Effect of left ventricular outflow on flow convergence region on the left septal surface in ventricular septal defect

The corrected shunt flow rate (Fc) and corrected defect orifice area (Ac) were calculated by modified equation F = 2 pi R2 (NL-VLVOT x Sin theta) in 23 patients with single membranous ventricular septal defect, in order to correct the effect of left ventricular outflow on flow convergence region on the left septal surface. The results indicated that Fc was closely correlated with Qp-Qs, and Qp/Qs measured by pulsed wave Doppler (r = 0.95 and r = 0.81 respectively, P < 0.001). And the correlation between Ac and the diameter of defect (Dd) measured directly in two-dimensional views was better than that between uncorrected defect orifice area (A) and the Dd (r = 0.98 and 0.69, respectively, P < 0.001). The shunt flow rate calculated by ideal equation F = 2 pi R2 x NL overestimated the actual shunt flow rate in ventricular septal defect, especially in membranous type. Our study concluded that Fc can be used for a more accurate evaluation of the shunt severity of ventricular septal defect.