Evaluate The Clinical Effectiveness, Safety And Tolerability Of Sildenafil Used In Doses ≥20mg TID For The Treatment Of Pulmonary Arterial Hypertension

• Change From Baseline in 6-Minute Walk Distance (6MWD) at Year 1 [ Time Frame: Baseline, Year 1 ] [ Designated as safety issue: No ]
  6MWD was the distance that a participant could walk in 6 minutes. Participants were asked to perform the test at a pace that was comfortable to them, with as many breaks as they needed.
  
  
• Change From Baseline in 6-Minute Walk Distance (6MWD) at Year 2 [ Time Frame: Baseline, Year 2 ] [ Designated as safety issue: No ]
  6MWD was the distance that a participant could walk in 6 minutes. Participants were asked to perform the test at a pace that was comfortable to them, with as many breaks as they needed.
  
  
• Change From Baseline in 6-Minute Walk Distance (6MWD) at Year 3 [ Time Frame: Baseline, Year 3 ] [ Designated as safety issue: No ]
  6MWD was the distance that a participant could walk in 6 minutes. Participants were asked to perform the test at a pace that was comfortable to them, with as many breaks as they needed.
  
  
• Change From Baseline in 6-Minute Walk Distance (6MWD) at Year 4 [ Time Frame: Baseline, Year 4 ] [ Designated as safety issue: No ]
  6MWD was the distance that a participant could walk in 6 minutes. Participants were asked to perform the test at a pace that was comfortable to them, with as many breaks as they needed.
  
  

• Change From Baseline in New York Heart Association, World Health Organization (NYHA/WHO) Functional Class in Participants With Pulmonary Arterial Hypertension (PAH) at Year 1, 2, 3 and 4 [ Time Frame: Baseline, Year 1, 2, 3, 4 ] [ Designated as safety issue: No ]
  NYHA/WHO functional classification for PAH range from Class I (no limitation in physical activity, no dyspnea with normal activity) to Class IV (can not perform a physical activity without any symptoms, dyspnea at rest). Improvement=reduction in functional class, deterioration = increase in functional class, no change = no change in functional class. Number of participants in each functional class was reported.
  
  
• Change From Baseline in Right Atrial Pressure (RAP) at Year 1, 2, 3 and 4 [ Time Frame: Baseline, Year 1, 2, 3, 4 ] [ Designated as safety issue: No ]
  RAP was measured using a pressure transducer positioned at the mid-axillary line with the participant in the supine position.
  
  
• Change From Baseline in Mean Pulmonary Arterial Pressure (mPAP) at Rest at Year 1, 2, 3 and 4 [ Time Frame: Baseline, Year 1, 2, 3, 4 ] [ Designated as safety issue: No ]
  mPAP was measured using a pressure transducer positioned at the mid-axillary line with the participant in the supine position.
  
  
• Change From Baseline in Pulmonary Vascular Resistance (PVR) at Year 1, 2, 3 and 4 [ Time Frame: Baseline, Year 1, 2, 3, 4 ] [ Designated as safety issue: No ]
  PVR: calculated by subtracting PCWP from mPAP and dividing by cardiac output in pulmonary circulation (COpulm).
  
  
• Change From Baseline in Cardiac Index (CI) at Year 1, 2, 3 and 4 [ Time Frame: Baseline, Year 1, 2, 3, 4 ] [ Designated as safety issue: No ]
  CI: calculated as COsys divided by BSA.
  
  
• Change From Baseline in Pulmonary Capillary Wedge Pressure (PCWP) at Year 1, 2, 3 and 4 [ Time Frame: Baseline, Year 1, 2, 3, 4 ] [ Designated as safety issue: No ]
  PCWP was measured by pulmonary artery catheterization and provided an indirect measure of left atrial pressure.
  
  
• Change From Baseline in Borg Dyspnea Index at Year 1, 2, 3 and 4 [ Time Frame: Baseline, Year 1, 2, 3, 4 ] [ Designated as safety issue: No ]
  Borg dyspnea scale: 10-point scale where following scores stands for severity of dyspnea: 0=no breathlessness at all;0.5=very very slight (just noticeable); 1=very slight; 2=slight breathlessness; 3=moderate; 4=some what severe; 5=severe; 7=very severe breathlessness; 9=very very severe (almost maximum) and 10=maximum.
  
  

The study design proposed is a retrospective chart review going back five years (01 April 2006 estimate) from the time of study initiation (31 March 2011 estimate). Within this five-year period, study index will occur the first time an adult patient begins sildenafil for the treatment of PAH for a period of at least three months. The patient has to be taking sildenafil at doses ≥ 20mg tid for the treatment of PAH.