The purpose of this study was to test the effectiveness of a new Doppler index combining systolic and diastolic time intervals (the Tei index) in the prospective assessment of ventricular function and pulmonary circulation in a newborn piglet model with hypoxic pulmonary hypertension during inhaled nitric oxide (NO). Piglets were prepared for the experiments under normal air, hypoxia, and hypoxia-with-inhaled-NO conditions. Complete two-dimensional Doppler echocardiographic examinations were performed in each condition. The right-ventricle (RV) Tei index increased with hypoxia and decreased following the inhalation of NO. Furthermore, there was a direct correlation between the individual changes in the RV Tei index and individual changes in mean pulmonary arterial pressure in each condition. We conclude that the Tei index is useful for assessing cardiac function and pulmonary circulation in hypoxic pulmonary hypertension during inhaled NO. These results suggest that the Tei index provides an objective assessment of persistent pulmonary hypertension of the newborn.