ARLINGTON , Va. , Oct. 7, 2004 – Biomedical engineers have devised a more efficient and safe method of defibrillation therapy than current implanted devices.

When implanted defibrillators detect an erratic heartbeat (arrhythmia), they send a significant shock to the entire heart to reset its electrical rhythm back to normal. Igor Efimov, Ph.D., an associate professor of biomedical engineering at Washington University in St. Louis , and his colleagues have developed a prototype system that would deliver minor, more targeted shocks. An implantable defibrillator using more efficient shocks would be smaller, safer, more comfortable, and, because it would use less electrical energy, last longer than conventional defibrillators.

Nearly 1 million people die in the United States each year because of heart disease, about one-third due to heart arrhythmia. Arrhythmia occurs when the electrical signals that keep the heart contracting and pumping blood become disrupted. Electrical waves begin swirling independent of one another, throwing the heart into cardiac arrest.

Currently, only a tiny fraction of arrhythmia patients survive. But Efimov estimates that, under optimal conditions, the survival rate could be brought up to about half.

In developing a more efficient system, Efimov and his team took advantage of three arrhythmia-related facts: most arrhythmia patients who wear a defibrillator have had a previous infarction; previous infarctions usually produce scaring in the heart muscle tissue; and this scar tissue seems to attract the swirling electrical waves.

“We thought, ‘Why don't we just affect the important part of the heart that sustains arrhythmia?'” says Efimov. “Instead of shocking the whole heart, let's shock just the activity around the scar. It's much gentler and requires less energy.”

When the computer model detects the swirling electrical impulses, it sends a small shock around the point of scarring, which scatters the electrical swirls and prevents them from sabotaging the heart's rhythm. Efimov estimates that shocks under the new model would be 5 to 10 times less powerful than the shock of standard defibrillators. Efimov and colleagues Valentin Krinsky, Ph.D., at Washington and Alain Pumir, Ph.D., of the Nonlinear Institute of Nice, France, published their results in July in Physical Review Letters.

Efimov and colleagues plan to begin testing the new system in rabbit hearts. “We believe that the new knowledge will enhance cardiac implantable device therapy by improving our understanding of the mechanisms underlying the interaction of cardiac structure with electrical impulse,” says Efimov.

Efimov received a Whitaker Research Grant in 2001 to support this work.

Contact:
Igor Efimov, Washington University
Mark Bowman, The Whitaker Foundation