Using Breathing Techniques to Ease Anxiety in ICU Patients Awaiting Heart Transplants

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