Left ventricular assist devices (LVADs) have improved survival of patients with end stage congestive heart failure (HF), but patients are at high risk of both hemorrhage and thrombosis. Acquired von Willebrand (vW) disease is observed in most patients after continuous flow LVAD insertion, presumably due to shear-dependent vW factor (vWf) cleavage, which may contribute to hemorrhage, but there are no validated thrombosis biomarkers. Since shear can also activate platelets, and platelets contain high concentration of transforming growth factor β1 (TGF-β1), we analyzed plasma TGF-β1 levels in patients before and after LVAD implantation and correlated the data with the loss of high molecular weight (HMW) vWf multimers.
Blood samples were collected from 14 HF patients enrolled either as a destination therapy (n=2) or as a bridge to transplantation (n=12) at the Columbia University before and after LVAD implantation. Plasma was prepared by centrifuging blood at 12,000 rpm for 5 min at 4°C within 5 min of blood drawing. Total TGF-β1 levels were measured after acidification of samples using a 2-antibody ELISA (R&D Systems). The platelet α-granule proteins thrombospondin 1 (TSP-1) and platelet factor 4 (PF4) were detected by immunoblotting. vWf multimers were analyzed by electrophoresis of plasma after running in 1.2% discontinuous agarose gel followed by in-gel immunoreactivity band quantification using the LI-COR imaging system. HMW-vWf multimers were defined as the percentage of total vWf antigen contributed by multimers above the 11th identifiable band, starting from the cathodal position.
Plasma total TGF-ß1 levels were higher in HF patients before LVAD implantation than in 16 healthy controls (3.76 ± 1.55 vs. 1.0 ± 0.60 ng/ml; p <0.001). After LVAD insertion, the levels in HF patients increased further to 5.20 ± 2.30 ng/ml (p=0.014). Plasma TGF-ß1 levels in HF patients before and after LVAD implantation were positively correlated with TSP-1 levels (r=0.86; p<0.0001), but PF4 was not detectable, suggesting in vivo release of TGF-β1 from platelets. A reduced percentage of HMW-vWf multimers was observed in HF patients before LVAD insertion compared to healthy controls (18.0 ± 10.0 vs. 29.5 ± 2.5 %; p=0.018), and the percentage was further reduced after LVAD implantation (11.0 ± 9.0 %; p=0.027). There was a weak negative correlation between the percentage of HMW-vWf multimers and TGF-ß1 after LVAD implantation (r= - 0.40; p=0.05).
We conclude that HF itself, even before LVAD insertion, is associated with both loss of HMW-vWf multimers and elevation of plasma TGF-ß1 levels and both abnormalities are exacerbated by LVAD implantation.
No relevant conflicts of interest to declare.
Asterisk with author names denotes non-ASH members.