Accuracy of wearable heart rate monitors in cardiac rehabilitation

Muhammad Etiwy, Zade Akhrass, Lauren Gillinov, Alaa Alashi, Robert Wang, Gordon Blackburn, Stephen M. Gillinov, Dermot Phelan, A. Marc Gillinov, Penny L. Houghtaling, Hoda Javadikasgari, Milind Y. Desai


Background: To assess the accuracy of four wearable heart rate (HR) monitors in patients with established cardiovascular disease enrolled in phase II or III cardiac rehabilitation (CR).
Methods: Eighty adult patients enrolled in phase II or III CR were monitored during a CR session that included exercise on a treadmill and/or stationary cycle. Participants underwent HR monitoring with standard ECG limb leads, an electrocardiographic (ECG) chest strap monitor (Polar H7), and two randomly assigned wrist-worn HR monitors (Apple Watch, Fitbit Blaze, Garmin Forerunner 235, TomTom Spark Cardio), one on each wrist. HR was recorded at rest and at 3, 5, and 7 minutes of steady-state exercise on the treadmill and stationary cycle.
Results: Across all exercise conditions, the chest strap monitor (Polar H7) had the best agreement with ECG (rc=0.99) followed by the Apple Watch (rc=0.80), Fitbit Blaze (rc=0.78), TomTom Spark (rc=0.76) and Garmin Forerunner (rc=0.52). There was variability in accuracy under different exercise conditions. On the treadmill, only the Fitbit Blaze performed well (rc=0.76), while on the stationary cycle, Apple Watch (rc=0.89) and TomTom Spark (rc=0.85) were most accurate.
Conclusions: In cardiac patients, the accuracy of wearable, optically based HR monitors varies, and none of those tested was as accurate as an electrode-containing chest monitor. This observation has implications for in-home CR, as electrode-containing chest monitors should be used when accurate HR measurement is imperative.