A new analysis of data from Apple’s joint heart study with Stanford found that the Apple Watch is capable of detecting more arrhythmias than we thought.
The Apple Heart Study is designed to test the Apple Watch’s ability to detect abnormal heart rhythms. Participants whose watches informed them of possible cardiac arrhythmias received an EKG patch that monitors their heart rhythm over a longer period of time. The data showed that the watch was pretty good at detecting certain arrhythmias, including atrial fibrillation. Case closed; Marketing and law can sleep soundly. This story is not a bomb. It’s about the value of the data that would otherwise be ignored.
What this new look at the Apple Heart Study data revealed is that while the watch did what it said it was also able to detect several other important patterns in the participants’ heartbeats – patterns the researchers didn’t had been looking for the original study. Many participants had additional out-of-rhythm atrial or ventricular contractions. “Even if you didn’t find atrial fibrillation, we found a lot of people who had something else that probably required some clinical attention,” said Marco Perez, director of the Inherited Arrhythmia Clinic at Stanford University Medical Center.
According to the new study (PDF), about a third of the 400,000 participants who had initially received the warning of cardiac arrhythmias eventually also showed atrial fibrillation (a-fib). Another 40 percent were diagnosed with a different type of arrhythmia. The report also found that nearly a third of study participants who were not diagnosed with a-fib after receiving the arrhythmia warning later said they had been diagnosed with the condition outside of the study. Once a person detects an arrhythmia, they will likely need future attention. This is what scientists mean when they say that things “fall out of the data”.
Atrial fibrillation is strongly associated with a high risk of stroke. Fibrillation can also be called “flutter,” and during atrial fibrillation the apex of the heart can beat and flutter rapidly. Sometimes you can feel it, sometimes you don’t. It causes turbulence in the atrium and can tear platelets, which can form a clot in the blood vessels that leads to an embolism or stroke. The risk is small with any single fibrillation event, but it will add up over time. I have my father’s A-fib; I take care of it.
Like the optical devices they use in a hospital to find a vein before blood is drawn, the Apple Watch’s EKG relies on optics to do its job. It lights up the skin, and then measures the tiny changes in skin color as blood goes in and out with the pulse. After that it’s just software pattern recognition. The technology is not the revolution here. For a person monitoring their heart health, subtle signals are often important. A false positive is much less bad than a free stay in the intensive care unit.
The result of all this is that cardiologists are unsure how to respond to all of these detected patterns, but the EKG technology used in the Apple Watch has been thoroughly tested and proven to be effective. It’s not a silver bullet, but for those looking for this feature, it can help you keep a keener eye on the kind of heart problems that can really ruin your day later in life.