P981Lvot area measurement using gated ct data reclassifies aortic stenosis severity as graded by echocardiography

Abstract

Background: Measurement of left ventricular outflow tract (LVOT) diameter and area for estimation of aortic valve area (AVA) using transthoracic echocardiography (TTE) and the continuity equation assumes circular LVOT. The use of direct planimetric measurement of LVOT area by gated-CT can theoretically improve accuracy of AVA calculation.

Purpose: We aim to assess reproducibility of LVOT echo measurement and its correlation and agreement with Gated CT measurements. In the subgroup with aortic stenosis (AS) we secondarily assessed the potential change in AS severity using LVOT area by CT instead of TTE in the continuity equation.

Methods: We retrospectively studied 93 patients, 43 of whom with severe AS. LVOT Area was measured with 2D TTE by 2 expert echocardiographers and gated-CT by 2 expert radiologists; inter-reader agreement and inter-method (Echo vs gated CT) agreement and correlation were measured. Finally we used the measurement of CT scan in the continuity equation instead of TTE measurement to assess potential reclassification of AS severity.

Results: Mean age was 78±11. Table shows inter-reader and inter-method agreement and correlation.

The correlation between 2 echocardiophers for LVOT measurements was good (rho = 0,77) although not perfect. Out of 43 severe AS, defined as AVA<1 cm2 using TTE in the continuity equation, 18 were reclassified by gated-CT LVOT measurements into moderate AS. This was due to gated-CT LVOT area resulting on average 1.4 cm2 larger than LVOT area by TTE.

Conclusion: LVOT is elliptical and TTE tends to underestimate LVOT area and AVA due to the measurement of the shorter diameter of this ellipse. CT scan can provide more geometrically accurate measurement and requires different cut-offs compared with traditional TTE AVA measurement. By the way, in the current study the LVOT area by CT was on average 38% larger of the LVOT area measured by TTE. Such correcting factor (increase TTE LVOT area by 38%) should apparently be used to assess anatomical true planimetric area to be compared with gated-CT LVOT.

summary tableTTE Inter-reader correlation LVOT area (Spearman rho)0.77TTE reader A vs CT 3-chamber equivalent correlation (Spearman rho)0.49TTE reader B vs CT 3-chamber equivalent correlation (Spearman rho)0.38TTE reader A area vs CT planimetric area correlation (Spearman rho)0.41TTE reader B area vs CT planimetric area correlation (Spearman rho)0.31Mean LVOT Area by TTE reader A3,60SD 0,6038%Mean LVOT Area by CT scan4,99SD 0,98 Abstract P981 Figure.

summary table.

Abstract P981 Figure.