The main objective of this application is to develop a comprehensive approach for rare disease registration in ERN GUARD-Heart by establishing the first overarching registry of ERN GUARD-Heart (the Heart-Core Registry) using standards and tools provided by the European Platform on Rare Disease Registration (EU RD Platform). To harmonize data and facilitate semantic interoperability, in the Heart-Core Registry a minimal dataset (including the Set of Common Data Elements for Rare Diseases Registration provided by the European Commission’s Joint Research Centre) will be prospectively collected for new patients in the ongoing ERN GUARD-Heart registries and in the future ERN GUARD-Heart registries. In addition, the Heart-Core Registry will signpost users to the detailed disease- or gene-specific ERN GUARD-Heart registries. To render its data more searchable and findable, the Heart-Core Registry will be registered on the European Rare Disease Registry Infrastructure (ERDRI). It is expected that the activities proposed in this application will facilitate ERN GUARD-Heart to reach its goals and specific objectives, create a cost-effective and comprehensive approach of rare disease registration in the ERN GUARD-Heart, lead to increased awareness of ERN GUARD-Heart patient registries and improved reusability of data in these registries among various stakeholders, and enable better interaction among rare disease registries in Europe.