Research blood samples will be drawn pre-transplant, and at monthly post transplant visits at times corresponding to post-transplant, standard of care ImmKnowo and AlloMap clinical testing. A minimum of 12 visits per patient is expected

The second group will include heart transplant recipients at one year post transplant who consent to participate in the study. Research blood samples will be drawn at quarterly post transplant visits (standard of care in Year 2 post transplant) corresponding to ImmunKnow and AlloMap testing. A minimum of 4 visits per patient is expected.

To systematically collect blood samples from heart allograft recipients who are 0 -2 years post-transplant for eventual screening of blood cell gene activity, in order to identify diagnostically useful biomarkers that can help distinguish among multiple possible clinical presentation, e.g., acute rejection, antibody mediated rejection, infection, coronary artery disease, a variety of potential causes for heart dysfunction.).

Recent work using our gene expression profiling (GEP) has shown that peripheral blood cells display a unique GEP that is 90% accurate for detection of acute rejection in liver transplant patients. The Investigators hypothesize that heart allograft recipients will display a similar pattern (Aim #2). The Investigators will retrospectively select longitudinal samples collected in Aim #1 from patients who did not experience rejection and from those who did, in order to determine if their GEP correlates with what we have observed for liver patients.

To correlate the BUMC GEP results with with AlloMap results. The Investigators will retrospectively select longitudinal samples collected in Aim #1 from patients who had normal vs. high AlloMap scores