Medical researchers reveal clues of sudden cardiac death

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Found this article interesting. Notice the bowling ball to describe a zap.

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High-speed ‘movies’ reveal clues to causes of sudden cardiac death ToonResearch News and Publications

Ventricular fibrillation kills thousands of Americans each week by inducing abnormal electrical signals that turn their hearts into quivering “bags of worms” no longer able to pump blood. Victims die within minutes, unless the erratic heart rhythms can be halted with massive jolts of electricity from a defibrillator. Medical researchers now have moved one step closer to understanding the causes of ventricular fibrillation through a remarkable series of high-resolution movies that clearly show how the condition disrupts the electrical signals that normally govern the heart. The unique high-speed imaging system produced for the research also revealed for the first time that ventricular fibrillation may develop in two distinct phases. “We have now seen the smoking gun of fibrillation,” said Bill Ditto, a physics professor at Georgia Tech and one of the study’s co-authors. “We now have evidence of what is going on. This dramatically increases the possibility that we could develop a new defibrillator or improve existing defibrillators.” “Sudden cardiac death kills more Americans than anything else,” said Francis Witkowski, the study’s lead author and a professor of medicine at the University of Alberta in Edmonton and a medical scientist of the Alberta Heritage Foundation for Medical Research. “The median age is 59, so these are not people who are very old. This often happens with people who are suffering a first heart attack from which they could have recovered.” The movies reveal a series of unusual spiral waves that originate with “rotors” near the surface of the heart. The waves rapidly expand, flow across the heart muscle, merge and even interfere with each other, causing heart cells to contract in an uncoordinated way. Knowing how these unique waves form and behave could provide the information needed to design and test control techniques that may provide an alternative to existing defibrillators-which deliver the electrical equivalent of “a bowling ball dropped onto your chest from a two-story building.” Because the spiral waves seem chaotic in their behavior, researchers hope they can apply newly discovered chaos control techniques to restore normal heartbeat. Instead of the massive jolt of electricity, the chaos control technique might bring the heart back into normal rhythm using carefully applied electrical signals of much less energy. “The idea behind chaos control is that very small changes to a truly chaotic system dramatically change its behavior,” Ditto explained. Reducing the amount of energy could also allow defibrillators-both portable devices used by emergency medical teams and the implantable devices put into chests of people vulnerable to fibrillation-to be smaller and operate longer on their batteries. Besides visualizing spiral waves in the heart, this study of canine hearts also showed that ventricular fibrillation goes through two distinct stages. That previously unknown information should also help improve control techniques. “The electro-physiology of the heart evolves in time as ventricular fibrillation develops, and that has implications for how we attempt to control it,” said Witkowski. “The initial form, which occurs in the first several seconds of ventricular fibrillation, is a different entity from what develops over time.” Medical researchers have long known that the longer the fibrillation episode lasts, the more difficult it is to stop. They had blamed that on declining blood flow in a fibrillating heart, but Witkowski says the newly discovered two-phase pattern suggests the explanation may be more complicated. The unique imaging system used by the research team produces detailed information from as many as 16,000 points on a portion of the exterior surface of the heart. Operating at 838 frames per second, the system allows researchers to capture the rapid and disorganized waveforms for analysis. The system relies on flourescent dyes that respond to electrical changes in the cells of the canine heart muscle. Researchers expose the beating heart to high intensity lights, then image and intensify specific wavelengths of light returned by the dyes. Pioneered by Witkowksi, who is also trained as an electrical engineer, the system produces images with improved resolution compared to earlier techniques. The next step in the work is to try out chaos control techniques, using the imaging system to observe the effects. Once they find promising techniques, the researchers hope to try them on surgery patients whose hearts go into fibrillation on the operating table. The technique could also have application to atrial fibrillation, a less-serious disruption of the heart’s atrium. Sponsors for the work include the U.S. Office of Naval Research, the National Science Foundation, the Medical Research Council of Canada and the Alberta Heritage Foundation for Medical Research. | Home | Georgia Tech's Homepage | Approved by the Office of External Affairs on 09/24/97 Last Modified: July 21, 1998Contact: webadmin@...