RESUMEN
In real electrophysiological experiments, irregularities in the extracellular excitation spread are believed to depend on cardiac tissue microstructure. An electronic hardware model was developed to analyze this dependence by placing some inhomogeneities (slow propagation areas) in the medium. The position of such inhomogeneities is correlated with abnormal delays and irregularities measured in signal propagation.
Asunto(s)
Sistema de Conducción Cardíaco/fisiología , Modelos Cardiovasculares , Animales , Fenómenos Biofísicos , Biofisica , Electrofisiología , Cobayas , Técnicas In Vitro , Transducción de SeñalRESUMEN
To study the spread of excitation in ventricular heart preparations we have designed a fast, high-resolution recording and mapping system. Papillary muscles were dissected from the isolated guinea pig hearts. The preparation was fixed in a tissue bath and superfused with Tyrode solution. Linear and two-dimensional arrays of Ag/AgCl electrodes were made on glass with a thin-film technique. The transparent sensors with up to 24 electrodes (spaced 50, 90, or 180 microns apart) were positioned close to the surface of the preparation with a custom-designed three-dimensional micromanipulator. Extracellular signals were simultaneously recorded by a 24-channel data acquisition system with a 200 kHz per channel sample rate, with 12-bit amplitude resolution and a maximum data length of up to 3 MB. Digitized video images of the electrode array and the underlaying preparation were used to identify the locations of the recording sites. A UNIX-based computer system with a custom-designed data acquisition and database program was used to control the instruments and to manage the experimental data. This technique gave signals with excellent signal-to-noise ratios (up to 65 dB) and permitted accurate evaluation of the time and the site of the local activation with high resolution (to within 5 microseconds, 50 microns). We describe the spread of excitation within the area of a few cells and found a substantial dispersion of conduction velocities. Beat-to-beat comparison of activation patterns showed relatively small variations in the spread of excitation (a few microseconds).