Endovascular Exclusion of a Thoracoabdominal Aortic Aneurysm after Retrograde Visceral Artery Revascularization

Abstract

Historically, open surgical repair of thoracoabdominal aortic aneurysms has been associated with high morbidity and mortality rates. Furthermore, endovascular exclusion alone can restrict blood flow to visceral arteries. We report a case of thoracoabdominal aortic aneurysm that was repaired using a hybrid approach: surgery followed by an endovascular procedure. A 53-year-old woman was admitted to our hospital for endovascular exclusion of a thoracoabdominal aortic aneurysm that included the superior mesenteric artery and the celiac artery. Aorto–mesenteric and aorto–celiac artery bypass grafting was performed to create a landing zone for subsequent endovascular exclusion of the aneurysm, which was completed successfully 6 weeks after the bypass procedure.

For thoracoabdominal aortic aneurysms that extend beyond the superior mesenteric artery and the celiac or renal arteries, a hybrid approach, consisting of limited surgical treatment followed by endovascular exclusion of the aneurysm, may yield optimal results in selected patients with serious preoperative comorbidities.

Historically, open surgical repair of thoracoabdominal aortic aneurysms (TAAAs) has been associated with high morbidity and mortality rates. Only during the last 2 decades has the risk of complications been greatly decreased by improved treatment techniques and better knowledge of this complex disease. Despite these improvements, open surgical repair of TAAAs continues to be a complex and extensive procedure that is performed safely only at specialized centers.

During the past 10 years, endovascular exclusion of abdominal aortic aneurysms has become an accepted minimally invasive alternative to surgical repair.¹ This success has spurred investigators at several centers to attempt endovascular exclusion of descending thoracic aortic aneurysms (DTAAs).^2,3 However, this technique requires an adequate landing zone for graft placement. If the DTAA includes visceral arteries, the aneurysm becomes a TAAA. The endograft will subsequently cover these arteries and compromise blood flow to abdominal organs.

For these reasons, some investigators are exploring a 3rd option for treating selected TAAA patients: open revascularization of the visceral arteries to provide a suitable landing zone for subsequent endovascular graft placement. This hybrid technique would permit complete endovascular exclusion of the TAAA without compromising blood flow to the superior mesenteric artery (SMA) or the celiac artery. We present a case in which endovascular exclusion of a TAAA was preceded by aorto–SMA and aorto–celiac artery bypass grafting.

Case Report

History

In November 2003, a 53-year-old woman was admitted to our institution for endovascular exclusion of a Crawford type I TAAA,⁴ which had been discovered incidentally on a recent computed tomographic scan while she was being treated for pneumonia. The aneurysm extended beyond the SMA and the celiac artery to the suprarenal region of the aorta. The patient had a complicated medical history that included chronic obstructive pulmonary disease, congestive heart failure, alcohol abuse leading to liver cirrhosis, splenomegaly with consequent thrombocytopenia and anemia (manifesting as multiple gastrointestinal hemorrhages), and thrombosis and multiple varicosities of the portal vein. Nine years earlier, the patient had undergone aortic valve replacement. Magnetic resonance angiography performed 2 months before the current admission showed a TAAA with a maximum diameter of 5.9 cm (Fig. 1) that was amenable to endovascular exclusion.

Fig. 1 Three-dimensional magnetic resonance angiogram shows aneurysmal dilatation in the distal descending thoracic and upper abdominal aorta. The diameter of the aneurysm was 5.9 cm at its widest point and 2.8 cm at the superior mesenteric artery.

On admission to our hospital, the patient underwent catheterization and repeat contrast aortography. The original treatment plan consisted of endovascular exclusion of the DTAA. However, angiography revealed that the aneurysm was extensive (Fig. 2) and included the SMA and the celiac artery. Therefore, the endoluminal exclusion was not undertaken: the distal landing zone for graft placement was beyond the SMA and the celiac artery; positioning the graft more caudally would have occluded these arteries, causing ischemia in the abdominal organs. We decided to perform initial aorto–SMA and aorto–celiac artery bypasses in order to create a suitable landing zone for later endoluminal exclusion of the TAAA. The patient was transferred directly from the catheterization laboratory to the operating room.

Fig. 2 Angiogram of the thoracoabdominal aortic aneurysm shows involvement of the superior mesenteric and celiac arteries (arrows).

Surgical Technique

The aorta was approached retroperitoneally via an oblique left laparotomy, and the left kidney, spleen, and intestines were mobilized medially. Tissue dissection was extremely demanding because of the splenomegaly, ascites, and numerous varicosities. The aorta, SMA, and celiac artery were exposed, and heparin (1 mg/kg) was given. A partial occlusion clamp was placed on the infrarenal aorta. A 14- × 17-mm bifurcated graft (Hemashield Gold™, Boston Scientific; Natick, Mass) was anastomosed to the aorta in end-to-side fashion. The graft was clamped, and the aortic clamp was released. The celiac artery was clamped proximally and distally and then divided. The celiac stump of the aorta was oversewn, and an end-to-end anastomosis was created between the celiac artery and the graft limb with a 5-0 running polypropylene suture. The graft was then de-aired and the clamp released. The 2nd limb of the bifurcated graft was then sewn to the distal SMA graft in the same fashion. On completion of the reconstruction, hemostasis was achieved. The peripheral pulses were excellent, and no ischemic changes were evident. The effects of heparin were reversed with protamine, and the laparotomy was closed in multilayer fashion. The patient recovered uneventfully and was discharged from the hospital on postoperative day 10.

Six weeks after surgery, as scheduled, the patient was readmitted for endovascular exclusion of the TAAA. An angiogram performed before the exclusion showed patent aorto–SMA and aorto–celiac artery bypass grafts (Fig. 3). The proximal landing zone was at the T4/T5 level, and the distal landing zone was just above the origin of the renal arteries. The aneurysm was excluded with one 32-mm and one 34-mm stent-graft (Talent™, Medtronic, Inc.; Minneapolis, Minn) with local anesthesia. A cerebrospinal-fluid drain was placed to minimize the risk of paraplegia. Aortography, performed in the catheterization laboratory immediately after the procedure, showed successful exclusion of the aneurysm without endoleaks (Fig. 4). No clinical signs of spinal-cord or abdominal ischemia were present. The patient had an uneventful postoperative course and was discharged from the hospital on the day after the procedure.

Fig. 3 Angiogram obtained 6 weeks after surgery and immediately before endovascular exclusion of the thoracoabdominal aortic aneurysm shows patent aorto–SMA and aorto–celiac bypass grafts. The arrow indicates the 14- × 17-mm bifurcated graft.

Fig. 4 Post-exclusion angiogram shows exclusion of the aneurysm with stents.

Discussion

During the past 2 decades, there has been a significant reduction in the mortality and morbidity rates associated with open surgical repair of TAAAs.^5–7 However, surgical repair of type I and type II TAAAs is extensive and complex. As a result, perioperative mortality and morbidity rates remain high because of severe cardiac stress and diminished organ perfusion.⁸ If severe preoperative comorbidities are present, as in our patient, conventional surgical repair poses an unacceptably high risk of various adverse events. In such high-risk patients with extensive TAAAs, lung dysfunction occurs in up to 50%, with prolonged respiratory support in up to 10%,⁹ associated mortality rates as high as 40%, and the possibility of visceral end-organ dysfunction.¹⁰ However, these risks can be lowered by using the combined approach. In particular, a limited, 2-stage surgical procedure involving revascularization of visceral branches followed by endoluminal exclusion of the TAAA may yield better results. In one of the few published articles on endovascular exclusion of TAAA, Dake and associates¹¹ reported that 37% of their patients with DTAAs were suitable for endovascular stenting.

The precise positioning of fenestrated endovascular grafts on the orifices of visceral vessels has been reported,¹² but this approach may result in eventual migration of the endostent. Strut placement into the orifice might circumvent this problem and secure the graft, but this goal is hard to achieve in patients with large TAAAs and abundant thrombus in the aneurysmal sac.

When a patient is considered for endovascular exclusion of a TAAA, the proposed proximal and distal landing zones must be carefully evaluated. If they are inadequate, the patient may have postoperative endoleakage, graft migration, or obstruction of important aortic branches (the arteria radicularis magna, intercostal branches, SMA, celiac artery, or renal arteries). Occlusion of the arteria radicularis magna can cause spinal-cord ischemia with subsequent paraplegia.¹³ The literature contains reports of retrograde visceral revascularization with use of less invasive surgical access through sites that provide an improved landing zone.^13,14

In our patient, the TAAA extended to just above the renal arteries and had a diameter of 2.8 cm, so the aorta was considered to have a good landing zone. Because an angiogram obtained a few months earlier had shown a DTAA that was extensive but did not go beyond the supraceliac aorta, the patient was taken to the catheterization laboratory for planned endoluminal exclusion with a landing zone above the celiac artery. However, a new angiogram made it immediately apparent that this strategy was not feasible. The TAAA had expanded, making extensive surgical repair too risky. Therefore, the hybrid approach was recommended, with 1st-stage surgical retrograde visceral revascularization followed by 2nd-stage endovascular exclusion of the TAAA after a recovery interval. The patient was taken from the catheterization laboratory to the operating room, where she underwent aorto–SMA and aorto–celiac artery end-to-end anastomoses via a retroperitoneal approach. Despite the patient's complex medical history, the procedure was completed without incident. Six weeks later, after completely recovering from the initial procedure, the patient was readmitted and had an uneventful endovascular repair with the aid of local anesthesia. Such hybrid procedures may be performed in either 1 or 2 stages, depending on the extent of the TAAA, the expected duration of the procedure, and the preferences of the individual surgeon or institution.¹⁵

Conclusion

For TAAAs that extend beyond the SMA and the celiac or renal arteries, a hybrid approach, consisting of limited surgical treatment followed by later endovascular exclusion of the TAAA, may yield optimal results in selected patients with serious preoperative comorbidities.

Acknowledgment

We are grateful to Stephen N. Palmer, PhD, ELS, for his editorial support.