The objective of this work is to study the modifications
on cardiac response during ventricular fibrillation (VF)
induced by physical training. The analysis was performed
in the frequency domain of VF, and the regularity of the
signal was also considered.
Two sets of records were acquired: control (G1:
without physical training, N=10), and trained (G2, N=9).
Cardiac registers were obtained using a 240-electrodes
matrix located on left ventricle of isolated rabbit heart. A
Langendorff system was used to maintain the heart
perfusion. VF was induced by increased frequencies.
To analyze the time course of VF, records were
processed in 4-second segments. For every segment and
channel, Welch periodogram with Hanning window, two
non-overlapped sections and zero padding, was
computed. Parameters considered in frequency domain
are: dominant frequency (DF) and normalized energy
(NE: spectral energy in the window DF±1Hz, normalized
by spectral energy in 5-35Hz band).
For every segment and channel, a regularity analysis
of VF was performed, obtaining the regularity index (RI),
which is a measure of similarity among local activation
waves present in every channel.
Mean values for the parameters (DF, NE and RI) of
the whole set of electrodes were computed for every
segment. Obtained results show that DF is lower for
trained rabbits (G1: 18.234±1, 241Hz; G2: 14.370±0,
866Hz; p<0.001). NE is greater for this group (G1:
0.140±0.006; G2: 0.263±0.017; p<0.001), suggesting a
greater spectral concentration around DF. Finally, a
greater regularity has been observed in the fibrillation
signal for trained group (IR, G1: 0.756±0.026; G2:
0.834±0.014; p<0.001).
As a summary, the results suggest that both spectral
characteristics and regularity of VF signal are clearly
different for G1 and G2 groups. The trained group (G2)
shows greater regularity, lower DF and spectral
dispersion. These factors should be interpreted as a more
stable cardiac response to V
