The Doppler-derived ratio of TRV/TVIRVOT has been previously used to measure pulmonary vascular resistance (PVR). The applicability of this ratio in measuring PVR in patients with congenital heart disease has not been adequately evaluated. Aim: To measure PVR in patients with congenital heart disease using Doppler echocardiography and compare with invasively derived PVR. Method: Twenty patients with post-tricuspid shunt lesions who were planned to undergo cardiac catheterization as a part of their management were enrolled for the study. The formula, PVR (WU) = 10x TRV/ TVIRVOT was used to calculate PVR non-invasively. Peak tricuspid regurgitation velocity (TRV) and the time velocity integral of the right ventricular outflow tract (TVIRVOT ) were measured using continuous wave and pulsed-wave Doppler respectively. PVR was also determined by cardiac catheterization. The peak systolic velocity of the lateral wall of tricuspid annulus (tSm) was also measured by tissue Doppler and correlated with invasively determined PVR. Results: There was a significant correlation between the ratio TRV/TVI RVOT and PVR CATH r=0.635(p=0.003). This correlation was better in the subgroup with lower PVR r=0.817(PVR<6WU). However, there was a significant difference between the mean PVR obtained by echocardiography and catheterization, mean PVR 1.8 WU vs 6.9 WU respectively (p<0.0001). Bland-Altman analysis showed very wide limits of agreement which was clinically unacceptable. There was no correlation between tSm and invasively determined PVR. Conclusion: Although there is positive correlation between the TRV/TVIRVOT and invasively determined PVR, this ratio cannot be reliably used to estimate the PVR in post-tricuspid shunts.