The concept of thoracic endovascular repair (TEVAR) for aortic dissection (AD) is to apply a stent graft (SG) to close the endovascular breach (tear) within the vessel and prevent the high-pressure, high-speed blood flow from rushing into the false lumen, thereby allowing the false lumen to The thrombus is formed and the wall tear is gradually repaired. Since Dake first reported the use of endoluminal repair for type B AD in 1998 [1], TEVAR has been widely performed worldwide, and more than 10 years of experience and follow-up results have confirmed the technical feasibility, minimal trauma, and efficacy of TEVAR for type B AD [2-7]. The successful performance of TEVAR requires a sufficient length of normal vessel wall proximal and distal to the breach to ensure adequate apposition of the SG to it, which is defined as the landing zone (LZ), including the proximal and distal LZ, The proximal LZ refers to the distance between the rupture and the opening of the superior arch artery (mainly the left subclavian artery (LSA)), while the distal LZ refers to the distance between the rupture and the opening of the visceral artery (VSA), which is generally required to be greater than 1.5 cm to ensure effective repair [8]. TEVAR therapy. In recent years, two main strategies have been used to expand the LZ: first, the application of new endoluminal repair devices; second, the application of new surgical techniques. New intracavitary devices can preserve the blood supply of branch arteries while ensuring adequate therapeutic effect, including the application of blockers, fenestrated and branched SGs. Blockers Blockers are intracavitary repair materials with a dumbbell-like structure and a fluid-impermeable membrane inside. The main application of the blocker is in the treatment of cardiology diseases such as atrial and ventricular defects and arteriovenous catheterization, etc. The break in AD has similarities with atrial and ventricular defects, and the aim of treatment is to block the abnormal flow of blood. Therefore, vascular surgeons have borrowed this concept and tried to apply blockers to the repair of AD. The special design structure of the blocker makes it more effective in repairing AD with less obscuration of the surrounding branch vessels. It is suitable for treating AD breaches around the visceral arteries and near the branch arteries on the arch. We were the first to apply the blocker to repair peri-visceral artery breaches in China and obtained good near and long-term repair results (Figure 1) [9]. However, there are limitations in the application of blockers in repairing AD. This is because the blocker needs to be released laterally in the descending and abdominal aorta in order to achieve the best repair results. The delivery sheath introduced from the femoral artery often enters the breach at an acute angle, resulting in a dumbbell-shaped structure that does not completely cover the AD breach upon release and is sometimes even washed into the false lumen under the action of blood flow. There are reports of successful development of controlled long sheaths at the head end, which can make the blocker enter the breach at an approximate right angle and ensure that the dumbbell-shaped structure can completely clamp the breach after release to ensure the repair effect. The blocker can also be used in the repair of breaches near the aortic arch. In China, Chang Guangqi [10] et al. applied it to near-LSA breaches, and the false lumen disappeared after surgery, and the false lumen was completely thrombosed and shrunk during the follow-up (Figure 2). 2. Open-windowed and branching SGs Open-windowed SGs have side holes in the artificial vessel membrane to preserve the blood supply to one to several branch vessels. After release, the proximal portion of the SG with membrane extends beyond the branch vessel opening to expand the proximal LZ, and the branch vessel blood supply is preserved through the side holes. A common type of SG with a proximal side hole is a scallop-shaped or horseshoe-shaped side hole that is reserved or cut into the proximal portion of the SG membrane. The advantage of the proximal lateral hole is that it is relatively easy to locate and easily remedied by retracting the SG if a branch artery is mistakenly covered intraoperatively, but the disadvantage is that the extent of LZ expansion is limited. In China, there are cases of successful application of SG with clipped out side holes to repair AD while preserving LSA [11]. Another method is to reserve or cut out the lateral hole in the middle of the SG artificial vascular membrane, which can obtain a larger degree of LZ expansion. The disadvantage is the difficulty in positioning and the difficulty in remedying and adjusting the SG band membrane once it partially covers the branch vessels. In China, Zhao B et al [12] reported the successful repair of a ruptured aortic arch lesion by applying this method in combination with right common carotid artery-left common carotid artery (RCCA-LCCA) bypass (Figure 3). The author also has experience in clinical work with three cases of successful proximal LZ expansion through the open-hole technique. The disadvantage of cutting out the lateral hole preoperatively is the possible effect on the firmness of the SG, thus shortening the life of the SG. The concept of a branched SG is a conventional SG with a side branch supplying branch arterial blood flow. SGs with one branch and SGs with three branches are common and are mainly used in lesions involving the aortic arch (Figure 4). Single-branch SGs are usually used to preserve the LSA, thus allowing expansion of the proximal LZ by a completely intraluminal approach without sacrificing the LSA. single-branch SGs are relatively less difficult to operate, and Saito N et al [13] used single-branch SGs to repair AD or thoracic aortic aneurysms (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 innominate artery (INA) while reconstructing the LCCA and LSA by bypass surgery. Guo Wei et al. reported [14] a case of type A AD with retrograde tear after TEVAR, in which an RCCA-LCCA-LSA bypass was performed in one stage and an SG was delivered to the ascending aorta via the RCCA in the second stage, 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 with the main body of the previous SG to repair the lesion. In 1999, Inoue et al [15] successfully treated a case of type A AD by implanting a three-branch SG to reconstruct the INA, LCCA, and LSA, respectively, and to extend the proximal LZ and repair the aortic arch lesion with a branch SG. 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 the surgical trauma. The disadvantages are the complexity of the operation of the SG with branches, the length of the procedure, the amount of contrast agent used, and the significantly higher intraoperative radiation dose to the patient and surgeon. chuter et al [16] concluded that the complexity of the operation and the risk of cerebral infarction would increase significantly with the implantation of more SG branches. II. New surgical techniques in expanding the LZ New surgical techniques have been used to broaden the indications for TEVAR surgery by reconstructing or preserving the blood supply of branch arteries in various ways. They mainly include the application of hybridization (Hybirid) technique and chimney (chimney) technique 1. Hybridization technique Hybridization technique refers to the treatment of vascular diseases by combining surgical treatment and endoluminal repair techniques. In the treatment of AD, the main purpose of hybridization is to expand the LZ by traditional surgical methods.The more applied areas are currently to ensure the cephalad blood supply or visceral arterial blood supply by revascularization, thus expanding the LZ as much as possible.According to the zoning method proposed by Ishimaru et al [17], the aortic arch is divided into four zones, Z0, Z1, Z2 and Z3 (Figure 5). According to the different zones in which the AD rupture occurs, different strategies are applied to expand the LZ by applying hybridization techniques. 1.1, rupture located in zone Z4 near the visceral artery AD rupture can be located in the distal part of the descending aorta adjacent to the opening of the visceral artery, and some of these patients can be repaired with an optional blocker. If the breach is large and/or the true lumen is too small for the use of a blocker, the LZ needs to be enlarged by hybridization, and a bifurcated artificial vessel can be used to bypass the inferior abdominal aorta or the iliac artery to the celiac artery (CA) and superior mesenteric artery (SMA); if the renal artery needs to be covered together, a bifurcated artificial vessel can be used again. If the renal artery needs to be covered together, a bifurcated artificial vessel can be used to reconstruct the bilateral renal artery flow. 1.2. Break in the Z3 zone When the AD break is located in the Z3 zone, the length of the LZ is the distance from the break 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 first to cover the LSA. reconstruction in order to cover the LSA to obtain an adequate proximal LZ [18]. A common approach is LCCA-LSA bypass. Reconstruction of the LSA helps to more adequately seal the lesion and reduce type I endoleak (endoleak). Type II endoleak may be eliminated by proximal ligation of the LSA or blocker embolization because of proximal LSA reflux. 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 RCCA-LCCA (Figure 6) and RCCA-LCCA-LSA bypass. -LCCA-LSA bypass, etc. 1.4. When the rupture is located in the Z1 zone, but the distance between INA and 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 zone and the distance between the RCCA and RCCA is less than 1.5 cm, it is necessary to reconstruct the RCCA blood flow to obtain a sufficient proximal LZ. The Debranch technique (de-branching technique) is used. A “partial block” technique [19] is used to anastomose the proximal end of the bifurcated prosthesis 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 7). When the patient is in poor systemic condition and cannot tolerate open-heart surgery, or when a healthy segment of the ascending aorta is not available for partial block, the LZ can be expanded by means of an artificial vessel bypass from the right iliac to the right axillary, left iliac to the left common carotid, and left axillary arteries. of the Debranch technique [20]. 1.5. The rupture is located in the Z0 zone When the rupture is located in the Z0 zone, AD is classified as Stanford type A. Depending on the patient’s condition, the LZ can be expanded using either the intra-anatomic Debranch technique or an extra-anatomic bypass from the iliac artery to the cephalad vessels. if the AD rupture is located in the ZO zone but there is sufficient distal LZ between the LSA, the LSA-LCCA-RCCA bypass can be performed first, followed by implantation of a short SG through the femoral artery approach 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. chimney technique The chimney technique releases a parallel laminated stent or bare stent in the aorta through the branch artery, with one end in the aorta and one end in the branch vessel, thus preserving the blood flow in that branch [21]. chimney technique can effectively expand the proximal LZ and can be applied to preserve the INA or LCCA in thoracic aortic TEVAR [ 22]. 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 8,Figure 9).The chimney technique was first proposed by Greenberg et al [23] in 2003 and was initially applied to preserve the renal artery in the repair of abdominal aortic aneurysms with an inadequate proximal aneurysm neck, and was later Sugiura K et al [21] reported 11 patients in whom the Chimney technique was applied during TEVAR for thoracic aortic disease, of whom 3 preserved the INA by chimney, 7 preserved the LCCA, and 1 preserved the LSA. the success rate of the technique was 100%, and the mean follow-up of chimney stents at 20 months was The patency rate was 100%, with two cases of proximal endoleaks occurring, one case treated postoperatively by conventional surgical methods, and one case followed up. Since CA and SMA tend to emanate at an acute angle on the abdominal aorta, the chimeny technique can be applied from the upper limb approach to expand the proximal anchorage zone for AD with a breach located near the visceral artery. The application of these new instruments and methods of endoluminal repair can expand the LZ to a greater extent, thus expanding the indications for TEVAR and making minimally invasive treatment available to a greater number of patients. Because these new instruments and methods have their own advantages, disadvantages and applicability, vascular surgeons can apply them flexibly according to their familiarity and according to the principle of individualization to achieve the best treatment results.