ECT and seizure threshold: effects of stimulus wave form and electrode placement

The effects of stimulus parameters and electrode placement upon ECT seizure threshold were investigated in 40 psychiatric inpatients referred for ECT treatment, using EEG monitoring of seizure activity. Overall, brief pulse stimuli were found to require approximately one-third as much stimulus energy as sine wave stimuli in producing equivalent suprathreshold seizures. For brief pulse stimuli, unilateral nondominant electrode placement, utilizing a parieto-frontotemporal arrangement, was associated with a slightly lower seizure threshold than for bilateral electrode placement. For sine wave stimuli, on the other hand, no difference in seizure threshold on the basis of electrode placement was found, although unilateral electrode placement as associated with briefer seizures. The implications of these findings in terms of clinical efficacy and CNS side effects are discussed.