Heart Transplant Patients

The goal of this clinical trial is to learn whether a breathing-based relaxation technique called heart rate variability biofeedback (HRVB) can help reduce anxiety in adult patients who are in the intensive care unit (ICU) and waiting for a heart transplant. The main questions it aims to answer are: Can HRVB reduce anxiety in patients awaiting heart transplantation in the ICU? Does HRVB help patients feel more in control of their emotions during this stressful time? Participants will: Complete a brief anxiety assessment before and after the intervention Participate in a guided HRVB session using a breathing device or app Learn how to use the technique on their own for future stress management

This clinical tissue-based, drug-free, single-center, longitudinal study aims to validate a new diagnostic method, namely, to evaluate whether plasma levels of circulating donor free DNA in the recipient's blood (Dd-cfDNA: donor-derived cell free DNA), in patients undergoing orthotopic heart transplantation, can be predictive of the presence of acute myocardial rejection with the same sensitivity as immunohistochemical analysis on endomyocardial biopsy specimen, the current gold standard for the diagnosis of acute cell-mediated myocardial rejection, in a population consisting of pediatric patients and adult patients with congenital heart disease undergoing orthotopic heart transplantation.