NPPB and pulmonary arterial hypertension: In the five patients with PAH, the mean ± standard deviation peak tricuspid regurgitant pressure gradient was 51 ± 13 mmHg (range, 39 to 70 mmHg; median, 50 mmHg) on echocardiography within 6 months of the present study, and the mean plasma brain natriuretic peptide level was 639 ± 623 pg/ml (range, 107 to 1,312 pg/ml; median, 568 pg/ml) at the time of this study.