A marked decrease in heart rate variability associated with junctional rhythm during anesthesia with sevoflurane and fentanyl.

Heart rate variability (HRV) was investigated using a new technique for time series analysis combining the maximum entropy method and non-linear least squares method -- the 'MemCalc method' -- in patients undergoing general anesthesia with sevoflurane and fentanyl for elective surgery. As the occurrence of junctional rhythm coincided with the measurement of these variables in two patients, we successfully evaluated the entropy, low (LF) and high (HF) frequency component of the HRV during junctional rhythm and found that the occurrence of junctional rhythm is associated with marked decreases in the entropy, LF and HF of HRV. When evaluating autonomic control of the heart using HRV analysis, the decrease in HRV caused by the occurrence of junctional rhythm must be taken into account.