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J Thorac Cardiovasc Surg 2006;131:1087-1094
© 2006 The American Association for Thoracic Surgery
Surgery for Acquired Cardiovascular Disease |
Division of Cardiothoracic Surgery and Division of Vascular Surgery, Hospital of the University of Pennsylvania, Philadelphia, Pa
Received for publication June 27, 2005; revisions received November 28, 2005; accepted for publication December 22, 2005. * Address for reprints: Joseph E. Bavaria, MD, Brooke Roberts Professor of Surgery, Division of Cardiothoracic Surgery, 4 Silverstein, Hospital of University of Pennsylvania, 3400 Spruce Street, Philadelphia, PA 19104 (Email: joseph.bavaria{at}uphs.upenn.edu).
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Abstract |
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METHODS: From April 1999 to March 2005, 99 patients with descending thoracic aneurysms underwent repair with a first or second-generation commercially produced endograft; 24 patients had an early-generation device, and 75 patients had a late-generation device. Each patient was enrolled as part of 3 distinct Phase I or Phase II Food and Drug Administration-approved clinical trials in accordance with strict inclusion and exclusion criteria.
RESULTS: Mean age was 73.1 years. Symptomatic aneurysms accounted for 42% of the cohort. Mean aneurysm size was 63.7 mm (range: 30-105 mm). Twenty percent of the patients underwent a subclavian carotid transposition or bypass preoperatively to obtain an adequate proximal landing zone. No procedures had to be aborted. In-hospital or 30-day mortality was 5.0%. The incidence of permanent spinal ischemia was 2%. Perioperative vascular complications requiring interposition graft, stent repair, or patch angioplasty occurred in 27% and seemed to be less frequent in the late-generation cohort than the early-generation cohort (22.7% vs 41.7%, respectively, P = .069). At the 30-day follow-up, 23 endoleaks were detected in 22 patients (14.7% in late-generation cohort vs 45.8% in early-generation cohort, P = .001). During the follow-up period, 3 new endoleaks were detected, 3 patients died of aortic rupture, and 10 patients underwent aneurysm-related reintervention. Kaplan-Meier estimated 1, 3, and 5-year survival was 84.5%, 70.5%, and 52.4%, respectively. Freedom from aneurysm-related event, defined as freedom from endoleak, aortic rupture, dissection, or any reintervention on the aorta, was 73%, 69%, and 64% at 1, 3, and 5 years, respectively.
CONCLUSION: Thoracic aortic stent grafting is a safe procedure in selected patients with the added benefit of a low incidence of paraplegia. However, there is an incidence of late complications and reinterventions. This risk requires further quantification and must be balanced against the benefits of a minimally invasive approach with low perioperative morbidity and mortality. Results are improving as technology evolves and our level of experience increases. Radiologic follow-up is mandatory.
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Introduction |
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Recent refinements in open technique, including extracorporeal circulation for peripheral organ preservation and multiple techniques for spinal cord protection, may improve results but are not applied universally. The highly invasive nature of this procedure necessitates a prolonged recovery period. In addition, high-risk patients who were previously denied surgical repair because of comorbidities, including but not limited to pulmonary, cardiac, and renal status, may become surgical candidates if a less-invasive endovascular option was possible. For these reasons, endovascular repair is preferable. The objectives of this article are to report on the hypothesis that results are improving with new stent design iterations and to describe our experience over a 6-year period.
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Methods |
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Early-generation devices were inserted in high-risk patients enrolled in a Phase I study: Investigation of the TALENT Endoluminal Spring Stent Graft System for the Treatment of Thoracic Aortic Aneurysms in High-Risk Patients.
Late-generation devices were inserted in patients who were operative candidates enrolled in 1 of the following Phase 2 trials:
A surgical team consisting of a cardiac surgeon and vascular surgeon performed all operations. Operations were performed under general anesthesia in the cardiac surgery or vascular surgery operating theatre. Recently, a fully equipped endovascular suite was built in the main operating room. All patients recovered postoperatively in the cardiac surgical intensive care unit.
Use of cerebrospinal fluid drains and somatosensory evoked potential monitoring was not standardized in this population but evolved with increasing experience. In our current management paradigm, preoperative lumbar drains and intraoperative somatosensory evoked potential monitoring are used in all patients who are considered high risk for spinal ischemia. These include the following:
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Preoperative Imaging
All potential candidates underwent preoperative aortography or high-definition computed tomography (CT) scanning. CT scans were then digitally reformatted into 3 dimensional 1-mm cuts using MMS technology (Medical Metrx Solutions, West Lebanon, NH), providing a patient-specific model that assists in understanding the relationships between structures and helps in accurately designing a stent graft system. Cerebrovascular assessment was based on angiographically determined vertebral artery patency. No attempt was made at preoperatively imaging intercostal arteries that may supply the spinal cord.
Statistical Analysis
All statistical tests were 2-tailed. Student t tests, chi-square tests, and Fisher exact tests were conducted when appropriate to assess differences between groups. Overall survival and freedom from aneurysm-related event curves were calculated by the Kaplan-Meier method. Calculations were performed using SPSS (SPSS for Windows, Version 12.0, SPSS Inc. Chicago, Ill).
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Results |
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Procedural data
All 99 patients had successful deployment of the device, and no patients required conversion to open repair. The mean number of devices used per patient was 2.62 (3.04 vs 2.49, early vs late generation, P = .07). The left subclavian was covered in 20 cases (20.8% vs 21.3%, early vs late generation, P = .96) after a scheduled elective carotid subclavian transposition or bypass. The site of vascular access was the femoral artery in 68 cases, iliac artery in 28 cases, and infrarenal aorta in 2 cases (early vs late generation, P > .15). Nineteen patients had a conduit constructed to insert the device (20.8% vs 18.7% early generation vs late generation, P = .82).
Overall, 11% of patients required mechanical ventilation more than 24 hours (20.8% vs 8%, early vs late generation, P = .08). The incidence of renal failure was 3% (8.3% and 1.3%, early vs late generation, P = .08).
Neurologic Complications
Spinal cord ischemia
The total incidence of spinal cord ischemia was 5.1%, with no significant difference between early-generation (4.2%) and late-generation (5.3%) cohorts. There was 1 case of paraplegia, 3 cases of paraparesis, and 1 case of only intraoperative loss of somatosensory evoked potentials while under general anesthesia, which was reversed with blood pressure management and cerebrospinal fluid drainage. Three of the 5 patients had a full recovery, for an incidence of permanent spinal deficit of 2%. Four of 5 patients with spinal ischemia had type C coverage, and 1 patient had a previous abdominal aortic aneurysm repair.
Stroke
One stroke occurred in the early-generation cohort, and 4 strokes occurred in the late-generation cohort (P = .675), for an overall incidence of 5%. All 5 patients had type A or C aortic coverage, and 3 of the 5 patients had a preoperative history of cardiovascular accident. None of the 5 patients had the left subclavian artery covered. Two of the 5 patients made a complete recovery with no deficit at discharge.
Vascular access complications
Vascular complications occurred in 41.7% (n = 10) of the early-generation cohort and 22.7% (n = 17) of the late-generation cohort (P = .069), for an overall incidence of 27% (n = 27). Of these 27 cases, repair involved an interposition graft in 41%, a patch angioplasty in 33%, and a bare metal stent repair in 19%.
Late Outcome
Through the 6-year period of this study, radiologic follow-up was complete in 86% of patients and vital statistics data were available in 100%.
Overall survival
For the entire cohort, 24 of the 99 patients died during the 6-year follow-up. Kaplan-Meier analysis estimated that 1, 3, and 5-year survival was 84.5%, 70.5%, and 52.4%, respectively. Five-year survival was 45% for the early-generation cohort and 55% for the late-generation cohort (P = .24) Figure 2.
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Three patients had an aneurysm-related death after the perioperative period:
Endoleaks
Early
At 30-day follow-up, 23 endoleaks were detected in 22 patients (45.8% and 14.7%, early vs late generation, P = .001). Type I endoleaks accounted for 57% (n = 13), type II endoleaks accounted for 26% (n = 6), and type III endoleaks accounted for 17% (n = 4). There were no type IV endoleaks observed. Of 22 patients with an endoleak, 7 had reinterventions, 4 had an endoleak resolve spontaneously (3 within 6 months; resolution took 2 years in 1 patient receiving Coumadin), 3 were lost to follow-up, and 8 have endoleaks that are currently ongoing and being followed.
Late
A late endoleak developed in 3 patients (3%) that was not present on the 30-day follow-up CT. One patient underwent successful urgent surgical intervention 3 years after endograft placement for a symptomatic (contained rupture) endoleak at the proximal landing zone. One patient (1 year after endograft insertion) is awaiting surgical correction at the time of this writing. One patient (1 year after endograft insertion) is currently undergoing workup.
Reinterventions
Ten patients (10.1%) underwent reintervention on the aorta (25% and 5.3%, early vs late generation, P = .012). Of these 10 patients, 7 had a reintervention for endoleak soon after their 30-day CT scan. Two patients required surgical reintervention on their aorta (discussed previously, 1 patient for late endoleak and 1 patient for dissection caused by the stent graft). One patient had endovascular reintervention for a new aneurysm that was not present at the initial procedure.
Of the 7 patients who underwent reintervention for an endoleak on their 30-day CT, all had endovascular procedures, 6 with graft extensions and 1 with a coil embolization of a type II endoleak. Four of the 7 patients had persistent leaks on follow-up CT despite the reintervention.
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Discussion |
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Since then, thoracic aortic endografts have been used with early success in small to moderate-sized retrospective single-center series.
4-9
Six years ago we enrolled our first patient in an FDA-approved thoracic stent graft trial. During the 6-year period, 99 patients received 5 different endograft models made by 2 manufacturers. For the purpose of this article, 2 of these models were classified as early-generation devices (24 patients) and 3 of these models were classified as late-generation devices (75 patients) on the basis of the mechanics of the device.
The patients in the early-generation cohort were part of a Phase I study and thus not candidates for open surgical repair. As expected, they had a significantly higher risk profile as manifested by an increased incidence of chronic obstructive pulmonary disease, peripheral vascular disease, and previous aortic surgery. However, aneurysm morphology, as defined by location, size, percentage who are symptomatic, and percentage who require preoperative carotid subclavian bypass/transposition, was similar between the 2 cohorts.
Our series and the series in the literature show low perioperative mortality. Although minimally invasive, endografting of DTA is not without negative perioperative outcomes.
Specific Findings of This Study
The main differences in outcomes between the early-generation and late-generation cohorts were noticed in the incidence of endoleaks, reinterventions, and vascular complications. In this study, results over time and with newer generation devices did not improve in regard to perioperative mortality, stroke, or spinal ischemia.
Endoleaks post-DTA stent grafting are a poorly understand phenomenon. In this series, 22% of patients were documented to have an endoleak by a radiologist at their first follow-up CT. The incidence of endoleaks was markedly higher in the early-generation versus the late-generation cohort (45.8% vs 14.7%, respectively, P = .001). Both cohorts had similar incidence of subclavian transposition, distribution of access site vessels, and aneurysm size, indicating that the aortic morphology was comparable in the cohorts. The lower incidence of endoleaks in the late-generation cohort likely reflects that the later generation of devices are easier to deploy at the curved arch and tortuous distal aorta, allowing more precise proximal landing zone deployment. Another reason for improved results with endoleaks is that with more experience we are covering more aorta, being more aggressive with overlapping, and using tapered grafts more judiciously. In addition, as our experience has progressed we have been more aggressive in fixing endoleaks intraoperatively and not leaving the operating theatre if there is an endoleak. This is similar to open surgery, in which we now know that after valvular repair/replacement, paravalvular leaks do not improve and lead to worse long-term outcome.
Vascular complications are sometimes underestimated with this minimally invasive technology. The overall incidence in this series was 27% (41.7% and 22.7% in early and late-generation cohorts, respectively). There was a strong trend, although this value did not reach statistical significance (P = .069). The early-generation devices all required multiple exchanges, which can lead to traumatic peripheral vascular effects. The endograft devices are inserted through sheaths that measure 20F to 25F in diameter and can cause access problems in certain patients. When the femorals are of small diameter or heavily calcified, we find it prudent to access the iliac vessels through a retroperitoneal approach rather than cannulate the femorals. In addition, consideration should be given to sewing on a conduit prophylactically for marginal access anatomy. Significant ileofemoral and infrarenal aortic complications can occur with thoracic endografts. In this study, ileofemoral bypass procedures, angioplasty, and bare stenting were all reported as vascular complications. Thus, it is important to have team expertise in this area.
Spinal cord ischemia is the most dreaded and feared complication of DTA repair. Early reports indicated an incidence of up to 30% with open surgical repair. More recent published data from 2 expert high-volume centers that specialize in open surgical repair of DTA report mortality rates in the range of 4% to 9% and paraplegia rates of less than 3% for isolated DTAs.
10,11
Despite these publications it is hard to judge what the true incidence of spinal ischemia is today with open repair of DTA. Most centers end up doing small volumes, surgical techniques are variable, there is no central registry, and undesirable outcomes are frequently underpublished. In the first completed multicenter comparative trial of endovascular versus an open surgical repair of DTA, the incidence of spinal ischemia was 2.9% in the endograft cohort and 13.8% in the open surgical control cohort.
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When endografting of DTA became a technically feasible option, we hypothesized that 1 of the proposed benefits, in addition to the minimally invasive nature, may be a decreased perioperative incidence of spinal ischemia. Theoretic reasons for lower spinal cord ischemia rates with an endovascular technique include the following:
Conversely, one could postulate that an open technique may confer an advantage for the following reasons.
The incidence of spinal ischemia in this series was 5.1%, with no difference between the early and late-generation cohorts. This is comparable to the incidence of 3.6% to 6.5% in the published literature.
6,14-16
Three of the 5 patients fully recovered by following a published paradigm for management of spinal ischemia.
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Thus, the incidence of permanent spinal cord ischemia after endografting in this series was 2%.
The incidence of stroke was 5%. In a multicenter comparative trial of endografting versus open surgical repair, we previously reported a higher incidence of stroke in patients with subclavian-carotid transposition or bypass and postulated that it may be an indication of higher atherosclerotic burden at the level of the arch. However, in this study none of the 5 patients with stroke underwent a subclavian-carotid transposition or bypass preoperatively. Thus, the incidence and cause of stroke with endografting require further clarification.
Freedom from an aneurysm-related event, as defined by freedom from any endoleak, aortic rupture, dissection, or aortic reintervention, was 64% at 5 years. There were 3 cases of frank aortic rupture; 2 were related to endoleaks, and 1 was caused by an uncovered nitinol stent that ruptured the aorta proximally and led to a retrograde dissection. Retrograde type A dissection from thoracic aortic stent grafting has been reported in the literature.
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We now generally try to avoid the use of uncovered stents.
The Kaplan-Meier estimated 1, 3, and 5-year survival was 84.5%, 70.5%, and 52.3%, respectively, which is consistent with results of thoracic endografting reported in the literature.
6,12,20
Aneurysm-related mortality after the perioperative period was 3%. This indicates that patients with thoracic aortic aneurysms have complex diseases and die of comorbidities unrelated to their thoracic aortic aneurysm. These patients require close follow-up in a multidisciplinary fashion. In a thought-provoking article, Demers and colleagues
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at Stanford questioned whether asymptomatic patients who are deemed to be inoperable for open repair should have even been treated with endografting because survival in this group was bleak. In this study, when patients with symptomatic aneurysms were compared with patients with asymptomatic aneurysms (some of whom were deemed "inoperable") there was no difference in survival. This topic warrants further investigation.
Conclusions/Lessons Learned
when he mentioned that these operations should be conducted in "... highly specialized centres for aortic surgery equipped with fully trained personnel and optimal methods of organ protection." |
Discussion |
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The authors have presented as you have heard their six-year experience with endograft management, specifically with atherosclerotic thoracic aneurysms. It is significant in my mind that their group has in cooperation with their vascular colleagues developed a multidisciplinary treatment program that is incorporated into their training program for future cardiothoracic residents.
Endografts are associated with their own specific technical complications, notably vascular access complications, stroke and endoleak. The gist of this paper is that so-called newer generation grafts, because of more flexible delivery systems and graft material, are associated specifically with decreased complications in vascular access sites, endoleak and improvement in late mortality. Because this is a technique-specific paper, my questions that start off the discussion, five of them, are specifically technical.
The first is, are the strokes related to their need to cover the left subclavian and/or are they related to wire manipulation in the proximal descending thoracic aorta?
Dr. Appoo. That's a very interesting question. All patients where the left subclavian was covered had a preoperative either carotid subclavian bypass or subclavian transposition. In previous work, in a multicenter looking at comparisons between open and endovascular repair, we had shown that 4 out of 5 patients in the endovascular group all had preoperative subclavian transposition indicating what we thought was a higher atherosclerotic burden up at the distal arch and strokes are associated with that. But in this study, none of the five patients who had a stroke actually had preoperative subclavian transposition.
Dr. Karmy-Jones. So it's a little unclear.
Dr. Appoo. It's unclear. I mean we presume that was an indication of higher atherosclerotic burden in those patients having that procedure but that wasn't the case in this situation. As to the wire management, I'm sure that's part of it. We are putting wires all the way up the arch and into the ascending aorta at times in these patients.
Dr. Karmy-Jones. Preoperatively, it leads into the next question, is that, it is an important issue for developing endovascular programs, but how do you assess cerebral circulation preoperatively. Do you favor cerebral angiography or TCD?
Dr. Appoo. We use cerebral angiography to ensure patency of both vertebral arteries.
Dr. Karmy-Jones. I accept your argument that the newer generation grafts are more flexible, etc., but is this benefit across the board with the graft, Gore versus Medtronic, or do you have differences that will shape the choice in any given case? Or can you tell?
Dr. Appoo. We tried very hard in this study not to compare one manufacturer versus another. I think these newer devices have both. They have improvements across and then they have specific things. I think with the Gore device the major advantage is that it is a single exchange device where you don't have to manipulate the vascular access site again and again. The Medtronic has advantages in that it does provide a larger graft, so if you have a patient with a large aorta, even where it is supposedly normal caliber, sometimes that is too big for the Gore device. There are specific benefits of each.
Dr. Karmy-Jones. Did the use of a conduit increase, decrease or have no effect on the incidence of vascular access complications?
Dr. Appoo. Our overall use of conduits was 19%, similar in both groups. Since it was similar in both groups, we can't assume that it improved it but I think maybe our employment of conduits was more judicious.
Dr. Karmy-Jones. Finally, you have noted a greater incidence of comorbidities, particularly COPD, prior aortic surgery, peripheral vascular disease in the earlier group. How is it possible to discriminate between potential selection bias and the benefit of the newer generations given that comparison?
Dr. Appoo. Inclusion/exclusion criteria were different for each of the three FDA studies. As we talked about, phase I study was high risk. The others were high and low risk. I think that is part of it in terms of outcome but the comorbidities probably play a larger role in outcome measurements such as stroke, operative mortality, and long-term outcome. I think device-specific outcomes, things like vascular complications and endoleaks, are probably irrespective of the comorbidities in the different patient populations.
Dr. Karmy-Jones. I'd like to thank the association for the privilege and the pleasure of reviewing this paper. Thank you.
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Footnotes |
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References |
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This article has been cited by other articles:
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  B. W. Ullery, G. J. Wang, D. Low, and A. T. Cheung Neurological Complications of Thoracic Endovascular Aortic Repair Seminars in Cardiothoracic and Vascular Anesthesia, December 1, 2011; 15(4): 123 - 140. [Abstract] [PDF]
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 T. Ueda, H. Takaoka, B. Raman, J. Rosenberg, and G. D. Rubin Impact of Quantitatively Determined Native Thoracic Aortic Tortuosity on Endoleak Development After Thoracic Endovascular Aortic Repair Am. J. Roentgenol., December 1, 2011; 197(6): W1140 - W1146. [Abstract] [Full Text] [PDF]
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 N. D. Desai, A. Pochettino, W. Y. Szeto, G. W. Moser, P. J. Moeller, N. Sodhi, B. Jackson, E. Woo, R. M. Fairman, and J. Bavaria Thoracic endovascular aortic repair: Evolution of therapy, patterns of use, and results in a 10-year experience J. Thorac. Cardiovasc. Surg., September 1, 2011; 142(3): 587 - 594. [Abstract] [Full Text] [PDF]
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 S. T. Mustafa, U. Sadat, M. U. Majeed, C. M. Wong, J. Michaels, and S. M. Thomas Endovascular Repair of Nonruptured Thoracic Aortic Aneurysms: Systematic Review Vascular, February 1, 2010; 18(1): 28 - 33. [Abstract] [Full Text] [PDF]
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M. D. Peterson, G. H. Wheatley III, J. Kpodonu, J. P. Williams, V. G. Ramaiah, J. A. Rodriguez-Lopez, and E. B. Diethrich Treatment of type II endoleaks associated with left subclavian artery coverage during thoracic aortic stent grafting. J. Thorac. Cardiovasc. Surg., November 1, 2008; 136(5): 1193 - 1199. [Abstract] [Full Text] [PDF]
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A. Marui, T. Mochizuki, T. Koyama, and N. Mitsui Degree of fusiform dilatation of the proximal descending aorta in type B acute aortic dissection can predict late aortic events. J. Thorac. Cardiovasc. Surg., November 1, 2007; 134(5): 1163 - 1170. [Abstract] [Full Text] [PDF]
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W. Anthony Lee Management of Aortic Aneurysms and Dissections with the Zenith TX2 Stent Graft Vascular, September 1, 2006; 14(5): 282 - 289. [Abstract] [Full Text] [PDF]
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