Currently, the most widely accepted treatment for uncomplicated acute type B aortic dissection (UATBAD) is conservative management through optimal medical therapy (OMT), reserving thoracic endovascular aortic repair (TEVAR) for complications such as rupture, malperfusion syndrome, refractory or recurrent pain, and uncontrolled hypertension. TEVAR is not free of risks, it can lead to complications such as retrograde dissection to the ascending aorta, “bird beak” phenomenon leading to prosthetic collapse or type IA endoleaks, among others, especially when additional procedures on the supra-aortic trunks (SAT) are required. However, the benefits in medium- and long-term survival of implanting these endoprostheses in the presence of complications in UATBAD seem to outweigh perioperative morbidity and mortality. The use and indications of TEVAR in UATBAD are not as clear and continue to be a subject of ongoing debate.

The objective of this study was to analyze the results of TEVAR performed in complicated and uncomplicated UATBAD in the Global Endovascular Aortic Treatment Registry of WL Gore (GREAT). A total of 5014 patients were retrospectively analyzed, of whom 172 underwent TEVAR in a UATBAD situation. Of these procedures, 102 were complicated UATBAD and 70 were uncomplicated. There was a greater involvement of procedures involving the SAT in complicated UATBAD vs. uncomplicated (45.1% vs. 21.4%, p = 0.002). Patients in the complicated UATBAD group also had a longer average hospital stay (14.3 vs. 9.8 days, p = 0.002). There were no significant differences in 30-day mortality (2.9% in complicated UATBAD and 1.4% in uncomplicated) or in aortic complications (8.8% vs. 5.7%). The three-year aortic event-free survival was similar in both groups (62.9% vs. 70.6%).

The authors conclude that patients with UATBAD in the GREAT registry treated with TEVAR, whether they were complicated or uncomplicated cases, had a low and similar incidence of perioperative complications and mortality. The medium-term results in both groups were satisfactory.

COMMENTARY:

The guideline on the management of type B aortic dissection of the STS/AATS published in 2022 is clear. TEVAR is unequivocally the treatment of choice in complicated UATBAD, just as OMT is in uncomplicated UATBAD. On the other hand, TEVAR in uncomplicated UATBAD continues to be a controversial issue. Over time, TEVAR in this scenario has been gaining ground in recent years; however, the level of recommendation in this last guideline is still not high (recommendation class IIb), stating that prophylactic TEVAR may be considered in uncomplicated UATBAD to reduce the risk of death and long-term adverse events related to the aorta.

OMT, which primarily consists of controlling blood pressure below 120/80 mmHg and a heart rate less than 70 beats per minute, has shown excellent intrahospital and 1-year survival results in uncomplicated UATBAD. However, numerous registries and a clinical trial have shown that these patients over time develop aneurysms in a proportion close to 70% and a mortality between 3-5 years of 25-30%.

The only two clinical trials that compare OMT with TEVAR in uncomplicated UATBAD provide very relevant data in favor of TEVAR, but still insufficient. The INSTEAD XL study showed that TEVAR performed between week 2 and 52 after acute aortic syndrome (subacute and chronic phase) improves 5-year survival and delays disease progression compared to isolated OMT. On the other hand, the ADSORB study, which does compare OMT with TEVAR without waiting for the subacute phase, showed a reduction in diameter and thrombosis of the false lumen with the use of endoprosthesis, but we still do not have information on the impact of this in the long term. Observational studies that compare OMT with TEVAR in this scenario are scarce and provide unclear and sometimes contradictory results.

Spinelli and colleagues, in this study conducted with patients from the GREAT registry, contribute their bit by adding evidence in favor of the safety and effectiveness of TEVAR in uncomplicated UATBAD. The results of the GREAT registry are the result of the analysis of real-world patients. A total of 172 patients with UATBAD treated with TEVAR with Gore TAG prostheses between 2010 and 2016 were analyzed. In the group with complicated UATBAD, TEVAR is confirmed as the treatment of choice. However, the real value of this study is provided by the results in patients with uncomplicated UATBAD. Mortality at 30 days, 1 and 3 years was 1.4%, 3.2%, and 9.6%, respectively, figures equivalent or better than the results of other studies that analyze OMT in isolation. Additionally, the aortic event-free survival (composite event that includes reintervention, stroke, spinal damage, aneurysm growth, retrograde dissection, or persistence of the false lumen) was 77% and 71% at 1 and 3 years, respectively. These data confirm the perioperative safety of TEVAR for patients with uncomplicated UATBAD, and demonstrate that TEVAR is not inferior to OMT in the short term. Unfortunately, the average follow-up of this study was relatively short (2 years), and there is little information available to assess the effectiveness in aortic remodeling, such as changes in the false and true lumen. On the other hand, for years it has been known that there are a series of anatomical characteristics such as an aortic diameter > 40 mm, initial diameter of the false lumen > 22 mm, intimal tear near subclavian artery, among others that, when present, the patient is classified as high risk for developing late complications. In this study, it would have been of great interest to know which patients had these risk factors and their evolution based on the treatment.

In the absence of randomized clinical trials, the information from this subgroup of patients that comes from registries like this one is invaluable for advancing knowledge of the best therapy. In patients with low-risk uncomplicated UATBAD, it seems prudent to first advocate for OMT, and at a second yet to be determined time, assess elective TEVAR based on the circumstances of each case. However, given the poor long-term results of OMT in uncomplicated UATBAD and the growing evidence of the safety and effectiveness of TEVAR in this group of patients, in some cases endovascular therapy, especially in those patients labeled as high risk for late complications, could be the first therapeutic option. This would be the true metamorphosis of the management of uncomplicated UATBAD; change is the only constant thing, and in this field it would be no exception.

REFERENCE:

Spinelli D, Weaver FA, Azizzadeh A, Magee GA, Piffaretti G, Benedetto F, et al. Endovascular treatment of complicated versus uncomplicated acute type B aortic dissection. J Thorac Cardiovasc Surg. 2023 Jan;165(1):4-13.e1. doi: 10.1016/j.jtcvs.2021.01.027.

MacGillivray TE, Gleason TG, Patel HJ, Aldea GS, Bavaria JE, Beaver TM, et al. The Society of Thoracic Surgeons/American Association for Thoracic Surgery Clinical Practice Guidelines on the Management of Type B Aortic Dissection. Ann Thorac Surg. 2022 Apr;113(4):1073-1092. doi: 10.1016/j.athoracsur.2021.11.002.