Objective: The objective of the current study was to develop and evaluate a persuasive decision-support aiming at reducing pre hospital delay and increasing ambulance service use for patients who suffer from a recurrent myocardial infarction. Materials and methods: The system was developed as a prototype mobile application for smartphones. The system was evaluated by four end-users with previous experience of myocardial infarction. The user tests were complemented with cognitive walkthroughs and heuristic evaluation. Results: A total of 14 persuasive design principles were used to guide the design of the system. The usability was regarded as high with an average score of 82 on the System Usability Scale. The users reported that they found the system highly persuasive. Conclusions: User-centered design together with persuasive design principles through iterative testing and development has resulted in a prototype app with potential to improve patients care seeking behavior. The content in the prototype will be further evaluated before it is integrated in educational interventions.