Photoplethysmography (PPG) is a promising technology for continuous monitoring of cardiovascular diseases such as cardiac arrhythmias (CAs). While most research and available PPG devices have focused on the detection of atrial fibrillation (AF), the performance of PPG-based CA detectors is less studied. The aim of the present work is to investigate the performance of PPG beat detectors across various types of CA.
We applied the open-source library (PPG-beats), provided by Charlton and colleagues that evaluates the performance of fifteen PPG beat detectors, to a newly acquired dataset containing various CAs. PPG signals were acquired with a wrist-bracelet concurrently with 12-lead ECG from 54 patients referred for diagnostic or therapeutic electrophysiological procedures at the Lausanne University Hospital. ECG signals were used as the ground truth both for beat timing and annotation of CAs. To compare PPG beat detection performances, F1 score was used as it represents a best trade-off between false positives and false negatives rates.
All beat detectors showed good performances during normal sinus rhythm (F1 score range: 93.6-98.5%). On the contrary, beats from atrial tachycardia (87.0-97.6%), atrial or ventricular bigeminy (70.7-83.2%) and ventricular tachycardia (85.0-92.5%) were more difficult to detect by all detectors, because of their early occurrence within the cardiac cycle and low ejection volume. Out of the fifteen detectors, qppg stands out by obtaining the best F1 score in presence of AF (95.8%), atrial tachycardia (97.6%) and ventricular tachycardia (92.5%) or with a score close to that of the best detector: atrial flutter (95.9%), atrioventricular blocks (96.9%), atrioventricular re-entrant tachycardias (98.8%) and atrial or ventricular bigeminy (82.6%).
Comparing the performances of PPG beat detectors revealed the benefits of using algorithms such as qppg in the presence of CAs. It also highlights the limitations of using PPG for detecting heartbeats during bigeminy, atrial tachycardia and ventricular tachycardia.