Detection and Analysis of Heartbeats in Seismocardiogram Signals

. 2020 Mar 17;20(6):1670. doi: 10.3390/s20061670

Algorithm 1 Detection of heartbeat events.

Inputs:

Begin:

Compute $x_{D E T}$ and $x_{S Q R}$ according to Equations (2) and (3), respectively
Calibration:
- 1.
  Find positive $x_{S Q R}$ periods such that:
  - (a)
    are separated by 400 ms up to 1500 ms
  - (b)
    relative variation in separation is not greater than $\pm 30 %$
- 2.
  Find $x_{D E T}$ maxima around periods found at point 1
- 3.
  Compute $τ_{S}$ from Equation (4)
- 4.
  Incrementally align sample beats:
  - (a)
    align waveforms around time instants found at point 2
  - (b)
    refine alignment by performing cross-correlation of $x_{S C G}$ within $\pm τ_{S}$ of the time instants found above at point 4a
- 5.
  Extract SCG beat template (median)
Annotation:
- 6.
  Perform steps 1–3
- 7.
  Perform steps 4a–4b by aligning the template and the current $x_{S C G}$ , $x_{D E T}$ waveforms
- 8.
  Mark the maximal alignment point as heartbeat location

Return time instants of heartbeats