STUDY DESIGN Collection of data and blood samples will be performed at the same time as the patient's regularly scheduled surveillance cardiac catheterization (1 month and 12 months after heart transplant). Additionally donor-specific anti-HLA antibodies (class I, II) and MHC complex class I - related chain A (MICA) antibodies will be measured also before heart transplant and in 6 months after heart transplant during regular follow-ups.