Relation between heart rate variability and seizure threshold in electroconvulsive therapy: a pilot study

Objectives: Vegetative dysfunction occurs in a host of medical and psychiatric conditions and is also influenced by their treatment. Heart rate variability (HRV) is an indicator of the heart’s autonomic activity. HRV is also an indicator of treatment outcome in depression. As autonomic activity affects the seizure threshold, it could influence the induction of seizures in electroconvulsive therapy (ECT). This study analyzed the correlation between autonomic nervous system activity measured by HRV and the seizure threshold in the first session of ECT. Methods: All patients treated with ECT at the Odessa Private Psychiatric Institute between December 2013 and May 2015 meeting study entry criteria formed the study sample. Measures calculated from the analysis of ECGs recorded immediately before the first seizure induction was correlated with the seizure threshold. Results: Thirty patients were included in the study. Univariate analysis revealed that only age (p=0.023) and the square root of the mean of the sum of the squares of differences (RMSSD) between all adjacent inter-beat (NN) intervals (p=0.007) had significant positive correlations with the initial stimulus intensity. Conclusion: This is the first report to demonstrate a correlation between the initial stimulus dose of ECT and the RMSSD, a measure of HRV. The RMSSD could be a promising, easily measurable parameter to ascertain initial stimulus intensity in ECT.