Discussion

The aneurysm formation is a rare complication of coarctation of the aorta and has an undefined risk of rupture, particularly if they are adjacent to a residual haemodynamic obstruction.^{Reference Rothman, Ciccolo, Galindo and Evans5} Surgical correction of such aneurysms poses significant challenges of bleeding and risks of rupture.^{Reference Di Tommaso, Mannacio, Di Tommaso, Pinna, Fontana and Iannelli3} This may be further complicated by the aneurysm being located adjacent to the left subclavian artery.^{Reference Rothman, Ciccolo, Galindo and Evans5} Our case highlights the role of hybrid procedures for managing this situation and may be considered an alternative to open surgery.

The prevalence of aneurysms in the proximal or distal aorta is about 5% in the post-surgical era.^{Reference Preventza, Livesay, Cooley, Krajcer, Cheong and Coselli6} The distribution of the aneurysms are as follows: 32% proximal to the coarctation, 51% distal, and 17% involve the left subclavian artery rather than the aorta.^{Reference Di Tommaso, Mannacio, Di Tommaso, Pinna, Fontana and Iannelli3,Reference Preventza, Livesay, Cooley, Krajcer, Cheong and Coselli6} Inflammation of the aortic wall, congenital weakness of the aortic arterial wall, or asymmetric and enhanced shear stress may play a significant role in the development of aneurysm.^{Reference Pu, Chen, Chen and Feng1} A 16-month-old female was described with a saccular aortic aneurysm distal to her aortic coarctation without any history of intervention or vascular inflammatory disease.^{Reference Ozyuksel, Canturk, Dindar and Akcevin7} The pathology report demonstrated remarkable basophilic degeneration and vacuole formation at the transition zone between the coarctation and aneurysmal segments suggesting possible inflammation is the leading cause of the localised weakness of the aortic wall and subsequent aneurysm formation.^{Reference Ozyuksel, Canturk, Dindar and Akcevin7}

Endovascular approach has been previously described in a 44-year-old man with Jehovah’s Witness who had unrepaired coarctation of the aorta and presented with a pre-stenotic dissecting thoracic aortic aneurysm.^{Reference Di Tommaso, Mannacio, Di Tommaso, Pinna, Fontana and Iannelli3} An endovascular aortic repair in which two stent grafts were placed in the descending aorta was successfully performed. Another case reported a 46-year-old man with coarctation of aorta concurrent with aortic arch aneurysm invading the left subclavian artery in whom a novel fenestration device was utilised to create fenestration of left common carotid artery.^{Reference Bai, Liu, Jin, Li, Ji and Qu4} There are few other cases of this approach in the literature; however, they were all in adults with significant co-morbidities who were considered high-risk surgical patients.^{Reference Khavandi, Bentham and Marlais8,Reference Bell, Taylor, Aukett, Young, Anderson and Reidy9} In our case, the use of covered balloon or self-expanding stents would have jailed off the subclavian artery. Thus, a vascular graft was necessary to provide blood blow into the subclavian artery prior to stent implantation. Due to the curvature of the aortic arch, we felt that use of a self-expanding endograft would be the preferred approach as opposed to using multiple stiffer balloon expanding CP-covered stents. Though, the smallest diameter endograft that we had available was the 21-mm Gore TAG endograft. Due to the mismatch between the “normal” transverse aortic arch of 11 mm and the short landing zone between the origin of the left common carotid and aneurysm (13.3 mm), the TAG graft jumped distal into the proximal aneurysm. The decision was made to place a covered CP stent just distal to the take-off of the left common carotid artery and to dilate the segment up to 18 mm, thus allowing for a better landing zone for the TAG graft. Once a better landing zone had been established, a second 21-mm Gore TAG graft was able to be properly positioned within the aortic arch segment, thus entirely covering the involved aortic segment. Our case highlights that hybrid approach is a safe approach in children to avoid open-heart surgery.

There is another case with two-stage hybrid management for an adult patient with a large single aortic arch aneurysm that was located at the greater curvature close to left subclavian artery, and was complicated by aortic arch coarctation.^{Reference Pu, Chen, Chen and Feng1} This is similar to our case where the aneurysm was located at the greater curvature as well. Endovascular approach, such as percutaneous balloon dilatation and stent implantation, is not suitable in cases with extensive calcification and is associated with higher procedural risk of aortic rupture.^{Reference Pu, Chen, Chen and Feng1} Our patient was young and did not have any calcifications and thus, the hybrid approach was utilised. The stenotic left subclavian artery was intimately associated with the aortic arch aneurysms and thus, the combined surgical/endovascular approach was utilised for this patient. Though we felt we would be far superior to the origin of the anterior spinal artery, we placed a lumbar drain for spinal protection.

The management of patients with complex coarctation of aorta with aneurysms requires multidisciplinary care including vascular and interventional cardiologists. This is demonstrated well in our patient with successful outcome with collaborative approach. There are many variables influencing the treatment strategy and include the degree of coarctation; location of the aneurysm relative to the coarctation; the shape, size, and degree of calcification of the aneurysm; suitability of landing zones for percutaneous devices deployment; patient age; and presence of collateral flow if let subclavian artery exclusion is required.