Clinical Validation of Heart Rate Apps: Mixed-Methods Evaluation Study

Figure 1. Visualized relation between electrocardiography (ECG), arterial blood pressure (ABP), and photoplethysmography (PPG).

Figure 2. Photoplethysmography (PPG) principle by smartphone.

Figure 3. Beat-to-beat analysis from R-R intervals (RRI) and peak-to-peak intervals (PPI).

Figure 4. Graphical representation of how measurements are performed using the different devices. Left, FibriCheck application; Middle, Nonin oximeter; Right, AliveCor.

Figure 5. Graphical overview measurement-process study 1.

Figure 6. Measurement setup for simultaneous photoplethysmography (PPG) and electrocardiography (ECG) recording. A wearable ECG sensor to measure 1-lead ECG data; B, FibriCheck app to measure PPG data.

Figure 7. Synchronization of electrocardiography (ECG) and photoplethysmography (PPG) signal.

Figure 8. Bland-Altman plots for each device pair. The mean difference (bias), 1.96 (lower limit of agreement, LLA) and +1.96 standard deviations (upper limit of agreement, ULA) are plotted as full lines.

Figure 9. Bland-Altman plot comparing the reference R-R intervals (electrocardiography [ECG]) to the peak-to-peak intervals (photoplethysmography, PPG).

Figure 10. Overview heart rates divided in resting and high heart rates.

Figure 11. Correlation of intervals for both techniques (ie, electrocardiography [ECG] and photoplethysmography [PPG]) in milliseconds. Gray, high heart rates; Black, low heart rates.

Figure 12. Overview of beat-to-beat intervals divided in irregular and regular beats.