Pacing to Predict Mechanism: Transient Entrainment and Reentry
As summarized recently , until the last decade or so, it was generally thought that cardiac rhythms resulted either from an automatic mechanism or a reentrant mechanism. Nevertheless, apart from the early and classic experiments of Mayer  on reentry in the Medusa ring, and subsequent studies by Mines  on ring preparations cut from dogfish auricles or from canine right ventricles, it was only with the publications of the in vitro studies of depressed bundles and loops of canine Purkinje fibers in 1972 by Wit et al. [4, 5] that the occurrence of reentry actually was documented. Before the latter studies, reentrant mechanisms had been postulated as being present in many arrhythmias, but this postulate was based primarily on indirect evidence. In fact, for in vivo rhythms, it had been thought that one could distinguish reentrant arrhythmias from automatic rhythms by a few key characteristics. Simply stated, it was generally accepted that if the rhythm could be either initiated or terminated by premature beats or rapid pacing, the rhythm was due to a reentry mechanism .
KeywordsVentricular Tachycardia Atrial Flutter Atrial Pace Pace Rate Slow Conduction
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