
Treatment Difference (Sildenafil – Placebo) 
Statistic 
Sildenafil
Low Dose 
Sildenafil Medium Dose 
Sildenafil High Dose 
Sildenafil Combined Dose 
Mean PAP (mmHg) 
n=39 
n=55 
n=71 
n=165 
Mean difference ±SE 
1.6±3.1 
–3.5±2.7 
–7.3±2.6 
–3.1±2.2 
95% CI 
–4.5, 7.6 
–8.9, 1.9 
–12.4, –2.1 
–7.5, 1.3 
P value^{*} 
0.610 
0.199 
0.006 
0.172 
PVRI (Wood units•m^{2}) 
n=37 
n=51 
n=68 
n=156 
Ratio^{†} 
0.982 
0.819 
0.727 
0.836 
95% CI 
0.802, 1.203 
0.684, 0.981 
0.612, 0.863 
0.720, 0.971 
P value^{*} 
0.859 
0.031 
<0.001 
0.019 
Cardiac index (L/min/m^{2}) 
n=37 
n=51 
n=69 
n=157 
Ratio^{†} 
1.100 
1.043 
1.148 
1.096 
95% CI 
0.963, 1.258 
0.925, 1.176 
1.026, 1.286 
0.994, 1.210 
P value^{*} 
0.161 
0.486 
0.017 
0.066 
CI=confidence interval; PVRI=pulmonary vascular resistance index; PAP=pulmonary artery pressure; STARTS1=Sildenafil in TreatmentNaïve Children, Aged 1 to 17
Years, With Pulmonary Arterial Hypertension.
^{*}With the exception of the primary comparison, P values should be interpreted descriptively because no adjustments were made for multiple comparisons.
^{†}Because PVRI and cardiac index data were logtransformed before analysis, comparisons are presented as ratios (active/placebo) when backtransformed.
N=56, 52 and 55 for the placebo group for mean PAP, PVRI, and cardiac index, respectively. 