[Dynamics of the electrical activity in the form of a vortex with a straight filament in ground squirrel heart].

Attacks of tachysystolia have been studied, which were induced by premature stimuli (amplitude up to 4-5 diastolic thresholds, duration 4 ms) applied after a set of rectangular impulses (amplitude 2 diastolic thresholds, duration 4 ms, frequency 0.5 or 2 Hz). The spatial and temporal distribution of electrical potential throughout the surface of a thin (approximately 1 mm) preparation was registered by two multi-electrode arrays (32 unipolar electrodes each). One array recorded the distribution of electrical potential on the endocardial surface and the other, on the epicardial one. Wave isochronous pictures (maps) corresponding to spatial and temporal propagation of excitation on the surfaces of the preparation were reconstructed on the basis of electrograms registered on each of the surfaces. On the basis of these maps, the three-dimensional structure of scroll waves, including the location, direction and velocity of the shift of filament ends as well as the shape of the thread was analyzed. The analysis of the data obtained in our experiments allow one to conclude that, under tachysystolias caused by three-dimensional scroll wave with a straight filament, there occur the following kinds of wave thread movements: (1) the wave thread may change its location from turn to turn and on the whole be located at different angles to the preparation surfaces; (2) the wave thread may precess, when one of the filament end is "secured" on the surface and the other constantly changes its location on the opposite surface; (3) the wave thread may periodically intertwine (twisted filament) and untwine; (4) dimensions of the scroll wave kernels (sections of the filament on the surfaces) may change from turn to turn both simultaneously on both surfaces (endocardial and epicardial) and on one of them only; (5) the wave thread may curve when it goes within the wall from endocardial to epicardial surfaces; the curve may come rather close the surfaces of the myocardial tissue.