The therapeutic management of uncomplicated acute type B aortic dissection holds a class I recommendation in the 2014 European guidelines for medical management and IIa for interventional management. Whereas in the American guidelines of 2022, medical management receives a class 1 indication and the interventional approach, only for anatomies with a high risk of developing complications; 2b. Nevertheless, these patients exhibit a significant mortality during follow-up, raising questions whether early endovascular treatment could offer any benefit over the natural history of the disease and prevent the development of complications that have not initially occurred.

The highest quality evidence, available so far, comes from the European studies INSTEAD and ADSORB. Both presented low statistical power (n=140 and 61 patients, respectively), although in the first, a sample size calculation was performed. The included patients presented with uncomplicated acute type B aortic syndromes, but at different evolutionary phases, and none of them demonstrated a true short-term benefit or at the 5-year follow-up. It was the extension of the follow-up in the INSTEAD study beyond 5 years (INSTEAD-XL) that determined a benefit of TEVAR in patients with uncomplicated type B dissection treated in the subacute phase by adding cases of mortality in the medical treatment group (mortality 19.3% vs 6.9%, p<0.0045). There are no new randomized studies proving this until now.

The following article attempts to shed light in this respect. It involves a study of historical cohorts that included patients with uncomplicated acute type B aortic dissection treated in American centers affiliated with Medicare and Medicaid programs, between 2011 and 2018, with maximum follow-up until 2019. The results included all-cause mortality and the need for hospitalization due to cardiovascular and/or aortic causes, including the need for new interventions/interventionism. Treatment cohorts were compared between those patients managed with optimal medical treatment and those who received TEVAR in the acute phase of the disease.

Of 7,105 patients with acute type B dissection, 1,140 (16%) underwent initial TEVAR (first 30 days) and 5,965 (84%) received medical treatment. The assignment to one type of therapy or another was adjusted based on idiosyncratic care reasons of the centers (which included differences in the type of care coverage), the presence of comorbidities such as arterial hypertension (OR 1.2), peripheral vascular disease (OR 1.24) or frailty (OR 0.09), and the year (increase in procedures from 2011) were related in the multivariate analysis to a different probability of having received TEVAR vs. medical treatment.

One of the main criticisms of the work (for the purpose of homogenizing both groups, as claimed by the authors) comes from having excluded patients who died in the first 30 days or who did not have sufficient health coverage for that period were excluded. The observed mortality with both strategies up to the 5 years of follow-up did not show significant differences in mortality, nor in hospitalizations related to aortic pathology, nor the need for new therapeutic procedures. For the purpose of amending the bias with the exclusion of the deceased in the first 30 days, a sensitivity analysis was included that suggested that initial TEVAR was associated with lower mortality during a period of the first year (adjusted HR = 0.86; 95% CI 0.75-0.99; p=0.03), at 2 years (adjusted HR = 0.85; 95% CI 0.75-0.96; p = 0.008) and at 5 years (adjusted HR = 0.87; 95% CI 0.80-0.96; p = 0.004).

COMMENTARY:

This new study on TEVAR treatment in type B aortic dissection provides highly relevant information on a topic with a clear lack of solidity in terms of evidence. It also represents one of the main experiences in American practice published regarding the management of uncomplicated type B dissection. The procedure rate remains low and adherence to clinical guidelines remains the norm in clinical practice, in light of the 16% of patients who received TEVAR in the initial phase. Although the results of adverse events observed in the follow-up are not broken down for each of the treatment cohorts, the authors recognize the lack of benefit for indicating TEVAR in early phases. Indeed, they argue that the potential benefit of changing the natural history of the disease (aneurysm formation of the dissection) is countered with the aggregation of short-term complications (retrograde dissection, stroke, paraplegia) and long-term (treatment of endoleaks, progression of native disease). This uncertainty continues to make necessary the selection of those cases with a high risk of complication: hypertension or uncontrolled pain, maximum aortic diameter ≥40 mm, maximum diameter of the proximal false lumen ≥22 mm, true lumen waning without malperfusion, progression of periaortic hematoma, large single entry tear ≥10 mm proximal and especially if located in the lesser curvature and/or distal “cul-de-sac” with partial thrombosis of the false lumen, as candidates to benefit from TEVAR in the acute-subacute phase of the uncomplicated type B dissection.

REFERENCE:

Weissler EH, Osazuwa-Peters OL, Greiner MA, Hardy NC, Kougias P, O’Brien SM et al. Initial thoracic endovascular aortic repair vs medical therapy for acute uncomplicated type B aortic dissection. JAMA Cardiol. 2022 Nov 5. doi: 10.1001/jamacardio.2022.4187.