Accelerated heartbeart mystery: Is odd electrical wav...( For people who suffer from a rapid hear...),Health

For people who suffer from a rapid heartbeat condition called tachycardia, an implanted device can usually nudge the racing blood pump back into a normal rhythm by applying electrical pulses to the heart. But on rare occasions, in a twist that has baffled physicians, the anti-tachycardia pulses produce the opposite effect: they trigger an even faster and more dangerous heartbeat.

By electrically jolting cardiac cells in a lab and mapping the change in the electrical activity, biomedical engineers at Johns Hopkins may have found an answer to this mystery. Writing in the "Proceedings of the National Academy of Sciences," the researchers proposed that maverick electrical waves called multiarm spirals may be causing the accelerated heartbeats. Their article appeared this week in the journal's online Early Edition and will be published in the Oct. 26 print edition.

The findings could lead to improvements in the next generation of implantable cardioverter defibrillators, devices used by tens of thousands of people with heart rhythm abnormalities. "At present, the devices can be programmed by the physician to deliver any one of many different combinations of pulse parameters, and although standard algorithms exist, the optimum algorithm is not known," said Leslie Tung, a co-author of the paper and director of the lab in which the research was conducted. Tung is an associate professor in the Department of Biomedical Engineering at Johns Hopkins.

"When the condition called ventricular tachycardia is accelerated to the point where it becomes indistinguishable from ventricular fibrillation, the patient must now receive a powerful, painful shock to restore normal rhythm, a scenario that is best avoided," said lead author Nenad Bursac, who worked on the research as a postdoctoral fellow in Tung's lab. "We are the first to show that these multiarm spiral waves can be electrically induced in sheets of cardiac cells, and we think that implanted devices could
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Contact: Phil Sneiderman
prs@jhu.edu
443-287-9960
Johns Hopkins University
22-Oct-2004

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