Electrical storm : refers to a state of cardiac electrical instability characterized by multiple episodes of ventricular tachycardia (VT storm) or ventricular fibrillation (VF storm) within a relatively short period of time, typically 24 hours . The clinical definition of electrical storm is varied, somewhat arbitrary, and is a source of ongoing debate . ●In patients without an implantable cardioverter-defibrillator (ICD), electrical storm has been variously defined as : •The occurrence of two or more hemodynamically stable ventricular tachyarrhythmias within 24 hours •VT recurring soon after (within five minutes) termination of another VT episode •Sustained and non-sustained VT resulting in a total number of ventricular ectopic beats greater than sinus beats in a 24-hour period. ●In patients with an ICD, the most widely accepted definition of electrical storm is three or more appropriate therapies for ventricular tachyarrhythmias, including antitachycardia pacing or shocks, within 24 hours . However, this definition is not comprehensive as it fails to account for: •VT that is slower than the programmed detection rate of the ICD •VT that fails to terminate with appropriate ICD therapy and remain undetected by the patient .TRIGGERS OF ELECTRICAL STORM — Most patients with electrical storm or incessant VT have severe underlying structural heart disease, and studies have revealed an inciting factor in only a minority of patients with electrical storm. However, careful assessment is required as some of the known triggers are reversible, including ●Drug toxicity ●Electrolyte disturbances (ie, hypokalemia and hypomagnesemia) ●New or worsened heart failure ●Acute myocardial ischemia ●QT prolongation (which may be related to drug toxicity, electrolyte imbalance, or an underlying syndrome such as long QT syndrome) These varied triggers highlight the complex interactions between anatomic substrate, autonomic tone, and cellular milieu that result in electrical storm. DIFFERENTIAL DIAGNOSIS — The differential diagnosis of electrical storm should be thought of differently depending on the presence or absence of an ICD: ●In patients without an ICD, the differential diagnosis includes the usual causes of a wide QRS complex tachycardia . ●In patients with an ICD who receive multiple ICD shocks, the differential diagnosis includes the usual causes of a wide QRS complex tachycardia as well as the possibility of ICD malfunction (eg, electrical noise, oversensing, lead fracture, etc). TREATMENT — In patients with an acute and ongoing episode of electrical storm or incessant VT, initial treatment is based on hemodynamic stability or instability. ●Patients with hemodynamically unstable ventricular arrhythmias should initially undergo electrical cardioversion according to advanced cardiac life support protocol. ●For patients with electrical storm or incessant VT who are hemodynamically stable, we recommend intravenous amiodarone as the initial antiarrhythmic agent given its superior efficacy for terminating most ventricular arrhythmias. Additionally, because of the adrenergic surge associated with frequently ventricular tachyarrhythmias and defibrillator shocks, we recommend co-administration of a beta blocker (usually metoprolol as it is available in both IV and oral formulations). ●For patients with electrical storm or incessant VT in whom active myocardial is felt to be a contributing factor, urgent coronary revascularization should be pursued.
Posted on: Fri, 24 Oct 2014 08:32:24 +0000
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