The Care After Life-threatening Medical Events Study

HRV biofeedback is a technique that combines slow paced breathing with the use of accurate, moment-to-moment physiological monitoring. The goal is to make internal cardiac information available to people in order to help them learn how to increase the beat-to-beat variability in their heart's activity and thereby increase parasympathetic activity of the autonomic nervous system. Apart from active interventions such as exercise training that reliably increase HRV but that may be inappropriate for many cardiac patients, HRV biofeedback is an easy-to-implement technique which allows people to monitor and then ultimately alter their parasympathetic activity.

Research is needed to determine whether HRV biofeedback training has beneficial consequences for mental and cardiovascular health in patients who have experienced serious, life-threatening cardiac events. The investigator believes that cardiac arrest survivors, in particular, may stand to benefit from such an intervention because many of them experience clinically significant psychological distress after their medical event.

Distressed cardiac patients may be especially motivated to learn to influence their own heart activity in order to improve their own HRV, reduce their cardiovascular risk, and lessen their symptoms of psychological distress. Therefore, it may be wise to harness this motivation in the service of helping these patients deliberately learn to alter their own autonomic activity rather than simply breathing at a rate that automatically improves HRV without any learning process. By providing patients with an external (e.g., visual) form of feedback about their otherwise largely inaccessible autonomic physiology (i.e., vagus nerve activity), the investigator will conduct a feasibility study of HRV biofeedback training with the goal of increasing HRV and reducing anxiety symptoms.

The purpose of this pilot study is to examine the feasibility of enrolling 10 participants and assessing the feasibility, acceptability, appropriateness, and usability of the at-home, multi-week HRV biofeedback training as well as participants' compliance with the intervention. Additionally, the purpose of the study is to assess whether participants generally show a decrease in cardiac-related interoceptive fear, a decrease in trait anxiety, a decrease in negative affect, and an increase in HRV during the course of the study. The data collected from participants as part of this feasibility pilot will influence the decision to continue with a larger randomized clinical trial using the methods in this pilot together with a control group. Progress will be monitored with Polar H10 heart rate monitor - a supremely precise heart rate sensor that comes with the Polar Pro chest strap. It will be used with a smartphone app Elite HRV - which is non-experimental.

Inclusion criteria

• Age 18 years or older
• Fluent in English
• A diagnosis of cardiac arrest (CA)
• Time elapsed since their CA is less than 72 months
• Elevated post-traumatic stress disorder (PTSD) symptom total scores on the 17-item Post-Traumatic Stress Disorder Checklist (PCL) of 30 or higher (i.e., greater than the median in a prior sample of cardiac arrest survivors) or elevated PCL-5 scores of 30 or higher or Acute Stress Disorder Scale (ASDS) scores of 34 or higher
• Owns either an iPhone or Android smartphone in order to run the app involved in the intervention

Exclusion criteria

• Breathing difficulty that does not allow participant to complete the intervention
• Inability to comply with the protocol (either self-selected or indicated during screening that s/he could not complete all requested tasks). This includes, but is not limited to, patients with a level of cognitive impairment indicative of dementia and patients with current alcohol or substance abuse, and patients with severe mental illness (e.g., schizophrenia).