Open repair of thoracoabdominal aortic aneurysms (TAAA) remains the gold standard approach for treating aortic aneurysms involving the visceral segment. This procedure has a proven track record highlighting its effectiveness, and long-term data from large series are available.^1-5 Risks of morbidity and mortality are well established. All sections of the aorta from the arch to the iliac bifurcation can be repaired using this method, and multiple techniques have been developed to preserve end-organ function while removing all of the diseased aorta, including clamp-and-sew methods, partial left heart bypass, and circulatory arrest.

Despite advances in open surgical techniques and improvements in postoperative intensive care, the risk of morbidity and mortality remains significant, especially in centers that are not specifically equipped to manage patients with this disease. In low-volume centers, mortality has been as high as 20%, but higher volume centers have reduced the risk of mortality to 5-8%^2,4,5 due not only to the surgeon's familiarity with the procedure but also to the institution's readiness to handle the postoperative care. Paraplegia and paraparesis rates depend on the extent of the aneurysm, but overall, the rate is 3-6% in most open series.^1-5 Morbidity that can be associated with the procedure is related to postoperative pain associated with the thoracotomy or thoracoabdominal incision, respiratory failure in 7%, renal failure in 5%, and wound healing problems in 4%.^1-5

Endurance through an open TAAA repair remains a demanding task for both the patients and the surgeons. Many patients have been deemed too high risk to undergo an open procedure, mainly due to advanced age or cardiopulmonary disease, and they have been relegated to medical management alone. An endovascular repair would purportedly be less invasive, have decreased respiratory complications, lower blood loss and transfusion rate, quicker recovery, and shorter length of stay, allowing higher-risk patients to be repaired.

Thoracic endovascular aneurysm repair (TEVAR) for descending thoracic aneurysms (DTA) limited to the thoracic aorta is well established and has been studied in large population databases. TEVAR offers a lower perioperative mortality compared to open surgery (6.1% vs. 7.1%, p = 0.07), which is especially beneficial for higher-risk patients. For ruptured DTA, the benefit was even greater (46% vs. 28%, p <0.0001). However, by one year, the survival benefit significantly favored open surgery (87% vs. 82%, p = 0.001), and this persisted at five-year follow-up (72% vs. 62%, p = 0.001).^6-7 While some have argued that this survival benefit was due to selection bias, comparison of propensity-matched cohorts having open repair versus TEVAR continued to show a survival benefit for open surgery across all populations.⁷

In the past, the patients' eligibility for an endovascular repair was limited by the available design of the stent grafts and their ability to maintain perfusion in the visceral segments. As technology has improved in the realms of radiologic imaging and stent graft development, a less invasive alternative has arisen for this older and higher-risk population. Advanced high-resolution computed tomography imaging has allowed for accurate three-dimensional reconstructions of the aorta with precise measurements of aortic length, diameter, tortuosity, landing zones, and branch vessel angulation. Companies manufacturing endografts have used this information to create stent grafts with fenestrations, branches, or a combination of the two to perfuse each visceral vessel. Unfortunately, each graft must be custom made to the individual patient's specific anatomy and the turn-around time for making a custom endograft is six to 12 weeks.⁸

Reports on the efficacy of fenestrated/branched thoracic endovascular aneurysm repair (f/br-TEVAR) for TAAA have shown some promise for this technique, although significant limitations remain. As expected, a gradual learning curve exists, and operative times tend to decrease with more experience. Technical success was achieved in 93-100% of cases.^9-14 In the unsuccessful cases, branch vessels were either occluded or failed to be cannulated. This is quite an acceptable number for these patients who might otherwise have been managed with medical therapy alone and progressed toward continued aortic growth and rupture.

Despite the less invasive nature of f/br-TEVAR, the morbidity and 30-day mortality of many series was somewhat disappointing and the rates of spinal cord ischemia, myocardial infarction, and renal dysfunction were not significantly reduced as might have been expected. Mortality ranged from 0-10%, which is comparable if not higher than large open series from aortic surgery centers.^9-14 The rate of paraplegia/paraparesis was also disappointingly high, ranging from 0-16.7%.^9-14 In two of the larger series, paraplegia/paraparesis was seen in 15% and 8% of patients after f/br-TEVAR despite having a population composed of Extent IV TAAA in 40% and 50% of patients, respectively,^9-10 which is the group associated with the lowest risk of spinal cord injury in the open surgery series. Renal failure requiring dialysis occurred in 0-6.7% of patients,^9-14 which is comparable to open series. Pulmonary complications were reduced compared to open series and many procedures were performed with regional rather than general anesthesia.¹³ Wound complications associated with the open procedures were eliminated, but a new set of complications were associated with f/br-TEVAR – namely, groin hematomas/seromas, iliac artery rupture, access vessel ischemia, aortic arch rupture, subclavian artery rupture, and retroperitoneal hematoma from access vessels.^9-14

Follow-up after f/br-TEVAR is currently limited with the majority of studies having a mean or median follow-up of 12-18 months, whereas open series have long-term follow-up data available. Even during early follow-up, a large number of patients treated with f/br-TEVAR had documented endoleaks despite initial successful graft placement. The incidence of endoleaks varied from 15-66.7%, and as many as 3-33.3% of patients required re-intervention.^9-14 These highly variable numbers highlight the variable follow-up and diagnosis of endoleaks. Once diagnosed, some groups are very aggressive in re-intervening, whereas others observe and intervene only if growth of the aneurysm sac is demonstrated. Type II endoleaks were most common, and these were either observed for sac growth or embolized with glue. Type I endoleaks required cuff extensions for proximal or distal sealing. Type III endoleaks at the modular components often required repeat stenting into the visceral or renal arteries to seal the modular joints. A few patients in each series had renal or visceral artery occlusion requiring open extra-anatomic bypass procedure or sacrificing a kidney. Some patients required peripheral vascular interventions with femoral artery bypass or stenting for leg ischemia. Others required multiple re-interventions for a combination of leaks, kinking, and stenoses. Interestingly, the risk for developing endoleak or branch vessel problems persisted for the duration of follow-up and occurred >24 months after the initial procedure in several patients.⁹

The currently published series on the topic are all relatively small series from specialized centers. The patients selected for f/br-TEVAR were patients who were deemed unfit for open surgery, and this appears to be a feasible option for this group that may have no open surgical option. More extensive experience and long-term follow-up is required to evaluate these devices and define the proper patient selection criteria. Perhaps more stringent patient selection will help to decrease the morbidity and mortality, although the highest-risk patients may have no other surgical option.

Table 1: Open Repair of Thoracoabdominal Aneurysms
Author, Year	Number of Patients		Extent 1 and 2			Mortality		Paraplegia and Paraparesis			Renal Failure
Svennson 1993	1,509		54.3			8.3		15.5			17.8
Safi 2003	1,004		41.6			14		3.6			NA
Coselli 2007	2,286		64.2			5		3.8			5.6
Acher 2008	637		37.9			2.7		5.5			2.6
Girardi 2015	675		48.5			5.6		2.8			5.2
Table 2: Fenestrated/Branched Thoracic Endovascular Aneurysm Repair
Author, Year		Number of Patients		Mortality	Paraplegia and Paraparesis		Renal Failure		Technical Success	Endoleak		Re-Intervention
Roselli 2007		73		5.5	2.7		1.4		93	18		29
Haulon 2009		33		9	15		9		-	15		3
Verhoeven 2009		30		6.7	16.7		3.2		93	-		6.7
Guillou 2012		89		10	7.8		6.7		96.6	21		4.2
Kitagawa 2013		30		0	0		0		100	66.7		33.3
Oikonomou 2014		31		9.6	12.9		3.2		93.5	38.7		32.3

References

1. Acher CW, Wynn MM, Mell MW, Tefera G, Hoch JR. A quantitative assessment of the impact of intercostal artery reimplantation on paralysis risk in thoracoabdominal aortic aneurysm repair. Ann Surg 2008;248:529-40.
2. Coselli JS, Bozinovski J, LeMaire SA. Open surgical repair of 2286 thoracoabdominal aortic aneurysms. Ann Thorac Surg 2007;83:S862-4; discussion S890-2.
3. Girardi LN, Shavladze N, Sedrakyan A, Neragi-Miandoab S. Safety and efficacy of retrograde cerebral perfusion as an adjunct for cerebral protection during surgery on the aortic arch. J Thorac Cardiovasc Surg 2014;148:2927-33.
4. Safi HJ, Miller CC 3rd, Huynh TT, Estrera AL, Porat EE, Winnerkvist AN, Allen BS, Hassoun HT, Moore FA. Distal aortic perfusion and cerebrospinal fluid drainage for thoracoabdominal and descending thoracic aortic repair: ten years of organ protection. Ann Surg 2003;238:372-80; discussion 380-1.
5. Svensson LG, Crawford ES, Hess KR, Coselli JS, Safi HJ. Experience with 1509 patients undergoing thoracoabdominal aortic operations. J Vasc Surg 1993;17:357-68; discussion 368-70.
6. Conrad MF, Ergul EA, Patel VI, Paruchuri V, Kwolek CJ, Cambria RP. Management of diseases of the descending thoracic aorta in the endovascular era: a Medicare population study. Ann Surg 2010;252:603-10.
7. Goodney PP, Travis L, Lucas FL, Fillinger MF, Goodman DC, Cronenwett JL, Stone DH. Survival after open versus endovascular thoracic aortic aneurysm repair in an observational study of the Medicare population. Circulation 2011;124:2661-9.
8. Greenberg RK, Qureshi M. Fenestrated and branched devices in the pipeline. J Vasc Surg 2010;52(4 Suppl):15S-21S.
9. Guillou M, Bianchini A, Sobocinski J, et al. Endovascular treatment of thoracoabdominal aortic aneurysms. J Vasc Surg 2012;56:65-73.
10. Haulon S, D'Elia P, O'Brien N, Sobocinski J, Perrot C, Lerussi G, Koussa M, Azzaoui R. Endovascular repair of thoracoabdominal aortic aneurysms. Eur J Vasc Endovasc Surg 2010;39:171-8.
11. Kitagawa A, Greenberg RK, Eagleton MJ, Mastracci TM, Roselli EE. Fenestrated and branched endovascular aortic repair for chronic type B aortic dissection with thoracoabdominal aneurysms. J Vasc Surg 2013;58:625-34.
12. Oikonomou K, Kopp R, Katsargyris A, Pfister K, Verhoeven EL, Kasprzak P. Outcomes of fenestrated/branched endografting in post-dissection thoracoabdominal aortic aneurysms. Eur J Vasc Endovasc Surg 2014;48:641-8.
13. Roselli EE, Greenberg RK, Pfaff K, Francis C, Svensson LG, Lytle BW. Endovascular treatment of thoracoabdominal aortic aneurysms. J Thorac Cardiovasc Surg 2007;133:1474-82.
14. Verhoeven EL, Tielliu IF, Bos WT, Zeebregts CJ. Present and future of branched stent grafts in thoraco-abdominal aortic aneurysm repair: a single-centre experience. Eur J Vasc Endovasc Surg 2009;38:155-61.

Keywords: Anesthesia, General, Aorta, Aortic Aneurysm, Aortic Aneurysm, Thoracic, Aortic Rupture, Constriction, Pathologic, Endoleak, Endovascular Procedures, Femoral Artery, Follow-Up Studies, Groin, Heart Bypass, Left, Hematoma, Iliac Artery, Intensive Care, Myocardial Infarction, Pain, Postoperative, Paraparesis, Paraplegia, Patient Selection, Postoperative Care, Renal Artery, Renal Dialysis, Renal Insufficiency, Respiratory Insufficiency, Selection Bias, Seroma, Spinal Cord Injuries, Spinal Cord Ischemia, Stents, Subclavian Artery, Surgeons, Thoracotomy, Tomography, Wound Healing

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