CARDIS (Cardiac ARrest DIgital Support): study protocol for a randomised controlled trial of a web-based support intervention for cardiac arrest survivors

Background Surviving sudden cardiac arrest often lead to long-term cognitive, emotional, and physical consequences. Although clinical guidelines recommend structured post-cardiac arrest follow-up, such follow-up is often lacking or inconsistent. Tailored digital interventions are scarce but may help address gaps in follow-up resources. The CARDIS trial evaluates the effects on patient-reported outcome measures of a co-created, web-based support programme designed to improve wellbeing, self management, and reintegration into everyday life for cardiac arrest survivors. Methods CARDIS is a multicentre, parallel-group, randomised controlled trial enrolling cardiac arrest survivors aged >18 years. Participants will be randomised 1:1 to intervention or control. Both groups will receive standard post-cardiac arrest care, including a routine followup visit with screening and management of cognitive, physical and emotional health, as well as a printed booklet. The intervention group will additionally receive access to a webbased selfguided support programme for 3 months. After study completion, control participants will be offered the programme. Outcomes Primary outcome is overall wellbeing and health (QWB) at 3 months. Secondary outcomes include self-reported cognitive problems, HRQoL, life satisfaction, symptoms of depression and anxiety, post-traumatic stress, fatigue, and sleep disturbances. A process evaluation will evaluate social selection bias, adherence and participants experiences. Discussion The CARDIS trial will investigate the use of more accessible and standardised follow-up pathways by complementing existing care structures, thereby enhancing equity in long-term recovery and quality-of-life without requiring additional healthcare resources. The process evaluation will provide data on adherence, social selection, and engagement, essential for future implementation. Trial registration: The trial is registered at clinicaltrials.gov (NCT07240714).