Dynamism of the aortic annulus: Effect of diastolic versus systolic CT annular measurements on device selection in transcatheter aortic valve replacement (TAVR)

Background: Annular dimensions, including cross-sectional area, perimeter and subsequently derived diameters, are subject to dynamic changes throughout the cardiac cycle. There is ongoing controversy as to whether perimeter measurement changes between systole and diastole are too small to impact on valve sizing. Objectives: To assess both the variability of aortic annular dimensions throughout the cardiac cycle across a range of sub-annular calcification using computed tomography (CT) and the impact of this variability on device size selection for balloon-expandable valves in a large, all-comer multi-center cohort. Methods: ECG-gated CT data of 507 patients (mean 81 ± 7.5 years, 60.1% male) were analyzed in this retrospective, multicenter analysis. Aortic annulus dimensions were assessed on pre-specified systolic and diastolic phases by planimetry, yielding both area and perimeter. Contour smoothing was employed to avoid artificial increase in perimeter values by uneven contours. The extent of subannular calcification was graded semi-quantitatively and assessed in relation to the degree of annular dynamism. Hypothetical device sizing was undertaken to assess the impact of using systolic and diastolic measurements on valve selection. Results: Mean annular dimensions were larger during systole than diastole (area: 474.4 ± 87.4 mm² vs. 438.3 ± 84.3 mm² or 8.23%, p < 0.001; perimeter: 78.5 ± 7.2 mm vs. 75.9 ± 7.2 mm or 3.36%, p < 0.001). The magnitude of annular area and perimeter change (systolic minus diastolic measurement) was greater among patients without calcification compared to patients with grade 3 calcification. Using diastolic rather than systolic data for device sizing resulted in a change of the recommended valve size in nearly half of patients for both annular area and perimeter. Conclusions: The systematic differences between systolic and diastolic annular measurements for cross-sectional area and perimeter have implications for device sizing with potential for valve under-sizing if diastolic annular dimensions are employed.