Thoracic endovascular aortic repair (TEVAR) demonstrates a one- and five-year survival advantage over the current “gold standard” practice of medical therapy in the treatment of uncomplicated type B aortic dissection, a recent study concludes. In light of these data, lead author James Iannuzzi (currently on staff at University of California San Francisco Medical Center) and senior author Virendra Patel (Division Chief of Vascular surgery at Columbia University Irving Medical Center) and colleagues call for a paradigm shift in the acute management of aortic dissection in favour of early TEVAR.
Citing a paucity of data regarding the impact of acute treatment of uncomplicated type B aortic dissection on long-term survival in a real-world cohort, the study investigators set out to compare TEVAR to open repair and medical therapy.
In their retrospective analysis of a prospectively collected Californian administrative database analysing 9,165 acute uncomplicated type B aortic dissections, 76% of those treated with TEVAR survived to five years’ post-treatment, compared with an inferior five-year survival rate of 67% in open repair patients, and a survival rate of 60% for medical therapy recipients.
The authors hypothesise that the mechanism by which TEVAR may have a favourable impact on survival is “by covering the entry tear, leading to false lumen thrombosis and prevention of aneurysmal degeneration.” They go on to explain: “Evidence from complicated type B aortic dissections treated with TEVAR demonstrates 63% to 88% partial or complete false lumen thrombosis. TEVAR for complicated type B aortic dissection has also been associated with decreased aortic diameter; however, this remains controversial as it has not been demonstrated consistently. By prevention of aneurysmal degeneration, initiation of false lumen thrombosis, and prevention of recurrent dissection, TEVAR may improve long-term survival, as demonstrated in this study and others.”
Iannuzzi and colleagues conclude that TEVAR for uncomplicated type B aortic dissection is a relatively safe and effective approach, associated with longer survival, but note that further study is necessary to determine longer term outcomes for these patients.
Major complications were lower in TEVAR and medical therapy cases than for open repair, with 49% of patients treated with medical therapy experiencing a major complication, and 55% of TEVAR patients, compared to a major complication rate of 72% in open repair cases. Paraplegia rates were also similar between TEVAR and medical therapy (3.4% and 2.9%, respectively), but where found to be highest in the open repair group (9.3%).
Speaking to Interventional News about the clinical ramifications of this finding, Patel comments, “Medical therapy has historically been the gold standard in the management of uncomplicated acute type B aortic dissection, however this work and others call that strategy into question as TEVAR treated patients are associated with better long term survival. This will not be a strategy to treat all patients; however, patients with excellent anatomy and young or healthy patients with expected long term survival should be considered for treatment in experienced centres or referral to aortic centres for TEVAR within the critical window of opportunity to stimulate beneficial remodelling, reduce late aortic events, and improve survival.”
Previous small, randomised controlled trials have found similar results. For example, the Investigation of Stent Grafts in Aortic Dissection (INSTEAD) trial, which randomised patients to optimal medical therapy or TEVAR for treatment of subacute to chronic uncomplicated type B aortic dissection, did not demonstrate a survival benefit at one year (as published in the Journal of Thoracic Cardiovascular Surgery in 2010), but did find that patients treated with TEVAR had improved aorta-specific survival at five years’ follow up. Iannuzzi and colleagues’ study included nearly four times as many TEVAR patients as the INSTEAD trial, and had concordant results.
Explaining the difference between the present study and the INSTEAD trial, the authors write: “A major difference between INSTEAD and this retrospective administrative study is timing of repair. The INSTEAD trial included healthier patients overall with a younger age (mean age of 60 years compared with 66 years), fewer diabetics (6% in INSTEAD vs. 12% in this study), and fewer smokers (17% in INSTEAD compared with 30% in this study). Whereas INSTEAD was a landmark study, corroboration in the real-world setting is imperative, and this study helps validate the INSTEAD findings that long-term survival is improved in patients treated with TEVAR.”
A proponent of stenting more uncomplicated subacute dissections, interventional radiologist Darren Klass, Vancouver, Canada, told Interventional News: “Type B aortic dissection carries a five-year mortality of 20–45%. Since the pivotal trials including STABLE and INSTEAD XL, the question of TEVAR for complicated dissection requires no discussion and patients progress with medical therapy alone. The IRAD demonstrated patients who survive a type A dissection and are discharged from hospital have a plateau in mortality, however patients with type B dissection have a mortality of 25% at three years. These patients therefore constitute a group of so-called ‘uncomplicated dissections’; it is this group, where medical therapy alone is clearly failing—as demonstrated yet again in the recent study by Iannuzzi et al.
“I am convinced we should be treating more uncomplicated type B dissection but two questions remain. 1) What is the ideal timing interval for intervention, and 2) Which patients should be treated?
“We have multiple studies quoting risk factors for aortic progression (entry tear, false lumen and overall aortic size) as well as risks for significantly higher mortality (more than three anti-hypertensive medications), however are these the only surrogates for a more complex disease we do not fully understand? Desai et al (Division of Cardiovascular Surgery, Perelman School of Medicine, University of Pennsylvania, USA) demonstrated a significantly lower complication rate if TEVAR occurred two to six weeks post event. If we could demonstrate reliably an extremely low periprocedural complication rate with an agreed method for TEVAR (PETTICOAT or stent grafting to the celiac), is it possible all uncomplicated dissections would be treated with TEVAR? We do not have the answer yet, but I know if I was unfortunate enough to become a patient, regardless of risk factors for progression, I know what treatment I would demand. Retrospective data or not, I know which Kaplan-Meier curve I want to be on, and it is not the medical therapy one.”
TEVAR twice as expensive as medical therapy in the USA
However, TEVAR was twice as expensive as medical therapy. Costs averaged US$58,000 for medical therapy, compared with US$133,000 and US$200,000 for TEVAR and open repair, respectively. The present study is the first to include cost data when comparing these treatment options in type B aortic dissections, and no prior cost-effectiveness analysis has evaluated TEVAR for uncomplicated dissection. The price tag associated with TEVAR differs dramatically between countries, though, as is expected from vastly differing healthcare systems. Whilst the cost in this US study is not comparable with medical therapy, in a recent Canadian trial, TEVAR cost as little as CA$61,000, less than half of the US expense. Furthermore, a German study of complicated aortic dissection demonstrated TEVAR to be more cost-effective than open repair.
Despite the initial increased cost of TEVAR compared with medical therapy, and the post-therapy surveillance costs incurred by both treatment modalities, the study authors postulate that over a longer time period, the former procedure may demonstrate an improved cost-effectiveness, “given the 25% to 40% increased risk for aneurysmal degeneration over time” present in medical therapy.