An electrical storm (ES) is an electrically unstable state that manifests as recurrent ventricular arrhythmias (VA) over a short period of time. The management of ES requires the involvement of a multidisciplinary team, but despite advanced treatments and invasive procedures, ES is associated with high morbidity and mortality. Recently, the European Heart Rhythm Association (EHRA) issued a clinical consensus statement focusing on the pathophysiology, clinical manifestations, diagnostic evaluation, and acute and long-term management of patients with ES or clustered VA. This article excerpts some of the key points for the benefit of readers.
Center Diagram
Pathophysiological mechanisms
The pathophysiological mechanisms that lead to ES are difficult to study in humans. In rabbit models, complex interactions between enhanced sympathetic tone, calcium-related signal abnormalities, protein phosphorylation dysregulation, and arrhythmia-prone stroma have been shown to promote ventricular fibrillation (VF) episodes.
Three key factors are thought to be prerequisites for ES: (1) a "fragile" heart—a "necessary" condition for ES (the presence of cardiac disease, creating the necessary anatomical or electrical "base") ;( 2) external precipitating or triggering factors, and (3) disruption of autonomic nervous system activity, particularly sympathetic activation. While some external factors may be involved, a possible initial trigger was found in only 13% of patients with structural heart disease implanted with an implantable cardioverter-defibrillator (ICD).
Clinical presentation
Patients with clustered VA or ES can be asymptomatic or present with a wide range of symptoms. Symptoms include palpitations due to tolerated ventricular tachycardia (VT, often with VT cycle length below ICD measurements) or VT terminated by antitachycardia pacing (ATP), presyncope or syncope despite termination of VT by ATP or ICD shock, hemodynamically unstable VT or VF, need for advanced cardiovascular life support (ACLS), multiple external cardioversion/defibrillation, and even arrhythmic death.
The arrhythmias that lead to ES are mainly persistent monomorphic VT (MSVT, 86%~97%), followed by primary VF (1%~21%), MSVT/VF (3%~14%), and polymorphic VT (2%~8%) (Table 1). In more than half of patients with ES, VT/VF episodes are spaced less than 1 hour apart.
Table 1 VA isotypes and definitions
The clinical presentation of ES depends on a variety of factors, and early identification of high-risk patients and early transfer to a specialist ward for mechanical ventilation and mechanical circulatory assistance (MCS) is essential.
Acute management
01 Assessment
For patients presenting with ES, vital signs and hemodynamic status (level of consciousness, temperature, heart rate, respiratory rate, and blood pressure) must be assessed, followed by serial assessment of rhythm and hemodynamic monitoring.
02 Treatment
(1) Hemodynamically unstable ES
In the case of hemodynamic instability, ACLS therapy needs to be started immediately. Unstable patients need to be managed by an interdisciplinary team, including cardiologists, anesthesiologists, or critical care specialists who specialize in cardiac electrophysiology and cardiac implantable devices, and, in selected cases, heart failure specialists or cardiac surgeons.
Patients with VT or VF with ES and persistent hemodynamic instability should be treated according to the general principles of ACLS (Figure 1). Basic airway techniques and step therapy (balloon mask ventilation, supraglottic airway devices or endotracheal intubation, and mechanical ventilation) are recommended until adequate ventilation is achieved. High-quality chest compressions (with minimal interruption) and early defibrillation are priorities.
Figure 1 ACLS treatment for ES
(2) Treatment of the disease
Optimal management of heart failure may help stabilize the heart rhythm. If persistent myocardial ischemia is suspected, urgent coronary angiography (CAG) is mandatory, and current guidelines need to be followed in patients with ST-elevation myocardial infarction (STEMI). In patients with chronic coronary artery disease (cCAD) without STEMI, the potential benefits and risks of (complete) revascularization should be weighed. Notably, MSVT is rarely caused by ischemia, and ischemic evaluation of patients with monomorphic VT storm without acute coronary syndrome (ACS) has not improved surgical outcomes or mortality after ablation.
(3) ICD reprogramming
Supraventricular tachycardia or atrial fibrillation with rapid ventricular rate may result in inappropriate ICD therapy. Inappropriate ICD treatment can also result from cardiac or extracardiac hypersensitivity. Non-sustained VT may trigger unnecessary ICD therapy, especially if the duration of the test is set short. In these cases, ICD treatment must be interrupted and prevented by disabling the ICD and reprogramming.
Fig.2 Inappropriate ICD treatment
(4) Deep sedation and mechanical ventilation
In patients with conscious recurrent ICD shocks or symptomatic VT, mild to moderate sedation is essential to improve patient comfort and reduce sympathetic tone (Table 2). Deep sedation and mechanical ventilation can be used to successfully control drug-refractory ES. Response to deep sedation is an independent predictor of in-hospital survival.
Table 2 Sedative medication for ES patients
(5) Acute drug treatment of ES
➤ Structural heart disease
Antiarrhythmic drugs (AADs) are the cornerstone of acute treatment of ES (Table 3). The specific treatment regimen for AAD depends on the type of VA, the (possibly) underlying cause, patient characteristics (including comorbidities and patient-specific contraindications), and the availability of medications. In patients with structural heart disease, sympathetic tone inhibition with β-blockers is first-line therapy, preferably with a nonselective agent (eg, propranolol), unless contraindicated.
Table 3 Pharmacotherapy in the acute phase of ES
➤ Primary ECG disease
In patients with primary ECG disease, treatment of ES is disease-specific. Treatment of long QT syndrome (LQTS) includes immediate elimination of the ultimate trigger (acquired LQTS [aLQTS] and congenital LQTS [cLQTS]), β-blockers (preferably nonselective nadolol or propranolol), intracellular extracellular magnesium and potassium supplementation (aLQTS and cLQTS type 2), isoproterenol (aLQTS), mexiletine (cLQTS), and temporary pacemaker overdrive stimulation (aLQTS and cLQTS type 2). For patients with Brugada syndrome and idiopathic VF, the optimal treatment for ES is intravenous isoproterenol. ES is rare in catecholaminergic polymorphisms (VT), β receptor blockers and epinephrine are first-line treatments.
（6）MCS
Transient MCS may be useful in the treatment of life-threatening, refractory, hemodynamically intolerant VA, maintenance of organ perfusion, and treatment of induced arrhythmias. However, MCS is associated with non-negligible complication rates (vascular access-related, bleeding, etc.), operational logistics/complexity/accessibility, and increased cost. Due to the lack of reliable evidence for the use of MCS in the context of ES, it is difficult to draw any definitive conclusions about its role in this setting.
(7) Catheter ablation in the acute phase
Catheter ablation is the treatment of choice for monomorphic VT that does not respond to medical therapy in the acute phase and is recommended for all eligible patients to reduce ES recurrence. Catheter ablation is an option in haemodynamically stable patients if rapid rhythm control is not possible with noninvasive strategies.
(8) Self-regulation
The autonomic nervous system plays an important role in the development of VT/VF. Treatment with β blockers reduces the risk of sudden cardiac death. It is important to note that the effect of sympathetic activation extends beyond the effects of β receptor blocker therapy. Elevated sympathetic tone can also lead to the release of sympathetic neurotransmitters, such as neuropeptide Y, or may decrease the action potential course and affect the development of arrhythmias.
In addition to increasing sympathetic efferent tone, sympathetic afferent activation may also work by inhibiting vagal tone. Thus, sympathetic modulation therapies, such as stellate ganglion block (SGB), thoracic epidural anesthesia (TEA), cardiac desympathetic neuresthesia (CSD), and renal desympathetic neurography (RDN), work by altering the heart's efferent and afferent sympathetic signals.
(9) Overdrive pacing
Overdrive pacing can eliminate abnormal ventricular automaticity by covering the ectopic pacemaker. Overdrive pacing may also cause outlet block of ectopic lesions. In reentrant VT, rapid pacing may disrupt the reentry pathway by altering conduction rates and altering excitatory pathways. By shortening the ventricular refractory period, overdrive pacing may also reduce susceptibility to the phenomenon of R on T. These effects can be enhanced by the addition of AAD.
(10) Treatment strategy
For patients with VT who have failed catheter ablation, one solution is continuous radiofrequency at the adjacent contralateral site. Other treatment options include prolonged or high-power applications, bipolar ablation, simultaneous unipolar ablation, use of low-ion solutions (seminormal saline), retractable needle ablation, and ethanol ablation. However, such protocols have not been used in large-scale or randomized trials.
Management of stable patients
01Long-term treatment
In the absence of specific antiarrhythmic interventions, patients with structural heart disease have a > 50% risk of ES recurrence. The risk of ES recurrence was highest within 1 year of the event.
β receptor blockers, angiotensin-converting enzyme inhibitors (ACEIs) or angiotensin receptor blockers (ARBs), spironolactones, and angiotensin receptor-neprilysin inhibitors (ARNIs; sacubitril-valsartan) are associated with arrhythmias and a reduced risk of sudden cardiac death in patients with heart failure (HFrEF) with reduced ejection fraction. There is limited evidence that statins reduce the occurrence of VA. Preliminary data suggest a benefit from sodium-glucose cotransporter-2 (SGLT-2) inhibitors. Optimal treatment of HF is recommended to follow existing guidelines. In patients with cCAD, complete revascularization may be beneficial.
02AAD prevents recurrence of ES
(1) Treatment of chronic AAD in patients with structural heart disease
There are few randomized controlled trials or large observational studies evaluating the efficacy of AAD in preventing ES recurrence. However, potential efficacy can be extrapolated from studies investigating the overall efficacy of AAD in preventing VT recurrence. Table 4 lists antiarrhythmics used to prevent recurrence of ES. β-blockers are the cornerstone of pharmacological therapy for patients with VA in the context of structural heart disease.
Table 4 Pharmacotherapy for chronic treatment of ES patients
(2) Chronic drug treatment of primary ECG diseases
β receptor blockers are the cornerstone of chronic treatment of LQTS, and non-selective agents (preferred long-acting propranolol and nadolol) have been shown to be more effective. Drug therapy has a limited role in Brugada syndrome, but quinidine is beneficial in preventing VA, ES, and recurrent ICD shocks. Catecholaminergic polymorphisms (VTs) respond well to β blockers.
03Catheter ablation to prevent ES recurrence
Catheter ablation is increasingly being used in VA and offers an alternative to AAD treatment, particularly in cases where AAD is not tolerated, ineffective, or undesirable.
Surgical risks and expected outcomes depend on the individual characteristics of the patient (including specific underlying etiology, stromal location/extent, comorbidities, previous surgeries, and previous ablation attempts), as well as the experience of the treatment center and operator. It is recommended that patients be provided with detailed surgical information, risks, and expected outcomes for shared decision-making.
医脉通编译自：Radosław Lenarczyk, Katja Zeppenfeld, Jacob Tfelt-Hansen. et al. Management of patients with an electrical storm or clustered ventricular arrhythmias: a clinical consensus statement of the European Heart Rhythm Association of the ESC-endorsed by the Asia-Pacific Heart Rhythm Society, Heart Rhythm Society, and Latin-American Heart Rhythm Society. Europace. 2024 Mar 30; 26(4):euae049.
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