Detecting atrial fibrillation (AF) from the electrocardiogram and photoplethysmogram (PPG): (a) Photoplethysmogram (PPG) signals during atrial fibrillation (AF, left) and normal sinus rhythm (right); (b) corresponding electrocardiogram (ECG) signals; (c) inter-beat intervals (IBIs); (d) Poincare plots constructed using PPG-derived IBIs.
Source: Data from the Listen Dataset

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Own work
Peterhcharlton