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an oscillation in membrane potential that is dependent upon a preceding action potential for its initiation, and which upon reaching threshold potential can induce arrhythmias that are said to be “triggered.” Early afterdepolarizations occur during phases 2 and 3 of repolarization; delayed afterdepolarizations follow full repolarization.
afterdepolarization/af·ter·de·po·lar·iza·tion/ (af″ter-de-po″lar-ĭ-za´shun) a depolarizing afterpotential, frequently one of a series, sometimes occurring in tissues not normally excitable. It may occur before (early a.) or after (delayed a.) full repolarization.
a membrane potential depolarization that follows an action potential. In cardiac muscles, it may be early (during phases 2 and 3 of the action potential) or delayed (during phase 4), and it is thought to cause atrial and ventricular tachycardia, especially in the setting of a long Q-T interval or digitalis poisoning. Also called afterpotential.
in myocardial activity a polarization, sufficient to trigger a cardiac cycle, which results from a preceding impulse or series of impulses.