Ascending aortic aneurysm (AAA) is strongly associated with aorticadverse events (AAEs) such as aortic rupture, coarctation, and death.The 2022 American College of Cardiology/American Heart Association (ACC/AHA) Guidelines for the Diagnosis and Treatment of Aortic Disease state that The 2022 American College of Cardiology/American Heart Association (ACC/AHA) Guidelines for the Diagnosis and Treatment of Aortic Disease state that AAA prophylactic intervention is indicated for diameters ≥5.5 cm, or 5.0 cm in combination with connective tissue disease, rapid diameter growth, or other risk factors; however, most AAEs occur at diameters <5.5 cm, which has been viewed as the “aortic paradox” [1-3]. The Yale team concluded that the indication for AAA preventive intervention should be “shifted left” to 5 cm [4]. However, the controversy is that the risk of surgical death is higher at this indication than the annual risk of AAEs (2.0% vs. 1.4%).

In recent years, superior predictors of efficacy over diameter have been developed, including the aortic dimensional index, diameter-height index, aortic height index, and ascending aortic length [5-9].Wu et al [10] concluded that ascending aortic morphology can vary considerably, even when aortic diameter and length values are similar. In contrast, aortic volume, as a three-dimensional property index, has the dual advantage of simultaneously evaluating the hemodynamic status of AAA (transverse) and the mechanical stress on the aortic wall (longitudinal), which helps to accurately predict the risk of AAEs. With the increasing research in fluid dynamics and biomechanics, the wall stress rupture potential index, numerical prediction of wall stress, severity parameter, and finite element analysis rupture index have begun to be used for risk prediction of ruptured abdominal aortic aneurysms [9,11-14]. However, considering the complexity of the proximal structure of the ascending aorta, the relevant indices still need to be validated in AAA.

Frozen elephant trunk stent technique (FET) has been gradually and widely used in the surgical treatment of type A aortic dissection (TAAD), which can effectively seal the primary breach, expand the true lumen, and promote the remodeling of the false lumen. The 9-year follow-up of 518 cases of acute TAAD in Beijing Anzhen Hospital showed that the false lumen closure rate of the descending aorta by Sun's procedure reached more than 95% [15,16]. Although the FET technique greatly simplifies the complexity of surgical operation, even in large cardiac centers with mature experience, the FET technique still inevitably involves systemic hypothermia and circulatory arrest during distal open anastomosis. There are three core variables for organ protection during intraoperative maneuvers: optimal core temperature, time to circulatory arrest, and cerebral perfusion at the time of circulatory arrest [17].

The more commonly used perfusion modalities in clinical practice include: deep hypothermia to stop circulation, deep hypothermia to stop circulation combined with retrograde cerebral perfusion, and moderate hypothermia to stop circulation accompanied by cisplaced cerebral perfusion [18]. Among them, moderate hypothermia combined with unilateral cisplaced cerebral perfusion is considered to be the safest strategy for circulatory management [19]. Large randomized controlled studies are still needed in the future to provide high-quality looking medical evidence to prove the optimal intraoperative core temperature and perfusion strategies. In addition, domestic and international researchers have favored changing the FET design or combining different perfusion modalities to break through the bottleneck of the current technology, using intra-balloon block [20-22], extra-stent vessel block [23], triple-branched stent vessels [24], and a new sutureless integrated stent vessel [25] to increase the core temperature and shorten distal anastomotic stoppage of the circulatory time, or simplifying distal anastomosis by using cutting anastomoses [26]. The above innovative technologies and novel vessels still need to be objectively evaluated using the GRADE EtD framework as a criterion to prove the practical value through extensive clinical studies. In addition, well-constructed open implantable vessels should have the advantages of easy release without increasing technical complexity; good flexibility, conforming to the aortic curvature and having a tapered distal end; a biocompatible surface with minimal blood permeability; and a distal anastomosis that facilitates secondary interventions [27].

The endoluminal repair technique is an alternative for high-risk patients when surgical treatment is not available. Previous studies concluded that endoluminal repair was previously thought to be unable to be applied in this segment of the aorta due to the structural complexity of the aortic root and ascending aorta.In 2014, Rylski et al[28] proposed an interventional device for aortic valve combined with ascending aortic replacement to break this technical bottleneck, but anatomical feasibility of this technique in the past was usually below 40%. In China, Prof. Guo Wei's team changed the design concept of the previous aortic root mesh structure and innovatively proposed a modular Endo-Bentall stent system with a fully coated structure, including a stent with two internal branches, two coronary reconstruction stents, and an interventional aortic valve with a connecting segment stent [29]. The operation was performed to reconstruct the ascending aorta, coronary arteries, aortic root and valve sequentially from distal to proximal. The anatomical applicability is increased to 66.4% and is more suitable for TAAD patients with intimal tears in the aortic root. The system is designed to allow for the internal branches required for coronary reconstruction, ensuring adequate myocardial perfusion during the operation. The modular combination avoids the drawbacks of customized stents and solves the problem of individualization. In the future, it is hoped that prospective cohort studies or randomized controlled studies will demonstrate the efficacy and safety of this stent system. Nowadays, the practical clinical application of the Endo-Bentall concept is still less reported, but the short-term therapeutic effect is more favorable [30-32]. Theoretically, Endo-Bentall will benefit more patients with TAAD. On the other hand, the use of Endo-Bentall has been reported to be not rigorous, and some of the cases were actually Endo-Wheat surgery, which should be strictly subclassified and the use of related academic terms should be standardized in the future.

In the 2022 ACC/AHA Guidelines for the Diagnosis and Treatment of Aortic Disease, open surgical repair of thoracoabdominal aortic aneurysm (TAAA) is a Class I recommendation, and endoluminal stent repair is only a Class IIb recommendation [33]. However, a German study found that the volume of endoluminal treatment for TAAA increased by 70% in ten years and the in-hospital mortality rate was much lower than that of open surgery (10.6% versus 23.9%) [34]. Beginning in the 1990s, clinical specialists used reinforced open or directional branching stents. Currently, the technique has evolved from the use of physician-modified endoluminal stents to individualized finished endoluminal stents. One study showed that open branch endoluminal repair reduced early overall mortality to 6.5% [35]. Despite technological advances, the intercostal arteries may have the disadvantage of not being able to be reconstructed by endoluminal treatment due to technical and anatomical limitations, which has raised concerns that extensive aortic coverage may increase the risk of spinal cord injury (SCI). The incidence of SCI has been reported to be 9.6% after open repair of TAAA [36] and 8% with endoluminal treatment [37]. Conventional monitoring and protection strategies such as motor evoked potentials, somatosensory evoked potentials, and cerebrospinal fluid drainage could not significantly improve the incidence of SCI [38]. Currently, in this regard, Etza et al [39] found that the intercostal segmental vessels are not the only arteries supplying the spinal cord, and their surrounding vascular plexus forms a dynamic blood supply mechanism. When the segmental arterial blood supply is insufficient, the collateral blood supply increases, which explains to some extent the failure of segmental vascular perfusion alone to reduce the incidence of SCI. Therefore, the concept of “minimally invasive staged segmental arterial coil embolization (MIS2ACE)” has been proposed for the initiation of the paraspinal collateral branch network prior to open or endoluminal TAAA repair to prevent postoperative SCI [40]. Animal experiments demonstrated good prognostic results [41], which is currently being studied in a multicenter randomized controlled trial (RCT) study with a total of 9 countries and 17 cities participating in the study [42], which, combined with noninvasive real-time monitoring of paraspinous muscle oxygenation by near-infrared spectroscopy, holds the promise of advancing the birth of new spinal cord protection strategies in the future.