To determine the incidence and predictors of true arrhythmia in pediatric patients presenting with concerns about smartwatch cardiac data.

Single-center, retrospective cohort study of children aged 10-18 years who had presented to a pediatric cardiology clinic between January 2018 and December 2021 with concerns related to smartwatch cardiac data. The primary study outcome was diagnosis of arrhythmia based on clinical evaluation or documentation of arrhythmia by clinical testing.

There were 126 patients (mean age 15.6 ± 2.4 years) who presented with a smartwatch-based rhythm concern, with tachycardia in 89%. In all, 19 of 126 (15%) patients were diagnosed with true arrhythmia. The odds of a true arrhythmia diagnosis with symptoms vs no symptoms were 3.2 (95% CI 0.7-14.5), and with heart rate (HR) ≥190 beats/min vs HR <190 beats/min, it was 14.3 (95% CI 3.8-52.8). The positive predictive value of HR ≥190 beats/min and symptoms together to predict arrhythmia was only 39% (95% CI 28-52). The negative predictive value for arrhythmia having neither symptoms nor HR >190 was 95% (95% CI 75-99).

The likelihood of a true arrhythmia in pediatric patients presenting with a smartwatch-based HR concern was low. Rarely, smartwatch electrograms or trend data were sufficient for arrhythmia diagnosis.