Correlation between time domain baroreflex sensitivity and Sympathetic Nerve Activity

Autonomic nervous system (ANS) dysfunction is evidenced by reduced baroreflex sensitivity (BRS), which can be quantified as the slope between SBP and RR values in baroreflex events (BEs). BEs can be either of short or of long length, so they are likely to be associated with fast/parasympathetic as well as with slow/sympathetic ANS modulations. Under sympathetic inhibition, LF power in Muscle Sympathetic Nerve Activity (MSNA) decreases and HF power dominates. Therefore, it is suggested that LF and HF powers of MSNA are related with sympathetic neural excitation and inhibition, respectively. In this work, MSNA powers are associated with BRS from short/long BEs, defined from a cutoff length estimated from the respiratory frequency of each subject. The results indicate that BRS from short(long) BEs are correlated with HF(LF), while not significantly correlated with LF(HF) powers. Therefore, short and long BEs may carry different information on ANS modulations in baroreflex regulation.