Technical Aspects of Fenestrated Arch TEVAR With Preloaded Fenestration

Abstract

Fenestrated thoracic endovascular aortic repair (f-TEVAR) has expanded the possibilities of endovascular arch repair, allowing treatment of pathologies involving the aortic arch that require sealing in Ishimaru zones 1 and 2. The growing number of implantations has increased physician experience and helped identify critical procedural points, mainly wire entanglement and device malrotation. Herein we describe a step-by-step approach to a f-TEVAR procedure with the Zenith fenestrated preloaded thoracic endograft, identifying potential pitfalls and suggesting problem-solving solutions.

Keywords

fenestrated thoracic repair endovascular treatment thoracic aortic repair (TEVAR)custom-made devices (CMD)aortic arch aortic pathology

Introduction

Open surgery represents the “gold standard” of treatment for diseases involving the ascending aorta and aortic arch, with morbidity and mortality rates ranging between 4% and 10% in low-risk patients.¹ The development of new endovascular techniques to treat aortic arch pathologies has mitigated risks associated with open surgery, offering treatment options to the elderly, high-risk patients and those with prior open cardiothoracic procedures.² In the early years of total endovascular aortic arch repair, the use of external branch and fenestrated endografts was associated with high rates of stroke, causing a delay of their global implementation.^2,3 However, the combination of increasing physician experience alongside the subsequent development of adjuncts, such as specific delivery systems, preloaded fenestrations, and inner branches, has improved results, making them a viable option for many patients today.^2,3

Endograft Designs

Two main endograft designs for endovascular arch repair exist today, fenestrated and branched arch endografts. Branched endografts are typically used for proximal arch pathologies, while fenestrated endografts are usually used in pathologies that require sealing in the mid-arch. Depending on the device selected, fenestrated thoracic endografts can incorporate a number of fenestrations and can be combined with a proximal scallop. Graft apposition at the level of the fenestration, normally in the mid-arch at the level of the branch vessels [left subclavian (LSA) or left carotid arteries (LCA)], is required for adequate sealing.² Because of the distance from the femoral arteries and the curvature of the arch, rotation of these devices is difficult to control. Precise deployment relies heavily on preoperative planning, the use of precurved delivery systems and preloaded catheters.^2,3 Currently, there are 3 available f-TEVAR devices in Europe: the Zenith preloaded fenestrated thoracic stentgraft (Cook Medical, Bloomington, IN, USA), the Relay thoracic stent graft (Vascutek, Terumo. Inchinnan, UK), and the Najuta stentgraft (Kawasumi Laboratories, Inc, Kanagawa, Japan). The Relay thoracic stent graft offers the possibility of having a proximal scallop or large fenestrations, which do not require bridging. Similarly, the Najuta stentgraft, which only recently obtained the CE for commercialization in Europe, can incorporate between 1 and 3 large fenestrations that do not require bridging stents for the supra-aortic trunks. While the concept of large fenestrations at the outer curvature to preserve supra-aortic branch perfusion seems feasible, concerns exist regarding the real extent of the proximal seal and the durability of the repair.

The Zenith preloaded fenestrated thoracic endograft is a custom-made device (CMD) with one preloaded fenestration, which can be combined with a scallop (Figures 1 and 2) and has a manufacturing time between 4 and 6 weeks. The potential target vessels of the fenestration ± scallop are the LSA and the LCA, or the LCA and the brachiocephalic trunk [after a carotid-subclavian bypass (CS-bypass)], respectively, enabling sealing in zones 1 or 2, making it suitable for treatment of aortic pathologies encroaching the distal arch, chronic type B dissections (though the risk of type A dissection should be kept in mind, especially if using a proximal scallop), inner curvature arch aneurysms, and arch penetrating aortic ulcers. Although it can be exceptionally used for pathologies that require sealing in zone 0, a branched thoracic endograft would be the preferred endovascular solution in most cases.

The Zenith preloaded fenestrated thoracic endograft is made on a Zenith stent-graft design, with diameter reducing wires, spiralizing wires and with the struts of the scallop fixed down on the introducer. The device is mounted on a Z-Track Plus introducer sheath (20Fr or 22Fr) and attached with a spiral wire, allowing for correct orientation to the appropriate clock position while being advanced to the arch. Available proximal diameters range between 24 and 46 mm, allowing treatment of aortas with a proximal sealing zone diameter between 20 and 38 mm. Clock position of the fenestration and scallops are custom made. Fenestration diameter possibilities include 6 mm, 6×8 mm, 8 mm, or 10 mm, all of which must be stented. The minimum distance between fenestration to scallop edge or to graft edge must be 2 mm, in order to avoid compromising the target vessel. Scallop width can be either 20 or 30 mm, with available stent lengths: 17 mm with scallop height 10 to 16 mm; 22 mm, with scallop height 10 to 21 mm.

Available clinical experience with this graft is mainly composed of small case series, including early procedures during which physicians were still in their learning curve, with mortality and stroke rates as high as 20% and 14%, respectively.^3–6 However, with increasing experience and technical graft modifications potential pitfalls and/or technical errors during delivery and deployment have been identified (mainly wire entanglement and device malrotation), with improving results, with the latest publications reporting mortality rates between 0% and 10% and stroke rates between 0% and 7%.^2–7

The aim of this technical note is to report a detailed step-by-step implantation approach for the Zenith fenestrated preloaded thoracic endograft, identifying potential problems and trouble-shooting solutions at each stage.

Technical Note

1: Access

The main access for the delivery system should be one of the femoral arteries (normally the right), either through surgical cut-down or ultrasound-guided puncture and placement of 2 percutaneous closure systems. The contralateral femoral artery should then be punctured via ultrasound guidance and a 5Fr introducer sheath should be left in place. Once the femoral access has been obtained, ultrasound guided puncture of the left brachial artery should be performed, with placement of a 7Fr and 55-cm long introducer sheath in the LSA or in the LCA (after crossing the bypass). Alternatively, exposure of the left proximal axillary/brachial artery can be made, followed by placement of a 7–9 Fr sheath depending on the bridging stent selected. Systemic heparinization should be administered until an activated clotting time of >250 seconds is achieved.

2: Set-up

Through the main femoral access, an extra-stiff double curve thoracic Lunderquist (Cook Medical, Bloomington, IN, USA) guidewire should be placed in the ascending aorta to the level of the aortic valve, followed by placement of an angiographic catheter at the arch through the contralateral access. Depending on the type of upper extremity access (percutaneous vs cut-down; 7×55 F vs 9×55 F sheath) a 7F EN Snare (Merit Medical Systems, South Jordan, UT, USA) or an 8 F Indy OTW Vascular Retriever (Cook Medical) should be positioned in the distal aortic arch or proximal descending thoracic aorta through the vessel planned for fenestration (LCA/LSA).

3: Through-and-Through Guidewire. Precaution With Wire Entanglement

Once the 3 necessary accesses, sheaths, and guidewires have been positioned, the Zenith CMD preloaded device may be advanced into the distal aortic arch. A long 400-cm hydrophilic guidewire should be inserted into the preloaded catheter located in the delivery system. This preloaded catheter exits the graft at the level of the fenestration and should be snared from the fenestration target vessel (LCA/LSA), creating a through-and-through wire from the main femoral access to the left upper access, taking care to avoid wire entanglement. This maneuver should be performed in the proximal descending aorta if possible, to avoid “trashing” of the supra-aortic trunks during manipulation with the snare.

4: Advancement of the Graft to Its Target Location. Troubleshooting 1

Once the through-and-through has been set up, the endograft can be advanced to its target location. During snaring of the hydrophilic guidewire advanced through the preloaded catheter, the wire has the potential of twisting around either the main graft or the Lunderquist wire. However, this may not be easily visible during stage 3 and will only become evident when the endograft is advanced to its correct position, making the behavior of the through-and-through guidewire critical at this stage (Figure 3A-E).

In the case that the through-and-through wire appears to be twisted around the main graft (Figure 3A and B), different techniques may be followed for troubleshooting:

Retraction of the endograft into the descending aorta and rotation of the delivery system. The direction of the rotation can only be determined by trial and error, with progressive reduction in guidewire entanglement becoming evident upon a correct direction.⁸

Retraction of the endograft into the descending thoracic aorta, achieving a stable position that avoids direct contact between the tip of the device and the aortic wall, followed be retraction of the Lunderquist guidewire (Figure 3C and D). Then, with caution given the potential risk of retrograde type A dissection or thrombus dislodgment, gentle tension is applied to the through and through wire and the Lunderquist guidewire is advanced again to the level of the aortic valve.

Release of the through-and-through guidewire. Retract the endograft and perform stage 3 again, establishing a new through-and-through access.

To confirm adequate positioning of the through-and-through wire and the endograft, critical attention must be paid to the behavior of the through-and-through wire at the level of the fenestration and the response of the 7–9 Fr brachial sheath (Figure 3A, B, and E).

5: Phase 1 Deployment

To achieve a precise and controlled delivery, this step should optimally be performed under fusion guidance and cardiac output reduction, either with the Munich Valsalva Implantation Technique, ventricular rapid over-pacing, vena cava (VC) balloon occlusion or adenosine-induced cardiac arrest.⁹ The endograft should be positioned with the fenestration in front of the target vessel and its correct location should be confirmed with angiography. First, under gentle tension on the through-and-through guidewire to maintain constant retraction of the wire as the endograft is unsheathed, the 2 initial stents should be deployed, taking care not to pull back the delivery system; followed by confirmation via angiography of correct positioning of the fenestration. During this stage, 2 main problems may arise—wire entanglement with the struts of the scallop (Figure 4) and malrotation (Figures 5 and 6).

6: Troubleshooting 2: Wire Entanglement With the Proximal Scallop and Malrotation

If the wire gets entangled at the proximal edge of the endograft during unsheathing, the operator should stop pulling on the through-and-through wire and position the endograft with the fenestration in front of the target vessel, while maintaining the sheath firmly in place.

At this point, various bailout possibilities exist:

Perform a buddy puncture of the upper access sheath, introduce a 5F Bernstein II catheter (Cook Medical) and try to catheterize the fenestration in a retrograde manner. Care must be taken to avoid pulling on the through-and-through, as this may cause reflection of the proximal edge of the endograft. Once the fenestration has been successfully catheterized, its correct position should be verified using a curved angiographic catheter (making sure it twists freely when inside the graft) or with the soft wire constrained inside the graft (Figure 7).

Release of the through-and-through guidewire and complete release of the endograft followed by antegrade catheterization and snaring (Figure 3).

Liberation of the wire through manipulation, either with a catheter or a balloon, from the LSA/LCA. This technique is however difficult and is rarely effective.

In case of significant graft malrotation and unsuccessful cannulation of the fenestration (Figures 5 and 6), avoid extensive manipulation and do not attempt to rotate the graft, as this is dangerous and ineffective. Furthermore, severe retraction or rotation of the endograft should not be performed, as it can potentially cause a type A dissection. If this is the case, the operator should leave a Rosen guidewire (Cook Medical) from the upper extremity access into the ascending aorta on the outside of the endograft to facilitate the option from a chimney in case necessary.

7: Phase 2 Deployment: Troubleshooting 3

The endograft can then be fully deployed, releasing the spiralizing wire, the diameter reducing ties and the proximal and distal fixation systems (Figure 1F). In cases with successful catheterization of the fenestration, the upper access sheath should be advanced into the endograft over the dilator, fixating the position of the fenestration.

In the case that irreversible problems have occurred with the catheterization of the fenestration, another effort to cannulate the fenestration over the retrograde approach with steerable sheaths and sidewinders can be performed. If nothing works, the fenestration should be given up, relined with another TEVAR to occlude the fenestration and prevent leaks, and subsequently followed by either a chimney to the target vessel or with a cervical bypass graft.

8: Removal of the Through-and-Through Wire

From the 7 or 9F sheath located in the left brachial/axillary artery, a buddy wire should be advanced proximally into the endograft (toward the ascending aorta) and exchanged over a catheter with a Rosen wire. Once the Rosen wire is securely positioned in the ascending aorta, the through-and-through wire can be removed, and the dilator of the delivery system can be retracted.

9: Bridging the Fenestration

Cases requiring distal extension should undergo the implantation of the secondary thoracic stent-graft prior deployment of the bridging stent, so as to avoid potential crushing or damage to it with the manipulation.

A balloon-expandable covered stent should be used for bridging, taking care to visualize the vertebral artery take-off before deployment to avoid coverage. Flaring should be performed in the usual manner, normally with a 2-mm larger noncompliant balloon, optimally with the tip of the balloon positioned at the level of the endograft. Confirmation angiography, making sure there are no distal problems (kinks, stenosis, dissection) should be performed, and if necessary, the bridging stent can be relined with a bare metal nitinol stent.

10: Completion Angiography and Closure

A final control angiography should then be performed, confirming patency of all supra-aortic trunks, absence of any complications with the bridging stent, as well as the absence of type I or III endoleaks. Endovascular materials can then be removed, followed by closure (percutaneous/cutdown) of the vascular accesses.

Discussion

The Zenith preloaded f-TEVAR allows treatment of pathologies encroaching the distal aortic arch, offering an attractive treatment alternative for high-risk patients, redo-sternotomies, and the elderly. Alternative treatment possibilities include coverage of the LSA without revascularization, cervical debranching of the supra-aortic vessels, chimney, and periscope techniques, as well as branched devices.⁵

Though some centers perform coverage of the LSA during urgent TEVAR with a low risk of clinically significant sequelae, it has been associated with arm claudication, vertebral territory and anterior circulation stroke, and spinal cord ischemia, especially in patients that require extensive aortic coverage or are at high risk for spinal cord ischaemia.¹⁰ In elective cases, the latest consensus regarding treatment of the aortic arch states that preventive LSA revascularization should be considered to reduce the risk of neurological complications, such as stroke and spinal cord ischemia (class IIa, level B).² Cervical debranching (CS bypass or subclavian artery transposition) in patients with aortic arch disease has been associated with rates of 11.4% of local bleeding complications, 10.4% reinterventions, 9.5% peripheral neurological damage and short-term mortality rates of 7.6%, considerably worse outcomes than in patients without aortic arch disease.¹¹ Other endovascular alternatives, such as chimneys and periscopes, have been associated with rates of up to 40% of early type I endoleaks, and a 30-day mortality rate of 11% (range 0%–29%; pooled for both elective and urgent patients).^2,12–14 Furthermore, endografts have not been purposefully design to accommodate chimneys or periscopes, thus the radial force, elasticity, shape and even length will suffer modifications, typically associating worse hemodynamic parameters when compared to specifically designed grafts.^2,14

When compared with branched TEVAR, f-TEVAR poses several advantages. First of all, f-TEVAR allows sealing in the mid-arch as opposed to the ascending aorta, of special importance when considering that dilated or aneurysmatic ascending aortas are one of the most important factors precluding endovascular arch repair.³ Other advantages of f-TEVAR are that it is typically easier, requires less vascular accesses, less fluoroscopy and contrast usage, as well as having shorter operating times. A study including patients treated between 2012 and 2014 with f-TEVAR vs branched-TEVAR, reported a mean operating time of 153±23 vs 270±26 minutes, respectively.³ Another study comparing f-TEVAR vs LSA debranching plus TEVAR for treatment of distal aortic arch and descending aortic lesions reported a mean endovascular operative time of 191±120 minutes for f-TEVAR versus 130±75 minutes for debranching TEVAR (p = nonsignificant), with an additional mean operative time for the debranching procedure of 181±97 minutes.¹⁵ In this sense, benefits of f-TEVAR in comparison with LSA debranching plus TEVAR include the need for only intervention and a shorter total operating time. The same study reported 0% 30-day death and major stroke rates; however, a 29.4% rate of local complications in patients undergoing LSA debranching. Additionally, at 15-month follow-up, the unplanned aortic-related reintervention rate was 35.3% for the debranching group vs 10.5% in the f-TEVAR group.¹⁵

Despite these benefits, f-TEVAR has been associated to a risk of entanglement of the preloaded catheter and wire, which can complicate the procedure and increase manipulation in the aortic arch, potentially increasing the risk of stroke.³ Some of these challenges have been ameliorated by the fixation of the free struts and scallop edges to the dilator, reducing the risk of entanglement; however, current series have reported rates of wire-entanglement of over 20%.^5,7 As placement of the fenestrations at the accurate clock position cannot be achieved by the delivery system only, we believe that the tension on the through-and-through brachio-femoral wire during deployment allows for additional correction of the endograft and fenestration orientation. Additional tools to aid correct alignment of the fenestration to the target vessels include a spiral wire attachment of the stent graft to the delivery system, and a curved self-orientating delivery system.⁵ However, despite its high rates of entanglement, we consider the through-and-through wire a valuable tool to assist and improve the orientation and should remain in the design of fenestrated arch endografts. With these technical considerations in mind, physician must be aware of 3 technical errors that may occur during these procedures⁸:

Through-and-through wire entanglement around the sheath/guidewire

Through-and-through wire entanglement with the struts of the scallop

Malalignment or malrotation of the graft.

Although improvements in the design have diminished the rates of wire entanglement, and the design of the endograft provides a platform through which the graft will theoretically orient itself properly in the arch, technical complications are still frequent, especially at the beginning of the learning curve. Leong Tan et al⁶ report their early experience with a preloaded Zenith fTEVAR device, with an 86% technical success rate (6/7). Unsalvageable malrotation of the endograft was observed in 1 patient, which was successfully remedied by converting the procedure to a chimney technique.⁶ In this same patient cohort, they report wire entrapment around the proximal stent struts in one case.⁶ Another series including 15 cases of preloaded f-TEVAR, obtained a technical success of 93.3% with failure of 1 case due to proximal displacement of the stentgraft.³ One of the largest and most recent publications, including a total of 44 patients, reports a technical success rate of 95% (2 patients), with 2 failures (1 secondary to 1 type A retrograde aortic dissection and one misplaced stent graft resulting in major stroke).⁵ Unfortunately, they do not report the percentage of wire entrapment. In a recent multicenter collaboration reporting on 108 patients, the technical success was 99%, considerably higher than that previously reported, despite a 29% rate of wire entanglement.⁷

Though CMD fenestrated arch grafts are only suitable for a selected number of patients—elective repairs of patients with distal arch pathology, with a landing zone between Ishimaru zones 0–2, with a maximum diameter of 38mm and which allow for stent-graft apposition at the level of the supra-aortic trunks, they are fundamental in the endovascular armamentarium for treatment of complex aortic disease and are increasingly being used. This technical note describes the step-by-step procedure that should be followed to minimize technical problems during delivery and deployment, giving possible troubleshooting solutions for potential complications, with the objective to ameliorate the learning curve for new operators, diminishing mortality and stroke rates associated to these procedures, especially for new practitioners.

Conclusion

Three principal complications can occur during deployment of a Zenith preloaded f-TEVAR: entanglement of the through-and-through guidewire around the delivery sheath or the main guidewire, entanglement with the proximal struts, and device malrotation. With a critical eye and a few bailout possibilities, most of these potential complications can be avoided.

Footnotes

Declaration of Conflicting Interests

The author(s) declared the following potential conflicts of interest with respect to the research, authorship, and/or publication of this article: Robert Binskin is an employee of Cook Medical, who collaborated on this proyect through verification of the technical characteristics of the endograft design.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

ORCID iDs

Carlota F. Prendes

Tilo Kölbel

Nikolaos Tsilimparis

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