Oversizing in transcatheter aortic valve replacement, a commonly used term but a poorly understood one: dependency on definition and geometrical measurements

Background: In transcatheter aortic valve replacement, prosthesis oversizing is essential to prevent paravalvular regurgitation. However, the estimated extent of oversizing strongly depends on the measurement used for annular sizing.

Purpose: The aim was to investigate the influence of geometrical parameters for calculation of relative oversizing in transcatheter aortic valve replacement, reported as percentage in relation to the native annulus size, to standardize reporting.

Methods: Electrocardiogram-gated cardiac dual-source CT data of 130 consecutive patients with severe aortic stenosis (mean age, 81 ± 8 years; 56 men; mean aortic valve area, 0.67 ± 0.18 cm2) were included. Aortic annulus dimensions were quantified by means of planimetry that yielded area and perimeter at the level of the basal attachment points of the aortic cusps during systole. Area- and perimeter-derived diameters were calculated as DA = 2 × √(A/π) and DP = P/π. Hypothetical prosthesis sizing was based on DA (23-mm prosthesis for 19-22 mm; 26-mm prosthesis for 22-25 mm; 29-mm prosthesis for 25-28 mm). Relative oversizing for hypothetical prosthesis selection was calculated as percentage in relation to the native annulus size.

Results: Mean annulus area was 492.12 ± 94.9 mm2 and mean perimeter was 80.1 ± 7.6 mm. DP was significantly larger than DA (25.5 ± 2.4 mm vs 24.9 ± 2.4 mm; P < .001). Mean maximum diameter was 28.1 ± 3.0 mm and mean minimal diameter was 22.8 ± 2.4 mm. Calculated eccentricity index [EI = 1 - minimal diameter/maximum diameter)] was 0.19 ± 0.06. Difference between DP and DA correlated significantly with EI (r = 0.67; P < .001). Relative oversizing was 10.2% ± 3.8% and 21.6% ± 8.4% by DA and area, and 7.8% ± 3.9% by both DP and perimeter.

Conclusion: For planimetric assessment of aortic annulus dimensions with CT, the percentage oversizing calculated strongly depends on the geometrical variable used for quantifying annular dimensions. Standardized nomenclature seems warranted for comparison of future studies.