The Endowedge and Kilt Techniques to Achieve Additional Juxtarenal Seal during Deployment of the Gore Excluder Endoprosthesis
Article Outline
The proximal 4 mm of the Gore Excluder endoprosthesis are scalloped. Our purpose is to describe our initial experience of a novel technique, referred to as the “endowedge,” that takes advantage of this scalloped configuration in aneurysms with short proximal necks. The technique utilizes a balloon in the renal artery to aid alignment of a scallop and allow additional juxtarenal seal. A retrospective review of aneurysms treated with the endowedge technique at our institution was initiated. Renal balloons were placed via the brachial approach. Excluder endografts were deployed by flowering the first one or two rings, then advancing upward against the inflated balloon during completion of deployment. In patients with dumbbell-shaped morphology, an aortic cuff was deployed in the distal seal zone prior to the main body (kilt technique). Eight patients were identified, three of whom underwent an adjuvant kilt procedure. Average preoperative proximal neck length was 8.5 mm (range 6-12). Average additional juxtarenal seal was 2.3 mm. Mean follow-up was 5 months (range 2.5 weeks to 9 months). There were no type I endoleaks. There were two type II endoleaks. Average aneurysm size decreased from 6.0 to 5.5 cm. No aneurysm has enlarged or ruptured. We conclude that the endowedge technique allows additional juxtarenal seal during endograft placement. Our early results suggest that this technique may allow for safe treatment of aneurysms with short necks.
INTRODUCTION
Successful endovascular exclusion of abdominal aortic aneurysms is dependent on formation of a seal between the endoprosthesis and the nona-neurysmal aorta. Recommendations for suitability of endovascular repair have generally focused on preoperative anatomic characteristics of the proximal aortic neck. Important anatomic characteristics that must be considered include the length of the neck and the amount of calcification, thrombus, and angulation. In terms of neck length, general recommendations have been a minimum of 15 mm.1 However, the amount of proximal seal zone achieved during endograft placement is determined not only by the length of the proximal neck but also by the position of the deployed graft.
The Gore (Flagstaff, AZ) Excluder endoprosthesis is unique in that its proximal 4 mm are scalloped. Therefore, if the graft is aligned with a trough at the renal artery, an additional 4 mm of juxtarenal proximal seal can be achieved (Fig. 1). We describe our experience using a balloon in the renal artery during endograft placement to achieve additional seal in patients with short proximal necks. We refer to this technique as the “endowedge.” In addition, we describe the use of a predeployed aortic cuff (or kilt) to effectually extend the main body of the Excluder endoprosthesis (Fig. 2). This procedure can be used as an adjuvant to the endowedge to take advantage of distal seal zones in patients with dumbbell-shaped or double aneurysms.
Fig. 1.
a The top of the Gore Excluder endograft is scalloped. Proper alignment of the lowest renal artery with the trough of a scallop could potentially achieve an additional 4 mm of seal. b Postoperative three-dimensional CT reconstruction of a patient who underwent aneurysm exclusion with an endowedge technique.
Fig. 2.
A predeployed aortic cuff (or kilt) can be used to effectually extend the main body of the Gore Excluder graft to take advantage of additional distal seal zones.
METHODS
A retrospective review of patients who have undergone endovascular exclusion of abdominal aortic aneurysm using the endowedge technique at our institution was initiated. Patients were considered for the procedure if they had large, expanding, or symptomatic aneurysms and significant risk factors for open repair. Preoperative proximal neck length was based on high-resolution axial computed tomographic (CT) slices and considered the distance from the lowest renal artery to the point where the aortic diameter excecded the maximum recommended diameter of the proposed endograft. Neck angulation was determined by intraoperative anterior-posterior aortography. Outcomes evaluated included technical success rate, postoperative aneurysm size, presence of endoleak, presence of postoperative graft migration, and renal function.
All procedures were performed in the operating room using an OEC 9800 (GE Healthcare Technologies, Waukesha, WI) C-arm. Maximum magnification was routinely employed, and the image intensifier was rotated in both the cranial-caudal and lateral anterior oblique planes to account for parallax, as determined by multiplanar CT reconstruction of the course of the aorta and lowest renal artery.
Procedural Details
The endowedge. A balloon is partially advanced into the lowest renal artery from a brachial approach through a 6 French, 70 cm Raabe sheath (Cook, Indianapolis, IN). The Excluder graft is positioned just distal to the balloon. The balloon is inflated to nominal pressure. The endograft is then deployed using a slow technique, as previously described.2 During the initial flowering of the graft, the graft is advanced upward against the balloon to wedge a trough of the scalloped graft against the balloon (Fig. 3). With experience, we found improved results with earlier engagement of the balloon. Also, a slight twist of the graft back and forth during engagement helps with the alignment of trough with balloon. Upward pressure is maintained and the slow deploy continued until the contra limb is released to assure secure graft position. Aortic angioplasty is then performed to firmly seat the graft. The remainder of the endograft procedure is then completed in standard fashion.
Fig. 3.
The endowedge technique. a Preoperative aor-togram demonstrating a short, angulated neck. b Magnified view after correction for parallax. c A balloon is inflated in the lowest renal artery via the brachial approach. d The Excluder endoprosthesis is flowered in a slow deploy technique while advancing the graft upward. e, f The balloon is engaged early and a slight, twisting movement back and forth ensures proper alignment of the balloon and a scallop of the graft. g Upward pressure is maintained until the contra limb is released, at which point the graft is well seated. Note that a favorable tilt in this angulated neck is assured since the endowedge, in effect, exerts a downward force along the inner curve of the graft. h Completion angi-ography demonstrating no endoleak and patent renal arteries.
The kilt. In cases of dumbbell-shaped aneu-rysms, an aortic extension cuff is deployed prior to the main body in the distal second seal zone (Fig. 4). The diameter of the cuff should match that of the main body. The top of the cuff should be no more than 1.5 cm distal to the target landing site of the main body as that device begins to taper at 2 cm. In fact, more overlap is preferred and a second predeployed cuff should be considered if concerns of inadequate overlap exist. However, the minimum distance is 1 cm to allow room for seating of the main body's anchors (which extend down to approximately 9 mm from the top of the graft). Finally, since the cuff deploys from hub to tip, it is performed in rapid fashion.
Fig. 4.
The kilt technique. a Preoperative multiplanar CT reconstruction (coronal view) of a patient with a dumbbell-shaped aneurysm. b An aortic cuff (or kilt) is deployed in the distal seal zone prior to performing an endowedge with the main body. c Completion angiography after kilt and endowedge technique. d Multiplanar CT reconstruction performed on postoperative day 2 demonstrating resolution of the proximal portion of the dumbbell-shaped aneurysm and no endoleak.
RESULTS
Eight patients were identified. Average age was 76 years (range 71-87). Average preoperative proximal neck length was 8.5 mm (range 5-12). Average neck angulation was 31 degrees (range 0-60). Three patients had dumbbell-shaped or double aneurysms and underwent an adjuvant kilt procedure to achieve additional distal seal. One patient had symmetrically positioned renal arteries and underwent a bilateral endowedge using a stent in the stenotic right renal artery and a balloon in the left renal artery. In retrospect, although proximal seal was achieved, the renal stent compromised our ability to seat the endograft with aortic angioplasty. We now prefer to perform any necessary adjuvant renal stenting only after the main body of the aortic endoprosthesis is firmly seated and the proximal seal has been confirmed by aortography.
In terms of technical success, proximal seal was achieved in all cases. However, one case (our first) required a proximal aortic cuff to achieve seal. In that case, the slow deploy was continued only for the first couple of rings, converting to a rapid deploy once the graft position was felt to be adequate. However, the graft slipped and tilted during this part of the deployment. The target side landed flush to the renal, but there was initial loss of seal along the contralateral renal side of the graft, necessitating the cuff. The incident directly led to our recommendation to continue the slow deploy until the contra limb is released.
The average amount of additional juxtarenal seal achieved was 2.3 mm (range 0-4). We were able to achieve the full 4 mm of potential additional seal in three of the eight cases, all of which occurred later in our series, indicating a learning curve to this technique.
Postoperative CT follow-up has ranged from 17 days to 9 months (mean 5 months). There have been no type I endoleaks and no incidence of graft migration. There have been two type II endoleaks. No aneurysm has increased in size or ruptured. Three aneurysms have decreased in size by 5 mm or more.
One patient died (on postoperative day 17) of a massive upper gastrointestinal bleed. A CT scan 2 weeks prior had shown no endoleak, patent renal arteries, and no suggestion of bowel adhesion to the graft or aorta. Serum creatinine drawn at the time of his attempted resuscitation was 4 mg/dL. Serum creatinine 2 days earlier was 1.1 mg/dL. Preoperative creatinine was 0.8 mg/dL. The patient had known prostate cancer. An autopsy was not performed. None of the other patients has had a change in postoperative creatinine±0.2 mg/dL. All postoperative CT scans have shown patent renal arteries.
DISCUSSION
Up until now, treatment strategies for endoluminal exclusion of aneurysms with short necks have generally focused on the use of fenestrated grafts. This procedure requires the alignment of custom-made holes with the visceral vessels during deployment of the graft. The visceral vessels are then stented with a significant portion of the stent protruding into the aorta. The aortic portion is then flared in an attempt to effectively rivet the fabric of the graft to the aortic wall.
The use of fenestrated grafts to treat aneurysms with short necks was pioneered by Anderson et al.3 and Lawrence-Brown et al.4 Since then, several other reports have validated the feasibility of this technique.5, 6, 7 The current largest published series to evaluate long-term results involved 32 patients.8 Twenty-two had neck lengths ranging 3-10 mm. Ten had neck lengths ranging 10-15 mm with concomitant angulation or thrombus. Postopera-tively, one early type I and one early type III en-doleak were treated with reintervention. Sac shrinkage (>5 mm) was noted in 15 of 26 patients at 6 months. No late deaths from the treated aneurysms were reported. One patient had aneu-rysm growth±5 mm.
There are several limitations to fenestrated grafts. The most immediate is the limited availability of the graft as it is not currently approved for use in the United States by the Food and Drug Administration. In addition, the grafts must be custom-made for each case based on the patient's individual anatomy. There are technical limitations as well. The fenestrations must be aligned precisely prior to deployment of the graft or visceral ischemic complications can occur. Haddad et al.9 reported a high incidence of adverse renal events in 72 patients undergoing placement of fenestrated grafts. In that series, adverse renal events were noted in 16% of patients without preoperative renal dysfunction and 39% of patients with preoperative renal dysfunction. Overall, after graft placement, there were 10 renal artery stenoses, five renal artery occlusions, and four patients requiring hemodialysis.
The endowedge technique has many features that make it an attractive alternative to fenestra-tion. The technique is performed with a standard, unmodified Gore Excluder graft. We chose to use the Excluder because of its scalloped configuration and our favorable experience with adjusting the position of the graft during deployment for precise placement.2 In addition, the renal artery is protected during deployment by the balloon, and any scallop on the graft can be wedged into alignment during deployment. In our small series, we saw no immediate postoperative renal dysfunction. Unfortunately, the etiology of the one case of later renal dysfunction in our series is unknown. However, we feel it is unlikely to have been secondary to the endograft-related ischemia as this would require proximal migration of the endo-graft. This phenomenon has been reported only once and occurred immediately postoperative in a patient with a tight concentric narrowing just above the most proximal aspect of the aneu-rysm.10 Thromboembolism from the top of the graft represents another possible etiology, but the contralateral, uninvolved renal artery should not have been affected. Further experience is necessary to clarify the effect of this procedure on renal function.
In terms of seal, a fenestrated graft does provide more seal than is achieved with the endowedge technique. However, unless the renal arteries have vastly asymmetric origins, most of the additional seal is suprarenal. Since it is actually the maximization of the infrarenal seal that prevents the endoleak via the fenestration, which aneurysms benefit from this more complex procedure will need to be determined. The suprarenal zone may provide additional fixation, but it should be noted that studies showing a clinical benefit to suprarenal fixation were done in comparison to the AneuRx (Medtronic, Santa Rosa, CA) device, which provides no active fixation.11 Data on the Gore Excluder device demonstrate that active infrarenal fixation is effective at preventing graft migration.12
The minimum amount of seal required for successful sustained exclusion of aneurysms remains unknown. Clearly, if there is no infrarenal seal, neither the endowedge technique nor fenestration will be successful. Branched grafts represent a potential future option in these patients.13, 14 When interpreting our results, it should be noted that the shortest neck in the subgroup of patients treated with the endowedge alone (i.e., without adjuvant kilt) was 9 mm. Therefore, we cannot currently recommend this specific treatment strategy in patients with shorter necks. The three patients in our series with necks <9 mm had a second seal zone that was utilized with the kilt technique. This technique is a valuable adjunct for dumbbell-shaped aneurysms, essentially extending the functional length of the main body of the graft. As opposed to deploying the main body low in the second seal zone then building up with extension cuffs, a kilt has no risk for type III endoleak and allows utilization of the endowedge technique with the main body for the proximal seal. It also keeps the fixation devices in the proximal seal zone and maintains the standard position and lengths of the limbs of the graft. It is not reported if any of the aneurysms treated with fenestrated grafts had additional distal seal zones that contributed to aneurysm exclusion. Since fenestration is based on the Zenith (Cook) graft, which has a long body, these second seal zones would have been utilized.
Another important consideration when determining the amount of potential seal is the degree of angulation in the neck. It is standard to measure preoperative neck length using the shorter inner curve of angulated necks. However, the outer curve of these necks can have considerably more length of potential seal, similar to the outer lane of an oval track. In several of our patients, the endowedge was noted to help influence the tilt of the graft and achieve significant extra seal in angulated necks (Fig. 3). This observation goes against the traditional thinking that angulated necks are associated with poorer outcomes15 and certainly will require further investigation. Additionally, the endowedge cannot completely overcome severe angulation as the graft will partially conform back to its cylindrical shape as it settles, but it certainly can add some curve to the graft. Ideally, future iterations of endografts will have curved (or at least beveled) configurations to help maximize seal in these angled necks.
Finally, it is important to recognize that this study represents a retrospective review of a relatively small number of patients. It is prone to the inherent weaknesses of such studies. In addition, longer follow-up is needed to determine the durability of this procedure. Therefore, strong consideration of open repair should be given for any patient with less favorable neck anatomy as this remains the current preferred treatment for patients with low operative risk. However, open juxtarenal aneurysm repair is by no means a benign procedure. Our early results with the endowedge and kilt techniques are favorable, suggesting that they may be a valuable and readily available alternative to open repair, especially in patients with significant comorbidities.
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PII: S0890-5096(06)61464-7
doi:10.1007/s10016-006-9094-z
© 2006 Annals of Vascular Surgery, Inc. Published by Elsevier Inc All rights reserved.
