triggered activity
Abnormal cardiac electrical activity initiated by afterdepolarizations that occur as a result of a preceding action potential.
Full Definition
Triggered activity is a mechanism of arrhythmogenesis where abnormal electrical impulses are generated by afterdepolarizations that follow normal action potentials. Unlike automatic rhythms that arise spontaneously, triggered activity requires an initiating beat or stimulus. There are two main types: early afterdepolarizations (EADs) that occur during phases 2 or 3 of the action potential and are associated with QT prolongation and torsades de pointes, and delayed afterdepolarizations (DADs) that occur after complete repolarization and are typically related to calcium overload states such as digitalis toxicity or catecholamine excess. Triggered activity can lead to isolated premature beats or sustained arrhythmias. Understanding this mechanism is crucial for selecting appropriate antiarrhythmic therapies and identifying underlying causes such as electrolyte disorders or drug toxicities.
Usage
Usage note: Distinguish between early and delayed afterdepolarization types when clinically relevant.
In Context
- "The patient's ventricular ectopy was attributed to triggered activity secondary to digitalis toxicity." — Cardiology consultation note
- "Triggered activity from delayed afterdepolarizations explained the exercise-induced ventricular arrhythmias." — Electrophysiology study report