Hybrid Procedures for Thoracoabdominal Aortic Aneurysms

Hybrid Procedures for Thoracoabdominal Aortic Aneurysms Mark A. Farber, MD, and Peter F. Ford, MBBS Treatment of thoracic aortic pathology has been rapidly changing in the 5 years since US Food and Drug Administration approval of thoracic stent grafts. Although not specifically evaluated in any of the major clinical trials to date, adjunctive techniques are being increasingly used to expand the applicability of stent-graft technology to patients with more extensive thoracoabdominal aortic aneurysms and dissections. Details of procedural techniques have been delineated by several aortic specialists, resulting in a trend toward standardization of effective strategies. Despite this trend, significant variability is evident in the outcomes of reported series. The objective of this article is to analyze published reports of hybrid procedures involving complete visceral debranching of the aorta and endovascular exclusion of the thoracoabdominal aortic aneurysms. Semin Vasc Surg 22:140-144 © 2009 Elsevier Inc. All rights reserved.

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HORACOABDOMINAL AORTIC ANEURYSMS continue to represent one of the most challenging conditions faced by today’s vascular specialists. Most physicians consider these formidable disorders to represent a highly lethal vascular condition if left untreated, yet acknowledge these complex aneurysms frequently present in patients with some of the most hostile comorbidities. In some regards, management of a subset of these disorders became vastly simpler with the introduction of thoracic aortic stent grafts. Although prospective randomized trials have never been conducted, utilization of thoracic endovascular procedures to manage thoracic aortic pathologies has gained wide acceptance by those individuals managing the disease. Those who actively oppose stent-graft use are typically individuals who either do not manage the disease or do not perform endovascular aortic repairs. Although some opponents contend that this therapy is unproven, data from clinical trials as well as large case series support its use for aneurysmal pathology in the descending thoracic aorta with acceptable anatomy. This belief and approach has been widely adopted by most aortic centers in the United States. Controversy still exists, however, regarding optimal management in those with unfavorable anatomy. While stent-graft technology has been shown to significantly reduce major morbidity and mortality compared to surgical controls for descending thoracic aneurysms,1,2 its

Division of Vascular Surgery, University of North Carolina, Chapel Hill, NC. Address reprint requests to Mark A. Farber, Division of Vascular Surgery, University of North Carolina, 3025 Burnett-Womack, Chapel Hill, NC 27599. E-mail: [email protected]

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0895-7967/09/$-see front matter © 2009 Elsevier Inc. All rights reserved. doi:10.1053/j.semvascsurg.2009.07.004

expanded use for lesions involving arch and visceral vessels is still undefined. Although many authors advocate its use for arch lesions to avoid hypothermic arrest and potential complications,3 its expanded use for the visceral region remains the subject of debate at numerous national and international congresses. A review of the literature involving visceral debranching for thoracoabdominal aortic aneurysms (TAAA) and its impact on morbidity and mortality are discussed. Although improvements in the surgical treatment of thoracoabdominal aortic repairs have occurred during the preceding two decades, overall morbidity and mortality at centers of excellence may not reflect true “real-world” experience. As published by Cowan et al,4 the outcomes from Medicare patients are sobering. In their analysis of 1,542 patients treated during a 10-year period from 1988 through 1998, overall mortality was 22.3%, with a statistical improvement during the later half of the study period and at highervolume centers. Furthermore, data from the surgical control groups in two of the US clinical trials are not as impressive as those reported by centers of excellence for isolated thoracic aneurysm repair.1,2,5 Thus, major mortality and morbidity still occurs with traditional open repair, despite significant improvements in anesthesia, critical care, and surgical techniques. In an effort to reduce these complications, alternative techniques to treat patients with extensive TAAA are being investigated. Despite continued engineering efforts since the first report of endovascular thoracic aortic repair in 1994,6 branched and fenestrated designs have been slow to develop outside of a few physician-sponsored investigational device sites. Cre-

Hybrid procedures for thoracoabdominal aortic aneurysms ation of a custom-made branched or fenestrated device is technically feasible, however, turnaround times of 3 to 12 weeks may be incurred, depending on the complexity and availability of design/manufacturing teams. Patients presenting in an urgent nature and those with large TAAA may be at risk of aneurysm rupture during this construction window. While off-the-shelf devices may theoretically reduce or eliminate this wait time, their development and availability may still be years away. The percentage of patients with TAAA who will be potential candidates for off-the-shelf branched/ fenestrated devices is still unknown. In an effort to expand therapeutic options using currently available and readily accessible technology, hybrid (debranching) procedures were conceived and implemented. The perceived theoretic advantages of these procedures include reducing the negative impact of aortic cross-clamping and dual-cavity exposure, as well as reduction of visceral and renal ischemic time. After the visceral blood flow has been rerouted, endovascular exclusion with US Food and Drug Administration⫺approved devices is then undertaken (Fig 1).

Early Results It is not surprising that early reports of these procedures originated from Europe, where thoracic endografts were available several years before being approved in the United States. The St Mary’s group in London is credited with publishing the first large series on the topic, although individual case reports had been reported previously.7-9 Although recognized as a major vascular center with excellent care, their group was not able to reduce paraplegia and mortality rates to acceptable levels with traditional open repair. In selected patients, they felt that avoiding aortic cross-clamping, leftheart bypass, and single-lung ventilation had a potential advantage. In their initial report of 29 patients, overall mortality for elective or urgent procedures was 13%, with no reported cases of paraplegia. As a result of the promising outcomes reported by Black et al,7 they have continued to employ these techniques. In addition several other centers began to incorporate similar techniques that have been described in detail.10,11 The strategy of utilizing visceral debranching techniques to extend endovascular options is predicated upon minimiz-

Figure 1 Open thoracoabdominal aortic aneurysms repair with bypass grafting to visceral segment.

141 ing or eliminating certain deleterious elements of traditional open surgical repair. The major physiologic insults that are mitigated or eliminated using this strategy include aortic cross-clamping, excessive blood loss, single-lung ventilation, and partial left-heart bypass. Despite appealing conceptual elegance, debranching procedures occasionally evolve into an operative tour de force, potentially requiring an open abdominal cavity for many hours. Although early publications were met with tempered enthusiasm regarding possible reductions in overall morbidity and mortality for complex aneurysm repair, visceral debranching procedures continue to pose a formidable operative challenge. These procedures require great attention to detail and surgical expertise in order to avoid anastomotic or other technical complications. While the fundamental tenets of visceral debranching procedures have been well-elucidated, appropriate patient-selection criteria continue to remain poorly defined. It may, in fact, be the case that variations in patient selection account for substantive differences in reported procedural outcomes. Currently there is no consensus on the inclusion and exclusion criteria for debranching procedures, and diverse outcomes in published reports may represent the sequelae of heterogeneous cohorts. When evaluating articles delineating outcomes for debranching techniques, it is important to consider both the extent of aortic disease treated and the percentage of patients who have undergone antecedent aortic repair. Published series with a high percentage of type I or type IV TAAA may have different outcomes when compared to those with a high percentage of type II or type III extent aneurysms. Similarly, cohorts with a high incidence of prior aortic surgery are generally predicted to have higher morbidities. If a “two-stage” strategy is employed, optimal timing of the two stages may also represent an outcome variant. Additionally, long-term outcomes such as graft patency are currently unknown. As such, in high-risk patients it may not reduce overall complications associated with repair. Several authors have recently published their early results after application of these techniques.

Recent Publications Donas et al12 recently conducted a literature review of hybrid repair of TAAA. In his report of 13 of 27 international publications comprising 58 patients, the overall mortality and paraplegia was 10.7% and 0% for elective and urgent procedures. In addition, graft patency was 97.8% at a mean follow-up of 14.2 months. One drawback of this article is that it consists of early initial experiences with a small numbers of patients, which may introduce a bias to the results. In addition, a significant proportion of this report includes the original data from the St Mary’s publication.7 Although the mortality and paraplegia outcomes appear promising in this series, endoleaks continue to plague 19% of the patients in the follow-up period, with 10% requiring additional procedures to exclude their aneurysm. Several groups have more recently published larger cohorts that are not as positive on outcomes and results. Lee et

M.A. Farber and P.F. Ford

142 al11 detailed their experience in 17 patients, 41% of which had type IV TAAA. A large percentage of the patients had undergone previous aortic surgery; 59% had previous abdominal aortic aneurysm, and 24% had prior thoracic aneurysm repair. There were a 24% mortality rate and a 25% complication rate associated with the first stage of the operation, comparatively higher than that of patients undergoing open repair during the same time period. There was, however, a significant selection bias present, with 82% of patients considered high risk for traditional repair. Despite the lack of routine use of spinal drainage, no paraplegia or additional deaths occurred in this series, with one patient refusing to complete the second-stage procedure. Although no patient ruptured during the mean 27-day wait between procedures, several institutions attempt to perform separate procedures during the same hospitalization to avoid lost patients, incomplete repairs, and ruptures that have occurred.7,13 Lee et al11 conclude that the most compelling reason to perform this procedure is the low incidence of paraplegia because of its devastating outcome (50% mortality) within the first year. However, in the young patient (younger than 65 years), traditional open repair is preferred because of long-term durability issues.

Procedural Logistics Considerable debate has occurred as to whether the stages of the procedure should occur separately or simultaneously. Those proponents of simultaneous repair advocate for reduced risks of rupture and decreased incidence of lost patients. Those who employ the separate procedure approach

attempt to limit the magnitude of the visceral debranching procedure and its impact on spinal cord perfusion. Recently, Böckler et al13 published their results for the treatment of thoracoabdominal aneurysms and chronic dissections in 28 patients and attempted to determine if there was a difference in outcomes based on simultaneous versus staged approach. Although mortality was comparable to other studies (14%), technical success was only achieved in 89% of patients and permanent paraplegia in 11%. There was no difference with respect to paraplegia or complications when comparing simultaneous and staged groups. The number of patients in each group, however, was low. Despite this, the group advocates separate procedures because of spinal perfusion stabilization and reduced operative time and complication rates. Whether this is a direct result of the reduction of visceral and renal ischemic times is difficult to determine. Recent personal communication and discussion of unpublished data with the St Mary’s group reveals additional information about paraplegia and graft patency. Their collective experience now includes 81 consecutive patients. The more recent data reveals a similar overall mortality (11.8%), however, paraplegia has occurred in 10% of the cohort, despite being notably absent in most other studies. Graft patency was 94% at a mean follow-up of 17 months, suggesting that graft occlusion does not appear to be a significant concern. A compilation of results from the published literature (Table 1) of 182 cases reveals an overall 30-day mortality of 11.9% and an associated paraplegia risk of 6.6%. Mean follow-up for this cohort averaged 15.3 months and graft patency was excellent at 94.4%.

Table 1 Complete Hybrid Repairs for Thoracoabdominal Aortic Aneurysms First Author

Year

n

30-Day Mortality (%)

Paraplegia (%)

Follow-Up (mos)

Patency (%)

St Mary’s Flye17 Donas18 Chiesa14 Macierewicz19 Quiñones-Baldrich8 Lawrence-Brown20 Kotsis21 Agostinelli22 Iguro23 Saccani24 Khoury25 Gawenda26 Lee11 Böcker13 Zhou27 Our series Totals

Unpublished 2004 2007 2004 2000 1999 2000 2003 2002 2003 2002 2002 2006 2007 2008 2006 Unpublished

81 3 8 1 1 1 2 4 1 1 3 1 6 17 28 18 6 182

11.8* 0 12.5 0 0 0 0 25 0 0 33 0 0 24 14.3 0 16.7 11.9

10 0 0 0 0 0 0 0 0 0 0 0 0 0 16 0 0 6.6

17 14.6 21 12 22 6 36 14 6 12 4 21 12 8 22 NR 6.2 15.3

94 100 96 100 100 100 100 100 100 100 100 100 92 96 89† 95 95 94.4

Adapted from Lee WA, Brown MP, Martin TD, Seeger JM, Huber TS: Early results after staged hybrid repair of thoracoabdominal aortic aneurysms. J Am Coll Surg 205:420-431, 200711 and Donas KP, Czerny M, Guber I, Teufelsbauer H, Nanobachvili J: Hybrid openendovascular repair for thoracoabdominal aortic aneurysms: current status and level of evidence. Eur J Vasc Endovasc Surg 34:528-533, 2007.12 Abbreviation: NR, not reported. *Elective procedures only. †30-day patency.

Hybrid procedures for thoracoabdominal aortic aneurysms

143

Patient Selection

Future Directions

The value of complete visceral reconstruction may be of most benefit in those patients with recurrent visceral patch aneurysms or recurrent disease. In reports by Chiesa et al14 and Lombardi et al,15 mortality and complication rates in patients with prior aortic procedures range from 11% to 33% and 33% to 38%, respectively. Because of these reports and our own experience, we have recently avoided visceral patch reconstructions with open TAAA repairs and attempt to reconstruct the visceral section with bypasses from the mid-portion of the aortic replacement graft to avoid this complication (Figs 1 and 2). As such, any recurrent disease can be managed by simple endovascular exclusion of the proximal or distal aortic anastomosis. It has also been our approach to limit complete visceral debranching to those patients with reoperative aortic surgery or to situations in which aortic cross-clamping and renal ischemia are felt to be the limiting comorbid factors with traditional open repair, thereby only using it in a highly selected patient population. In those patients who are good surgical candidates, we either perform a traditional repair or perform a combination hybrid/fenestrated approach in those patients felt to be significantly high risk, thereby reducing operative time. By doing so, we limit the extent of the open repair by providing selective surgical revascularization to critical vessels, such as one renal and the superior mesenteric artery, and rely on fenestrated/branched approaches to maintain perfusion to the other critical vessels. While several authors have reported significant blood loss with visceral debranching,7,11 this has not been our experience unless they are being performed for recurrent aneurysmal disease or in emergent conditions, such as ruptures. It should also be noted that visceral debranching procedures are considered separate from arch debranching procedures for transverse arch aneurysms. The risk-to-benefit ratio is higher for arch aneurysms and total debranching of the great vessels appears more beneficial in this group of patients.

While the aforementioned approach has helped limit our complications, many vascular specialists consider hybrid repair as a bridge until either custom grafts or off-the-shelf configurations become available. Considered by many to be one of the leaders in the field of endovascular therapy for aortic disease, the Cleveland Clinic reported16 recently their comparative results of branched versus open repair of patients with TAAA. Because of the heterogeneity of the population, results were limited to mortality and paraplegia. With respect to these outcomes, branched treatment was similar to open repair, despite a sicker cohort of patients. While paraplegia was not significantly reduced, the extent of TAAA disease seemed to be a determining factor in the analysis of paraplegia risk. As with many initial reports, it remains to be seen whether branched total endovascular repair can be disseminated across several groups and maintain its overall positive influence on treating the disease.

Conclusion Hybrid repair of TAAA utilizing endovascular techniques after complete visceral debranching is a complex undertaking. Initial results continue to show promise, however, 30-day mortality and paraplegia rates appear to be more significant than initially appreciated. Given the moderate diversity of outcomes in reported series to date, it is difficult to establish the true morbidity of these hybrid procedures and perform a meaningful comparison between hybrid procedures and traditional open surgical repairs. Complication rates appear significant irrespective of technique used to repair these complex lesions. Patient selection and extent of aneurysmal disease may account for significant variation in patient outcomes when utilizing these techniques. Patient factors and anatomic features that predict improved surgical results for hybrid procedures remain incompletely defined. Further investigation is needed to determine the appropriate timing of the procedures and which patients will benefit most com-

Figure 2 (A) Preoperative and (B) postoperative reconstructions.

144 pared to traditional repair. Until branched and fenestrated endovascular repair become more common in the United States, these procedures will continue to have a role in appropriately selected patients.

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