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 (10×10 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 ~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