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8.6. Visualization

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8.6.1. RR Tachogram #

Graph of RR intervals over time:

  • Blue line: RR intervals
  • Gray points: local minima (respiratory cycles)
  • Green line: signal power (scaled)
  • Gray vertical lines: section markers

8.6.2. RR Tachogram Spectrum #

FFT spectrum of the interpolated RR signal:

  • X-axis: frequency (0–0.5 Hz)
  • Y-axis: spectral amplitude
  • LF (0.04–0.15 Hz) and HF (0.15–0.4 Hz) ranges are marked
  • LF%, HF%, and LF/HF ratio are displayed

8.6.3. Poincaré Plot (Local Return Map) #

Scatter plot of RR(i) versus RR(i-1) or RR(i-shift):

  • Each point: a pair of consecutive RR intervals
  • Colors: different sections
  • Ellipses: 2SD1 and 2SD2 for each section
  1. Shift RR: shift for the Poincaré plot (1–15 intervals)
  2. Checkboxes for including or excluding sections

Physiological explanation of the Poincaré plot:

The Poincaré plot (return map) is a graphical way to visualize heart rate variability by showing the patterns of RR interval changes.

How to read the plot:

  • Each point = a pair of consecutive RR intervals
  • X-axis: RR(i-1), the previous interval
  • Y-axis: RR(i), the current interval
  • If the heart beat like a metronome, all points would be in one place.

Typical shapes:

Round/oval shape (healthy heart):

  • high variability
  • good adaptability
  • healthy ANS state
  • SD1 and SD2 are roughly equal

Elongated shape along the diagonal:

  • low short-term variability (small SD1)
  • long-term trends remain (larger SD2)
  • possible stress or fatigue
  • low SD1/SD2

Compact cloud:

  • low variability overall
  • very regular heartbeat
  • possible health problems
  • both SD1 and SD2 are small

Shifted center:

  • change in mean RR
  • transition between states (rest → load)
  • response to a stimulus

Physiological meaning of SD1 and SD2:

  • SD1 (minor axis):
    • short-term variability
    • beat-to-beat changes
    • predominantly parasympathetic activity
    • associated with respiratory arrhythmia
  • SD2 (major axis):
    • long-term variability
    • trends and slow changes
    • sympathetic + parasympathetic activity
    • associated with the baroreflex and other slow regulatory processes

Clinical significance:

  • Healthy people: round or oval cloud, SD1/SD2 ≈ 0.3–0.5
  • Stress: the cloud becomes elongated, SD1 decreases
  • Aging: the cloud becomes more compact, both SDs decrease
  • Pathology: a very compact cloud or an unusual shape

8.6.4. Segmental HRV Analysis #

The graph shows the dynamics of HRV parameters over time:

  • HR: heart rate
  • FuncGroup: functional group (×10)
  • ExtraPoint: additional score (×100)
  • z(HR): pulse z-score
  • z(SD1): SD1 z-score
  • z(SD2): SD2 z-score
  • RMSSD: RMSSD
  • Relaxation: Relaxation
  • Concentration: Concentration (from EEG)
  • Breath: breathing rate

All parameters are calculated in a sliding window with 75% overlap.

  1. Checkboxes for including or excluding HRV parameters
  2. Average Window: Averaging window for segmental analysis (10–100 intervals)
  3. Save continuously HRV: Save continuous HRV parameters over time