The 6-minute walk distance (6MWD) test was conducted according to the American Thoracic Society guidelines (ATS statement: guidelines for the six-minute walk test. Am J Respir Crit Care Med 2002; 166(1):111-117.).

All assessments of efficacy were performed using the randomized analysis set; subjects were allotted to an individual dose group based upon their randomized treatment assignment in the 2 prior studies (NCT00423748 or NCT00423202) or in the extension study. The LOCF method of imputation was used; only postbaseline observations were carried forward.

The primary endpoint of this study is the incidence and severity of adverse events associated with long-term exposure to AMB in participants with PAH. The most frequently occurring adverse events (occurring in 15% or more of the participants in the combined group) are presented, by severity, that began after entering this extension study. Adverse events that were serious are included. Adverse events are coded according to the Medical Dictionary for Regulatory Activities (MedDRA) Version 6.1 and are presented by MedDRA preferred term. Severity was graded as follows: mild (AE did not interfere with routine activities; subject may have experienced slight discomfort), moderate (AE interfered with routine activities; subject may have experienced significant discomfort), and severe (AE made it impossible to perform routine activities; subject may have experienced intolerable discomfort or pain).

Safety Analysis Set: Includes all participants who received at least 1 dose of AMB in one of the 2 prior studies (NCT00423748 or NCT00423202) or in the current extension study. Treatment group assignments for the safety analysis set were based upon the highest dose of AMB received at any time during the parent or extension studies.

The 6-minute walk distance (6MWD) test was conducted according to the American Thoracic Society guidelines (ATS statement: guidelines for the six-minute walk test. Am J Respir Crit Care Med 2002; 166(1):111-117.). Missing values were imputed using LOCF method based on post-baseline observations. Baseline (BL) values from the screening/randomization visit of the 2 prior studies defined the BL of this long-term analysis for those receiving ambrisentan in the prior studies. The Screening/Randomization Visit of the present study was the BL for subjects receiving placebo in the prior studies.

All assessments of efficacy were performed using the randomized analysis set; subjects were allotted to an individual dose group based upon their randomized treatment assignment in the 2 prior studies (NCT00423748 or NCT00423202) or in the extension study. The LOCF method of imputation was used; only postbaseline observations were carried forward.

The 6-minute walk distance (6MWD) test was conducted according to the American Thoracic Society guidelines (ATS statement: guidelines for the six-minute walk test. Am J Respir Crit Care Med 2002; 166(1):111-117.). The last-observation-carried-forward (LOCF) imputation method was used. Baseline (BL) values from the screening/randomization visit of the 2 prior studies defined the BL of this long-term analysis for those receiving AMB in the prior studies. The Screening/Randomization Visit of the present study was the BL for subjects receiving placebo in the prior studies.

All assessments of efficacy were performed using the randomized analysis set; subjects were allotted to an individual dose group based upon their randomized treatment assignment in the 2 prior studies (NCT00423748 or NCT00423202) or in the extension study. The LOCF method of imputation was used; only postbaseline observations were carried forward.

The 6-minute walk distance (6MWD) test was conducted according to the American Thoracic Society guidelines (ATS statement: guidelines for the six-minute walk test. Am J Respir Crit Care Med 2002; 166(1):111-117.). The last-observation-carried-forward (LOCF) imputation method was used. Baseline (BL) values from the screening/randomization visit of the 2 prior studies defined the BL of this long-term analysis for those receiving AMB in the prior studies. The Screening/Randomization Visit of the present study was the BL for subjects receiving placebo in the prior studies.

All assessments of efficacy were performed using the randomized analysis set; subjects were allotted to an individual dose group based upon their randomized treatment assignment in the 2 prior studies (NCT00423748 or NCT00423202) or in the extension study. The LOCF method of imputation was used; only postbaseline observations were carried forward.

Thoracic Society guidelines (ATS statement: guidelines for the six-minute walk test. Am J Respir Crit Care Med 2002; 166(1):111-117.). The last-observation-carried-forward (LOCF) imputation method was used. Baseline (BL) values from the screening/randomization visit of the 2 prior studies defined the BL of this long-term analysis for those receiving AMB in the prior studies. The Screening/Randomization Visit of the present study was the BL for subjects receiving placebo in the prior studies.

All assessments of efficacy were performed using the randomized analysis set; subjects were allotted to an individual dose group based upon their randomized treatment assignment in the 2 prior studies (NCT00423748 or NCT00423202) or in the extension study. The LOCF method of imputation was used; only postbaseline observations were carried forward.

Borg Dyspnea Index is a measure of perceived shortness of breath: 0 units on a scale (none) to 10 units on a scale (maximum breathlessness).

All assessments of efficacy were performed using the randomized analysis set, such that subjects were allotted to an individual dose group based upon their randomized treatment assignment in the 2 prior studies (NCT00423748 or NCT00423202) or in the current extension study.

Borg Dyspnea Index is a measure of perceived shortness of breath: 0 units on a scale (none) to 10 units on a scale (maximum breathlessness). Baseline (BL) values from the screening/randomization visit of the 2 prior studies defined the BL of this long-term analysis for those receiving ambrisentan in the prior studies. The Screening/Randomization Visit of the present study was the BL for subjects receiving placebo in the prior studies.

All assessments of efficacy were performed using the randomized analysis set; subjects were allotted to an individual dose group based upon their randomized treatment assignment in the 2 prior studies (NCT00423748 or NCT00423202) or in the extension study. The LOCF method of imputation was used; only postbaseline observations were carried forward.

Borg Dyspnea Index is a measure of perceived shortness of breath: 0 units on a scale (none) to 10 units on a scale (maximum breathlessness). Baseline (BL) values from the screening/randomization visit of the 2 prior studies defined the BL of this long-term analysis for those receiving AMB in the prior studies. The Screening/Randomization Visit of the present study was the BL for subjects receiving placebo in the prior studies.

All assessments of efficacy were performed using the randomized analysis set; subjects were allotted to an individual dose group based upon their randomized treatment assignment in the 2 prior studies (NCT00423748 or NCT00423202) or in the extension study. The LOCF method of imputation was used; only postbaseline observations were carried forward.

Borg Dyspnea Index is a measure of perceived shortness of breath: 0 units on a scale (none) to 10 units on a scale (maximum breathlessness). Baseline (BL) values from the screening/randomization visit of the 2 prior studies defined the BL of this long-term analysis for those receiving AMB in the prior studies. The Screening/Randomization Visit of the present study was the BL for subjects receiving placebo in the prior studies.

All assessments of efficacy were performed using the randomized analysis set; subjects were allotted to an individual dose group based upon their randomized treatment assignment in the 2 prior studies (NCT00423748 or NCT00423202) or in the extension study. The LOCF method of imputation was used; only postbaseline observations were carried forward.

WHO Classes: I) pulmonary hypertension (PH); ordinary physical activity not limited or causes increased dyspnea, fatigue, chest pain, or presyncope. II) PH; ordinary physical activity mildly limited and causes increased dyspnea, fatigue, chest pain, or presyncope; comfortable at rest. III) PH; physical activity markedly limited and less than ordinary physical activity causes increased dyspnea, fatigue, chest pain, or presyncope; comfortable at rest. IV) PH; physical activity causes symptoms; signs of right heart failure; dyspnea/fatigue possible at rest.

All assessments of efficacy were performed using the randomized analysis set, such that subjects were allotted to an individual dose group based upon their randomized treatment assignment in the 2 prior studies (NCT00423748 or NCT00423202) or in the current extension study.

WHO Classes: I) pulmonary hypertension (PH); ordinary physical activity not limited or causes increased dyspnea, fatigue, chest pain, or presyncope. II) PH; ordinary physical activity mildly limited and causes increased dyspnea, fatigue, chest pain, or presyncope; comfortable at rest. III) PH; physical activity markedly limited and less than ordinary physical activity causes increased dyspnea, fatigue, chest pain, or presyncope; comfortable at rest. IV) PH; physical activity causes symptoms; signs of right heart failure; dyspnea/fatigue possible at rest.

All assessments of efficacy were performed using the randomized analysis set; subjects were allotted to an individual dose group based upon their randomized treatment assignment in the 2 prior studies (NCT00423748 or NCT00423202) or in extension study. Missing values imputed using LOCF based on post-baseline observations.

WHO Classes: I) pulmonary hypertension (PH); ordinary physical activity not limited or causes increased dyspnea, fatigue, chest pain, or presyncope. II) PH; ordinary physical activity mildly limited and causes increased dyspnea, fatigue, chest pain, or presyncope; comfortable at rest. III) PH; physical activity markedly limited and less than ordinary physical activity causes increased dyspnea, fatigue, chest pain, or presyncope; comfortable at rest. IV) PH; physical activity causes symptoms; signs of right heart failure; dyspnea/fatigue possible at rest.

All assessments of efficacy were performed using the randomized analysis set; subjects were allotted to an individual dose group based upon their randomized treatment assignment in the 2 prior studies (NCT00423748 or NCT00423202) or in extension study. Missing values were imputed using LOCF based on post-baseline observations.

WHO Classes: I) pulmonary hypertension (PH); ordinary physical activity not limited or causes increased dyspnea, fatigue, chest pain, or presyncope. II) PH; ordinary physical activity mildly limited and causes increased dyspnea, fatigue, chest pain, or presyncope; comfortable at rest. III) PH; physical activity markedly limited and less than ordinary physical activity causes increased dyspnea, fatigue, chest pain, or presyncope; comfortable at rest. IV) PH; physical activity causes symptoms; signs of right heart failure; dyspnea/fatigue possible at rest.

All assessments of efficacy were performed using the randomized analysis set; subjects were allotted to an individual dose group based upon their randomized treatment assignment in the 2 prior studies (NCT00423748 or NCT00423202) or in the extension study. Missing values were imputed using LOCF based on post-baseline observations.

The 8 scales of the SF-36 Health Survey measured included physical functioning, role physical, bodily pain, general health, vitality, social functioning, role-emotional, and mental health, and the summary measures included physical health and mental health. Scores for each scale are transformed and the transformed scores range from 0 (worst health) to 100 (best health). The scores are then standardized with the 1998 General United States (US) population mean and standard deviation (SD). Finally, the scores are transformed to the norm-based scoring with a mean of 50 and SD of 10.

All participants were combined into one group for this analysis (all doses) and an observed-case approach was used.

The 8 scales of the SF-36 Health Survey measured included physical functioning, role physical, bodily pain, general health, vitality, social functioning, role-emotional, and mental health, and the summary measures included physical health and mental health. Scores for each scale are transformed and the transformed scores range from 0 (worst health) to 100 (best health). The scores are then standardized with the 1998 General US population mean and SD. Finally, the scores are transformed to the norm-based scoring with a mean of 50 and SD of 10.

All participants were combined into one group for this analysis (all doses) and an observed-case approach was used.

The 8 scales of the SF-36 Health Survey measured included physical functioning, role physical, bodily pain, general health, vitality, social functioning, role-emotional, and mental health, and the summary measures included physical health and mental health. Scores for each scale are transformed and the transformed scores range from 0 (worst health) to 100 (best health). The scores are then standardized with the 1998 General US population mean and SD. Finally, the scores are transformed to the norm-based scoring with a mean of 50 and SD of 10.

All participants were combined into one group for this analysis (all doses) and an observed-case approach was used.

The 8 scales of the SF-36 Health Survey measured included physical functioning, role physical, bodily pain, general health, vitality, social functioning, role-emotional, and mental health, and the summary measures included physical health and mental health. Scores for each scale are transformed and the transformed scores range from 0 (worst health) to 100 (best health). The scores are then standardized with the 1998 General US population mean and SD. Finally, the scores are transformed to the norm-based scoring with a mean of 50 and SD of 10.

All participants were combined into one group for this analysis (all doses) and an observed-case approach was used.

Clinical worsening of PAH was defined as the time from randomization to ambrisentan therapy to the first occurrence of death, lung transplantation, hospitalization for PAH, atrial septostomy, addition of approved prostanoid therapy, study withdrawal due to the addition of other clinically approved PAH therapeutics, or study withdrawal due to 2 or more early escape criteria (for subjects randomized to AMB in NCT00423748 or NCT00423202). Results are presented as the Kaplan-Meier estimate (% probability) of not having clinical worsening after a given time.

All assessments of efficacy were performed using the randomized analysis set, such that subjects were allotted to an individual dose group based upon their randomized treatment assignment in the 2 prior studies (NCT00423748 or NCT00423202) or in the current extension study.

Treatment failure was defined as the time from randomization to ambrisentan therapy to the first occurrence of death, lung transplantation, addition of approved prostanoid therapy, study withdrawal due to the addition of other clinically approved PAH therapeutics, or study withdrawal due to 2 or more early escape criteria (for subjects randomized to ambrisentan in NCT00423748 or NCT00423202). Results are presented as the Kaplan-Meier estimate (% probability) of not having treatment failure after a given time.

All assessments of efficacy were performed using the randomized analysis set, such that subjects were allotted to an individual dose group based upon their randomized treatment assignment in the 2 prior studies (NCT00423748 or NCT00423202) or in the current extension study.

Long-term survival was defined as the time from initiation of active treatment to death. Results are presented as the Kaplan-Meier estimate (% probability) of survival after a given time.

All assessments of efficacy were performed using the randomized analysis set, such that subjects were allotted to an individual dose group based upon their randomized treatment assignment in the 2 prior studies (NCT00423748 or NCT00423202) or in the current extension study.

The number of participants with serum alanine aminotransferase (ALT) and serum aspartate aminotransferase (AST) falling into the following categories: >3.0 and </= 5.0 x ULN, >5.0 and </= 8.0 x ULN, and >8.0 x ULN. Includes the highest value per participant across all visits as well as values from early termination visits.

Safety Analysis Set: Includes all participants who received at least 1 blinded dose of AMB in one of the 2 prior studies (NCT00423748 or NCT00423202) or in the current extension study.