Cross-instrument feasibility, validity, and reproducibility of wireless heart rate monitors: Novel opportunities for extended daily life monitoring

Abstract

Wired ambulatory monitoring of the electrocardiogram (ECG) is an established method used by researchers and clinicians. Recently, a new generation of wireless, compact, and relatively inexpensive heart rate monitors have become available. However, before these monitors can be used in scientific research and clinical practice, their feasibility, validity, and reproducibility characteristics have to be investigated. Therefore, we tested how two wireless heart rate monitors (i.e., the Ithlete photoplethysmography (PPG) finger sensor and the Cortrium C3 ECG monitor perform against an established wired reference method (the VU-AMS ambulatory ECG monitor). Monitors were tested on cross-instrument and test-retest reproducibility in a controlled laboratory setting, while feasibility was evaluated in protocolled ambulatory settings at home. We found that the Cortrium and the Ithlete monitors showed acceptable agreement with the VU-AMS reference in laboratory setting. In ambulatory settings, assessments were feasible with both wireless devices although more valid data were obtained with the Cortrium than with the Ithlete. We conclude that both monitors have their merits under controlled laboratory settings where motion artefacts are minimized and stationarity of the ECG signal is optimized by design. These findings are promising for long-term ambulatory ECG measurements, although more research is needed to test whether the wireless devices' feasibility, validity, and reproducibility characteristics also hold in unprotocolled daily life settings with natural variations in posture and activities.

Keywords: adolescents; cardiovascular; heart rate; heart rate variability.

FIGURE 1

Flowchart of the study. *A precise specification of these various dropout reasons is given in the method section. **The second laboratory session included two more participants than the 49 that finished the second ambulatory week is because although they dropped out of the ambulatory assessment part they agreed to participate in the second laboratory session

FIGURE 2

Visualization of the study design. Upper part: The study involved two laboratory sessions and ambulatory measurements. Lower part: Enlargement of the laboratory sessions. The two blocks labelled “Acc.” indicate 2 min of acclimatization. The other blocks indicate the six laboratory tasks: supine, standing, sitting, paced breathing, a mental stress task, and paced walking

FIGURE 3

Bland‐Altman plots of the Inter‐Beat Interval data collected during the first laboratory session with the Cortrium versus the VU‐AMS device (details on the laboratory session are described in the Method section and depicted in Figure 2). The blue dotted lines represent the mean difference between the Inter‐Beat Interval values, while the red dotted lines represent the limits of agreement from negative 1.96 until positive 1.96 times the standard deviation of the differences. On the x‐axis the Inter‐Beat Interval mean values are given while the y‐axis shows the differences between Inter‐Beat Interval values obtained from the two devices