Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Accelerated heartbeart mystery: Is odd electrical wave the key?

25.10.2004


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 sometimes be setting off the same pattern in the heart."

Tung’s lab is one of the few in the world that studies electrical activity in large-scale cardiac cell cultures. The Johns Hopkins researchers collect ventricular cells from newborn rats and remove the connective tissue. The remaining cardiac cells are placed in a nutrient solution, where they thrive and establish electrical connections with one another. The result is a roughly circular single-cell layer of cardiac cells, about 2 centimeters in diameter, situated atop a microscope cover slip.

For the experiments in their new study, Tung’s team stained the cells with a voltage-sensitive dye. The researchers then used the tip of a platinum wire to administer electric pulses to the cell culture. Within milliseconds of each jolt, a wave of electrical activity moved through the culture, causing the stained cells to glow as it passed through them. An optical-fiber bundle beneath the culture captured this light show, enabling the researchers to see the shape and movement of each electrical wave as it passed through the cardiac cells.

This gave the researchers a glimpse into the type of electrical activity that takes place in the heart. In a healthy organ, these waves move smoothly through the cardiac cells, causing the muscle fibers to contract and pump blood in a coordinated manner, like soldiers marching in near lockstep. During ventricular tachycardia, however, electrical waves can often form in the shape of a single-arm spiral, throwing the cellular soldiers out of sync and into a very fast but inefficient rhythm that results in a weakened pump output. Implanted devices can deliver a series of electrical pulses to disrupt these errant waves and restore a normal heartbeat.

The Johns Hopkins researchers found that the same kind of spiral wave behavior could be reproduced in their cell cultures, making the spiral waves available for scrutiny. Just as is the case with implanted devices, when electrical pulses were administered to single-arm spirals, the waves were not always halted. Instead, they broke up into a new pattern called multiarm spirals, exhibiting complex wave dynamics and an accelerated rhythm. The researchers hypothesize that what they witnessed in the lab may mirror what happens when an implanted device inadvertently triggers an accelerated heartbeat. "The basic rules on how waves propagate and respond to electrical stimuli may best be learned in simplified models of the heart," Tung said. "With further research, it may be possible to evaluate and optimize different anti-tachycardia algorithms."

Funding for this research was provided by the Mid-Atlantic Affiliate of the American Heart Association and the National Institutes of Health.

Bursac, the lead author of the study, is now an assistant professor of biomedical engineering at Duke University. Felipe Aguel, a co-author of the study, was a postdoctoral fellow in Tung’s lab when the research was conducted. He is now a staff fellow with the U.S. Food and Drug Administration.

Phil Sneiderman | EurekAlert!
Further information:
http://www.jhu.edu

More articles from Health and Medicine:

nachricht GLUT5 fluorescent probe fingerprints cancer cells
20.04.2018 | Michigan Technological University

nachricht Scientists re-create brain neurons to study obesity and personalize treatment
20.04.2018 | Cedars-Sinai Medical Center

All articles from Health and Medicine >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Spider silk key to new bone-fixing composite

University of Connecticut researchers have created a biodegradable composite made of silk fibers that can be used to repair broken load-bearing bones without the complications sometimes presented by other materials.

Repairing major load-bearing bones such as those in the leg can be a long and uncomfortable process.

Im Focus: Writing and deleting magnets with lasers

Study published in the journal ACS Applied Materials & Interfaces is the outcome of an international effort that included teams from Dresden and Berlin in Germany, and the US.

Scientists at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) together with colleagues from the Helmholtz-Zentrum Berlin (HZB) and the University of Virginia...

Im Focus: Gamma-ray flashes from plasma filaments

Novel highly efficient and brilliant gamma-ray source: Based on model calculations, physicists of the Max PIanck Institute for Nuclear Physics in Heidelberg propose a novel method for an efficient high-brilliance gamma-ray source. A giant collimated gamma-ray pulse is generated from the interaction of a dense ultra-relativistic electron beam with a thin solid conductor. Energetic gamma-rays are copiously produced as the electron beam splits into filaments while propagating across the conductor. The resulting gamma-ray energy and flux enable novel experiments in nuclear and fundamental physics.

The typical wavelength of light interacting with an object of the microcosm scales with the size of this object. For atoms, this ranges from visible light to...

Im Focus: Basel researchers succeed in cultivating cartilage from stem cells

Stable joint cartilage can be produced from adult stem cells originating from bone marrow. This is made possible by inducing specific molecular processes occurring during embryonic cartilage formation, as researchers from the University and University Hospital of Basel report in the scientific journal PNAS.

Certain mesenchymal stem/stromal cells from the bone marrow of adults are considered extremely promising for skeletal tissue regeneration. These adult stem...

Im Focus: Like a wedge in a hinge

Researchers lay groundwork to tailor drugs for new targets in cancer therapy

In the fight against cancer, scientists are developing new drugs to hit tumor cells at so far unused weak points. Such a “sore spot” is the protein complex...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Invitation to the upcoming "Current Topics in Bioinformatics: Big Data in Genomics and Medicine"

13.04.2018 | Event News

Unique scope of UV LED technologies and applications presented in Berlin: ICULTA-2018

12.04.2018 | Event News

IWOLIA: A conference bringing together German Industrie 4.0 and French Industrie du Futur

09.04.2018 | Event News

 
Latest News

Magnetic nano-imaging on a table top

20.04.2018 | Physics and Astronomy

Start of work for the world's largest electric truck

20.04.2018 | Interdisciplinary Research

Atoms may hum a tune from grand cosmic symphony

20.04.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>