Clement De Vecchi, Presenter: Nothing to Disclose

Jerome Caudron MD, Abstract Co-Author: Nothing to Disclose

Nathalie Pirot, Abstract Co-Author: Nothing to Disclose

Claire Werquin, Abstract Co-Author: Nothing to Disclose

Fabrice Bauer MD, Abstract Co-Author: Nothing to Disclose

Jean-Nicolas Dacher MD, PhD, Abstract Co-Author: Consultant, General Electric Company

To evaluate the influence of 2 factors resulting in under-estimating the aortic valve area (AVA) with transthoracic echocardiography (TTE) compared with MSCT in patients with aortic stenosis: the measurement of left ventricular outflow tract (LVOT) area and the pressure recovery (PR) phenomenon.

Retrospective single-center study involving 40 patients with severe aortic stenosis referred before transcatheter aortic valve implantation. The AVA was deduced from the continuity equation on TTE and planimetry from MSCT. The LVOT area was calculated as follows: on TTE, from the measurement of the LVOT diameter on the parasternal long-axis view, thus applying π.r2 formula; on MSCT, from manual planimetry using multiplanar reconstruction perpendicular to LVOT. Measurements of minimal (Dmin) and maximal (Dmax) diameters of the LVOT were also performed in order to calculate the eccentricity index (=1-Dmin/Dmax) of the LVOT. LVOT was considered non circular when eccentricity index was greater than 0.1. Aortic root diameters were measured at 3 levels (sinuses of Valsalva, sino-tubular junction, and tubular) to calculate the PR at each of these levels.

At baseline, correlation between TTE and MSCT was moderate (R=0.51, p=0.001), with constant underestimation of the AVA with TTE (AVATTE=0.65±0.14cm2) compared with MSCT (AVAMSCT=0.89±0.21cm2) (p<0,0001). After correction with PR, this difference decreased moderately (AVATTE/PR=0.73±0.18cm2, p<0.001 vs. MSCT), without improving the correlation (R=0.52, p=0.001). After correction with the LVOT area measured with MSCT, the corrected AVATTE/LVOT (0.91±0.27cm2) did not differ from AVAMSCT (p=0.75) and correlation significantly increased (R=0.64, p<0.0001). All patients had a non circular, i.e. an elliptic LVOT, with a mean eccentricity index measured at 0.23±0.07 (min=0.12, max=0.34).

The ellipsoid shape of the LVOT is a key element to explain the AVA estimates discrepancies between TTE and MSCT.

TTE consistently underestimates the AVA by considering LVOT as a perfect circle. A large MSCT study could help to define a mathematical correction of this important parameter.

De Vecchi, C, Caudron, J, Pirot, N, Werquin, C, Bauer, F, Dacher, J, Assessment of the Aortic Valve Area with MSCT in Severe Aortic Stenosis: Which Factors Explain Differences with Transthoracic Echocardiography?.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11007711.html