Nonoperative and interventional treatment in patients presenting with non-A non-B acute aortic dissection: Current management strategies and clinical outcomes

<h2>Abstract</h2> Non-A non-B aortic dissections (AD) are uncommon (3-11% of all aortic dissections) so, frequently, they are unrecognized and classified as type B dissections. Currently defined as a dissection with a primary tear in the arch (Ishimaru zone 1 or 2) or in Ishimaru zone 3 and retrogradely extending into the arch they indicate an heterogenous group of diseases that may deeply differ in terms of clinical and anatomical presentation. Affected patients tend to be younger (57 versus 65 and 67 years respectively) when compared with type A and B ADs and the clinical presentation and evolution seem to be frequently complicated (up to 88% of cases) with signs of malperfusion (29%) or risk of impending rupture (6%). Non-operative management seems possible in only a small percentage of NANB cases with most of the patients receiving intervention in the acute or subacute phase. However, because of the variability of the dissection anatomy and extent, the type and timing of treatment may vary, and there is no standardized treatment pathway. Despite its preferability, anatomic or goal-directed treatment does not yet represent the standard of care. The reported data is heterogenous, and thus it is difficult to compare the outcomes achieved with surgical and endovascular strategies. Taken at face value, the published papers demonstrate that the 30-day mortality rate is increased in patients treated medically versus those who undergo intervention (14% versus 3.6%), but populations included in these publications are not comparable: Most studies only focus on a single approach, with small sample sizes and limited detail on the anatomical features of the dissection. When an intervention is needed, several strategies have been adopted so far, including open aortic arch replacement or frozen elephant trunk (FET), thoracic endovascular aortic repair (TEVAR) with chimney stent graft or hybrid procedures with surgical rerouting of supra-aortic branches and TEVAR. After intervention, postoperative stroke rate ranges between 0% and 12.5% and post-operative myocardial infarction is described in up to 2.8%; aortic-related reintervention during follow-up are reported to be up to 43.6% in operative group. Because the heterogeneity and the lack of exhaustive data, a prospective study would be pivotal to provide more substantial evidence for the standardize application of surgical/medical approaches in this subgroup of patients of which immediate and long-term outcomes deeply relay upon the selection criteria and radiological findings at the initial onset