Discussion

Thoracic aortic ISF is the core technique for supra-aortic branch reconstruction, whereas conventional strategies have long been plagued by three major clinical challenges: the risk of cerebral embolism, insufficient puncture accuracy, and the mutual exclusivity between cerebral protection and device access. This design may help address the aforementioned limitations. Preclinical experiments have verified that this system possesses both favorable safety and efficacy. Hereinafter, we conduct an in-depth discussion focusing on the core innovations of the system, and elucidate its technological breakthroughs and clinical value in the context of current research progress.

Integrated design: resolving the access conflict of conventional strategies

In conventional ISF procedures, there is an inherent compatibility conflict in device access between the cerebral protection device and puncture operation: deployment of the embolic protection filter occupies the surgical access required for puncture and fenestration, rendering the puncture procedure unfeasible; whereas prioritizing the puncture access requires abandoning real-time cerebral protection, leaving patients exposed to the risk of cerebral embolism. This inherent limitation forces operators to face a persistent dilemma between “safety and operability”.

A key feature of this system is the integration of the embolic protection filter and the active steering directional puncture catheter into a single device, which enables simultaneous “whole-procedure cerebral protection” and “precision puncture” via a single access. This integrated design is not a simple superposition of devices, but a fundamental optimization of the surgical workflow: it eliminates the need for access switching and additional deployment of protection devices. In the in vivo experiments, all six experimental animals completed the full surgical workflow with a 100% success rate, no device-related complications occurred, and the total operative time was controlled at 38.92 ± 4.36 minutes. The score for “Degree of Procedural Simplification” in the operator feedback reached 7.50 ± 0.55 points. Compared with conventional strategies,11, 12, 13 these results demonstrate that this integrated design may simplify the surgical workflow, reduce operational complexity, and show promising feasibility in this preclinical setting.

Active steering directional mechanism: Overcoming the challenge of puncture accuracy in complex anatomical scenarios

The anatomical complexity of the aortic arch (especially type Ⅱ and Ⅲ arches) is a key factor limiting the puncture success rate of ISF. Conventional puncture tools rely on the operator's hand feel and experience, making it difficult to achieve vertical puncture at the ostium of the target vessel. This tends to cause complications such as needle slippage and out-of-bounds puncture, which significantly increases surgical risk and operation time, and is one of the barriers restricting the popularization of ISF technology.7, 8, 9

In this study, the active steering directional mechanism allowed the puncture force line to be oriented approximately perpendicular to the stent graft by adjusting the force direction and angle of the catheter tip, thereby potentially reducing the degree of reliance on operator experience. The in vitro experimental results showed that this mechanism could achieve highly concentrated puncture sites within the projection area of the target vessel ostium across all types Ⅰ to Ⅲ arch scenarios, with a puncture coverage ratio of 41.9% to 68.8% and no out-of-bounds puncture observed in any case. Even under the type Ⅲ arch with the most restricted anatomical space, the effective puncture coverage ratio of the left subclavian artery and left common carotid artery remained at 41.9% and 44.0%, respectively, and the brachiocephalic trunk even showed an upward trend in puncture concentration. These findings suggesting that this mechanism has favorable adaptability to the most clinically complex anatomical scenarios.

Of note, the active steering directional design not only improves puncture accuracy, but also enables efficient fenestration. The mean fenestration time in the in vivo experiments was 0.15 ± 0.03 minutes (5-11 seconds), and this efficiency advantage is particularly prominent in direct comparison with existing fenestration devices. The currently recognized highly efficient Quick fenestrator still has a mean fenestration time of 0.67 ± 0.06 minutes (approximately 40 seconds), whereas the fenestration time of conventional laser and needle puncture is 5.50 ± 3.10 and 3.50 ± 1.50 minutes, respectively11 (Table VII). Of note, intraoperative observation found that after adjustment, the active steering directional puncture catheter also possessed the “fixation” and “position-limiting” functions as reported in the literature, which can stabilize the relative position between the catheter tip and the stent graft, reduce catheter displacement and force dispersion during puncture,14 and further improve the success rate of puncture and fenestration. Meanwhile, no clear linear association was observed between fenestration time and total procedure time in this study, which differs from the conclusion in existing studies that “puncture time is a key factor affecting total operative duration.”11,15 This preliminary finding indicates that this active steering directional mechanism can significantly reduce the time consumption and operational uncertainty of the puncture procedure, and is expected to alleviate the restriction of this step on the overall surgical efficiency. The highest score was observed in the dimension of directional accuracy in the operator feedback (7.83 ± 0.75 points), which is consistent with the favorable puncture performance observed in both the benchtop and in vivo experiments.

Device type | Mean fenestration time, minutes | Integrated cerebral protection | References
Laser fenestration | 5.50 ± 3.10 | No | Wang et al,11 2023
Needle fenestration | 3.50 ± 1.50 | No | Wang et al,11 2023
Quick fenestrator | 0.67 ± 0.06 | No | Bai et al,15 2021
Present integrated system | 0.15 ± 0.03 | Yes, 120 μm filter | Present study

Targeted cerebral protection function: Addressing the core risk of high postoperative stroke incidence following ISF

The incidence of post-ISF stroke is as high as 6%,5,6 and its core inducement is cerebrovascular embolism caused by intraoperatively generated plaque debris, thrombus, and stent graft fragments larger than 100 μm.16,17 Studies have found that even patients with asymptomatic cerebral infarction present corresponding behavioral changes during long-term follow-up.18,19 Conventional strategies either lack whole procedure cerebral protection, or cannot perform puncture operations, whereas cerebral protection is implemented.

The cerebral protection function of the device in this study has clear targeting: the embolic protection filter adopts a mesh with a 120 μm pore size. In vitro experiments showed that the capture rates for microspheres of stroke-causing critical particle sizes of 120 and 150 μm reached 87.1% ± 2.7% and 98.1% ± 0.9%, respectively. This capture efficiency is comparable to the performance of clinically used cerebral protection devices reported in the literature,20,21 and may reduce the risk of symptomatic embolism. The result that the embolic protection filter successfully captured thrombus debris in the in vivo experiments verified its protective capability in a physiological blood flow environment. The 120 μm pore size reflects a balance between embolic protection and cerebral perfusion. Smaller pores could capture more sub-120 μm particles but may increase the risk of filter thrombosis and flow compromise, whereas larger pores may inadequately capture stroke-critical debris.16,20,21 In this study, capture efficiency was 87.1% for 120 μm but only 24.2% for 100 μm microspheres, indicating that smaller particles may still escape. The clinical significance of such microemboli remains uncertain, and future device refinements may address this residual risk. Notably, all in vitro capture experiments were performed using standardized spherical fluorescent microspheres, which differ in shape, surface texture, and mechanical properties from clinically relevant embolic materials such as irregular atherosclerotic plaque fragments and thrombus. Existing literature has consistently demonstrated that irregularly shaped debris is more easily captured by filter meshes than smooth spherical particles of the same size. Therefore, the capture rates reported in this study represent conservative estimates, and the actual embolic protection efficacy of the device in real clinical scenarios is likely to be higher.

The qualitative air bubble observation should be regarded strictly as hypothesis-generating; it provides no evidence of clinically meaningful air embolus protection. Intraoperative air introduction must continue to be meticulously avoided through standard flushing and deairing techniques.22,23

This design focuses on the intraoperative safety issues of ISF, and may help address the technical limitation of conventional strategies that protection and operation cannot be synchronized through the “whole procedure cerebral protection” mode. The in vitro experimental results and immediate in vivo observation findings have preliminarily confirmed its embolic capture capability, indicating its potential to provide embolism protection during ISF procedures, which lays a foundation for subsequent clinical validation.