Intimal tear closure by false lumen stent graft placement for postdissection thoracoabdominal aortic aneurysm

Abstract

We report a false lumen (FL) stent graft technique to close the intimal tears at the visceral segment for a postdissection thoracoabdominal aneurysm after initial thoracic endovascular aortic repair. Following endovascular abdominal aortic repair, a stent graft was deployed in the FL, overlapping the main bodies from both previous repairs just after a bare metal stent was implanted in the FL proximal to the target lesion to prevent overdilation. A reentry tear at the iliac level was intentionally preserved to protect spinal cord perfusion and develop a collateral network and will be closed in the future staged procedure.

Chronic type B aortic dissection (CTBAD) often presents with false lumen (FL) dilation due to residual tears. Less invasive techniques for postdissection thoracoabdominal aortic aneurysms (TAAAs) have been investigated with advances in thoracic and abdominal endovascular aortic repair (TEVAR and EVAR, respectively). Inflow to the FL remains when the intimal tear is located at the abdominal visceral segment even after entry closure, leading to aneurysmal enlargement. In the present report, we describe the case of a patient undergoing FL stent graft placement as a part of staged repair for a postdissection TAAA with multiple intimal tears in the visceral segment. We used this technique with the aim of minimizing the risk of spinal cord ischemia (SCI). The patient provided written informed consent for the report of his case details and imaging studies.

Case report

A 46-year-old man, with a history of noncompaction cardiomyopathy, had undergone emergency zone 3 TEVAR using a TAG stent graft (W.L. Gore & Associates, Newark, DE) for complicated type B acute aortic dissection 2 years previously. Postoperative contrast-enhanced computed tomography (CT) imaging showed the FL began from the descending aorta and extended into the left external iliac artery (EIA; Fig 1, A and B), with several residual reentry tears at the renal artery level (Fig 1, C) and a large one at the left EIA level. No reentry tears were present at the celiac or superior mesenteric artery level. The imaging studies also showed the infrarenal abdominal aortic aneurysm with three lumbar arteries originating from the true lumen (TL). Both renal arteries also originated from the TL, and they were not dissected. During periodic CT follow-up, the abdominal part of the postdissection TAAA had dilated from 39 mm to 53 mm in 2 years (Fig 1, D). To prevent future TAAA rupture, we decided to repair the TAAA. Considering his impaired cardiac function with an ejection fraction of 24%, we decided to perform additional endovascular treatment with intimal tear closure using FL stent graft placement.

Fig 1.

A, Three-dimensional reconstruction of preoperative computed tomography (CT) scan showing the false lumen (FL) extending from the descending aorta to external iliac artery. B, C, and D refer to the descending aorta, renal artery, and abdominal aortic aneurysm levels. Axial contrast-enhanced CT images at the descending aorta level (B), renal artery level with an intimal tear (C; orange arrow), and abdominal aortic aneurysm level (D). TL, True lumen.

The bilateral femoral arteries were approached with the patient under general anesthesia. First, we completed EVAR with the Excluder Aortic Extender (W.L. Gore & Associates) below the renal artery, followed by an Excluder main body (W.L. Gore & Associates) landing on bilateral common iliac arteries in the TL. This excluded the TL of the abdominal part of the TAAA (Fig 2, A and B). Coil embolization of the three lumbar arteries originating from the TL of the abdominal aorta was also performed to prevent a type II endoleak. Second, a Kumpe access catheter (Cook Medical Inc, Bloomington, IN) was used to catheterize the tear at the external iliac artery and situated in the FL. We placed a 10 × 40-mm Epic vascular self-expanding stent (Boston Scientific, Marlborough, MA) in the FL at the level of the distal end of the TAG stent graft to prevent overdilation of the FL and rupture due to the FL stent graft. Next, the intimal tears at the renal artery level were closed using an Endurant II iliac leg (catalog no. ELW1624C94; Medtronic, Dublin, Ireland) from the FL side. This stent graft was placed in the FL, overlapping the inner side of the Epic stent placed in the FL on the proximal side and the Excluder Aortic Extender placed in the TL on the peripheral side (Fig 2, C). The aortogram confirmed that the several intimal tears at the renal artery level were all closed by the FL stent graft. The retrograde angiogram from the left femoral artery sheath showed residual blood flow increasing the FL from the reentry tear at the left EIA, and some lumbar arteries originating from the FL showed contrast enhancement (Fig 2, D). His postoperative course was uneventful, with no paraplegia, and he was discharged on postoperative day 4. CT at 6 months after the procedure showed the unchanged diameter of the abdominal aorta of 52 mm and FL of 23 mm (Fig 3). The patient will be followed up with periodic CT scans every 6 months. If either the total aortic diameter or the FL diameter have enlarged even slightly, the final operation, including stent graft placement on the left EIA to cover the last reentry tear, will be performed.

Fig 2.

Intraoperative angiogram showing false lumen (FL) with contrast enhancement through an intimal tear at the visceral segment (A), Excluder main body placed in true lumen (TL; B), Epic stent placed in FL at level of distal sight of CTAG (C; orange arrow), and Endurant II iliac leg placed in FL to close intimal tears near the renal artery (C; white arrow). D, Iodine contrast-enhanced angiogram from left femoral sheath showed residual blood flow increasing the FL size, with slight contrast enhancement of the lumbar artery originating from the FL. Both renal arteries were intact because they originated from the TL.

Fig 3.

Three-dimensional reconstruction of postoperative computed tomography (CT) scan at 6 months after the procedure. B, C, and D refer to the descending aorta, renal artery, and abdominal aortic aneurysm levels. B-D, Axial contrast-enhanced computed tomography images showing unchanged diameter of the abdominal aorta and false lumen (FL). TL, True lumen.

Discussion

CTBAD often presents with FL dilation and often leads to a postdissection TAAA. A recent guideline for CTBAD reported that open surgical repair should be considered for patients with CTBAD with indications for intervention unless the comorbidities are prohibitive.¹ However, open surgery for TAAAs has a great risk of complications, including SCI and acute kidney injury. Especially for patients with low cardiac function, the risk of perioperative complications is high, with an odds ratio of 2.72.² In recent years, endovascular strategies, including FL embolization with the candy-plug technique, have been increasingly reported as good treatment options for FL dilation of CTBAD.^3,4 However, if inflow from the intimal tears is non-negligible, the FL could enlarge. In particular, intimal tears located at the visceral branches make the procedure complicated. Several endovascular techniques can be used to close reentry tears at the abdominal visceral segment. Fenestrated and branched TEVAR can cover the entire thoracoabdominal aorta while maintaining visceral artery perfusion through the fenestration.⁵ However, this method requires special customization of devices, and abrupt interruption of FL flow can cause SCI if some branches in the FL are the source of spinal cord perfusion. Some TEVAR techniques, including the chimney, periscope, and sandwich, are also available^5,6; however, these techniques have resulted in a high incidence of type I and type III endoleaks, the so-called gutter leak.⁷

The aim of placing an FL stent graft in the staged repair is to eliminate intimal tears at the visceral branch level. There are two key points in this strategy. First, we ensured we did not injure the intimal flap by placement of the FL stent graft and that the 24-mm distal size of the FL stent graft was the appropriate diameter (105%-110% of the FL diameter). Because the FL diameter decreased sharply toward the proximal side, a size mismatch was still present, although the minimal diameter (16 mm) was used on the proximal side. This carries the risk of aortic rupture due to overdilation of the FL. Therefore, a self-expandable stent was placed in advance to prevent overdilation. The 16F (5.3-mm) external diameter of the FL stent graft delivery system should be small enough to pass through the stent diameter of 10 mm without being trapped. However, the delivery system should be situated with caution when a stent is not fully dilated. Furthermore, just as for the distal overlap with the Excluder stent graft, it was necessary to stabilize the intimal flap. If radial force of the FL stent graft was applied on the intimal flap without overlapping with the Excluder stent graft in the TL, a new tear might have been created. Second, we intentionally preserved the reentry tear at the EIA and planned staged closure considering the high preoperative probability of SCI. Total elimination of the FL is planned as the final step. Closing all the tears in a single procedure prolongs the operative time, which is reported as a risk factor for SCI.^8,9 In addition, the anatomic complexity categorized this patient in a high-risk group. Staged closure has been reported to reduce the incidence of SCI compared with a single-stage procedure,^10,11 which might derive from the development of a collateral network for spinal cord perfusion. The reduction in operative time and injury at each procedure might also contribute to this advantage. Additionally, the remaining reentry tear can be used as an access site for additional FL intervention in the future, if needed.

Another advantage of FL stent graft placement is preservation of the side branches in the TL. With the TL stent graft, branches at the same level as the intimal tears or on the landing zone must be closed by the stent graft itself. In contrast, the FL stent graft covers only the branches supposed to be thrombosed after intimal tear closure. This could also positively affect a reduced risk of SCI. Because this strategy requires a long time for completion, we start the initial intervention at the early stage of postdissection TAAAs. The timing of subsequent procedures will be determined by aneurysmal progression with follow-up CT scans at least once every 6 months. Even if a reduction in the aneurysm diameter is achieved, we would proceed with the final surgery once the aneurysm has started to grow again. The future final surgery includes embolization of the lumbar arteries originating from the FL to prevent type II endoleaks and stent graft placement on the left EIA to cover the last reentry tear, preserving the internal iliac artery. Performance of this FL stent graft technique is easier when all four visceral vessels originate from the TL, as in the present case. If one of the renal arteries had originated from the FL, which often happens, open repair should be recommended. If treatment must be completed with endovascular repair in high-risk patients, a covered stent can be placed to bridge from the renal artery to the TL of the abdominal aorta through the intimal tear, followed by FL stent graft placement to cover the remaining tears. However, because of interference between the covered stent and FL stent graft, additional coiling might be required. We believe it is important to avoid complications, including SCI, to avoid impairing the less invasiveness of endovascular treatment. Although placement of stent grafts into the FL has some anatomic limitations, this intimal tear closure technique can be performed with relatively low risk and can be considered a feasible therapeutic option for postdissection TAAA cases.

Conclusions

FL stent graft placement is a useful technique to eliminate intimal tears at the visceral segment and can be a treatment option for postdissection TAAAs.