Historically, open surgery for acute ascending aortic dissection (AAAD) of DeBakey Type I has primarily focused on resecting the ascending aorta segment containing the primary intimal tear to survive this catastrophic emergency. Surgeons have accepted that if the remaining dissected distal aorta dilates in the future, complex reoperation could be performed in an elective context. In the past decade, mortality rates and complications such as stroke and malperfusion after this emergent procedure appear to have improved. In contrast, long-term complications due to residual aortic dilation remain an unsolved issue. The primary underlying causes of aortic dilation include intimal tears allowing reentry into the proximal thoracic aorta and false lumen (FL) patency. Most studies on FL after AAAD surgery focus on FL diameter and/or thrombosis. However, the FL in the aorta has complex, dynamic, and three-dimensional features, and such studies may not accurately capture its true characteristics.
The aim of this study was to investigate whether the ratio of the maximum false lumen area (MFLA) in the distal aorta predicts late aortic dilation and reintervention following open repair of DeBakey Type I AAAD. For this, 309 patients with DeBakey Type I AAAD treated with proximal aortic repair between 1994 and 2017 were analyzed. In 230 patients with non-thrombosed FL in postoperative computed tomography (CT), the MFLA ratio (MFLA/aortic area) in the descending thoracic aorta was measured via postoperative CT. Patients were divided into three groups based on MFLA quartiles: low MFLA, <0.62 (n = 57); intermediate MFLA, 0.62 to 0.81 (n = 116); and high MFLA, ≥0.82 (n = 57). The aortic expansion rate was significantly higher in the high MFLA group (11.1 ± 21.2 mm/year) compared with the intermediate group (3.0 ± 7.4 mm/year; p < 0.01) and the low group (0.6 ± 6.6 mm/year; p < 0.01). A high MFLA ratio was found to be an independent risk factor for significant aortic expansion (HR = 5.26; p < 0.01) and aorta-related reintervention (HR = 4.99; p < 0.01), and the MFLA ratio was significantly associated with reentry tears in the proximal descending thoracic aorta.
The authors conclude that a high MFLA ratio in the descending thoracic aorta following DeBakey Type I AAAD repair is associated with a greater risk of late aortic reintervention and distal aortic dilation. A high MFLA ratio is strongly associated with reentry tears in the proximal descending thoracic aorta.
COMMENTARY:
In this retrospective study by Kim et al., 309 DeBakey Type I AAAD cases over 20 years were analyzed. This study is rare and genuine as it includes long-term information on both clinical outcomes and imaging follow-up. The three most relevant findings would be: 1) a growth rate >10 times higher in the high FL ratio group compared to the low FL ratio group; 2) a significantly higher incidence of reintervention in the high FL ratio group with an HR of 4.99; and 3) a clear association between aortic growth and proximal reentry tears.
Most surgeons would not be surprised by these findings. They seem quite expected, before this article’s publication, they were merely asumptions. This data has been substantiated by the large annual patient volume and the excellent and detailed follow-up of both clinical and imaging outcomes. Additionally, the study is highly relevant due to the current availability of hybrid open and endovascular techniques in cardiovascular surgery teams.
To my knowledge, this is the most comprehensive study demonstrating that residual FL following DeBakey Type I AAAD repair is a risk factor for aneurysm formation. These results lead to further questions: Are there preoperative factors that can help predict which patients will have a larger FL? Should early intervention be considered in cases of a high FL ratio, even if they do not meet the surgical criteria for aortic diameter? What is the best technique to treat the residual aorta given the range of available hybrid procedures? Is it increasingly necessary to establish specialized aortic teams, and if so, which patients should be referred to these centers of excellence?
To date, most information on the safety of complete aortic arch surgery in DeBakey Type I AAAD comes from retrospective studies, mainly conducted like this one, in Asia. Currently, the first randomized study in North America (HEADSTART) is underway to compare standard hemiarch surgery with more extensive aortic surgery in patients with DeBakey Type I AAAD. Hopefully it may provide answers to many of these questions.
REFERENCE:
Kim JH, Lee SH, Lee S, Youn YN, Yoo KJ, Joo HC. Role of False Lumen Area Ratio in Late Aortic Events After Acute Type I Aortic Dissection Repair. Ann Thorac Surg. 2022 Dec;114(6):2217-2224. doi: 10.1016/j.athoracsur.2022.03.054.
