Introduction
Acute type A aortic dissection remains the most common of all aortic catastrophes
and is associated with significant morbidity and mortality[1], and the time-honored dictum is that urgent surgery should be undertaken[2]. In 1983, Borst introduced the elephant trunk procedure[3], followed by a variety of modifications[4]
[5]
[6], with improved clinical outcomes over the years[7]
[8]
[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[12], which has produced satisfactory early and long-term results[13]
[14]
[15]
[16]
[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[18]. In this paper, we briefly describe Sun's procedure with regard to operative techniques,
surgical indications, and clinical outcomes. A video ([Video 1]) shows the technical details for better understanding of the Sun's procedure.
Surgical Techniques
Sun's procedure encompasses several technical details in terms of cannulation, cardiopulmonary
bypass, cerebral protection, and surgical skills[12]
[13]
[14]
[15]
[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[12]. 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.
Figure 1. The stented elephant trunk, Cronus®, before (A) and after (B) implantation.
Figure 2. Schema of Sun's procedure. (A) Insertion of the stented elephant trunk into the descending
aorta; (B) Deployment of the stented elephant trunk in the descending aorta; (C) Anastomosis
of four-branched graft distally to stented elephant trunk and perfusion of descending
aorta restarted; the suture line should include the endograft, native aorta, and tetrafurcated
graft, joining all three layers firmly together; (D) Reconstruction of left common
carotid artery, SCP continued through RAA and left common carotid artery, and rewarming
begins; (E) Anastomosis of four-branched graft proximally to ascending aorta and perfusion
to the heart resumed; (F) Reconstruction of the left subclavian artery; (G) Reconstruction
of the innominate artery.
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.
Operative Indications
As our team has gained vast experience since its introduction, the indications of
Sun's procedure have evolved considerably[12]
[13]
[14]
[15]
[16]
[17]
[19]
[20]
[21]
[22]
[23]
[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[17].
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]
[13]
[14]
[15]
[16]
[17]
[19]
[20]
[21]
[22]
[23]
[24]:
-
type A dissections with the primary entry locating in the arch and descending aorta
-
type A dissections severely involving the arch vessels
-
type A dissections with extensive intimal intussusception
-
Marfan syndrome complicated with type A dissection
-
thoracic aortic aneurysms involving the ascending aorta, arch, and descending aorta
-
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.
Clinical Outcomes
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[25]. Complete thrombus formation around the stented graft is observed in 93% of patients,
extending to the diaphragmatic level in 70%[16].
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”[16].
