Complementary Role of Fenestrated/Branched Endografting and the Chimney Technique in the Treatment of Pararenal Aneurysms After Open Abdominal Aortic Repair

Abstract

Purpose: To evaluate the totally endovascular techniques for treating complex pararenal aortic aneurysms after open repair of abdominal aortic aneurysm. Methods: This retrospective study involved 34 men (mean age 74 years) with pararenal aortic aneurysms (22 pseudoaneurysms and 12 para-anastomotic aneurysms) that developed a median 11 years (range 4–22) after the primary surgical reconstruction. The median infrarenal neck length was 2 mm (range 0–9). Total endovascular aneurysm repair (EVAR) included the use of fenestrated (f-EVAR; n=17), branched (b-EVAR; n=11), combined f-EVAR/b-EVAR (n=1), and chimney (ch-EVAR; n=4) grafts and the “sandwich” technique (n=1). The primary outcome was aneurysm shrinkage >5 mm at latest follow-up. Secondary outcomes were target vessel patency, 30-day mortality, late survival, absence of type I and III endoleak, clinical success, and reintervention rate. Results: Technical success was 97% (n=33/34), while clinical success was achieved in 32 (94%) patients. The 30-day mortality was 3% (n=1/34). Mean follow-up was 23.2±16.6 months. One patient was lost to follow-up, and 1 patient underwent late open conversion for endograft infection. Six (18%) of the 33 surviving patients required a reintervention. Primary patency of the target aortic branches was 98% (109/111). Mean aneurysm diameter decreased from 64.1±10.2 to 56.7±16.9 mm (p<0.001) at latest follow-up. Midterm mortality was 12.1% (4/33). Estimated survival rates at 1 and 2 years were 93.9% and 90.9, respectively. Conclusion: Use of f-EVAR, b-EVAR, and ch-EVAR allows effective treatment of postsurgical pararenal aneurysms based on a clear algorithm and patient selection, highlighting the complementary character of these less invasive approaches.

Keywords

aneurysm branched stent-graft chimney technique fenestrated stent-graft pararenal abdominal aorta reintervention sandwich technique target vessel patency

Introduction

Long-term complications of open abdominal aortic repair are very challenging.^1–3 Haimovici⁴ classified postsurgical abdominal aortic aneurysms (AAA) as para-anastomotic aneurysm and pseudoaneurysms. The former was defined as a continuous degeneration of the aortic wall owing to progression of the aneurysm disease, while a pseudoaneurysm was characterized by a break in the arterial wall (usually suture line) with blood extravasation and formation of a fibrous capsule, which tends to enlarge over time. Open repair of these late postsurgical sequelae is associated with high morbidity (70% to 83%) and mortality between 8% and 70%.^5,6 Total endovascular aneurysm repair (EVAR) using fenestrated (f-EVAR), branched (b-EVAR), and chimney (ch-EVAR) grafts has been described in case reports or small series^7–9 as an option to treat pararenal aneurysms after AAA open repair. The aim here is to present our experience with total endovascular repair using these advanced techniques for patients with juxtarenal and suprarenal postsurgical aortic aneurysms.

Methods

Patient Population

A retrospective review was conducted of 34 consecutive patients (mean age 74 years; all men) with postsurgical pararenal aneurysms treated by endovascular means between June 2009 and May 2014. Patients with thoracoabdominal aneurysm requiring thoracic extension of the endograft for progressive aneurysm disease were excluded. Twenty-two (64%) patients were diagnosed with pseudoaneurysms and 12 (36%) patients with para-anastomotic aneurysms. Patient demographics and anatomical data are presented in Table 1. Initial surgical repair of the AAAs was performed electively for 27 (79%) patients and emergently for 7 (21%) due to symptoms or rupture. Fourteen (41%) patients received an aortic tube graft, 15 (44%) an aortobi-iliac graft, and 5 (15%) an aortobifemoral graft. Median interval from the primary surgical reconstruction was 11 years (range 4–22).

Table 1.

Characteristics of Patients and Procedures to Repair Postsurgical Aortic Aneurysms Using Endovascular Techniques Alone.^a

	ch-EVAR/Sandwich (n=5)	f-EVAR (n=17)	b-EVAR^b (n=12)	Total
Age, y	70.2±7.1	70.6±8.2	68.2±8.6	69.7±8.1
Comorbidities
CAD	4	8	6	18
COPD	—	5	1	6
PAD	—	6	5	11
ASA
III	2	12	6	20
IV	3	5	6	14
eGFR, mL/min/1.73 m²	66±46.2	65.2±20.7	79.3±22.6	70.3±26.1
Maximum aneurysm diameter, mm	66.7±12.3	62.1±9.5	66.1±10.8	64.1±10.2
Symptomatic aneurysm	4/5	0	0	4/34
Ruptured aneurysm	2/5	0	0	2/34
Target vessel preservation	8/8	56/58	45/45	109/111
Operation duration, min	140 [125–353]	255 [157–363]	256.5 [202–420]	262.5 [157–420]
Fluoroscopy time, min	37 [27–92]	79 [51–140]	86.5 [49–208]	79 [36–208]
Contrast medium, mL	154.6±26.7	151.3±42.1	191.3±39.1	165.9±42.6
Hospital stay, d	8 [5–12]	8 [5–34]	9.5 [7–19]	8.5 [5–34]

Abbreviations: ASA, American Society of Anesthesiologists; b-EVAR, branched endovascular aneurysm repair; CAD, coronary artery disease; ch-EVAR, chimney endovascular aneurysm repair; COPD, chronic obstructive pulmonary disease; eGFR, estimated glomerular filtration rate; f-EVAR, fenestrated endovascular aneurysm repair; PAD, peripheral artery disease.

Continuous data are presented as the means ± standard deviation or median [range]; categorical data are given as the counts.

Includes one patient treated with 2 fenestrations.

EVAR Techniques

The selection of the therapeutic approach was based on our published algorithm,¹⁰ summarized in Figure 1. Anatomic and morphologic suitability criteria for f-EVAR and b-EVAR were previously reported.¹¹ In case of symptoms, rupture, or anatomical conditions unsuitable for customized devices, the chimney or the sandwich technique was performed. All patients gave written informed consent to the procedures.

Preoperative measurements of the computed tomography angiography (CTA) datasets were performed using Aquarius software (TeraRecon Inc, San Mateo, CA, USA). All procedures were carried out under general anesthesia in a hybrid operating room. The 17 patients undergoing f-EVAR were treated with a custom-made Zenith fenestrated graft (Cook, Bloomington, IN, USA) using a procedure that has been described.^12,13 The 12 patients selected for b-EVAR received a custom-made Zenith branched graft [including for purposes of reporting 1 (3%) patient who had both f-EVAR and b-EVAR]. Both femoral arteries and the left axillary artery were used as access. A 12-F sheath (Cook) was introduced through the axillary artery via an open approach. An 8-F Shuttle sheath (Cook) was introduced into the 12-F sheath. Transfemoral precannulation of the target vessels was done to ensure correct apposition and insertion of the working guidewire. The branched device was deployed 2 cm above the precannulated arteries. Bridging balloon-expandable covered stents were deployed over a 7-F sheath. Aortic endografting was finished with a distal component (tube or bifurcated graft), and the femoral arteries were closed percutaneously.

For the 4 ch-EVAR patients, the chimney grafts were advanced in the renovisceral aortic segment via an open brachial or axillary approach with a 7-F Shuttle sheath (Cook). The target aortic branches were cannulated with a 5-F multipurpose or vertebral catheter (Angiodynamics Inc, Queensbury, NY, USA). An Advanta V12/i-Cast balloon-expandable covered stent (Atrium Maquet Getinge Group, Mijdrecht, the Netherlands) was used for each target vessel to preserve flow and extend the proximal fixation zone for the aortic stent-graft, which was an Endurant device (Medtronic Vascular, Santa Rosa, CA, USA) in all cases.

The sandwich technique or modified chimney was used in 1 patient who had iliac artery anatomy unsuitable for either customized device. A thoracic endograft was advanced and deployed in a healthy segment. Additionally, parallel grafts were advanced to the visceral vessels via an open axillary approach and 2 separate 7-F Shuttle sheaths (Cook). The target vessels were the superior mesenteric artery (SMA) and celiac artery (CA); the patient was under dialysis so there was no need to revascularize the renal arteries. An Advanta V12/i-Cast balloon-expandable covered stent was deployed for each visceral vessel, and the distal aortic endograft was deployed.

Surveillance Protocol

CTA, abdominal duplex ultrasound, and plain radiography of the device in 2 projections were performed prior to hospital discharge, at 1 year, and yearly after. At the 3- and 6-month visits, physical examination and abdominal duplex ultrasound were performed.

Definitions and Outcome Measures

The definitions suggested by Haimovici⁴ were used to classify postsurgical aneurysms as para-anastomotic aneurysm or pseudoaneurysms, and the term “pararenal aneurysms” included juxtarenal and suprarenal cases. The maximal aneurysm diameter was measured for the pseudoaneurysms in the infrarenal or juxtarenal segment and in the juxtarenal or suprarenal segment for the para-anastomotic aneurysms.

Technical success was defined as a completed endovascular procedure with patent targeted vessels and no type I or III endoleak in the first 24 hours postoperatively. Clinical success was defined as the completion of the endovascular procedure without death, type I or III endoleak, graft infection or thrombosis, aneurysm expansion >5 mm, aneurysm rupture, or conversion to open repair. Renal deterioration was defined as a postoperative (48–72 hours) decrease of at least 25% of the estimated glomerular filtration rate (eGFR) compared with the preoperative values following the RIFLE criteria.

The primary outcome was aneurysm shrinkage >5 mm based on the last CT or magnetic resonance imaging. Secondary endpoints and outcomes were target vessel patency, 30-day mortality, survival, absence of type I or III endoleak, reintervention, and assisted primary clinical success achieved with secondary endovascular treatment of type I/III endoleak. Secondary procedures included all reinterventions performed due to technical reasons related to the graft or to the ancillary components, such as endoleak, migration, limb graft stenosis/thrombosis, bridging stent fracture, dislocation, or in-stent stenosis/occlusion.

Statistical Analysis

Categorical variables are presented as counts and percentages. Continuous variables are presented as mean ± standard deviation if the data are normally distributed or median (range) if the data are skewed. The Kaplan-Meier method was used to estimate clinical success, freedom from all-cause mortality, and target vessel patency. Statistical significance was set at p<0.05. Survival, target vessel patency, and freedom for reintervention were analyzed using Kaplan-Meier curves. Data were collected and analyzed using IBM SPSS Statistics (IBM Corporation, Somers, NY, USA).

Results

The design of the endograft for the f-EVAR/b-EVAR cases was a monotube for 10 (30%) patients, a composite tube for 12 (35%), and a composite bifurcation for 12 (35%). The total number of vessels targeted in the study was 111, excluding scallops. One fenestration could not be cannulated; the remaining 110 vessels had covered stents placed (107 balloon-expandable). Three self-expanding stents were placed in renal arteries with a very pronounced angulation in the b-EVAR technique. An additional 57 stents were used to reline the deployed bridging devices. The use of these stents depended mainly on the transition between the distal part of the covered stent and the native vessel. The endograft and covered stent-graft configurations used are listed in Table 2.

Table 2.

Stent-Graft Specifications for Target Vessels.

Patients (%)	LRA	RRA	SMA	CA
8 (23)	Fenestration	Fenestration	Fenestration	Fenestration
8 (23)	Branch	Branch	Branch	Branch
7 (21)	Fenestration	Fenestration	Fenestration	Scallop
2 (6)	Covered	Covered	0	0
2 (6)	Covered	0	0	0
1 (3)	Occluded	Branch	Branch	Branch
1 (3)	Nephrectomy	Branch	Branch	Branch
1 (3)	Branch	Nephrectomy	Branch	Branch
1 (3)	Fenestration	Fenestration	Fenestration	0
1 (3)	Fenestration	Fenestration	Branch	Branch
1 (3)	Fenestration	Fenestration	Scallop	0
1 (3)	Occluded	Occluded	Covered	Covered

Abbreviations: CA, celiac artery; LRA, left renal artery; RRA, right renal artery; SMA, superior mesenteric artery.

Technical success was 97%. Cannulation of the left renal artery was impossible in 1 patient treated by f-EVAR as noted above. The main graft and the aortic wall were in close contact at that point, probably due to angulation of the aorta at this segment, and occlusion and thrombosis of the renal artery was expected. No evidence of endoleak was observed in the final angiogram. The patient required temporary hemofiltration for 6 days due to renal deterioration but was discharged without any persistent decline in renal function. This patient was admitted 45 days after his discharge and died in the third month postoperatively due to nonocclusive bowel ischemia in the context of heart failure and low cardiac output. None of the patients had persistent paraplegia or paraparesis. Four (11%) patients suffered from minor transient lower limb weakness that resolved days after the procedure; 2 of these patients were treated with f-EVAR and 2 with b-EVAR.

There were 3 cases of severe renal deterioration; the first was in the f-EVAR case noted above caused by unsuccessful revascularization of the renal artery. The second case was due to spontaneous renal bleeding on postoperative day 15, which was treated by urgent coil embolization of the renal artery of the single left kidney (after previous right nephrectomy for renal cell carcinoma several years before). Renal function deterioration in the third patient was related to coverage of 2 accessory renal arteries. The remaining patients had a postoperative mean eGFR that remained stable (69.3±30.1 mL/min/1.73 m²). Except for the dialysis patient treated using the sandwich technique, no other patient required permanent hemodialysis after discharge from the hospital.

Clinical success at 30 days was achieved in 32/34 patients (Figure 2A). One patient was lost on follow-up, and another patient experienced sudden death at home on the 10th postoperative day (3% 30-day mortality). His CT scan at discharge showed sufficient exclusion of the aneurysm, no evidence of any type of endoleak, and all vessels were patent.

Mean follow-up was 23.1±16.5 months. Cumulative mortality was 12.1% (4/33); none of the 3 late deaths was procedure related (Figure 2B). In follow-up, 1 patient died 3 months after the procedure due to nonocclusive bowel ischemia as noted above; the other deaths were due to significant coronary disease. Estimated survival rates at 1 and 2 years were 93.9% and 90.9, respectively. Overall target vessel patency was 98.2% (Figure 2C).

Mean maximal aneurysm diameter decreased from 64.1±10.2 to 56.8±17.2 mm (p<0.001). Twenty-five (76%) patients met the primary outcome measure and 7 (21%) patients had a stable aneurysm sac. One patient with recurrent type III endoleaks showed aneurysm sac growth before the last reintervention (detailed below); the most recent duplex after the last treatment showed sac regression. Figure 3 displays individual aneurysm sac evolution for the 33 patients, excluding the patient who died perioperatively but the patient lost to follow-up was included because a noncontrast CT recorded 3 months after the procedure at another center for another clinical condition became available for this portion of the analysis. Five (14%) patients diagnosed with type II endoleaks had stable aneurysm sacs and were treated conservatively. Absence of type I or III endoleak was achieved in 88% (n=29/33) patients. No graft migration or limb occlusions were observed during follow-up.

Six (18.2%) patients needed 8 reinterventions during the observation period. One b-EVAR patient required 3 reinterventions. The first was due to a right renal type III endoleak, which was treated with a covered stent. The second reintervention was a combined CA and SMA type III endoleak, both successfully treated with covered stents. This patient’s last endoleak was caused by left renal artery stent misplacement and coexisting stenosis; it was treated with deployment of an additional bare metal stent. Times of these reinterventions were 12, 25, and 53 months, respectively.

One patient treated with a ch-EVAR underwent endograft explantation 1 year postoperatively for type Ib endoleak and endograft infection likely caused by a mycotic pseudoaneurysm. The patient underwent placement of a rifampicin-infused aortobifemoral bypass with antegrade bypass to the renovisceral vessels. The further course was uneventful.

Two patients were treated with covered stents due to type III endoleaks in bridging stents at 8 and 45 months, respectively. The remaining 2 interventions were the previously mentioned coil embolization of a renal artery due to kidney bleeding and SMA stenting due to in-stent high-grade stenosis.

Discussion

The current series reports the performance of all available endovascular techniques for patients with postsurgical pararenal aneurysms, including patients who were treated in elective and urgent settings. Based on our internal algorithm, f-EVAR and/or b-EVAR is the preferable approach for elective, anatomically feasible cases, while ch-EVAR is our first choice in symptomatic or ruptured patients or those anatomically unsuitable for f-EVAR/b-EVAR.^14–17

Standard EVAR has already demonstrated effectiveness in the treatment of infrarenal AAAs; however, in postsurgical pararenal aneurysms and pseudoaneurysms, the requisite infrarenal neck is not present. Consequently, advanced endovascular techniques, such as f-EVAR/b-EVAR and ch-EVAR, are necessary.¹⁸ The literature lacks a robust evaluation of the performance of these techniques in this specific pathology. Most of the published series report their experience treating infrarenal para-anastomotic aneurysms and pseudoaneurysms with standard EVAR treatment. Some of these series reported reintervention and conversion rates of 26.9% and 6.9%, respectively, at a median follow-up of 41 months.^19,20 These poor outcomes reported in the use of standard EVAR are mostly due to endograft migration related to poor quality of the aortic wall and the increased risk of neck enlargement. Today, newer tools, such as giant stents and endoanchors, are available to improve proximal neck sealing.

Oikonomou et al⁹ reported 35 patients who underwent f-EVAR for juxtarenal aneurysms after open AAA repair. The authors included only elective cases, demonstrating safety of the procedure with low morbidity and mortality. With the exception of the Oikonomou article, published data for endovascular treatment of juxtarenal and suprarenal aneurysms after open aortic repair are mostly case reports, reflecting the substantial need for additional evidence in the literature.^21–23

Earlier historical reports on para-anastomotic aneurysms and pseudoaneurysms showed an incidence between 0.5% and 15%.^24,25 However, this incidence might be underestimated as not all the patients who undergo open repair receive radiologic imaging in follow-up, which is important due to the late appearance of postsurgical aneurysms. Patients with untreated para-anastomotic aneurysms show a higher risk for rupture between 15% and 61%.^5,26,27 Additionally, the treatment is technically challenging due to the involvement of renovisceral vessels, the advanced age of the patients, and the possible progress of coexisting severe comorbidities.^28,29

Complex endovascular treatment for primary pararenal and thoracoabdominal aneurysms is well described in large series from many experienced centers. However, technical issues in the treatment of this specific disease should be mentioned. Some difficulties in planning and performing the procedure need to be considered, which makes this a different scenario from primary f/b-EVAR. Limitations in maneuverability and catheterization of target vessels may be encountered, especially in f-EVAR, as a previous aortic tube may have a small lumen and provide little space for the endograft, producing unwanted frictional forces.

Complications of these complex endovascular procedures need to be discussed. Spinal cord ischemia and renal deterioration must be avoided to achieve clinical success. Some recent reports show low rates of paraplegia and paraparesis. Spinal cord ischemia reached 10.4% in one series, while persistent paraplegia was 1.5% for thoracoabdominal aneurysm repair.³⁰ Contrariwise, the present series had no evidence of persistent spinal cord ischemia, probably due to the rare need to cover the infradiaphragmatic aorta.³¹ Main reasons for reinterventions were type I and III endoleaks, highlighting the importance of meticulous follow-up.

Conclusion

Total endovascular repair of postsurgical pararenal aneurysms is feasible and safe, with low morbidity and mortality and few reinterventions in the midterm. In elective cases with anatomic suitability, f-EVAR or b-EVAR was our first approach. On the other hand, in emergent cases or those with hostile iliac or neck anatomy, ch-EVAR was a valid and preferable option. The suggested algorithm for treatment of postsurgical pararenal aneurysms highlights that the 3 available total endovascular techniques are complementary and not competitive. Long-term results and larger patient cohorts are necessary to provide durability of total endovascular repair.

Footnotes

Declaration of Conflicting Interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

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

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