A novel contribution towards coherent and reproducible intravalvular measurement of the aortic annulus by multidetector computed tomography ahead of transcatheter aortic valve implantation

Abstract

As current multidetector computed tomography (MDCT) measurements underestimate the size of the aortic annulus ahead of transcatheter aortic valve implantation (TAVI), a strategy of approximate annulus area oversizing has been adopted recently. To measure the aortic annulus using a novel complementary intravalvular MDCT slice. Fifty-five patients with severe aortic stenosis were selected for MDCT ahead of and 1 month after CoreValve(®) TAVI. Two MDCT slices were analysed and compared: the current standard virtual basal ring (VBR) at the nadir of the aortic cusps; and a novel slice, defined as the basal (lowest) complete commissural coaptation (BCCC) plane. BCCC is an intravalvular plane lying 5.2±0.8 mm above the VBR. The BCCC annulus is almost circular, unlike the VBR (mean eccentricity index 0.09±0.04 vs 0.3±0.1, respectively). The mean BCCC annulus diameter was 26.6±2.3 mm, 16% larger than that of the VBR (23.9±2.2 mm; P<0.001). The BCCC annulus area proved coherent with the orifice area measured after TAVI on the projection of the same slice (i.e. systematically equal to or greater than the latter [mean difference, +2.3±1.4 mm]), in contrast to the wider scatter found for the VBR (-1.3±2.0 mm). Once the sclerotic calcified valves have been pushed back by the implant, the aortic orifice after TAVI will inevitably be equal to or less than the diameter of the virtually unvalved annulus before TAVI. Based on the present results, we recommend including a BCCC slice to complete aortic annulus sizing, in order to optimize implant calibration.