Hypnotizability-related complexity of heart rate variability during long lasting relaxation

Aim of the experiment was to compare heart rate and HRV of healthy subjects with high (Highs) and low (Lows) susceptibility to hypnosis during long-lasting relaxation. HRV indexes extracted in the frequency and time domain as well as related to the complexity of the tachogram (entropy) were analyzed through repeated measures ANOVA. The results indicated a parasympathetic prevalence in Highs all over the session and a sympathetic modulation across the session in both groups reflected in the sd2 dimension of the Poincaré plot and in entropy. The possible role of the Very Low Frequency spectral component in these changes, supported by the different correlations between entropy and frequency/time related indexes of HRV, is suggested.