The goal of this observational study is to learn about the impact of donor heart procurement time based on circadian rhythm on the long-term outcomes of heart transplant recipients. The main question it aims to answer is:

Does the time of day when a donor heart is procured-specifically during the circadian repression phase (00:00-12:00) versus the activation phase (12:00-00:00)-affect post-transplant survival and rejection rates in patients with end-stage heart failure?

Patients undergoing heart transplantation at the study hospital will have leftover donor heart tissue and preservation fluid collected during surgery for multi-omics analysis. These participants will then be followed prospectively for up to three years to track survival and rejection outcomes.

Inclusion Criteria:

• All patients undergoing heart transplantation surgery at our hospital due to end-stage heart failure.

Exclusion Criteria:

• Exclude patients undergoing multi-organ combined transplantation, re-do heart transplantation, or those with a history of other organ transplantation.

This study will enroll adult patients diagnosed with end-stage heart failure who are scheduled to undergo heart transplantation at the study hospital. Participants must meet standard transplant eligibility criteria. Exclusion criteria are applied to minimize confounding factors, including previous organ transplants, re-transplants, and multi-organ transplant recipients, ensuring a more homogeneous study population focused on first-time, heart-only transplant cases.

Individual participant data (IPD) from this study will not be shared publicly. All data collected will be used solely by the research team for the analysis purposes outlined in this protocol.