September 30, 2011

A Less Painful Way To Jolt A Heart

(Ivanhoe Newswire) -- Painful jolts are so yesterday!  Each year in the United States, more than 200,000 people have a cardiac defibrillator implanted in their chest to deliver a high-voltage shock to prevent sudden cardiac death from a life-threatening arrhythmia.  While it is a necessary and effective preventive therapy, those who have experienced a defibrillator shock say it is painful, and some studies suggest that the shock can damage heart muscle.

Scientists at John Hopkins believe they have found a kinder and gentler way to halt the rapid and potentially fatal irregular heart beat known as ventricular fibrillation.
According to a recent study, the use of lower amplitude and high-frequency alternating current at 100-200 Hz to stop the arrhythmia was effective.  Researchers say this approach may prove to be less painful for patients in comparison to standard defibrillator shocks.

"We believe we have found a way to stop a life-threatening arrhythmia by applying a high-frequency alternating current for about one-third of a second," Ronald Berger, M.D, PhD, a cardiac electro physiologist at the Johns Hopkins Heart and Vascular Institute and a professor of medicine and biomedical engineering at the Johns Hopkins University School of Medicine, was quoted as saying.

Graduate student Seth Weinberg, a co-lead author of the study, says the way heart cells behave during ventricular fibrillation is like having a football stadium full of fans, all of whom are doing the wave in an uncoordinated, disorganized fashion. "Applying the alternating current," he was quoted as saying, "is like freezing all of the fans in a position halfway between sitting and standing. When the current is turned off, the fans sit down in an orderly way, ready to be instructed to do the wave in a coordinated way."

According to Berger and his colleagues, a team of John Hopkins cardiologists and biomedical engineers, it is the first time heart cells have been put in a suspended state to interrupt ventricular fibrillation.

"The idea to put heart cells in a brief state of suspended animation came from studies showing that alternating current could be used to put nerve cells in a similar state to block the signals that cause pain," Harikrishna Tandri, M.D, assistant professor of medicine and the other co-lead author of the study, was quoted as saying.

In order to allow the team to explore the response of individual heart cells to the high-frequency electrical current, co-author Natalia Trayanova, Ph.D., professor of biomedical engineering, produced a multi-scale computational model of the heart.

While more testing is needed in animal models, the researchers are optimistic that their work may lead to a new approach to shock the human heart back to a normal rhythm.

"We are ultimately hoping to develop a device that, instead of delivering a painful, high-voltage shock when it detects a life-threatening arrhythmia, applies a more gentle alternating current for the right amount of time to stop the dangerous rhythm. We think that would be a great benefit to the millions of people worldwide who have a defibrillator to prevent sudden death," Dr.Berger was quoted as saying.

SOURCE: Science Translational Medicine, published online September 28, 2011