Effect of electrical parameters on ECT convulsive threshold and duration

Optimal stimulus parameters for electroconvulsive therapy (ECT) are unclear. Pulse duration and frequency related to convulsive threshold and seizure duration in the first ECT treatment in a series were evaluated.

Convulsive threshold was estimated for all patients (N = 550) receiving ECT over 27 months. Thresholds were estimated using different brief pulse stimulators, starting with a dose of approximately 25 mC per pulse train for right unilateral (RUL) stimulation (50 mC for bilateral [BL] stimulation). The charge was applied in 25-mC serial increments (approximately doubling for BL stimulation) up to approximately 100 mC (>200 mC for BL stimulation) to a generalized motor seizure endpoint. Patients lacking seizure response at 100 mC (200 mC for BL stimulation) received >500 mC.

Convulsive threshold increased with age, African American identity, diagnosis other than depression, and female sex, and decreased with RUL electrode placement, low frequency (30 Hz), and brief pulse width (0.5 msec). RUL stimulation and lower anesthetic medication doses promoted longer seizures. Younger patients had longer seizures than older patients. Pulse width and frequency did not affect seizure duration. Lower charge yielded longer seizures.

ECT efficiency appears to be achieved by lower frequency and briefer pulse duration stimulation. Randomized trials are needed for corroboration of these findings.