Smart watches for heart rate assessment in atrial arrhythmias

Background: Despite studies demonstrating the accuracy of smart watches (SW) and wearable heart rate (HR) monitors in sinus rhythm, no data exists regarding their utility in arrhythmias.

Methods: 102 hospitalized patients were evaluated at rest using continuous electrocardiogram (ECG) monitoring with concomitant SW-HR (FitBit, FB, Apple Watch, AW) for 30 min.

Results: Across all devices, 38,616 HR values were recorded. Sinus rhythm cohort demonstrated strong agreement for both devices with a low bias (FB & AW Bias = 1 beat). In atrial arrhythmias, AW demonstrated a stronger correlation than FB (AW r_s = 0.83, FB r_s = 0.56, both p < 0.01) with a lower bias (Bias AW = -5 beats, FB = -18 beats). Atrial flutter demonstrated strongest agreement in both devices with a mean bias <1 beat. However, in AF, there was significant HR underestimation (Bias FB = -28 beats, AW-8 beats) with wide limits of agreement. Despite HR underestimation in AF, when SW recorded HR ≥ 100 in arrhythmias, 98% of values were within ±10-beats of ECG-HR.

Conclusions: SW demonstrate strong agreement for HR estimation in sinus rhythm and atrial flutter but underestimates HR in AF. Tachycardic episodes recorded at rest on a SW may be suggestive of an underlying atrial tachyarrhythmia and warrant further clinical evaluation.

Clinical trial registration: Australian New Zealand Clinical Trials Registry (www.anzctr.org.au) ACTRN: 12616001374459.