The treatment of Stanford type B aortic coarctation has been controversial. Initially, most scholars believed that surgical treatment is highly invasive, has many complications, and has a high mortality rate, and should be treated conservatively. With the development of related disciplines and the increasing understanding of the disease, there is now a tendency to adopt more aggressive treatment measures for patients with Stanford type B coarctation.
Aortic interventions, which are less invasive, simpler to perform, and have fewer complications, began in 1991 and became more widely used after Nienaber and Dake reported on endoluminal stent isolation for aortic coarctation in 1999. The rationale for the use of endoluminal stent isolation in the treatment of aortic coarctation is to close the endothelial rupture of the proximal aortic tear, isolate the blood flow between the true and false lumen of the aortic coarctation, dilate the true lumen, and promote thrombosis of the false lumen, thereby stabilizing the aortic wall.
Stanford type B intracavitary overlapping stent placement preoperatively and postoperatively showed that the contrast agent in the false lumen disappeared after stent placement
Clinical Applications
Indications and contraindications
Indications
①Stanford BS-type aortic coarctation.
(ii) Thoracoabdominal aortic dissection or near dissection with stent placement for emergency treatment.
③Stanford B type entrapment combined with important organ ischemia, intractable hypertension that cannot be controlled by drugs or persistent pain that cannot be relieved by drugs, etc.
(iv) Anchorage area ≥ 1.5 cm and normal aortic diameter in the anchorage area ≤ 3.8 cm.
⑤ aortic ulcer.
(6) Type B aortic coarctation without the above indications, anchorage zone <1.5 cm and non-left dominant vertebral artery, major abdominal vessel from the pseudolumen but with a large secondary rupture nearby.
Contraindications
(i) Severe stenosis or distortion of the iliac or femoral arteries that prevents passage of the conduction system.
(ii) Complicated pericardial tamponade, vascular involvement of the ascending aorta, branch vessels of the aortic arch, and aortic valve closure insufficiency (> grade II).
③severe atherosclerotic lesions in the anchor zone or significant thickening of the aortic internal diameter in the anchor zone ≥ 4 cm.
④an acute angle between the aortic arch and descending aorta.
⑤ Marfan syndrome and aortic coarctation due to connective tissue genetic disorders, such as Loeys-Dietz syndrome.
Management of special types of patients
Patients with limited abdominal aortic coarctation are rare and account for only about 1% of aortic coarctations. Faber et al. suggest that such patients with aortic dissection or near dissection should be treated with emergency surgery, not only to replace the diseased aorta, but also to explore it intraoperatively to exclude other abdominal organ pathologies.
In patients with intramural aortic hematoma, endoluminal stent intervention is not required because there is no obvious rupture and there is already thrombosis between the inner and outer membranes.
Management of patients in the acute phase
The management of patients in the acute phase is controversial. Some scholars believe that stenting should be performed after the aortic wall edema has subsided and is relatively stable, otherwise it may lead to new rupture of the intima and new entrapment or endoleaks. However, based on recent reports in the literature and our experience, luminal placement of overlapping stents in patients with acute Stanford type B coarctation is usually safe, with satisfactory early to midterm outcomes in most patients.
Clinical Outcomes
Criteria for successful interventional treatment of Stanford type B aortic coarctation include.
① complete closure of the proximal primary rupture.
(ii) absence of significant endoleaks and other serious complications (e.g., paraplegia), and
③ disappearance of the false lumen at the level of the thoracic aortic stent or thrombosis within the false lumen.
Due to the different cases selected by each hospital, the current success rate of intracavitary aortic stent placement is about 85%~100%, the mortality rate in the early postoperative period (30 days) is 0~16%, and the incidence of false lumen thrombosis is 79%~100%.
In China, Huang Lianjun et al. reported that all 86 patients with Stanford type B coarctation were successfully treated with endoluminal stenting, and postoperative imaging showed only a small amount of endoleaks in 9 cases. This shows that endoluminal overmolded stent placement for Stanford type B entrapment is reliable, relatively simple, low-risk, and less invasive, with rapid patient recovery, few complications, and low mortality.
Current problems
1.Inside leakage
Endoleaks affect the immediate results after stent placement and also have a greater adverse effect on the long-term outcome. According to the time of occurrence, it can be divided into immediate endoleaks and late endoleaks, which are mainly divided into the following four types.
Immediate type I endoleaks are mainly caused by inappropriate aortic curvature, anchorage area or improper stent selection, and type I endoleaks can also occur when the aortic endothelium is torn during operation. Delayed type I endoleaks are mainly caused by the stent not adhering closely enough to the endothelium of the attachment area after the contraction of the pseudoluminal thrombus or the enlargement of the true lumen filling, or the stent is displaced so that the originally closed endothelial rupture is exposed again.
②Type II endoleaks mainly refer to reflux. In addition to the above-mentioned causes, type II endoleaks can also be caused by blood flow reversing into the false lumen because the distal rupture becomes the entrance after the proximal rupture of the aortic coarctation is closed, or the false lumen is connected to the collateral vessels and blood flow from the collateral arteries pours into the false lumen.
Type III endoleaks mainly refer to the rupture of the stent itself or the endoleak of the stent connection.
Type IV endoleaks refer to endoleaks caused by leakage of the stent overlay or other causes. Endoleak is a more serious complication of aortic endoluminal stent intervention, once it occurs, it should be closely observed and if necessary, surgical treatment or re-stenting treatment should be performed.
2.Aneurysmal changes
Endoleaks and changes in the conduction of internal tension after pseudoluminal thrombosis can lead to aneurysm. Once aneurysm changes or progressive increase in the diameter of the clamping occurs, close observation should be made, and if necessary, surgical treatment or re-stenting should be performed.
3.Paraplegia
Paraplegia has been reported less frequently in Stanford B aortic coarctation treated with intraluminal stenting, probably because the spinal cord blood supply has been effectively compensated during the process of sham lumen thrombosis. Even so, when stenting Stanford type B clamps, it is important to avoid too low stent position, especially to avoid covering the aorta from T8 to L2 level to prevent paraplegia.
4. Partial thrombosis or non-compression of the false lumen
Failure to completely thrombose the false lumen is mostly caused by endoleaks, especially type II endoleaks. The false lumen not being compressed is mostly seen in chronic Stanford B type clot, so the treatment of such patients should emphasize the closure of the distal rupture.
5. Type A entrapment caused by retrograde dissection of the stent after stent placement
This complication is most often seen in acute Stanford type B coarctation, where retrograde tearing of the coarctation results in ascending aortic coarctation due to re-rupture of the aortic intima in the anchorage area. This complication has serious consequences and should be re-surgical once it occurs. In the acute stage, the original overlapping stent can be removed, and in the chronic stage, when the overlapping stent and the aortic intima are closely attached, the original stent should not be forcibly removed to avoid serious aortic tears that can’t be dealt with, so that diversion surgery can be considered and the aorta of the overlapping stent segment can be left open.
6.Stent placement into false lumen
Stent placement false lumen is the most serious complication of aortic stenting, and once it occurs, patients mostly die, so this complication should be avoided as much as possible when performing aortic coarctation intervention.
7.Operation and stent guiding system still need to be improved
The aortic stent guide system is thick (about 20~24F), and most of the aortic endoluminal overlay stenting procedures require incision of the femoral artery, which may lead to related complications, such as pseudoaneurysm of the femoral artery incision, incision infection, and lymphatic leakage. Moreover, some patients with stenosis and torsion of the iliac artery cannot be treated with this technique. Therefore, the guiding system of aortic stent and the overlapping stent itself are yet to be improved to make it adaptable to more complicated situations in order to reduce surgical operations and related complications.
8. Patient selection is still controversial
The selection of patients for aortic endoluminal stenting for Stanford type B coarctation is controversial, as the selection index varies from center to center and is entirely dependent on the experience of the operator. Therefore, a more objective patient scoring selection system is needed to improve the outcome of interventions for Stanford B coarctation.
9.Hybrid (hybrid) technique
Hybrid technique is a complex aortic disease treatment method that has emerged in recent years. Generally, aortic head and arm revascularization (debranch procedure) is performed in stage I, and endoluminal overlapping stent placement in the aorta is performed in the same period or stage II. This technique is suitable for some patients of advanced age, with involvement of the aortic arch, high surgical risk and a short natural course.
In conclusion, the results of overlapping stent intervention for Stanford type B coarctation are encouraging in the early stages, but there is a lack of large multicenter prospective randomized controlled clinical studies to compare the medium- and long-term results of surgical procedures, medical drug therapy, and overlapping stent intervention. Nevertheless, with advances in material science and imaging medicine, the future of interventional treatment of aortic coarctation is promising.