Roanoke Times
Copyright (c) 1995, Landmark Communications, Inc.
DATE: SUNDAY, February 14, 1993 TAG: 9302140011
SECTION: NATIONAL/INTERNATIONAL PAGE: A-13 EDITION: METRO
SOURCE: Knight-Ridder/Tribune
DATELINE: LENGTH: Medium
SCIENCE CONFIRMING BASIC CONDITION OF HEART: CHAOS
The mellifluous lub-dub of a human heart, seemingly the definition of order and regularity, may be, it turns out, among the prime physiological examples of a system in chaos.As with a swinging pendulum, or a clock's tick-tock, there is a range of randomness for each millisecond of regularity.
This makes the heart subject to study by the same discipline - "fractal geometry" - used to analyze weather fluctuations, chaotic chemical reactions, Jupiter's whirling Great Red Spot, even infinitesimal oscillations in a laser beam.
To physicists and biologists studying turbulent phenomena, chaos, simply defined, is order born of randomness.
"There is a lot of beat-to-beat irregularity in a normal heart," said Ary Goldberger, an associate professor of medicine at Harvard University's medical school and director of electrocardiography at Beth Israel Hospital in Boston.
"An intuitive notion we proposed suggests that for normal people, the heartbeat, although it feels regular, has a lot of complex variability," he said.
According to this idea, a healthy heart is an organ in the throes of chaos.
"What chaos theory is in a general way is non-linear dynamics, basically the study of systems that don't play by the straight-line rules," Goldberger explained. "Their behavior is unpredictable. The components of all physiological systems have properties of these non-linear systems: the brain, the lungs, the heart valves."
The patterns underlying the behavior of those structures are the "fractals" scientists see.
A fractal, which strictly speaking means an irregular line or surface, takes its name from the ragged appearance of certain kinds of clouds. Fractal geometry embraces concepts developed by Benoit Mandelbrot of IBM's Thomas J. Watson Research Center. He mastered a way to quantify chaos, a science originally developed more than a century ago.
To the eye, fractal patterns have the same structure whether viewed from far away or close up. A coastline seen from the air or the outline of a mountain range are common examples - geometric remnants of chaotic events. The emerging science of chaos is finding unexpected order in a range of random occurrences, and increasingly in how the human body works.
Imagine, for example, a kaleidoscope of chemical activity as enzymes catalyze biochemical reactions, or the waves that signify the function of the human brain. Capturing either for posterity would reveal fragmented shapes of varying size, but similar shape - remnants of chaos.
Such geometric remains are what Goldberger finds in the electrocardiographs of chaotic but healthy hearts.
The evolving notion linking a healthy heart to erratic activity flies in the face of earlier concepts on biologic chaos.
In the mid-1980s, scientists suggested that hearts hopelessly out of synch - those overcome by arrhythmias, particularly deadly fibrillations - were examples of physiological chaos.
A fibrillating heart simply looked, acted and sounded chaotic. But that was an assumption lacking the benefit of mathematical analysis.
Now researchers such as Goldberger see chaos as the underlying key to a normally functioning heart. It is the tiny variations from one beat to another that he and his team detect, and in which they see the essence of chaos.
"This may be closer to what mathematicians call chaos. When you look at the rhythm of people with severe heart disease, their beats are more periodic and less chaotic" than in healthy people, Goldberger said.
Because beat regularities seem associated more with disease than health, Goldberger hopes to translate lofty fractal mathematics into bedside applications that ultimately will allow doctors to predict traumatic heart conditions possibly years before they occur.
Forecasting heart disease is likely, Goldberger said, because the normal heartbeat "has a pattern or scaling that is extremely well described by fractal mathematics."
Without the randomness, Goldberger said, patients could be in cardiac trouble. For reasons that have yet to be explained, increasingly "regular" cardiac activity also accompanies the aging process.