ZeroHeart Biopsy - Prediction of Deceased Donor Heart Transplant Performance From Organ Donors Using Pre-Transplant Biopsies - A Pilot Study

The goal of this observational study is to evaluate whether molecular analysis of donor heart biopsies taken at the time of organ removal ("Time Zero") can help predict the future function and rejection risk of the transplanted heart in adult transplant recipients. The main questions it aims to answer are: * Can early molecular injury in the donor heart, caused by brain death or circulatory death, be detected at the time of organ removal? * Can these early molecular findings predict short-, mid-, and long-term transplant outcomes, such as graft function or rejection? Participants will: * Include heart donors whose hearts are being transplanted (both standard and marginal donors, including DBD and DCD cases) * Provide two small biopsies from the donor heart at the time of organ removal: one for routine pathology, one for microarray-based molecular analysis * Have routine follow-up biopsies after transplantation as part of standard care (no additional procedures required beyond medical standard) Researchers will compare biopsy results from different donor types (standard vs. marginal, DBD vs. DCD) to see if early molecular signals are linked to later heart transplant outcomes.