Electrical Storm
Definition
Electrical storm (ES) is defined as ventricular arrhythmia (VA) that occurs 3 or more times within 24 hours (each episode separated by at least 5 minutes), with each episode requiring termination by an intervention (ICD shock, overdrive pacing, or external cardioversion). It is a life-threatening condition associated with high in-hospital mortality and poor long-term prognosis.
- AHA 2017 definition (VA/SCD guideline): VT/VF storm (electrical storm or arrhythmic storm) = a state of cardiac electrical instability defined by ≥3 episodes of sustained VT, VF, or appropriate shocks from an ICD within 24 hours. (No minimum inter-episode separation specified in the AHA definition, in contrast to the ESC ≥5 minutes separation requirement.) (sources/va-scd-aha-2017, rating: very high)
Key concepts
- Incessant VT: a related but distinct entity — continuous sustained VT that recurs promptly despite repeated intervention over several hours. (sources/VA-SCD-ESC-2022)
- ES is most commonly associated with underlying structural heart disease (especially ischaemic cardiomyopathy) and occurs most often in ICD recipients. (sources/VA-SCD-ESC-2022)
- ES in structural heart disease (SHD) is driven by an unstable arrhythmic substrate (typically post-infarction scar-based re-entry), sympathetic activation, electrolyte disturbances, or ischaemia. (sources/VA-SCD-ESC-2022)
- In primary electrical diseases, ES is driven by triggered activity: catecholamine-driven DADs in CPVT; short-coupled R-on-T PVCs in IVF/ERS; adrenergic facilitation in BrS. (sources/VA-SCD-ESC-2022)
- ES in ICD recipients is associated with increased long-term mortality independent of the underlying disease and the number of shocks delivered. (sources/VA-SCD-ESC-2022)
Acute Management Algorithm (ESC 2022)
Step 1 — Correct reversible triggers (Class I):
- Treat electrolyte disturbances (hypo-K⁺, hypo-Mg²⁺).
- Exclude acute ischaemia/ACS and treat if present.
- Identify and stop QT-prolonging drugs.
- Treat fever (antipyretics in BrS).
Step 2 — Deep sedation and analgesia (Class I):
- Reduces sympathetic tone; key in all ES regardless of aetiology.
- Intubation + mechanical ventilation for refractory cases.
Step 3 — Antiarrhythmic therapy (based on aetiology):
- SHD-associated ES:
- IV amiodarone: Class I (reduce recurrent VT/VF).
- IV beta-blockers: Class I (reduce adrenergic drive — BUT avoid in haemodynamic compromise).
- IV procainamide: Class IIa if SMVT with haemodynamic tolerance.
- IVF/ERS-associated ES:
- IV isoproterenol: Class IIa (increases heart rate, suppresses short-coupled PVCs).
- IV verapamil: Class IIa (suppresses triggered Purkinje activity).
- Quinidine: Class IIa (chronic therapy to prevent recurrence).
- CPVT-associated ES:
- IV beta-blockers (Class I); isoproterenol contraindicated.
- BrS-associated ES:
- IV isoproterenol: Class IIa.
- Acquired LQTS with TdP:
- IV magnesium + potassium correction: Class I.
- IV isoproterenol or transvenous pacing to increase heart rate: Class I.
Step 4 — Emergency catheter ablation (Class I for SMVT):
- Catheter ablation is recommended for incessant VT or ES due to SMVT refractory to AADs.
- Epicardial access may be required in non-ischaemic aetiology.
- Ablation addresses reentrant substrate; not effective against triggered-activity VA.
- VANISH2 (2025): VT storm was defined as the primary endpoint component in this trial; catheter ablation as first-line therapy showed a non-significant trend toward fewer VT storm events (HR 0.95) vs antiarrhythmic drugs over 4.3 years. This suggests ablation does not markedly reduce acute VT storm risk — its benefit is mainly on chronic arrhythmia suppression. (sources/vt-ablation-vanish2-nejm-2025, rating: very high)
Step 5 — Mechanical circulatory support:
- Intra-aortic balloon pump or percutaneous LVAD (e.g., Impella) to maintain haemodynamic stability during ablation in high-risk patients.
- Consider extracorporeal membrane oxygenation (ECMO) for refractory cases.
Step 6 — Autonomic modulation:
- LCSD (Class IIa): Left cardiac sympathetic denervation if other measures fail, especially in CPVT or refractory SHD ES.
- Thoracic epidural anaesthesia (Class IIb): Alternative sympathetic blockade.
- Bilateral stellate ganglion blockade: Emergency option.
Connections
- Related to entities/Idiopathic-Ventricular-Fibrillation
- Related to entities/CPVT
- Related to entities/Brugada-Syndrome
- Related to entities/Long-QT-Syndrome
- Related to entities/Early-Repolarization-Syndrome
- Related to concepts/Left-Cardiac-Sympathetic-Denervation
- Related to concepts/Sudden-Cardiac-Death
Contradictions / Open Questions
- Optimal pharmacological sequencing in SHD-associated ES not established by RCTs.
- Role of stellate ganglion blockade vs. LCSD in refractory non-operative setting is unresolved.
- Timing and selection criteria for emergency catheter ablation in haemodynamically unstable ES remain expert opinion (Level C evidence).
- Ablation does not markedly reduce VT storm: VANISH2 (2025) found catheter ablation as first-line therapy led to a non-significant reduction in VT storm vs antiarrhythmic drugs (HR 0.95; 21.7% vs 23.5%). The primary benefit of ablation was on sub-threshold VT and ICD shocks, not ES episodes. This raises the question of whether ES reduction requires a different approach or endpoint than substrate ablation alone. (sources/vt-ablation-vanish2-nejm-2025)