Historically, the management of complex aortopathies was limited to open surgical repair, which carries a heightened risk of mortality and morbidity in elderly and comorbid patients [1]. In recent years, advancements in the management of complex aortic arch and descending thoracoabdominal aortic pathologies have increased treatment options for frail and elderly patients unamenable to conventional open repair. Among these, hybrid arch repair (HAR) with simultaneous or staged thoracic endovascular repair (TEVAR) has emerged as a viable option for this population. In this paradigm, HAR refers to the first component of a simultaneous or staged operation, whereby the great vessels are surgically debranched to create a proximal landing zone, which is followed by TEVAR of the remaining disease aortic segment [2]. When assessing the therapeutic benefit of such interventions, most studies classically assessed raw clinical outcomes, with an emphasis on survival benefit over time. One recent large series published by the Duke University Center for Aortic Disease [3] assessed the outcomes of 163 high-risk (47% prior sternotomy) patients undergoing HAR between 2005 and 2022. The most common indication for the procedure in this series included degenerative aneurysm (N=71, 44%) followed by residual dissection after prior type A repair (N=62, 38%). The authors found a 9% operative mortality at 30 days, with an overall survival rate of 59% and 47% at 5 and 10 years respectively.  Unsurprisingly, increased institutional experience was associated with improved operative and long-term survival.

While clinical outcomes are an important metric for assessing therapeutic benefit, the physio-anatomical impact of aortic intervention remains unclear. It is important to highlight those following invasive treatments, the aorta [4] undergoes a series of remodeling changes to adapt to laminar blood flow and reduce shearing stress on the vessel walls. Admittedly, there is no uniform criteria of what constitutes positive remodeling and definition is heterogenous between different studies and institutions [5]. Generally however, positive remodeling involves an expansion in the true luminal aortic diameter (TLD), regression in the size of the false lumen preferably with complete thrombosis, and a decrease or stabilizing of the total aortic diameter size [6,7]. To this point therefore, we believe that it is imperative to assess the impact of HAR+TEVAR on long-term positive aortic remodeling and correlate it with clinical outcomes to fully assess the operation’s therapeutic benefit in this high-risk population.

Recently we published our experience with 39 high-risk patients undergoing HAR+TEVAR at our high-volume aortic center in the Journal of Thoracic and Cardiovascular Surgery [8]. In that series, we had a mortality rate of 7.7% (N=3), need for dialysis rate of 10.5% (N=4), and no incidence of stroke, paraplegia, or type Ia, II, III, or IV endoleak. Additionally, we found compelling evidence supporting the efficacy of HAR with zone 0-5 TEVAR in facilitating positive aortic remodeling in aortic dissection patients, including improved true lumen augmentation down to zone 8 of the aorta, and complete false lumen thrombosis up to zone 5 at a weighted mean follow-up of 14.9 months. In the included cohort, we saw the greatest increase in TLD at the level of the left inferior pulmonary vein, tracheal carina, and inferior left atrium (+13.22 mm, +13.06 mm, +11.19 mm, respectively). Conversely, there was a much more modest and non-statistically significant increase in the mean TLD at the level of the aortic bifurcation (+0.27 mm) and right (+0.19 mm) and left (+1.32 mm) common iliac arteries. Our findings are consistent with prior literature showing diminished positive aortic remodeling distal to the infrarenal aorta. This trend is believed to be secondary to factors such as persistent visceral branch retrograde filling of the false lumen and distal false lumen perfusion secondary to re-entry tears in the intimal flap [9]. Another possible cause of less effective aortic remodeling in distal zones is due to disruption in laminar blood flow at the aorto-iliac bifurcation, which causes shearing stress and promotes localized atherosclerotic and inflammatory changes. Given these risk factors, for patients with dissections involving zones 9 to 11, operators should be weary of potential need for adjunctive treatment strategies to promote total aortic remodeling. Accordingly, in our published series, six of the nine patients requiring further interventions after their index HAR+TEVAR operation did so for indications, such as TEVAR extension and/or endovascular iliac aneurysm repair.

Importantly, our study had several limitations worth noting. Our series was relatively small, constituting under 40 patients undergoing the novel technique during a 2-year period (January 2020 – March 2022). The population was also highly heterogeneous ranging from acute or chronic presentations of both type A and B aortic dissection, as well as aortic aneurysms, Finally and arguably most important, our follow-up duration was limited to 15 months, which may not be enough to draw definitive conclusions regarding long-term aortic remodeling and associated morbidity/mortality. Currently, we are growing our cohort size and gathering long-term aortic remodeling surveillance data to follow-up our series.

As the average life expectancy across the world continues to generally increase, aortic referral centers will face a growing population of elderly patients and patients with comorbidities requiring surgical management of aortic arch and descending thoracoabdominal aortic disease. Stratifying patient risk levels and being able to offer hybrid and endovascular approaches to those patients with contraindications for conventional surgical repair will continue to be of paramount importance. We believe our study highlights the efficacy of HAR with staged TEVAR as a feasible alternative to conventional open repair and speaks to its potential role in the contemporary management of complex aortopathies. Looking forward, longitudinal studies with extended follow-up periods are warranted to elucidate the long-term implications of aortic remodeling on clinical outcomes. Doing so will help further refine modern management strategies and treatment algorithms for high-risk patients undergoing complex aortic repairs.

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