Background—Transplant vasculopathy is the main limiting factor of the long-term success of heart transplantation. We sought to establish the role of platelets in the development and progression of transplant vasculopathy.

Methods and Results—Platelet analysis and intracoronary ultrasound examination were performed in 78 heart transplant recipients. Quantitative intracoronary ultrasound was used to define the severity of disease at baseline (48.8±4.5 months after transplantation) and at 1-year follow-up. Platelet activation was assessed with the use of immunological surface markers of activation (ligand-induced binding site 1 [LIBS-1], P-selectin, GPIIb-IIIa) and flow cytometry. We found that LIBS-1 immunoreactivity was significantly increased in patients with diffuse disease when compared with focal transplant disease (median [quartile], 27[14, 64] versus 18[7.9, 47], P=0.04). In a logistic regression model, we found that LIBS-1 was an independent predictor for the presence and progression of diffuse transplant vasculopathy (P=0.04). Patients with enhanced LIBS-1 levels (>75% quartile) had a 3.3-fold increased relative risk (95% CI 1.8 and 18.9, P=0.002) for the presence of diffuse transplant vasculopathy. When a cutoff value of 16.5 for the level of LIBS-1 was used, patients had a 4.8-fold increased relative risk (95% CI 1.9 and 12.5, P<0.01) for the progression of transplant vasculopathy.

Conclusions—Enhanced platelet activation is strongly associated with the development and progression of transplant vasculopathy. Understanding the underlying pathophysiological mechanisms might contribute to the development of treatment strategies to prevent transplant vasculopathy.