Type of surgery techniques preceding endovascular treatment:

Extra-anatomic bypass, [4-5]:

1. Carotid-subclavian bypass (Fig. 1 and Fig. 2)

2. Carotid-carotid bypass (Fig. 3)

3. Carotid-carotid + carotid-subclavian bypass (Fig. 4 and Fig. 5)

LSA Revascularization

LSA is an important source of blood flow to the left arm but it also plays an important role for the collateral pathways to the cerebellum -via the left vertebral artery (VA)- and the spinal cord -via the left VA to the anterior spinal artery, and collateral perfusion to the left intercostal vessels through the internal mammary and thoracodorsal arteries-.

When revascularization of the LSA is strongly recommended, [6-10]:

• Occluded or severely stenosed right VA

• Clearly dominant left VA

• Discontinuity of the vertebrobasilar system

• Presence of a patent left internal mammary artery to coronary artery by-pass graft

• A functioning dialysis access fistula in the left arm

• In high risk patients for spinal cord ischemia:

  • patients requiring extensive coverage of the thoracic aorta where critical intercostal arteries originate;

  • patients who have undergone infrarenal aortic surgery (ligation of lumbar and middle sacral arteries);

  • patients with compromised hypogastric blood supply

Debranching of epiaortic vessels with sternotomy or ministernotomy [4-5; 11-14]:

1. Partial debranching: End-to-side graft from ascending aorta to innominate artery and right common carotid artery -> left common carotid artery ± left common carotid artery -> left subclavian artery bypass (Fig. 6)

2. Partial debranching: Bifurcated end-to-side graft from ascending aorta to innominate artery and left common carotid artery ± left common carotid artery -> left subclavian artery bypass (Fig. 7)

3. Total debranching: Trifurcated end-to-side graft from ascending aorta to all supra-aortic vessels (Fig. 8)

Aortic arch replacement with sternotomy [4-5; 11-14]:

1. En bloc total arch replacement (Fig. 9): using an island of aortic tissue, epiaortic vessels are attached to a corresponding opening into the convex portion of the prosthetic graft.

2. When the arch is heavily calcified, separated anastomoses of individual grafts to the arch vessels are performed (Fig. 10)

3. Dacron branched grafts designed for total aortic arch replacement may be used for this purpose (Fig. 11)

Elephant-trunk and Frozen Elephant-trunk techniques [15-17]:

1. Aortic arch replacement (± replacement of ascending tract) with elephant trunk technique (Fig. 12): a free-floating extension of the arch prosthesis, the so-called “elephant trunk” (usually 5- to 7-cm long), is left behind in the proximal descending aorta. This technique facilitates subsequent endovascular treatment (TEVAR) on the downstream aorta which, in our experience, could be performed in the same stage, avoiding the requisite thoracotomy or thoracoabdominal incision, mandatory in the traditional second surgical stage.

2. Aortic arch replacement (± replacement of ascending tract) with frozen technique (Fig. 13). This procedure is adapted from the previous technique, with E^®-vita prosthesis placement (Jotec, Hechingen, Germany). E^®-vita is a hybrid vascular graft consisting of a conventional tube graft with an endovascular stented graft in the distal end (http://www.jotec.com/english/produkte-hybrid.pml).

Role of Imaging

MDCT technology with ECG-gating for thoracic aorta improves spatial/temporal resolution and minimizes motion artifacts and examination time, thus:

1. allowing optimal one-step assessment of entire aorta, mediastinal structures, and lungs

2. providing optimal visualization of the coronary arteries

3. including in the same session also the intracranial vasculature and the iliac-femoral arteries.

Treatment planning

According to the classification that was initially described by Balm et al. [18], then modified by Mitchell et al.[19], and used in published reports by Criado et al.[20], the level and extension of aortic involvement are defined by using an “arch zone map” (Fig. 14) that has since been embraced by many around the world and incorporated in several clinical trial protocols. The classification divides the arch into actual four zones that could be used to define precisely the site of proximal fixation of a thoracic stent-graft. On this basis, the operative strategy is decided and procedure planning and materials are defined.

Role of the Diagnostic/Interventional Radiologist – Patient and pathology management – (Fig. 15)

• Choice of the type of endovascular procedure

• Choice of the vascular accesses

• Patient evaluation

• MDCT scan review (site and extension of the pathology) and stent-graft planning

• Choice of the devices

• Imaging follow-up, whichallows prompt recognition of complications, which is crucial for immediate management

Role of the Interventional Radiologist – Technical issues –

• Positioning of aortic endograft

• Other related procedures (before or after endograft)

• LSA occlusion (possible use of vascular plug)

• Possible PTA/stenting of iliac arteries

• Aortic fenestration

• Management of complications (e.g. vascular thrombosis, iliac dissection, embolism)

Pre- and post-operatory imaging findings at MDCT

Fig. 16 and Fig. 17 illustrate a case of an aortic arch aneurysm treated with sequential extra-anatomic by-pass followed by endograft repair.

Fig. 18, Fig. 19 and Fig. 20 illustrate a case of a chronic type-B aortic dissection managed with epiaortic vessels debranching with bifurcated graft and left common carotid -> left subclavian artery by-pass followed by endograft repair.

Fig. 21 illustrates a case of an aortic arch aneurysm treated with total debranching using a trifurcated graft followed by endograft repair.

Fig. 22 illustrates steps of the surgical part of the hybrid procedure (total debranching using a trifurcated graftsto all supra-aortic vessels) and the MDCT correlation for the treatment of extensive thoracic aortic disease.

Fig. 23 and Fig. 24 illustrates a case of an aortic aneurysm involving the aortic arch and the descending thoracic aorta, managed with total debranching using three separated graft anastomoses followed by stent-graft repair.

Fig. 25 and Fig. 26 illustrate a case of a huge aneurysm of the aortic arch and descending thoracic aorta with extensive wall thrombosis treated with elephant-trunk technique followed by stent-graft repair.

Fig. 27 and Fig. 28 illustrate a case of a huge aneurysm of the aortic arch and descending thoracic aorta with extensive wall thrombosis managed with frozen elephant-trunk technique followed by stent-graft repair.