Ann Thorac Surg 2007;83:S856-S861
© 2007 The Society of Thoracic Surgeons
Supplement
Thoracoabdominal Aneurysm Repair: A 20-Year Perspective
Mark F. Conrad, MD*,
Robert S. Crawford, MD,
J. Kenneth Davison, MD,
Richard P. Cambria, MD
Division of Vascular and Endovascular Surgery and the Thoracic Aortic Center; Department of Surgery, Harvard Medical School, and the Massachusetts General Hospital, Boston, Massachusetts
* Address correspondence to Dr Conrad, Massachusetts General Hospital, 15 Parkman St, WAC 4, Boston, MA 02180 (Email: mconrad{at}partners.org).
Presented at Aortic Surgery Symposium X, New York, NY, April 27–28, 2006.
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Abstract
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BACKGROUND: A variety of operative approaches and protective adjuncts have been used to minimize organ dysfunction and, in particular, spinal cord injury (SCI) after thoracoabdominal aneurysm (TAA) repair. There is no consensus with respect to the optimal approach.
METHODS: Reviewed were 445 consecutive TAA repairs done between January 1987 and December 2005. Clinical features included urgent operation in 103 patients (22.6%), of which 52 (11.4%) were ruptures. Operative management consisted of a clamp-and-sew technique with adjuncts in 417 patients (92%). Epidural cooling to prevent SCI was used in 240 (68%) extent I to III repairs. Predictors of mortality and SCI were assessed with multivariate analysis, and long-term survival was determined with Kaplan-Meier life-table analysis.
RESULTS: Operative mortality was 8.2% and was associated with preoperative serum creatinine level of 1.8 mg/dL or more (p = 0.005), intraoperative hypotension (p = 0.01), intraoperative transfusion requirement (p = 0.0008), postoperative SCI (p = 0.02), and postoperative renal failure (p < 0.0001). SCI of any severity occurred in 60 patients (13.2%), and 43 (9.5% of the total cohort) sustained major paraplegia. Epidural cooling significantly reduced the risk of SCI in patients with types I to III TAA (13.7% versus 29%, p = 0.01). Independent predictors of SCI included extent I/II aneurysms (p = 0.02), epidural cooling (p = 0.02), urgent/emergent operation (p = 0.02), intraoperative hypotension (p = 0.005), total aortic cross-clamp time (p = 0.01), and postoperative pulmonary complications (p = 0.003). Late survival rates were at 54.4% at 5 years, 28.7% at 10 years, and 20.5% at 15 years.
CONCLUSIONS: Despite the favorable impact of operative adjuncts on perioperative mortality and SCI, major morbidity after TAA remains a challenge; the implications to further develop stent graft strategies are clear.
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Introduction
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The modern era thoracoabdominal aneurysm (TAA) repair at Massachusetts General Hospital began in the mid-1980s when fundamental surgical considerations such as shorter operative and cross-clamp times and greatly diminished blood turnover produced results vastly improved compared with prior experience [1]. Throughout our experience, an emphasis on operative expediency and simplicity has driven our approach. Accordingly, a clamp-and-sew technique, with specific adjuncts directed towards renal and spinal cord protection as well as early reestablishment of mesenteric reperfusion, has been the surgical method applied in some 90% of cases [2, 3]. Distal aortic perfusion provided by partial left heart bypass has been applied selectively, typically in cases where the proximal aortic reconstruction is predicted to be difficult or in cases of chronic dissection in extent I and II aneurysms, or both.
With specific reference to spinal cord protection, in 1993 we developed a technique for regional cord hypothermia with epidural cooling and have previously described its positive impact on decreasing spinal cord ischemic complications compared with historical controls [3, 4]. In this report, our experience is updated and the emerging impact of stent graft repair is considered.
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Material and Methods
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Prospective collection of relative clinical and demographic data has been our policy throughout the study interval, which was January 1, 1997, to December 30, 2005. Aneurysms were stratified according to the Crawford classification in which extent I and II are defined as resection of the entire descending aorta. Isolated descending thoracic aneurysms were omitted from this analysis. Clinical and demographic features are detailed in Table 1.
Mild and severe pulmonary disease was determined by preoperative pulmonary function tests, which were obtained on most patients. Urgent operation was defined as rupture or presentation with acute aortic syndrome necessitating invasive monitoring in an intensive care unit and operative repair within 48 hours of admission. The clinical evaluation protocol was approved by the Institutional Review Board of the Massachusetts General Hospital and consent was waived.
The clamp-and-sew technique with adjuncts was used in 92% of cases, with distal aortic perfusion techniques reserved for patients with anticipated technically complex proximal anastomoses or significant renal insufficiency. Epidural cooling has been used in types I to III TAA for spinal cord protection since July 1993 and was supervised in all cases by a dedicated vascular anesthesia team.
Details of the clamp-and-sew technique and the epidural infusion system have been previously reported [2, 4] In brief, as schematized in Figure 1, the epidural cooling system uses an iced saline epidural infusion which provides for moderate (25° to 27°C) hypothermia to the spinal cord during the critical period when the aorta is cross-clamped. Patent intercostals vessels in the T9-L1 region were reimplanted by means of a separate inclusion button or were preserved with a beveled anastomosis when technically feasible. After reperfusion of the lower extremities, epidural cooling was discontinued and continuous passive cerebrospinal fluid (CSF) drainage was initiated to keep CSF pressure at 10 mm Hg and continued for 48 hours.
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Fig 1. Operative approach for repair of type II thoracoabdominal aneurysm with a clamp-and-sew technique supplemented with regional hypothermic adjuncts for renal and spinal cord protection. (A) The entire aneurysm sac is continuously exposed after proximal cross-clamp application. After completion of the proximal anastomosis, pulsatile arterial perfusion is established into the mesenteric circulation through in-line mesenteric shunting into either the celiac axis (as depicted) or the superior mesenteric artery. Thereafter, critical intercostals vessels are reconstructed (dotted line), and a single inclusion button anastomosis for reconstruction of celiac, superior mesenteric and right renal arteries is possible in the majority of cases. The left renal artery is reconstructed with a side-arm graft. (B) Regional spinal cord hypothermic protection is achieved via epidural cooling. A 4°C epidural saline infusion (arrow) is begun in anticipation of cross-clamping. Cerebrospinal fluid temperature and pressure is simultaneously monitored with a separate intrathecal catheter. See text for further details.
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Operative mortality was defined as any death within 30 days of the procedure or any death occurring during the initial hospitalization.
All patients were awakened in the operating room for an initial neurologic examination of the lower extremities. Spinal core injuries (SCI) were classified as immediate when noted as the patient awoke from anesthesia, or as delayed when patients were initially neurologically intact.
Major pulmonary complications included mechanical ventilation for more than 72 hours postoperatively, reintubation, respiratory failure requiring monitoring in the intensive care unit, pneumonia, or need for tracheostomy. Significant renal failure included postoperative serum creatinine levels exceeding 3.0 mg/dL in patients with normal baseline levels or need for dialysis.
Statistical analysis was performed using 
2 with or without Yates correction, Fisher exact, Student t, and Mann-Whitney tests as appropriate. Multivariate predictors of SCI were evaluated using logistic regression models constructed by including all variables that were significant on univariate analysis (p 
0.05). Actuarial survival analysis was performed using Kaplan-Meier life tables.
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Results
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During the study interval, 455 TAA repairs were performed. TAA extent and associated operative mortality are summarized in Figure 2. The overall operative mortality was 8.3% (elective cases, 6.8%; urgent cases, 12.9%; p = 0.06). Four intraoperative deaths occurred, two in the setting of ruptured TAA and hemorrhage, one from coagulopathic hemorrhage and one from cardiogenic shock after myocardial infarction. Variables that correlate with operative mortality are summarized in Table 2. Multivariate analysis showed that a preoperative serum creatinine level of 1.8 mg/dL or more (p = 0.005), intraoperative hypotension (p = 0.01), intraoperative transfusion requirement (p = 0.0008), postoperative SCI (p = 0.02), and postoperative renal failure (p < 0.0001) were the most powerful predictors of death in the perioperative period.
Nonfatal complications, excepting SCI, are detailed in Table 3. Renal failure occurred in 17 (17%) of 102 urgent cases and 35 (10%) of 352 elective cases (p = 0.07). SCI of any severity occurred in 21 (21%) of 102 of urgent cases and in 33 (9%) of 352 elective (p = 0.003). The overall incidence of any degree of lower extremity neurologic deficit is stratified according to TAA extent in Table 4. Overall, SCI occurred more frequently in type I/II than in III/IV (33/190 [17%] versus 22/265 [8%]; p = 0.002). However, the use of epidural cooling in type I to III TAA repairs was associated with a significant decrease in SCI in this cohort (29/211 [13.7%] versus 25/86 [29%]; p = 0.01). Multivariate analyses of predictors associated with SCI are summarized in Table 5.
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Table 5. Analysis of Variables Examined for Association With Spinal Cord Ischemia for 455 Thoracoabdominal Aneurysm Operations
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The mean duration of follow-up was 49 months (range, 0 to 215 months). The actuarial survival was 54% at 5 years, 29% at 10 years, and 21% at 15 years, as determined by Kaplan-Meier life-table analysis (Fig 3).
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Fig 3. Long-term survival after thoracoabdominal aneurysm (TAA) repair as determined by Kaplan-Meier life-table analysis.
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Comment
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Despite advances in critical care and the application of various intraoperative adjuncts, TAA repair remains a major undertaking for both surgeon and patient. Most published reports come from a few select centers that have been able to sustain excellent results with operative mortality and SCI rates in the 5% to 12% range [3, 5]. However, a recent review of the Nationwide Inpatient Sample database, a discharge database representing 20% of United States hospitals, showed that mortality after elective TAA repair was 22.3%, with higher rates in hospitals with lower procedure volumes [6]. In addition, a recent single institutional report found a 17.8% rate of perioperative mortality (10% in elective cases) and concluded that survival and good functional outcomes were significantly less common than expected [7].
A recent California state-wide study of more than 1000 TAA repairs indicated a 19% rate of overall perioperative mortality, but emphasized that the corresponding 1-year mortality overall was 31% [8]. This rather sobering 1-year mortality was linearly stratified by patient age, thus emphasizing the potential negative impact of open TAA resection even beyond the index hospitalization. In contrast, our early mortality was 8.3% for all patients (6.8% elective, 12.5% urgent), and the actuarial 5-year survival is equivalent to that reported after AAA repair [9].
SCI after TAA repair remains a major issue, especially in patients with more extensive type I/II lesions. Epidural cooling has reduced the overall incidence of SCI, and in prior reports, appeared to minimize the overall severity of the injury even when it does occur, but the problem has hardly been eliminated. Although different adjuncts have been used in individual centers, there remains no consensus.
Many surgeons advocate the use of distal aortic perfusion provided by atrial-femoral bypass during the creation of the proximal anastomosis [5]. In addition, an aggressive posture toward intercostals vessel reconstruction can be considered the "majority opinion." We demonstrated in a prior report the negative impact of intercostals vessel sacrifice in the critical T9-L1 zone [3, 4]. The use of intraoperative monitoring of evoked motor potentials as a guide to adequate spinal cord perfusion has been reported to reduce the acute paraplegia rate to 4.2% in extent I/II TAA; however, the early mortality of 13.4% in this series, possibly secondary to increased operative time and complexity spent revascularizing threatened sections of cord, may not be an appropriate compromise [10].
Although open repair of TAA can be performed with excellent results, emerging technologies in thoracic stent grafting will eventually be applied to patients with TAA. We have used hybrid procedures, which combine open arch or visceral segment rerouting procedures with stent graft repair, to extend TAA repair to high-risk patients (Fig 4). This strategy has been used with much success at both the arch and visceral segment levels in patients who were marginal candidates for open replacement. This procedure is in its infancy, however, and further studies are required to define the role of hybrid procedures in the management of TAA. This technique has been effective in the current era of thoracic stent grafting, but will likely be replaced by fenestrated and branched graft technology as it becomes available.
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Fig 4. Three-dimensional reconstruction of hybrid repair of a thoracoabdominal aneurysm. The long white arrow indicates the origin of the bifurcated aorto-superior mesenteric artery and aorto-celiac bypass graft. Short arrow points to origin of aorto-left renal artery bypass.
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In conclusion, despite consistent favorable results over a 20-year period at our center, available evidence would suggest that across a spectrum of hospitals, mortality associated with open TAA repair is excessive. Strategies to regionalize care for these patients or the further development of stent graft strategies, or both, appear to be the appropriate evolution.
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Acknowledgments
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This work was supported in part by the Harold and June Geneen Vascular Surgery Research Fund.
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References
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- Cambria RP, Brewster DC, Moncure AC, et al. Recent experience with thoracoabdominal aneurysm repair Arch Surg 1989;124:620-624.[Abstract/Free Full Text]
- Cambria RP. Thoracoabdominal aortic aneurysm repair: how I do it Cardiovasc Surg 1999;7:597-606.[Medline]
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- Davison JK, Cambria RP, Vierra DJ, Columbia MA, Coustas G. Epidural cooling for regional spinal cord hypothermia during thoracoabdominal aneurysm repair J Vasc Surg 1994;20:304-310.[Medline]
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- Rectenwald JE, Huber TS, Martin TD, et al. Functional outcome after thoracoabdominal aortic aneurysm repair J Vasc Surg 2002;35:640-671.[Medline]
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Abstract
Introduction
