Angiopoietin-2 and D-dimer add prognostic information to clinical risk in pulmonary arterial hypertension

Abstract

Background: Thrombosis and endothelial injury are pathologic hallmarks of pulmonary arterial hypertension (PAH). We aimed to evaluate whether markers of endothelial dysfunction and coagulation in the blood would provide insight into disease activity, treatment response, and outcomes in PAH.

Methods: We prospectively collected baseline and 3-month follow-up blood samples from treatment-naïve patients with PAH (n = 22) and those who had a clinical indication to intensify therapy (n = 19). In addition, we recruited 12 healthy people and clinically stable patients with PAH (n = 45) as controls who had 2 blood samples collected twice within 14 days. We generated platelet-free plasma and measured D-dimer, angiopoietin-2, thrombin time, soluble P-selectin, von Willebrand factor, and vascular endothelial growth factor. We assessed treatment response with Reveal Lite 2 scores (all patients had N-terminal-pro-brain natriuretic peptide, 6-minute walk, and functional class assessment at both visits) and followed clinical outcomes for 3 years.

Results: Angiopoietin-2 levels were elevated and fell in response to effective therapy (drop in Reveal Lite 2 score). At follow-up, persistently elevated angiopoietin-2 levels predicted clinical events and even identified low-risk participants who subsequently had events. D-dimer levels were also elevated in patients with PAH but did not change in response to therapy. Several other abnormalities in endothelial and platelet activation were identified (including elevated soluble P-selectin, elevated von Willebrand factor, and elevated vascular endothelial growth factor) but these did not change with treatment or predict outcome.

Conclusions: Angiopoietin-2 and D-dimer are elevated in patients with PAH and may add prognostic information to routine clinical assessment.

Keywords: D-dimer; REVEAL; angiopoietin-2; pulmonary arterial hypertension; score; thrombosis.

Figure 1

Ang-2 is elevated in patients with PAH, responds to treatment, and may predict outcomes. (A) Ang-2 levels in patients with PAH vs healthy controls. (B) Ang-2 drops after adding therapy for those who had improvement in risk score. (C) Event-free survival in patients with PAH (whether or not intensifying treatment) with high Ang-2 (>90%-ile of healthy) vs normal Ang-2 levels. (D) In participants with follow-up Reveal Lite 2 ≤5, those with elevated Ang-2 levels had worse event-free survival. Ang-2, angiopoietin-2; PAH, pulmonary arterial hypertension.

Figure 2

VEGF is elevated in patients with PAH. (A) VEGF levels in patients with PAH are elevated compared to healthy controls. (B) VEGF levels in treatment responders (indicated by drop in Reveal Lite 2.0 score) vs nonresponders among patients with PAH starting or intensifying treatment. Lower levels at baseline may predict treatment responders. (C) There was no difference in event-free survival based on VEGF level. PAH, pulmonary arterial hypertension; VEGF, vascular endothelial growth factor.

Figure 3

D-dimer is elevated in patients with PAH and predicts treatment response. (A) D-dimer level in patients with PAH compared to healthy controls. (B) D-dimer levels were lower at baseline in patients who had a drop in Reveal Lite 2 score after adding therapy; D-dimer did not fall with new therapy, but higher D-dimer levels were observed in those who did not improve with therapy. (C) Event-free survival in patients with PAH (whether or not intensifying treatment) with high D-dimer (>90%-ile of healthy) vs normal D-dimer levels. (D) Event-free survival in patients with high (90%-ile of healthy) or normal Ang-2 and D-dimer levels; for those with high Ang-2 levels, a high D-dimer predicted even higher risk. D-dimer added nothing for those with more normal Ang-2 levels. Data are shown as median + IQR or Kaplan-Meier event curves. Ang-2, angiopoietin-2; IQR, inter-quartile range; PAH, pulmonary arterial hypertension.

Figure 4

Thrombin time, P-selectin, and VCAM (A) thrombin time was generally shorter but also more variable in PAH compared to healthy controls, resulting in no net difference. (B) P-selectin levels are elevated in patients with PAH vs HC. (C) VCAM levels are elevated in patients with PAH vs HC. Data are shown as median + IQR. HC, healthy controls; IQR, inter-quartile range; PAH, pulmonary arterial hypertension.