DataTools4Heart_Milestone MS17_CardioSynth synthetic dataset for cardiology generated and provided open-access on the DT4H platform for the community

This milestone document reports the status of CardioSynth, the multi-centre, multilingual and fully synthetic heart-failure dataset produced by DataTools4Heart (DT4H). It briefly reported the methods and results of the full CardioSynth report into three questions: why CardioSynth was built, how it is generated, and what it consists of today (September 2026). CardioSynth is generated inside the secure environment of each participating hospital from adult heart-failure hospitalisations extracted through the DT4H Common Data Model. One pipeline produces structured synthetic records with nine families of generative models, evaluates them against the natural variability between two real samples (the noise floor) and a suite of privacy attacks, and passes every candidate file through an automated release gate. A second pipeline writes one clinical note per synthetic patient, in the language of the centre and in the style of clinician-authored documents about fictional patients, so that no real patient text is ever used. Structured and unstructured generation is complete or ongoing at several centres and planned at the others. The first version of CardioSynth (i.e CardioSynth v1.0) includes data generated with two methods (TVAE and MST) for structured data and derived notes from four clinical centres. Following approval from the local officers, CardioSynth will therefore be released in tiers: open documentation, code and evaluation evidence; gate-cleared synthetic data under a data use agreement on the DataTools4Heart platform; and tailored cohorts generated on request inside the hospitals. The route to a fully open release, and the governance decisions it requires, are described in the final section. Full details of the pipeline to build CardioSynth are published in the Deliverable 7.2 (same date of publication).