Factors associated with oxygenation improvement after balloon pulmonary angioplasty for non-operable chronic thromboembolic pulmonary hypertension.

<bold>Background:</bold> Balloon pulmonary angioplasty (BPA) is promising for non-operable chronic thromboembolic pulmonary hypertension (CTEPH). Almost normal hemodynamics at rest could be achieved. Oxygenation also improved; however, improvement was limited. We aimed to clarify the clinical mechanism of oxygenation improvement after BPA in non-operable CTEPH. <bold>Methods:</bold> Data from 173 patients with CTEPH, who underwent BPA from 2011 to 2022, were retrospectively analyzed. We evaluated hemodynamics with right heart catheterization, arterial blood gas, respiratory function tests, and exercise capacity (cardiopulmonary exercise testing) which were routinely performed at baseline and after BPA. <bold>Results:</bold> Nearly normal hemodynamics achieved (mean pulmonary artery pressure: 37.5±10.0 to 20.6±4.9 mmHg, p<0.01). Oxygenation slightly improved (partial pressure of arterial oxygen [PaO2]; 61.5±12.3 to 67.7±12.7mmHg, p<0.01). Baseline lower PaO2 (p<0.001), higher alveolar arterial gradient for oxygen (A-aDO2) (p=0.006), and higher diffusing capacity for lung carbon monoxide (p=0.047) were associated with greater improvement in PaO2 after BPA in the multivariable linear analysis. Moreover, the decrease in A-aDO2 was correlated to the improvement in PaO2 after BPA in multivariable analysis (p<0.001). <bold>Conclusions:</bold> The decrease of A-aDO2; the marker of ventilation-perfusion mismatch and lung diffusing capacity, was strongly correlated with the improvement of oxygenation after BPA. The decrease of ventilation-perfusion mismatch by BPA contributed most, however normalized oxygenation would be still difficult to achieve.