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Page 4 of 16 Annibali et al. Mini-invasive Surg 2022;6:12 https://dx.doi.org/10.20517/2574-1225.2021.101

Saluggia, Italy) and Trifecta (Abbott), were the only factors independently associated with coronary
[16]
obstruction .
As mentioned above, a rare event is then delayed coronary obstruction (DCO), defined as an obstruction
that occurs after the patient leaves the operating room after TAVR. It is more common in TAVR ViV after
self-expanding valve implantation. DCO was found in the first seven days after the procedure (63%), in 47%
of cases within 24 h, but also after 60 days (37%). Presentation with cardiac arrest was the most frequent
(32%). Mechanisms underlying early DCO, the one associated with higher mortality, include continuous
THV expansion, coronary dissection and aortic root hematoma. Mechanisms of late obstruction include
endothelization of native or surgical bioprosthetic leaflets or thrombus embolization that may occur in the
[21]
TAVR valve or sinus of Valsalva .

Other patients at high risk for coronary obstruction are those with small anatomies, especially narrow
sinuses of Valsalva, narrow sinotubular junction (STJ) and low coronary ostium. These patients have often
[14]
received a small surgical valve, which therefore increases the potential risk of coronary obstruction .
According to data from the Valve-in-Valve International Data (VIVID) registry, 28% of ViV TAVR were
labeled as 21 mm valves and, in the PARTNER surgical arm, approximately one-third of patients had
undergone cardiac surgery with a small valve [22,23] .

[24]
As recently demonstrated by Ochiai et al. , pre-TAVR CT scan can predict the risk of coronary
obstruction due to sinus sequestration in patients undergoing redo TAVR with low STJ height. After a post-
TAVR CT analysis, they documented a statistically significant difference in terms of coronary obstruction
due to sinus sequestration between the two groups (Evolut R/Evolut PRO group 45.5% vs. Sapien 3 group
2.0%, P < 0.001) and the inability to perform a preventive leaflet laceration procedure because of the
overlaps between the first THV commissural posts and the coronary ostium in a significant proportion of
patients. Thus, they concluded that a THV with low commissure height that was designed to achieve
commissure-to-commissure alignment with the native aortic valves may be preferable to avoid the risk of
coronary obstruction due to sinus sequestration and allow for a preventive leaflet laceration procedure in
[24]
future redo TAVR .
As identified by the Vancouver group, another key piece of information given by the pre-TAVR CT study is
the virtual distance between the THV and the coronary ostium, which has been shown to be a reliable
predictor of coronary obstruction. A virtual ring of the same diameter as the planned TAVR is inserted in
the center of the degenerated bioprosthesis, positioned at the height of the coronary ostium with a coplanar
alignment to more accurately reflect the position of the future prosthesis. This measure was defined as
virtual transcatheter valve-to-coronary distance (VTC). A VTC below 4 mm is a very accurate cut-off, with
high sensitivity and specificity (P < 0.001). There were no differences in ostium height between patients with
and without coronary obstruction . Distances of VTC and valve-to-STJ (VTSTJ) < 3 mm would be
[25]
considered at high risk of coronary obstruction as demonstrated by Dvir et al. .
[26]
To prevent this terrible complication, one of the most used techniques consists in the placement of a
guiding catheter and a coronary guidewire in the coronary artery at risk with a coronary balloon or an
undeployed stent ready to be used in case of coronary obstruction (chimney technique) [27,28] . Urgent stenting
of the left main was necessary in approximately 20% of patients who underwent coronary protection .
[16]
Unfortunately, even this technique may be associated with several complications such as inability to
withdraw the stent, mechanical deformation of the stent caused by the bioprosthesis or inability to re-access
to the coronary arteries in the future. In addition, there are no data regarding the long-term patency of these