Procedural Volume and Outcomes After Balloon Pulmonary Angioplasty for Chronic Thromboembolic Pulmonary Hypertension

Background Balloon pulmonary angioplasty (BPA) is an established treatment for inoperable chronic thromboembolic pulmonary hypertension; however, volume-outcome relationships remain unclear. Objectives This study examined the relationship between hospital and operator volume and BPA-related complications using a nationwide registry. Methods The authors analyzed 5,403 BPA sessions for chronic thromboembolic pulmonary hypertension in the Japanese Structural Heart Diseases registry between 2021 and 2024. Procedural volume was defined as BPA sessions performed during the preceding 3 years. The primary outcome was a composite of BPA-related complications. Mixed-effects logistic regression models accounted for hospital and operator clustering. Results BPA-related complications occurred in 751 sessions (13.9%). Severe complications were uncommon, with 3 periprocedural deaths, 6 requiring invasive mechanical ventilation, and 7 requiring extracorporeal membrane oxygenation. The main categorical analysis revealed that hospital BPA volume ≥150 sessions/3 years was associated with higher odds of BPA-related complications (adjusted OR: 1.60; 95% CI: 1.08-2.36; P = 0.019), whereas operator volume was not independently associated. When hospital and operator volumes were modeled separately as continuous variables, each was associated with complications. However, neither remained independently associated after mutual adjustment. In an analysis restricted to 135 complications considered less susceptible to differences in ascertainment, no statistically significant association was detected for either volume measure, although the smaller number of events limited statistical precision. Conclusions BPA-related complications demonstrated a complex relationship with procedural volume, while severe complications remained uncommon. The attenuation of hospital- and operator-level associations after mutual adjustment suggests that procedural volume alone may not adequately characterize BPA safety. Further studies incorporating lesion- and procedural-level characteristics and standardized complication ascertainment are warranted.