AimsTo evaluate the effects of applying current sizing guidelines to different multislice computer tomography (MSCT) aortic annulus measurements on Corevalve (CRS) size selection.Methods and resultsMultislice computer tomography annulus diameters [minimum: Dmin; maximum: Dmax; mean: Dmean = (Dmin + Dmax)/2; mean from circumference: Dcirc; mean from surface area: DCSA] were measured in 75 patients referred for percutaneous valve replacement. Fifty patients subsequently received a CRS (26 mm: n = 22; 29 mm: n = 28). Dmin and Dmax differed substantially [mean difference (95 CI) = 6.5 mm (5.7-7.2), P < 0.001]. If Dmin were used for sizing 26 of 75 patients would be ineligible (annulus too small in 23, too large in 3), 48 would receive a 26 mm and 12 a 29 mm CRS. If Dmax were used, 39 would be ineligible (all annuli too large), 4 would receive a 26 mm, and 52 a 29 mm CRS. Using Dmean, Dcirc, or D CSA most patients would receive a 29 mm CRS and 11, 16, and 9 would be ineligible. In 50 patients who received a CRS operator choice corresponded best with sizing based on DCSA and Dmean (76, 74), but undersizing occurred in 20 and 22 of which half were ineligible (annulus too large).ConclusionEligibility varied substantially depending on the sizing criterion. In clinical practice both under-and oversizing were common. Industry guidelines should recognize the oval shape of the aortic annulus.