The electrocardiogram (ECG) feature on the Apple Watch is generally considered to be accurate, but it is not perfect.
The ECG feature uses the heart rate sensor and electrodes on the back of the watch to measure the electrical activity of the heart and display a tracing on the watch face.
The accuracy of the ECG feature is dependent on a number of factors, including the quality of the electrodes and the reliability of the heart rate sensor. In general, the ECG feature on the Apple Watch has been shown to be comparable to a traditional ECG machine in terms of accuracy.
However, it is important to note that the Apple Watch is not a medical device, and it should not be used for making medical diagnoses or decisions. If you are concerned about your heart health, it is best to consult with a healthcare provider.