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Physical training modifies the sympathetic-vagal
balance of autonomic nervous system. Previous studies
have shown that such training also produces intrinsic
modifications of cardiac electrophysiological properties
in isolated heart during Ventricular Fibrillation (VF).
Ten NZW trained rabbits were studied to test if the
modifications are related to the activity of
postganglionic parasympathetic neurons. Two records
per subject were acquired during VF: before (G1) and
after (G2) the infusion of atropine to inhibit the activity
of neurons. Mapping records were obtained using a
240-channel electrode array located in the left ventricle
of isolated heart (perfused by Langendorff system). VF
was induced by stimulation at increasing frequencies.
To analyze the time course of fibrillation, the records
were processed in 4-second consecutive segments. For
each channel and segment, the following parameters
were computed: 1) Dominant Frequency (DF), obtained
by the Welch periodogram b) Normalized Energy (NE)
in a frequency band centered at the DF; c) Regularity
Index (RI), which analyzes the similarity of local
activation waves in every segment and channel; d)
Coefficients of Variance of DF (CVDF), NE (CVNE)
and RI (CVRI).
For each segment, we obtained the average value of
each of the parameters analyzed for all electrodes. The
results are: a) DF (G1: 13.671 ± 0.509 Hz, G2: 14.783
± 0.455 Hz), b) NE (G1: 0.398 ± 0.014; G2: 0.380 ±
0.013); c) RI (G1: 0.855 ± 0.017; G2: 0.865 ± 0.015), d)
CVDF (G1: 0.109 ± 0.009; G2: 0.098 ± 0.008), e)
CVNE (G1: 0.398 ± 0.014; G2: 0.380 ± 0.013 ) f) CVRI
(G1: 0.084 ± 0.009; G2: 0.078 ± 0.008).
None of these parameters showed significant
differences between groups. Thus, the parasympathetic
postganglionic neurons seem to have no effect on the
cardiac response in VF due to physical training.
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