Type B dissections: keeping it “uncomplicated” in a complicated world

In the complex world of vascular surgery, where “high risk” is basically our love language, one topic continues to spark the debate: the uncomplicated type B aortic dissection. “Uncomplicated” may sound reassuring, but don’t be fooled. In reality, “uncomplicated” may just mean not yet complicating your life. These patients represent the calm before the storm, leaving clinicians to weigh whether it’s better to follow a conservative approach or go in early and do something heroic (and preferably endovascular).

Once upon a time, all type B dissections were approached as ticking time bombs — open surgery, big incisions and lots of drama. Outcomes, however, were far from ideal. As evidence emerged that doing less often yielded better results, the field shifted direction. Medical therapy became the dominant approach; enter the era of “let’s control the blood pressure and hope for the best.” Today, medical therapy — mainly antihypertensives and analgesics — remains the cornerstone for managing uncomplicated type B dissections.

Short-term survival left everyone quite satisfied: in-hospital survival was about 90%. Long-term results, however, were less pleasing. Survival drops to around 79% at five years, with approximately one-third of these initially “uncomplicated” patients eventually requiring intervention – procedures that are technically more challenging in the chronic phase with higher procedural risks. Turns out, “uncomplicated” is more complicated than it sounds.

Traditional management by open surgery was left behind, and by 1994, TEVAR was born — the minimally invasive knight in shining stent graft. For complicated dissections (rupture, malperfusion, shock, etc.), TEVAR is the undisputed hero. Without a doubt, everyone will recommend TEVAR for these complicated patients. But for “uncomplicated” dissections? The debate is as alive as ever. Of course, TEVAR has proven to enhance aortic remodeling with a better looking aorta on follow-up CT-images as a result. However, it also comes with its own bag of tricks: paraplegia, retrograde dissection, and, the worst of all, death. So, choose your risks wisely.

Two well-known early trials – ADSORB and INSTEAD(-XL) – have tried to settle the debate of TEVAR in “uncomplicated” dissections by randomizing patients to either medical therapy and TEVAR or medical therapy alone in the subacute and early chronic phase of the disease. TEVAR showed promising effects on aortic remodeling, and maybe, maybe for long-term survival. The differences in survival between both groups, however, weren’t statistically convincing enough to rewrite the guidelines. In other words: “Looks good so far, but not good enough to risk paraplegia, or worse…”

Even among TEVAR proponents, consensus on optimal timing of TEVAR is lacking. Intervene too early, and the aorta is angry, inflamed, and ready to tear at the seams. Wait too long, and you’ve lost your window for effective remodeling – and facing more technical challenges. Most agree that the subacute phase – roughly 2–12 weeks after onset of symptoms – represents a “Goldilocks zone”: not too hot, not too cold.

And now, the Nordics are here to save the day (and maybe the descending aorta). The SUNDAY trial — Scandinavian trial of Uncomplicated Aortic Dissection therapY — aims to answer the million-dollar question: Should we add early TEVAR to medical therapy in uncomplicated type B dissections to improve long-term survival? Besides all-cause mortality as the primary outcome of the trial, secondary outcomes will be reported, such as aortic-related mortality, neurological events, hospital readmissions, reinterventions and an economic analysis in conjunction with quality of life.

The trial randomizes patients between standard medical therapy alone or medical plus TEVAR in the subacute phase (e.g. 90 days after onset of symptoms). Besides the determination of the primary treatment plan by randomization, the medical and endovascular strategies are left to the discretion of each participating center. The study protocol only describes therapeutic targets – such as a target blood pressure of less than 120/80mmHg and heart rate of less than 60bpm – are predefined in the protocol.

Patients with an uncomplicated type B aortic dissection over the age of 18 are invited to participate in the trial. Of course, the protocol states some exclusion criteria. Patients with a history of descending aortic pathology already requiring TEVAR-treatment, a pre-existing thoracoabdominal aortic aneurysm or a traumatic aortic dissection exclude patients from participation. Furthermore, the diagnosis of dementia, a life expectancy of less than 2 years or a current septic state also exclude patients from participation in the trial.

Recruitment started in Aarhus, Denmark mid 2023, and is now ongoing in seven (soon to be nine!) countries: Denmark, Sweden, Norway, Iceland, Finland, the Netherlands, and New Zealand — with legal approval pending in Hungary (Figure 1). The study plans to enroll 550 patients, because apparently we need at least that many to make a statistical dent in a world this complicated. As of November 2025, 135 patients have entered the study. You can follow the saga at www.sundaytrial.dk.

As it turns out, the Nordics weren’t the only ones trying to solve the ongoing puzzle. The United States and Great Britain are apparently thinking along the same lines. The American IMPROVE-AD trial – IMPRoving Outcomes in Vascular disease-Aortic Dissection – and the British EARNEST trial – Early Aortic Repair in patients Needing Endovascular/open Surgery for Type B Aortic Dissection – set out on similar missions. As of early 2025, all three trials are officially up and running, recruiting patients across multiple countries. Hopefully, in ten years time, we will have enough data to finally answer the big question: TEVAR for uncomplicated type B dissections – yes or no?

Type B dissections may sometimes be labeled “uncomplicated”, but in the high-risk vascular world, nothing ever truly is. Between careful medical management, the timing of TEVAR, and the pursuit of optimal aortic remodeling, the only uncomplicated thing about these cases is how complicated they make our decisions. Until ongoing trials like the SUNDAY, IMPROVE-AD and EARNEST trial provide clearer answers, we’ll keep doing what vascular surgeons do best: arguing passionately, managing blood pressure aggressively, and hoping our “low-risk” strategy doesn’t turn “high-risk” overnight.