Number 237 (Story #2), August 15, 1995 by Phillip F. Schewe and Ben Stein A MAJOR CLASS OF HEART ATTACK HAS UNEXPECTEDLY NON-RANDOM CHARACTERISTICS , new evidence suggests, opening the future possibility of clinical treatment with the tools of chaos theory. Always fatal within minutes, ventricular fibrillation (VF) is the uncoordinated twitching of muscle fibers in the main pumping chambers of the heart. Whereas most previous research has assumed VF to be a random process, an interdisciplinary team of researchers in Canada and the U.S. (including Daniel Kaplan of McGill University, danny@cnd.mcgill.ca) has found the first evidence for subtle patterns in the rhythms associated with VF. Analyzing the electrical activity during VF episodes in dogs, the team developed and applied statistical tests to demonstrate that the complex electrical rhythms of fibrillating hearts appear to have non-random "deterministic" characteristics; that is, they can be described by mathematical equations that relate the system's future state to its past and present conditions. Deterministic systems offer the possibility of "feedback control" of the type used to nudge seemingly random chaotic systems into a desired state. But the researchers caution that "the practical implementation of such control is still highly speculative and will present significant challenges." (F.X. Witkowski et al., Physical Review Letters, 7 August 1995.) In a separate development, Leon Glass of McGill University (514-398-4338) and Mark Josephson of Beth Israel Hospital in Boston (617-667-4387) have developed a mathematical model for describing a type of rapid heartbeat known as re-entrant tachycardia. Its further development may help cardiologists to better identify the condition and to learn the types of electrical activity in the heart that can trigger and terminate the condition. (L. Glass et al., upcoming article in Physical Review Letters. Texts and figures are available to science writers.)