Mechanisms and pharmacological control of ventricular spiral-wave reentry

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We have analyzed dynamics of spiral-wave reentry in rabbit hearts perfused in-vitro using our original optical mapping system with a high spatio-temporal resolution.1. Development of a new optical mapping system using a high-speed digital video camera combined with light-emitting diodes.This system has an advantage over ones reported previously by other investigators in terms of high spatio-temporal resolutions (0.1 mm and 1.3 ms) and signal quality (S/N ratio 10.6) combined with less photo-bleaching (2.4%/min), and this system enables us to analyze the detail of the spiral-wave dynamics during cardiac tachyarrhythmias.2. Analysis of ventricular spiral dynamicsDynamics and pharmacological modulation of spiral reentry during ventricular tachycardia (VT) was investigated in a two-dimensional anisotropic subepicardial layer of rabbit ventricular myocardium by use of our original high-resolution optical mapping system. VT induced by cross-field stimulation was often caused by single-loop r … More eentry around a functional line of block. The functional block line was formed by meandering of the spiral tip along its own refractory tail (refractory block line) combined with pronounced conduction delay at the pivot points around the both ends of the central refractory block line (conduction block). The latter was always oriented parallel to the subepicardial fiber direction. There was no isoelectric segment (fully-excitable gap) between action potentials, and low-amplitude double potentials were obtained at the central refractory block line. Blockade of Na^+ channels by pilsicainide or disopyramide markedly enhanced conduction delay at the pivot points resulting in a prolongation of the functional conduction block line. Around the pivot points, the action potentials showed slow upstroke and long duration, but after making a turn, normal action potentials with a short excitable gap were observed. These results suggest that dynamics of two-dimensional ventricular spiral reentry is determined primarily by (1) the curvature of a wavefront, (2) tissue anisotropy and (3) the wavefront-tail interaction. Less