More than 419,000 Apple Watch users have signed up for the unusual study, making it the largest ever to explore the screening of apparently healthy people for atrial fibrillation, a condition that if left untreated can eventually trigger stroke.
Researchers at Stanford University reported that the clock did not blow up the flocks of people, warning only half the participants – about 2,100 – that they could have a problem.
But even among those reported, "it is not perfect", warned dr. Richard Kovacs of the American College of Cardiology, who was not involved in the study.
People who received a warning had to consult a study doctor via telemedicine and then wear an ECG patch that measures cardiac activity for the following week to determine the accuracy of the watch. Some skipped the virtual check-up to consult their doctors; overall, around 57 percent required medical treatment.
Among those who obtained ECG monitoring through the study, one-third had atrial fibrillation, based on preliminary results presented at a conference of the American College of Cardiology in New Orleans.
A-fib tends to come and go, and a week of monitoring may have lost some cases, said chief researcher Stanford Dr. Mintu Turakhia. But if the clock detected another irregular heartbeat while someone was wearing the EKG patch, 84 percent of the time it was really a fib, he said.
"This study, in our opinion, provides very encouraging evidence that a device, the Apple Watch, can be used to detect fibers and to alert people when further checks or tests may be needed," said Dr. Lloyd Minor, dean of Stanford medicine.
Other cardiology experts said the study, funded by Apple, suggests that wearable technology screening could be technically feasible in the end, but needs much more research.
"I would not recommend this to the general general population," said Dr. Valentin Fuster, director of Mount Sinai Heart in New York and a former president of the American Heart Association, who was not involved in the study. Instead, he would like to see him tested in the elderly with risk factors such as hypertension.
WHAT IS ATRIAL FIBRILLATION?
A-fib occurs when the upper chambers of the heart, called atria, come out of sync with the pumping action of the lower chambers. Sometimes patients feel a heartbeat or a heartbeat, but many times I am not aware of an episode.
Sometimes the heart regains its rhythm by itself. Other patients experience an electric shock to return to the rhythm, or blood thinners are prescribed to counteract the blood clots that cause the stroke that cannot be stimulated. A-fib causes 130,000 deaths and 750,000 hospitalizations per year in the United States.
HOW DO THE PHYSICIANS VERIFY IT?
The A-fib is more common in the elderly and other risks include hypertension or a family history of arrhythmias. But routine screening is not recommended for people without symptoms. Studies have not yet shown that early detection of screening could prevent a sufficient number of strokes to overcome the risks arising from unnecessary tests or over-tests.
HOW DO YOU DISPLAY THE APPLE WATCH?
A mobile app uses the optical sensor on some versions of the clock to analyze pulse rate data. If it detects a sufficient change from beat to beat over a period of 48 hours, the user receives a warning of an irregular heart rhythm.
The latest version of Apple Watch also allows users to press a button to take an ECG and share the reading with the doctors. Saturday's study did not include watches with that ability.
IS THE NEW STUDIO SHOW MASS PROJECT A GOOD IDEA?
No. The study was designed to indicate the watch with respect to a week of standard ECG monitoring, not if the wearer's health has improved because screening has discovered arrhythmia. To demonstrate whether the detection of an initial risk fib lowers the risk of stroke take years of study.
And since the study didn't have a control group that got routine ECGs, there's no way to tell if the clock lost heartbeat problems, giving a false sense of security, has called Kovacs.
The staggering number of alarms could be due to the fact that most of the participants were young or middle-aged, not the elderly who are most at risk for a fib, he said.
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