The Opsumit Users registry (OPUS; NCT02126943) was developed to characterize the safety profile of Opsumit and to describe clinical characteristics and outcomes of patients newly treated with Opsumit in the post-marketing setting. It is expected that the recruitment target of the OPUS registry cannot be achieved within the planned time period (5000 Opsumit new users by October 2018). The OrPHeUS study is designed to supplement the OPUS registry with retrospectively identified first-time Opsumit users in order to achieve the desired sample size.

Inclusion Criteria:

• Patients who initiated Opsumit for the first time between 19 October 2013 and 31 December 2016 (inclusive)
• Patients whose medical charts are available for data collection

Exclusion Criteria:

• Patient participation in the OPUS registry
• Patient participation in any clinical trial involving Opsumit treatment or macitentan investigational product

Patients who initiated Opsumit for the first time between 19 October 2013 and 31 December 2016 (inclusive) are eligible for OrPHeUS (i.e., eligibility period).