The use of thoracic stent grafts for endovascular repair of abdominal aortic aneurysms

Abstract

Objectives

Stent grafts for endovascular repair of infrarenal aneurysms are commercially available for aortic necks up to 32 mm in diameter. The aim of this study was to evaluate the feasibility of endovascular repair with large thoracic stent grafts in the infrarenal position to obtain adequate proximal seal in wider necks.

Methods

All patients who underwent endovascular aneurysm repair using thoracic stent grafts with diameters greater than 36 mm between 2012 and 2016 were included. Follow-up consisted of CT angiography after six weeks and annual duplex thereafter.

Results

Eleven patients with wide infrarenal aortic necks received endovascular repair with thoracic stent grafts. The median diameter of the aneurysms was 60 mm (range 52–78 mm) and the median aortic neck diameter was 37 mm (range 28–43 mm). Thoracic stent grafts were oversized by a median of 14% (range 2–43%). On completion angiography, one type I and two type II endoleaks were observed but did not require reintervention. One patient experienced graft migration with aneurysm sac expansion and needed conversion to open repair. Median follow-up time was 14 months (range 2–53 months), during which three patients died, including one aneurysm-related death.

Conclusions

Endovascular repair using thoracic stent grafts for patients with wide aortic necks is feasible. In these patients, the technique may be a reasonable alternative to complex endovascular repair with fenestrated, branched, or chimney grafts. However, more experience and longer follow-up are required to determine its position within the endovascular armamentarium.

Keywords

Endovascular aneurysm repair abdominal aortic aneurysm wide infrarenal neck thoracic endograft funnel technique

Introduction

Endovascular repair of infrarenal aortic aneurysms causes less perioperative morbidity and mortality than open repair.^1–3 Suitable aortic neck anatomy is one of the most important conditions for successful outcomes after endovascular aneurysm repair. In particular, patients with a wide infrarenal aortic neck are at risk of inadequate proximal sealing, resulting in endoleaks and reinterventions.⁴ Commercially available stent grafts have a maximal diameter of 36 mm to be used for aneurysms with proximal aortic necks up to 32 mm. Patients with wider necks must either undergo open repair or have complex endovascular procedures with branched, fenestrated, or chimney stent grafts in the visceral arteries to extend the sealing zone. As an alternative, we used commercially available thoracic stent grafts with a maximal diameter of 46 mm in the infrarenal position in order to treat these patients with a relatively simple endovascular procedure. The aim of this study was to describe the outcomes of this new treatment for aortic aneurysms with a wide infrarenal neck.

Methods

Study design

This retrospective observational study included all patients who underwent endovascular repair of an infrarenal aortic aneurysm at our center using a thoracic stent graft with a diameter greater than 36 mm between January 2012 and December 2016. Patients were followed with computed tomography angiography (CTA) at six weeks after surgery and with annual duplex examinations thereafter. The study protocol was approved by the institutional review board.

Surgical procedure

Preoperative CTA was used for procedural planning. We used two variants of the funnel technique with either an aorto-uniiliac or a bifurcated stent graft. In the first variant, after obtaining bilateral vascular access through common femoral artery cutdown, an Endurant aorto-uniiliac stent graft with a diameter of 36 mm (Medtronic, Fridley, MI) was deployed 70 mm below the renal arteries using a calibrated pigtail catheter. The aorto-uniiliac stent graft was then extended to the iliac bifurcation if necessary to stabilize the stent graft and to prevent its migration during deployment of the proximal thoracic stent graft. Subsequently, a Valiant Captivia proximal FreeFlo straight thoracic stent graft with a length of 100 mm and a diameter of 38–46 mm (Medtronic) was deployed just below the renal arteries, with 30 mm overlap into the aorto-uniiliac stent graft. A Talent Occluder (Medtronic) was placed in the contralateral common iliac artery and all stent grafts were dilated with a Reliant balloon (Medtronic). A completion angiography was made and the procedure was finalized with a femorofemoral crossover bypass. Alternatively, a bifurcated stent graft with a diameter of 36 mm was positioned 50 mm below the renal arteries and the thoracic stent was deployed with 50 mm overlap into the bifurcated graft after contralateral gate cannulation and stent graft extension to the iliac bifurcations in order to stabilize the bifurcated graft. Of note, the distance from the renal arteries to the aortic bifurcation should be at least 100 mm when using aorto-uniiliac stent grafts and at least 130 mm when using bifurcated stent grafts. The distance from the renal arteries to the iliac bifurcation should be at least 172 mm when using aorto-uniiliac stent grafts and at least 185 mm when using bifurcated stent grafts.

Outcome definitions

Demographics, clinical characteristics, aneurysm morphology, and postoperative outcomes were retrospectively extracted from patients’ charts. Patients with a history of angina, any previous myocardial infarct, prior percutaneous coronary intervention, or prior coronary artery bypass surgery were considered to have ischemic heart disease. Cerebrovascular disease was defined as a history of a transient ischemic attack or stroke. Chronic kidney disease refers to a glomerular filtration rate (GFR) of less than 60 ml/min. GFR was estimated using the MDRD formula.⁵ Aneurysm morphology was measured after center-lumen line reconstructions using 3Mensio (3Mensio Medical Imaging, Bilthoven, the Netherlands). Aortic neck diameter was measured at 5 mm intervals over a length of 20 mm (or until the start of the aneurysm in necks shorter than 20 mm) starting immediately below the renal arteries; the average neck diameter is reported. The aortic neck was considered conical when there was an increase in diameter greater than 5 mm within the neck. Perioperative complications refer to a time frame of 30 days from surgery. Acute kidney injury was defined according to KDIGO guidelines.⁶ Endoleak was defined as persistent blood flow into the aneurysm sac after the endovascular procedure.⁷ Endograft migration refers to a displacement of the endograft of at least 10 mm.⁷ Sac expansion was defined as an increase of the aneurysm sac diameter of 5 mm or more.⁷ Aneurysm-related mortality refers to any death that occurred within 30 days of primary repair or reintervention, or any death related to the aneurysm or stent graft at any time following treatment.

Statistics

Continuous variables are presented as median and range and categorical variables are presented as percentages.

Results

Patient characteristics

Eleven patients with wide infrarenal necks underwent aortic aneurysm repair using thoracic stent grafts. Patient characteristics are reported in Table 1. Median age at intervention was 75 (62–81) years. Endovascular repair was chosen over open repair because patients were considered unfit for open repair (n = 4), because of extensive prior abdominal surgery (n = 1), or because of simultaneous endovascular repair of a thoracic aortic aneurysm (n = 3). One patient underwent urgent surgery for a contained rupture; we chose for endovascular repair in this patient because of limited life expectancy due to metastasized lung carcinoma. In two cases there was no particular contraindication for open aneurysm repair. During the study period, 149 infrarenal aortic aneurysms were treated using open repair, whereas 250 patients received standard endovascular aneurysm repair at our institution.

Table 1.

Demographics and clinical characteristics.

	Gender	Age	Comorbidities	Maximal diameter of aneurysm (mm)	Reason for EVAR	Urgency of surgery
1	M	76	CVD, hypertension	76	None	Elective
2	M	79	CKD, hypertension	78	Combination with TEVAR	Elective
3	M	81	CVD, IHD, CKD	60	Unfit for open repair	Elective
4	M	75	IHD, CKD, hypertension	71	Unfit for open repair	Elective
5	M	62	Hypertension	52	Limited life expectancy due to NSCLC stage 4	Emergenta
6	M	68	COPD, hypertension	57	Combination with TEVAR	Elective
7	M	80	DM, hypertension	68	Previous abdominal surgery with urostomy	Elective
8	F	68	CVD, IHD, CKD, hypertension	58	Combination with TEVAR	Elective
9	M	77	CVD, CKD, hypertension	60	Unfit for open repair	Elective
10	M	66	COPD, hypertension	55	None	Elective
11	M	72	CVD, IHD, CKD, hypertension	55	Unfit for open repair	Elective

CKD: chronic kidney disease; COPD: chronic obstructive pulmonary disease; CVD: cerebrovascular disease; DM: diabetes mellitus; EVAR: endovascular aneurysm repair; F: female; IHD: ischemic heart disease; M: male; NSCLC: non-small-cell lung carcinoma; TEVAR: thoracic endovascular aneurysm repair.

^aContained rupture.

Aneurysm characteristics

Median maximal aneurysm diameter was 60 (52–78) mm; the patient with an aneurysm diameter below 55 mm presented with a contained rupture (Table 2). Median infrarenal neck diameter and length were 37 (28–43) and 25 (0–46) mm, respectively. In the two patients with no infrarenal neck, open repair was discussed. However, in the patient with metastasized lung cancer, we felt that open repair would result in the patient recovering from major surgery in the last months of his life, which would not be in his best interest. The other patient refused open repair and therefore we offered the funnel technique. The aortic neck was conical in seven patients. Two patients had both a suprarenal and infrarenal aortic neck angulation of more than 60°. Moderate calcifications were present in one patient and thrombus involving more than 50% of the aortic circumference was present in four patients. Median oversizing of the thoracic stent grafts at the infrarenal neck was 14% (2–43%). The patient with the largest infrarenal neck diameter presented with a contained rupture and required urgent treatment with the largest available stent graft at our clinic, which resulted in only 2% oversizing. Due to the definition we used for aortic neck diameter and the high incidence of conical necks, the reported oversizing seems to be an underestimation of reality. When oversizing is calculated based on the smallest diameter of the first 20 mm of the aortic neck that is critical for sealing by the stent graft, median oversizing was 25% (13–82%).

Table 2.

AAA anatomical characteristics.

	Aortic neck length (mm)	Mean aortic neck diameter (mm)	Aortic neck angulation suprarenal/infrarenal (°)	Stent graft	Stent graft diameter (mm)	Oversizing (%)
1	45	35	88/69	AUI	40	14
2	25	40	35/58	AUI	44	9
3	23	40	0/37	AUI	46	15
4	30	38	10/39	AUI	44	16
5	0	43	26/44	AUI	44	2
6	18	37	25/40	AUI	40	8
7	30	37	20/35	AUI	42	15
8	41	33	21/34	AUI	38	14
9	46	33	97/107	BF	40	23
10	0	40	32/0	BF	44	9
11	20	28	32/57	BF	40	43

AAA: abdominal aortic aneurysm; AUI: aorto-uniiliac stent graft; BF: bifurcated stent graft.

Patient outcomes

Endoleaks were present at completion angiography in three patients (one type I and two type II endoleaks). The natural history of the type I endoleak could not be determined because the patient died two months after surgery (Table 3). One type II endoleak from an accessory renal artery persisted at the postoperative CTA but did not result in aneurysm sac expansion. The other type II endoleak resolved spontaneously. We did not observe any limb stenosis, occlusion, or kinking. The patient with the type II endoleak from an accessory renal artery developed a late type IA endoleak with aneurysm sac expansion, which was left untreated due to dementia and poor functional status. The patient with the least oversizing (2%) experienced stent graft migration and required conversion to open repair because of aneurysm sac expansion and persisting contained rupture at seven months after surgery. No other reinterventions were required. At one year after surgery, median aortic diameter shrunk by 9 mm (range −2 to 16 mm).

Table 3.

Complications.

	Early endoleak (≤30 days)	Late endoleak (>30 days)	Early reintervention (≤30 days)	Late reintervention (>30 days)	Aneurysm growth at one year (mm)	Perioperative systemic complications (≤30 days)	Dead	Follow-up (months)
1	–	–	–	–	−16	AKI, buttock claudication	No	26
2	–	–	–	–	−1	IHCA, CABG, AF, AKI, delirium	Yesa	20
3	Type IA	–	–	–	Unknown	MI, AKI, delirium, readmission	Yesb	2
4	–	–	–	–	2	Wound infection left groin, readmission	Yesc	11
5	Type II	–	–	Open repair	Unknown	–	No	14
6	–	–	–	–	−9	–	No	21
7	–	–	–	–	−9	AF	No	53
8	–	–	–	–	−9	Pneumonia, CHF, UTI, readmission	No	36
9	Type II	Type IA	–	–	10	–	No	13
10	–	–	–	–	−3	–	No	14
11	–	–	–	–	−15	–	No	11

AF: atrial fibrillation; AKI: acute kidney injury; CABG: coronary artery bypass grafting; CHF: congestive heart failure; IHCA: in-hospital cardiac arrest; MI: myocardial infarction; UTI: urinary tract infection.

^aDied of an upper gastrointestinal bleeding at 20 months after surgery.

^bDied of cardiorenal syndrome at two months after surgery.

^cDied of unknown cause at 11 months after surgery.

No patients died in the first 30 days after surgery. Perioperative complications occurred in six patients (Table 3). Median follow-up time was 14 (2–53) months. One patient who had a perioperative myocardial infarction died of cardiorenal syndrome at two months after surgery; this was the patient with the early type I endoleak. One patient died at 20 months postoperative due to upper gastrointestinal bleeding. One patient died of unknown cause at 11 months after surgery.

Discussion

Endovascular aneurysm repair is generally not recommended for patients with a proximal aortic neck diameter greater than 32 mm because of the increased risk of endoleak due to inadequate proximal sealing. The funnel technique, in which a large thoracic stent graft is used as a proximal extension of a bifurcated or aorto-uniiliac device, allows treatment of aneurysms with wide aortic necks with a relatively simple endovascular procedure. This study confirmed the feasibility of this new technique.

The current series of 11 patients in whom we used a thoracic stent graft for proximal sealing in infrarenal aneurysms with wide aortic necks constitutes the largest experience in published literature. Due to the difficulty to achieve adequate proximal sealing, endovascular repair of aneurysms with hostile neck anatomy is associated with type I endoleaks in 2% of patients in the perioperative period and in 10% of patients at one year after surgery.⁸ In our series, completion angiography showed endoleaks in 27% of patients. One patient had a type I endoleak for which proximal graft extension was not possible, and we decided to observe this endoleak as the majority may resolve spontaneously.⁹ Unfortunately, it could not be followed up because the patient died of cardiorenal syndrome at two months after surgery. The other two patients had type II endoleaks that are usually not of clinical significance and are unrelated to aortic neck morphology. Indeed, one type II endoleak persisted but did not result in aneurysm sac expansion. The other type II endoleak resolved spontaneously, but later this patient experienced stent graft migration with aneurysm sac expansion, which required conversion to open repair. This complication was probably caused by the limited oversizing of the particular stent graft and the reduced suprarenal fixation of thoracic stent grafts without anchor pins in combination with the early type II endoleak. At the moment of aortic rupture, this patient was unfit for open surgery as he was being treated for advanced lung cancer. However, his pulmonary metastases were unexpectedly found to be stable and as he gradually recovered from his oncological treatment, he was considered fit enough for open repair at seven months after index surgery. Even though the majority of our patients were selected for unsuitability for open repair, no patients died in the first 30 days after surgery. During follow-up, one patient died at two months after surgery of cardiorenal syndrome as a result of perioperative myocardial infarction and one patient died at 20 months postoperative due to upper gastrointestinal bleeding. One patient died of unknown cause at 11 months after surgery. Although we were successful at preventing aneurysm rupture, all-cause mortality in our cohort was relatively high and further experience is necessary to refine patient selection. In particular, two out of four patients who were unfit for open surgery died within one year of aneurysm repair. It may be argued that aneurysm repair had no influence on overall life expectancy in these patients and therefore was not necessary.

Alternative treatment options for patients with an infrarenal aneurysm with a hostile neck unable to undergo open repair are either conservative management or complex endovascular procedures with branched, fenestrated, or chimney stent grafts. The EVAR-2 randomized controlled trial compared endovascular aneurysm repair (within instructions for use) with best medical therapy in patients unfit for open repair.¹⁰ Endovascular aneurysm repair did not improve survival over conservative management, often led to graft-related complications and was considerably more expensive than best medical therapy. The study has been criticized for its high crossover rate from conservative management to endovascular repair and for the high rate of aneurysm rupture before surgery after randomization to endovascular repair. Despite these limitations, the trial raises the question whether we should offer endovascular aneurysm repair to unfit, high-risk patients in the first place.

The goal of fenestrated, branched, and chimney stent graft repair is to extend the proximal sealing zone while preserving blood flow to the visceral arteries. Fenestrated and branched endovascular aneurysm repairs are performed using custom-made endografts with holes that have to be secured to the visceral arteries with bare metal stents or with preattached covered stents, respectively. These repairs are challenging, costly, and time-consuming procedures and are not suitable for urgent situations. In endovascular repair with chimneys, covered stents are deployed alongside the main endograft to preserve perfusion to branch vessels. This technique is less complex but has a greater risk of endoleaks through gutters between the stent graft and the chimneys. In a systematic review of observational cohort studies, clinical outcomes of endovascular repair of juxtarenal aneurysms with fenestrations and chimneys were compared.¹¹ Type I endoleaks were present after surgery in 4% of fenestrated repairs and in 8% of chimney repairs. Since almost half of the type I endoleaks in the chimney group resolved spontaneously, reintervention rates were similar in the two groups (11 and 10%, respectively). The 30-day mortality rate was 1% in the fenestrated group and 4% in the chimney group, but chimney repairs were also done for urgent cases with greater expected mortality. For comparison, 30-day mortality after open aneurysm repair requiring suprarenal clamping in medically fit patients was 3% in a contemporaneous population-based registry.¹² Taken together, short-term clinical outcomes of the funnel technique seem to be comparable with the published experience of fenestrated and chimney endovascular aneurysm repair, although more evidence is required to determine the place of the funnel technique in the treatment of aortic aneurysms.

The outcome of endovascular aneurysm repair with the funnel technique for wide proximal aortic necks from previous case reports is summarized in Table 4.^13–17 Out of 12 published cases, three patients experienced endoleak. One patient had a type I endoleak that resolved spontaneously. The second patient experienced a contained rupture, which was left untreated due to the patient’s poor functional status. The third patient had two type I endoleaks and needed reintervention 490 days after the index procedure. No other patient required reintervention, no patients died in the first 30 days after surgery, and one aneurysm-related death was reported during follow-up. These findings are in line with our experience and document the feasibility of the funnel technique as a treatment for infrarenal aneurysms with a wide proximal aortic neck.

Table 4.

Overview current literature.

	Aortic neck diameter (mm)	Stent graft diameter (mm)	Stent graft type	Endoleak	Reintervention	Mortality	Follow-up (months)
Grey et al.¹³
Case 1	40	42	Talent	Yesa	No	No	36
Ronsivalle et al.¹⁴
Case 2	38	44	Talent	No	No	Yesb	48
Case 3	35	44	E-Vita	No	No	No	24
Case 4	36	40	Valiant	No	No	No	12
Case 5	43	44	E-Vita	No	No	No	24
Jim et al.¹⁵
Case 6	35	40	Zenith TX2	No	No	No	18c
Case 7	37	40	Zenith TX2	No	No	No	18c
Case 8	36	40	Zenith TX2	Yesd	No	Yese	3
Pecoraro et al.¹⁶
Case 9	36.5	40	Valiant	No	No	No	6
De Bruijn et al.¹⁷
Case 10	32	40	Valiant Captiva	Yesf	Yesf	No	29
Case 11	36	40	Valiant Captiva	No	No	No	13
Case 12	35	40	Valiant Captiva	No	No	No	11

^aResolved spontaneously at four months.

^bDue to prostatic cancer.

^cMinimum follow-up duration.

^dCT imaging showed stranding around the aneurysm sac with dramatic enlargement consistent with a pseudoaneurysm or contained rupture, which was left untreated due to the patient’s overall poor state.

^eDied at three months after surgery.

^fSuccessful treatment with deployment of a proximal Valiant extension with endoanchors, embolization internal iliac artery, and bilateral distal extension (490 days after the index procedure).

Conclusion

The use of thoracic stent grafts for endovascular repair of infrarenal aneurysms with a wide proximal neck is feasible. Although some would consider that sealing in a diseased dilated neck conflicts with basic concepts of endovascular surgery, 30-day mortality, type I endoleak, and reintervention rates are low in our experience as well as in previously published case reports. The funnel technique is a relatively simple procedure compared to endovascular repair with fenestrated, branched, or chimney stent grafts and can readily be used in urgent cases. However, the number of patients treated with this technique is small and more experience and longer follow-up are required to determine its place within the endovascular armamentarium for patients unsuitable for open aneurysm repair.

Footnotes

Acknowledgments

Oral presentation, Vaatdagen, Noordwijkerhout, 12 April 2016.

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.

References

Prinssen

Verhoeven

Buth

et al . A randomized trial comparing conventional and endovascular repair of abdominal aortic aneurysms. N Engl J Med 2004; 351: 1607–1618.

Lederle

Freischlag

Kyriakides

et al . Outcomes following endovascular vs open repair of abdominal aortic aneurysm: a randomized trial. JAMA 2009; 302: 1535–1542.

Greenhalgh

Brown

Powell

et al . Endovascular versus open repair of abdominal aortic aneurysm. N Engl J Med 2010; 362: 1863–1871.

Schanzer

Greenberg

Hevelone

et al . Predictors of abdominal aortic aneurysm sac enlargement after endovascular repair. Circulation 2011; 123: 2848–2855.

Levey

Bosch

Lewis

et al . A more accurate method to estimate glomerular filtration rate from serum creatinine: a new prediction equation. Ann Intern Med 1999; 130: 461–470.

Khwaja

KDIGO clinical practice guidelines for acute kidney injury. Nephron Clin Pract 2012; 120: 179–184.

Chaikof

Blankensteijn

Harris

et al . Reporting standards for endovascular aortic aneurysm repair. J Vasc Surg 2002; 35: 1048–1060.

Antoniou

Georgiadis

Antoniou

et al . A meta-analysis of outcomes of endovascular abdominal aortic aneurysm repair in patients with hostile and friendly neck anatomy. J Vasc Surg 2013; 57: 527–538.

Tan

Eslami

Rybin

et al . Outcomes of patients with type I endoleak at completion of endovascular abdominal aneurysm repair. J Vasc Surg 2016; 63: 1420–1427.

10.

EVAR trial participants. Endovascular aneurysm repair and outcome in patients unfit for open repair of abdominal aortic aneurysm (EVAR trial 2): randomised controlled trial. Lancet 2005; 365: 2187–2192.

11.

Bai

et al . Fenestrated and chimney technique for juxtarenal aortic aneurysm: a systematic review and pooled data analysis. Sci Rep 2016; 6: 20497.

12.

Deery

Lancaster

Baril

et al . Contemporary outcomes of open complex abdominal aortic aneurysm repair. J Vasc Surg 2016; 63: 1195–1200.

13.

Grey

Butterfield

Nasim

Successful endovascular repair of a ruptured abdominal aortic aneurysm in a patient with unfavorable anatomy. J Vasc Surg 2006; 43: 831–833.

14.

Ronsivalle

Faresin

Franz

et al . Funnel technique for EVAR: “a way out” for abdominal aortic aneurysms with ectatic proximal necks. Ann Vasc Surg 2012; 26: 141–148.

15.

Jim

Fajardo

Geraghty

et al . Use of zenith TX2 endografts in endovascular abdominal aortic aneurysm repair for large-diameter aortic necks. Vascular 2012; 20: 113–117.

16.

Pecoraro

Pakeliani

Dinoto

et al.

Endovascular treatment of large and wide aortic neck: Case report and literature review. Gen Thorac Cardiovasc Surg 2017; 65: 219–224.

17.

de Bruijn

Tournoij

Heuvel

et al . Endovascular treatment of complex abdominal aortic aneurysms by combining different types of endoprostheses. Vascular 2016; 24: 425–429.