Sequential Smartwatch Readings for Atrial Fibrillation Have High Detection Rates

Joseph Weisel, MD

New data suggest a wearable with an algorithm that takes 3 sequential atrial fibrillation readings every day with all readings having shown atrial fibrillation for a positive AF >24 hour result can detect 95% of episodes with few false positive readings.

“Therefore, screening for [atrial fibrillation] should be designed to only detect AF>24h and if AF<24h is detected, it should be considered clinically insignificant and a “false positive,” wrote study author Joseph Weisel, MD, NYU Langone Health.

The findings were presented at The American College of Cardiology (ACC) 2022 Scientific Sessions in Washington, DC.

Previous studies have suggested that atrial fibrillation that lasts more than 24 hours increases the risk of stroke, while anticoagulating patients with shorter episodes of atrial fibrillation do not prevent strokes.

Screening methods such as smartwatches with pulse and electrocardiogram atrial fibrillation detection capability are promising new advancements. A pulse could be used for automatic screening for atrial fibrillation, while the electrocardiogram could be used to confirm the heart arrhythmia.

Investigators performed an analysis of a single year of simulated screening for atrial fibrillation >24 hours in eldery patients using a wearable smartwatch. They additionally used reported data for the Apple Watch electrocardiogram (sensitivity 98.3%; specificity 99.6%).

From published data from the LOOP natural history study, investigators estimated the likelihood of detecting episodes of clinically insignificant atrial fibrillation in an eldery population. These were based on an estimate of the mean time per patient of atrial fibrillation <24 hour (burden 0.6%).  Then, the sensitivity used for detecting the first episode of atrial fibrillation >24h was equal to electrocardiogram sensitivity.

Additionally, specificity for atrial fibrillation >24 hour was the electrocardiogram specificity of 99.6% reduced by detection of atrial fibrillation <24 hour which is 0.6%, with a final specificity of 99.0%. Investigators extrapolated daily probability over a full year (365 days) to get annual outcomes.

Data show once a day readings over the full year would detect 98.3% of the first atrial fibrillation >24 hour episodes, while the probability of at least one false positive reading in 365 days would be 98%.

Further, readings twice a day or three times a day would result in slightly lower sensitivity of 87% and 95% respectively. Over one year, the likelihood of at least one false positive reading would be reduced to 4% and 0.04%, respectively.

The abstract, “Optimal Screening For Atrial Fibrillation Using a Smartwatch,” was presented at ACC 2022.