Regional Capture of Fibrillating Ventricular Myocardium

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Abstract
Previous investigations have suggested that during ventricular fibrillation (VF) pacing stimuli are incapable of evoking propagated ventricular activations. To determine whether regional myocardial capture could be achieved during rapid pacing in VF, extracellular unipolar potentials were sampled (2 kHz) and recorded from 506 Ag-AgCl electrodes arranged in a rectangular grid (22×23, 1.12-mm spacing) embedded in a plaque overlying two pacing electrodes in the epicardium of the anterobasal right ventricle in pentobarbital-anesthetized pigs (25 to 30 kg, n=6). During separate episodes of electrically induced VF, two bursts of 40 monophasic stimuli (10 mA, 2-millisecond duration) were asynchronously applied to the stimulating electrodes in either a bipolar, unipolar anodal, or unipolar cathodal mode. Evidence of regional capture was provided by (1) animating the first temporal derivative of the extracellular potentials, (2) analyzing interbeat interval patterns, and (3) employing the Karhunen-Loeve d...

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