Quantitative assessment of severity of ventricular septal defect by Three-Dimensional reconstruction of color doppler-imaged Vena Contracta and Flow Convergence region

Background - The aim of the present study was to investigate the feasibility and potential value of the computer-controlled, 3D, echocardiographic reconstruction of the color Doppler-imaged vena contracta (CDVC) and the flow convergence (FC) region as a means of accurately and quantitatively estimating the severity of a ventricular septal defect (VSD). Methods and Results - We performed a 3D reconstruction of the CDVC and the FC region in 19 patients with an isolated VSD using an ultrasound system interfaced with a Tomtec computer. The variable asymmetric geometry of the CDVC and the FC region could be 3D-visualized in all patients. The 3D-measured areas of CDVC correlated well with volumetric measurements of the severity of VSD (r=0.97, P<0.001). Regression analysis between the shunt flow rate (calculated from the product of the area of CDVC and the continuous Doppler-derived velocity time integral) and the corresponding reference results (calculated by cardiac catheterization) demonstrated a close correlation (r=0.95, P<0.001). There was also a good correlation between shunt flow rates calculated using the conventional 2D, 1-axis measurement of the FC isovelocity surface area with the hemispheric assumption (r=0.95, P<0.001); shunt flow rates calculated using 3D, 3-axis measurements of the FC region (r=0.97, P<0.01); and reference results by cardiac catheterization. However, the 2D method substantially underestimated the actual shunt flow rate. Conclusions - The 3D reconstruction of the CDVC and the FC region may aid in quantifying the severity of VSD.