
later, in 2014, we added the Thoraflex hybrid prosthesis to our “armamentarium”. With the introduction of