In Situ Laser Fenestration Technique: Bench-Testing of Aortic Endograft to Guide Clinical Practice

In situ laser fenestration of the Thoraflex Hybrid frozen elephant trunk for emergent revascularization of the left subclavian artery and laser fenestration for spinal cord perfusion

In situ laser fenestration (ISLF) has emerged as a promising technique for emergent revascularization of the left subclavian artery in the case of thoracic endovascular aortic repair coverage, presenting excellent technical success rates in most studies. We describe a case of ISLF of the Thoraflex Hybrid frozen elephant trunk device to achieve immediate left subclavian artery revascularization. We demonstrate the feasibility and technical success of using ISLF in this setting, providing a less invasive alternative to conventional surgical revascularization when required.

Anatomic Feasibility of In-Situ Fenestration for Isolate Left Subclavian Artery Preservation during Thoracic Endovascular Aortic Repair Using an Adjustable Needle Puncturing System

OBJECTIVES

To evaluate the feasibility of thoracic endovascular aortic repair (TEVAR) using the Ankura™ device (Lifetech Scientific, Shenzhen, China) with left subclavian artery (LSA) in-situ fenestration (ISF) using an adjustable puncture device system.

METHODS

It is a single center, retrospective, financially unsupported cohort study of TEVAR performed from 16 February 2007 to 10 January 2023. Inclusion criteria were isolate LSA revascularization for elective or urgent/emergent "zone 2" TEVAR, and the availability of the preoperative computed tomography angiography.

RESULTS

Post-hoc analysis identified 52 TEVARs. There were 39 (75.0%) males, and 13 (25.0%) females: median age was 74.5 years (IQR, 65.5-78). Index TEVAR was performed for atherosclerotic aneurysm in 27 (51.9%) cases, dissection-related diseases in 18 (34.6%), penetrating aortic ulcer in 5 (9.6%), and blunt traumatic aortic injury in 2 (3.8%). Access-vessel feasibility rate of TEVAR using the Ankura™ device would have been 98.1% (51/52). Considering the morphology of the aortic arch, ISF TEVAR feasibility would have been 61.5% (32/52). Binary logistic regression analysis identified LSA angulation (OR: 1.1, 95%CI: 1.03-1.14, p = 0.003) to be associated with ISF feasibility using this endograft and a self-centering adjustable needle-based puncture device.

CONCLUSIONS

Potential feasibility of TEVAR using the Ankura™ endograft with ISF using a self-centering adjustable needle system was 61.5%. Left subclavian artery angulation seems to be the most important and limiting anatomical constraint.

Off-the-Shelf Single-Fenestrated Endograft for Emergent Juxtarenal and Pararenal Abdominal Aortic Aneurysm

INTRODUCTION

Endovascular solutions to emergent juxtarenal and pararenal abdominal aortic aneurysms (AAAs) are complicated. Endovascular aortic repair (EVAR) with in situ laser fenestration (ISLF) is promising but requires a period of visceral ischemia. With an off-the-shelf, single superior mesenteric artery (SMA)-fenestrated device mesenteric ischemia is avoided and renal ischemia decreased. The aim was to develop an optimized design of such an endograft suitable for >90% of juxtarenal and pararenal AAAs.

METHODS

Single-center analysis on 44 consecutive preoperative CTs for previously elective fenestrated EVARs for juxtarenal and pararenal aneurysms. Anatomical characteristics were analyzed to define: (1) shortest aortic coverage above SMA fenestration to achieve ≥4 cm seal; (2) feasibility of a scallop for the celiac artery; (3) shortest distance between the SMA and lowest renal, to facilitate renal ISLF in a straight endograft; (4) distance from the lowest renal to the aortic bifurcation, to allow an overlapping zone >40 mm with a bifurcated stent graft; (5) aortic diameter in the sealing zone, for optimal proximal stent graft diameter with 10% to 30% oversizing; (6) the final design was then tested on individual level.

RESULTS

(1) The stent graft needs to start 40 mm above the SMA fenestration to achieve a 4 cm sealing zone in >90% of cases. (2) A proximal sealing zone of 40 mm without a scallop covers 77% of celiac arteries. With an addition of a 20 mm deep, 20 mm wide scallop at 12:30, the stent graft still covers 27% of celiacs. This suggests that a scallop would not be practically feasible. (3) In >90% of cases, the lowest renal was <31 mm from the SMA, suggesting that the tapering should start 30 mm below the SMA. (4) The distance from the lowest renal to the aortic bifurcation ranged from 82 to 166 mm. This allows for a 20 mm tapering and 50 mm straight part in all cases. (5) The 5th and 95th percentile of the aortic diameter in the sealing zone was 22 and 31 mm, respectively. Thus, 2 different stent graft diameters (28 and 34 mm) would fit >90% of cases. (6) The final design was suitable in 91% cases.

CONCLUSIONS

Two sizes of a single-fenestrated aortic stent graft without scallop cover >90% of juxtarenal and pararenal anatomies.

CLINICAL IMPACT

Emergent juxta- and pararenal aortic aneurysms is a difficult clinical scenario that continuously challenges physicians. An endovascular option is in situ laser fenestrated endografts. One risk with these is the complete visceral ischemia occurring before the fenestrations are completed. An off-the-shelf single-fenestrated stent graft facilitates the treatment by removing the ischemia time for the SMA and reducing the ischemia time for the celiac and renal arteries thus decreasing the risk of visceral ischemia complications.

Urgent endovascular mycotic aortic arch aneurysm repair using in situ laser fenestration and selective arterial perfusion with venoarterial extracorporeal membrane oxygenation

In recent years, mycotic aortic aneurysms have been increasingly treated successfully by endovascular means. The introduction of custom-made fenestrated and branched devices, parallel graft techniques, and in situ fenestration has enabled total endovascular treatment also for arch pathologies. We describe a total endovascular repair of a mycotic arch aneurysm with in situ laser fenestration using venoarterial extracorporeal membrane oxygenation to preserve flow to vital organs.

Mechanical Comparison between Fenestrated Endograft and Physician-Made Fenestrations

INTRODUCTION

A fenestrated endograft (FE) is the first-line endovascular option for juxta and pararenal abdominal aortic aneurysms. A physician-modified stent-graft (PMSG) and laser in situ fenestration (LISF) have emerged to circumvent manufacturing delays, anatomic standards, and the procedure's cost raised by FE. The objective was to compare different fenestrations from a mechanical point of view.

METHODS

In total, five Zenith Cook fenestrations (Cook Medical, Bloomington, IN, USA) and five Anaconda fenestrations (Terumo Company, Inchinnan, Scotland, UK) were included in this study. Laser ISF and PMSG were created on a Cook TX2 polyethylene terephthalate (PET) cover material (Cook Medical, Bloomington, IN, USA). In total, five LISFs and fifty-five PMSG were created. All fenestrations included reached an 8 mm diameter. Radial extension tests were then performed to identify differences in the mechanical behavior between the fenestration designs. The branch pull-out force was measured to test the stability of assembling with a calibrated 8 mm branch. Fatigue tests were performed on the devices to assess the long-term outcomes of the endograft with an oversized 9 mm branch.

RESULTS

The results revealed that at over 2 mm of oversizing, the highest average radial strength was 33.4 ± 6.9 N for the Zenith Cook fenestration. The radial strength was higher with the custom-made fenestrations, including both Zenith Cook and Anaconda fenestrations (9.5 ± 4.7 N and 4.49 ± 0.28 N). The comparison between LISF and double loop PMSG highlighted a higher strength value compared with LISF (3.96 N ± 1.86 vs. 2.7 N ± 0.82; p= 0.018). The diameter of the fenestrations varied between 8 and 9 mm. As the pin caliber inserted in the fenestration was 9 mm, one could consider that all fenestrations underwent an "elastic recoil" after cycling. The largest elastic recoil was observed in the non-reinforced/OC fenestrations (40%). A 10% elastic recoil was observed with LISF.

CONCLUSION

In terms of mechanical behavior, the custom-made fenestration produced the highest results in terms of radial and branch pull-out strength. Both PMSG and LISF could be improved with the standardization of the fenestration creation protocol.

Stent-Graft Fabrics Incorporating a Specific Corona Ready to Fenestrate

In situ fenestration of endovascular stent-grafts has become a mainstream bailout technique to treat complex emergent aneurysms while maintaining native anatomical visceral and aortic arch blood supplies. Fabric tearing from creating the in situ fenestration using balloon angioplasty may extend beyond the intended diameter over time. Further tearing may result from the physiologic pulsatile motion at the branching site. A resultant endoleak at the fenestrated sites in stent-grafts could ultimately lead to re-pressurization of the aortic sac and, eventually, rupture. In an attempt to address this challenge, plain woven fabrics were designed. They hold a specific corona surrounding a square-shaped cluster with a plain weave fabric structure, a 2/2 twill, or a honeycomb. The corona was designed to stop potential further tearing of the fabric caused by the initial balloon angioplasty and stent or later post-implantation motion. The cluster within the corona was designed with relatively loose fabric structures (plain weave, 2/2 twill weave, and honeycomb) to facilitate the laser fenestration. Two commercial devices, Anaconda (Vascutek, Terumo Aortic) and Zenith TX2 (Cook), were selected as controls for comparison against this new design. All the specimens were characterized by morphology, thickness, and water permeability. The results demonstrated that all specimens with a low thickness and water permeability satisfied the requirements for a stent graft material that would be low profile and resistant to endoleaks. The in situ fenestrations were performed on all fabrics utilizing an Excimer laser followed by balloon angioplasty. The fabrics were further observed by light microscopy and scanning electron microscopy. The dimension of the fenestrated apertures was smaller than the balloon's diameter. The tearing was effectively confined within the corona. The clinical acceptability of this concept deserves additional bench testing and animal experimentation.

In Situ Laser Fenestrations of Aortic Endografts for Emergent Aortic Disease

BACKGROUND

In situ laser fenestration (ISLF) is a novel endovascular technique which allows customization of a standard stent graft to a patient's anatomy. While most reported cases involve revascularization of the left subclavian artery (LSA), some centers have now reported their initial experience treating branches of the visceral aorta for aortic aneurysms. The aim of this study is to examine the adoption of ISLF in emergent aortic pathology at a specialized aortic center.

METHODS

Between December 2020 and February 2022, all patients who underwent ISLF as part of endovascular intervention for complex aortic pathology at a university hospital were identified. Cases were collected from a prospective aortic database with additional information obtained from a retrospective review of electronic hospital records.

RESULTS

Fifteen patients (11 men and 4 women) underwent emergency ISLF, with a median age of 76 years. Eleven presented with symptomatic or ruptured aortic aneurysms, three with acute complicated aortic dissections and 1 aortic traumatic transection. Most aortic aneurysms were thoraco-abdominal (n = 7), with 1 arch, 1 thoracic, 1 supra-renal, and one-juxta-renal aortic aneurysm. ISLF was performed to revascularize the LSA in 8 cases, and branches of the reno-visceral aorta in 7 cases. All LSA ISLF cases had left brachial artery exposure. Femoral access was percutaneous in 14 of 15 cases. Technical success was 96.3% (26/27)). Median ischemic times were: superior mesenteric artery 7 min, renal arteries 22 min, and celiac trunk 43.5 min. There were 2 early aortic/fenestration related reinterventions. There was no stroke and 1 death caused by heparin-induced thrombocytopenia within 30 days. The majority of patients did not require intensive care admission (n = 8). The median intensive care unit stay was 0 days and hospital length of stay 18 days. There was no fenestration endoleak or reintervention post discharge with a median follow-up of 168 days.

CONCLUSIONS

ISLF is a promising new technique that can show excellent technical results in experienced aortic centers, even during the learning curve. While custom-made devices with reinforced fenestrations are preferred in nonemergent situations, ISLF is a feasible option for complex aortic pathology in the acute setting when open surgery is not feasible.