I flatlined for 19 seconds. I might not have woken up." Apple's electrocardiogram (ECG) app was introduced with the Apple Watch Series 4 in 2018. The functionality is similar to a single-lead ...

That’s because doctors check the rhythm of your heart with a machine called an electrocardiogram -- also called an ECG or EKG ... they sometimes shock a flatlined heart with a defibrillator.