Electrical storm

A standard clinical definition of ES is 3 or more sustained VA episodes (including appropriate ICD shocks) separated by at least 5 minutes over 24 hours

Development of ES usually requires both an arrhythmic substrate and a proarrhythmic trigger

Most ES develops on a backdrop of either structural heart disease or pathogenic ion channel defects (channelopathies).
Structural heart disease can cause arrhythmogenic remodeling with the development of myocardial scar that forms the basis for re-entry and may impair the expression and function of ion channels resulting in proarrhythmic alterations in ion handling.

Triggers such as myocardial ischemia, inflammation, or hemodynamic decompensation, as well as drug and electrolyte effects, often with accompanying autonomic nervous system imbalance, can lead to sustained ventricular arrhythmia caused by re-entry and/or afterdepolarizations in those with vulnerable anatomic or electrical substrates, including myocardial scar promoting re-entry, early afterdepolarizations (EADs) from long QT syndrome, or delayed afterdepolarizations (DADs) from myocardial ischemia. Perpetuation of the inciting trigger and the resulting sympathetic nervous system response leads to recurrent ventricular arrhythmia and electrical storm (ES).

The most common mechanism for VA during ES is macro-re-entry caused by slow conduction through surviving tissue channels in scar resulting in MMVT. Additionally, micro-re-entry can result from focal inflammation or interstitial fibrosis and functional re-entry can occur via heterogeneously impaired excitability and decreased repolarization reserve, which may be augmented by myocardial stretch and elevated sympathetic tone during decompensated HF.

Re-entry requires an area of anatomic or functional conduction block, an electrical pathway with unidirectional block, and a pathway with slow or heterogeneous conduction. This substrate is present in patients with myocardial scar from a prior myocardial infarction (MI), interstitial fibrosis from dilated nonischemic cardiomyopathy (NICM), focal inflammation, or infiltrative cardiomyopathy

References

Multidisciplinary Critical Care Management of Electrical Storm - JACC