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 TSRI researchers develop new method to 'fingerprint' HIV
29.03.2017 | Scripps Research Institute

nachricht Periodic ventilation keeps more pollen out than tilted-open windows
29.03.2017 | Technische Universität München

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: A Challenging European Research Project to Develop New Tiny Microscopes

The Institute of Semiconductor Technology and the Institute of Physical and Theoretical Chemistry, both members of the Laboratory for Emerging Nanometrology (LENA), at Technische Universität Braunschweig are partners in a new European research project entitled ChipScope, which aims to develop a completely new and extremely small optical microscope capable of observing the interior of living cells in real time. A consortium of 7 partners from 5 countries will tackle this issue with very ambitious objectives during a four-year research program.

To demonstrate the usefulness of this new scientific tool, at the end of the project the developed chip-sized microscope will be used to observe in real-time...

Im Focus: Giant Magnetic Fields in the Universe

Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.

The results will be published on March 22 in the journal „Astronomy & Astrophysics“.

Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...

Im Focus: Tracing down linear ubiquitination

Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.

Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...

Im Focus: Perovskite edges can be tuned for optoelectronic performance

Layered 2D material improves efficiency for solar cells and LEDs

In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...

Im Focus: Polymer-coated silicon nanosheets as alternative to graphene: A perfect team for nanoelectronics

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

International Land Use Symposium ILUS 2017: Call for Abstracts and Registration open

20.03.2017 | Event News

CONNECT 2017: International congress on connective tissue

14.03.2017 | Event News

ICTM Conference: Turbine Construction between Big Data and Additive Manufacturing

07.03.2017 | Event News

 
Latest News

Researchers shoot for success with simulations of laser pulse-material interactions

29.03.2017 | Materials Sciences

Igniting a solar flare in the corona with lower-atmosphere kindling

29.03.2017 | Physics and Astronomy

As sea level rises, much of Honolulu and Waikiki vulnerable to groundwater inundation

29.03.2017 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>