Mechanism of Action and Indications for Electroconvulsive Therapy
Mechanism of Action
ECT works by inducing a generalized seizure through electrical stimulation of the brain under general anesthesia, though the precise mechanisms remain incompletely understood. 1, 2
The proposed mechanisms include:
Neuroplastic changes: ECT increases gray matter volume in the hippocampus-amygdala complex, which correlates with clinical improvement 3. Patients with high connectivity between the subgenual anterior cingulate and middle temporal gyrus before ECT show better treatment response 3.
Neurotransmitter modulation: Animal models demonstrate ECT affects multiple neurotransmitter systems including glutamate, GABA, serotonin, and dopamine, though human evidence remains limited 3.
Anticonvulsive effects: The therapeutic benefit may paradoxically relate to anticonvulsive properties that develop after repeated seizure induction 1.
Immunomodulatory properties: ECT exerts potent effects on immune function that may contribute to its antidepressant efficacy 1.
The lack of complete convergence between these neurobiological changes and ECT's robust clinical effects likely reflects small sample sizes and methodological differences across studies 1.
Primary Indications
The primary indication for ECT is severe, persistent major depression (with or without psychotic features), where it achieves 70-80% response rates and 50-60% remission rates even in treatment-resistant patients. 4, 1
Mood Disorders
- Severe major depression with treatment resistance (failure of at least two adequate medication trials) 4
- Mania (with or without psychotic features) 4
- Schizoaffective disorder 4
- Bipolar depression 2
Psychotic Disorders
- Schizophrenia, particularly with prominent affective symptoms or during acute exacerbations of positive symptoms 5, 4, 6
- Clozapine-resistant schizophrenia 2
Emergency Psychiatric Conditions
- Catatonia (regardless of underlying diagnosis) - this is a particularly strong indication 4, 2
- Neuroleptic malignant syndrome 4
Life-Threatening Presentations
ECT should be considered urgently when patients present with:
- Refusal to eat or drink 4
- Severe suicidality (ECT reduces suicide risk by 50% in the first year post-discharge) 7
- Uncontrollable mania 4
- Florid psychosis 4
Required Criteria Before ECT
Treatment resistance is mandatory unless waiting endangers life or the patient cannot tolerate medications. 4
The criteria include:
- Appropriate diagnosis: One of the primary indications listed above (not anxiety disorder alone) 4
- Severe, life-threatening symptoms: As detailed above 4
- Treatment resistance: Defined as failure of at least two adequate medication trials, unless the patient cannot tolerate medications or waiting endangers life 4
Important Clinical Considerations
Comorbidities Are Not Contraindications
- Personality disorders do not contraindicate ECT, though they may affect treatment response 5, 7
- Anxiety disorders comorbid with severe mood disorders should not prevent ECT use 4
- Mental retardation is not a contraindication 5
- Seizure disorders do not preclude ECT and may even improve with treatment 5
- Neurological conditions (including history of craniotomy, intracranial tumors, or cerebral lesions) require careful assessment but are not absolute contraindications 5, 7
Optimizing Treatment Parameters
Right unilateral (RUL) electrode placement is as effective as bilateral ECT for major depression and causes fewer cognitive side effects. 8, 3, 9
- Use brief pulse stimulation rather than sine wave to reduce cognitive impact 8
- Employ the lowest effective electrical dose moderately above seizure threshold 8
- Administer treatments 2-3 times weekly 7
- A typical course consists of 10-12 treatments, with initial improvement after 5-6 treatments 7
- For severe agitation or psychotic features, bilateral placement may be preferred initially for more rapid response 7
Medication Management During ECT
- Discontinue: Lithium, benzodiazepines, and carbamazepine due to adverse effect risks 7
- May continue: Olanzapine, mirtazapine, and vortioxetine as part of maintenance strategy 7
Common Side Effects and Management
- Cognitive effects: Memory impairment may persist for approximately 2 months post-treatment 8
- Acute side effects: Headache (treat with acetaminophen), nausea, vomiting, muscle aches, confusion, and agitation typically resolve within the day of treatment 5, 8
- Prolonged seizures: Occur in 0-10% of treatments; treat promptly with additional methohexital, diazepam, or lorazepam 5, 8
Post-ECT Management
ECT resolves acute illness but does not prevent relapse, requiring continuation treatment. 5
- Implement pharmacotherapy tailored to the presenting disorder (antidepressants for unipolar depression, mood stabilizers for bipolar illness) 5
- Consider maintenance ECT in adults, though data in adolescents are insufficient 5
- Monitor for mood changes and suicidal ideation for several weeks post-treatment 5
- Use standardized rating scales to systematically assess treatment outcomes and adverse effects 5, 8