Smartwatch-Based Heart Rate Detection in Atrial, Ventricular and Pulseless Arrhythmias

Smartwatches can provide a non-invasive heart rate (HR) monitoring to aid screening for atrial fibrillation, however, the accuracy of HR detections in the context of other arrhythmias requires further investigation. We aimed to assess the accuracy of HR measurements of two commonly used wearables at onset, during and termination of various induced and paced arrhythmias.

Patients undergoing an electrophysiology study were fitted intraprocedurally with both the Apple Watch Series 4 (AW) and Fitbit Versa (FB). Detected HRs on the devices were recorded at initiation, during, and at termination of various paced and induced arrhythmias. True HR was confirmed via intracardiac electrograms and 12-lead electrocardiogram. Detected HRs on the AW and FB were assessed for accuracy, defined as HR with in ±10% of the true rate.

A total 322 cardiac rhythms from 32 patients were analysed. Both AW and FB demonstrated reasonable HR detection during sinus rhythm (100% vs 87%; p=0.04) and supraventricular tachycardia (SVT) (89% vs 86%; p=1). Both devices performed poorly at detecting SVT termination (62% vs 41%; p=0.04) and ventricular tachycardia (41% vs 16%; p=0.007). Neither device identified changes in HR during ventricular fibrillation or asystole.

Both the Apple Watch and Fitbit demonstrate reasonable accuracy in HR detection during regular rhythms of supraventricular origin, however, struggle with arrhythmia terminations and ventricular arrhythmias. Care should be taken when assessing HR trends for presence of cardiac arrhythmias.