Dec. 11, 1998 CHAPEL HILL -- Researchers at the University of North Carolina at Chapel Hill are applying the same mathematics used for measuring the earth’s seismic activity to find early signs of heart trouble.
The study team mapped and then mathematically identified components of electrical waves recorded at the heart’s surface with each heartbeat. By doing so, the researchers pinpointed characteristics of abnormal cardiac activity typical of that which can trigger potentially fatal heart rhythm disturbances. The affected areas of heart muscle -- some smaller than a millimeter -- might then be targeted for treatment with surgery or medication.
A report of the new study appears in the December issue of the Annals of Biomedical Engineering.
"Any kind of electrical signal can be decomposed into its individual frequencies," said Dr. Timothy A. Johnson, associate professor of biomedical engineering and medicine at UNC-CH School of Medicine.
"We’ve taken a wave front, a two-dimensional structure, and we broke that complex wave into its individual wave components. We then looked at those components to see if it was possible to get an understanding of how each one changes during ischemia -- when blood supply to cardiac tissue is interrupted."
The study, a doctoral research project in Johnson’s laboratory, was conducted in pigs, whose hearts are structurally similar to humans’.
To obtain accurate electrical recordings, the UNC-CH researchers joined forces with the Biomedical Microsensors Laboratory at N.C. State University in Raleigh to design a plastic micro-electronic probe. On its tip is a 1-centimeter-square grid which contains 144 electrodes. Mounted as a patch on the heart’s surface, the probe recorded simultaneous electrical activities occurring beneath each electrode.
"On the basis of that, we were able to construct the activation wave front that was passing underneath the grid," Johnson said. He and his colleagues then applied mathematics similar to those used for analyzing seismic waves to decompose the two-dimensional wave front into its individual wave components.
"You can look at the wave fronts and determine how normal they are and whether they have an alternate pathway that may be contributing to an arrhythmia, or rhythm disturbance," Johnson explained. "When you add the mathematics, you can identify the specific character of that wave front, such as high or low frequency components, their direction and strength. This tells us a lot about the fingerprint of that wave front."
Armed with such information, doctors might map the heart’s surface during surgery to decide which portions are conducting electrical impulses properly and which ones need repair. And given the minute size of the electrode grid, the probe can be fashioned for application to the heart via a catheter that is threaded through a major blood vessel.
A catalogue of this information may be potentially helpful to doctors using those "fingerprints" to help identify patients with wave front characteristics that suggest a specific cardiac or electrical abnormality.
"The application of this mathematical method to the study of the flow of electricity in the heart provides us with a novel way to measure the electrical performance of normal and diseased hearts," said study co-author Dr. Wayne Cascio, UNC-CH associate professor of cardiology.
"We are excited about the prospect that this approach might offer advantages for the development of better antiarrhythmic drugs and more intelligent pacemakers and internal defibrillators."
The study was funded by the National Heart, Lung and Blood Institute in Bethesda, Md. Along with Johnson and Cascio, co-authors include Connie Engle and Dr. Leonard S. Gettes from the UNC-CH Division of Cardiology, Dr. H. Troy Nagle from N.C. State University, and former UNC-CH doctoral student Dr. Bonnie B. Punske, who is now with the University of Utah.
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