Invited editorial: anatomical feasibility of EndoBentall strategies for management of acute type A aortic dissection

Vallée and colleagues present an insightful retrospective radiographic examination of 116 consecutive acute type A aortic dissections, in order to assess candidacy for one of two possible EndoBentall repair strategies, while also introducing a novel anatomic nomenclature for the aortic root and proximal landing zone when performing these procedures (1).

Acute type A dissection remains associated with substantial mortality, and despite increasing surgical repair rates, as many as 10–20% of patients do not undergo surgery due to prohibitive dissection-related complications or comorbidities (2). Mortality remains above 60% in this nonoperative cohort, for whom emerging endovascular treatment strategies may be particularly beneficial (3).

Early endovascular attempts at treating type A dissection have focused on ascending endografting alone, building upon surgeon and industry experience with thoracic endovascular aortic repair (TEVAR) in the descending thoracic aorta and arch. While progress continues to be made with ascending aortic endografting, early reports of radiographic feasibility have consistently demonstrated that the most common reason for anatomic exclusion is an inadequate proximal landing zone (4,5). In the case of acute type A dissection, specific reasons have included proximity of the intimal tear to the coronary artery ostia or aortic valve, primary aortic root tear, or maximal aortic diameter larger than currently available devices (5). Despite these limitations, when used in appropriately selected patients, early feasibility results for ascending TEVAR in acute type A dissection have been promising (6).

Combining transcatheter aortic valve replacement (TAVR) technology with ascending TEVAR, the “EndoBentall”, has been conceived as a solution for endovascular treatment of acute type A dissection. The initial reports of utilization of the EndoBentall were for the treatment of complex proximal aneurysmal disease, with customized devices built for patient-specific anatomy (7,8). Our group was the first to publish the use of “off-the-shelf” devices in a modular fashion to create a branched EndoBentall to treat a complex aortoatrial fistula in a patient at prohibitive operative risk (9). Various EndoBentall configurations have included balloon-expandable and self-expanding TAVR valves, without consensus on which TAVR device is best at this time.

In 2023, Ghoreishi and colleagues reported their experience with the first two patients treated with a staged EndoBentall for acute type A dissection, utilizing a self-expanding TAVR valve, and commercially available TEVAR graft with physician modifications to combine both devices and create fenestrations for subsequent left and right coronary stenting (analogous to the “Branched” EndoBentall approach described here by Vallée and colleagues) (10).

While each iteration and application of the EndoBentall represents a significant effort to treat complex aortic root and ascending pathology, the concept will never grow beyond a few intrepid centers without improved predictive capability for patient candidacy, device design, and availability. This manuscript by Vallée and colleagues addresses several of these current knowledge gaps, and add objectivity with a new classification scheme so that subsequent research may speak a common language. Their focus remains on the application of the EndoBentall for acute type A dissection, and thus appropriately limits various size criteria to current commercially available TAVR and TEVAR devices. The proposed new aortic classification segments Zone 0 into four separate zones (labelled 0.1–0.4) based on their respective proximity to the sinotubular junction (STJ) in the case of Zone 0.1, or the innominate artery (Zone 0.3 & 0.4), with Zone 0.2 filling the remaining space between Zones 0.1 and 0.3. Uniquely, Zones 0.1, 0.3, and 0.4 will be essentially fixed across all individuals, and pertain specifically to suitable landing zones, while Zone 0.2 may be highly variable in both length and angulation across EndoBentall candidates. The authors have also added the concept of Zone −1, which represents the root (proximal to the STJ), and is further subdivided based on each specific sinus for additional detail. This new classification is highly practical as it specifically distinguishes the root from the ascending aorta, and does not rely on any other landmarks external to the aorta for measurement and nomenclature, as has been previously proposed (11).

Interestingly, despite relatively high radiographic candidacy rates for the EndoBentall based upon the location of the primary intimal tear in the ascending aorta (86%), suitability of the proximal landing zone remained the primary “Achilles heel” similar to previous reports focused on ascending endografting alone (1). In the current series, approximately 20% of patients were excluded based on annular size alone, and coronary anatomy due to inadequate height or insufficient length was an exclusion criterion in approximately 24% of cases.

Vallée and colleagues also analyzed patients for both branched and fenestrated EndoBentall configurations, with or without the need for coronary stenting respectively. Based upon their analysis, approximately 40% of EndoBentall candidates could be treated with a fenestrated endo-valved conduit (1). The true frequency of candidacy for a fenestrated EndoBentall remains to be determined, but several important challenges will remain. The acutely dissected proximal aorta presents an extremely challenging environment due to its: (I) high dynamism of motion; (II) complex geometry with differing lengths on the greater curve/lesser curve; and (III) a highly compliant, mobile dissection flap. Successful endovascular exclusion of the primary intimal tear requires elimination of all blood flow into a non-linear tear in a fragile intima. This requires “water-tight” seal zones proximal and distal to the tear for 1.5–2 cm. Given the anatomic challenges discussed above, a fenestrated Endobentall may only be successful with mid-ascending tears with long ascending aortas that afford 2 cm of seal zone proximal and distal to the tear. We believe that the branched EndoBentall (technically more challenging) affords the best chance of complete exclusion of all perfusion into the primary intimal tear, a concept supported by the fact that the majority of EndoBentall reports have used a branched technique (7,9,10).

Another potential limitation at the proximal landing zone is the application of TAVR technology designed to anchor within a calcific, stenotic aortic valve. In direct contrast, the vast majority of aortic valves in the setting of acute type A dissection are neither calcified nor stenotic, and frequently demonstrate acute aortic regurgitation. The current strategy in the limited reports describe anchoring the TAVR valve directly to the ascending endograft, or deploying valves within an endograft that spans the aortic valve. This requires rapid ventricular pacing +/− cardiopulmonary bypass to mitigate the risk of TAVR valve migration or embolization. This is a serious consideration that must be addressed in order for this procedure to gain widespread acceptance. The future design of a dedicated EndoBentall device for type A dissection should incorporate the newer TAVR devices built specifically for the treatment of aortic insufficiency rather than the current Sapien^TM (Edwards Lifesciences, Irvine, CA, USA) or Evolut^TM (Medtronic, Minneapolis, MN, USA) platforms, which were designed to treat aortic stenosis. Additional unanswered questions remain, including access vessel suitability for larger device delivery sheaths, the size and type (self-expanding vs. balloon expanding) of stents to accommodate most coronary arteries, the optimal degree of device oversizing for both the TAVR and TEVAR components, and how to address primary arch tears. Lastly, additional hurdles to overcome even after successful EndoBentall deployment will include prevention and/or management of any stent-induced new entry (SINE), endoleaks, and long-term coronary stent patency, which may be diminished if covered stents are required.

In conclusion, Vallée and colleagues present an insightful anatomic examination of EndoBentall feasibility in acute type A aortic dissection. These authors highlight what may be currently achievable within the limitations of commercially-available devices, while also showing areas for improvement and innovation to treat a deadly disease. In addition to shared experience, partnership with industry to innovate and produce novel EndoBentall devices is paramount to advancing the endovascular treatment of acute type A aortic dissection.

Acknowledgments

None.

Footnote

Provenance and Peer Review: This article was commissioned by the editorial office, AME Surgical Journal. The article has undergone external peer review.

Peer Review File: Available at https://asj.amegroups.com/article/view/10.21037/asj-24-57/prf

Funding: None.

Conflicts of Interest: Both authors have completed the ICMJE uniform disclosure form (available at https://asj.amegroups.com/article/view/10.21037/asj-24-57/coif). B.G.L. is a speaker for Medtronic and a consultant for Endospan Inc. The other author has no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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