Abstract
Background: Uncomplicated type B aortic dissection (un-TBAD) has been managed conservatively with medical therapy in order to control the heart rate and blood pressure to limit disease progression, in addition to radiological follow-up. However, several trials and observational studies have investigated the use of thoracic endovascular aortic repair (TEVAR) in un-TBAD and suggested that TEVAR provides a survival benefit over medical therapy. Outcomes of TEVAR have also been linked with the timing of intervention.
Aims: The scope of this review is to collate and summarise all the evidence in the literature on the mid- and long-term outcomes of TEVAR in un-TBAD, confirming its superiority. We also aimed to investigate the relationship between timing of TEVAR intervention and results.
Methods: We carried out a comprehensive literature search on multiple electronic databases including PubMed, Scopus and EMBASE in order to collate and summarise all research evidence on the mid- and long-term outcomes of TEVAR in un-TBAD, as well as its relationship with intervention timing.
Results: TEVAR has proven to be a safe and effective tool in un-TBAD, offering superior mid- and long-term outcomes including all-cause and aorta-related mortality, aortic-specific adverse events, aortic remodelling, and need for reintervention. Additionally, performing TEVAR during the subacute phase of dissection seems to yield optimal results.
Conclusion: The evidence demonstrating a survival advantage in favour TEVAR over medical therapy in un-TBAD means that with further research, particular trials and observational studies, TEVAR could become the gold-standard treatment option for un-TBAD patients.
Introduction
Stanford type B aortic dissections (TBAD) involve an entry tear in the intimal layer of the aorta distal to the left subclavian artery (LSA). Blood leaves the true lumen (TL) into the false lumen (FL), which expands over time and can eventually rupture [1]. This original entry tear can propagate antegrade or retrograde and may result in static obstruction of a branch vessel and malperfusion/ischaemia of end-organs. The other mechanism for malperfusion is via dynamic obstruction, which is more common and caused by intermittent blockage of a branch vessel by the mobile intimomedial dissection flap [2].
TBAD can be subcategorised based on presence of complications and time frame. Complicated TBAD (co-TBAD) exhibits certain symptoms on presentation which associate it with higher mortality and morbidity. The two principal complications are aortic rupture and end-organ malperfusion. If rupture or malperfusion are absent then the TBAD is classified as uncomplicated TBAD (un-TBAD). Using time of onset, TBAD can be classified as acute (<15 days since symptom onset), subacute (15-90 days since symptom onset), and chronic (>90 days since symptom onset) [1]. However, the onset-based classification of TBAD according to the International Registry of Acute Aortic Dissection (IRAD) is hyperacute (<24h), acute (2–7 days), subacute (8–30 days), and chronic (>30 days). Knowing the time phase of TBAD is clinically important as the dissection flap becoming less compliant over time which may negatively influence aortic remodelling [3].
Un-TBAD is managed conventionally with optimal medical therapy (OMT), also known as best medical therapy (BMT), to strictly regulate the heart rate (<60 bpm) and blood pressure (systolic BP < 100-120 mmHg) [4, 5]. However, un-TBAD patients who are discharged with OMT alone maybe lost to follow-up and the disease progresses to become fatal. Some survival analyses showed that up to 50% of un-TBAD patients on OMT alone were dead by 5-years [5]. Several trials and observational studies have investigated the use of thoracic endovascular aortic repair (TEVAR) for un-TBAD in an effort to shift the paradigm), but there are certain high risk features which may need be considered if a stent graft is an option [4]. These were summed up nicely in a recent interesting review by Jubouri et al. [4] who combined the evidence from these studies, including the INSTEAD, INSTEAD-XL, and ADSORB trials, as well as multiple retrospective studies. All of these which proved the TEVAR does offer a long-term survival advantage and improved aortic remodelling in un-TBAD patients relative to OMT alone. Jubouri et al. [4] also looked at how the timing of TEVAR intervention influences outcomes and confirmed TEVAR in the subacute phase of un-TBAD yielded optimum results. To assess any superiority, the aim of this review is to sum up the evidence in the literature on the mid- and long-term outcomes on TEVAR in un-TBAD.
Late outcomes (>30 days)