Reentrant Ventricular Rhythms in the Canine Postinfarction Heart

Abstract

Reentrant excitation is an important mechanism of ventricular arrhythmias associated with myocardial ischemia and infarction. In 1977, El-Sherif and associates made the observation that in dogs that survived the initial stage of myocardial infarction arrhythmias and that were studied 3–5 days postinfarction, reentrant ventricular rhythms occurred spontaneously but were more commonly induced by programmed electrical stimulation [1–3]. The anatomic and electrophysiologic substrates for the reentrant rhythms were later characterized in a series of reports [4–12]. Those zones (arcs) of functional conduction block were attributed to ischemia-induced spatially nonhomogeneous lengthening of refractoriness. Sustained reentrant tachycardia was found to have a figure 8 activation pattern, whereby a clockwise and counterclockwise wavefront oriented around two separate arcs of functional conduction block. The two circulating wavefronts coalesced into a common wavefront that conducted slowly between the two arcs of block. Using reversible cooling, reentrant excitation could be successfully terminated only from localized areas along the common reentrant wavefront [7]. In the present report, we will describe in more detail the electrophysiologic characteristics of reentrant excitation in the canine postinfarction heart.