Lots of skeptical doctors were saying that it'd cause a lot of hypochondriacs and false positives to overwhelm the system. Did this actually happen? Personally I read the documentation that Apple released about how the ECG and the irregular heart rhythm notifications worked, so I predicted it wouldn't happen. Curious to get everyone's take though.
The ECG app waveform is similar to a Lead I ECG, which can enable classification of atrial fibrillation and sinus rhythm, but cannot identify other conditions, like heart attacks.
After taking an ECG reading, the ECG app will check for sinus rhythm or AFib. If the heart rate is under 50 bpm or over 120 bpm, the app is unable to check for AFib, but will note the heart rate and save the ECG recording. The ECG app may provide an inconclusive result if, for example, there is poor signal due to motion artifacts or poor electrode contact, the heart rate is between 100 and 120 bpm, or for other reasons such as presence of arrhythmias other than AFib, presence of an ICD or pacemaker, or poor electrical signal in the recording which can occur as a result of right axis deviation.
In a clinical study, the rhythm classification by the ECG app of a single lead ECG on Apple Watch was compared to the rhythm classification by a cardiologist of a simultaneously collected 12-lead ECG. The ECG app demonstrated 99.6% specificity in classifying sinus rhythm and 98.3% sensitivity in classifying AFib for the classifiable results. In this study, 12.2% of recordings were not classifiable.
Source: Original link