Monitoring and modulating cardiac bioelectricity: from Einthoven to end-user

In 2024, we celebrate the 100th anniversary of Willem Einthoven receiving the Nobel Prize for his discovery of the mechanism of the electrocardiogram (ECG). Building on Einthoven's legacy, electrocardiography allows the monitoring of cardiac bioelectricity through solutions to the so-called forward and inverse problems. These solutions link local cardiac electrical signals with the morphology of the ECG, offering a reversible connection between the heart's electrical activity and its representation on the body surface. Inspired by Einthoven's work, researchers have explored the transition from monitoring to modulation of bioelectrical activity in the heart for the development of new anti-arrhythmic strategies, e.g. via optogenetics. In this review, we demonstrate the lasting influence that Einthoven has on our understanding of cardiac electrophysiology in general, and the diagnosis and treatment of cardiac arrhythmias in particular.