Author + information
- Received July 13, 2000
- Revision received May 7, 2001
- Accepted June 19, 2001
- Published online October 1, 2001.
- Marcus H Howell, MD∗,
- Neil Strickman, MD, FACC∗,
- Ali Mortazavi, MD, FACC∗,
- Charles H Hallman, MD† and
- Zvonimir Krajcer, MD, FACC∗,* ()
- ↵*Reprint requests and correspondence:
Dr. Zvonimir Krajcer, 6624 Fannin, Suite 2780, Houston, Texas 77030
This study evaluated the clinical effectiveness of the Medtronic AneuRx stent-graft in patients with infrarenal abdominal aortic aneurysms (AAAs) who were treated in an endovascular suite.
The use of endovascular stent-graft prosthesis for the treatment of AAAs is receiving increasing attention as an alternative to standard surgical repair. Endovascular treatment of AAAs offers the potential to avoid the significant morbidity and mortality associated with surgical repair.
In this series, 215 patients have undergone AAA exclusion with the AneuRx stent-graft. Six-month follow-up is available in 132 patients; one-year follow-up is available in 84 and two-year follow-up in 22.
Of the patients, one hundred ninety-two (89%) were male; 87% had hypertension, and 58.6% were American Society of Anesthesiologists grade IV or higher. The procedural success was 99.5%; we were unable to place the device in one patient. There was no procedural or one-month mortality. There were no acute conversions to surgical repair. One patient had a non–Q-wave myocardial infarction 24 h after the procedure. Endoleaks were present in 82 patients (42%) at discharge, 15 patients (11.3%) at six months and 10 patients (11.9%) at one year. Twenty-two patients had a secondary procedure for endoleak repair of which three were conversions to surgical repair. Twelve late deaths have occurred, none due to device failure or AAA rupture. Mean hospital stay was 1.9 days.
These results reveal that infrarenal AAAs can be safely and successfully treated in an endovascular suite with the AneuRx stent-graft. Further follow-up is needed to determine the long-term efficacy of endoluminal treatment to prevent rupture and death due to AAAs.
The incidence of abdominal aortic aneurysms (AAAs) is increasing. The prevalence of AAAs in men over age 65 ranges from 4.3% to 8.8%; if untreated, the natural history is gradual expansion and possible rupture (1,2). Although highly effective in preventing such rupture, open surgical repair is associated with mortality rates of 2% to 8% (average: 4%) (1,3). Because of the high prevalence of comorbid medical conditions in patients undergoing surgical AAA repair, the morbidity rates in high-risk patients can be as high as 30% (3). Complications include myocardial infarction, abdominal ischemia, arrhythmias, congestive heart failure (CHF), pulmonary insufficiency, renal impair
ment, bleeding (requiring transfusion), distal thromboembolism and wound infection. Endovascular repair using stent-grafts is a less invasive procedure that may avoid many of these risks and has consequently gained increased popularity with both physicians and patients. Endovascular stent-graft techniques for the repair of AAAs offer less pain, shorter hospitalization and recovery time (4–6). Stent-graft treatment of AAAs has advanced rapidly since first used for endovascular exclusion of an infrarenal AAA by Parodi and associates (7)in 1990. Although the technology is still in its infancy, significant improvements have recently been made in the design and delivery of endovascular stent-grafts. These improvements in profile and deliverability potentially lower the possible need for urgent major vascular surgery.
Due to these improvements, we performed these procedures in an endovascular suite as opposed to a surgical operating room. Therefore, this study evaluated the safety and short-term clinical effectiveness of the Medtronic AneuRx stent-graft system in patients with infrarenal AAAs who were treated in an endovascular suite.
Study design and patient population
Patients treated with the AneuRx system were initially enrolled as part of a phase III prospective clinical trial. The Institutional Review Board approved the study protocol as defined by Food and Drug Administration regulations. Enrollment of patients began in November 1998. All enrollees provided written informed consent.
Candidates for the study were selected from patients referred to cardiology practices at a tertiary medical center. They had nonruptured infrarenal AAAs that possessed: 1) a diameter of >5 cm; 2) a diameter of 4.5 to 5.0 cm, with a 0.5-cm increase during the preceding six months; 3) a diameter twice that of the normal infrarenal aorta; or 4) a saccular shape. Additional requirements included a minimal neck, comprising a 1-cm length of nonaneurysmal aorta, measuring 18 to 25 mm in diameter and located immediately inferior to the most inferior major renal artery. Iliac artery requirements include a luminal caliber that allowed access with a 21F delivery catheter on one side and a 16F sheath on the other side and a maximal distal iliac diameter of 16 mm. Patients had to be willing to undergo follow-up examination at 1, 6 and 12 months and yearly thereafter.
Exclusion criteria included age <18 years, an acutely ruptured aneurysm, pregnant or nursing status, suprarenal or inflammatory aneurysms, hypercoagulability, active systemic infection, inability to give informed consent and inability to return for follow-up visits.
Before entering the study, each patient had a complete history and physical examination. Diagnostic imaging with contrast computed tomography (CT) and angiography, with a calibrated pigtail catheter, was performed to characterize the aneurysm and iliac vessels and to ensure that each patient met the study qualifications.
Endovascular stent-graft device
The Medtronic AneuRx stent-graft is a modular, bifurcated system designed to isolate an aneurysm from blood flow. The outside of the graft is fully stented, with self-expanding nickel-titanium stent rings. The graft is made of noncrimped, woven polyester and is sutured to the nitinol stent. The device consists of a bifurcated main segment and a contralateral iliac segment. Additional modular components include aortic and iliac extender cuffs. The stent-graft is implanted transluminally in the aortoiliac position via a retrograde approach from the femoral arteries using AneuRx delivery catheters: a 21F catheter for the main segment and a 16F catheter for the iliac segment. The aortic neck of the bifurcated stent-graft ranges from 20 to 28 mm in diameter. The main segment of the stent-graft has a proximal aortic cuff that secures the device in place with a frictional seal. The straight iliac limbs range from 12 to 16 mm in diameter. Its length can be adjusted with distal extender cuffs.
Endovascular treatment procedure
On the basis of diagnostic imaging, an endovascular stent-graft of the appropriate size was selected. The aortic and iliac stent-graft device diameter was oversized by 10% to 20% over what was measured by CT and angiography. The procedures were performed in an endovascular suite modified for peripheral endovascular imaging and interventional procedures. The endovascular suite is equipped with a floor mounted 16-in. image intensifier with digital subtraction and roadmapping capabilities. All procedural imaging was performed with digital subtraction angiography. The room was designed and ventilated so that vascular surgical procedures could be performed with sterile technique. The patients were routinely prepped as for open surgical repair. All procedures were performed under general anesthesia. Heparin was administered intravenously to achieve and maintain an activated clotting time above 250 s. Access for the 21F delivery system was via surgical exposure of the femoral artery or via a percutaneously placed 22F, 20-cm long sheath (Cook Inc., Bloomington, Indiana). At the end of the procedure, a vascular surgeon performed femoral artery repair. Contralateral femoral artery access for the 16F iliac limb device was obtained percutaneously via a 16F, 30-cm long sheath with a hemostatic valve (Cook Inc.). When the deployment of the contralateral iliac limb was completed, a 10F Prostar XL Percutaneous Vascular Surgery Device (Perclose, Inc., Menlo Park, California) was used for femoral artery closure. After insertion of the stent-graft, a computerized, power-injected, abdominal aortic and iliac angiogram with delayed imaging was routinely performed. If an endoleak was identified and located, additional endovascular treatment was performed. This included balloon angioplasty or extender cuff placement at the site of the endoleak. If the abdominal angiogram did not definitively rule out an endoleak, a selective injection was made in each limb of the stent-graft in several angulations. An endoleak is defined as flow of blood into the aneurysm sac between the endovascular graft and the aortic wall but not into the abdominal cavity. Interventional cardiologists inserted the AneuRx stent-graft, and vascular surgeons performed the arteriotomies and femoral artery repairs in the endovascular suite.
Patients were extubated in the endovascular suite and routinely monitored in the cath lab holding area for 1 h to 2 h before they were sent to a telemetry hospital room. They were not routinely admitted or monitored in the postoperative intensive care unit (ICU). The patients remained in the hospital overnight for observation. If there were no contraindications, they were discharged the following day. All patients underwent flat-plate abdominal radiography and physical examination before they were discharged from the hospital.
AneuRx group follow-up protocol
The follow-up imaging protocol changed slightly after the completion of the phase III trial. During the phase III trial, all the patients with endoleaks had CT scans with contrast before their discharge from the hospital. All CT scans were performed with 3-mm thick slices, delayed images and three-dimensional reconstruction. After completion of enrollment in the phase III trial, the protocol was changed so that all patients had a CT scan with contrast and delayed images performed at one month after the procedure. In the phase III trial (first 64 patients), all patients with endoleaks on their predischarge CT scan had repeat CT scans with contrast at one month. The patients (during the phase III trial) with no endoleak on their postprocedure digital subtraction angiogram or predischarge CT scan only had abdominal duplex ultrasound and plain X-ray imaging at one month. If the ultrasound was suspicious for endoleak or the X-ray showed migration of the stent-graft, the patient had a contrast CT scan performed. The phase III trial patients all had a contrast CT scan at six months and yearly afterward, with more frequent CT scans if endoleaks were detected (Fig. 1).
Since the completion of the phase III trial (next 151 patients), contrast CT scans were performed at one month in all patients regardless of their postprocedure endoleak status. If an endoleak was identified, the patient was taken for angiography. All patients receive contrast CT scans at six months and yearly thereafter with more frequent CT scans if an endoleak is identified.
Cumulative patency and survival rates were calculated using the Kaplan-Meyer life table analysis. Figures are expressed as mean ± SD where applicable.
Between November 1998 and April 2001, 215 patients were enrolled in the AneuRx stent-graft study (Table 1). They included 192 men (89%) and 23 women (11%) whose ages ranged from 48 to 90 years (mean: 72 ± 8.2 years). These patients had multiple comorbidities, making them a moderate-to-high risk group, as defined by previous studies (3,8). In 58.6% of the cases, the American Society of Anesthesiologists operative risk classification was grade IV or higher (8). Ninety-eight patients (45.5%) had a history of myocardial infarction; 51 (23.7%) had CHF, and 121 (56.2%) had a history of coronary revascularization. Ninety-two patients (42.7%) had chronic obstructive pulmonary disease, and 45 (20.2%) had a “hostile” abdomen because of previous abdominal surgery in the area of the aneurysm. The mean AAA diameter was 55.5 ± 11 mm (range: 33 to 100 mm). Six-month follow-up information was available for 132 patients; one-year information was available for 84 patients and two-year follow-up in 22 patients.
Results of the primary procedure
The AneuRx stent-graft was successfully deployed in 214 patients (Table 2). The 22F sheath could not be advanced in only one patient because of diffuse, bilateral, iliac artery atherosclerotic disease. Before the procedure, 40 patients (18.6%) required iliac angioplasty to facilitate passage of the 22F sheath. In 174 patients, the Prostar XL device (Perclose Inc., Menlo Park, California) was used for percutaneous closure of the femoral artery through which the 16F iliac-limb device had been delivered. Twenty-six patients had both femoral arteries closed percutaneously with the ProStar XL device. Blood loss averaged 352 ml per patient; 11 patients (5.1%) required packed red blood cell transfusions. The mean hospital stay was 1.9 ± 3 days. One hundred thirty-two patients (61.3%) were discharged home the day after the procedure. Five patients (2.3%) required postprocedure ICU monitoring; three had planned aortomonoiliac stent-grafts placed followed by femoral to femoral artery bypass and, due to surgical protocol, were monitored in the postoperative ICU. Two patients with severe pulmonary disease required gradual recovery from general anesthesia and were monitored in the postoperative ICU, both for less than 24 h.
Procedural adverse events
No periprocedural deaths or acute surgical conversions occurred. One patient with a history of coronary artery disease and CHF had a non–Q-wave myocardial infarction and CHF 24 h after the procedure. He responded quickly to standard therapy and was discharged six days after the procedure. Four patients had femoral or iliac artery dissection related to the 22F sheath: one dissection required an iliac stent, and the three femoral artery dissections were repaired at the time of surgical closure. Five patients had iliac artery thrombotic occlusion requiring Fogarty thrombectomy immediately after the procedure; at one-month follow-up examination, they were without evidence of limb ischemia. No embolic complications were observed.
Endoleaks were classified into four types (9,10): 1) type I or a perigraft leak due to poor proximal or distal graft attachment or seal; 2) type II or collateral backflow due to patent lumbar, inferior mesenteric or intercostal arteries feeding into the excluded aneurysm sac; 3) type III due to fabric tear, modular or graft disconnection or graft disintegration; and 4) type IV or transgraft flow caused by the high porosity of the graft, most likely created by the numerous suture holes holding the graft material to the stent. Eighty-two patients (42%) had postprocedure endoleaks documented by digital subtraction angiography. Seventy-seven (94%) of these postprocedure endoleaks were type IV, two (2.4%) were type I, and three (3.6%) were type II. At one month, all of the type IV endoleaks had resolved. Of the 132 patients for whom six-month follow-up information was available, 15 (11.3%) had endoleaks, 13 of which were new (Table 3). Of these patients, none had diameter enlargement of their aneurysm. At one-year follow-up, 10 of 84 patients (11.9%) had endoleaks, six of which were new.
Secondary procedures for endoleaks
None of the 77 type IV endoleaks diagnosed on postprocedure digital subtraction angiography required treatment; all resolved spontaneously (Table 4). Subsequently, 22 patients have required treatment for endoleaks of which 19 were endovascular treatments and 3 were conversions to open surgical repair.
One patient had treatment of an endoleak before six-month follow-up. This patient required two coil embolization procedures for a persistent type II endoleak; the first procedure, documented at one month, was performed for internal iliac branch collateral backflow, and the second procedure, documented at six months, was performed for inferior mesenteric artery branch collateral backflow. Despite the persistent endoleak, this patient’s aneurysm had not grown.
In the 15 patients who had endoleaks at six months, 13 of these had no postprocedural or one-month endoleaks. Nine of the new endoleaks were categorized as type II, due to collateral back flow. Four of these patients underwent coil embolization of the collateral vessel. None of these aneurysms has increased in diameter. The other six endoleaks were categorized as type I, two due to proximal aortic attachment-site leak and four due to a distal iliac attachment-site leak. Four of these patients were successfully treated with extender cuffs. One patient had to be converted to open repair because of the inability to advance a distal extender cuff delivery device to the location of the leak. The other patient underwent aortic cuff placement but, because of persistent proximal endoleak and diameter enlargement of the AAA, was converted to open surgical repair. The five other patients who had type II endoleaks at six months had spontaneous closure of their endoleak at one-year follow-up.
Eight of 10 endoleaks present at one-year follow-up were due to collateral back flow, of which six underwent coil embolization of the collateral vessel. The other two type II endoleaks spontaneously closed at 18-month follow-up. None of them had diameter enlargement of their aneurysm. Two patients had a type I endoleak at one year, both underwent iliac cuff placement and had no endoleak at 18-month follow-up.
Three patients had new endoleaks at two-year follow-up. Two patients had a type II endoleak, and both underwent successful coil embolization of the collateral vessel. The other patient had a type III endoleak due to modular separation of an aortic cuff and the main body of the stent graft due to distal migration of the stent graft. Due to aneurysm enlargement, this patient underwent successful, uncomplicated conversion to open surgical repair.
Mortality and morbidity
During the first month, there was no mortality in the AneuRx treated patients. Twelve late deaths have occurred, all related to comorbid conditions and not due to device failure or AAA rupture. Six (2.7%) patients had localized groin infections at the surgical cut down site requiring antibiotics. Two of these patients required surgical drainage and intravenous antibiotics. Twenty patients had mild postprocedural hematomas that resolved with conservative therapy. No patient had a femoral artery pseudoaneurysm or fistula. Eight patients had transient femoral neuropathy on the side of femoral artery cut down; all resolved by one-month follow-up. Five patients had mild hematuria, and one patient had a lower urinary tract infection requiring antibiotics. One patient presented at six months with iliac limb occlusion. He was successfully treated with Fogarty thrombectomy. He was also found to have a stenosis in the left iliac limb of the stent graft, which was treated with angioplasty of the iliac limb.
One patient presented at two-year follow-up with one month of fever and fatigue. Work-up revealed and infected AAA sac. The patient had no endoleak on contrast CT. This patient underwent successful, uncomplicated surgical removal of an intact stent-graft, along with surgical repair of the AAA. Surgical exploration revealed a peptic ulcer that had eroded into the AAA sac.
Access site closure
The 16F femoral artery access site was closed percutaneously in 174 patients with a 10F Prostar XL percutaneous vascular surgery device (11). This percutaneous closure technique was attempted in 188 patients, with successful closure in 174 patients (92.5%). The 14 patients in whom this procedure failed had surgical repair of the access site. This technique, using 2 Prostar XL devices, was attempted to close the 22F access site in 27 patients (12). Twenty-six of the 27 patients (96%) had successful closure of the 22F femoral artery access site and, thus, complete percutaneous AAA repair.
The early results for the 215 patients who had AAA repair with the AneuRx stent-graft in this study compare favorably with those of previous studies. In a prospective, matched study of 250 AAA patients, Zarins and colleagues (4)compared open surgical repair (60 patients) with endovascular repair using the AneuRx stent-graft (190 patients). In their study, the endoleak rate was 22% before hospital discharge and 9% at one month. The endoleak rates in this series were 42% after the procedure and 11.3% at six months. During the first month, Zarins and associates (4)reported five deaths (2.6%) in their AneuRx group. There was no one-month mortality in this series.
The six-month and one-year endoleak rates in this study, of 11.3% and 11.9%, respectively, compare favorably with the 9% to 44% rates reported for a variety of endovascular stent-grafts (5,6,13–18).
Fifteen patients (11.3%) in this series had endoleaks at six months, and 10 required treatment, but none had revealed an increase in their aneurysm diameter. Nine of these endoleaks were type II, four of which were treated by coil embolization. The five other type II endoleaks were followed closely with CT scans because the collateral artery causing the endoleak was small, and their AAAs had decreased in diameter. The other six endoleaks at six months were type I, five of which were successfully treated with extension cuffs. Due to prior iliac artery stenting, an AneuRx cuff could not be advanced to the site of the other type I endoleak, and this patient was converted to open repair. It is unclear from previous publications what to do about early type II endoleaks that are not resulting in aneurysm expansion. Close observation is usually sufficient initially because some will close spontaneously, as seen in this study. Type II endoleaks that are resulting in AAA expansion or are persistent should be treated aggressively. Current experience supports aggressive treatment of endoleaks that are type I or III or that result in aneurysmal expansion, as this increases the risk of late rupture (19–21). Endovascular treatment should be attempted first, followed by open repair if the former strategy is unsuccessful.
Most early endoleaks in this series were type IV occurring at the time of stent-graft implantation. We were very aggressive in postdeployment evaluation of endoleaks and liberal use of extender cuffs and balloon angioplasty to resolve type I endoleaks. By one month, all of the type IV endoleaks had closed spontaneously. Transgraft flow, caused by the high porosity of the Dacron and the numerous suture holes holding the graft material to the stent, is a transient phenomenon that terminates spontaneously (4,9,10).
Eight of the 10 endoleaks found at one-year follow-up were type II. None of these patients had diameter enlargement of their aneurysms, but two had diameter decrease. Six of these patients ultimately underwent coil embolization treatment. Two resolved spontaneously.
Conversion and rupture
Most reports cite a surgical conversion rate of 2% to 20% (6,13,22,23). To date, four patients (1.8%) in this study had to undergo open surgical repair, three due to endoleaks and one due to aneurysm sac infection. Two of these patients had diameter increase of their AAA and were the only patients with AAA diameter enlargement to date. Of the patients with one-year follow-up, 57 (71.2%) have had aneurismal diameter reduction, and 21 (26.2%) had no change.
No AAA ruptures or AAA-related mortality have occurred in this series with a mean follow-up of 14 ± 3 months. A recent article by Zarins et al. (24)reviewed all 1,067 patients in the phase I, II and III portions of the clinical trial. They found that, in the 1,046 patients who had successful endovascular AAA repair, aneurysm rupture occurred in seven (0.7%), five of whom died for a rupture-related mortality of 0.5%. Their mean follow-up was 16 months. Thus, it is imperative that all patients treated with this device be followed closely. Because of these ruptures, the threshold for surgical conversion is low for patients with persistent endoleaks and AAA diameter enlargement.
Thus far, only one case of stent migration has been observed in this study, but our follow-up period (mean months: 14 ± 3 months) has not allowed adequate time for full postexclusion aneurysmal morphologic changes to occur (25).
The six patients who had localized groin infections at the surgical cut down site were extremely obese, with body mass indexes over 35 (26). All of these occurred early in the study and at the surgical femoral artery access site. Since treating these cases, the preoperative scrub regimen was changed to include chlorhexidine gluconate (Hibiclens, Becton Dickinson, Franklin Lakes, New Jersey) and povidine-iodine (Betadine, Becton Dickinson). All patients receive oral antibiotics for at least three days after the procedure. Since these changes have been implemented, no further groin infections have occurred.
Arterial access site management
We were able to percutaneously close 92.5% of the 16F femoral artery access sites attempted and 96% of the 22F femoral artery sites attempted. Twenty-six patients had complete percutaneous repair of their AAA. The technique involves the placement of Prostar XL percutaneous vascular device before placement of the access sheath with arterial closure after the case. The arterial access site expands within the confines of the sutures and, thus, is closed by these sutures at the end of the case (11,12). Hopefully, with lower profile endovascular devices and improved percutaneous closure devices for large bore sheaths, the entire procedure will be routinely performed percutaneously without the need for open surgical exposure of the femoral arteries.
The early results in this series show that AAAs can be safely and successfully treated with the AneuRx stent-graft in an endovascular suite. There is no increased morbidity and mortality compared with stent-graft procedures performed in the operating room. There were no AAA ruptures or acute conversions to open surgical repair. The majority of the 16F femoral artery access sites were closed percutaneously, further decreasing the invasiveness of the procedure. To date, there are no reliable long-term follow-up data concerning the durability and efficacy of the endovascular stent-graft procedure in the long-term prevention of rupture and death in patients with AAAs. Nevertheless, owing to the current progress in endovascular stent-graft design, this less invasive procedure should soon gain widespread acceptance as an alternative treatment for selected infrarenal AAAs, especially in patients at high risk for open surgical repair.
- abdominal aortic aneurysm
- congestive heart failure
- computed tomography
- intensive care unit
- Received July 13, 2000.
- Revision received May 7, 2001.
- Accepted June 19, 2001.
- American College of Cardiology
- ↵Zarins C, White R, Schwarten D, et al, for the investigators of the Medtronic AneuRx Multicenter Clinical Trial. AneuRx stent graft versus open surgical repair of abdominal aortic aneurysms: multicenter prospective clinical trial. J Vasc Surg 1999;29:292–308.
- ↵Schwartz S, Shires G, Spencer F, Daly J, Fischer J, Galloway A. Principles of Surgery. 7th ed. American Society of Anesthesiologist (ASA) Physical Status Classification. New York, NY: McGraw-Hill, 1999;1704–5.
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