I have a heart defect (mitral valve prolapse) that, if I understand it right, is benign. One side effect is that EKGs will always be inaccurate. If a doctor doesn't know this, they get alarmed at my EKG. When they really need to know how my heart is doing, they do an echo-cardiogram which is far more extensive and expensive. Anyway, I don't need the ability in a watch, because the data it produces will probably not be useful.