Balloon expandable stents facilitate right renal artery reconstruction during complex open aortic aneurysm repair
Article Outline
Objective
Patients undergoing repair of thoracoabdominal (TAA) or visceral aortic segment aneurysms typically require reconstruction of the renal arteries. The use of balloon expandable stents (BES) has been proposed as an alternative to endarterectomy or bypass for renal artery reconstruction (RAR) during open aortic aneurysm repair. We report technical aspects and long-term patency data for this method of right RAR during complex open aortic aneurysm repair.
Methods
During the interval July 1, 2005 to December 31, 2007, a total of 67 patients underwent right RAR using a BES during concomitant TAA (type I: n = 2 [2.9%], type II: n = 8 [11.9%], type III: n = 13 [19.4%], and type IV: n = 22 [32.8%]), juxtarenal (n = 9 [13.4%]) or suprarenal (n = 13 [19.4%]) AAA repair. Indications for RAR were orificial stenosis (n = 21 [31%]) and/or technical considerations referable to the proximal aortic suture line. Patency of the renal stent was evaluated in patients with computed tomography angiography using three-dimensional reconstruction or with abdominal duplex evaluation at follow-up.
Results
The mean patient age was 75.1 years, 54.4% were male, and 18% of operations were in nonelective circumstances. Twenty-seven (39%) out of 67 patients had a preoperative creatinine level ≥1.4 mg/dL. Two patients (2.9%) developed permanent renal failure postoperatively (neither related to renal artery occlusion). Mean radiologic follow-up was 405 days (11-1281) with 98% stent patency noted. One patient had an early stent occlusion noted at 1 month. An additional patient was noted to have a nonflow-limiting dissection distal to the renal stent, and another was noted to have distal migration of the stent beyond the renal ostium; however, these findings were clinically silent.
Conclusions
The use of BES during complex open aortic aneurysm repair affords a rapid and durable mode of RAR, obviating the need for endarterectomy and its associated technical complications.
Patients undergoing repair of complex aortic aneurysms, thoracoabdominal aneurysms (TAA) in particular, often have associated renal and/or visceral artery occlusive disease. The incidence of such orificial occlusive disease in this patient population has been reported to range between 15% and 45%.1, 2 Reconstruction of the visceral vessels, especially renal arteries, is either mandated by their topographic relation to the aneurysm or indicated to correct orificial stenosis, which, in turn, is important to preserve perioperative renal function.3, 4 The majority of complex aortic aneurysms are repaired via a left flank or thoracoabdominal incision, as this method offers superior exposure to the visceral and/or thoracoabdominal segments.5, 6 Management of renal artery reconstruction (RAR) during thoracoabdominal (TAA) repair is variable; for most patients, inclusion techniques are used for the right RAR and either bypass or reimplantation for the left.6, 7 Technical pitfalls leading to potential renal artery occlusion and prevention thereof have been reviewed previously.6 Options for revascularization of significant right renal artery stenosis from a left flank exposure are generally limited to orificial endarterectomy,8 especially when a sizable aneurysm involves the pararenal aorta. An important limitation of endarterectomy in this setting is the surgeons' inability to directly repair and/or interrogate the reconstructed right renal artery, as circumferential external control/exposure of the right renal artery is unavailable. Prior studies advocating direct duplex interrogation of operative RAR have indicated defects requiring immediate revision in up to 23% of cases.9, 10 While right renal artery bypass via a left flank incision has been reported,11 this is technically challenging, increases renal ischemic time, and is only feasible when the pararenal aortic aneurysm neck can be circumferentially divided and mobilized.
The widespread use of percutaneous stents has provided another means of renal artery revascularization. However, when the aneurysm surgery itself involves the pararenal aorta, antecedent placement of renal stents is ill-advised. Recently, LeMaire et al described orificial balloon-expandable stenting for intraoperative management of both renal and mesenteric occlusive lesions,12 but limited follow-up information was available. In the present study, we report our experience using balloon expandable stents to facilitate right RAR during concomitant complex open aneurysm repair.
Methods
This retrospective study was approved by the Massachusetts General Hospital Institutional Review Board. A total of 67 patients with complex aortic aneurysm disease underwent open surgical repair of the aneurysm with concomitant right renal artery stenting between July 2005 and December 2007.
Operative strategies for TAA repair have been previously summarized.6 Specifically, with reference to the renal arteries, cold (4°C) renal preservation solution was routinely instilled into the renal arteries to increase ischemic tolerance, as all patients had suprarenal or supravisceral cross-clamp application. Inclusion techniques at or into the right renal orifice and bypass (6-mm polytetrafluoroethylene [PTFE]) of the left renal artery were used in most cases.
Description of technique
The decision to stent the right renal artery was made intraoperatively by examination of the right renal artery orifice for severe stenosis or technical considerations such as suture line impingement. Cold renal preservation solution was instilled into the right and left renal arteries unless a severe stenosis was encountered. If the right renal artery orifice was stenotic, it was gently dilated with a fine Schnidt clamp (Fig 1) prior to the instillation of cold renal preservation solution. The posterior/inferior layer of the visceral aortic anastomosis courses at or within the right renal orifice to ensure adequate bites of healthy aorta and maximal exclusion of aneurysmal aorta (Fig 2). After the posterior aspect of the anastomosis courses around the right renal artery, open right renal orificial stenting is accomplished by direct placement of an appropriate-sized balloon expandable stent within the right renal artery (Fig 3). Neither guidewire nor fluoroscopic imaging was utilized. The stent is placed such that a small portion would override into the aorta. Insufflation to burst pressure under direct vision then expanded the stent within the renal artery ostium. No effort was made to “size” the stent based on preoperative computed tomography angiography (CTA). In general, 6-mm Palmaz Blue balloon expandable stents (Cordis Corp, Miami Lakes, Fla) were utilized and the aortic end of the stent was postdilated with larger balloons until a snug fit was achieved at the aortic ostium. After the stent is successfully placed, the anterior aspect of the inclusion anastomosis is completed (Fig 4).
Fig 1.
Schematic representation of opened visceral aortic segment (patient head to right) during thoracoabdominal (TAA) repair. Origins of (from right to left) celiac, superior mesenteric, right, and left renal arteries are displayed. Dashed lines indicate the right renal artery wherein circumferential external exposure is not possible. Inset: hemostat gently dilates right renal artery orificial stenosis.
Fig 2.
Inclusion button reconstruction of celiac, superior mesenteric, and right renal artery ostia. The left renal artery origin is detached from the aorta, and cold renal preservation solution is instilled. Note the attached side-arm graft for the subsequent left renal artery reconstruction. The visceral inclusion button anastomosis is begun just cephalad to the celiac axis origin and coursing close to the visceral and right renal origins. Note the suture bites into the right renal artery; a perfusion catheter (not shown) is typically placed within the right renal artery orifice to allow the instillation of cold renal preservation solution and to interrogate the course of the right renal artery as it courses around the aneurysm.
Fig 3.
Following completion of the posterior/inferior aspect suture line, a balloon expandable stent is inserted into the right renal artery with a small portion overriding into the aorta. The stent is then rapidly expanded under direct vision. Note that no guidewire or fluoroscopic imaging is utilized.
Fig 4.
The anterior aspect of the visceral button anastomosis is now completed, with no further bites near or into the stented right renal artery. Inset: the balloon-expandable stent is seen within the right renal artery in a coronal plane. Note how the stent overrides into the aorta and protects it from suture line impingement or plaque shift. The left renal bypass using a sidearm polytetrafluoroethylene (PTFE) graft is now performed after completion of the visceral inclusion button anastomosis.
CTA with three-dimensional (3D) reconstruction was the predominant imaging study; typically, it was obtained at the 6- to 12-month interval, and this varied among individual surgeons. Ultrasound was also used in a minority of patients (n = 5). Society for Vascular Surgery risk score13 was used to assess preoperative risk factors. Pre- and postoperative creatinines were recorded. Patient survival was confirmed using the Social Security Death Index, review of computerized hospital records or telephone follow-up.
Follow-up CT scans were reviewed to assess stent patency, renal artery dissection, and/or stent migration.
Results
Demographics and clinical features of the study group are displayed in Table I. During the study interval, a total of 158 thoracoabdominal, juxtarenal, or suprarenal aneurysms were performed, and 67 (42%) underwent simultaneous open right renal artery stenting. Perioperative outcomes are displayed in Table II, and although lower than our previously reported data, likely reflect the fact that one third of the patients had complex abdominal aneurysms.14, 15 There were three in-hospital deaths secondary to pneumonia, sepsis from a perforated viscus, and colonic ischemia due to a failed superior mesenteric artery (SMA) reconstruction. One-year actuarial survival was 85% (57/67) (Fig 5). A total of three patients required dialysis (two permanent), however, none of these patients had failure of their RAR. Of the two patients who required permanent dialysis, one case was due to hypotension secondary to postoperative bleeding, and the other, who had severe pre-existing renal insufficiency, developed renal failure but had a postoperative angiogram demonstrating patent renal arteries. The third patient had chronic renal insufficiency preoperatively, and required transient dialysis due to acute tubular necrosis.
Table I. Demographics and clinical features of 67 patients with complex aortic aneurysm repair
| Age (y) | 75.1 ±7.2 |
| Gender (male) | 37(55.2%) |
| Number of hypertensive medications | |
| 0 | 4(5.9%) |
| 1 | 19(28.3%) |
| 2 | 33(49.2%) |
| 3+ | 12(17.9%) |
| Diabetes mellitus | 8(11.9%) |
| Severe COPD (oxygen dependent) | 2(2.9%) |
| Smoking history | |
| Never | 28(40.2%) |
| Former | 33(49.2%) |
| Current | 7(10.4%) |
| SVS risk score (mean) | 6.18±2.14 |
| Preoperative aneurysm sac size (cm) | 6.32±1.14 |
| Aneurysm extent | |
| Type I TAA | 2(2.9%) |
| Type II TAA | 8(11.9%) |
| Type III TAA | 13(19.4%) |
| Type IV | 22(32.8%) |
| Juxtarenal AAA | 9(13.4%) |
| Suprarenal AAA | 13(19.4%) |
| Clinical presentation | |
| Elective | 55(82.0%) |
| Rupture | 2(2.9%) |
| Urgent nonruptured | 10(14.9%) |
Table II. Perioperative outcomes
| Perioperative mortality (30 d) | 3(4.4%) |
|---|---|
| Neurologic | |
| Temporary paraparesis | 2(2.9%) |
| Permanent paraplegia | 2(2.9%) |
| Cardiac | |
| Myocardial infarction | 4(5.9%) |
| Arrhythmia | 4(5.9%) |
| Pulmonary | |
| Pneumonia | 8(11.9%) |
| Prolonged intubation (>48 h) | 6(8.9%) |
| Reintubation | 2(2.9%) |
| Permanent renal failure (on dialysis) | 2(2.9%) |
Fig 5.
Cummlative survival. Patients post-right renal artery stenting during open complex aortic aneurysm repair.
Months 0 1 12 24 36 At risk 67 60 41 16 4 Cum events 3 4 9 10 11 Cum survival 0.95 0.94 0.85 0.80 0.74 St error 0.03 0.03 0.05 0.06 0.08
The indication for renal artery stenting was severe ostial stenosis in 31% (n = 21), technical reasons such as encroachment of the renal orifice during the aortic anastomosis in 58% (n = 39), and both stenosis and technical in 7% (n = 5) of the cases. Left renal bypass was also undertaken in 81% (54/67) of the patients undergoing right renal stenting. Two of these bypasses were noted to be thrombosed (96% patency) during follow-up imaging. A total of 51 (76%) patients had radiologic follow-up with 16 patients having no radiologic follow-up. Of these 16 patients without radiologic imaging, nine (13%) were patients who died within 6 months after surgery with seven (10%) patients lost to follow-up. The median follow-up in patients with radiologic imaging was 405 days (11-1281). Three known stent-related complications occurred with one stent occlusion and one reintervention for stent migration (Fig 6). One patient had a dissection distal to the stent (Fig 7), and another patient with significant tortuosity of the renal artery had distal migration of the stent (Fig 8). There was only one stent occlusion noted, which was discovered by a CTA performed 1 month after surgery. Interestingly, this patient had patent left and right renal arteries via a duplex obtained 2 days after surgery due to acute renal failure. All three of these stent-related complications were clinically silent and discovered during follow-up imaging.
Fig 6.
Reintervention or stent occlusion.
Months 0 1 12 24 36 At risk 67 44 30 10 1 Cum events 0 1 1 1 2 Freedom from occlusion/reintervention 1 0.98 0.98 0.98 0.86 St error 0 0.02 0.02 0.02 0.12
Fig 7.
Figure depicts a cross-sectional computed tomography (CT) image with a balloon expandable renal stent within the right renal artery, slightly overriding into the aorta. A dissection flap is noted immediately distal to the stent, however, contrast is noted to fill the right kidney without any appreciable delay when compared to the left kidney. Note the orificial plaque at the right renal artery origin.
Fig 8.
A, Depicts a preoperative cross-sectional computed tomography (CT) image demonstrating an aortic aneurysm in proximity to a tortuous right renal artery. Note the small area of calcification along the inferior aspect of the right renal artery origin. B, demonstrates a similar cross-sectional image upon postoperative CT imaging. Note the stent migration into the renal artery without appropriate overriding into the aorta with kinking of the renal artery proximal to the stent near the orificial calcification.
Discussion
Although it has been argued that “physiologically silent” renal artery stenosis in association with the need for infrarenal abdominal aortic aneurysm (AAA) repair can safely be ignored,16 complex aneurysm surgery which necessitates suprarenal (or more proximal) cross-clamping is a decidedly different clinical scenario. Herein, cross-clamp application and/or aortic suture lines can precipitate plaque shift and renal artery occlusion, increasing the risk of perioperative renal failure with the obligatory renal ischemia17, 18 associated with suprarenal clamping. In turn, there is consensus that perioperative renal failure increases the short- and long-term mortality risk in TAA repair.6, 14, 15, 19, 20, 21 Accordingly, an aggressive posture toward correction of the frequently encountered renal artery stenosis in complex aneurysm surgery is appropriate. Regardless of ostial renal artery stenosis, other technical considerations can result in renal artery occlusions in complex and/or TAA repair.6, 19 Prior follow-up studies have indicated that surgical RAR produces durable results after TAA repair,1 yet technical factors require strict attention to detail.6 Orificial endarterectomy has been the standard method for managing right renal artery stenosis during complex aneurysm repair;8 yet technical limitations are imposed by the fact that circumferential external control thereof is generally not possible.
Renal artery stenting has been reported in patients with TAAs: Sullivan et al published a case report describing preoperative percutaneous renal artery stenting in a patient with uncontrolled renovascular hypertension, congestive heart failure, and a TAA.22 Six weeks later, the patient successfully underwent open aneurysm repair, although multiple reinterventions for in-stent stenoses were required. The use of percutaneous renal stenting after open thoracoabdominal repair has also been published.23 In this case report, suspected plaque shift in the setting of a solitary kidney resulted in renal artery obstruction and acute renal failure, successfully treated with percutaneous stenting of the renal artery. We have not used preoperative renal stenting in the setting of complex aneurysm disease; the threat of atheroembolism with diffuse aneurysm disease has led to this posture.1
Renal and/or mesenteric stenting during complex open aneurysm repair was first reported by LeMaire et al in 2004.12 The rationale for stenting in lieu of bypass or endarterectomy was reduction of organ ischemia and reduced vessel fragility and thinning. Ninety-three patients underwent successful stenting of either the renal or mesenteric vessels during open TAA repair. Only 9% of the patients had postprocedure imaging with the majority of these patients undergoing imaging at 4 to 42 days postoperatively. Only one patient had long-term imaging at 19 months, and this revealed stent occlusion. While the ability to place a stent in lieu of an endarterectomy or bypass may be technically feasible, the present series contains the first available information in this setting on the long-term patency of stenting. Of note, in contrast to LeMaire at al, the present study's focus was stenting of the right renal artery only because of the specific anatomic nuances thereof with regard to complex aneurysm surgery approached from the left flank. Celiac/SMA lesions were generally treated with endarterectomy and interrogated thereafter with Doppler, as these ostial lesions tend to be bulky and calcific; we have previously reported on the relatively high recurrence rate for stenting of visceral vessels.24
Open stenting of the right renal artery is a technique of expediency that is clearly faster than orificial endarterectomy. The current study examined renal artery patency poststenting via CTA with high-resolution 3D reconstruction as the imaging modality of choice. Although this modality is not the most sensitive for evaluating restenosis, it does allow the determination of patency and has been our imaging modality of choice in follow-up after complex aneurysm surgery. The authors have previously used CT in reporting late graft-related events after TAA repair, and excellent long-term patency of renal/visceral reconstructions were noted.1 The favorable (98%) “gross” patency in open renal stenting described herein, when compared with the 15% to 30% restenosis rate after percutaneous renal stenting may be explained by the limitations of the imaging modality as described above but also potentially by more accurate placement across a stenosis due to direct open visualization via the opened aneurysm. Also, the majority (n = 39; 58%) of our stents were placed for technical reasons (such as suture line impingement) that did not include severe orificial stenosis. One would expect a lower rate of restenosis in this patient cohort.
Although intermediate results utilizing renal artery stenting in complex aortic surgery seem promising, there were complications associated with stenting. There was one early stent occlusion. A duplex obtained 2 days after surgery demonstrated a patent right renal artery, however, a CTA performed 1 month after surgery clearly demonstrated an occluded right renal artery just distal to the stent. No definite cause for occlusion was noted; however, there was antecedent significant atrophy of the kidney by this stenotic renal artery. Regardless, this patient suffered no long-term renal deficits and had a creatinine of 1.3 mg/dL noted at the most recent follow-up. After observing a single stent migration in this study, we now routinely “flare” the aortic ostium of the stent with an oversized balloon. In addition, assessment of the length of a right renal lesion as assessed on perioperative CTA is important. Deploying stents in circumstances in which the distal renal artery is not anatomically normal (ie, the entire lesion cannot be stent covered) would appear to be ill advised. The overall rate of postoperative renal failure requiring hemodialysis in this cohort is in the range of a previously reported publication19 (2.9% and 2.7%, respectively).
The ease of deploying a stent in the right renal artery as opposed to bypass or endarterectomy indicates to us that widespread adoption of this technique in complex aortic surgery is appropriate. The placement of a balloon expandable stent ensures that the suture line will not impinge the right renal artery orifice and/or corrects orificial stenosis more expeditiously when compared to endarterectomy.
The study's limitations include its retrospective nature and lack of complete follow-up imaging information; furthermore, subtle degrees of in-stent restenosis could be missed by our principle follow-up study, CTA imaging.
Author contributions
References
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Competition of interest: none.
The editors and reviewers of this article have no relevant financial relationships to disclose per the JVS policy that requires reviewers to decline review of any manuscript for which they may have a competition of interest.
PII: S0741-5214(09)01658-9
doi:10.1016/j.jvs.2009.04.079
© 2010 Society for Vascular Surgery. Published by Elsevier Inc. All rights reserved.
