Preliminary study for localizing c, d and e waves in photoplethysmogram signals.

An efficient and robust method based on two moving-average filters followed by a dynamic event-duration threshold was developed to locate c, d and e waves in the acceleration photoplethysmogram (APG) signals. This investigation was the first of its kind to locate c, d and e waves in subjects measured at rest and after exercise. The method detects c, d and e in arrhythmia APG signals that suffer from: 1) non-stationary effects and 2) low signal-to-noise ratios. The performance of the proposed method was tested on 27 records collected in normal and heat-stressed conditions, resulting in a 99.95% sensitivity and 98.35% positive predictivity.