- Blood samples 60 cc (about 3 tablespoons) of blood will be collected from all participants by needle stick in a vein. The sample will be analyzed for genes and proteins that might predict heart rejection. In addition, many genes in blood cells and cells lining blood vessels that are unrelated to heart transplant rejection and whose functions or significance are unknown will also be examined for ideas for future research. Patients enrolled while on a wait list will, after transplantation, have an additional 44 cc (about 2 tablespoons) of blood collected at each heart biopsy and rejection episode during the first year of transplant, and 60 cc collected with each yearly biopsy for the next 9 years.