Endovascular treatment of thoracic aortic diseases

Bacground/Aim. Endovascular treatment of thoracic aortic diseases is an adequate alternative to open surgery. This method was firstly performed in Serbia in 2004, while routine usage started in 2007. Aim of this study was to analyse initial experience in endovacular treatment of thoracic aortic diseses of three main vascular hospitals in Belgrade – Clinic for Vascular and Endovascular Surgery of the Clinical Center of Serbia, Clinic for Vascular Surgery of the Military Medical Academy, and Clinic for Vascular Surgery of the Institute for Cardiovascular Diseases “Dedinje”. Methods. Between March 2004. and November 2010. 41 patients were treated in these three hospitals due to different diseases of the thoracic aorta. A total of 21 patients had degenerative atherosclerotic aneurysm, 6 patients had penetrating aortic ulcer, 6 had posttraumatic aneurysm, 4 patients had ruptured thoracic aortic aneurysm, 1 had false anastomotic aneurysm after open repair, and 3 patients had dissected thoracic aneurysm of the thoracoabdominal aorta. In 15 cases the endovascular procedure was performed as a part of the hybrid procedure, after carotidsubclavian bypass in 4 patients and subclavian artery transposition in 1 patient due to the short aneurysmatic neck; in 2 patients iliac conduit was used due to hypoplastic or stenotic iliac artery; in 5 patients previous reconstruction of abdominal aorta was performed; in 1 patient complete debranching of the aortic arch, and in 2 patients visceral abdominal debranching were performed. Results. The intrahospital mortality rate (30 days) was 7.26% (3 patients with ruptured thoracic aneurysms died). Endoleak type II in the first control exam was revealed in 3 patients (7. 26%). The patients were followed up in a period of 1–72 months, on average 29 months. The most devastating complication during a followup period was aortoesofageal fistula in 1 patient a year after the treatment of posttraumatic aneurysm. Conversion was performed with explantation of stent-graft and open aortic in situ recontruction, followed by esophagectomy and the creation of cervical and gastrical stoma. Conclusion. Having in mind initial results of the 3 main vascular clinics in Belgrade, Serbia, economical situation in our country, as well as the published international results, endovascular treatment of thoracic aortic diseases is indicated in hemodinamicaly unstable patients with acute traumatic aneurysm, or in stabile patients older than 65, as well as in case of chronic diseases of the thoracic aorta in patients with significant comorbid conditions or in patients older than 65 years. Endovascular procedures on the thoracic aorta could be performed, hower, only in high-volume centers with experience in routine open surgery of thoracic aorta.


Introduction
In the last decades we have faced an increased incidence of all diseases of the thoracic aorta -degenerative, traumatic and dissected aneurysms, penetrating aortic ulcers (PAU).Some of them (dissected) are more frequent among middle-aged, patients or in very young patients (traumatic).Besides being medical burdery these diseases are the economic burden to society 1 .Early results of the treatment of these diseases has been improved with introduction of endovascular procedures 2 .
First endovascular surgery on the thoracic aorta [thoracic endovascular aneurysn repair -(TEVAR)] in Serbia was performed in 2004 at the Institute for Cardiovascular Diseases (ICVD) "Dedinje".However, these procedures have been routinly performed in Serbia since 2007.
The aim of this study was to present the first initial experience in thoracic aortic diseases treatment in the three main vascular hospitals in Belgrade -Clinic for Vascular Surgery of the Military Medical Academy, Clinic for Vascular Surgery of ICVB "Dedinje" and Clinic for Vascular and Endovascular Surgery of the Clinical Center of Serbia.

Methods
From 2007 to December 2010, 41 patients were treated with TEVAR due to different diseases of the thoracic aorta.The average age of the treated patients was 72.43 years.Twenty one (51.29%)patients had degenerative aneurysm of the thoracic aorta, 6 (14.63%) patients was operated for PAU, 6 (14.63%) patients had traumatic (acute 1 patient or chronic 5 patients).Four (9.75%) patients had ruptured thoracic aneurysm, and 1 (2.43%) patient had anastomotic aneurysm after open treatment, and 3 (7.26%)patients had dissected aneurysm of thoracoabdominal aorta (Table 1).Indications for endovascular treatment were significant cardiorespiratory comorbid condition, hostile thoracic cavity and older age.

Results
Figure 1 shows penetrating aortic ulcer before (A) and after TEVAR (B), Figure 2 aortic dissection type B before (A) and after TEVAR (B), and Figure 3 shows traumatic aneurysm of the isthmic segment of the thoracic aorta before (A) and after TEVAR (B), too.
The procedure TEVAR was performed as a part of the two-stage hybrid procedure in 15 (36.45%) patients (Table 1).Before TEVAR, due to the short aneurysmal neck, subclavian transposition was performed in 4 patients and carotid-subclavian bypass in the 1 patient; due to hypoplastic or stenotic iliac or femoral artery iliac conduit was performed in two cases; 5 open reconstructions of the abdominal aorta; 1 aortic arch debranching and two visceral debranching procedures were also performed.Different kinds of two-stage hybrid procedures are shown in Figures 4-6.

-Multislice computed tomography (MSCT) angiograhy of a patient at high risk for complete open repair of thoracoabdominal aneurysm type II (Crawford classification) -the visceral part of the abdominal aorta repaired in the first stage (A), and proximal thoracic aneurysm repair with a stent-graft in the second stage (B)
In the first 30 postoperative days the 3 (7.26%)patients died.All these patients were treated for ruptured thoracic aneurysm.Endoleak type II was encountered in 3 (7.26%)patients with no other complications.All the patients were followed up 1-72 months, on average 29 months.Persistent endoleak type II was registered in 2 patients but without increasing aneurysm diameter.One patient had the most devas- tating complication -aortoesophageal fistula (AEF) developed 1 year after the TEVAR procedure due to posttraumatic thoracic aneurysm.AEF was treated with explantation of stentgraft and open in situ aortic reconstruction and omentoplasty, followed by esophagectomy with cervico-and gastrostoma.This procedure was complicated with aortobronchial fistula in the early postoperative recovery period treated with another stent-graft implantation.The patient was discharged after several months of care in order to be prepared for coloplasty, however, in the meantime he passed away in caohexic state due to malnutrition, with no signs of a new graft infection.

Discussion
Conventional open treatment of thoracic aortic disease comparing to abdominal aortic diseases is a far more complex procedure due to necessity to protect and perfuse the spinal cord and viscera 3,4 .The TEVAR procedure brought a significant improvement in treatment of these pathology, especially in high risk patients [5][6][7][8][9] .However, TEVAR is limited by anatomical and morphological conditions or the thoracic aorta close to the aortic arch or to the visceral region of aorta 10 .Some of the limitations could be avoided, with some adjuvant procedures.In 4 patients we performed subclavian transposition, and carotid-subclavian bypass in 1 patient due to the short aneurysmal neck.Subclavian artery origin covering could cause arm, brain or spinal cord ischemia 10 .In patients with ruptured thoracic aneurysm covering of the subclavian artery origin was complicated by stroke, coma and death.In case of more proximal extention of aneurysm into the aortic arch, safe stent-graft implantation is possible only after previous "debranching" procedure (revascularization of the supraaortic branches with anatomical or extraanatomical reconstruction) 11 .A patient from our study suffered fatal stroke on the third postoperative day following the successfull anatomical debranching procedure.Thoracic stent-graft safe implantation is possible if aortoiliac and femoral segments provide a diameter more than 7 mm, no sever tortuosity or anerysmatic dilatation with intraluminal thrombus at risk of embolization 12 .In 2 patients we performed iliac conduit, and in 5 patients we performed reconstrucion of the abdominal aorta in the first stage to secure safe passage of a delivery system.
Inadequate endograft fixation can be the cause of endoleak type I 16 .The other types of endoleaks are the consequence of retrograde flow from the intercostal arteries, inadequate sealing between the graft components or fractures of stent-graft matherial or armature.Spinal cord ishemia is always a concern when thoracic aortic disease is to be treated.Risk increases with covering the subclavian artery, long segment of the thoracic aorta, if the abdominal aorta is already reconstructed or hypogastric and the lumbal arteries occluded 17 .In all our patients with these risk factors we performed preventive measures for keeping perfusion pressure with the middle systemic pressure above 100 mmHg, cerebrospinal fluid drainage and previous revascularization of vertebral or hypogastric bed.There were no episodes of spinal cord ishemia in our patients.
Long-term complications after TEVAR are still under investigations.One of the most devastating complication is aortic graft infection with fistulization to surrounding organs, the esophagus and the bronchus 15,18 .Open treatment of these complications is one of the options and our patient suffered early aortobronchial fistula after the treatment.There is stil no consesus about the best treatment options.
Stent-graft migration is also a possible early or longterm complication requiring correction 19 .Younger patients with traumatic injuries are more prone to this complication because of their arch anatomy, and because of the estimated long-term survival as well as due to aortic growth rate 20 .All these reasons should be kept in mind when selecting the method of treatment of acute aortic injury and stent-graft diameter because hypotension of these patients could reduce a measured aortic diameter.TEVAR of dissected aneurysm of-fers promising results only if treated by criteria that already exist for aneurysms -if there is a sufficient proximal and distal landing zone which is rare.For these purposes, the authors give algorithm of thoracic aortic disease treatment in Figure 7.

Conclusion
In cases with acute traumatic injury of the thoracic aorta in hemodinamically unstable or politraumatized patients or patients older than 65 years, TEVAR is an acceptable method.In cases with chronic diseases of the thoracic aorta in high risk patients TEVAR is indicated, as well as in patients older than 65 years.
TEVAR safe and secure perfomance and its adjuvant procedures, as well as treatment of all complications is, however, possible only in high-volume centers with prevous experience in open treatment of thoracic aortic diseses.

Fig. 6 -
Fig. 6 -(A) Multislice computed tomography (MSCT) angiography shows a distal thoracic and suprarenal aneurysm in high risk patients; (B) The first stage of procedure was infrarenal aortic repair with bifurcated graft, with bypass from the left limb to all the four visceral branches; (C) Ten days later, aneurysm was excluded with a stent-graft.