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. 2021 Jul 19;37(1):188–197. doi: 10.1007/s11606-021-07007-w

Figure 3.

Figure 3

Schematic demonstrating the algorithm used by the early version of the Apple Watch, which was featured in the Apple Heart Study. When a user is at rest, the watch generates a 60-second tachogram. If irregularity is noted, the device will trigger subsequent tachograms; if five of six tachograms are irregular, the user receives a notification of an irregular heart rate. Importantly, more contemporary versions of the Apple Watch include both PPG (shown here) and ECG (not shown here) features.