Electrical storm. Definition, prevalence, causes and prognostic implications

Background. Electrical storm (ES) represents a state of cardiac electrical instability which manifests by multiple episodes of ventricular tachyarrhythmia (VT) within a short time. In patients with an implantable cardioverter- defibrillator (ICD), ES is best defined as ≥3 appropriate VT detections in 24 h, treated by antitachycardia pacing or shock. The number of shocks and inappropriate detections are irrelevant for the definition. Within a period of 3 years ES occurred in approximately 25 % of ICD patients with secondary prophylaxis indications of sudden cardiac death. Although the definition includes minor arrhythmic events, ES frequently consists of up to 50 VTs. Potential triggers found in 20-65 % of patients include new/deteriorated heart failure, diarrhea/hypokalemia, changes in antiarrhythmic medication, association with other illnesses, and psychological stress. In most patients ES consists of monomorphic VT indicating the presence of reentry while ventricular fibrillation indicating acute ischemia is rare. Material and methods. ES seems to have a low immediate mortality (1 %) but frequently (50-80 %) leads to hospitalization. Long-term prognostic implications of ES are unclear. The key intervention in ES is a reduction of the elevated sympathetic tone by beta blockers and also frequently sedation. Amiodarone i.v. is highly efficient in ES while class I antiarrhythmic drugs are usually unsuccessful. Substrate mapping and VT ablation may be useful in treatment and prevention of ES. Prevention of ES requires ICD programming systematically avoiding unnecessary shocks by long VT detection and numerous attempts of antitachycardia pacing before shock therapy which can fuel the sympathetic tone and prolong ES. © 2014 Springer-Verlag.