reentry

reentry /re·en·try/ (re-en´tre) 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 also requires refractoriness of the tissue to stimulation and an area of unidirectional block to conduction.reen´trant

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re·en·try (r-ntr)

n.

Return of the same impulse into an area of heart muscle that it has recently activated but that is now no longer refractory, as in reciprocal rhythm.

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reentry

[rē·en′trē]

Etymology: L, re, again; Fr, entrée

(in cardiology) the reactivation of myocardial tissue for the second or subsequent time by the same impulse. Reentry is one of the most common arrhythmogenic mechanisms. For example, paroxysmal supraventricular tachycardia may be caused by sinus nodal reentry, atrioventricular (AV) nodal reentry, or AV reentry by way of the AV node and an accessory pathway; atrial flutter is caused by an atrial macroreentry circuit. Reentry also underlies some forms of ventricular tachycardia and extrasystoles. AV and AV nodal reentry mechanisms may be terminated by a vagal maneuver, adenosine, or procainamide.

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reentry [re-en´tre]

in cardiology, 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; see also circus movement.

atrioventricular (AV) nodal reentry an arrhythmia-causing mechanism in which two opposing pathways are established within the atrioventricular node (longitudinal dissociation); the anterograde pathway, which is usually slower, activates the ventricles and the retrograde pathway, which is usually faster, activaties the atria. This mechanism is responsible for approximately half of symptomatic paroxysmal supraventricular tachycardias.