Aortic dissection (AD) is a disease in which blood breaks through the intima and enters the middle layer of the aortic wall, tearing the aortic wall into two inner and outer layers [1]. once AD develops, the risk of wall rupture leading to death is extremely high. From the perspective of guiding treatment, the staging of AD is mainly based on Stanford criteria and can be divided into Stanford type A, in which AD involves the ascending aorta regardless of the extent of distal involvement, and Stanford type B, in which AD involves the left subclavian artery (LSA) to the distal descending aorta [2].The management of AD is based on surgical treatment, and the traditional In 1998, Dake first reported the use of thoracic endovascular repair (TEVAR) for the treatment of type B AD. The concept of TEVAR for AD is to apply a stent graft (SG) to close the endovascular rupture within the vessel and prevent the high-pressure, high-speed blood flow from rushing into the false lumen, resulting in thrombosis and gradual repair of the tear in the false lumen. More than 10 years of experience and follow-up results have confirmed the technical feasibility, minimal trauma, and efficacy of TEVAR in the treatment of type B AD [4-6]. The main problem that limits TEVAR is the lack of an adequate anchoring zone (LZ), which is defined as the distance between the AD opening (tear) and the branch artery opening. For example, the proximal LZ refers to the distance between the breach and the opening of the branch artery on the arch (mainly LSA), and the distal LZ refers to the distance between the breach and the opening of the visceral artery (VSA), which is generally required to be greater than 1.5 cm to ensure effective repair [7]. Recent advances in expanding the LZ include the following: application of Hybrid technique (including Debranch technique); application of open-window (fenestrated) or branching (branched) SG; application of chimney technique (chimney). 1.Hybrid technique Hybrid technique means hybrid technique. By definition, hybrid technique refers to the treatment of vascular disease through a combination of surgical treatment and endoluminal repair techniques. In the treatment of AD, the main purpose of hybridization is to extend the LZ by traditional surgical methods.The current widely used field is to extend the proximal LZ as much as possible by reconstructing the blood flow to fully ensure the cephalad blood supply.According to the zoning method proposed by Ishimaru et al [8], the aortic arch is divided into four zones, Z0, Z1, Z2 and Z3 (Figure 1). According to the different zones in which the AD rupture occurs, different strategies are adopted to apply hybridization techniques to expand the LZ. 1.1, Rupture located in Z3 zone When the AD rupture is located in Z3 zone, the length of the LZ is the distance from the rupture to the LSA. If the right vertebral artery is the dominant artery and the intracranial Willis ring is intact, the LZ can be obtained by directly covering the LSA, but when the following conditions exist: (1) the left vertebral artery is the dominant artery; (2) the Willis ring is incomplete; (3) the coronary artery relies on the left internal mammary artery for blood supply after CABG; (4) there is ipsilateral internal carotid artery occlusion relying on posterior circulation compensation, the LSA needs to be reconstructed before covering the LSA. reconstruction in order to cover the LSA to obtain an adequate proximal LZ [9]. A common approach is the left common carotid artery (LCCA)-LSA bypass. Reconstruction of the LSA helps to more adequately seal the lesion and reduce type I endoleak (endoleak). Type II endoleak may result from proximal LSA regurgitation and can be eliminated by proximal ligation of the LSA or blocker embolization. When the LCCA and LSA are in close proximity, the proximal LZ is still insufficient even after covering the LSA; or when the proximal breach is located in the Z2 zone and the distance between the LCCA and the LCCA is less than 1.5 cm, the LCCA needs to be reconstructed to obtain sufficient LZ. Depending on whether the LSA needs to be reconstructed, the common bypass methods are right common carotid artery (RCCA)-LCCA (Figure 2) and RCCA-LCCA-LSA bypass, etc. When the rupture is located far from the LCCA, but the distance between the innominate artery (INA) and the LCCA is very close, even if the LSA and LCCA are covered, a satisfactory proximal LZ cannot be obtained; or when the rupture is located in the Z1 area and the distance between the RCCA and the RCCA is less than 1.5 cm, it is necessary to reconstruct the RCCA blood flow to One way to expand the proximal LZ in this case is to use the Debranch technique (debranching technique). The procedure requires a median sternotomy, but without the assistance of extracorporeal circulation, and a “partial block” technique [10] is used to anastomose the proximal end of the bifurcated artificial vessel to the lateral wall of the ascending aorta and the distal bifurcation to the INA and LCCA, respectively, with or without reconstruction of the LSA depending on the preoperative assessment. The custom-made prosthetic vessel can have a temporary “leg” attached to its proximal end to allow for direct downstream introduction of the SG to repair the AD after the reconstruction (Figure 3). When the patient is in poor systemic condition and cannot tolerate open thoracic surgery, or when a healthy segment of the ascending aorta is not available for partial block, the LZ can be expanded by means of a right iliac to right axillary, left iliac to left common carotid, and left axillary artery artificial vessel bypass. the problem with this completely extra-anatomic approach to reconstruct cephalad vessels is that it may not have the same long-term patency as the intra-anatomic open-chest Debranch technique [11]. 1.4, Rupture located in the Z0 zone When the rupture is located in the Z0 zone, AD is classified as Stanford type A. If the AD rupture is located in the ZO zone, but there is sufficient distal LZ between the LSA and the LSA, the LSA-LCCA-RCCA bypass can be performed first, followed by implantation of a short SG through the femoral artery access to cover the INA and LCCA, preserving the LSA, repair the lesion. In China, Chang Guangqi et al [12] reported that two cases of type A AD were cured by this method with good results. 2. Application of open-window and branching SG The concept of open-window SG is to reserve or preoperatively cut out side holes on the artificial vessel membrane of SG according to the specific situation, so that the proximal part with membrane after SG release exceeds the opening of branching vessels but the blood flow of the vessel can be preserved through the side holes. A common approach is to prep or cut a scalloped or horseshoe-shaped side hole in the proximal portion of the SG membrane. The advantage of proximal side holes is that they are relatively easy to locate and can be easily remedied by retracting the SG if a branch artery is mistakenly covered, but the disadvantage is the limited expansion of the proximal LZ. Guo inland Qing-sheng et al. reported the successful application of the above method of open-window SG in repaired AD while preserving the LSA [13]. Another method is to reserve or cut out a lateral hole in the middle of the SG artificial vascular membrane, thus allowing a greater degree of LZ expansion, with the disadvantage that it is difficult to position and difficult to remedy and adjust once the SG band membrane partially covers the branch vessels. In China, Zhao B et al [14] reported the successful repair of a ruptured aortic arch lesion by applying this method in combination with INA-LCCA bypass surgery. In my clinical work, the author has also experienced three cases of successful expansion of the proximal LZ through the windowing technique. However, the disadvantage of cutting out the lateral hole preoperatively is that it may have an effect on the firmness of the SG, thus shortening the life of the SG. The concept of branched SG is a conventional SG with a side branch that preserves branch arterial vascularity. SGs with one branch and SGs with three branches are common and are mainly used in lesions involving the aortic arch. Single-branch SGs preserve the blood supply of one branch artery on the arch, usually the LSA, thus allowing the proximal LZ to be expanded by a completely intraluminal approach without sacrificing the LSA. single-branch SGs are relatively less difficult to perform, and Saito N et al [15] used single-branch SGs to repair AD or TAA involving the LSA starting in 1999, treating 17 patients, all of whom underwent successful surgery. The short- and medium-term follow-up was satisfactory, with no lesion- or treatment-related fatalities. Specially designed single-branch SGs can also be used to preserve the blood supply to the INA while reconstructing blood flow to the LCCA and LSA by bypass surgery. Guo Wei et al. reported [16] a case of type A AD with retrograde tear after TEVAR, in which an RCCA-LCCA-LSA bypass was performed in stage I. In stage II, the SG was delivered to the ascending aorta via the RCCA, with a short branch extending into the INA and the main body located in the arch, and then another straight SG delivered via the femoral artery was docked to the main body of the previous SG to repair the lesion. Inoue et al [17] successfully treated a case of type A AD in 1999 by implanting SGs with three branches to reconstruct the INA, LCCA, and LSA, respectively, and to extend the proximal LZ and repair the aortic arch lesion using SGs with branches. The advantages of using SG with branches to expand the proximal LZ and repair aortic arch lesions are that it can avoid opening and clamping the aorta and reduce surgical trauma. Chuter et al [18] concluded that the complexity of the operation and the risk of cerebral infarction would increase significantly with the implantation of more SG branches. 3. chimney technique The chimney technique, or Chimney technique, involves releasing a laminated stent or bare stent parallel to the SG through the branch artery in the aorta, with one end in the aorta and one end in the branch vessel, thereby preserving blood flow in that branch [19]. the Chimney technique is effective in expanding the proximal LZ and can be applied in thoracic aortic TEVAR preservation of the INA or LCCA [20]. Usually, the delivery system of the overmolded or bare stent is pre-delivered to the target location, then the SG is introduced and fully released, followed by the release of this overmolded or bare stent. With the chimney technique, the SG can be released beyond the LSA or LCCA opening while preserving the LSA or LCCA blood supply, thus allowing expansion of the LZ (Figure 5). chimney technique was first proposed by Greenberg et al [21] in 2003 and was initially applied to preserve the renal artery in the repair of proximal aneurysms with insufficient neck, and then gradually applied Sugiura K et al [19] reported 11 patients who used the chimney technique during TEVAR for thoracic aortic disease, of whom 3 had preserved INA, 7 had preserved LCCA, and 1 had preserved LSA by chimney. There were two cases of proximal endoleaks, one case was treated by traditional surgical methods after surgery, and one case was followed up. The chimney technique can also be applied to salvage LCCAs that have been mis-capped. The author had encountered a case of AD with a short proximal LZ and intraoperative release of SG to cover half of the LCCA, but the aortic arch morphology was inconsistent with the preoperative contrast due to the introduction of super stiff guidewire, and the LCCA pulsation was found to disappear after SG release. The LCCA was urgently dissected and the ascending aorta was selected through the gap between the SG and the apex of the arch, and one smart-control stent was released from the LCCA to the ascending aorta, and the LCCA blood supply was successfully restored by the chimney technique (Figure 6). Most of the proximal breaches in AD are located near the aortic arch, so these technical methods mentioned above are mainly applied to expand the proximal LZ. However, in some cases of AD, the rupture is located in the distal part of the descending aorta adjacent to the opening of the visceral artery, and in this case, the distal LZ also needs to be expanded by the above-mentioned methods. The CA and SMA often emanate at an acute angle from the abdominal aorta, so if one tries to implant a chimney stent from the distal abdominal main, one is that the stent may break due to the compression of the SG, and the other is to reverse the direction of blood flow, so the chimney technique is more convenient in this case. At this time, it is more convenient to enter from the upper extremity. The open-window and branching SGs, on the other hand, can be tried here for suitable cases [22]. These aforementioned technical approaches have largely expanded the indications for TEVAR procedure, allowing more patients to have access to minimally invasive treatment. They each have their own advantages and disadvantages and scope of application, and in the course of clinical practice, it is necessary to reasonably adopt the appropriate method according to the patient’s specific situation and the operator’s experience to achieve the goal of improving the therapeutic effect while minimizing the trauma and complication rate.