The importance of stentgraft anchoring in the aortic annulus in endovascular treatment of acute aortic dissection type A

Kern et al. [1] report in their study on anatomical feasibility for the endovascular repair of acute aortic dissection type A using various currently available stent graft systems in 112 patients. They measured multiple aortic parameters to clarify the feasibility of implanting 6 commercially available systems including tubular, branched and fenestrated stentgrafts: Terumo ascending stent graft (Terumo Aortic, Sunrise, FL, OTS); Cook Zenith Ascend (Cook, Bloomington, Indiana, OTS); Cook Double Branched (Cook, Bloomington, Indiana, CMD); Relay Plus Double Branched (Terumo Aortic, Sunrise, FL, CMD); Najuta Stent Graft System (Kawasumi Laboratories, Tokyo, Japan, CMD); and Nexus Aortic Arch Stent Graft System (Endospan, Herzliya, Israel, OTS). They also assessed hypothetically the anatomical feasibility of all the aforementioned devices in which a valve-carrying component with inner branches or fenestrations at the bottom of the stent graft had been added to secure the diastolic coronary blood flow and anchor it in the aortic valve annulus. Anatomic suitability was determined by criteria provided by 3 manufacturers. The anatomic feasibility of the stentgrafts they analysed ranged between 4% and 21%. The main limitation was the short proximal landing zone and its large diameter. Adding a valve-carrying component increased the feasibility up to 80%. Understanding the pathology is essential whenever applying a new or available technology for the first time to treat new pathologies. Kern et al.’s publication [1] is an excellent example of how to solve clinical problems taking innovative approach by incorporating 2 different technologies. The well-known limitations of endovascular aortic repair in patients with acute aortic dissection type A is the lack of a satisfactory proximal landing zone [2, 3]. The role of the proximal landing zone is its sealing function between the stent graft and aortic wall, and to stabilize the stent graft, thus preventing its downstream migration. The landing zone is by definition a healthy aortic segment measuring not less than 2.5 cm length, non-dissected and of a normal diameter (<38 mm). The vast majority of patients with an acute aortic dissection present with it extending down to the aortic valve annulus level and involving at least the noncoronary sinus. In other words, most patients with aortic dissection type A have no adequate proximal landing zone. According to this report [1], 80–90% of patients are thus affected. It has already been postulated that to make the endovascular treatment of aortic dissection type A feasible, we need to specify a new proximal landing zone—namely the aortic valve annulus [2–4]. Since on average two-thirds of aortic dissections type A reveal at least a moderate aortic valve regurgitation [5], fixing a stent graft to a transcatheter aortic valve prosthesis, thereby enabling both aortic valve regurgitation therapy and fixing the stent graft in a stable landing zone—would seem to be a smart solution. The authors considered 2 designs of the portion between the transcatheter valve and aortic stent graft: a fenestrated design entailing an uncovered stent graft and a branched design, that is, a covered stent graft with 2 branches dedicated to both main coronary arteries. The branched design has the advantage of potentially effective treatment also in patients with an entry within the aortic root. The fenestrated design is an option only for those patients whose dissection entry is located above the sinotubular junction. The literature on implanting covered stentgrafts in the coronary arteries is limited. The small diameter of coronary arteries is behind the high risk of thrombosis that covered stentgrafts carry, making this approach quite theoretical. Similar results showing the Endo-Bentall concept’s high CT feasibility involving a tapered tubular covered stent graft with a transcatheter valve at the bottom and a fenestrated design between both components were recently published [6]. In that study, two-thirds of all patients presenting a type A dissection were potential candidates for treatment with endovascular valve-carrying conduits. Kern et al. should be congratulated for their research showing that going down as far as the aortic annulus and anchoring the stent graft in the aortic annulus will make the endovascular treatment of most patients with aortic dissection type A anatomically possible.