Non-A non-B aortic dissections: are we still in uncharted waters?

Despite the fact that the indications for surgery in type A and type B acute aortic dissections are clarified and widely accepted by the cardiothoracic community, little is known for non-A non-B aortic dissections. The review and meta-analysis by Carino et al. [1], with regard to non-A non-B aortic dissections published recently in the journal, aimed to shed some light in this topic, and it was very educative, especially because there are no available guidelines for the management of this clinical entity. Conventional wisdom has it that the main flaws of a study usually stem from its retrospective nature. In this meta-analysis, all the selected papers are retrospective or observational studies. Beyond these single-arm observational studies, however, there is a paucity of data comparing modalities of treatment for this disease in the literature, therefore, this cannot be considered as a limitation of the study. The authors have explicitly shown that medical treatment in case of non-A non-B dissections is inferior to any kind of operation with reported rates for 30-day mortality 14% vs a 3.6% for surgery. Additionally, medical therapy for these dissections carries a mortality substantially higher than that of type B dissections. This finding, along with the relatively low mortality, stroke and retrograde dissection rate, dictate that management should be done by means of surgery. Another important element of this study is that in terms of surgical treatment, more than half of the patients underwent some form of thoracic endovascular aortic repair (TEVAR) (18% for TEVAR with extrathoracic transposition, 36% TEVAR with chimney graft and 21% for hybrid arch repair and zone 0 TEVAR). The applicability of endovascular repair of the aortic arch and descending aortic pathology is steadily expanding with encouraging outcomes [2]. The results of this meta-analysis indicate that TEVAR appears to be a viable option for the emergency setting of non-A non-B dissections. Finally, the authors have concluded that large prospective studies are necessary to establish that early intervention is indicated in non-A non-B dissections. In addition to this, we think that it would be of great interest if future research could provide more insight and focus on the comparison between endovascular repair techniques in terms of outcomes and complications as well as on long-term patency of chimney grafts. Management of non-A non-B dissections remains challenging, and our knowledge on the subject is still limited. Nevertheless, studies like this [1] will help surgeons to navigate and explore these uncharted waters.