6-min walk distance; 6MWD; B-type natriuretic peptide; BNP; CHD-PAH; CI; CMR; EqCO(2); FC; HIV-PAH; IPAH; N-terminal pro­B-type natriuretic peptide; NIH; NT-proBNP; NYHA; National Institutes of Health; New York Heart Association; PAH; PAP; PH; PoPH; RAP; RV; RVEDVI; SLE-PAH; SSc-PAH; SvO(2); cardiac index; cardiac magnetic resonance; functional class; hemodynamics; idiopathic pulmonary arterial hypertension; mixed venous oxygenation; pulmonary arterial hypertension; pulmonary arterial hypertension related to congenital heart disease; pulmonary arterial hypertension related to human immunodeficiency virus infection; pulmonary arterial hypertension related to portal hypertension; pulmonary arterial hypertension related to scleroderma; pulmonary arterial hypertension related to systemic lupus erythematosus; pulmonary artery pressure; pulmonary hypertension; right atrial pressure; right ventricular; right ventricular end-diastolic volume index; right ventricular function; ventilatory equivalent for carbon dioxide