Figure 3.

A comparison of cardiovascular signals in wearable devices. The electrocardiogram (ECG) waveform is shown relative to the volumetric waveform obtained via photoplethysmography (PPG). Of note, the volumetric changes that are demonstrated in the PPG waveform captured at a distal anatomical location travel slower than the electrical impulses that are captured by ECG, resulting in a slight delay of features, though highly proportional to that of ECG.