A naturalistic study of the measurement of seizure adequacy in electroconvulsive therapy

The aim of this study was to assess an electroconvulsive therapy (ECT) rating scale by studying the intraictal electroencephalograph parameters induced by the seizure, and determine the clinical utility of such a scale in terms of time, application and ease of use.

This naturalistic study of 55 depressed patients over a 2-year period examined specific parameters of the intraictal electroencephalograph seizure morphology and computer printout, and their association with overall clinical outcome. The rating scale was developed and evaluated in terms of clinical reliability and ease of use.

Overall, 1076 individual ECT treatments were given. Using multiple regression analysis, overall seizure adequacy correlated most closely with abrupt seizure endpoint, a high amplitude rhythmic spike and wave phase of >13 s, a seizure energy index of >1000 u, and an electroencephalograph seizure length of > 24 s. "Adequate" overall ratings as determined by the rating scale were shown to correlate significantly with overall clinical improvement. The rating scale had extremely high interrater and test-retest reliability; and was relatively easy to use and time efficient.

The use of the rating scale has the potential to help clinicians optimize ECT. While not perfect in any sense, it still gives clinicians good predictive qualities when used as a clinical guide. It is important that larger studies look at all the potential variables that may interact with seizure adequacy and clinical outcome.