Endografts with mini-cuff-augmented fenestrations for endovascular repair of thoracoabdominal aortic and common iliac artery aneurysms

Introduction

Fenestrated and cuffed-branched endografts have brought thoracoabdominal aortic aneurysms (TAAA) into the realm of endovascular aneurysm repair (EVAR). ¹ This has been accomplished by both custom-manufactured endografts and physician-modified endografts (PMEG) with comparable results. ² In general, fenestrations are appropriate for preserving flow into aortic branches arising in areas where the endograft comes into contact with the aortic wall and cuffed-branches for aneurysmal zones. ³ Addition of mini-cuffs to fenestrations to improve sealing could enable its use in aneurysmal zones. ⁴ Mini-cuffs increase the length of overlap between the fenestration edge and the fenestration stent without significantly increasing the bulk of the endograft. In this report, we describe a technique of creating mini-cuff-augmented fenestrations (MCAF) in PMEGs using vascular graft and illustrate its use in a patient with TAAA who underwent fenestrated-EVAR. A highlight of the same case is the initial use of MCAFs to preserve flow into the internal iliac arteries (IIA) during bilateral common iliac artery (CIA) aneurysm EVAR, a situation usually managed with iliac branch devices, ⁵ but which was not feasible here because of distal CIA narrowing. This problem was overcome by using tapered iliac limb endografts in which pre-cannulated MCAFs were created to preserve flow into the IIAs.

Technique

Illustrative case

A 62-year-old male smoker, with symptomatic chronic obstructive airway disease, systemic hypertension, bilateral inguinal hernia, and obstructive benign prostatic hypertrophy, presented with progressive abdominal pain that had become severe. Computerized tomography angiography (CTA; Figure 1) revealed a large (88 × 68 mm), calcific, thrombus-lined, Crawford extent-3 TAAA whose cranial limit was at a sharp angulation in the lower descending thoracic aorta. There were two right renal arteries of equal size. Aneurysmal disease extended into both CIAs but spared the terminal portion, which was narrow (<8 mm) due to calcific atherosclerotic disease. Both IIAs were patent and 5–6 mm in diameter. Fenestrated-EVAR using PMEGs was deemed the best treatment option in this situation and was preferred over open surgery in view of the extent of disease and associated co-morbidities. Preservation of both IIAs was considered necessary to prevent spinal cord ischemia.

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Figure 1.

Baseline computerized tomography angiography reconstructed images in (a) anterior, (b) left lateral, and (c) posterior views, showing a large, calcified, partially thrombosed Crawford extent-3 thoracoabdominal aortic aneurysm with bilateral common iliac artery extension. Colored arrows indicate dual right renal arteries (blue), celiac artery (pink), superior mesenteric artery (green), left renal artery (white), bilateral internal iliac arteries (red), and narrowed terminal portions of both common iliac arteries (yellow).

Preparation of endografts with MCAFs

The technique of making MCAFs is described in Figure 2. Fenestrations are made using a circular thermal cautery instrument ⁶ and its edges are reinforced with a double loop of 0.014-inch radio-opaque wire (Fielder, Asahi Intecc, Aichi, Japan) affixed with continuous interlocking 6–0 polypropylene suture. A short length of straight thin-wall expanded polytetrafluoroethylene vascular graft (Impra, BD/Bard, Covington, GA, USA) of the same diameter as the fenestration is positioned within the fenestration with slight outward projection and attached to the fenestration edge using continuous nonlocking 5–0 polypropylene suture. The vascular graft is then everted, and its length trimmed so that it projects 3–4 mm outside the endograft. It is dilated with a noncompliant balloon of the same diameter at high pressure to smoothen out wrinkles and achieve the nominal diameter of the vascular graft. Relaxed stay sutures, anchored to adjacent endograft stent struts, are taken through three or four equidistant points on the outer edge of the vascular graft to prevent invagination.

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Figure 2.

Diagrammatic representation of the steps involved in creating mini-cuff-augmented fenestrations. (a) An endograft, represented by parallel vertical blue lines, is fenestrated (b) at a predetermined point. (c) The fenestration edge is reinforced with a double loop of 0.014-inch radio-opaque wire fastened with continuous interlocking 6–0 polypropylene suture (colored red). (d) A 2-cm length of straight thin-wall expanded polytetrafluoroethylene vascular graft (colored purple) of the same diameter as the fenestration is positioned within the fenestration with 1 mm outward projection. (e) The vascular graft is attached to the fenestration edge using continuous nonlocking 5–0 polypropylene suture. The vascular graft is then everted (f) and its length trimmed (g) so that it projects approximately 3–4 mm outside the endograft. The vascular graft is dilated (h) with a noncompliant balloon of the same diameter at high pressure to smoothen out wrinkles. (i) Relaxed stay sutures (colored green), anchored to adjacent endograft stent struts, are taken through three or four equidistant points on the outer edge of the vascular graft to prevent invagination.

Using strict sterile technique, a 30–30-192 mm Valiant Captivia endograft (Medtronic Vascular, Santa Rosa, CA, USA), was fully deployed on a sterile table without releasing the tip-capture mechanism. Based on detailed study of CTA images of the patient’s vascular anatomy, five MCAFs were made (Figure 3(a) and (b); Supplementary Table 1), four of which were pre-cannulated to facilitate catheter crossing using two shared 300 cm nitinol guidewires (Roadrunner, Cook Medical, Bloomington, IN, USA)—one 0.014-inch and one 0.018-inch. Each wire looped through two fenestrations and the ends trailed parallel to the endograft delivery system after exiting a needle hole created in the introducer sheath. After deployment of the fenestrated aortic endograft in the patient and removal of the delivery system, these wires will emerge from the femoral arterial access and can be easily differentiated based on tip hardness and wire thickness. Catheters riding up either end of these guidewires will reliably cross the corresponding MCAF, after which a parallel guidewire can be passed into the target vessel through the catheter (Figure 4). The process is repeated over the other end of the guidewire, after which the loop is removed by pulling on its hard end. MCAFs located in large aneurysmal areas do not need to be pre-cannulated as they can be reliably crossed using steerable sheaths (Figure 5(b)).

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Figure 3.

Physician-modified Valiant Captivia (a, b) and Endurant iliac limb (c) endografts. Colored arrows (except red and yellow) indicate mini-cuff-augmented fenestrations made using vascular graft for the celiac artery (green), superior mesenteric artery (purple), dual right renal arteries (blue), left renal artery (black), and internal iliac artery (brown). Red arrows (in a and b) indicate two pre-cannulating nitinol guidewires, one shared by the superior mesenteric and left renal artery fenestrations, and the other by the dual right renal artery fenestrations; each of these guidewires loop through two fenestrations and their ends enter the introducer sheath (seen on the extreme right of images a and b). Yellow arrows in image A indicate welds in each stent segment, which should remain in a straight line after re-sheathing to ensure there is no twist in the endograft. In image c, a guidewire (red arrows) runs along the entire length of the endograft moving from inside to outside through the fenestration as it passes from top to bottom; the last two stent segments of this endograft have been temporarily tied down with 2–0 silk (as will the rest) in preparation for endograft re-sheathing. Also seen in image c, just above the brown arrow, is the cut zig of stent segment 5 making room for the fenestration.

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Figure 4.

Diagrammatic representation of visceral aortic branch wiring through pre-cannulated mini-cuff-augmented fenestrations (MCAF) made in an aortic endograft. 6 F catheters (dotted arrows) riding up both ends of a femoral-femoral 0.014/0.018-inch nitinol guidewire (hollow arrow) that loops through two MCAFs (solid arrows) made in an endograft cross the corresponding MCAFs reliably and allow passage of parallel steerable guidewires (two-tailed arrows) into target aortic branches through them.

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Figure 5.

Intra-operative images during endovascular aneurysm repair. (a) Fenestrated aortic endograft being moved into position guided by the pre-marked visceral aortic branches. (b) Celiac artery fenestration cannulated using a steerable sheath. (c) Iliac limb endograft with single fenestration (white arrow) oriented towards the marked right internal iliac artery (IIA); the guidewire pre-cannulating the fenestration has been exteriorized through a catheter in the left common iliac artery. (d) Iliac limb endograft with single fenestration (white arrow) oriented towards the marked left IIA. (e) Kissing-balloon dilatation of the stents in the right external and internal iliac arteries. (f) Second covered stent deployment in the right IIA after the first disconnected from its fenestration. Contralateral 10 F sheath (white arrow) stabilized by a femoro-femoral guidewire loop and coaxial 6 F sheath (black arrow) are seen sandwiched between two overlapping right iliac endografts.

Two 16–10-93 mm tapered iliac limb endografts (Endurant, Medtronic; Figure 3(c)) were also fully deployed on the sterile table and one pre-cannulated 5 mm MCAF was made in each of them at the taper zone located between stent segments 5 and 6 from the top after removal of the apex of a strut zig; here the pre-cannulating guidewire did not loop back but ran along the entire length of the endograft moving from inside to outside through the MCAF as it passed from top to bottom. Per-operatively the top end of this guidewire was exteriorized from the contralateral femoral artery to allow a catheter to ride retrograde over it and cross the MCAF after endograft deployment in the ipsilateral iliac artery. A parallel guidewire can then be passed into the ipsilateral IIA through the catheter.

None of the endografts were constrained. All three endografts were re-sheathed similarly: each stent segment was tied down using 2–0 silk (Figure 3(c)) and these ties were sequentially removed as re-sheathing progressed. Care was taken to ensure there was no twist in the re-sheathed endograft (Figure 3(a)). Endograft re-sheathing was not hampered by the presence of MCAFs or by the presence of the pre-cannulating guidewires. The aortic endograft took approximately 2 h to prepare and the iliac limb endografts about 30 min each.

Procedure

The procedure was performed under general anesthesia after obtaining written informed consent from the patient for the planned procedure and for use of PMEGs. The study was approved by the Institutional Review Board. A ceiling mounted Allura FD 10 Xper cardiovascular X-ray system (Philips, Amsterdam, Netherlands) was used; fusion imaging was not available. The mean arterial pressure was maintained above 90 mmHg throughout the procedure. A spinal drain was not used. The patient was kept heparinized throughout the procedure with activated clotting time maintained at 300–350 s. Duplex ultrasound guidance was used to obtain bilateral femoral and left brachial arterial percutaneous accesses. Proglide sutures (Abbot Vascular, Santa Clara, CA, USA) were pre-laid in the femoral artery accesses. All target arteries were pre-marked: the superior mesenteric artery and the three renal arteries were marked using 4/6 F angiographic catheters and 0.014-inch guidewires inserted through four punctures made in the valve of a 14 F sheath in the left femoral artery; the celiac artery was similarly marked from the left brachial access (Figure 5(a)). Details of endografts used in the procedure are provided in Supplementary Table 2. Initially a Valiant Captivia 30–26-152 mm endograft was deployed with its lower end just above the celiac artery. Next, the fenestrated aortic endograft was deployed after orienting the fenestrations towards their respective pre-marked target branches (Figure 5(a)). After removal of the delivery system an 18 F sheath was inserted over the ends of the pre-cannulating wires. All MCAFs were stented using a balloon-expandable covered stent 1 mm larger in diameter than the MCAF and lined internally with a self-expanding nitinol stent (Supplementary Table 1); the latter was done because only older (less robust) iterations of balloon-expandable covered stents were locally available.

The fenestrated 16–10-93 mm iliac limbs were then deployed, first on the right side, while keeping the IIA marked from the left brachial access (Figure 5(c) and (d)). A 10 F 40 cm contralateral sheath (Flexor Check-Flo, Cook) stabilized internally with a taut femoro-femoral 035-inch guidewire loop was used to facilitate delivery and deployment of the IIA fenestration stents (Supplementary Table 1) through a long 6 F sheath (Ansel, Cook). After this a 32–20-166 mm bifurcated aortic endograft extended below with a 20–20-82 mm iliac limb (both Endurant) were sequentially introduced from the right femoral artery and deployed overlapping the fenestrated aortic endograft above and the fenestrated right iliac limb below. However, passage of the 20 F bifurcated aortic endograft through the narrow terminal right CIA resulted in disconnection of the right IIA stents from its MCAF despite prior kissing-balloon dilatation of the right external and internal iliac arteries (Figure 5(e)). As the femoro-femoral wire loop was still present, it was possible to deploy another pair of stents to restore sealing (Figure 5(f)). Finally, the contra-limb of the bifurcated aortic endograft was extended into the fenestrated left iliac limb with a 16–20-156 mm iliac limb (Endurant). The total fluoroscopy time was 204 min, procedure time 378 min, and contrast volume 380 mL.

Outcome

Final angiography (Figure 6) was satisfactory. The patient was extubated on the table. No neurological deficits were noted. The post-operative period was uneventful, and he was discharged home after five days. CTA after six months showed patency of all endografts and stents, decrease in sac size and lack of endoleak (Figure 7). He continues to do well one year later. Two additional symptomatic TAAA cases have completed six-month follow-up successfully after fenestrated-EVAR using PMEGs with MCAFs at our center (Supplementary Figures 1 and 2).

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Figure 6.

Completion angiograms after endovascular aneurysm repair showing (a) lower thoracic and upper abdominal aorta, (b, c) abdominal aorta, and (d) iliac arteries. All images are in anteroposterior projection except (c), which is in right lateral projection. All endografts and fenestrations stents show good flow. There is no evidence of endoleak.

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Figure 7.

Computerized tomography angiography images obtained at six-month follow-up. Reconstructed images in anterior (a) and lateral (b) views show undistorted and patent endografts and fenestration stents and no endoleak. Axial images at the renal (c) and common iliac artery (d) levels show complete thrombosis of the aneurysm sac and patent endografts and renal fenestration stents.

Discussion

In the only report on MCAF so far, Oderich et al. ⁴ described attachment of mini-cuffs fashioned from a self-expanding covered stent (Viabahn, W.L.Gore, Flagstaff, AZ, USA) to two fenestrations to improve sealing in a patient undergoing TAAA fenestrated-EVAR with a PMEG. Our technique of using vascular graft to fashion MCAFs was effective in preventing endoleak despite fenestrations being located within the aneurysmal zone. Straight thin-wall expanded polytetrafluoroethylene vascular graft has a low profile and can be turned inside-out (unlike the Viabahn covered stent). This enables taking a continuous nonlocking suture that wraps the proximal end of the vascular graft over the edge of the fenestration which provides a robust seal (Figure 2(e)). Subsequent eversion of the vascular graft is associated with slight inward projection at the point of eversion (Figure 2(f)), which increases overlap between the MCAF and the fenestration stent and reduces the requirement for outward projection of the MCAF. Vascular graft, however, is supple and MCAFs made from it require external stay sutures to prevent graft invagination.

Mini-cuffs do not appreciably increase the bulk of the endograft because of their very short length. This obviates the need for a smaller endograft diameter in the visceral zone as in custom-manufactured cuffed-branched endografts. Nevertheless, it would be prudent to avoid making two MCAFs at the same level in the endograft if it is the largest available in a particular size of delivery system because of the limited extra space available. In the Valiant Captivia product range, 32 mm diameter endografts are the largest available in 22 F delivery systems and 40 mm diameter endografts in 24 F delivery systems. Pre-cannulation of MCAFs facilitates catheter crossing even if the MCAF abuts the aortic wall and prevents inadvertent double wiring of a fenestration into two aortic branches.

MCAFs, as designed in this report, lack directionality, unlike cuffed branches of custom manufactured endografts. This is advantageous because it makes MCAFs suitable for any orientation of aortic branches; it also makes MCAFs easy to enter from a femoral or brachial approach. MCAFs retain the major advantage of fenestrations over cuffed branches of requiring shorter covered stents, which could translate to better long-term patency. ¹ In a large single-center experience of TAAA EVAR using custom-manufactured endografts, fenestrations had better long-term patency, but a higher rate of branch endoleak than cuffed-branches, suggesting a trade-off between branch endoleak and patency with currently available technologies. ¹ MCAFs have the potential to offer the best of both techniques, combining long-term patency with good sealing. Flaring of the proximal ends of balloon-expandable covered stents (which is the norm with commercially manufactured reinforced fenestrations to achieve good sealing) is not required with MCAFs because of the greater length of overlap available for sealing and the use of stents slightly larger in diameter than the MCAF.

EVAR of CIA aneurysms is usually accomplished using iliac branch devices. ⁵ However, distal CIA narrowing makes deployment of conventional iliac branch devices difficult. This has prompted the development and use of custom-manufactured fenestrated iliac endografts (Anaconda, Vascutek-Terumo, Inchinnan, UK). ⁷ , ⁸ Alternative fenestrated endograft techniques to preserve IIA flow have included bail-out in situ fenestration ⁹ and onsite fenestration of an Endurant tapered iliac limb ¹⁰ ; in the latter case the fenestration had a strut going across it which prevented fenestration stenting. Our technique of removal of the apex of a strut zig allows creation of a MCAF that can be stented and provides superior sealing. This should not compromise the integrity of the iliac limb as >90% of this stent segment remains attached to the endograft. In the Anaconda fenestrated iliac endograft, space is created for the fenestration by omitting an entire stent segment.

Onsite modification of standard endografts involves a trade-off between the advantages of making devices appropriate for the patient’s anatomy available rapidly and at significantly lower cost than custom-made endografts and the disadvantages of lacking industrial quality control, voiding of any guarantee of safety by the manufacturer and the investment of time spent in modifying the endograft. Complications of standard EVAR procedures may occur here as well. Open repair, which avoids the need for endograft modification, must be considered in all such cases if the associated risks are acceptable.

Conclusion

Onsite creation and clinical use of MCAFs made using polytetrafluoroethylene vascular graft in TAAA fenestrated-EVAR is feasible. MCAFs can also be made in iliac limb endografts and be used to preserve flow into IIAs. MCAFs accomplish effective sealing despite being in aneurysmal zones, while preserving the advantages of fenestrations over cuffed branches.

Supplemental Material

Supplemental Material

Supplemental Material