Rutger Hassink works as a cardiologist in the UMC Utrecht. He is specialized in the field of clinical electrophysiology. During his daily work he treats patients with cardiac arrhythmias with ablation therapy. And he implants pacemakers and internal defibrillators. At the outpatient cardiogenetics clinic he examines patients with more common but also rare heart disease. Ever since the start of his academic career, the (often rare) cardiac arrhythmias with unknown cause have been intriguing him. As a principal investigator, he leads a large national cohort-study of patients known with ‘idiopathic ventricular fibrillation’ (CVON Dutch Heart Foundation: Vigilance: non-invasive electrocardiographic imaging for individuals at risk for apparently idiopathic ventricular fibrillation; collaboration of the university hospitals of Utrecht, Maastricht, Amsterdam). A rare clinical picture in which previously healthy patients are suddenly attacked by cardiac arrest due to fibrillation of the ventricles. Despite extensive diagnostics, no cause (= idiopathic) is found in these patients. Thanks to his research, causes have nevertheless come to light in various patients. Which can not only have consequences for the (treatment of the) patient her/himself, but also, for example, for their family. The usage of deep neural networks for ECG interpretation will hopefully lead to further unravelling the etiology of ventricular fibrillation in the other patients.