The acute effect of bitemporal electroconvulsive therapy on synchronous changes in heart rate variability and heart rate in patients with depression.

The transient autonomic nervous system responses induced by electroconvulsive therapy (ECT) may serve as critical indicators of treatment efficacy and potential side effects; however, their precise characteristics remains unclear. Considering that the intense stimulation of ECT may disrupt the typical antagonistic relationship between the sympathetic and parasympathetic branches, this study aims to conduct a meticulous analysis of the rapid changes in heart rate variability and heart rate during ECT, with a particular focus on their synchronized interplay. Methods: Pulse interval sequences were collected from fifty sessions of bitemporal ECT administered to twenty-seven patients diagnosed with major depressive disorder. The average heart rate (HR) and ultra-short term (UST) heart rate variability (HRV) indices RMSSD and SDNN, as well as the Poincaré indices SD1, SD2 and SD2/SD1, were calculated using a 10-second sliding window with a step size of 1 second. In particular, the synchronous changes between SD1, SD2, SD2/SD1 and HR were analyzed. Results: The synchronous changes of the indices showed different characteristics over time. In particular, SD1, SD2 and HR increased significantly by 41.50±11.45 ms, 33.97±10.98 ms and 9.68±2.00 bpm respectively between 8 and 20 seconds, whereas they decreased significantly by 19.89±9.07 ms, 17.54±8.54 ms and 3.80±1.33 bpm respectively between 45 and 53 seconds after ECT stimulus onset. SD1, SD2 and SD2/SD1 all had highly significant positive correlations with HR in the above phases. Conclusion: The results suggest that bitemporal ECT induces the sympathetic and parasympathetic co-activation during the early ictal period and brief co-inhibition approximately 45 seconds after stimulus. Our findings may provide new insights comprehending the mechanisms of ECT and its associated cardiovascular risks. .