Background: Cardiovascular disease is one of the leading causes of disability worldwide. eHealth has the possibility to improve health outcomes and quality of life adjunct to regular care. “The Myocardial Infarction Box” (MI Box) is an at home monitoring system using smartphone-enabled health monitoring devices. However, like many eHealth interventions, the MI Box had variable adherence This variable adherence could be due to a misalignment with the needs of the users and the intervention. Through co-creation, this study aims to develop design strategies to enhance the effectiveness of the MI Box in the long term: to increase adherence in the first year and support MI patients in adopting a healthy lifestyle. Methods: Six iterative co-creation session were conducted with various stakeholders. One with designers and with healthcare professionals. Four sessions with users. In these sessions, the patient journey and patient personas were discussed to identify needs and opportunities for enhancements to the intervention. Furthermore, design strategies for enhancing the intervention, aiming both to optimize adherence and to stimulate a healthy lifestyle, were discussed. Findings: This resulted in themes such as personalized feedback, understanding the data, and regaining confidence in one’s own body to be key aspects to creating a more meaningful and personally relevant intervention. Discussion: Involving the stakeholders in co-creation sessions provides invaluable insights into the userexperiences and opportunities for personalization. Adapting the intervention to these needs is the next step to increase engagement with the intervention and thereby increase adherence. @en