Apple Watch marks several types of irregular heartbeat, study shows

People who get irregular heartbeats on an Apple Watch but do not have atrial fibrillation – the condition the feature focuses on detecting – could still have another type of problem with their heartbeat, according to a new study.

The results show that even if someone with a worrying alarm from their Apple Watch does not get an atrial fibrillation diagnosis, they may not be clear, says study author Marco Perez, director of the Inherited Arrhythmia Clinic at Stanford University Medical Center. “Even if you did not find the atrial fibrillation, we found many people who had something else that probably needed clinical attention,” he says.

The analysis, published in the journal Circulation, was performed using data from the Apple Heart Study, which was designed to test the Apple Watch’s ability to detect irregular heartbeats. It was launched in 2017 and included over 400,000 participants. In the study, everyone who received an irregular heart rate message from the watch was sent a clinical ECG patch that could monitor their heart rate over an extended period of time. About 2,000 participants received an irregular heartbeat message, and a previous analysis showed that about one-third of the people who then wore an ECG patch had atrial fibrillation appear during this monitoring period.

This new study looked at ECG patch data from the remaining participants did not do has detected atrial fibrillation. “If we did not find the atrial fibrillation – what did we find then?” Says Perez. About 40 percent of these people had another type of irregular heartbeat, including premature atrial contractions (extra heartbeats coming from the top of the heart) and premature ventricular contractions (extra heartbeats from the bottom of the heart). “They had a lot of those extra heartbeats,” he says. “Those are things we are aware of.”

Cardiologists still do not have a good understanding of how dangerous those kinds of frequent extra heartbeats can be, and often do not agree on how or whether they should be treated, Perez says. They have been linked to the development of atrial fibrillation and heart failure, but there is no clear understanding of the best way to deal with them.

The study also showed that nearly one-third of study participants who did not have atrial fibrillation detected on the ECG patch said they eventually continued to be diagnosed with the condition outside the study. So even if someone does not get a diagnosis on an initial evaluation, it may make sense to keep an eye on them in the future. “We should probably start thinking about the best strategy to follow these patients over time,” Perez says.

Right now, there is a wide range of responses to this type of warnings. If someone tells a cardiologist that they had an irregular heartbeat message, the doctor may be able to perform a quick, 10-second ECG check in the office. Other doctors may send them home with a patch for a week. Still others, if there are other factors that make them suspicious, may want to monitor in the long run. The technology is still new and the approach is still evolving, Perez says.

Further research will help refine the approach. But for now, this study suggests that people who get irregular heart rate alerts should keep an eye on their heart health, Perez says. “There may very well be something going on that may cause you to have an irregular heartbeat and could be a sign that something is wrong with your heart.”

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