The goal of this study is to develop The Heart Priority programme, a supplement to standardised cardiac rehabilitation (CR) aimed at identifying and supporting cardiac patients at risk of dropout due to being in a vulnerable situation. Additionally, the study aims to test the programme through a feasibility study.

The programme comprises two main parts: 1) an evidence-based identification form to identify patients at risk of dropout from CR due to being in a vulnerable situation and 2) an add-on intervention targeted these patients.

The study will be guided by the Medical Research Council's framework for developing and evaluating complex interventions (MRC). The development follows an iterative three-stage process guided by the framework for co-producing and prototyping of healthcare interventions. Stage 1 is preparation by considering the knowledgebase. Building on this knowledge, stage 2 and 3 includes a co-production and prototyping process, aiming to develop, field test and adapt the programme, deemed ready for feasibility testing.

The feasibility study will be designed as a single-arm follow-up study conducted in two community health care centres in Denmark. Process data will be collected continuously over a six-months period and at the study's conclusion, focussing on three dimensions: implementation (reach and fidelity), acceptability, and mechanism of impact.

Despite advancements in reducing cardiovascular disease, heart disease remains a significant health issue. Cardiac rehabilitation (CR) is crucial for recovery, with evidence showing its positive impact on morbidity, mortality, and functioning. However, dropout rates, especially among patients in a vulnerable situation, are high due to social inequalities and lack of tailored interventions. To implement interventions for individuals in a vulnerable situation, it is necessary to: 1) identify the target group and 2) develop an intervention tailored to the group. There is currently no such intervention within the field of CR. Therefore, we developed, and feasibility tested the Heart Priority Programme aiming to reduce dropouts in cardiac rehabilitation among patients in a vulnerable situation.

The purpose is to develop the Heart Priority Programme in close collaboration with stakeholders and subsequently conduct a feasibility study in community healthcare services within the Central Denmark Region.

The study follows the Medical Research Council's framework for developing complex interventions, focusing on the development and feasibility phases.

First a development study will be conducted. The development of the Heart Priority Programme will follow a three-stage iterative process, including evidence review, stakeholder consultations, co-production of intervention content, and prototyping involving close collaboration between cardiac patients, healthcare professionals, and researchers. The Heart Priority Programme encompasses two main parts: 1) an evidence-based identification form to identify patients being in a vulnerable situation (professional tool to be used during the initial consultation) and 2) an add-on intervention to supplement standard CR targeted these patients.

Subsequently, a feasibility study designed as a single-arm follow-up study will be conducted in two community healthcare services in Central Denmark Region. The programme is delivered by the CR team. The evidence-based identification form will be used for all cardiac patients referred to CR and fulfilled during the initial consultation. If the healthcare professional identifies a patient at risk of dropout due to being in a vulnerable situation this patient will receive the add-on intervention targeted these patients. The add-on intervention encompasses three core elements:

1. Assigning a contact person with specific responsibilities (e.g., ensure the patient feels safe and welcome at the first session, and acting as a contact in case of cancellation)
2. Systematically communicating patient information to colleagues in the CR team
3. Systematic follow-up (e.g., maintaining continuous contact in case of cancellation/absence, and ongoing follow-up).

The add-intervention will be described in detailed in accordance with the Template for Intervention Description and Replication (TIDieR)

Both quantitative (data from the identification form) and qualitative methods (data from feedback meetings with healthcare professionals) will be used to collect data. Process data will be collected continuously over a six-months period and at the study's conclusion, focussing on three dimensions: implementation (reach and fidelity), acceptability, and mechanism of impact. Descriptive statistics will be used to analyse implementation data, while content-driven analysis will be applied to assess acceptability and mechanisms of impact. Based on clinical and research judgment, a convenience sample of at least 150 cardiac patients referred to CR was deemed sufficient to adequately represent the target population and provide data for the feasibility study.

According to Danish legislation and the Act on Biomedical Research Ethics Committee System in Denmark, research without human biological material does not require approval from an ethics committee (§14 Section 2). The study was registered and approved by the Data Protection Agency of Central Denmark Region (1-16-02-121-24). Cardiac patients and healthcare professionals provide written informed consent to participate in the co-production process, like participants in the feasibility test.

If the feasibility study yields promising results, a larger-scale study will be conducted to evaluate the Heart Priority Programme's overall impact on dropout rates in cardiac rehabilitation.

Inclusion Criteria:

• patients with acute coronary syndrome
• age >18 years
• patients referred to CR in community healthcare services
• patients living in Central Denmark Region
• patients at risk of dropout due to being in a vulnerable situation.

Exclusion Criteria:

• age < 18