High speed optical imaging of the initiation and termination of self-sustaining cardiac spiral waves

Ventricular fibrillation is composed of many self-sustaining reentrant electrical pathways. The simplest such reentry is a single two-dimensional spiral rotor. The authors studied the initiation, maintenance and termination of such rotors in canine cardiac tissue by staining a thin slice of epicardial tissue with the potentiometric dye di-4-ANEPPS and recording the resultant fluorescent signals with a 96-channel (10/spl times/10 minus corners) photodiode (PD) array at 500 frames/s. The authors found that, at room temperature, the rotors revolved around a partially-depolarized central hub at approximately 3 Hz. Action potentials recorded at individual PDs distal from the hub revealed that the tissue fully repolarized before being reexcited by the return of the rotor's wavefront. Furthermore, these rotors could be successfully terminated with a field stimulus greater than /spl sim/10 V/cm, with refractory period extensions responsible for its success. Indeed, this optical imaging technique records transmembrane activity with high temporal and spatial fidelity and without stimulus-induced electrical artifacts, thus making possible the examination of interactions between a rotor and a stimulus in unprecedented detail.< >