a thoracoabdominal aortic aneurysm ( taaa ) is characterized by enlargement of the aortic segment at the diaphragmatic crura and extends for variable distance proximally and/or distally from this point .
historically , open surgical repair of taaas has involved greater operative risk than repairs of aneurysms in other aortic segments .
the main sources of morbidity during operative repair of taaas are multiorgan failure , paraplegia and respiratory , cardiac or renal complications .
experienced surgical centers now report lower mortality and morbidity rates for taaa repair than they once did , largely because of the use of adjuncts to prevent end - organ ischemia .
the recent introduction of endovascular techniques may extend the indications of taaa repair to high - risk patients , whose only alternative is now represented by the best medical therapy .
conventional treatment of taaas consists of graft replacement with reattachment of the main aortic branches . a multimodal approach
is currently used to reduce the trauma of surgery by maximizing organ protection . the surgical technique used , as the extension of the aneurysm , has a significant impact on the outcome of the procedure .
thoracoabdominal incision and aortic exposure the patient is positioned with a beanbag in right lateral decubitus ( shoulders 60 , pelvis 30 ) .
the upper portion of the thoracoabdominal incision is made through the 6th intercostal space ; anterolaterally , the incision curves gently as it crosses the costal margin , reducing the risk of tissue necrosis .
the pleural space is entered after single right - lung ventilation is initiated ( figure 1 ) .
paralysis of the left hemidiaphragm by its radial division to the aortic hiatus would contribute significantly to postoperative respiratory failure , hence after thoracoabdominal incision , a circumferential section of the diaphragm is routinely carried out , sparing the phrenic center . under favorable anatomic conditions ,
a limited phrenotomy is carried out to preserve the tendinous center of the diaphragm ; this has been shown to reduce respiratory weaning time .
the upper abdominal aortic segment is exposed via a transperitoneal approach ; the retroperitoneum is entered lateral to the left colon , and medial visceral rotation is performed so that the left colon , the spleen and the left kidney can be retracted anteriorly and to the right .
transperitoneal approach allows direct view of the abdominal organs to evaluate the efficacy of revascularization at the end of aortic repair .
left heart bypass ( lhb ) cross - clamping of the descending thoracic aorta leads to several hemodynamic disturbances , including severe afterload increase and organ ischemia .
the rationale of lhb is providing flow to the spinal cord , viscera and kidneys during the aortic cross - clamp period together with the reduction of proximal hypertension and afterload to the heart . in preparation for lhb and aortic clamping , intravenous heparin ( 1 mg / kg )
is administered with a target act ( activated clotting time ) of 220 - 270 seconds .
proximal descending thoracic aorta , left atrium or pulmonary vein are usually cannulated for arterial blood drain that is reinfused through a centrifugal pump ( biomedicus ) into the subdiafragmatic aorta or the common left femoral artery .
flow is initially low ( 500 ml / min ) to avoid retrograde embolization and then increased after aortic clamping to a mean distal aortic pressure of about 70 mmhg , a value that is usually achieved using a flow between 1500 and 2500 ml / min .
y  bifurcation is connected to the circuit and is provided with two occlusion / perfusion catheters for selective perfusion of visceral vessels ( figure 2 ) . left heart bypass and renal perfusion catheters .
once the proximal aspect of the taaa is isolated between clamps the descending thoracic aorta is transected and separated from the esophagus ( figure 3 ) .
the proximal end of the graft is sutured to the descending thoracic aorta using a 2/0 monofilament polypropylene suture in a running fashion .
the clamp is then removed and reapplied onto the abdominal aorta above the celiac axis ( sequential cross - clamping ) .
reimplantation of intercostal arteries to the aortic graft plays a critical role in spinal cord protection .
critical patent segmental arteries from t7 to l2 are selectively reattached to the graft by means of aortic patch or graft interposition .
the distal clamp is moved onto the distal abdominal aorta below the renal arteries and the upper abdominal aortic aneurysm is opened .
visceral hematic perfusion is then maintained by the pump with occlusion / perfusion catheters ( 9 fr ) inserted selectively into the celiac trunk and the superior mesenteric artery ( 400 ml / min ) .
selective perfusion of renal arteries is performed with a cold crystalloid solution ( ringer 4c + mannitol 18% 70 ml , 6-methylprednisolone 500 mg in 500 ml ) . for visceral arteries reimplantation
, a side cut is tailored in the graft and the celiac trunk , superior mesenteric artery and renal arteries are reattached by means of a carrel patch .
this technique has been performed in 82.3% of the patients in our series . in 33.1% of the cases treated by carrel patch
the left renal artery has been separately reattached to the graft in a direct fashion or by graft interposition . when the relative distance of the visceral arteries would have required a large carrel patch ,
a branched graft can be successfully used ( vascutek gelweave - coselli thoracoabdominal graft ) ( figure 4 ) .  
type ii taaa repair : aortic graft replacement and visceral vessels reattachment by means of carrel patch ( left ) and coselli thoracoabdominal graft ( above ) .
this prosthesis allows single vessel reattachment , reducing the risk of recurrent aortic patch aneurysm . in our series the coselli branched graft has been used in 10.5% of cases .
the vascutek triplex graft is a new vascular prosthesis and consists of three layers : an inner polyester graft , an outer eptfe layer and a central layer of elastomeric membrane ( figure 5 ) .
the vascutek triplex graft consists of three layers : an inner polyester graft , an outer eptfe layer and a central layer of elastomeric membrane . in our preliminary experience with this graft
we found good handling and tailoring performances and actually a reduced bleeding from the suture lines .
finally , an end - to - end anastomosis with the distal aorta is performed . in some cases ( taaa type i )
endovascular procedures may be an appealing less invasive approach to the thoraco - abdominal aorta , however , the involvement of the visceral segment of the aorta represents a major challenge for taaa stent - graft repair .
although total endovascular treatment with branched stent - graft   has made it technically feasible to preserve visceral perfusion , the cost - efficacy and durability of these pioneering techniques are yet to be fully assessed .
hybrid taaa repair was first introduced by quiones - baldrich in 1999   and mainly consists of open aortic debranching and revascularization followed by endovascular exclusion of the aneurysm .
the inflow site for visceral grafts is a healthy artery , usually the infrarenal aorta , the iliac arteries or an infrarenal graft .
visceral and renal arteries are then ligated at the origin to avoid back - flow in the aneurysm and consequent type ii endoleak .
the open surgical stage requires a laparotomy and a transperitoneal or extraperitoneal access to the visceral vessels ; however , proximal aortic cross - clamping , thoracotomy , aneurysm exposure and monopulmonary ventilation are avoided ( figure 6 ) .
the hybrid procedure consisted of infrarenal aortic grafting with single visceral vessels revascularization ( center ) .
hybrid taaa repair may be indicated in case of previous descending thoracic aortic repair in which a redo left - sided thoracotomy may be associated with major bleeding , increased rate of postoperative respiratory and organ failure and longer total aortic clamping time . a further advantage of the hybrid treatment is the possibility to reduce organ ischemic time and perform visceral protection techniques by selective cooling .
hybrid repair is appealing in case of visceral aortic patch ( vap ) aneurysm after taaa conventional repair .
moreover , vap aneurysms have ideal straight and long  in - graft  proximal and distal necks where the stent - graft can be safely delivered . with this technique ,
the aortic branches are anastomosed separately and virtually no native aortic remnants are left in situ , thus avoiding the risk of recurrences . 
from literature , mortality and morbidity rates after taaa conventional repair remain significant even in high - volume centers   ( table 1 and 2 )
. these data could be not totally representative of the actual outcomes of taaa surgical repair .
analized data from the nationwide inpatient sample ( nis ) , dividing centers where taaa surgical repair has been performed ( 1988-'98 ) in low volume ( 1 - 3 cases / year ) , medium volume ( 2 - 9 cases / year ) and high volume ( 5 - 31 cases / year ) .
annual surgeon volume has been defined as low ( 1 - 2 cases ) or high ( 3 - 18 cases ) .
conclusions were that the results of low - volume centers and surgeons were significantly different from those of high - volume centers and surgeons .
results after taaa conventional repair - universit vita - salute , scientific institute san raffaele , milan , italy .
graphs show in - hospital mortality rates in function of annual hospital volume ( left ) and annual surgeon volume ( right ) .
in particular , in a specific subset of high - risk patients , the outcomes are associated to higher morbidity and mortality rates . as a result , these outcomes have encouraged some centers to consider the hybrid repair as the treatment of choice .
the data reported in literature regarding classification and extension of pathology , patient s overall clinical conditions , surgical technique and results of taaa hybrid repair are still very heterogeneous ( table 3 ) .  
further studies are needed to assess the safety , efficacy and long - term survival associated to the hybrid treatment of thoraco - abdominal aortic aneurysms .
the etiology of spinal cord ischemia during thoracic aortic procedures is multifactorial , and the risk of paraplegia is a debated concern .
conrad et al . demonstrated the impact of paraplegia / paraparesis on survival of patients who underwent surgical or endovascular taaa repair : 5-year survival rate was 25% in paraplegic / paraparetic patients versus 51% in patients with no spinal complications .
five - year survival rate was 41% in paraparetic patients , while no paraplegic patients survived for more than 5 years   ( figure 8) .
graphs show the impact of paraplegia/ paraparesis on survival of patients who underwent surgical or endovascular taaa repair ( sci : spinal cord ischemia ; scid : spinal cord ischemia deficit ; scid i : flaccid paralysis ; scid ii : muscle function < 50% ; scid iii : muscle function > 50% ) extensive coverage of the thoraco - abdominal aorta could be identified as the cause of a higher rate of spinal complications .
greenberg et al . compared total stent - graft length in patients that did and did not develope neurological deficit , demonstrating a significant association with the lenght of aortic coverage .
bckler et al . demonstrated that in the animal model endovascular repair is associated to lower spinal cord ischemia and paraplegia rates than aortic cross - clamping . during hybrid taaa repair , the avoidance of supraceliac clamping and the shortened duration of visceral ischemia should lead to greater perioperative hemodynamic stability compared with that during conventional open repair of taaa , and the risk of spinal cord ischemia
open surgical repair of thoracoabdominal aortic aneurysms has evolved significantly over the last decades thanks to technical improvements , especially in the area of organ protection . however , despite adjunctive strategies , morbidity and mortality rates are still not negligible .
surgical taaa repair is to be performed in high - volume centers by experienced surgeons .
the hybrid treatment is currently indicated in a subset of patients , however morbidity and mortality are significant .
further studies are needed to assess the safety , efficacy and long - term benefits of this technique .
 conventional treatment of thoracoabdominal aortic aneurysms ( taaas ) consists of graft replacement with reattachment of the main aortic branches . over the past 20 years 
 a multimodal approach has gradually evolved to reduce the trauma of surgery by maximizing organ protection , allowing experienced surgical centers to have better outcomes than previously reported . 
 however , mortality and morbidity associated to taaa open repair remain significant . 
 hybrid repair , consisting of open aortic debranching and revascularization followed by endovascular exclusion of the aneurysm , may extend the indications of taaa repair to high - risk patients that can not benefit from surgery , however results are still under evaluation . 
 aim of this paper is to illustrate the management and results of thoracoabdominal aortic aneurysms surgery with open techniques of organ protection and hybrid approach in our center . 
Introduction
Open repair
Hybrid repair
Results