JMIR Publications

ABSTRACT

Background:

Wearable devices present a promising alternative for remotely monitoring heart rate (HR) during home-based cardiac rehabilitation. However, evidence on their accuracy across different exercise intensities and patient profiles is limited, particularly in cardiovascular disease (CVD) populations such as those with heart failure (HF).

Objective:

To assess the accuracy of HR measurements obtained by the Fitbit Inspire 3 during cardiopulmonary exercise testing (CPX) in patients with CVD.

Methods:

This single-center, prospective pilot study enrolled 30 patients with CVD undergoing CPX. HR was simultaneously recorded using electrocardiography (ECG) and the Fitbit Inspire 3 at 1-min intervals across different CPX phases, including rest, exercise below and above anaerobic threshold (AT), and recovery. The correlation between the two methods was evaluated using Pearson’s correlation coefficient, while measurement error was determined by mean absolute error and mean absolute percentage error (MAPE). A MAPE of ≤10% was set as the cutoff for acceptable agreement.

Results:

The Fitbit Inspire 3 showed a strong overall correlation with ECG-derived HR (r = 0.90) and an acceptable MAPE of 5.40%. The underestimation rate reached 15.97% at above AT compared to 3.33% at rest. When stratified by HF stage (B vs. C), underestimation rates were more pronounced in patients with HF (5.09% vs. 11.27%).

Conclusions:

The Fitbit Inspire 3 demonstrates acceptable validity for HR monitoring during CPX in patients with CVD. Nonetheless, clinicians should exercise caution when interpreting HR data during high-intensity exercise, particularly in patients with HF.