Pregnancy-associated plasma protein A – a new indicator of pulmonary vascular remodeling in chronic thromboembolic pulmonary hypertension?

Background In chronic thromboembolic pulmonary hypertension (CTEPH) impaired pulmonary hemodynamics lead to right heart failure. Natriuretic peptides reflect hemodynamic disease severity. Pregnancy-associated plasma protein-A (PAPP-A) might address another aspect of CTEPH - chronic tissue injury and inflammation. This study assessed dynamics of PAPP-A in CTEPH patients who undergo therapy with pulmonary endarterectomy (PEA) or balloon pulmonary angioplasty (BPA). Methods The study included a total of 125 CTEPH patients scheduled for treatment (55 PEA/ 70 BPA) and a control group of 58 patients with pulmonary hypertension other than CTEPH. Biomarker measurement was performed at baseline and follow-up in the CTEPH cohort, prior to each BPA in the BPA cohort and once in the control group. Results The median PAPP-A level was slightly higher ( p = 0.05) in CTEPH patients [13.8 (11.0–18.6) mU/L], than in the control group [12.6 (8.6–16.5) mU/L], without a difference between the BPA and PEA group ( p = 0.437) and without a correlation to mean pulmonary artery pressure ( p = 0.188), pulmonary vascular resistance ( p = 0.893), cardiac index ( p = 0.821) and right atrial pressure ( p = 0.596). PEA and BPA therapy decreased the mean pulmonary artery pressure ( p < 0.001) and pulmonary vascular resistance ( p < 0.001) and improved the WHO-functional-class (baseline: I:0/II:25/III:80/IV:20 vs. follow-up: I:55/II:58/III:10/IV:2). PAPP-A levels decreased after PEA [13.5 (9.5–17.5) vs. 11.3 (9.8–13.6) mU/L; p = 0.003) and BPA treatment [14.3 (11.2–18.9) vs. 11.1 (9.7–13.3) mU/L; p < 0.001). The decrease of PAPP-A levels is delayed in comparison to N-terminal pro-B-type natriuretic peptide. Conclusion PAPP-A is overexpressed in CTEPH and decrease significantly after surgical or interventional therapy, however without association to hemodynamics. Further investigation is needed to define the underlying mechanism of PAPP-A expression and changes after therapy in CTEPH.