mg: milligrams, BID: twice a day, TID: three times a day, vs: versus, N: total number of patients who received the study drug, N with PH: number of patients with pulmonary hypertension, PH: pulmonary hypertension, PAP: pulmonary artery pressure, CO: cardiac output, PVR: pulmonary vascular resistance, SpO2: oxygen saturation by pulse oximetry, PaO2: arterial oxygen tension, 6MWD: six-minute walk distance, m: meters, NA: not available or not applicable, r + e: rest and exercise, Δ: change, r: rest, e: exercise.