Possible impact of stimulus duration on seizure threshold in ECT

Seizure thresholds were measured in patients treated with right unilateral electroconvulsive therapy (ECT) using 0.9 amp, 0.5 ms constant current pulses at 30 Hz for 0.93-2.8 s. Using these parameters, only two patients failed to seize at stimulus charges < or = 75.6 mC. Three patients were excluded from further analysis because they experienced generalized motor or electrographic seizures lasting less than 25 s and 30 s, respectively. The remaining 52 patients had a mean seizure threshold of 48.9 +/- 15.3 mC. Seizure threshold was correlated with age, but not sex. These values for seizure threshold are significantly lower than those reported previously using longer pulse-briefer train duration stimuli, suggesting that characteristics of the electrical stimulus influence seizure threshold. These findings have implications for electrical dosing in right unilateral ECT.