Return of the same impulse into a zone of heart muscle that it has recently activated, sufficiently delayed that the zone is no longer refractory, as seen in most ectopic beats, reciprocal rhythms, and most tachycardias.
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re·en·try (')rē-'en-trē n, pl -tries a cardiac mechanism that is held to explain certain abnormal heart actions (as tachycardia) and that involves the transmission of a wave of depolarization along an alternate pathway when the original pathway is blocked with return of the impulse along the blocked pathway when the alternate pathway is refractory and then transmission along the open pathway resulting in an abnormality
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re·en·try (re-enґtre) reexcitation of a region of cardiac tissue by a single impulse, continuing for one or more cycles and sometimes resulting in ectopic beats or tachyarrhythmias. It can exist over either an anatomical or a functional area of slowed impulse conduction and requires also refractoriness of tissue to stimulation and an area of unidirectional block to conduction. See also reflection and reentrant mechanism, under mechanism. reentrant adjMedical dictionary. 2011.