Uncomplicated type B aortic dissection (uTBAD) has traditionally been conservatively managed through intensive pharmacological therapy from diagnosis, continuing during follow-up if clinical-radiological stability is maintained in successive controls. However, the evolution of progressively increasing evidence reflects a scenario where a considerable volume of patients benefit from or need invasive procedures to correct the progression of their aortopathy or to prevent potentially lethal complications.

Research in this field is plagued by heterogeneity (patients at different stages of the disease, different follow-up durations, and different goals: mortality, aortic remodeling, etc.) and studies with limited statistical power. The generation of evidence began, firstly, from the INSTEAD and ADSORB studies, where TEVAR was compared to optimal medical treatment (OMT) in the subacute and acute phases, of patients with uTBAD. In none of the cases was a benefit obtained with respect to OMT. It was the INSTEAD-XL study that first demonstrated a survival benefit at 5 years related to aortic events in patients treated with TEVAR in relation to a limitation of disease progression and better aortic remodeling. Since then, different observational works supported this thesis, proposing different predictors that would allow selecting the best candidates for TEVAR in subacute and chronic phases. The culmination of this work was provided by the analysis of the GREAT registry, showing good results for the application of TEVAR in patients with uTBAD in the acute phase, where new predictors were identified.

The work by Kreibich et al. (from Czerny’s team in Freiburg, Germany) describes the natural history of uTBAD. They selected 91 patients affected between 2012 and 2018, all of them initially managed with OMT. They performed a 5-year follow-up finding, at a median follow-up of 4 months, 33% had required some invasive procedure. The indications for this were the progression of aortic diameters >5 mm/year (67%), dynamic obstruction or claudication (23%), recurrent pain (7%) and one case of aortic rupture. The invasive procedure that was mainly performed was TEVAR (83%) with/without left subclavian artery bypass. Elephant trunk surgery was reserved for those cases with involvement of the aortic arch in the pathology (10%) and repair was performed via a thoracoabdominal approach in those where the involvement extended distally to the thoracic aorta (7%). TEVAR was also rejected for those patients in whom a sufficient landing zone could not be obtained despite the transposition of the left subclavian artery or carotid-subclavian bypass when the diameters of the ascending aorta and/or arch exceeded 40 mm or there was some underlying connective tissue disorder. There was no periprocedural mortality, and the mortality during follow-up was 3 patients for non-cardiovascular reasons. In the univariate analysis, different factors, which we will mention below, were presented significantly more frequently in the patients who required an interventional/surgical/hybrid strategy compared to those in whom management continued with OMT. In the multivariate analysis, only an aortic diameter >45 mm was shown as an independent predictor of having an indication for performing some interventional/surgical procedure.

The authors concluded that in patients with uTBAD, initially managed with OMT, the need for additional endovascular, surgical or hybrid procedures was substantial. It is necessary to establish new management criteria based on the available evidence that optimize the assignment of patients to the best treatment strategy at each evolutionary moment of their pathology.

COMMENTARY:

The work of Kreibich et al. perfectly describes the natural history of uTBAD in the context of modern OMT and calls for an update of the consensus documents that do not reflect the reality of the available evidence. Reviewing the predictors that indicate benefit in survival and aortic wall remodeling with TEVAR compared to OMT, which are discussed in this work and in subsequent comments on it, we have:

In the acute phase (<14 days), defined as “high-risk” uTBAD, currently included in the 2020 SVS/STS clinical guidelines: poorly controlled pain, refractory arterial hypertension, pleural effusion, radiological evidence of arterial obstruction without signs or symptoms compatible with malperfusion.
In the subacute phase (2 weeks – 3 months): entry door on the lesser curvature and >10 mm, false lumen diameter >22 mm and aortic diameter >40 mm in the first diagnostic angiography, partial or absent thrombosis of the false lumen, elliptical true lumen (instead of circular, which is a good prognosis), false lumen without exit door in “cul-de-sac” and rehospitalization for aortic cause in the first 30 days after diagnosis.
In the follow-up with OMT (>3 months) proposed in the work of Kreibich et al. and concordant with the previous literature: partial or absent thrombosis of the false lumen, greater length of dissection extension, greater amount of communications between lumens (this criterion has not been constant in the literature or has been considered a protective factor), greater proximity of the entry door to the left subclavian artery, size of the entry door >10 mm and location on the lesser curvature (although these last ones were not significant in the work of Kreibich et al.), larger diameters of thoracic and abdominal aorta with a cut-off point at 45 mm (other works have suggested 40 mm), non-A non-B dissection (entry door in the aortic arch) and diameter of the false lumen >22 mm.
The number of predictors makes one consider the almost oxymoron “dissection” and “uncomplicated”. Indeed, this justifies that in a third of the patients a conservative strategy is not enough, and its perpetuation, harmful. After all, OMT only delays the natural evolution of the disease; TEVAR achieves a high rate of correction with a favorable risk/benefit balance thanks to the advancement of technology and the experience of the teams. Therefore, that procedure still assigned to a class of evidence IIb, conceived as prophylactic, probably has to be reconsidered in the therapeutic algorithm of these patients, apparently, uncomplicated.

REFERENCE:

Kreibich M, Siepe M, Berger T, Beyersdorf F, Soschynski M, Schlett CL, et al. Intervention rates and outcomes in medically managed uncomplicated descending thoracic aortic dissections. J Thorac Cardiovasc Surg. 2021 Apr 27(21)00729-7. doi: 10.1016/j.jtcvs.2021.03.126.