Contemporary management of acute type B aortic dissection has evolved over the last 15 years. In 2001 the European Society of Cardiology sought to review current diagnosis and management strategies regarding aortic dissection and provide recommendations and guidelines regarding optimal treatment [11]. This established the first set of society guidelines for aortic dissection. A task force of 11 members included one member appointed by the American College of Cardiology to include endorsement from that group as well. The group recommended strict heart rate and blood pressure control with beta-blockers and nitroprusside upon admission. Emergent operative repair was recommended in instances of hemodynamic instability. Other indications for operative repair in TBAD included persistent or recurrent chest pain, aortic expansion, periaortic hematoma, and mediastinal hematoma. Endovascular therapy was described as an evolving technique with goals of fenestration with or without stent placement for coverage of entry tears and relieving malperfusion due to the tears. However, the supporting evidence for endovascular intervention at this time was largely based on case reports and only awarded a GRADE “very low” quality of evidence. This paper served as the first formal guidelines supported by a society in the treatment of acute type B aortic dissections.

Interest in better delineating the treatment and outcome of acute aortic dissection led to the need for a robust database, culminating in the creation of the International Registry of Acute Aortic Dissection (IRAD) in 1996. All patients with acute aortic dissection confirmed by imaging, visualization in the operating room, or at autopsy are included and data are enrolled prospectively and a questionnaire of 290 variables is used to collect data. Initially, patients were enrolled from 12 centers in 6 countries, and now this has expanded to 24 referral centers in 11 countries. Reports from the IRAD database are published periodically [5, 12, 13].

In 2008 Fattori et al. analyzed the impact of different treatment strategies on survival in patients in the IRAD database [12]. This review included 571 patients with acute type B aortic dissection who were enrolled in the database between 1996 and 2005. Of these patients, 390 were treated medically and 125 were treated surgically. The surgical treatment group included 59 patients who underwent open repair and 66 patients who were treated with an endovascular approach. All patients were initially treated with aggressive antihypertensive and anti-impulse therapy. The patients undergoing open intervention suffered either extension of dissection, recurrent or refractory pain, visceral ischemia, or limb ischemia. The reasons for endovascular treatment included recurrent or refractory pain, and limb or visceral ischemia. Endovascular techniques employed in this group included stent graft repair as well as endovascular balloon fenestration of the dissection flap. Mortality in the endovascular treatment group was 10.6 %, while mortality in the open surgical group was 33.9 % (P = .002). In-hospital complications, including stroke, spinal cord ischemia, myocardial infarction, acute renal failure, limb ischemia, and mesenteric ischemia were observed in 20.8 % of the patients undergoing endovascular intervention, and in 40.0 % of the patients undergoing open surgical repair (P = .04). Patients with uncomplicated acute TBAD were treated with medical therapy only and mortality in this group was similar to that of the complicated acute TBAD group treated with endovascular therapy. This report demonstrated the likely better short-term outcomes of endovascular repair versus open surgical repair of complicated acute TBAD with respect to mortality and in-hospital complications. However, long-term follow-up was lacking and no comparison directly between medical therapy and endovascular treatment was available.

As a follow-up to this analysis, Fattori et al. reviewed the IRAD database to compare medical therapy to thoracic endovascular aortic repair (TEVAR) therapy [13]. This review included 1129 patients enrolled between December 26, 1995 and January 20, 2012, 853 of whom were treated exclusively with medical therapy, and 276 of whom were treated with endovascular stent-graft placement in addition to medical therapy. Of note, patients undergoing endovascular treatment were more likely to present with signs of malperfusion, pre-operative renal failure, and pulse deficit. Additionally, endovascular therapy was more frequently used in European centers compared to North American sites. Despite these differences in the patient populations, in-hospital mortality was similar between the two groups with 10.9 % mortality in the endovascular group and 8.7 % in the medically treated group (P = .273). Complications in this acute phase, including renal failure, stroke, spinal cord ischemia, and extension of dissection, were more common in the TEVAR group (38.9 % vs. 17.8 %). At 1-year post-discharge, the mortality was 8.1 % in the patients treated with TEVAR and 9.8 % in the patients treated with medical therapy alone, though this was not statistically significant (P = .604). Kaplan-Meier estimates were modeled for 5-year follow-up and projected a lower mortality rate for those patients undergoing endovascular treatment versus medical therapy alone (15.5 % vs. 29.0 %, P = .018). While late intervention rates were projected to be more common after TEVAR (30.6 % vs. 19.7 %), this was not anticipated to be significant (P = .810). Additionally, projections demonstrated a smaller descending aortic diameter in the group treated with TEVAR as compared to the medical therapy group with median diameter of 4.2 cm for the TEVAR group and 4.6 cm for the medical therapy group (P = .034). The analysis from this review demonstrates similar long-term mortality between patients treated with TEVAR versus medical therapy alone as well as favorable long-term aortic remodeling in patients undergoing TEVAR.

While IRAD does provide “real-world” review of acute aortic dissection, it lacks the rigor of a randomized study to provide better comparison of outcomes between medical therapy alone versus medical therapy and operative intervention. The Investigation of Stent Grafts in Aortic Dissection (INSTEAD) Trial was the first randomized trial to compare TEVAR and medical therapy for subacute TBAD [14]. Nienaber et al. recruited 140 patients in stable clinical condition between November 2003 and November 2005 and randomized to elective stent-graft placement in addition to medical therapy or to medical therapy alone. Seventy-two patients were randomized to the TEVAR group and 68 were randomized to the medical treatment group, with no significant differences noted between the two study groups. Patients undergoing TEVAR had TALENT stent grafts placed (Medtronic, Inc, Santa Rosa, CA). At 2-year follow-up, overall survival was 88.9 % in the TEVAR group and 95.6 % in the medical therapy group (P = .145). Freedom from aorta-related mortality at 2 years was also not significantly different between the two groups, 94.4 % for the TEVAR group and 97.0 % for the medical treatment group (P = .435). Similarly, there was no difference in progression of aortic disease, 77.2 % for the TEVAR group and 72.5 % for the medical treatment group (P = .545). Of note, there was a significant trend towards decreased false-lumen diameter with concomitant increase in true-lumen diameter in the TEVAR group at the 3-month, 1-year, and 2-year follow-up. Additionally, complete false-lumen thrombosis at 2 years was achieved in 91.3 % of patients undergoing TEVAR and only 19.4 % of patients undergoing medical therapy (P < .001). The overall observed mortality rate was lower than expected, leading to the study being underpowered. However, this study did confirm that TEVAR leads to favorable aortic remodeling and false-lumen thrombosis, fostering the argument for the expanded role for operative intervention in subacute TBAD, even in uncomplicated cases traditionally managed with medical therapy alone.

Nienaber et al. followed INSTEAD with INSTEAD-XL, the 5-year follow-up of the randomized study [9]. While all-cause mortality was not significantly different at 2 years, there was a significant survival benefit seen with TEVAR between 2 and 5 years with 100 % of TEVAR patients surviving that time frame compared to 83.1 % of the medical treatment group (P = .0003). Similarly, there was a significant decrease in aorta-specific mortality between 2 and 5 years for the TEVAR group, with no patients from the TEVAR group experiencing aorta-specific mortality between 2 and 5 years. At 5 years, the overall aorta-specific mortality was 6.9 % for the TEVAR group and 19.3 % for the medical treatment group (P = .045). TEVAR also out-performed medical treatment between years 2 and 5 with respect to progression of disease and aorta-specific events, with 95.9 % of TEVAR patients free from these events compared to 71.9 % of medical treatment patients (P = .004). False lumen thrombosis and aortic remodeling was favorable in the TEVAR group with complete thoracic false lumen thrombosis in 90.6 % and morphologic remodeling in 79.2 % at 5 years. The medical treatment group was conversely associated with an increase in aortic diameter in 66.0 % and only demonstrated false lumen thrombosis in 22.0 % at 5 years. INSTEAD-XL demonstrated that while TEVAR was associated with excess early mortality largely due to peri-procedural risks, TEVAR was beneficial in treatment of subacute TBAD with respect to overall mortality, aorta-specific mortality, aortic remodeling, and false lumen thrombosis with a number needed to treat of 13.