Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Little-studied waves in the heart may be cause of defibrillation failure

09.12.2003


Vanderbilt University researchers believe a slow electrochemical wave, known as a damped wave, may be one of the reasons that low-voltage defibrillation shocks fail to halt fibrillation in cardiac patients.



The findings by Vanderbilt University researchers John Wikswo, Veniamin Sidorov, Rubin Aliev, Marcella Woods, Franz Baudenbacher and Petra Baudenbacher were published in the Nov. 14 issue of Physical Review Letters.

Fibrillation is a series of rapid, disorganized contractions in the heart caused by multiple uncoordinated, self-generated electrochemical waves that prevent the heart from pumping blood, quickly causing death.


"In normal conditions, an electrochemical wave moves smoothly across the heart, like expanding ripples in a lake when you toss in a stone. This wave then triggers a smooth and orderly contraction of the muscle," Wikswo, the Gordon A. Cain University Professor and Director of the Vanderbilt Institute for Integrative Biosystems Research and Education, said. "In fibrillation, it is as if someone continually throws in lots of rocks at different spots in the lake. In the resulting confusion, no blood gets pumped."

The application of a strong electrical shock, either with paddles on the chest or with an implantable defibrillator, is the best way to stop fibrillation. Ideally, a defibrillation shock would stop all waves in the heart and prevent new waves from arising spontaneously.

"You want to use as low a voltage shock as possible to minimize tissue damage and, for implantable defibrillators, to save your batteries," Wikswo continued. "However, if the voltage is too low, fibrillation returns immediately and you have to try again. The puzzle is why."

Wikswo’s study explores the possibility that some waves might not be fully extinguished by a low voltage defibrillation shock, or new waves might be created by the shock, causing defibrillation to fail. If these remaining or new waves were the difficult-to-detect damped propagating waves, they could propagate slowly within the heart wall, rather than slowly dying out as previously expected. This might cause the heart to return to fibrillation or another cardiac arrhythmia.

"Damped propagating waves are not generally well understood, largely because they are difficult to view and to study," Wikswo said. "It turns out cardiac tissue provides a beautiful example of these waves."

Although cardiac graded responses have been considered for some time, recent advances in high-speed imaging, data processing and numerical modeling are just now allowing their quantitative analysis as damped, propagating waves.

To study the damped waves, Wikswo’s team initiated a wave with a strong stimulus that moved smoothly across the heart. They then created a damped wave with a weaker stimulus and sent it in the wake of the first.

"If you timed it just right you could find that the second wave would hesitate and then split in two," Wikswo continued. "One half would get smaller and slowly die, while the other half would sharply increase and eventually become a self-continuing wave on its own."

This second, self-continuing wave could be a cause of defibrillation failure.

"What surprised us is the ease with which we could create damped waves that hung around for 50 milliseconds, which is a long time when you are defibrillating the heart," Wikswo said.

The research, conducted by studying the rabbit heart, lays the foundation for future studies to determine if the waves created under experimental conditions also occur spontaneously following defibrillation.

Future studies based on this research will be conducted to better understand how to manage these waves, the effect of anti-arrhythmic drugs on them, and whether these findings could be used to improve the efficiency of cardiac defibrillators.

Melanie Catania | Vanderbilt University
Further information:
http://sitemason.vanderbilt.edu/newspub/bjfTyg?id=8580
http://www.vanderbilt.edu/lsp/abstracts/1501-Sidorov-PRL-2003.htm

More articles from Health and Medicine:

nachricht The genes are not to blame
20.07.2018 | Technische Universität München

nachricht Targeting headaches and tumors with nano-submarines
20.07.2018 | Universitätsmedizin der Johannes Gutenberg-Universität Mainz

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: Future electronic components to be printed like newspapers

A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.

The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...

Im Focus: First evidence on the source of extragalactic particles

For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.

To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...

Im Focus: Magnetic vortices: Two independent magnetic skyrmion phases discovered in a single material

For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.

Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...

Im Focus: Breaking the bond: To take part or not?

Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.

A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...

Im Focus: New 2D Spectroscopy Methods

Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.

"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Leading experts in Diabetes, Metabolism and Biomedical Engineering discuss Precision Medicine

13.07.2018 | Event News

Conference on Laser Polishing – LaP: Fine Tuning for Surfaces

12.07.2018 | Event News

11th European Wood-based Panel Symposium 2018: Meeting point for the wood-based materials industry

03.07.2018 | Event News

 
Latest News

A smart safe rechargeable zinc ion battery based on sol-gel transition electrolytes

20.07.2018 | Power and Electrical Engineering

Reversing cause and effect is no trouble for quantum computers

20.07.2018 | Information Technology

Princeton-UPenn research team finds physics treasure hidden in a wallpaper pattern

20.07.2018 | Materials Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>