Wearable Irregular Heart Rhythm Detection Recurrences and Electrocardiographic Atrial Fibrillation Confirmation: The Fitbit Heart Study.

BACKGROUND

Wrist-worn wearables can detect irregular heart rhythms using photoplethysmography, but ECGs are required to confirm atrial fibrillation (AF). We sought to determine the frequency of a recurrent irregular heart rhythm detection (IHRD; ≥30 minutes of an irregular rhythm), estimate the potential diagnostic yield of different electrocardiographic monitoring strategies for confirming AF, and identify predictors of recurrent IHRDs.

METHODS

The Fitbit Heart Study enrolled wrist-worn photoplethysmography device users without diagnosed AF. Of 455 699 participants, 1057 who wore and returned a 1-week ECG patch monitor after receiving an IHRD were analyzed. Baseline clinical data, device-derived metrics, IHRDs during follow-up, and electrocardiographic patch data were used for analysis.

RESULTS

A total of 570 (53.9%) participants were aged 40 to 64 years, 422 (39.9%) were aged ≥65 years, and 510 (48.2%) were women. Median follow-up after ECG patch initiation was 80 days (interquartile range, 45-122 days). The frequency of another IHRD was 57.2% (95% CI, 53.1%-60.9%) at 3 months. After an initial IHRD, the estimated diagnostic yield for AF with a 10-second ECG was 7.6% (95% CI, 6.2%-9.0%), twice-daily 30-second ECGs over 1 week 19.0% (95% CI, 16.7%-21.2%), 24-hour monitor 17.4% (95% CI, 15.5%-19.3%), 1-week monitor 32.2% (95% CI, 29.4%-35.0%), 2-week monitor 46.8% (95% CI, 42.7%-50.8%), and 4-week monitor 60.8% (95% CI, 56.5%-65.1%). The risk of a recurrent IHRD was greater with older age (P<0.001), male sex (P=0.001), vascular disease (P=0.03), longer initial runs of consecutive IHRDs at detection (P=0.02), and less nightly sleep (P=0.03).

CONCLUSIONS

Irregular heart rhythms are common after initial detection using a wrist-worn wearable device. Longer electrocardiographic monitoring periods increase the likelihood of confirming AF.

REGISTRATION: URL: https://www.clinicaltrials.gov; Unique identifier: NCT04380415.