Effect of ECT Stimulus Parameters on Seizure Physiology and Outcome

Abstract

This study examined the effect of low- and high-pulse frequency stimulus electroconvulsive therapy on seizure physiology and therapeutic outcome. Forty depressed patients randomly received either low (n = 19) or high (n = 21) pulse frequency stimulus during a course of right unilateral electroconvulsive therapy. The current and pulse width were kept constant whereas the duration was proportionately varied. The two groups were compared for seizure parameters and therapeutic outcome. Low frequency stimulus group had lower threshold and less subconvulsive stimulation. There were no differences in seizure durations, ictal cardiovascular responses and therapeutic outcome between the two groups. Low frequency stimulus produced seizure at lower stimulus dose without affecting seizure parameters and therapeutic effects.

Exceptionally High Initial Seizure Threshold in a Catatonic Patient Treated With Electroconvulsive Therapy

“…26 On the other hand, female patients generally have a lower seizure threshold than males, 27 and the stimulus parameters used in our patient (ie, long stimulus duration and short pulse width) may have contributed to lowering her seizure threshold. 18 Etomidate has been recommended as the first-line anesthetic for patients with very high seizure thresholds. 15 Because we routinely administer etomidate, lowering the seizure threshold by switching to another anesthetic was not an option with our patient.…”

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“…After the seizure, blood flow and glucose metabolism decrease, most markedly in the frontal lobes, and this decrease appears to correlate strongly with the therapeutic outcome of ECT. Therefore, the effects on frontal lobe function, an area strongly implicated in the pathophysiology of depressive illness, may be relevant in the mechanism of action of ECT (5,4,6).…”

“…Virtually every neurotransmitter system is affected by ECT, but consistent findings include downregulation and desensitization of postsynaptic beta-adrenergic receptors and upregulation of postsynaptic serotonin receptors, a change similar to that observed with virtually all antidepressant treatments ECT also decreases serotonin turnover and acetylcholine levels in the brain and CSF and also may result in reduction in dopamine levels. Regarding second-messenger systems, ECT affects the coupling of G proteins to their receptors, the activity of adenylyl cyclase and phospholipase C, and the regulation of calcium entry into neurons (7,8,4).…”

“…Bilateral ECT may be indicated initially in patients with severe symptoms or those who pose an immediate danger to themselves or others. Examples of such situations include catatonic stupor, marked agitation, acute suicide risk, severe depressive or manic symptoms, and treatment-resistant schizophrenia (5,15,8,4).…”

“…In addition, a course of ECT treatments often increases a patient's seizure threshold by 25-200%. Adding to the confusion of inter-and intrapatient differences in seizure threshold, a difference in genders, with men having a higher threshold, and age, in which the elderly require a greater stimulus, has been established (3,8,4).…”