Patient Characteristics
The median age of the patients was 62.0 (49.0, 72.0) years and 10.4% (12/115) were female. Two patients had preoperative aortic dissection/aneurysm rupture or signs of impending rupture, three showed insufficient blood supply to the lower limbs, and two had vascular ischemia in the visceral area. Fifteen asymptomatic patients were identified by physical examination, and five patients had traumatic involvement of the aorta with lesions. There were 91.3% (105/115) of patients with hypertension; in addition, there were other basic comorbidities, such as coronary heart disease and diabetes mellitus. After admission, CTA revealed arch lesions, including aortic dissection (n=66), aortic intramural hematoma (n=15), penetrating aortic ulcers (n=9), and thoracic aortic aneurysms (n=25). Information on patients’ preoperative conditions is presented in Table 1.
Operative and early postoperative outcomes
Of the 115 patients treated with ISNF, 175 supra-arch branch vessels were reconstructed, with a technical success rate of 100%. Of these, 79 patients had fenestration of a single-branched artery, 12 had fenestration of two vessels, and 24 had fenestration of all supra-arch branches. Of the 79 patients, LSA fenestration was performed in 77 patients, LCCA fenestration was performed in one patient, and the patient also underwent an LCCA-LSA bypass; BCT fenestration was performed in the other patient who had undergone TEVAR combined with a prior hybrid technique.
The 30-day mortality rate was 2.6% (3/115), with one patient dying from postoperative acute renal failure after receiving intermittent hemodialysis in the hospital and not continuing this after discharge. The second patient had a tear in the proximal aorta and underwent retrograde type A dissection 12 days after the surgery, followed by emergency open surgery for total aortic arch and ascending aorta replacement, ultimately resulting in respiratory and cardiac arrest. The last patient had an aortic rupture. Of the major postoperative complications, two patients had cerebral vascular accidents, one patient had lower limb paraplegia, two patients had a postoperative proximal stent tear retrograding into type A aortic dissection, and two patients had acute renal insufficiency. The perioperative outcomes are presented in Table 2.
Mid-term follow-up results
The median follow-up time was 31.0 (23.0, 40.0) months, with an overall mortality rate of 8.7% (10/115) and an aortic-related mortality rate of 2.6% (3/115). Of the remaining 7 patients who died, one died of complications while undergoing abdominal aortic surgery in another hospital, one died of renal failure 6 months after the surgery and did not undergo regular hemodialysis, one died of acute myocardial infarction, two suffered respiratory and cardiac arrest, and two died of other non-aortic diseases. Of the major postoperative complications, cerebral vascular accidents occurred in three patients, of which one had spontaneous brainstem hemorrhage 1 year after surgery, two had cerebral infarction, two had lower limb paraplegia, and one had an endoleak during regular postoperative CTA review, which was managed without intervention and reviewed regularly. No occlusion or stenosis of the aortic main or branch vessel stents was observed. In addition, four patients had distal stent-induced new entry (dSINE), four had retrograde type A dissection, and three had renal failure. Nine patients underwent thoracic aorta-related secondary operations, including four patients with retrograde type A dissection and a 21-year-old patient diagnosed with Marfan syndrome who underwent total aortic arch and ascending aorta replacement 2 years later at another hospital. Four patients with dSINE underwent TEVAR. Moreover, four patients underwent other non-aortic procedures. The additional follow-up results are shown in Table 3. Survival estimates are shown in Figure 2.
Comment
Complications of aortic arch lesions cannot be resolved using TEVAR alone because of the complex and variable vascular anatomy of the aortic arch; therefore, a combination of techniques such as parallel stents, fenestrations, and branched devices are necessary to address complicated arch lesions.[7] Parallel stents are typically susceptible to endoleaks because of the gutters between the main stent, aortic wall, and chimney stent.[8] Branched stent-grafts require advanced customization and do not meet the needs of the emergency and general public; stroke and thromboembolic accidents remain major problems associated with branched endografts.[9] This makes the ISF a relatively popular choice. In the present study, we found that the mid-term outcomes of ISNF for the treatment of aortic arch pathologies during TEVAR were within an acceptable range. Aorta-related mortality and the rate of postoperative major complications were comparatively low. To date, there is no consensus on the best method to perform fenestration. In addition, the fenestration devices must be further developed and improved.
In contrast to in vitro fenestration, ISF temporarily blocks blood flow to the target branch vessels, particularly when reconstruction of all branches of the superior arch is required and the entire blood supply to the brain is blocked, additional adjunctive cerebral protection techniques are required. Our center uses a simple but effective method for maintaining cerebral perfusion. First, the unilateral CFA is punctured with two short sheaths; then, two sheaths are punctured into the proximal and distal ends of the right common carotid artery (RCCA) and LCCA. An infusion tube is cut, and the CFA is connected to the short sheath of the distal end of the RCCA and LCCA to establish a bypass. Blood pressure is raised appropriately and a cerebral oxygen meter is connected beforehand to monitor cerebral oxygen at all times. Follow-up results proved the effectiveness of this method, with a 2.6% (3/115) incidence of postoperative cerebral accidents. In comparison, one study reported a 4.5% incidence of stroke after TEVAR.[10] In addition, there are other ways to protect the brain.[11] Ryuta Seguchi et al. described a new method of cerebral protection using selective cerebral perfusion supported by extracorporeal membrane oxygenation (ECMO) technology.[12] To restore the cerebral blood supply as soon as possible, we fenestrated the LCCA and BCT first and the LSA was fenestrated last.[13] Our approach is relatively simple, does not require the use of extracorporeal circulation machines, and achieves excellent results.
In this study, we chose a needle to perform fenestration. ISNF has been reported less frequently in the literature, and recent studies have focused on the use of thermal methods such as laser[14] or radiofrequency[15] for fenestration. When performing LSA fenestration, we use an angle-adjustable sheath with a flexible needle or an adjustable puncture system.[16] When performing fenestration of several supra-arch branches, we use a homemade fenestration device consisting of a tracheal biopsy needle (Olympus, Tokyo, Japan) and a cerebral surgical metallic suction device. We place the needle into the suction which provides support and guidance. We chose expanded polytetrafluoroethylene (ePTFE) membrane stent-grafts because experiments have shown that the ePTFE membrane is easier to puncture, and the fabric is not easy to tear after balloon dilation, thereby forming a relatively higher quality fenestration.[17] When the target vessel is excessively tortuous, twisted, or angulated, it is much more difficult to perform fenestrations. The application of the “squid catch” technique[18] ensures vertical contact between the puncture sheath and the stent graft, broadening the range of application of the ISNF technique.
During the operation, we found that fenestration of the LSA, which is usually much more tortuous, twisted, or angulated, was more difficult than that of the BCT and LCCA. When the LSA had a severe lesion or was extremely difficult to fenestrate, arterial bypass or transposition was performed. After fenestration, an appropriate balloon size was selected according to the diameter of the branch artery. When dilating the puncture site, we used gradual balloon dilation followed by balloon-guided insertion of a branch stent, slow release of the stent, and re-dilation with a balloon to avoid collapse and occlusion of the stent and ensure blood patency of the branch artery. The proximal end of the branch stent extended 1 cm inside the aorta, and the distal end avoided blocking other branched arteries.[19] To prevent endoleaks, fluency-covered stents are usually used; however, some studies have shown that the utilization of a balloon-expanded bare stent is also safe and effective if there is a sufficiently healthy PLZ.[20]
To determine the best puncture methods, many studies and experiments have compared different brands of grafts and puncture methods. As for which method results in better fenestration quality, different stent grafts tolerate mechanical and thermal energy differently, and can influence the final fenestration quality. An in vitro study[21] used five commercially-available stent grafts to perform fenestrations using a needle and laser, followed by gradual balloon dilation, to assess the fenestration quality using various quantitative indicators. We can conclude that there is no absolute best way to perform fenestration, and we should choose the appropriate method according to the different stent grafts available and existing technical conditions.
The incidence of cerebrovascular accidents was relatively low at 2.6%, demonstrating the benefits of our method of cerebral protection and simple arch operation without extra steps; therefore, a good learning curve is also key to the outcomes of ISNF. In this study, there was only one case of endoleak. The patient underwent LCCA chimney and LSA fenestration simultaneously, a small amount of endoleak was observed at the proximal end of the stent during postoperative follow-up and was reviewed regularly without intervention. Research shows that chimneys are more prone to Type I endoleaks.[22] New stent-induced entry is a major complication of this procedure. Entry tear can occur at both the proximal and distal ends of the stent. However, proximal entry is problematic and carries the potential danger of retrograde type A dissection. Our follow-up results showed that four patients had dSINE and four patients had retrograde type A dissection. Most studies have shown that the mismatch between stent size and aortic lumen diameter and the fragility of the vascular wall are the main causes of endoleak.[23] Proximal stent sizes larger than the lumen diameter are chosen to prevent type I endoleaks. However, this also increases the risk of rupture, leading to retrograde type A dissection.[24] Furthermore, the distal true cavity is usually smaller and is subjected to excessive radial forces from the stent, making it more prone to entry.[25] Therefore, stents with low radial forces, high compliance, and good fit must be developed.[26]
Limitations
First, the study was retrospective with a small sample size and lack of subgroups from a single center, so the results may be limited in terms of generalization to other populations. Second, the follow-up period was short and solid long-term clinical outcomes could not be determined. Third, the thoracic stent graft selection was relatively limited, and there was no comparison with other brands of stents. Finally, we used needles for all fenestrations and there was no comparison with other fenestration methods.