CNET senior reporter Vanessa Hand Orellana sits in a consultation room at UCSF Medical Center in San Francisco while cross-referencing Apple Watch's new electrocardiogram feature readings with medical-grade EKG equipment.
"The last thing I expected was to find something abnormal with my heart rhythm," she says.
With the update to WatchOS 5.1.2, heart rate will play a more important role on the Apple Watch as the device gets access to the two new FDA-cleared features: an abnormal heart rhythm alert for all models, except for the first-generation, and an electrocardiogram (EKG or ECG) exclusive to the Series 4.
The latest update to Apple Watch, WatchOS 5.1.2, rolled out the two new features, both of which could help warn of potentially life-threatening heart conditions.
A technician connects the series of 12 electrodes used in the hospital during a standard medical EKG heart test.
The EKG on the Apple Watch directly coincided with the results of the hospital EKG that Dr. Gregory Marcus, a professor of medicine and a cardiac electrophysiologist at UCSF Medical Center, had printed out. Both devices showed intermittent early beats coming from the upper right ventricle of Vanessa's heart.
The results from the Apple Watch on the iPhone were compared to the 12-lead EKG results on paper.
"This would be really useful to screen for this or to have the first understanding that you have these early heart beats," said Marcus.
"What's missing in the single lead Apple Watch is the information that tells us more specifically where exactly this is coming from."
"We see on your Apple Watch the same early heartbeat that we see on the EKG," said Marcus during CNET's testing.
Examining the results of the Apple Watch EKG alongside the test of the more advanced medical EKG device at the UCSF Medical Center
Marcus says the results displayed on both devices are concerning for Vanessa. He wants to follow up with her about the early beat that was detected.
For people with more serious heart conditions, this could help doctors make a faster diagnosis and allow them to treat the problem sooner.
The irregular heart rhythm notification is already available on all Apple Watches starting with the Series 1 and can be set up in the Heart section of the Watch app.
The EKG app is only available on the Apple Watch Series 4 and is only available in the US, though Apple expects to get regulatory approval for this feature in other countries later on.