Clinical predictors of seizure threshold in electroconvulsive therapy: a prospective study

Abstract

At the start and during the course of electroconvulsive therapy (ECT), estimation of the seizure threshold (ST) is useful in weighing the expected effectiveness against the risks of side effects. Therefore, this study explores clinical factors predicting initial ST (IST) and levels of ST during the ECT course. This prospective observational study included patients aged ≥18 years receiving ECT without contraindications for dose titration. At the first and every sixth consecutive ECT session, ST level was measured. Using multivariate linear regression and multilevel models, predictors for IST and change in ST levels were examined. A total of 91 patients (mean age, 59.1 ± 15.0 years; 37 % male; 97 % diagnosis of depression) were included. In multivariable analysis, higher age (β = 0.24; P = 0.03) and bifrontotemporal (BL) electrode placement (β = 0.42; P < 0.001) were independent predictors for higher IST, explaining 49 % of its variation. Also, these two variables independently predicted higher ST levels at different time points during the course. Using multilevel models, absence of a previous ECT course(s) predicted a steeper rise in ST during the course (P = 0.03 for the interaction term time*previous ECT). The age-adjusted dose-titration method is somewhat crude, resulting in some measurement error. Concomitant medication use could have influenced ST levels. Increasing age and BL electrode placement predicted higher (I)ST, which should be taken into account when selecting ECT dosage. Previous ECT course(s) may avoid an increase in ST during the course of ECT.

Individualized Low-Amplitude Seizure Therapy: Minimizing Current for Electroconvulsive Therapy and Magnetic Seizure Therapy

“…Our analysis did not reveal weight as a significant predictor of ST either. This is largely consistent with clinical ECT data (Boylan et al, 2000;Chung, 2006;van Waarde et al, 2013c), except for a small predictive power of body mass index on BL ECT ST in one study (Chung, 2006).…”

“…The ability of this MT to explain 63.1% of the ST variance in our study is notable as known predictors of conventionally titrated ST for a given electrode placement explain less than 40% of the variance (Boylan et al, 2000;Chung, 2006;Galvez et al, 2015;Sackeim et al, 1994;van Waarde et al, 2013c). The strong correlation between MT and amplitude-titrated ST supports the explanation that the interindividual ST variability is influenced by individual anatomical parameters that also affect the MT.…”

“…This is in contrast to clinical ECT where ST increases with session number (Sackeim, 2004;van Waarde et al, 2013c). The most likely explanation for this difference is that our subjects had been receiving ECT and MST regularly before the initiation of this study and, within the study, the different stimulation modality conditions were scheduled without a significant break in between.…”

“…After accounting for electrode placement, age is the strongest predictor of conventionally titrated ST, although it explains only 10-30% of the ST variance (Boylan et al, 2000;Chung, 2006;Galvez et al, 2015;van Waarde et al, 2013c). Amplitude-titrated ST in unanesthetized patients also increases with age (Liberson, 1948).…”

Differential diagnosis of major depression and bipolar disorder

“…Estimation of the seizure threshold is used in weighing effectiveness against the risk of side effects. In a prospective study, van Waarde et al [16] found higher age and bifrontotemporal electrode placement to be predictors for higher seizure threshold levels at different time points, which should be taken into account when selecting ECT dosage. With respect to treatment of affective disorders, new treatment strategies based on mechanisms of neuroplastic processes should be developed and lead to regeneration of disturbed brain function.…”