The purpose of this study is to compare the effectiveness of 2 approaches for monitoring heart transplant rejection with either a blood test that looks at cell-free DNA (fragments of DNA from the transplanted heart) or a heart biopsy. Specifically, Prospera (a commercially available blood test that measures cell-free DNA) will be used to monitor heart transplant rejection compared to a heart biopsy. The Prospera blood test is under investigation in clinical trials to determine its effectiveness in rejection surveillance. Study procedures also include blood sample collection and medical records review. Participants will be randomly assigned to 1 of 2 groups to monitor for rejection through the first year after their transplant. About 2 out of every 3 patients will be randomly assigned to Group 1. About 1 out of every 3 patients will be randomly assigned to Group 2. In Group 1, participants will receive Prospera testing per their transplant center’s standard-of-care rejection monitoring schedule. In Group 2, heart biopsies will be performed per their transplant center’s standard-of-care rejection monitoring schedule.