The International BPA Registry demonstrated that balloon pulmonary angioplasty (BPA) leads to significant clinical improvements, including better hemodynamics, oxygen saturation, WHO functional class, 6-minute walk distance, NT-proBNP levels, and reduced dyspnea. These improvements translated into practical benefits such as enhanced quality of life, fewer hospitalizations, decreased oxygen dependency, and reduced use of pulmonary hypertension (PH) medications. Complications were reported in 11.3% of BPA sessions and in 33.9% of patients, with hemoptysis being the most common. Importantly, there were no deaths within 30 days of the procedure. Complication rates were generally lower in Japan compared to Europe and the United States, likely due to advanced technical refinement and structured proctoring programs. The registry included 500 patients from 18 centers across three continents. Differences between Japanese and Caucasian patients were observed, influenced by anthropometric factors, procedural techniques, and treatment strategies. Japanese centers typically performed shorter intervals between BPA sessions, used less radiation and contrast, and treated more lesions per session. Hemodynamic assessment conducted around six months after the final BPA showed a 57% reduction in pulmonary vascular resistance (PVR), with final values comparable to those achieved after pulmonary endarterectomy (PEA). Post-interventional pulmonary hypertension, defined as a mean pulmonary artery pressure of at least 25 mmHg, persisted in approximately half of the patients, similar to rates seen after PEA. This raised questions regarding the adequacy of current PH definitions following mechanical interventions. Most patients were on PH medications at the start of BPA treatment, and over half remained on these therapies after BPA. While PH medications did not significantly influence PVR reduction, they did enhance improvements in cardiac output, suggesting BPA primarily reduces pressure rather than directly increasing cardiac output. Nevertheless, many patients continued medications post-procedure, highlighting uncertainty about optimal medical management after BPA. Three-year survival following BPA was 94.1%, comparable to outcomes reported in Japan and France. Mortality predictors included higher WHO functional class, elevated NT-proBNP, and a longer interval between diagnosis and initiation of BPA treatment. The registry faced several limitations, including reliance on an older PH definition, incomplete follow-up right heart catheterization data due to the COVID-19 pandemic, and insufficient detail regarding medication effects and complication-related hospitalizations.

In conclusion, BPA demonstrated meaningful clinical improvements with low short-term mortality and acceptable complication rates. These outcomes were achieved through a multidisciplinary, patient-centered approach. However, uncertainties remain regarding the optimal use of PH medications post-BPA and the need for refining PH definitions after interventional treatment. Future research should address these gaps to optimize BPA outcomes.