This is the study Apple did with Stanford. It's based on the photoplethysmograph (PPG) sensor from the pre-Series 4 Apple Watches. Presumably the new Apple hear

This is the study Apple did with Stanford. It's based on the photoplethysmograph (PPG) sensor from the pre-Series 4 Apple Watches. Presumably the new Apple heart study announced will also use the ECG in the Series 4 and later [1]. [1] https://www.apple.com/newsroom/2019/11/apple-launches-three-innovative-studies-today-in-the-new-research-app/ https://www.apple.com/newsroom/2019/11/apple-launches-three-...