Fitbit app can detect undiagnosed atrial fibrillation: study

New results of a large study suggest that an algorithm for Fitbit watches can correctly detect previously undiagnosed atrial fibrillation (AF) in wearers, with a a positive predictive value of 98%. About a third (32%) of people who had an irregular health rhythm detected by the Fitbit algorithm were eventually found to have undiagnosed AF. The new study involved adult Fitbit users in the in the U.S. with no history of atrial fibrillation (AF). The results add to previous research showing the Apple Watch app was successful in identifying atrial fibrillation. “I believe that both of these algorithms identify patients or participants or consumers early in the course of the disease,” said Dr. Mintu Turakhia, director of the centre for digital health at Stanford University. The Fitbit algorithm uses information from pulse photoplethysmography (PPG) signals. It samples the pulse continuously but only analyses the data when accelerometers detect the wearer is at rest. If there are 11 consecutive five-minute-long tachograms that are irregular, it is flagged as an irregular heart rhythm detection (IHRD). Those with an irregular heart rhythm detection (IHRD) were invited to sign up for a telehealth visit and, after a screening process, were mailed a one-week ECG patch monitor. Of the 455,699 people participating in the study, 4,728 were notified of an irregular heart rhythm detection. Of these, 1,057 returned the ECG monitor so their data could be analyzed, and 340 were found to have AF. The positive predictive value of AF using this software algorithm was 97% in participants who were 65 years old and older, which suggests a potential benefit for people at highest risk for stroke, said Dr. Steven Lubitz, a cardiologist at Massachusetts General Hospital and lead investigator of the Fitbit Heart Study. The median burden of AF was 7% and the median longest episode measured by the ECG patch was seven hours, he reported. Read: Apps to improve our lives Dr. Hariette Van Spall, cardiologist and associate professor of medicine McMaster University in Hamilton, Ont., said the study shows there are “lots of possible applications of this wearable technology beyond tracking for personal fitness.” Dr. Van Spall noted that of the 4,728 who were invited to attend a telehealth appointment, only 1,700 did, and fewer got an ECG. Dr. Lubitz said this lack of engagement was a problem with trials conducted remotely. “Engagement of participants is critical but may be a challenge at a distance at times,” Dr. Lubitz said. “Similar situations have been seen before in large-scale remote clinical trials.” End-of-study survey results are still being analyzed. The answers may provide more information on patients’ contact with the health care system outside of the trial. Dr. Turakhia pointed out the algorithm does not provide “classical screening as we think about in public health,” but a consumer-targeted opt-in screening. The big problems is engagement, he said, adding that it could be a useful tool people who have an increased likelihood of AF. Post-marketing surveillance may provide more data on who may benefit most from the monitoring. The Apple Watch study was published in the New England Journal of Medicine in 2019. It had a similar number of participants and 34% of people notified about an irregular heart rhythm were subsequently found to have undiagnosed AF. The positive predictive value for observing AF ON ECG was 84%. The Apple Watch app algorithm looked at one-minute-long tachograms and notified those with irregular five out of six discrete tachograms. There were some fears that the Apple Watch app would increase the number of visits to primary care and an increase in the diagnosis of AF. Researchers from Harvard University found there was no difference in the number of physician visits that resulted in a diagnosis of AF before and after the app was released in December 2018. Their paper was published in Circulation in 2020. A third study by Huawei Technologies involved an app where monitoring had to be turned on by wearers. Results were published in the Journal of the American College of Cardiology in 2019. Read: Coffee may not trigger atrial fibrillation episodes: study

Fitbit app can detect undiagnosed atrial fibrillation: study

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