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Page 2 of 7 Sengupta et al. Vessel Plus 2020;4:40 I http://dx.doi.org/10.20517/2574-1209.2020.55

INTRODUCTION
With the conclusion of the recent low-risk trials, transcatheter aortic valve implantation (TAVI) has now
[1,2]
been approved for patients with symptomatic, severe aortic stenosis across all surgical risk categories .
Amidst these rapidly evolving clinical indications, several issues related to the long-term durability and
feasibility of TAVI in younger patients have been raised by the structural heart community. One such
example is transcatheter heart valve (THV) orientation during initial deployment and its impact on
commissural alignment. Whereas direct visual inspection and excision of native leaflets during surgical
aortic valve replacement (SAVR) readily allows alignment of the surgical valve commissures with the native
[3]
commissures, commissural alignment with THVs during TAVI is far more inconsistent and random .
Commissural malalignment may lead to varying degrees of overlap between the neo-commissural posts
[4,5]
and coronary arteries . Furthermore, experimental models have shown that THV leaflet stress and
[3,6]
central aortic regurgitation (AR) may be exacerbated with suboptimal commissural alignment . These
findings have significant clinical implications for younger patients who have an increased lifetime risk
of complications of aortic valve disease and coronary artery disease. Given that coronary reaccess and
redo-TAVI will become more prevalent in the future, achieving commissural alignment during initial
TAVI may impact the feasibility of both these procedures. Here, we review some of the salient features
of neo-commissural alignment and offer our perspectives on how to achieve a more physiologic valve
implantation.

CORONARY REACCESS
Contemporary THV device and delivery system designs do not allow for consistent and precise
commissural alignment. Following initial TAVI, an obstructive commissural post may significantly hinder
[5]
future coronary access by extending above, in front of, or through the coronary ostia . Coronary reaccess
is impeded not just by the obstructive THV stent frame, but also by an in situ barrier formed by the native
aortic leaflets. Thus, the anatomy relating the aortic root to the valve stent frame must be thoroughly
evaluated. The coronary arteries are easily reached when the sinotubular junction (STJ) or coronary ostia
are situated distal to the transcatheter valve stent frame. However, when either of these structures is located
below the THV frame, the TAVI operator would need to cross the stent frame to access the coronary
arteries. This may not be a major issue when using THVs with short stent frame heights provided that the
[7]
native aortic valve does not obstruct the open cells of the stent frame .
REINTERVENTION AFTER INITIAL TAVI
Commissural misalignment during initial TAVI also jeopardizes the success of future valve-in-procedures
for the treatment of prosthetic valve failure. While TAVI-in-SAVR is a relatively simple procedure, redo-
TAVI in the current era is associated with a number of anatomic risks, including coronary obstruction, that
[8]
are exacerbated in the absence of neo-commissural alignment . Thus, consideration of the THV leaflet
height within the anatomic boundaries of a patient’s aortic root becomes crucial when evaluating him or
her for redo-TAVI. As before, if the leaflets lie proximal to the coronary ostia, valve-in-valve TAVI should
be feasible. If not, an adequate margin between the valve stent frame and sinotubular junction is imperative
[7]
to prevent sinus sequestration and coronary obstruction .

In recent years, the BASILICA (Bioprosthetic or native Aortic Scallop Intentional Laceration to prevent
Iatrogenic Coronary Artery obstruction) procedure has been successfully applied in TAVI-in-SAVR cases
[9]
with a high risk of coronary obstruction . However, this procedure may not be as easily performed during
redo-TAVI, especially with supra-annular THVs since leaflet splitting can be impeded by the valve stent
frame. In cases of commissural misalignment that appose the commissural post to a coronary ostium, the
BASILICA technique may not completely eliminate the possibility of coronary obstruction in redo-TAVI.