Introduction
With the continuous advancement and refinement of intravascular techniques and medical devices, Thoracic Endovascular Aortic Repair (TEVAR) has emerged as the preferred modality for treating aortic pathologies [
1,
2], traditional open surgical approaches for aortic lesions involving arch vessel branches have gradually been phased out due to their associated high trauma, mortality rates, and complication occurrence [
3]. In recent years, there has been an increase in the applications of 3D printing-assisted open aortic fenestration techniques and integrated branch stent-graft TEVAR technology, particularly in cases of aortic dissections with proximal anchoring insufficiency [
4]. These techniques are used when the distance between the tear and the left subclavian artery (LSA) is less than 15 mm [
5] (5), necessitating coverage of the LSA or left common carotid artery (LCCA) [
6] (6). However, due to the relatively short clinical application history and limited related clinical literature, debates persist regarding their safety and efficacy [
7‐
9]. Therefore, this study aims to summarize the experiential applications of these two techniques, assess their short-term clinical outcomes in the treatment of proximal anchoring insufficient aortic dissections, and analyze their pros and cons, providing new choices and insights for clinical treatment.
Discussion
For patients with aortic dissections who are not suitable candidates for open surgery, TEVAR serves as a safer and more reliable alternative. However, a healthy proximal anchoring zone of at least 15 millimeters is typically required for the safety and stability of the implanted aortic stent graft in TEVAR treatment [
5]. Unfortunately, over 40% of aortic dissection patients have inadequate proximal anchoring due to tears less than 15 millimeters from the left subclavian artery (LSA) [
12]. Traditional cardiovascular surgical interventions necessitate the administration of general anesthesia followed by a midline thoracic incision. Cardiopulmonary bypass is then initiated to facilitate meticulous examination of the aortic arch and its branches [
13], aiming to identify the precise location of the intimal tear and ascertain the extent of the lesion. Subsequently, an optimal surgical approach is chosen based on these findings. Nevertheless, owing to the substantial trauma and increased incidence of postoperative complications associated with traditional surgical techniques [
14], Tevar has emerged as a viable alternative in recent years. The debranching hybrid surgery is commonly employed to extend the proximal anchoring zone [
15]. Common procedures include carotid-subclavian artery bypass, subclavian-carotid transposition (end-to-side anastomosis), and carotid-axillary artery bypass combined with TEVAR. However, it still requires high-risk, highly invasive open chest surgery. Chimney stent techniques and in-situ fenestration techniques are also frequently used for LSA reconstruction; however, both methods require temporary coverage of the arch branches, which increases the risk of stroke [
16]. Furthermore, chimney stent techniques have a higher incidence of late endoleaks due to the formation of grooves between parallel stents and the main stent [
17]. Extracorporeal fenestration combined with TEVAR technology has been widely adopted for LSA reconstruction due to its acceptable technical success rate and complication rate. Nevertheless, it is important to note that precise stent fenestration positioning, fenestration diameter, and accurate alignment with the LSA opening are critical factors in extracorporeal fenestration technology, and the anatomical complexity of the aortic arch further complicates this technique [
18].
With the rapid advancement of 3D printing technology, its application in the medical field has become increasingly extensive. Studies have demonstrated the accuracy and reliability of 3D-printed aortic models, which can effectively guide extracorporeal fenestration surgery for aortic stents [
19,
20]. In comparison to traditional auxiliary examination methods like CT scanning and CT three-dimensional reconstruction, 3D printed models provide more intuitive and precise data, thereby playing a crucial role in surgical planning and stent selection. 3D-printed aortic arch models offer two distinct advantages in aortic stent reconstruction [
8,
21]. Firstly, the hollow and transparent nature of these models allows for precise fenestration positioning within the model after stent graft deployment, reducing potential errors caused by manual measurements. Secondly, the accurate replication of the aortic arch location enables the aortic stent graft to more accurately simulate the post-implantation position and the position of branch vessel openings compared to measurements solely obtained from CTA. This facilitates a more precise simulation of the spatial relationship between the aortic stent graft and the arch branches. In cases of aortic anatomical variations, such as bovine arch, vagal subclavian artery, left vertebral artery originating from the aortic arch, or a highly twisted or curved aortic arch, these anatomical conditions can increase the difficulty of extracorporeal fenestration surgery [
22]. Therefore, utilizing 3D printing technology to create anatomically complex aortic arch models not only allows for direct visualization of the lesion’s anatomy but also enables the simulation of the twisting of the aortic stent graft. This, in turn, facilitates more accurate fenestration design, reduces surgical difficulty, and ensures safety. Moreover, apart from guiding physicians in aortic stent fenestration surgery, 3D-printed models can visually display aortic morphology and the anatomical relationships of various branch arteries. This aids in enhancing understanding of the disease and surgical plans for both physicians and patients, promoting doctor-patient communication, and improving young physicians’ knowledge of aortic diseases [
23]. Furthermore, in precise fenestration procedures guided by 3D-printed models, our center combines the use of the “bundle diameter” technique. This technique involves reducing the diameter of the main stent by at least 30–45% before reinserting it into the delivery system, allowing for a more extensive in-vessel adjustment range. Compared to traditional extracorporeal fenestration techniques, this approach ensures sufficient blood flow to the branch arteries, reducing the likelihood of cerebral ischemic events. Additionally, it facilitates easier super-selection of the branch artery guidewire into the fenestration, thereby reducing the alignment time between the stent fenestration location and branch arteries, as well as the stent deployment time. Consequently, this shortens the surgical duration and lowers the incidence of postoperative complications [
24,
25]. Additionally, the intrabranch technique involves suturing an appropriately sized intrabranch stent at the site of the large stent fenestration. This transforms the original “wire-to-surface” contact into “surface-to-surface” contact, effectively preventing the occurrence of type I endoleaks associated with traditional extracorporeal fenestration techniques [
26]. Furthermore, the integrated design of the Castor stent eliminates the need for assembly and mitigates the risk of stent dislocation due to assembly-related leaks. The connection between the branch segment and the graft main body is composed of flexible polyester fabric, enabling the branch segment to be easily drawn into the intended branch artery. The branch-to-main stent junction offers a 150-degree rotational range, accommodating the typical angles between branch arteries and aortic arch stents [
27]. Currently, at our center, both 3D-printing-assisted extracorporeal pre-fenestration techniques and Castor integrated branch techniques are widely employed in treating TBAD with inadequate proximal anchoring zones.
Our study compared the short and mid-term clinical outcomes of patients with TBAD and inadequate proximal anchoring zones treated with these two surgical approaches. The baseline data, surgical success rate, secondary intervention rate, and mortality showed no statistically significant differences between the two groups (
p > 0.05). These findings indicate that both approaches are safe and effective, consistent with previous domestic and international studies [
28,
29]. However, we observed significantly lower postoperative rates of cavity-type cerebral infarctions and “bird-beak” signs in the 3D-printing-assisted extracorporeal fenestration group compared to the castor stent group (
p < 0.05). Several factors may contribute to this disparity. Firstly, the branch segments of the Castor integrated branch stent are relatively flexible, making them prone to distortion in cases where the angle between the left subclavian artery (LSA) and the aortic arch is small. This distortion can lead to the narrowing of the branch stent [
30] (See Fig.
5 Picture C, D), slowed blood flow, and the formation of small thrombi, which increase the risk of lacunar cerebral infarction. In contrast, the 3D-printing-assisted extracorporeal fenestration approach utilizes a separate metal-covered branch stent inserted through the brachial artery into the main stent fenestration below the LSA. This technique better adapts to vascular anatomical structures, resulting in a significantly lower probability of stent distortion and branch stent narrowing. Secondly, the Castor integrated branch stent lacks a stent-covered area at its main front end and has only a short stent-covered area. In cases of aortic arches with significant curvature or complex morphologies, “bird-beak” signs are more likely to occur, impeding stent anchoring and increasing the risk of stent migration. Additionally, the castor stent group had a significantly shorter operation time compared to the 3D-printing-assisted extracorporeal fenestration group (
p < 0.05). This is mainly because the Castor integrated branch stent does not require extracorporeal stent modification, resulting in a lower rate of endoleakage [
31]. However, in our study, there was no significant difference in the postoperative endoleak rate between the two groups. Further studies with larger sample sizes are needed to confirm these findings. Lastly, the expansion rate of the true and false lumens and the degree of thrombosis after TEVAR are reliable indicators for evaluating the long-term prognosis of TBAD patients [
32,
33]. In our study, we found no significant differences between the two groups in terms of the expansion rate of the true and false lumens and the degree of thrombosis between stented and non-stented segments. However, within each group, the postoperative expansion rate of the true lumen and the degree of false lumen thrombosis in the stented segment were significantly better than those in the non-stented segment (
p < 0.05). This suggests that stented segments have a better effect on aortic remodeling [
34,
35].
Limitations
(1) Currently, the materials used in 3D-printed aortic models are relatively rigid and cannot fully simulate the changes in the aorta under force [
36,
37]. With advancements in 3D printing technology, we anticipate obtaining more flexible and elastic materials that can accurately simulate the physiological conditions of the aortic arch. Additionally, we are exploring ways to shorten the model preparation time to benefit critically ill patients requiring urgent surgery. (2) The Castor integrated branch stent has some major limitations: ① The current stent models may not meet the needs of all cases due to individual anatomical variations, particularly in reconstructing double-branch or triple-branch scenarios. ② The release steps are relatively complex and require sufficient release space to expand the branch stent, which may carry a higher risk of complications such as arterial wall injury, plaque, or thrombus detachment leading to lacunar cerebral infarction. However, we acknowledge that our study has limitations, including a small sample size, a short follow-up period, and the need for more data to assess medium to long-term treatment outcomes [
38]. Therefore, larger-scale, longer-term, and more rigorous randomized controlled trials are urgently needed to validate the efficacy and feasibility of 3D-printing-assisted extracorporeal pre-fenestration techniques in treating TBAD patients with inadequate proximal anchoring zones.
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