Scientists have predicted that this rotating disturbance can break free and begin to circulate as a unit in the heart tissue. It may also break up into a small number of additional spiral waves, all rotating and meandering at different rates. Garfinkel and his group looked for evidence of this pattern of behavior in cardiac recordings of five patients who suffer from chronic atrial fibrillation, in multi-electrode recordings of electric activity during ventricular fibrillation in the excised, intact heart of a dog, and in maps of electric activity across thin slices of human and canine cardiac tissue in the lab. Their measurements showed waves of electric activity consistent with a scenario in which a meandering spiral wave breaks up into additional spiral waves, causing the system to destabilize and become chaotic. The data suggest that fibrillation is a form of . . .
Characteristic oscillations precede and precipitate fibrillation.
The chaotic behavior appears to arise because of interactions among distinct spiral waves meandering at different rates. A computer simulation of the process in a sheet of cardiac tissue supports the findings. The effect resembles the way in which a smoothly flowing liquid breaks up into vortices, becoming turbulent. Identifying the instabilities involved in fibrillation is difficult both theoretically and experimentally. Garfinkel and his colleagues attribute spiral wave instabilities to a characteristic known as restitution, which governs how quickly a heart cell recovers from one beat to the next.