Elevated Angiopoietin-2 Level in Patients With Continuous-Flow Left Ventricular Assist Devices Leads to Altered Angiogenesis and Is Associated With Higher Nonsurgical Bleeding

Circulation. 2016 Jul 12;134(2):141-52. doi: 10.1161/CIRCULATIONAHA.115.019692. Epub 2016 Jun 28.


Background: Nonsurgical bleeding is the most common adverse event in patients with continuous-flow left ventricular assist devices (LVADs) and is caused by arteriovenous malformations. We hypothesized that deregulation of an angiogenic factor, angiopoietin-2 (Ang-2), in patients with LVADs leads to increased angiogenesis and higher nonsurgical bleeding.

Methods: Ang-2 and thrombin levels were measured by ELISA and Western blotting, respectively, in blood samples from 101 patients with heart failure, LVAD, or orthotopic heart transplantation. Ang-2 expression in endothelial biopsy was quantified by immunofluorescence. Angiogenesis was determined by in vitro tube formation from serum from each patient with or without Ang-2-blocking antibody. Ang-2 gene expression was measured by reverse transcription-polymerase chain reaction in endothelial cells incubated with plasma from each patient with or without the thrombin receptor blocker vorapaxar.

Results: Compared with patients with heart failure or those with orthotopic heart transplantation, serum levels and endothelial expression of Ang-2 were higher in LVAD patients (P=0.001 and P<0.001, respectively). This corresponded to an increased angiogenic potential of serum from patients with LVADs (P<0.001), which was normalized with Ang-2 blockade. Furthermore, plasma from LVAD patients contained higher amounts of thrombin (P=0.003), which was associated with activation of the contact coagulation system. Plasma from LVAD patients induced more Ang-2 gene expression in endothelial cells (P<0.001), which was reduced with thrombin receptor blockade (P=0.013). LVAD patients with Ang-2 levels above the mean (12.32 ng/mL) had more nonsurgical bleeding events compared with patients with Ang-2 levels below the mean (P=0.003).

Conclusions: Our findings indicate that thrombin-induced Ang-2 expression in LVAD patients leads to increased angiogenesis in vitro and may be associated with higher nonsurgical bleeding events. Ang-2 therefore may contribute to arteriovenous malformation formation and subsequent bleeding in LVAD patients.

Keywords: LVAD; angiogenesis; angiopoietin-2; cardiac transplant; nonsurgical bleeding; thrombin.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Aged
  • Angiopoietin-2 / biosynthesis
  • Angiopoietin-2 / blood*
  • Angiopoietin-2 / genetics
  • Arteriovenous Malformations / complications
  • Biomarkers
  • Cross-Sectional Studies
  • Endothelial Cells / metabolism
  • Female
  • Heart-Assist Devices
  • Hemorrhage / etiology*
  • Human Umbilical Vein Endothelial Cells
  • Humans
  • Male
  • Middle Aged
  • Neovascularization, Pathologic / blood
  • Neovascularization, Pathologic / etiology*
  • Neovascularization, Pathologic / physiopathology
  • Thrombin / pharmacology


  • Angiopoietin-2
  • Biomarkers
  • Thrombin