Progressive lesion-level hemodynamic improvement from immediate post-procedural assessment to follow-up after balloon pulmonary angioplasty

Background Balloon pulmonary angioplasty (BPA) is an established therapy for chronic thromboembolic pulmonary hypertension (CTEPH); however, no standardized lesion-level physiological endpoint has been defined. Treated vessels frequently exhibit further enlargement and perfusion improvement during follow-up, suggesting potential divergence between immediate post-procedural and later hemodynamic responses. Distal-to-proximal pulmonary artery pressure ratio (Pd/Pa), measured using a monorail-type pressure catheter, has been adopted in selected centers as a physiological procedural guide, yet its longitudinal behavior after BPA remains incompletely characterized. Purpose To assess changes in lesion-specific Pd/Pa between the immediate post-procedural phase and follow-up in treated pulmonary arteries. Methods We retrospectively analyzed consecutive patients who underwent BPA between August 2024 and December 2025 in whom proximal pulmonary artery pressure (Pa) and distal pulmonary artery pressure (Pd) were measured immediately after balloon dilatation and reassessed during follow-up. Pd/Pa was defined as the ratio of distal to proximal pulmonary artery pressure. Analyses were performed at the lesion level. Results Twenty-one patients (41 lesions) were included. Mean age was 67 ± 11 years, and 71% were female. The median interval to reassessment was 123 (63–168) days. Baseline hemodynamics at the time of lesion treatment were mPAP 26 (20–32) mmHg, cardiac index 2.44 (1.91–2.96) L/min/m², and PVR 4.79 (3.43–6.29) WU. Immediately post-procedurally, Pd/Pa increased from 0.39 (0.29–0.48) to 0.72 (0.59–0.79) (Bonferroni-adjusted p<0.003). At follow-up, mPAP decreased to 22 (15–24) mmHg (p<0.001) and PVR to 3.5 (2.5–4.2) WU (p<0.001), whereas cardiac index remained unchanged at 2.52 (2.18–3.05) L/min/m² (p=0.351). Lesion-specific Pd/Pa further increased to 0.78 (0.68–0.90), exceeding immediate post-procedural values (Bonferroni-adjusted p<0.001). Peak waveform analysis showed concordant changes: peak Pd/peak Pa increased from 0.61 (0.50–0.72) to 0.69 (0.59–0.79) (p=0.001), while the peak Pd – peak Pa pressure gradient decreased from 16 (10–25) to 9 (6–16) mmHg (p<0.001). Pd/Pa increased between the immediate post-procedural phase and follow-up in 29 of 41 lesions. Applying a cutoff of 0.7, 7 lesions newly met the criterion at follow-up, whereas 4 no longer met it. Conclusion Lesion-specific Pd/Pa continues to increase during follow-up after BPA, exceeding immediate post-procedural values. Immediate post-procedural assessment may therefore underestimate the ultimate physiological benefit achieved through vascular remodeling and perfusion redistribution. Procedural optimization should incorporate the expected delayed hemodynamic gain when defining adequate balloon expansion.