Steep right anterior oblique view of self-expandable transcatheter aortic valve to timely detect stent under-expansion or non-uniform expansion before final release: a case series.

BACKGROUND

Severely calcified aortic valves are a major limitation of transcatheter aortic valve replacement, because eccentric and heavy calcification of the aortic valve occasionally inhibits self-expansion of the valve frame, resulting in stent under-expansion, including non-uniform expansion or infolding. Nevertheless, the two-dimensional nature of fluoroscopic projection imaging can limit detection of stent under-expansion prior to the final release.

CASE SUMMARY

We present two cases demonstrating the importance of the steep right anterior oblique (RAO) view (>50°) in detecting significant stent under-expansion of a self-expanding valve prior to the final release. In Case 1, despite enough pre-dilatation, the partially deployed transcatheter heart valve (THV) appeared to be a substantial under-expansion, which was detected only in steep RAO view. Immediately after the final release, the THV was spontaneously embolized into the ascending aorta (the so-called 'pop-up' phenomenon). Emergent implantation of balloon-expandable valve proved to be successful as a bailout. In Case 2, significant stent distortion and infolding, especially on the non-coronary cusp side, was successfully diagnosed only in a steep RAO view prior to the final release. This finding allowed THV recapture and replacement with a new THV.

DISCUSSION

Notably, the steep RAO view can visualize the THV from its short axis while eliminating parallax, allowing for accurate diagnosis of THV under-expansion particularly in patients with severe calcification in the non- or right-coronary cusp. Therefore, the steep RAO view allows timely detection of THV under-expansion before the final release, enabling THV recapture and the adoption of several management strategies.