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 Using fragment-based approaches to discover new antibiotics
21.06.2018 | SLAS (Society for Laboratory Automation and Screening)

nachricht Scientists learn more about how gene linked to autism affects brain
19.06.2018 | Cincinnati Children's Hospital 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: Temperature-controlled fiber-optic light source with liquid core

In a recent publication in the renowned journal Optica, scientists of Leibniz-Institute of Photonic Technology (Leibniz IPHT) in Jena showed that they can accurately control the optical properties of liquid-core fiber lasers and therefore their spectral band width by temperature and pressure tuning.

Already last year, the researchers provided experimental proof of a new dynamic of hybrid solitons– temporally and spectrally stationary light waves resulting...

Im Focus: Overdosing on Calcium

Nano crystals impact stem cell fate during bone formation

Scientists from the University of Freiburg and the University of Basel identified a master regulator for bone regeneration. Prasad Shastri, Professor of...

Im Focus: AchemAsia 2019 will take place in Shanghai

Moving into its fourth decade, AchemAsia is setting out for new horizons: The International Expo and Innovation Forum for Sustainable Chemical Production will take place from 21-23 May 2019 in Shanghai, China. With an updated event profile, the eleventh edition focusses on topics that are especially relevant for the Chinese process industry, putting a strong emphasis on sustainability and innovation.

Founded in 1989 as a spin-off of ACHEMA to cater to the needs of China’s then developing industry, AchemAsia has since grown into a platform where the latest...

Im Focus: First real-time test of Li-Fi utilization for the industrial Internet of Things

The BMBF-funded OWICELLS project was successfully completed with a final presentation at the BMW plant in Munich. The presentation demonstrated a Li-Fi communication with a mobile robot, while the robot carried out usual production processes (welding, moving and testing parts) in a 5x5m² production cell. The robust, optical wireless transmission is based on spatial diversity; in other words, data is sent and received simultaneously by several LEDs and several photodiodes. The system can transmit data at more than 100 Mbit/s and five milliseconds latency.

Modern production technologies in the automobile industry must become more flexible in order to fulfil individual customer requirements.

Im Focus: Sharp images with flexible fibers

An international team of scientists has discovered a new way to transfer image information through multimodal fibers with almost no distortion - even if the fiber is bent. The results of the study, to which scientist from the Leibniz-Institute of Photonic Technology Jena (Leibniz IPHT) contributed, were published on 6thJune in the highly-cited journal Physical Review Letters.

Endoscopes allow doctors to see into a patient’s body like through a keyhole. Typically, the images are transmitted via a bundle of several hundreds of optical...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Munich conference on asteroid detection, tracking and defense

13.06.2018 | Event News

2nd International Baltic Earth Conference in Denmark: “The Baltic Sea region in Transition”

08.06.2018 | Event News

ISEKI_Food 2018: Conference with Holistic View of Food Production

05.06.2018 | Event News

 
Latest News

Graphene assembled film shows higher thermal conductivity than graphite film

22.06.2018 | Materials Sciences

Fast rising bedrock below West Antarctica reveals an extremely fluid Earth mantle

22.06.2018 | Earth Sciences

Zebrafish's near 360 degree UV-vision knocks stripes off Google Street View

22.06.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>