Background: The details and consequences of a small aortic annulus among transcatheter aortic valve replacement (TAVR) patients remain uncertain. This study investigated the short-term outcomes in patients with small annular size and compared the 30-day outcome between intra- and supra-annular devices, with similar outer casing diameter in this subgroup. Methods and Results: Cases registered in the Japanese national TAVR registry between August 2013 and December 2017 were analyzed. Among a total of 5,870 registered patients, 647 (11.0%) had small annulus (area ≤314mm2) measured by multi-detector computed tomography. Patients with a small annulus had a significantly smaller indexed effective orifice area (iEOA, 1.10cm2/m2 [0.92–1.35] vs. 1.16cm2/m2 [0.96–1.39], P<0.001) and higher mean pressure gradient (mPG, 10.0mmHg [6.9–14.2] vs. 8.5mmHg [6.0–11.5], P<0.001) compared with a normal-sized annulus. Among patients with a small annulus, those receiving a 20mm intra-annular device had a smaller iEOA (0.94cm2/m2 [0.78–1.06] vs. 1.07cm2/m2 [0.8–1.24], P=0.001) and higher mPG (14.0mmHg [10.0–18.5] vs. 11.0 [7.0–14.0], P<0.001) compared with those receiving a 23-mm supra-annular device, although the incidence of paravalvular leakage (≥moderate) was similar (14.4% vs. 16.5%, P=0.69). Conclusions: Patients with a small annulus were associated with less hemodynamic improvement. A supra-annular device is associated with better echocardiographic improvement in patients with a small annulus, without increasing paravalvular leakage.
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