Sustained vortex-like waves in normal isolated ventricular muscle.

Abstract

Sustained reentrant excitation may be initiated in small (20 X 20 X <0.6 mm) preparations of normal ventricular muscle. A single appropriately timed premature electrical stimulus applied perpendicularly to the wake of a propagating quasiplanar wavefront gives rise to circulation of self-sustaining excitation waves, which pivot at high fequency (5-7 Hz) around a relatively small "phaseless" region. Such a region develops only very low amplitude depolarizations. Once initiated, most episodes of reentrant activity last indefinitely but can be interrupted by the application of an appropriately timed electrical stimulus. The entire course of the electrical activity is visualized with high temporal and spatial resolution, as well as high signal-to-noise ratio, using voltage-sensitive dyes and optical mapping. Two-and three-dimensional graphics of the fluorescence changes recorded by a 10 X 10 photodiode array from a surface of 12 x 12 mm provide sequential images (every msec) of voltage distribution during a reentrant vortex. The results suggest that two-dimensional vortex-like reentry in cardiac muscle is analogous to spiral waves in other biological and chemical excitable media.Many hypotheses have been postulated to explain reentrant excitation in cardiac muscle. Beginning with the classical studies of Mines (1), in which reentry occurs around an anatomical obstacle, through Allessie's leading circle hypothesis (2), to the more recently postulated anisotropic reentry (3), most mechanisms proposed by experimental electrophysiologists are focused on preexisting functional or anatomical inhomogeneities in the myocardium. On the other hand, theoretical studies based on wave propagation in other types of excitable media such as, for example, the BelousovZhabotinsky reaction (4) suggest that these rotating waves, also known as "spiral waves," "reverberators," and "vortices," may occur even in totally homogeneous and continuous media (4-8). As proposed by Winfree (9) and later shown in the whole heart (10), initiation of reentry depends not only on the properties inherent to the myocardium but also on transient local conditions created by the impulse that triggers the reentry. In fact, reentrant excitation may be initiated in the myocardium at a critical point that results from the interaction of a geometrically graded recovery of excitation (i.e., the "tail" of a planar wavefront) with a geometrically graded transverse premature stimulus (10). Our objective was to utilize these concepts to develop an in vitro model of sustained reentry, in which the electrical activity can be closely monitored. Here we demonstrate that self-sustaining vortex-like reentry can be induced in small two-dimensional pieces of cardiac muscle and that the entire course of the excitation-recovery process during the reentrant cycle can be analyzed in detail through the use of optical mapping and voltage-sensitive dyes. METHODSHearts were dissected from anesthetized sheep (sodium pentobarbital, 35 mg/kg, i.v.). Thin slices of left ventricul...

2012 HRS/EHRA/ECAS Expert Consensus Statement on Catheter and Surgical Ablation of Atrial Fibrillation: Recommendations for Patient Selection, Procedural Techniques, Patient Management and Follow-up, Definitions, Endpoints, and Research Trial Design

“…213,214,215 The rotor is the organizing center of the reentrant excitation 215 ; it spins at exceedingly high frequencies, radiating spiral wavefronts with outwardly decreasing curvature, forming an Archimedean spiral, and resulting in wave fragmentation in its periphery. 216,217 Because CV decreases as the wavefront curvature becomes steeper toward the center tip, it follows that at that site (sometimes called the phase singularity [PS]) the curvature reaches a critical value, the velocity becomes zero, and the PS follows a circular trajectory. 215,218 At each point the direction of propagation is perpendicular to the wavefront and the velocity increases toward the periphery.…”

Critical brain networks

“…Relatively simple dynamics gets sophisticated as the nonlinear term acquires relevance (moving upward in the graph) or as the number of degrees of freedom increases (moving to the right). Pictorial examples include: (1) the transition from one to many coupled pendulums, (2) few foraging ants to the entire swarm [5], (3) from the chaotic dynamics of an isolated cardiac cell [6] to the spatiotemporal spiral waves in the heart [7], (4) a sandpile and, of course, (5) the brain.…”

Rotors and Focal Sources for Human Atrial Fibrillation

“…18 Conversely, leading circle reentry requires an unexcitable/refractory core that fixes reentry, which conceptually differs from a rotor, with outward activation of peripheral tissue. Rotors were shown experimentally by Davidenko et al in 1990, 45 then supported by modeling and optical mapping of isolated animal hearts. 46, 47 Sources are often spatially and temporally stable but precess ("wobble") in small regions 46,48 re- fixed in location and rate from cycle to cycle and rotates around an "inert" obstacle.…”