Abstracts

Rationale: Dynamic heart rate (HR) changes have been repeatedly described in previous studies on electroconvulsive therapy (ECT). However, the specific timing of these changes remains unclear. To elucidate the cardiac autonomic nervous system changes during an epileptic seizure, we examined HR and spectral analysis of heart rate variability (HRV) during ECT.Methods: Fifteen patients with depression and ten patients with schizophrenia who underwent ECT were recruited. A total of 206 ECT sessions were assessed using electrocardiograms (ECG). HR was recorded and analyzed for the HRV indices HF (an index of parasympathetic activity) and LF/HF (an index of sympathetic activity) during 4 minutes before and after stimulus onset. Visual inspection of HR waveforms, and HF and LF/HF power suggested that HRs were reduced in the initial 0 30 seconds and that LF/HF power was larger compared with HF power at 30 100 seconds. In addition, HF power increased and became larger compared with LF/HF power after 100 seconds. Thus, we defined three epochs as follows: 0 30 seconds, first phase; 30 100 seconds, second phase; and 100 170 seconds, third phase after stimulus onset. For the first phase, averaged HRs over three HRs (RR intervals) were compared between pre-seizure and post-seizure. For the second and third phases, HF and LF/HF power were assessed.Results: There was a significant prolongation of the average HR over three HRs just after stimulus onset, suggesting parasympathetic dominance in the first phase. The LF/HF power significantly increased in the 30 100 seconds after stimulus onset, while the average power of HF significantly increased in the 100 170 seconds after stimulus onset, reflecting sympathetic activation in the second phase and parasympathetic activation in the third phase. Conclusions: The evaluation of HRs and HRV revealed a triphasic change from parasympathetic to sympathetic to parasympathetic cardiac autonomic activity following stimulus onset. This may be a useful model for studying cardiac autonomic nervous activity changes during seizures in epilepsy.