Editorial Comment: Aortic branch vessel compromise vs clinically overt malperfusion in acute type A aortic dissection

In the present issue of the journal, Nagamine et al. [1] reported on a retrospective imaging analysis of aortic branch perfusion patterns in 34 patients operated on for acute type A aortic dissection. The aim of this study was to develop a novel classification system for branch perfusion patterns in type A aortic dissection, intended to improve the treatment strategy of these high-surgical-risk patients with end-organ malperfusion. The authors of this article should be congratulated for performing such an extensive analysis of aortic branch perfusion patterns in type A dissection patients. Patients with acute type A dissection and clinically overt malperfusion complications represent a challenging cardiac surgical cohort with a well-documented poor in-hospital outcome [2, 3]. Immediate central aortic repair is the preferred treatment strategy that restores peripheral blood flow to the compromised aortic branch vessels in most of these patients [3], as convincingly demonstrated by the authors of the current article. However, the resulting postoperative morbidity in this patient cohort is predominantly a consequence of ischaemic damage that had already occurred before the surgery and had been aggravated by the emergent procedure (i.e. ischaemia-reperfusion injury, coagulopathy and systemic inflammatory response). Therefore, percutaneous interventions followed by central aortic repair have been proposed for some specific subgroups of aortic dissection patients with a clinically overt preoperative malperfusion (e.g. mesenteric ischaemia) [4, 5]. The authors retrospectively analysed aortic branch perfusion patterns in acute type A dissection patients and classified them into three distinct categories and nine different branch vessels perfusion patterns. If this classification system is applied to a total of 11 vascular territories analysed in this report, it would result in a total of 99 possible perfusion patterns in a single patient. However, a significant proportion of patients with an acute type A aortic dissection present in severe shock (i.e. 30% in the present study) and undergo emergency surgery immediately after hospital admission. Therefore, a detailed analysis of all aortic branch perfusion patterns by means of Multi-detector computed tomography imaging, as advocated by the authors, may be not appropriate in such an emergency setting. Moreover, external computed tomography (CT) images from referring institutions that are performed as a screening examination to exclude a variety of acute clinical conditions, may be not sufficient for this thorough perfusion analysis of aortic side branches. The complexity is a clear limitation of the proposed classification system. The authors state in their article that ‘malperfusion syndromes associated with acute aortic dissection represent only a small proportion of identified aortic branch compromises’. However, this statement questions the clinical implications of the presented classification system. Despite a significant number of high-risk perfusion patterns in a total of 61 aortic branches before the surgery, clinically overt malperfusion syndromes were present in only 16 (26%) patients (9 patients with cerebral malperfusion and 7 with lower limb ischaemia) preoperatively. A total of 92% of these high-risk perfusion patterns were resolved sufficiently by means of the central aortic repair, without any clinical evidence of postoperative end-organ ischaemia. High-risk perfusion patterns persisted in only five (8%) aortic branches (i.e. four cervical branches and one abdominal branch) postoperatively. However, only a single patient suffered a new-onset cerebral malperfusion event postoperatively. Therefore, the clinical relevance of asymptomatic high-risk perfusion patterns in the aortic branches, as defined by means of CT imaging, may not be definitely answered by the present study. Moreover, the persistence of asymptomatic high-risk perfusion patterns after the surgery precludes any clinical implications in this specific cohort of aortic dissection patients. Given the large proportion of aortic dissection patients with high-risk perfusion patterns and no deleterious end-organ malperfusion, the role of percutaneous endovascular interventions remain unclear. However, as fairly recognized by the authors, the study cohort is very small, with only a few cases of clinically overt end-organ malperfusion. Despite the above-mentioned limitations, this study provides a very detailed picture of the involvement of the aortic branches in the acute type A aortic dissection before and after surgery, which is followed by meaningful and sharable comments and conclusions. The authors were able to convincingly demonstrate the key role of central aortic repair in resolving the high-risk perfusion patterns in the aortic branches as well as the clinically overt malperfusion. Another important message derived from this article is that the II-b-2 perfusion patterns are not always static lesions and may be resolved by the central aortic repair, particularly in the cervical aortic branches. Incomplete decompression of the false lumen after central aortic repair may be encountered more frequently in the abdominal branches, which is supposed to be due to residual re-entries in the abdominal aorta. In summary, this article provides new insights into the spatio-temporal diversity of aortic branch involvement in acute type A aortic dissection patients, which may contribute to the refinement of treatment strategies of these high-risk situations. Larger prospective studies are required to define the clinical impact of the proposed classification system on the specific cohorts of aortic dissection patients with aortic branch vessel compromise.