Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Engineered heart tissue offers insights into irregular heartbeats, defibrillator failure

07.02.2006


Engineers who have induced heart cells in culture to mimic the properties of the heart have used the tissue to gain new insight into the mechanisms that spawn irregular heart rhythms. Studies of the engineered cardiac tissue revealed that while electric shocks such as those delivered by defibrillators usually stopped aberrant waves, in some cases they cause them to accelerate and multiply.

The Duke University and Johns Hopkins University team, led by Nenad Bursac of Duke’s Pratt School of Engineering, reported its findings in the Feb. 1, 2006, Cardiovascular Research. Bursac and study co-author Leslie Tung conducted the experiments at Johns Hopkins before Bursac joined the Duke faculty. The work was supported by the National Institutes of Health and the American Heart Association.

In their experiments, the researchers sought to understand the characteristics of ventricular tachycardia -- a condition characterized by abnormally fast beating of the heart’s pumping chambers. In particular, they sought to understand how such arrhythmia may lead to ventricular fibrillation, in which the heart’s electrical activity becomes disordered, causing the ventricles to flutter rather than synchronously beat. As a result, pumping of the blood is inefficient, and death can result within minutes.



"Ventricular tachycardia and fibrillation are the leading causes of sudden death in the developed world," Bursac said. "Yet, in humans and animals the anatomy is so complex that mechanisms of such arrhythmias are difficult to dissect systematically."

In their study, Bursac and his colleagues created a simpler version of cardiac tissue using cells from the heart ventricles of neonatal rats. They transferred the cells into culture dishes on which they had stamped precise patterns of proteins known to support heart tissue growth. The proteins caused the cells to orient themselves, interconnect and grow in a manner that mimics normal heart tissue, Bursac explained.

The team then induced electrical activity in these engineered tissues as would occur in ventricular tachycardia and attempted to halt it with pace-setting pulses.

"In the beginning, there is a single rotating wave -- the ’culture dish’ analog of ventricular tachycardia," Bursac said. "After a short period, we applied trains of pulses in an attempt to terminate this wave."

The pulses successfully halted the wave 80 percent of the time, they reported. In the remaining cases, however, the pulses converted the single wave into multiple waves that continued to activate the cardiac cells at an accelerated rate.

"In other words, instead of terminating it, the pacing actually perpetuated and worsened the initial condition in about 20 percent of the cases," Bursac said. "That percentage approximates the frequency with which this is thought to occur in patients with implanted defibrillators."

The researchers’ analysis revealed a possible explanation for the two responses. They found significant differences in propagation of electrical activity through the engineered tissues between those that responded to pace-setting shocks by halting their aberrant rhythm, and those that responded by accelerating their rhythm.

Should such characteristic patterns hold in patients, physicians could potentially use them to identify those people for whom defibrillators are more likely to worsen abnormal heart rate, Bursac said.

So-called implantable cardioverter defibrillators (ICD) monitor the timing of heartbeats and can deliver small or large shocks to correct arrhythmias. Such devices have become increasingly common for patients who have experienced arrhythmias and are therefore at increased risk for future rhythm abnormalities, Bursac said.

In patients with implanted defibrillators, the devices often attempt to terminate ventricular tachycardia by delivering electrical pulses to a single site at a rate slightly higher than the rate of tachycardia. Such pacing usually overrides the abnormal heart waves to restore a normal rhythm, Bursac said.

In 5 to 20 percent of cases, however, the anti-tachycardia pacing can result in an accelerated heart rate or induction of ventricular fibrillation.

When pacing pulses accelerate tachycardia, current ICD devices usually deliver a strong and painful shock, he said. Further study of the engineered tissues might lead to more reliable and less painful strategies for halting arrhythmias, Bursac said. For example, preliminary observations suggested that pacing the engineered tissue at rates slightly below the rate of tachycardia may still slow down the accelerated rhythm.

The results in general demonstrated the promising utility of engineered tissue in the laboratory for studying the complex electrophysiological properties of the heart in both health and disease, they said.

"Implanted defibrillators can protect many patients, but sometimes the devices instead accelerate rapid heart beats," Bursac said. "The mechanism responsible for this had remained unclear. We’ve now been able to show in these cardiac cell cultures that electric pulses sometimes break rotating waves rather than block them."

Engineered cardiac tissues also might prove a useful testing ground for potential drug and gene therapies that could restore normal heart rhythms, he added.

"Bursac and Tung have presented a convincing mechanistic explanation for a clinically important phenomenon that they reproduced in a Petri dish," Igor Efimov and Crystal Ripplinger, both of Washington University in St. Louis, wrote in an editorial. "Their study showed that, as in clinical therapy, anti-tachycardia pacing is highly successful; yet in some cases, it may result in acceleration of reentrant arrhythmia instead of its termination."

Kendall Morgan | EurekAlert!
Further information:
http://www.duke.edu

More articles from Health and Medicine:

nachricht NTU scientists build new ultrasound device using 3-D printing technology
07.12.2016 | Nanyang Technological University

nachricht How to turn white fat brown
07.12.2016 | University of Pennsylvania School of Medicine

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: Significantly more productivity in USP lasers

In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.

Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...

Im Focus: Shape matters when light meets atom

Mapping the interaction of a single atom with a single photon may inform design of quantum devices

Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

Im Focus: MADMAX: Max Planck Institute for Physics takes up axion research

The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.

The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

NTU scientists build new ultrasound device using 3-D printing technology

07.12.2016 | Health and Medicine

The balancing act: An enzyme that links endocytosis to membrane recycling

07.12.2016 | Life Sciences

How to turn white fat brown

07.12.2016 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>