| 
      VO2=oxygen consumption.
    Numbers represent the percentage of patients having less than or equal to the specified percentage change from baseline for each parameter.
        |  | Peak    VO2, mL/kg/min | Mean    pulmonary artery pressure, mmHg | Pulmonary    vascular resistance index, Wood units•m2 | Cardiac    index, L/min/m2 |  
        | Change    from Baseline | n | 0 | 1 | 2 | n | 0 | 10 | 20 | n | 0 | 10 | 20 | n | 0 | 1 | 2 |  
        | Placebo | 29 | 55.2 | 58.6 | 72.4 | 56 | 50.0 | 82.1 | 89.3 | 50 | 48.0 | 86.0 | 98.0 | 52 | 61.5 | 88.5 | 94.2 |  
        | All    Sildenafil Doses Combined | 77 | 24.7 | 37.7 | 57.1 | 165 | 67.3 | 87.3 | 97.6 | 152 | 64.5 | 90.8 | 96.7 | 154 | 47.4 | 74.7 | 92.2 |  
        | Low Dose | 24 | 37.5 | 50.0 | 70.8 | 39 | 48.7 | 76.9 | 92.3 | 36 | 52.8 | 86.1 | 91.7 | 37 | 48.6 | 78.4 | 94.6 |  
        | Medium Dose | 26 | 19.2 | 34.6 | 50.0 | 55 | 74.5 | 85.5 | 98.2 | 49 | 65.3 | 89.8 | 98.0 | 49 | 51.0 | 75.5 | 91.8 |  
        | High Dose | 27 | 18.5 | 29.6 | 51.9 | 71 | 71.8 | 94.4 | 100.0 | 67 | 70.1 | 94.0 | 98.5 | 68 | 44.1 | 72.1 | 91.2 |  |