- extrastimulus
- ex·tra·stim·u·lus (ek″strə-stimґu-ləs) a premature stimulus delivered, singly or in a group of several stimuli, at precise intervals during a tachyarrhythmia in order to terminate it. Delivery of stimuli may be synchronous or asynchronous with the arrhythmia; if synchronous, delivery may be preprogrammed or adaptive to the tachycardia cycle length. Premature stimuli may also be delivered during cardiac electrophysiologic testing to initiate supraventricular or ventricular tachycardia.
Programmed extrastimulus used to initiate ventricular tachycardia. The last two ventricular-paced beats at a cycle length of 600 milliseconds are shown. Two premature stimuli (S1, S2) initiate a sustained monomorphic tachycardia at a cycle length of 300 milliseconds.
Medical dictionary. 2011.