Pulsatile distention of the nondiseased and stenotic aortic valve annulus: analysis with electrocardiogram-gated computed tomography

BACKGROUND: Knowledge of the dynamic changes of the aortic valve (AV) annulus may aid in the sizing and design of transcatheter valve prostheses. We assessed AV annulus distention in patients without AV disease and with severe AV stenosis (AS) using computed tomography (CT).

METHODS: Electrocardiogram-gated multislice CT scans of 15 patients without AV disease (age 53±12 years) and 20 patients with severe AS (age 81±6 years) were analyzed. Images in plane with the AV annulus were reconstructed for every 10% to 12.5% of the cardiac cycle. With the use of dedicated software the annulus was segmented. In all phases of the cardiac cycle the area was measured, as were the maximum radius (Rmax) and minimum radius (Rmin) of an ellipse fitted around the segmented lumen. The asymmetry ratio was defined as Rmax/Rmin. Direct comparison of both groups was not possible because age and scan protocols were confounding factors.

RESULTS: The mean change of the area, Rmax, and Rmin was 122±33 mm2, 1.8±0.7 mm, and 2.4±0.5 mm in the patients with nondiseased annulus and 98±52 mm2, 1.4±0.7 mm, and 1.9±0.8 mm in those with AS. The mean asymmetry ratio was 1.3±0.1, indicating an elliptic annulus. Both the asymmetry ratio and the area changed significantly over the cardiac cycle (p<0.001).

CONCLUSIONS: With the use of CT and postprocessing software, significant area and radius changes during the cardiac cycle were demonstrated in both the nondiseased annulus and the stenotic annulus. This finding may help selection of the optimal size in patients undergoing AV implantation and also aid in prosthesis design.