These new AI chatbots are pretty helpful now. They can easily replace things like reddit and make Internet searches much easier. I asked. the “chatbot” perplexity.ai the same question as this post and got this answer (Perplexity.ai is free and do not require an account and searches in real time on current data):

"According to multiple studies, the accuracy of the ECG feature on the Apple Watch varies depending on the study and the condition being tested. Here are some key findings:

• One study by a Stanford Associate Professor of Medicine demonstrated that the Apple Watch could accurately detect atrial fibrillation (AFib) in 84% of cases when compared to a traditional 12-lead ECG[4].
• Another study showed that the Apple Watch single-lead ECG had a high accuracy to identify AFib and sinus rhythm[1].
• However, a study showed that a single-lead ECG measured using a KardiaBand paired with an Apple Watch had only “moderate diagnostic accuracy” in diagnosing AFib compared to a 12-lead ECG in the hospital[3].
• Yet another study assessed the Apple Watch ECG’s accuracy in detecting AFib in patients who had undergone cardiac surgery. The study showed a sensitivity of 41% for the abnormal rhythm notification from the Apple Watch Series 4 and a sensitivity of 96% for the single-lead ECG downloaded as a PDF, compared to telemetry[3].
• The ability of the Apple Watch ECG to detect abnormalities related to cardiac ischemia was limited[5].
• Apple’s ECG application is a much simpler single-lead ECG with limited capabilities. It won’t help detect most heart rhythm abnormalities or worsening heart failure. It also won’t reliably detect the electrical changes associated with a heart attack[6].

In summary, the accuracy of the ECG feature on the Apple Watch varies depending on the study and the condition being tested. While some studies have shown high accuracy in detecting AFib and sinus rhythm, other studies have shown moderate diagnostic accuracy in diagnosing AFib compared to a 12-lead ECG in the hospital. It is important to note that the ECG feature on the Apple Watch is not a substitute for professional medical advice and diagnosis. If you are experiencing symptoms, it is recommended to discuss them with your healthcare provider as soon as possible to rule out underlying heart conditions.

Citations: [1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9795256/ [2] https://www.cnet.com/tech/mobile/apple-watch-ecg-ekg-watchos-vs-hospital-medical-grade-detected-strange-heart-rhythm/ [3] https://www.gehealthcare.com/insights/article/ecg-watch-accuracy-and-the-question-of-data-overload [4] https://www.qaly.co/post/how-accurate-the-ecg-is-on-your-apple-watch [5] https://www.ahajournals.org/doi/full/10.1161/CIRCEP.120.009260 [6] https://www.cnn.com/2018/12/06/health/apple-watch-ecg-app-review/index.html"