The treatment of ascending aorta diseases is usually performed by traditional surgery with median sternotomy and cardiopulmonary bypass. However, in some patients, the operative risk of this approach may be prohibitive. In these instances, endovascular approaches to the ascending aorta may be an alternative.
Endovascular approaches are being increasingly utilized to treat a variety of thoracic aortic diseases including aneurysms, pseudoaneurysms, dissections, penetrating aortic ulcers, traumatic aortic rupture, coarctation and abdominal aortic aneurysms .
Ascending aorta has several limitations for the endovascular approach, such as its larger diameter and the presence of the aortic valve and the coronary arteries.
2. Access and technique
The endovascular procedure is usually performed through the femoral arteries [1-3]. Sometimes this access is impossible or not recommended because of small size vessels, obstruction, calcification, dissection or extreme tortuosity.
The feasibility of endovascular treatment depends on many anatomic factors, including the diameter and the disease state of the access vessels [4,5]. Stenosis, calcifications, tortuosity, small size or dissection in both femoral and iliac arteries can make introduction of large sheath hazardous or impossible.
Endoprosthesis deployment in the ascending aorta usually requires large diameter and long sheath. There is always possibility of damaging the aortic valve, since the nose of the commercially available devices is designed for descending and/or abdominal aorta. The vascular prosthesis should be large enough to oversize by 15-20 % the aortic diameter and short in length to fit between the coronary arteries and the brachiocephalic trunk. This length usually measures 8 cm or less. The endovascular technique would have several advantages over the open surgical alternatives if the right tools for the procedure were available. Current thoracic aortic stent-grafts are too long, while abdominal aortic stent-grafts are too short and narrow. Moreover, abdominal aortic delivery systems are too short to traverse the long and tortuous path from the femoral artery to the ascending aorta.
The technique should be carefully planned. Rapid pacing and adenosine are useful to lower blood pressure and allow precise deployment. A rigid (Landerquist or super stiff) and long (260 cm) guidewire is usually placed in the left ventricle to give adequate support near the coronary arteries. This is similar to what we use when performing transcatheter aortic valve implantation (TAVI). One important tip is to perform a “wide J-shape” at the end of the rigid guidewire in order to prevent left ventricule perforation and, consequently, cardiac tamponade or left ventricular pseudoaneurysm.
Similar to other endovascular procedures, besides careful planning, patient selection and technical expertise are crucial to obtain satisfactory results. In this setting multidetector computed tomography (MDCT) plays an important role in selecting the patients suitable for the procedure and allows a careful and detailed step by step preoperative planning.
We have recently published a series of five clinical cases and described the technique in which the axillary artery was used to deliver the endograft for the treatment of different thoracic aortic diseases . We also demonstrated the possibility of concomitant treatment of ascending aorta disease and coronary stent implantation [10,11].
Transcarotid is another alternative access and, recently, transapical approach through a small left thoracotomy has been described.
3. Clinical cases
In this part we will discuss clinical cases of endovascular treatment of ascending aortic diseases showing different approaches and techniques.
3.2. Clinical case 2
A 57-year-old female underwent coronary artery bypass graft in another hospital with left internal mammary artery to the left anterior descending and saphenous vein graft to the right coronary artery. The patient developed mediastinitis and had 7 reinterventions resulting in acute bleeding through the sternum. She was sent to our hospital in cardiogenic shock and manual compression of the bleeding site in the sternum. Previous computed tomography showed ruptured pseudoaneurysm at the proximal anastomosis of saphenous vein graft to the (Figures 3-6).
3.3. Clinical case 3
A 74-year-old male with previous coronary artery bypass graft presented with iatrogenic ascending aortic pseudoaneurysm that occurred during angiography. The patient was at very high risk for surgical treatment, therefore an (Figures 7-9).
Both procedures were successfully performed and the patient was discharged without (Figures 10-12). At 6 months and 1 year clinical follow-up the patient had no symptoms as well as no other adverse cardiovascular events.
4. Target diseases
There are several pathologies of the ascending aorta that can be potentially addressed by the endovascular approach. Pseudoaneurysms or sacular aneurysms in the mid-ascending aorta are adequate for this technique because they usually appear with a sufficient proximal and distal landing zone. On the other hand, fusiform aneurysms have the limitation of lacking a sufficient landing zone in many cases.
Thoracic endovascular stent grafting has revolutionized the treatment of distal [type B] acute aortic dissection. Endovascular surgeons are now seeking the ways to improve the treatment of type A dissection by offering endovascular techniques to replace conventional surgical therapy. Less invasive endovascular therapy, obviates the need for sternotomy and cardiopulmonary bypass, reduces perioperative morbidity, and offers an alternative solution for those patients not eligible for conventional intervention due to co-morbidity or severe complications of the disease.
Thoracic stent grafting in the ascending aorta presents specific challenges and the role of uncovered stents is unclear in this situation. The majority of patients with acute type A aortic dissection has the intimal tear originated in the sinotubular junction. More than 90% of patients with this disease does not have sufficient proximal or distal landing zone required for secure fixation. Therefore, the site of the intimal tear as well as aortic valve insufficiency and aortic diameter >38mm are major factors limiting the use of endovascular therapy for acute type A dissection. Current available stents in use to treat type B aortic dissection do not address anatomical constraints present in type A aortic dissection in the majority of cases, hence the development of new devices is required.
5. Technical limitations
Endovascular approach of the ascending aorta has several limitations and is still in its beginning phase.
The diameter of the ascending aorta is usually larger than the rest of the aorta and the proximity with the aortic valve and the presence of the coronary arteries pose special challenges.
The length of the delivery system, which is designed for the abdominal aorta, does not allow to reach the ascending aorta through the groin.
Finally, the length of the endoprosthesis itself for descending aorta may be too long to be positioned between the coronary ostia and the brachiocephalic trunk.
Despite the fantastic progress in this field and the clear advantages of endovascular approaches for the ascending aorta in some clinical situations, one must bear in mind the high level of risk that these procedures entail.
Long-term data are not available to establish the safety and durability of stent-graft repairs. The cases described represent an off-label use of this technology and should be considered with the above mentioned limitations in mind.
The surgeon will need special skills in open aortic surgery and catheter based interventions to be able to plan the procedure carefully, to properly deliver the devices and to manage the potential serious complications .
Challenges in endograft design are the development of branched endografts and of pathology-specific endografts . However, the unique composition of the proximal thoracic aorta and the associated mechanical properties have to be taken into account and make this effort by far more complex than initially expected. Moreover, there is a need for reducing the stent-graft devices profile as well as for increasing conformability and trackability.
We believe that future advances with devices specifically designed for the treatment of ascending aorta diseases will allow this technique to be incorporated into routine medical practice.