Insights into balloon pulmonary angioplasty and the WHO functional class of chronic thromboembolic pulmonary hypertension patients: findings from the CTEPH AC registry

Advances in chronic thromboembolic pulmonary hypertension (CTEPH) treatment have improved prognosis, shifting focus towards symptom management. This study aimed to identify factors influencing the World Health Organization functional class (WHO-FC) in CTEPH patients. The CTEPH AC registry is a prospective, multicenter database from 35 Japanese institutions, analyzing data from August 2018 to July 2023. We examined factors associated with achieving WHO-FC I and WHO-FC changes over time in 1,270 patients. Significant factors for WHO-FC I achievement included male sex (odds ratio: 1.86, p = 0.019), age (0.98, p = 0.007), pulmonary vasodilator use (0.51, p = 0.001), post-balloon pulmonary angioplasty (BPA) (1.93, p = 0.010), lower mean pulmonary arterial pressure (0.94, p = 0.004), and lower pulmonary vascular resistance (PVR) (0.78, p = 0.006). Multivariate analysis showed that WHO-FC improvement correlated with male sex, baseline PVR, and BPA during follow-up. WHO-FC deterioration was associated with cancer, history of pulmonary endarterectomy and/or BPA at registration, bleeding risks, and thyroid disease or hormone therapy. BPA implementation is closely linked to symptomatic improvement and achieving WHO-FC I, while symptom worsening is often associated with patient-specific, difficult-to-control conditions.