Balloon pulmonary angioplasty relieves haemodynamic stress towards untreated-side pulmonary vasculature and improves its resistance in patients with chronic thromboembolic pulmonary hypertension

Aims: Chronic thromboembolic pulmonary hypertension (CTEPH) is characterised by organised thrombotic obliteration of major vessels and small-vessel arteriopathy in the non-thrombosed vessels. The aim of this study was to investigate the impact of balloon pulmonary angioplasty (BPA) on the non-BPA-side pulmonary vasculature in patients with CTEPH. Methods and results: This study explored the outcomes of 20 unilateral BPA sessions in 13 CTEPH patients. We measured the pulmonary vascular resistance (PVR), pulmonary artery (PA) flow in the BPA-side and non-BPA-side lungs, respectively, using phase contrast MRI and cardiac catheterisation. The interval from BPA to the follow-up evaluation was 92.8±52.0 days. A single session of BPA decreased mean PA pressure from 37.4±6.2 to 30.9±6.5 mmHg (p<0.001). In the BPA side, BPA increased the PA flow from 1.58±0.65 to 1.95±0.62 L/min (p=0.001) and decreased the PVR from 27.3±27.4 to 14.4±9.0 Wood units (p=0.004). In contrast, it decreased both the non-BPA-side PA flow from 2.25±0.64 to 1.90±0.23 L/min (p=0.008) and the non-BPA-side PVR from 14.8±6.6 to 12.8±3.9 Wood units (p=0.01). Conclusions: BPA could relieve haemodynamic stress towards the non-BPA-side vasculature and decrease its PVR in patients with CTEPH, suggesting that it can suppress or regress the progression of the small-vessel arteriopathy in non-BPA-side vasculature, presumably due to haemodynamic unloading.