A cohort study in HigAshi-nippon of Pulmonary hyPertensIoN in systEmic SclerosiS (HAPPINESS study): protocol and baseline data for an observational study.

Background: Pulmonary hypertension (PH) is the leading cause of death among patients with systemic sclerosis (SSc). Recently, early therapeutic intervention to improve the prognosis was suggested, and the definition of PH was recently revised by lowering the cut-off value of mean pulmonary arterial pressure (mPAP) from ≥ 25 to > 20 mmHg. However, the optimal threshold for therapeutic intervention remains unclear. We aim to evaluate the prognosis of patients with SSc and its relationship with mPAP.

Methods: For this non-interventional retrospective and prospective cohort study, we enrolled patients with SSc or scleroderma spectrum disorders accompanied by other connective tissue diseases who underwent right heart catheterization (RHC) for suspected PH from 2010 to 2023. The date of the first RHC was defined as the baseline. Enrolled patients were classified into three groups based on their mPAP at the first RHC (≤ 20, 21-24, and ≥ 25 mmHg) and are being observed from baseline up to three years. The primary endpoint is the time between the first RHC and the first hospitalisation or death due to worsening PH.

Results: This study was approved by the Ethics Committee of Hokkaido University Hospital. A total of 229 patients were enrolled from 12 participating centres, with 41 prospectively followed up and 188 retrospectively followed up. The number of patients in each group (an mPAP of ≤ 20, 21-24, and ≥ 25 mmHg) is 79, 26, and 124, respectively. The observation is expected to be completed by December 2026. Findings will be disseminated at scientific conferences, peer-reviewed journals.

Conclusions: The findings of this study that we will obtain are expected to provide important information that will lead to improvements in the diagnosis of PH and the prognosis of patients.

Trial Registration: This study was approved by the Ethics Committee of Hokkaido University Hospital (approval number 022-0109). It has been registered in the Japan Registry of Clinical Trials as jRCT1010220025 since November 7, 2022.