Electroconvulsive Therapy
Psychiatry · Mood Disorders · lean revision notes
Electroconvulsive Therapy
Electroconvulsive therapy (ECT) is a neuromodulation treatment in which a controlled, generalised tonic-clonic seizure is therapeutically induced under general anaesthesia using a brief electrical stimulus across the scalp. It remains the single most effective treatment in psychiatry for severe, life-threatening mood and psychotic illness, and is a perennial NEET PG favourite because of its counter-intuitive facts (no absolute contraindications, suxamethonium use, modified vs unmodified technique).
Definition and basic concept
ECT delivers a brief electrical current through electrodes placed on the scalp to provoke a bilateral, generalised seizure of adequate duration (≥ 15-25 seconds of motor activity, or adequate EEG ictal activity). The therapeutic effect derives from the seizure itself, not from the electricity per se — hence the goal is always an adequate generalised cerebral seizure, monitored by EEG and the motor (cuff) method.
- Modified ECT — performed under general anaesthesia + a muscle relaxant (suxamethonium) + oxygenation. This is the standard of care today; it abolishes the violent motor convulsion and prevents fractures.
- Unmodified ECT — without anaesthesia/relaxant; now considered substandard/unethical in most settings because of fracture and aspiration risk. (Still asked in exams as a contrast.)
High-yield: The therapeutic agent in ECT is the generalised seizure, not the current. A failed/abortive (focal or short) seizure is therapeutically inadequate.
Indications
ECT is indicated when illness is severe, refractory, or life-threatening, or when a rapid response is required.
| Indication | Why ECT / notes |
|---|---|
| Severe major depressive disorder with suicidality | Fastest, most effective antidepressant; first-line when suicide risk is acute |
| Depression with refusal to eat/drink, severe psychomotor retardation, stupor | Need rapid response; saves life |
| Psychotic (delusional) depression | Responds better to ECT than to antidepressant alone |
| Catatonia (any cause) | Highly effective; second-line after a lorazepam challenge |
| Mania — severe, drug-resistant, or with exhaustion | Effective, rapidly controls |
| Schizophrenia — catatonic subtype, severe agitation, drug resistance | Adjunct, not first-line for chronic disease |
| Neuroleptic malignant syndrome (NMS) | ECT is an effective treatment when supportive care/dantrolene/bromocriptine fail |
| Post-partum psychosis / depression | Useful when rapid recovery needed and to limit drug exposure during breastfeeding |
| Pregnancy with severe mental illness | Considered relatively safe in all trimesters |
High-yield: The number-one and most-tested indication is severe major depression with active suicidal intent (when a rapid response is needed). Catatonia and NMS are the favourite "non-mood" indications.
Mnemonic for prime indications — "SMC": Severe depression with Suicidality, Mania (resistant) / Melancholia, Catatonia.
Contraindications
This is the single most tested ECT concept.
High-yield: There is NO absolute contraindication to ECT. All contraindications are relative — risk/benefit must be weighed. NEET PG repeatedly tests this exact statement.
Relative contraindications (situations of raised risk, chiefly because of the transient rise in intracranial pressure, blood pressure and cardiac workload during the seizure):
| Relative contraindication | Mechanism of concern |
|---|---|
| Space-occupying intracranial lesion / raised ICP | Seizure-induced surge in cerebral blood flow & ICP → herniation risk (classically the highest-risk relative CI) |
| Recent myocardial infarction (< 3 months) | Surge in HR/BP & catecholamines stresses myocardium |
| Recent stroke / cerebral haemorrhage | Risk of rebleed with BP surge |
| Unstable / severe cardiac disease, arrhythmia, decompensated CCF | Haemodynamic stress |
| Cerebral aneurysm / vascular malformation | Rupture with BP surge |
| Retinal detachment, phaeochromocytoma | Pressure / catecholamine surge |
| Severe osteoporosis, recent fracture, unstable spine | Fracture risk (mitigated by muscle relaxant) |
| Severe respiratory disease | Anaesthetic risk |
High-yield: A space-occupying lesion with raised ICP is the condition most often labelled the "highest-risk" relative contraindication — but it is still NOT absolute.
Physiology and mechanism of action
The mechanism is multifactorial and incompletely understood, but examinable strands include:
- Neurotransmitter / receptor changes — ECT enhances post-synaptic responses to serotonin (5-HT), downregulates β-adrenergic receptors (similar to antidepressants), and modulates dopamine and GABA. It increases dopaminergic transmission (explains anti-parkinsonian benefit and use in NMS/Parkinson disease).
- Neuroendocrine release — transient surge in prolactin, ACTH, cortisol, oxytocin (prolactin rise post-seizure can confirm a true generalised seizure).
- Neurotrophic / neuroplasticity hypothesis — increased BDNF, hippocampal neurogenesis and synaptogenesis.
- Anticonvulsant hypothesis — seizure threshold rises across a course of ECT and seizure duration shortens; this rise in threshold correlates with therapeutic response.
Seizure threshold — the minimum charge needed to induce an adequate seizure. Important facts:
- Threshold is higher in men, the elderly, and with bilateral placement.
- Threshold rises progressively during a course of ECT → may need to increase dose ("dose titration").
- Anticonvulsants, benzodiazepines and lignocaine raise threshold (reduce efficacy); drugs like theophylline, caffeine, and flumazenil lower it (and theophylline risks status epilepticus).
High-yield: Seizure threshold is highest in elderly males with bilateral electrodes, and it increases over the course (so stimulus dose may need up-titration).
Stimulus waveform: brief pulse vs sine wave
| Feature | Brief-pulse (modern) | Sine wave (old) |
|---|---|---|
| Waveform | Brief square pulses | Continuous sinusoidal |
| Electrical energy delivered | Much lower | High (lots of "wasted" current) |
| Efficiency at producing seizure | High (efficient depolarisation) | Low |
| Cognitive side effects / memory loss | Less | More |
| Current standard | Preferred | Obsolete |
Ultra-brief pulse (≤ 0.3 ms) further reduces cognitive impairment, especially with right unilateral placement, but may need more sessions.
High-yield: Brief-pulse stimulus is preferred over sine wave — it produces a seizure with less electrical energy and fewer cognitive/memory side effects.
Electrode placement: bilateral vs unilateral
| Feature | Bilateral (bitemporal) | Right unilateral (RUL, d'Elia) |
|---|---|---|
| Efficacy / speed | Most effective, fastest response | Slightly slower, needs higher dose (≥ 5-6× threshold) |
| Cognitive side effects | More memory impairment | Fewer cognitive/memory effects |
| When preferred | Need rapid response (suicidal, catatonia, NMS); failed unilateral | When minimising memory loss is priority |
- Right unilateral (d'Elia placement): one electrode over the right temple, the other on the right parietal area (vertex). Spares the dominant (left) hemisphere → less verbal memory loss.
- Bifrontal placement is a third option, balancing efficacy with somewhat fewer cognitive effects.
High-yield: Eponym to remember — d'Elia placement = right unilateral ECT. Bilateral is more effective but causes more memory loss.
Anaesthesia and drugs used during ECT
A clean, examinable sequence. Pre-oxygenation → anticholinergic → induction (anaesthetic) → muscle relaxant → bite block → deliver stimulus → ventilate → recovery.
| Drug class | Agent(s) | Role / pearl |
|---|---|---|
| Anticholinergic | Atropine / glycopyrrolate | Reduces secretions, prevents vagal bradycardia/asystole from the stimulus |
| Induction anaesthetic | Methohexitone (classic), thiopentone, propofol, etomidate, ketamine | Methohexitone is the traditional agent of choice (least effect on seizure threshold); propofol shortens seizure; etomidate/ketamine prolong it |
| Muscle relaxant | Suxamethonium (succinylcholine) | Depolarising, ultra-short-acting relaxant of choice — prevents the violent muscle contraction and fractures |
| Bite block | — | Protects teeth/tongue (one of the few muscle groups deliberately not fully relaxed so a small motor seizure can be observed) |
High-yield (very frequently asked): The muscle relaxant used during modified ECT is suxamethonium (succinylcholine) — chosen for its short, rapid action. The classic induction agent is methohexitone.
Pearls:
- Suxamethonium is avoided where there is a pseudocholinesterase deficiency (prolonged apnoea) or hyperkalaemia risk.
- Atropine before ECT prevents bradyarrhythmia/asystole during the brief parasympathetic phase that immediately follows the stimulus.
- Hyperventilation with oxygen lowers seizure threshold and prolongs seizure → used to optimise an inadequate seizure.
Autonomic sequence during a seizure: an initial brief parasympathetic surge (bradycardia, even transient asystole) is followed by a dominant sympathetic surge (tachycardia, hypertension).
Technique, course and frequency
- Work-up: history, exam, cardiac assessment, fasting status; informed consent. Routine "ECT battery" investigations are not mandatory in a healthy young patient but are individualised.
- NPO for ~6 hours; remove dentures; secure IV access; monitor ECG, SpO₂, BP, EEG.
- Pre-oxygenate, give anticholinergic, induce anaesthesia, give suxamethonium, insert bite block.
- Deliver brief-pulse stimulus; confirm an adequate seizure by EEG and the cuff (Hamilton) method — a BP cuff inflated above systolic on one limb before the relaxant lets you watch the motor seizure in that "isolated" limb.
- Ventilate until spontaneous breathing returns; recover and monitor.
- Frequency: typically 2-3 times per week (alternate days). India commonly uses thrice weekly.
- Course: usually 6-12 sessions for depression; continue to remission, not a fixed number.
- Continuation/maintenance ECT — periodic ECT (e.g., weekly→monthly) to prevent relapse in highly recurrent illness.
- Adequate seizure duration: roughly 15-25 s of motor activity (or 25-50 s of EEG ictal activity); < 15 s is usually inadequate, while a prolonged seizure (> 120-180 s) should be terminated with IV benzodiazepine.
High-yield: Standard schedule is 2-3 sessions/week, total ~6-12 sessions, continued to clinical remission rather than a preset count. Adequate motor seizure ≈ 15-25 seconds.
Side effects and complications
| Category | Effects |
|---|---|
| Cognitive (most important) | Anterograde amnesia (new learning) and retrograde amnesia (memories around treatment); transient post-ictal confusion. Memory typically recovers over weeks; some patchy retrograde gaps may persist. |
| Immediate / per-procedure | Headache, myalgia, nausea, jaw pain, transient confusion |
| Cardiovascular | Transient arrhythmia, bradycardia→tachycardia, BP surge; rare MI/arrhythmia in cardiac patients |
| Respiratory / anaesthetic | Aspiration, prolonged apnoea (suxamethonium + pseudocholinesterase deficiency) |
| Musculoskeletal | Fractures, dislocations (only in unmodified ECT — prevented by relaxant) |
| Other | Prolonged seizure/status, emergent mania ("manic switch"), dental/tongue injury |
Memory pearls:
- Cognitive side effects are reduced by: brief/ultra-brief pulse, right unilateral placement, lower stimulus dose, twice-weekly (vs thrice) scheduling, adequate oxygenation.
- Mortality of ECT is very low — comparable to that of brief general anaesthesia (≈ 1 in 50,000–80,000 treatments), and deaths are usually cardiac.
High-yield: The major, most-tested adverse effect is memory impairment (amnesia), which is minimised by right unilateral electrode placement + brief-pulse stimulus. ECT does not cause permanent structural brain damage.
ECT and special situations
- Pregnancy: ECT is considered relatively safe in all three trimesters and is often preferred over teratogenic/risky psychotropics in severe illness; precautions include left lateral tilt, fetal monitoring, and avoiding hyperventilation-induced hypocapnia.
- Elderly: Often more responsive (e.g., psychotic depression) but higher seizure threshold and more cognitive effects → unilateral, careful dosing.
- Parkinson disease: ECT can transiently improve motor symptoms (dopaminergic effect) and treat coexisting depression.
- Epilepsy: Not a contraindication; ECT actually raises seizure threshold (anticonvulsant effect).
- Drug interactions: Lithium + ECT → risk of prolonged delirium/confusion and prolonged neuromuscular blockade → usually withheld/reduced before ECT. Benzodiazepines and anticonvulsants raise threshold and reduce efficacy → taper if possible. Theophylline risks status epilepticus.
High-yield: Lithium should be withheld/reduced before ECT (risk of delirium and prolonged apnoea). Benzodiazepines and anticonvulsants reduce ECT efficacy by raising seizure threshold.
Key differentials and "what to choose instead"
Exam stems often pit ECT against other neuromodulation/somatic treatments:
| Modality | Seizure induced? | Anaesthesia? | Niche vs ECT |
|---|---|---|---|
| ECT | Yes (therapeutic) | Yes | Most effective for severe/refractory mood & catatonia |
| rTMS (repetitive transcranial magnetic stimulation) | No | No | Outpatient, fewer cognitive effects, milder depression / less urgent |
| VNS (vagus nerve stimulation) | No | Implant surgery | Chronic treatment-resistant depression, slow onset |
| DBS (deep brain stimulation) | No | Neurosurgery | Experimental for refractory OCD/depression |
| Magnetic seizure therapy (MST) | Yes (focal) | Yes | Fewer cognitive effects than ECT; investigational |
- Catatonia algorithm: Lorazepam challenge first → ECT if no response (or if malignant catatonia/NMS, move to ECT early).
- NMS: stop the offending neuroleptic, supportive care, dantrolene/bromocriptine → ECT if refractory.
Recently asked / exam angle
NEET PG, INI-CET and FMGE have repeatedly tested:
- "Which is an absolute contraindication to ECT?" → trick: none / there is no absolute contraindication. (raised ICP / SOL is only relative.)
- Muscle relaxant used in ECT → suxamethonium (succinylcholine).
- Anaesthetic agent of choice / classic induction agent → methohexitone.
- Drug given to prevent bradycardia/secretions → atropine (anticholinergic).
- Most effective treatment for severe depression with suicidal ideation → ECT.
- Electrode placement with the least memory impairment → right unilateral (d'Elia).
- Waveform causing fewer cognitive effects → brief pulse.
- Most common / most important side effect → memory impairment (amnesia).
- What confirms an adequate effect / true seizure → adequate EEG ictal activity + cuff method motor seizure (15-25 s); prolactin surge.
- ECT in pregnancy → considered safe.
- Indication other than depression → catatonia, NMS, severe drug-resistant mania.
- Seizure threshold across a course → increases.
Rapid revision
- No absolute contraindication to ECT — all are relative; raised-ICP/SOL is the highest-risk relative CI.
- The therapeutic agent is the generalised seizure, not the current itself.
- Suxamethonium (succinylcholine) = muscle relaxant of choice (short-acting, depolarising).
- Methohexitone = classic induction anaesthetic; atropine/glycopyrrolate prevents bradycardia and secretions.
- Brief-pulse waveform > sine wave: less energy, fewer cognitive effects.
- Right unilateral (d'Elia) = least memory impairment; bilateral = most effective/fastest.
- #1 indication: severe MDD with suicidality needing rapid response; also catatonia, mania, NMS.
- Major side effect: memory impairment (anterograde + retrograde amnesia) — usually reversible; no permanent brain damage.
- Seizure threshold rises over a course and is highest in elderly males with bilateral placement.
- Schedule: 2-3×/week, ~6-12 sessions, to remission; adequate motor seizure ≈ 15-25 s.
- ECT is safe in pregnancy (all trimesters); withhold lithium beforehand (delirium/prolonged apnoea).
- Autonomic response: brief parasympathetic (bradycardia) then dominant sympathetic (tachycardia/hypertension) surge.