NPPB and pulmonary arterial hypertension: In the CTD-PAH subgroup, NT-proBNP levels decreased significantly with ambrisentan treatment at week 12 (− 1156.8 ng/L, p < 0.001) and week 24 (− 1095.5 ng/L, p < 0.001) compared to baseline (mean 1837.5 ng/L).