Injury of transplant tissue by a transplant recipient's immune system continues to be the leading cause of graft rejection and recipient death. The purpose of this study is to identify a single test or a combination of noninvasive tests currently used for heart transplant monitoring that correlate to long-term graft survival.

A major cause of heart transplant failure is the blockage of blood flow from lesions caused by ongoing injury and repair of the graft by the host's immune system. However, the role of T cells, antibodies, and other parts of the recipient's immune system are not well understood in transplant injury. Currently, there are no effective, noninvasive ways to detect or predict how an individual's immune system will react to a transplant. The purpose of this study is to correlate current noninvasive monitoring tests with long-term graft survival and function, and determine which tests are the most accurate predictors of this survival.

Participants in this study must currently be on the waiting list for a heart transplant and have a donor heart available to them. This study will consist of six study visits over 12 months. The baseline visit will occur on the day of transplantation. Follow-up visits will occur at Week 6 and Months 3, 6, 9, and 12 post-transplant. At each visit, a physical exam, medication tracking, assessment of graft survival, and blood and urine collection will occur. At the Week 6 and Month 12 visits, intravascular ultrasound and echocardiograms will occur. At the Week 6, Month 6, and Month 12 visits, endomyocardial biopsies will also occur. No immunosuppressive therapy will be provided by the study.

Inclusion Criteria:

• Age greater than 10 and a body mass of 30 kg (66 lbs) or more
• On waiting list for a heart transplant for whom a donor heart available
• Willing to comply with study protocol
• Willing to use acceptable forms of contraception
• Parent or guardian willing to provide consent, if applicable

Exclusion Criteria:

• Receiving multiple organ transplants
• Previously received organ transplants
• Other comorbidities that, in the opinion of the site investigator, would interfere with the study
• Currently taking immunosuppression for nontransplant reasons
• Participation in an interventional clinical trial
• Pregnancy or breastfeeding

People who are on the waiting list for a heart transplant at one of the participating study sites (listed below)