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 is a single-group clinical trial designed to evaluate the effectiveness of heart rate variability biofeedback (HRVB) in reducing anxiety among adult patients who are currently admitted to the intensive care unit (ICU) and awaiting heart transplantation. Patients in this population often experience elevated levels of psychological distress, including anxiety and panic symptoms, due to the uncertainty of their medical condition, the high-stress ICU environment, and the emotional burden of awaiting a life-saving procedure.

Heart rate variability (HRV) is a physiological marker of autonomic nervous system function and emotional regulation. HRVB is a non-invasive intervention that teaches individuals to regulate their breathing in a way that promotes optimal HRV. This technique has been shown in prior research to reduce anxiety and improve emotional resilience in various populations, but its application in critically ill transplant candidates remains underexplored.

Participants in this study will complete a baseline assessment of anxiety using validated self-report measures. They will then participate in a guided HRVB session, which includes paced breathing instruction and the use of a biofeedback device or app that provides real-time feedback on heart rate and breathing patterns. Following the session, participants will complete a post-intervention assessment to evaluate changes in anxiety levels. Participants will also be encouraged to continue practicing the technique independently as appropriate.

This study aims to assess the feasibility and immediate psychological benefits of HRVB in a high-acuity medical setting and to inform future research on integrative behavioral health interventions for transplant candidates.

Inclusion Criteria

• any gender
• any race/ethnicity
• ≥18 years old with no upper limit
• currently inpatient in the cardiac ICU, awaiting heart transplant
• elevated anxiety symptoms as evidenced by cut scores on the Depression, Anxiety and Stress Scale (DASS-21) and the Cardiac Anxiety Questionnaire (CAQ) (Lovibond & Lovibond, 1995; Eifert et al., 2000).
• proficiency in speaking, reading and writing in English Participants in this study must be proficient in English due to the language limitations of the study administrator. The intervention includes a teaching component that requires verbal instruction, psychoeducation, and interactive engagement, all of which will be conducted exclusively in English. At this time, the study administrator is only proficient in English and is unable to reliably deliver the intervention or assess participant understanding in other languages. To ensure consistency, accuracy, and fidelity of the intervention, as well as to maintain ethical standards in informed consent and participant comprehension, only English-speaking individuals will be eligible to participate.
• able/willing to consent to participate Exclusion Criteria
• <18 years of age
• active psychosis or delirium
• current neurological problems (e.g., stroke) at time of enrollment that would interfere with the ability to complete the practice
• on a ventilator at time of enrollment
• pregnancy
• unable or unwilling to consent to participate

Only IPD used in the results publication

Beginning 1 year after publication with no end date