https://orcid.org/0000-0002-1272-7990
Abstract
Conventional treatment for type A aortic dissection includes replacement of the ascending aorta with an open distal anastomosis in the hemiarch position. The frozen elephant trunk (FET) is a hybrid technique that extends the repair to the descending thoracic aorta. The goal is to improve resolution of malperfusion syndrome and to induce positive aortic remodelling and reduce the need for reintervention on the downstream aorta. We aim to summarize the data on the short and long-term outcomes of this technique.
A thorough search of the literature was conducted isolating all articles dealing with aortic remodelling after the use of FET in case of type A acute aortic dissection. Keywords ‘aortic dissection’, ‘frozen elephant trunk’, ‘aortic remodelling’ and ‘false lumen thrombosis’ were used. Data for type B and chronic aortic dissections were excluded.
FET use favourably influences aortic remodelling. The main advantages lie in the exclusion of distal entry tears in either the aortic arch or descending aorta thus restoring antegrade blood flow in the true lumen and inducing false lumen thrombosis. False lumen thrombosis is not only induced at the level of the stent deployment but also lower in the distal descending aorta. Moreover, it offers an adequate landing zone in the mid-descending aorta for second-stage endovascular or open surgical aortic repair, if needed.
FET can be advantageous in the treatment of acute type A aortic dissection dealing with extended aortic pathology.
INTRODUCTION
Acute type A aortic dissection (ATAAD) is a life-threatening condition [1], where an emergent life-saving surgical intervention is required. Ascending aorta and hemiarch replacement are indispensable parts of the conventional operation to reestablish true-lumen perfusion [2]. Optimization of surgical techniques and perioperative care has led to improved outcomes over the last decades [3], with a perioperative mortality of below 15% [2]. Although simple ascending aortic replacement may be acceptable in the emergent ATAAD setting [4], a residual dissected downstream aorta with a patent false lumen (FL) is present in up to 90% of survivors after conventional surgery for ATAAD, which has a negative impact on long-term prognosis [3].
A patent FL is associated with an increased risk of late aortic growth resulting in higher reoperation rates and reduced long-term survival [2, 3]. Approximately 15–50% of residual DeBakey type I AD will develop chronic aneurysm formation of the downstream aorta [5]. Reinterventions are not benign; open repair for both chronic dissections and non-dissected thoraco-abdominal aortic aneurysms in high-volume centres have a 30-day mortality rate of 5–8%. Paraplegia risk ranges between 6 and 8% [6–9], and up to 25% of patients will experience renal complications. Outside of high-volume centres, mortality approaches 22.3%, whereas postoperative complications occur in >55% of cases [10]. Endovascular repair of chronic thoraco-abdominal dissections also carries significant risk, with early mortality rates of up to 7.5% and neurologic complication rates between 0 and 9% [11].
Consequently, an alternative operative strategy that can promote FL thrombosis and positive remodelling at the time of the initial ATAAD repair is required [3]. Single-stage treatment of extensive thoracic aorta disease via the frozen elephant trunk (FET) technique, first described in 1996 [12] appears to be a choice. Endovascular and conventional surgery benefits are combined and an appropriate landing zone for possible second-stage downstream endovascular or open repair is achieved [13, 14]. The main goal of FET is the exclusion of a primary intimal tear in the distal arch or proximal descending thoracic aorta (DTA), or distal re-entry tears, thus improving distal true lumen (TL) perfusion [1, 15, 16] and promoting aortic remodelling in the downstream thoraco-abdominal aorta [1, 16]. Therefore, FET use potentially obviates subsequent reinterventions, while providing an optimal substrate for subsequent endovascular or open repair if needed [14]. However, there are limitations to the FET approach. FL thrombosis and positive remodelling are commonly restricted to the stent graft level within the first year [5, 15] and little is known about the remodelling process of the aorta distal to the stent graft [16]. During follow-up, negative remodelling requiring further intervention to prevent rupture is reported in 20% to 38% of patients. Therefore, continued imagine surveillance is still necessary after FET for ATAAD. Spinal cord injury (SCI) after FET is also greater than the conventional approach [5].
In this review, we aim to cover the evidence supporting FET use in ATAAD, outline limitations of this approach and recommend specific scenarios where FET should be considered.
FET AND AORTIC REMODELLING DEFINITION
FET includes the hybrid replacement of the entire aortic arch from the innominate artery to a point beyond the left subclavian artery via a single prosthesis consisting of a conventional graft replacing the aortic arch along with a stent graft antegrade deployed within the proximal descending aorta. The subsequent step of reimplanting the supra-aortic branches can be performed in different ways either as an island technique or as individual arch vessels reimplantation [17].
Aortic remodelling is the term introduced by Iafranesco et al. to qualify the surgery outcomes after aortic dissection [13, 18]. Aortic remodelling reflects the diameter or volume changes of the TL and FL over the length of the dissected aorta [19]. Positive remodelling indicates either TL expansion or FL reduction in maximal diameter or volume provided that total aortic diameter or volume remain unchanged, or total maximal aortic diameter reduction. Aortic true lumen ratio (TLR) dividing the TL diameter by the total aortic diameter at the narrowest level of the aortic TL of the descending aorta has also been recommended to describe aortic remodelling. In this case, increased postoperative TLR indicates positive aortic remodelling [20].
According to the Society of Vascular Surgeons/Society of Thoracic Surgeons reporting standards document [19], the rule of 10% threshold to define significant changes, as introduced by Dohle et al., is recommended [13] and aortic remodelling is classified into 3 groups: positive, stable and negative. Therefore, TLR increase >10% with stable aortic lumen (AL) or AL decrease >10% with stable TLR are considered positive remodelling, whereas changes within 10% threshold are typical of stable remodelling. A significant increase in the diameter of the AL or a significant decrease in the diameter of the TL shows negative remodelling [16].
However, there is a risk of misinterpretation of aortic remodelling using the above definitions. Although one may observe positive changes within 1 part of aorta, there may still be negative changes within downstream distal aortic zones [19]. To address this, diameters are commonly measured at 3 or 4 different levels of the descending thoraco-abdominal aorta: mid-DTA at the level of pulmonary artery bifurcation (usually covered by the stent graft), distal DTA around the level of the diaphragm where the aorta is usually not covered by the stent graft, abdominal aorta at the level of coeliac trunk and distal abdominal aorta below the renal arteries [14, 21].
Finally, a complete assessment includes commentary on the remodelling status in the context of FL thrombosis and reintervention [16]. FL thrombosis is described as patent, partially thrombosed or completely thrombosed for each one of the aforementioned levels [14, 21]. Overall, positive aortic remodelling is defined as no need for reintervention on the downstream aorta, absence of total diameter progression and FL stabilization with at least partial thrombosis [14].
NATURAL HISTORY OF DOWNSTREAM AORTA POST-CONVENTIONAL APPROACH
After isolated ascending aorta with or without hemiarch replacement for type A aortic dissection, up to 40% of patients may require a second-stage operation for increased aortic dilatation of the downstream aorta during the first 5 postoperative years [22–24]. The cumulative risk of reintervention via a redo sternotomy or left thoracotomy significantly impairs long-term mortality and morbidity [25].
The need for reoperation depends on distal FL patency. Up to 90% of the cases receiving conventional treatment for DeBakey I AD have persistent patent FL postoperatively [15]. Pressurization of the remaining FL results in downstream aorta dilatation. There are many mechanisms involved including untreated distal re-entry tears around the visceral branches and iliac arteries, re-entry tears from dissected arch branch vessels, untreated primary intimal tears distal to the replaced aortic segment or new iatrogenic entry tears at the level of the anastomosis [23], the so-called distal anastomotic new entry tear (DANE) [25]. More than 70% of patients will experience a DANE after hemiarch replacements thus leading to negative aortic remodelling [26]. Pressurization of the FL due to antegrade pulsatile flow occurs post-DANE formation [25]. According to Rylski et al. [26] studying post-hemiarch repair patients who experienced an ATAAD and diagnosed with negative aortic remodelling, 95.6% of the cases had a DANE.
Moreover, postoperative descending aortic diameter over 4 cm, even in the absence of FL patency is an independent predictor of >10 mm increase in the aortic diameter thus negatively impairing aortic remodelling [27]. An initial FL diameter of 22 mm or more is also identified as an independent risk factor for aortic disease progression [28]. According to Leontyev et al. [29], 38% of patients with postoperative residual aortic diameter over 40 mm required reoperation on the residual dissected distal aorta.
GOALS OF THE FROZEN ELEPHANT TRUNK
The consensus document published by the European Association of Cardiothoracic Surgery (EACTS) [30] considers the use of FET in 4 different scenarios. First, in case of acute type A AD with a primary entry tear either in the distal aortic arch or in the proximal descending aorta to treat malperfusion syndrome or to avoid its postoperative development; second, in complicated acute type B AD when there is inadequate landing zone for primary thoracic endovascular aortic repair (TEVAR) or retrograde type A AD risk is high; third, in extensive thoracic or thoraco-abdominal aortic disease when a second-stage procedure in the downstream aorta is predicted. Finally, it is also recommended in case of type A AD to prevent midterm aneurysmal degeneration of the downstream aorta [1, 30]. Recognizing a descending aortic diameter over 40 mm as a risk factor for aortic-related reoperation possibly justifies the application of FET in case of greater descending aortic diameter to timely prevent negative aortic remodelling [29]. An aortic diameter increase over 10 mm [27], as well as an initial FL diameter over 22 mm [28] also independently predict aortic disease progression thus making space for possible FET application to interrupt the negative remodelling process [29]. Similarly to the EACTS consensus document, the most recent EACTS/STS guidelines for the aortic organ recommend emergent FET use for acute dissections in case of an entry tear at the outer curvature of the aortic arch or within 10 mm distal to the left subclavian artery making the anatomy hostile for TEVAR. Finally, whenever a one-stage aortic arch treatment is intended, current European guidelines are in favour of FET technique [17].
The main advantage of the FET in the treatment of AD is the exclusion of the distal entry tears in either the aortic arch or descending aorta, restoring antegrade blood flow in the TL and inducing FL thrombosis by decreasing FL pressure [1, 31]. Moreover, lower body and visceral malperfusion syndromes related to TL collapse can be resolved by FET [32]. Arch branch re-entry tears are resolved through reimplantation of these branch vessels. Furthermore, FL perfusion from DANEs is minimized [1, 31], thanks to the circumferential suture line of FET at the level of distal arch [16]. The suture line is supported by the TEVAR which would also seal any DANEs that could be present [25]. It is reported that more than 90% of FET cases will achieve FL thrombosis with subsequent shrinkage at the stent graft level [16]. Therefore, positive aortic remodelling is promoted, achieving improved freedom from reintervention rates [1, 13, 22]. Overall, FET extensively deals with the aortic pathology via a thorough single-step procedure [32].
However, there are cases when complete FL thrombosis is not achieved despite FET use because of continuing FL perfusion via distal reentry tears. Continuing perfusion of the FL leads to increasing FL pressurization and subsequently increased wall tension which may result in aneurysm expansion and rupture. FL patency is a significant independent predictor of long-term mortality and aortic events, whereas partial FL thrombosis is not associated with the long-term mortality. As a result, a post-FET second-stage repair may still be required in the long term [22]. Hereby, FET provides an extra advantage by offering an optimal landing zone in the mid-descending aorta for endovascular repair and facilitates open second-stage aortic repair as well [32, 33].
The subsequent sections will detail the evidence behind the purported goals of FET during the treatment of ATAAD: promoting FL thrombosis, minimizing distal aortic malperfusion, preventing future aortic reoperation and optimizing long-term survival [34].
FALSE LUMEN THROMBOSIS OF THE DOWNSTREAM AORTA
Current literature reveals that FET is extremely effective in triggering FL thrombosis in the DTA, but less effective as far as the abdominal aorta is concerned [13]. Complete FL thrombosis in the abdominal aorta is prevented from perfusion of the FL through the visceral, renal and lumbar branches coming of it [35]. There are large series that have quantified rates of FL thrombosis, Sun et al. reported the largest experience on aortic dissections treated with a stented elephant trunk in a total of 291 patients. The prevalence of FL thrombosis at follow-up after acute dissections was 94.2% and only 1 patient required a second-stage aortic reintervention for thoraco-abdominal aortic replacement [36]. Encouraging results had been published from Cleveland Clinic as well [37]. A modified hybrid approach has been applied since 2009 including FET along with a fenestration in the proximal stent graft level in type I DeBakey AD. Complete thrombosis rate of 66.7%, with 25.4% partial thrombosis rate and only 7.9% FL patency rate of the treated segment have been reported throughout the 28 ± 25 months median follow-up. As a result, 14 completion reinterventions including 7 TEVAR extensions were performed [37]. Similarly, 90% of patients reported to have complete or partial FL thrombosis by Di Bartolomeo et al. [38] A metanalysis containing 15 studies that involved 1279 patients shows similar results; FL thrombosis rate was 96.8% (95% confidence interval, 90.7–98.9%) [39]. These results are by far better than the FL thrombosis rate ranging from 33.3 and 77.8% of cases after conventional surgical management. However, FL thrombosis at the level of the abdominal aorta is much lower occasionally requiring further management [40].
But even concerning the distal to the stent graft aorta where lower FL thrombosis rates are reported, FL thrombosis is significantly higher than the preoperative value up to the level of the coeliac artery [13]. Dohle et al. [15] reported increasing FL thrombosis rates 2 years postoperatively reaching 87% at the level of the coeliac trunk and 54% at the distal abdominal aorta. Moreover, extending a FET with a thoracic stent graft implanted down to the downstream aorta is associated with even higher FL thrombosis rate at the thoracic level but not in the abdominal segment [33, 35].
There is also a study supporting the use of provisional extension to induce complete attachment (PETTICOAT) technique with a bare metal stent for FET extension in case of either acute or chronic AD. Although no significant postoperative abdominal FL thrombosis was immediately observed, patients who received the PETTICOAT technique achieved increasing abdominal thrombosis rates throughout a year of follow-up [5]. Previous studies studying the impact of the PETTICOAT technique only in cases of acute and subacute AD reported significantly higher FL thrombosis rates with perfect regression in both thoracic and abdominal segments even immediately postoperatively [5]. In case of AD, FL patency is associated with negative remodelling at all aortic levels, apart from the distal abdominal aorta [13]. The absence of complete FL thrombosis and subsequent FL pressurization is a predictor of subsequent aortic dilatation and late mortality [33].
Apart from FL patency, other risk factors for postoperative adverse events and mortality include an initial DTA diameter >35 mm, an initial FL diameter ≥22 mm and a large (>10 mm) proximal intimal tear. However, although FET is sometimes ineffective to address the entire AD pathology at one stage, it facilitates endovascular second-stage reintervention in the downstream thoraco-abdominal aorta [1].
AORTIC REMODELLING
Positive aortic remodelling at least in the proximal part of the thoracic aorta after FET is generally reported in the literature with statistically significant TLR expansion and FL ratio reduction [18].
Iafrancesco et al.’s multicentre international study including 383 patients treated for either acute or chronic AD with FET detected no differences in terms of postoperative AL diameters among acute and chronic AD cases in their at least 1-year follow-up CT scan. No increase was detected at the level of the stent graft, whereas the lumen was stable just below it and it increased distally. Both groups showed stable distal abdominal AL diameters when FL was thrombosed and increased distal AL diameter when FL was patent. Additionally, the stability of the AL in the thoracic aorta even despite FL patency may reveal that reduced movement of the dissection flap after stent deployment in the TL results in lower pressure pulsatility in the FL preventing the latter from expansion. As far as the TL diameter is concerned, TL was increased at all levels in cases of ATAAD when FL was patent, whereas it was increased proximally and remained stable when FL was thrombosed in the ATAAD group [13].
However, there are studies generally showing favourable overall remodelling in case of acute compared to chronic AD [18]. Dohle et al. revealed positive or stable remodelling in all aortic segments investigated in more than 60% of acute AD cases after the first post-FET year. 92%, 65% and 62% of the patients revealed positive or stable remodelling along the stent graft aortic segment, downstream to coeliac trunk and distally to aortic bifurcation respectively. Positive or stable remodelling was also statistically significant correlated with FL thrombosis in all 3 levels of the aorta studied. Moreover, when positive or stable remodelling was found at the level of the coeliac trunk, this was associated with positive or stable remodelling of the distal abdominal aorta as well. No patient demonstrated negative remodelling in all 3 segments of the aorta investigated, whereas persistent negative remodelling in >2 aortic levels was found in 19% of the patients after the first year of follow-up [16].
ZONE OF IMPLANTATION AND ‘ELONGATED’ FET
The remodelling of the aorta is also associated with length of the graft and the localization of the FET anastomosis. However, more proximal anastomosis of the FET seems to be related to better results. Surgical and ischaemic time are reduced, and postoperative morbidity and mortality are decreased, but FL thrombosis rates are lower compared to more distal zones of the anastomosis [40, 41].
Small retrospective series, like the one published by Panfilov et al. showed that there are not statistically significant differences found in the early outcomes related to morbidity and mortality, however, FL thrombosis post-FET anastomosis in zone 2 was 60% compared to 77% related to zone 3 anastomosis (P = 0.046) at 24 months follow-up. Subsequently, higher reintervention rates were also reported after proximalization of the distal anastomosis (25.9 vs 8.3%, respectively) [41]. Therefore, it can be concluded that failure of FL thrombosis may be related to reduced length of coverage of the thoracic aorta.
Other multicentric studies have indirectly addressed this question. Berger et al. [42], during the evaluation of the early and mid-term outcomes of 2 different FET prostheses, concluded that at 1-year follow-up one of the prosthesis showed a significantly reduced rate of secondary aortic interventions (22% vs 0%; P = 0.003) and a trend towards a higher rate of FL thrombosis (74% vs 95%; P = 0.085) and these differences are attributed to a longer coverage of the descending aorta due to a longer stent graft and a more frequent implantation in zone 3.
Extending a FET with a thoracic stent graft implanted down to the coeliac artery, the so-called elongated FET had shown better results but not statistically significant in cumulative survival 100% vs 72% (P = 0.29), freedom from negative remodelling 80% vs 67.5% (P = 0.58) and distal aortic reintervention 100% vs 75% (P = 0.61) at 5 years [35]. Reintervention could be either endovascular or open. Even in the case of open repair, the remaining disease may be transformed into a Crawford-Type IV pathology, significantly simplifying possible third-step intervention, as there is no need for 1 lung ventilation throughout the operation and the operative time is significantly shortened [43].
The choice of FET length may also impact the incidence of distal stent graft-induced new entry (dSINE), with shorter graft lengths associated with increased dSINE in small series [44]. dSINE leads to FL patency and subsequent negative aortic remodelling, and it is provoked by the continuous motion of the distal intimal lamella during the cardiac cycle. The PETTICOAT technique seems advantageous. When a completion bare metal stent is deployed in the downstream aorta, better support of the TL with subsequent immobilization of the intimal lamella can be achieved. Moreover, spinal cord ischaemia is less possible when an uncovered stent is used and additional stenting of malperfused aortic branches originating from the FL is also facilitated thanks to the realignment of the intimal ostia of dissected branches after TL re-expansion [45].
Patients having experienced aortic dissection are in need for continuous follow-up for disease progression to be regularly reassessed [46]. Hopefully, in case of negative aortic remodelling requiring completion procedure, FET offers an optimal landing zone for either endovascular or surgical stage II thoraco-abdominal repair [24, 46]. The most common indications for TEVAR completion are downstream aorta continuing dilation, planned completion for an extensive aortic pathology or a newly diagnosed dSINE after FET [46].
FREEDOM FROM REINTERVENTION
More and more evidence show that FET promotes TL expansion and FL obliteration. As a result, fewer stage II reinterventions are required [18]. Distal aortic reintervention depends on FL status and its correlation with aortic remodelling [4, 35]. Negative remodelling due to FL patency distal to the stent graft is a risk factor for reintervention [4]. Negative remodelling in at least 2 different aortic levels is related to reintervention requirement distal to the stent graft. Up to 20% of AD and 40% of CAD cases remain at risk for distal stage II reintervention [16]. From 16% to 26% of post-FET patients will require distal reintervention via either a left thoracotomy or resternotomy post-FET, when FL remains patent [35]. According to Chen et al. [47], freedom from distal aortic reoperation at 10 years was significantly higher in patients with a completely and partially thrombosed FL in the descending aorta compared to a patent FL (89.2% vs 64.6%, P < 0.001), as well as in those with a preoperative maximum descending aorta diameter <40 mm (86.3% vs 63.9%, P < 0.001).
As mentioned before, there are technical amendments during FET implantation having an impact on reintervention risk. Performing the distal anastomosis in proximal zones of the aorta has better surgical exposure and makes the procedure easier [40–42], whereas shorter stent grafts are more commonly adopted to avoid the detrimental complication of spinal cord ischaemia. However, both surgical amendments lead to FL patency and higher aortic reintervention rates [40–42, 44].
SPINAL CORD INJURY PREVENTION
SCI is a detrimental complication that can happen after dealing with aortic pathology. After FET, 4.7% incidence of SCI is reported in a large metanalysis [48]. Multiple factors can trigger SCI including low intraoperative and postoperative blood pressure, prolonged circulatory arrest time, long stent coverage, atheromatous emboli of the spinal cord artery and aortic pathology [49]. The atherosclerotic aorta is more intense negative predictive factor than postoperative FET status [50]. Despite the different postoperative and preoperative care, the length of the graft is also considered a risk factor to develop SCI. The optimal length of FET is still debated; a delicate balance between adequate aortic length coverage to achieve FL thrombosis and minimal occlusion of spinal arterial branches must be achieved [51]. There is no established consensus regarding the distal landing zone of the FET. Prevetza et al. reported higher spinal cord ischaemia event rates when longer than 15-cm-long graft was used or when FET was deployed below T8 level compared to 10-cm-long FET grafts (11.6% vs 2.5%, P < 0.001) [48]. Fewer thromboembolic complications is another advantage to using shorter FET grafts [52]. On the contrary, other series have not found increased incidence of SCI in T8–T9 [33] or further in T10–T12 [53]. An alternative approach to minimize SCI risk, is to complete a zone 2 arch replacement as popularized by the Penn group, which allows for selective stent graft deployment at a later stage, effectively completing an FET repair in 2 stages [46].
Whenever TEVAR extension is needed after FET (or zone 2 arch), this is optimally performed at least 14 days after FET implantation. This allows the patient enough time for the creation of collateral network that allows spinal cord perfusion. Other preventive measures to keep FET extension safe include regulating CSF pressure via spinal drain insertion, antegrade cerebral perfusion with a flow rate of 8–10 ml/kg/min, elevating arterial perfusion pressure at 60–80 mmHg and maintenance of postoperative mean arterial pressure at 80–100 mmHg, assuring an adequate haemoglobin level over 25% and serial postoperative neurological examination [35, 43, 49].
SURVIVING THE SHORT TERM TO TAKE ADVANTAGE OF FROZEN ELEPHANT TRUNK
FET is per se a more complex operation than hemiarch replacement including total arch replacement by definition with subsequent reimplantation of the supra-aortic vessels [17]. Short-term results after FET are decent according to a large systematic review by Tian et al. [51] including 37 studies with 4178 patients mainly focused on acute dissections. As far as FET in acute aortic dissection cases (1801 cases) are concerned, mortality, stroke, SCI and acute kidney injury rates were 9.4%, 4.7%, 2.6% and 10.5%, respectively [51]. Moreover, both techniques FET and the conventional one require total circulatory arrest. Finally, similar perioperative mortality and neurologic risks are reported according to a multicentre Canadian registry analysis comparing perioperative outcomes of patients with ATAAD after hemiarch replacement with those after extended aortic arch repair [54].
CONCLUSIONS
In overall, despite some potential pitfalls, there are significant advantages accompanying FET use. FET technique can achieve a durable treatment at least up to the mid-descending aorta in ATAAD [16]. Aortic remodelling is a significant indicator of patients’ prognosis after FET [40]. The use of FET favourably influences aortic remodelling, inducing FL thrombosis not only at the level of the stent deployment but also lower at the distal descending aorta (central image). As a result, FET can be a definitive treatment in case of AD [14]. However, its positive remodelling effect is weaker in the distal abdominal aorta. FL status and timing of presentation impair TL diameter changes [13]. Therefore, distal aortic completion reinterventions may be required. FET stent graft serves as an optimal landing zone for TEVAR completion in the remaining downstream aorta up to the level of the coeliac trunk with very good postoperative outcomes (central image) [43, 46]. The elongated FET with TEVAR extension can further trigger FL thrombosis and subsequently improve remodelling of the thoracic aorta [35] without increasing the risk of SCI [33]. Finally, even in case that this 2-stage-approach is not sufficient to deal with the whole aortic pathology, a third thoraco-abdominal aortic replacement may be required which will also be simpler given the distal shift of the anastomosis (central image) [43]. However, given the advanced complexity of FET procedure, we should always keep in mind that, most importantly, the patient should stay alive postoperatively. Surviving the short term is the only way to take profit of the long-term advantages of the FET related to better aortic remodelling. Therefore, FET is an advantageous technique that should be selectively applied in high-volume centres by experienced aortic surgeons to achieve optimal results along with low morbidity rates.
FUNDING
No funding was received.
Conflict of interest: none declared.
DATA AVAILABILITY
No new data were generated or analysed in support of this research.
Author contributions
Nikolaos A. Papakonstantinou: Conceptualization; Data curation; Formal analysis; Investigation; Methodology; Project administration; Resources; Software; Validation; Visualization; Writing—original draft; Writing—review & editing. Daniel Martinez-Lopez: Data curation; Formal analysis; Investigation; Methodology; Resources; Validation; Visualization; Writing—original draft. Jennifer Chia-Ying Chung: Formal analysis; Project administration; Supervision; Validation; Visualization; Writing—review & editing.
Reviewer information
European Journal of Cardio-Thoracic Surgery thanks Martin Grabenwöger and the other anonymous reviewers for their contribution to the peer review process of this article.
REFERENCES
ABBREVIATIONS
- AL
Aortic lumen
- ATAAD
Acute type A aortic dissection
- DANE
Distal anastomotic new entry tear
- DTA
Descending Thoracic Aorta
- dSINE
Distal stent graft-induced new entry
- EACTS
European Association of Cardiothoracic Surgery
- FET
Frozen elephant trunk
- FL
False lumen
- PETTICOAT
Provisional extension to induce complete attachment
- SCI
Spinal cord injury
- TL
True lumen
- TLR
True lumen ratio
- TEVAR
Thoracic endovascular aortic repair
