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Background Right ventricular (RV) pressure overload is directly related to the increase in mortality in pulmonary hypertension. Pulmonary arterial compliance (CPA; stroke volume/pulmonary pulse pressure) was reported to be an independent determinant of RV systolic afterload in patients with pulmonary arterial hypertension (PAH). Recently, balloon pulmonary angioplasty (BPA) has been reported to reduce mean pulmonary artery pressure (mPAP) and pulmonary vascular resistance (RPA) in patients with inoperable chronic thromboembolic pulmonary hypertension (CTEPH). However, the effects of BPA on CPA remain unclear. Purpose The aim of this study was to investigate the impact of BPA on CPA in patients with inoperable CTEPH. Methods We retrospectively analyzed 78 patients (388 BPA sessions) with inoperable CTEPH who underwent BPA in our hospital from September 2012 to June 2018. Total number of BPA sessions was 5.0±1.8 (range 1–10). The pressure values were obtained from right heart catheterization at baseline (n=78), just after the final BPA (n=78) and follow-up (n=19) periods. The intervals from baseline to the final BPA and the final BPA to follow-up were 593±498 days and 397±276 days, respectively. Results Mean age was 60.5±12.6 years old, and 64 (82%) were female. All patients were symptomatic (WHO functional class II/III/IV 16/55/7). Patients who had pulmonary vasodilators decreased from 70 (90%) at baseline to 23 (28%) at the final BPA and 2 (15%) at follow-up. BPA reduced mPAP and RPA significantly from baseline to the final BPA and follow-up periods. BPA also improved CPA with significant reduction of pulse pressure despite no significant changes in stroke volume between baseline and follow-up (Table). CPA between the final BPA and follow-up was equivalent (p=0.95). Conclusions BPA improved CPA just after the final BPA in inoperable CTEPH patients. In addition, CPA was preserved during the follow-up after the final BPA sessions. These data suggest that BPA consistently unloads RV systolic afterload in those patients.