QUANTITATIVE ESTIMATION OF SHUNT IN ATRIAL SEPTAL DEFECTS BY TRANSESOPHAGEAL IMAGING OF THE FLOW CONVERGENCE REGION.

In this study we attempted a qauntitative analysis of atrial septal defect (ASD) shunt by means of multiplane transesophageal echocardiography. We studied 18 ASD patients (pts), aged 13 to 69 yrs (median 32,3 yrs), and considered flow convergence signal as a marker for shunt flow. The maximum axial distance of the first color alias ASD flow convergence region (FCR) from the left atrial defect border was measured. Using the hemispherical isovelocity surface assumption peak shunt flow (Q) was calculated (ml/s) as follows: Q=2r2Va, where r (cm) is the maximal distance of the flow convergence and Va (cm/s) is the aliasing velocity used for imaging of the flow convergence. The same peak shunt flow rate was also measured as the product of the CW or high PRF pulsed Doppler peak velocity of the shunt flow and the corresponding smallest diameter of the defect. Contrast echo was performed using saline infusion and videointensity signal was used to calculate shunt flow. Peak shunt flow rates calculated by the flow convergence method correlated well with those derived from CW or PW Doppler velocity-time integral (y=0.93 x – 6.1, r=0.95, p<0.0001, SEE=15 ml/s) and those derived from contrast echo (y=0.98 x – 6.8, r=0.93, p