A graft inversion technique for retrograde type A aortic dissection after thoracic endovascular repair for type B aortic dissection

Dake [1] and Nienaber [2] first applied thoracic endovascular aortic repair (TEVAR) for thoracic aortic disease in 1999; this technique has since been increasingly used as a safe and less-invasive treatment option for patients with Stanford type B aortic dissection (TBAD). However, TEVAR may lead to some potentially fatal complications. One of the most serious complications is retrograde type A aortic dissection (RTAD), which has a low incidence but a high mortality rate.

In the process of total arch replacement for type A aortic dissection, sometimes distal anastomosis is difficult, and bleeding from it is a tricky problem because of limited surgical exposure. Therefore, surgeons are seeking better technique for distal anastomosis. Koyu Tanaka et al. [3] modified a new procedure, graft inversion technique, which was applied to distal anastomosis in a total arch replacement for thoracic aortic aneurysm. In this paper, we report this technique which first applied to the treatment of RTAD after TEVAR, and summarized our experiences in surgical treatment for this serious complication.

Twelve patients who suffered RTAD after TEVAR at our center. The corresponding institutional incidence of RTAD was 2.1% (12 of 571). In 16 of the 20 patients, we observed new entry tears located at the distal convexity of the aortic arch near the bare metal springs at the proximal ends of the stent grafts when we explored the aortic arch in the operation. In the remaining four cases, the tears were located far from the bare metal springs, which excludes the stent graft as the cause.

Eighteen survivors completed follow-up for a mean period of 25.8 ± 18.2 months. No patient died during the follow-up period, and no recurrences of aortic disease required reoperation. All patients recovered well and achieved satisfactory results and an improved quality of life.

TEVAR has become the first-choice therapy for patients with uncomplicated TBAD. However, RTAD, a catastrophic complication of this interventional procedure, has been extensively described. Although the incidence of RTAD was reported to be 1.3–4% [4, 5], the overall mortality rate was as high as 33.6–57% [6–9].

Given the evidence reported in the literature, RTAD may be associated with device which damage to the aortic wall during or after TEVAR, or as the outcome of natural progression of disease. The main possible risk factors for RTAD after TEVAR are as follows. (1) Direct injury occurs during the intervention. Aortic dissection alters the original shape of the aorta and causes intimal fragility, the resulting anatomic abnormality can trigger intimal damage in the easily injured aortic wall during guide wire manipulation, stent graft deployment, and balloon dilation. Subtle cardiac cycle–related movement of the semirigid stent graft also may cause RTAD during TEVAR. (2) The stent graft can be excessively oversized. According to international consensus, the degree of oversizing in a case of aortic dissection should be 15–20% to provide sufficient radial force to reduce the incidence of postoperative complications such as aneurysm neck dilatation, type I endoleak, and device migration [10–12]. However, Canaud et al. [13] found that each 1% increase in endograft oversizing beyond 9% increased the risk of RTAD by 14%, as the excessive radial force caused by aggressive oversizing could easily damage the fragile aortic wall. Lei et al. [14] observed that patients in whom stent graft oversizing remained at or below 5% experienced a lower incidence of RTAD with no significant increase in the stent migration and endoleak rates. Endovascular treatment for aortic dissection aims to plug the intimal tear, whereas the endograft provides only the necessary radial force to ensure complete attachment to the aortic wall. Therefore, excessive oversizing should be avoided, and an oversizing rate of 5% or less may be a suitable option for TEVAR of type B dissection. (3) Pathological changes in the aortic wall itself also comprise a high risk factor for RTAD after TEVAR. For example, patients with connective tissue disorders such as Marfan syndrome have a significantly increased incidence of RTAD. In a series of reoperations for complications of endovascular aortic repair, Spiliotopoulos and Colleagues [15] reported that 16 of 45 patients with a previous thoracic endograft had a connective tissue disorder (14 Marfan syndrome, 2 Loeys–Dietz syndrome), and all 16 developed aortic dissection. Accordingly, endovascular stent grafts should not be used routinely in patients with connective tissue disorders [16]. (4) A proximal landing zone diameter greater than 40 mm was also associated with an increased risk of RTAD [17]. (5) The timing of RTAD may be a factor because acute dissection and fragility appear to have a correlation with a higher incidence of RTAD after TEVAR [6].

Given the high mortality rate associated with RTAD, open surgery is necessary. In contrast to patients with a primary type A aortic dissection, the aortic arch requires exploration and resolution in patients with RTAD, and total arch replacement must be performed under deep hypothermic circulatory arrest. Therefore, great care should be taken to protect the brain and spinal cord. However, this operation is simultaneously complicated by the presence of previous endovascular stent grafts in the aortic cavity. Researchers have reported various methods addressing these previous grafts. (1) The previous endovascular stent grafts may be left in place, and the 4-branched prosthetic graft can be directly anastomosed to the aortic wall. (2) The previous endovascular stent grafts can be removed completely. (3) The bare waved wire of the endovascular stent graft proximal edge can be trimmed, and distal anastomosis can then be completed. In our 20 patients, we left the previous endovascular stent grafts in place to prevent a new initial tear in the fragile aortic wall during removal. However, we did trim the bare waved wires of the graft proximal edges.

We note that direct anastomosis between an artificial blood vessel and a distal aorta containing stent grafts is unreliable and can easily lead to anastomotic bleeding. Therefore, we deployed an elephant trunk into the descending aorta (stent-in-stent) along with the proximal ends of the stent graft and aortic wall, which were sewn together to a 4-branched prosthetic graft. This procedure has yielded satisfactory results. However, bleeding at the distal anastomosis of the aortic arch is a main risk of this type of operation. The aortic wall lesion receives limited surgical exposure and is thin, fragile, and easily torn. Moreover, once distal anastomotic bleeding occurs, it is difficult to perform hemostasis, and internal drainage may be ineffective. Although the stent-in-stent procedure supports the suture and can significantly reduce the incidence of anastomotic bleeding, it also has some inevitable shortcomings, as follows. (1) stenosis of the lumen, especially in patients with primitive lumen stenosis, results in reduced effective blood flow and ischemia of the lower half of the body. (2) Thrombosis at the distal end of elephant trunk stent causes embolism. (3) Distortion, folding, and collapse of the stent vessels can lead to hemolysis and distal dysuria.

To address the limitations of the stent-in-stent procedure, we made a technical improvement based on a graft inversion technique which was first applied to distal anastomosis in a total arch replacement for thoracic aortic aneurysm by Koyu Tanaka et al. [3]. We first applied this improvement to the treatment of RTAD. Our experience has demonstrated the advantage of our graft inversion technique for the treatment of this serious complication. This technique simplifies the operative procedure while allowing anastomosis to be performed under good surgical exposure. Our improved procedure also reduces the duration of CPB time, and circulatory arrest time and does not require graft-to-graft anastomosis. Moreover, the “sandwich” suture is firm and can be used to compress the aortic wall after the inverted graft is pulled out, thus reducing the risk of anastomotic bleeding. Finally, our procedure avoids the previous issue involving the difficulty of suturing endovascular stent grafts to vascular grafts. We further note that with this procedure, there are no reduction in the vessel lumen, compared with elephant trunk stent implantation, and no elephant trunk stent-related complications.

Awareness of RTAD should be heightened after TEVAR. The graft inversion anastomosis technique can enable a secure distal anastomosis under good surgical exposure, resulting in reduced durations of CPB, and circulatory arrest for RTAD after TEVAR. Surgical treatment could be is a safe alternative for treatment of this patients.