Spectral EEG effects of electroconvulsive shock stimulus parameters: the development of a rationale for the optimization of the ECT stimulus.

Abstract

Electroconvulsive therapy (ECT) stimulus parameters, such as pulse amplitude, pulse width, pulse frequency, and stimulus duration, differently influence seizure threshold and, possibly, other neurobiological effects of ECT. We examined the influence of these parameters on the EEG power spectrum in an animal model. Adult, male, Wistar rats (n=54) were randomized to receive one of five differently constituted (approximately) 30-mC electroconvulsive shock (ECS) stimuli administered once on alternate days for a total of three ECS. A single-lead, unipolar EEG recording was obtained before, during, and immediately after each ECS seizure. EEG power was computed in eight frequency bands from 2 to 40 Hz. Greater ictal EEG power, greater postictal EEG suppression, and greater interictal EEG power, especially in lower frequency bands, were a priori defined as proxies of seizure efficacy. Motor and EEG seizure duration and a proxy for seizure generalization did not differ significantly across the five stimulus groups. Despite equivalent charge, the five stimuli varied widely in their effects on the EEG proxies of seizure efficacy. The narrow (0.6 milliseconds) pulse width, high (100 Hz) pulse frequency combination was best associated with EEG proxies of seizure efficacy; with this combination, a longer stimulus train duration appeared superior to a greater pulse amplitude. The wide (2 milliseconds) pulse and low (30 Hz) frequency combination was least associated with EEG proxies of efficacy. Stimulus "on" time, number of pulses delivered, and the rate of delivery of charge were not associated with the EEG proxies; the former finding questions the validity of dosing ECT in units of charge. These findings suggest a rationale for optimizing stimulus parameter choices during ECT and provide a framework for the evaluation of electrical aspects of the ECT stimulus.