The treatment of Stanford (Stanford) type B aortic coarctation has been highly controversial. Initially, most scholars believed that surgical treatment was highly invasive, with many complications and high mortality, and should be conservative. 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 principle of using endoluminal stent isolation to treat 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, thus serving to stabilize the aortic wall.
Indications and contraindications for clinical application
Indications:
①StanfordBS type aortic coarctation;
(ii) Thoracoabdominal aortic dissection or near dissection with stent placement for emergency treatment;
③StanfordB type coarctation combined with important organ ischemia, intractable hypertension that cannot be controlled by drugs or persistent pain that cannot be relieved by drugs, etc;
④Anchorage area ≥1.5cm and normal aortic diameter in the anchorage area ≤3.8cm;
⑤ Aortic ulcer;
(6) Type B aortic coarctation without the above indications, anchorage area <1.5 cm and non-left dominant vertebral artery, major abdominal vessels from the pseudolumen but with 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, involvement of the ascending aorta and branch vessels of the aortic arch, and aortic valve insufficiency (> grade II);
③Severe atherosclerotic lesions in the anchoring area or significant thickening of the aortic internal diameter in the anchoring area ≥4 cm;
④The angle between the aortic arch and the descending aorta is acute;
⑤ Marfan syndrome and aortic coarctation due to connective tissue genetic diseases, such as Loeys-Dietz syndrome.
Management of special types of patients
Patients with limited abdominal aortic coarctation are relatively rare, accounting 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 lesions.
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 B coarctation is usually safe, with satisfactory early to midterm outcomes in most patients.
Clinical Outcomes
Criteria for successful interventional treatment of Stanford B aortic coarctation include.
(i) Complete closure of the proximal primary rupture.
(ii) No significant endoleaks and other serious complications (e.g., paraplegia).
③ disappearance of the false lumen at the level of the thoracic aortic stent or thrombus formation 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 pseudoluminal thrombosis is 79%~100%.
In China, Huang Lianjun et al. reported that all 86 patients with Stanford B coarctation were successfully treated with endoluminal stent placement, and the postoperative imaging showed only a small amount of endoleaks in 9 cases, and the postoperative follow-up revealed that all patients survived in good health except for one patient (1.16%) who died after surgery due to pseudoaneurysm distal to the stent, and the patients with endoleaks did not worsen. This shows that endoluminal overmolded stent placement for Stanford B type entrapment is reliable, relatively simple to perform, less risky, less traumatic, with rapid patient recovery, fewer complications, and lower mortality.
Current problems
Endoleaks:Endoleaks affect the immediate outcome after stent placement and also have a greater adverse effect on the long-term outcome. They can be divided into immediate endoleaks and late endoleaks according to the time of occurrence, and 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, treated by surgery or re-stenting.
Aneurysm degeneration:
Leakage and altered conduction of internal tension after pseudoluminal thrombosis can lead to aneurysm. Once an aneurysm or progressive increase in the diameter of the entrapment occurs, it should be closely monitored and, if necessary, referred for surgical treatment or re-stenting.
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 for during sham lumen thrombosis. Even so, stenting should be avoided during stent intervention for Stanford B coarctation, especially when trying not to cover the aorta at the T8 to L2 level to prevent paraplegia.
Partial thrombosis or non-compression of the false lumen:Failure of complete thrombosis of the false lumen is mostly caused by endoleaks, especially type II endoleaks. In contrast, incomplete thrombosis of the pseudolumen is most often seen in chronic Stanford B-type entrapment, so the treatment of such patients should emphasize closure of the distal rupture.
Retrograde dissection of the interstitial layer after stent placement resulting in type A entrapment: This complication is most often seen in acute Stanford B entrapment, where retrograde tearing of the interstitial layer results in ascending aortic entrapment 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 not be dealt with, so that diversion surgery can be considered and the aorta of the overlapping stent segment can be left open.
Stent placement pseudo-lumen: Stent placement pseudo-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.
Operation and stent guiding system should be improved: The guiding system of aortic stent is thick (about 20~24F), and most of the aortic endoluminal overlay stent placement requires 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 aortic stent guide system and the overlapping stent itself have yet to be improved to adapt them to more complex situations in order to reduce surgical operations and related complications.
Patient selection is controversial:
Patient selection for aortic endoluminal stenting for Stanford B coarctation is currently controversial, with selection criteria varying from center to center and entirely dependent on operator experience. Therefore, a more objective patient scoring selection system is needed to improve the outcome of interventions for Stanford B coarctation.
Hybrid (hybridization) technique
The hybrid technique is a treatment method for complex aortic disease that has emerged in recent years. Aortic head-arm revascularization (debranch procedure) is usually performed in stage I, and endoluminal overlapping stent placement in the aorta is performed in the same period or in stage II. This technique is suitable for some patients of advanced age, involving the aortic arch, with high surgical risk and a short natural course of disease.
In conclusion, the results of overlapping stent intervention for Stanford 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 the disciplines of materials science and imaging medicine, the future of interventional treatment of aortic coarctation is promising.