Acute type A aortic dissection remains the most common of all aortic catastrophes and is associated with significant morbidity and mortality , and the time-honored dictum is that urgent surgery should be undertaken . In 1983, Borst introduced the elephant trunk procedure , followed by a variety of modifications [4–6], with improved clinical outcomes over the years [7–9]. Recently, endovascular placement of stent grafts and hybrid repair have also emerged as new treatment options [10,11]. An ideal therapy should be able to replace the dissected aortic segment as long as possible and obliterate the false lumen, which is essential to minimizing operative risks and avoiding or reducing the need for reinterventions.
In our practice, we have been trying to find a new treatment option that integrates the advantages of open surgical and endovascular repairs. In 2002, the senior author (L.Z.S.), then the chief of Aortic Surgery in Fu Wai Hospital, designed a new stented graft and proposed a modified technique of total arch replacement using a four-branched graft with implantation of this stented elephant trunk as a treatment for type A aortic dissection , which has produced satisfactory early and long-term results [13–17]. Owing to its ingenious design, widespread usage, and excellent outcomes, this technique was named after Dr. Sun by domestic and international colleagues in 2008, hence the term “Sun's procedure,” i.e., total arch replacement using a tetrafurcate graft with stented elephant trunk implantation . In this paper, we briefly describe Sun's procedure with regard to operative techniques, surgical indications, and clinical outcomes. A video showing the technical details can be accessed at http://dx.doi.org/10.12945/j.aorta.2013.13.015.vid.01, for better understanding of the Sun's procedure.
Sun's procedure encompasses several technical details in terms of cannulation, cardiopulmonary bypass, cerebral protection, and surgical skills [12–16]. It is performed via a median sternotomy under total cardiopulmonary bypass (CPB) and selective cerebral perfusion (SCP) with cannulation of the right axillary artery (RAA). The arterial line is bifurcated for perfusing the brain through RAA and the descending, abdominal aorta and lower extremities through one branch of the tetrafurcate graft . If indicated, root procedures are finished during cooling. Circulatory arrest is instituted as the nasopharyngeal temperature reaches 25°C. After the arch vessels are cross-clamped, antegrade SCP through RAA is started. The ascending aorta and transverse arch are opened, and the three arch vessels are transected at their origins from the arch. A stent endograft (Cronus®, Shanghai MicroPort Medical, China) (Fig. 1) is inserted into the true lumen of the descending aorta and deployed to compress the false lumen and, most importantly, to enlarge the true lumen. Then the stented endograft is anastomosed to a four-branched graft (Maquet Cardiovascular, Wayne, NJ) end-to-end. All anastomoses are completed with continuous 4–0 prolene suture without pledgets. The suture line should include the endograft, the native aorta, and the tetrafurcated graft so that all these structures are joined firmly together (Fig. 2). When the distal anastomosis is completed, perfusion of the lower body is resumed through one branch of the tetrafurcate graft, and the CPB flow is gradually returned to 2.0–2.4 L/m2/min.
To minimize the time of cerebral and cardiac ischemia, the left common carotid artery is reconstructed first. On completion of anastomosis, rewarming begins, and SCP is continued through the RAA and left common carotid artery. Then, continuity between the tetrafurcate graft and the distal ascending aorta is established. The ascending aorta is declamped and heart beat returns. Finally, the left subclavian and innominate arteries are, in turn, anastomosed to the four-branched graft end-to-end (Fig. 2).
Difficulties may occur during the dissection and immobilization of the left subclavian artery. Great caution must be taken when suturing the distal anastomosis, because bleeding at this site may be very difficult to control afterward.
The core technique of Sun's procedure lies in its unique stented graft, which has the following advantages. First, it can be deployed very quickly, often within seconds, which decreases the technical difficulty and makes the implantation easier, compared with delivery in endovascular and other open repairs. Second, this stented endograft has an extra centimeter of attached regular vascular graft, proximally and distally, to which a conventional hand-sewn anastomosis can be performed. This minimizes the risk of proximal endoleak, eliminates residual dissections in and beyond the arch, and facilitates manipulations in second-stage operations. Third, the stent graft implanted in the descending aorta is 10–12 cm in length. It is strong enough to compress the false lumen and obliterate the intimal tear in the arch and proximal descending aorta, as is the case in the majority of type A dissections. Implantation of this elephant trunk is not associated with paraplegia or malperfusion syndromes and promotes false lumen thrombosis for the length of the stent graft and thrombosis of the entire thoracic aortic false lumen. This may obviate the necessity for surgical reintervention in a substantial proportion of these problematic patients. Finally, with inherently high mechanical strength and long-term durability, this stent graft can tolerate the forces of clamping and all manipulations during second-stage operations very well.
As our team has gained vast experience since its introduction, the indications of Sun's procedure have evolved considerably [12–17,19–24]. This, in part, may be ascribed to an algorithm dictating the surgical strategies based on our subcategorization of the Stanford system that divides type A dissections into subtypes according to the aortic root diameter, degree of aortic insufficiency, competency of the sinotubular junction, and the dissection process in the arch and beyond .
In our practice, Sun's procedure is chiefly indicated in patients with extensive dilating aortic pathologies (aneurysm and dissection) affecting the ascending aorta, aortic arch, descending aorta, and beyond. Listed below are the most common indications [12–17,19–24]:
(1) type A dissections with the primary entry locating in the arch and descending aorta
(2) type A dissections severely involving the arch vessels
(3) type A dissections with extensive intimal intussusception
(4) Marfan syndrome complicated with type A dissection
(5) thoracic aortic aneurysms involving the ascending aorta, arch, and descending aorta
(6) some type B dissections, such as those involving the arch, or with concomitant cardiac disease requiring surgical treatment; and complications of endovascular repair for type B dissections, including retrograde type A dissection, endoleak, etc.
As of January 2013, our team has performed more than 1,000 cases of Sun's procedure, with an in-hospital mortality rate of 4.6% (6% in acute cases versus 2% in chronic cases) and an incidence of second-stage operation of 4% (most seen in Marfan patients). This is one of the lowest recorded in the literature, three- to four-fold lower than most contemporary reports . Complete thrombus formation around the stented graft is observed in 93% of patients, extending to the diaphragmatic level in 70% .
At present, nearly 8,000 patients in China have received Sun's procedure as a treatment of aortic dissection or aneurysm (Z.H. Miao, pers. comm., e-mail on February 19, 2013). Cardiac surgeons in South American countries, including Argentina, Brazil, Chile, Ecuador, Uruguay, and Venezuela have successfully treated nearly 200 patients with this procedure. Since 2004, our team has trained over 600 Chinese physicians on Sun's procedure, and spread this technique to more than 70 cardiac centers across China. Between 2009 and 2012, four workshops on Sun's procedure were successfully launched for 117 South American colleagues engaged in the care of patients with aortic disease. Now Sun's procedure is gaining wider acknowledgment in international cardiac surgical community, and “may become the next standard treatment in patients with type A aortic dissection involving repair of the aortic arch” .