Figure 7: Peak pressure gradient across RV-RA at 8-weeks. We evaluated tricuspid regurgitation by the color Doppler method and recorded the flow profile of TR from which maximum regurgitant velocity was measured and pulmonary artery pressure was estimated using the modified Bernoulli equation from the four-chamber view. Tricuspid regurgitation was recognized in many surviving rats. Estimated pulmonary artery pressure in a tadalafil+citrulline group seems to be lower than those in other groups. But there were no significant differences.