Abstract 3368: Assessing Aortic Valve Area in Aortic Stenosis by Continuity Equation: A Novel Approach using Real-time Three Dimensional Echocardiography
Background: Two dimensional echocardiographic (2DE) continuity-equation derived aortic valve area (AVA) in pts with aortic stenosis (AS) relies on nonsimultaneous measurement of left ventricular outflow track (LVOT) velocity and geometric assumptions for area calculation. These can amplify error, especially in the presence of upper septal hypertrophy (USH). We hypothesized that real-time three dimensional echocardiography (RT3DE) can improve accuracy of AVA calculation by directly measuring LVOT stroke volume (SV) in one window.
Methods: RT3DE color Doppler incorporating LVOT and 2DE were acquired in 44 AS pts (75±12 yrs) prospectively. Flow velocity profile from a gaussian sampling curve placed orthogonal to LVOT was obtained and SV derived (Tomtec Imaging). Agreement between RT3DE and 2DE and predictors of discrepancies (>0.2 cm2 in AVA) were analysed. Validation of LVOT cardiac output (CO) by aortic flow probe was performed in an open-chest sheep model with balloon inflation of septum to vary the LVOT geometry.
Results: There was only modest correlation between 2DE and RT3DE AVA (r=0.44, P=0.003; difference -0.14±0.35 cm2). Significant discrepancies were predicted solely by the presence of USH in multivariate analysis (OR=30, 95%CI 5–200; P<0.001). When CO was measured in experimentally distorted LVOT geometry in sheep, RT3DE correlated better with flow probe assessment (r=0.96, P<0.001) than 2DE (r=0.71, P=0.006). The difference of flow probe data with 2DE and RT3DE were -0.50±1.1 and 0.01±0.18 L/min respectively (Fig. 1⇓⇓).
Conclusion: RT3DE color Doppler-derived LVOT SV in the calculation of AVA by continuity equation appears accurate even in the presence of USH.