Researchers find new source of dangerous electrical instability in the heart

Researchers find new source of dangerous electrical instability in the heart
This image produced by Richard Gray and Pras Pathmanathan at the FDA shows simulated fibrillation in a rabbit heart. Credit: FDA

Sudden cardiac death resulting from fibrillation - erratic heartbeat due to electrical instability - is one of the leading causes of death in the United States. Now, researchers have discovered a fundamentally new source of that electrical instability, a development that could potentially lead to new methods for predicting and preventing life-threatening cardiac fibrillation.

A steady heartbeat is maintained by electrical signals that originate deep within the and travel through the muscular organ in regular waves that stimulate the coordinated contraction of muscle fibers. But when those waves are interrupted by blockages in electrical conduction - such as scar tissue from a heart attack - the signals can be disrupted, creating chaotic spiral-shaped electrical waves that interfere with one another. The resulting electrical turbulence causes the heart to beat ineffectively, quickly leading to death.

Scientists have known that instabilities at the cellular level, especially variation in the duration of each electrical signal - known as an action potential - are of primary importance in creating chaotic . By analyzing in the hearts of an animal model, researchers from the Georgia Institute of Technology and the U.S. Food and Drug Administration have found an additional factor - the varying amplitude of the action potential - that may also cause dangerous electrical turbulence within the heart.

The research, supported by the National Science Foundation, was reported April 20 in the journal Physical Review Letters.

"Mathematically, we can now understand some of these life-threatening instabilities and how they develop in the heart," said Flavio Fenton, a professor in Georgia Tech's School of Physics. "We have proposed a new mechanism that explains when fibrillation will occur, and we have a theory that can predict, depending on physiological parameters, when this will happen."

The voltage signal that governs the electrically-driven heartbeat is mapped by doctors from the body surface using electrocardiogram technology, which is characterized by five main segments (P-QRS-T), each representing different activations in the heart. T waves occur at the end of each heartbeat, and indicate the back portion of each wave. Researchers have known that abnormalities in the T wave can signal an increased risk of a potentially life-threatening heart rhythm.

Fenton and his collaborators studied the cellular action potential amplitude, which is controlled by sodium ion channels that are part of the heart's natural regulatory system. Sodium ions flowing into the cells boost the concentration of cations - which carry a positive charge - leading to a phenomena known as depolarization, in which the action potential of the cell rises above its resting level. The sodium channels then close at the peak of the action potential.

While variations in the duration of the action potential indicate problems with the heart's electrical system, the researchers have now associated dynamic variations in the amplitude of the action potential with conduction block and the onset of fibrillation.

"We have shown for the first time that a fundamentally different instability related to amplitude may underlie or additionally affect the risk of cardiac instabilities leading to fibrillation," said Richard Gray, one of the study's co-authors and a biomedical engineer in the Office of Science and Engineering Laboratories in the U.S. Food and Drug Administration.

The mathematical analysis provides a simple explanation.

"You can have one wave with a long amplitude followed by one wave with a short amplitude, and if the short one becomes too short, the next wave will not be able to propagate," said Diana Chen, a Georgia Tech graduate student and first author of the study. "The waves going through the heart have to move together to maintain an effective heartbeat. If one of them breaks, the first wave can collide with the next wave, initiating the spiral waves."

If similar results are found in human hearts, this new understanding of how electrical turbulence forms could allow doctors to better predict who would be at risk of fibrillation. The information might also lead to the development of new drugs for preventing or treating the condition.

"One next scientific step would be to investigate pharmaceuticals that would reduce or eliminate the cellular amplitude instability," said Gray. "At the present time, most pharmaceutical approaches are focused on the action potential duration."

The critical role of electrical waves in governing the heart's activity allows physics - and mathematics - to be used for understanding what is happening in this most critical organ, Fenton said.

"We have derived a mathematical explanation for how this happens, why it is dangerous and how it initiates an arrhythmia," he explained. "We now have a mechanism that provides a better understanding of how these electrical disturbances originate. It's only when you have these changes in wave that the signals cannot propagate properly."


Explore further

Cause of killer cardiac disease identified by new method

More information: Diandian Diana Chen et al, Mechanism for Amplitude Alternans in Electrocardiograms and the Initiation of Spatiotemporal Chaos, Physical Review Letters (2017). DOI: 10.1103/PhysRevLett.118.168101
Journal information: Physical Review Letters

Citation: Researchers find new source of dangerous electrical instability in the heart (2017, May 3) retrieved 16 October 2019 from https://phys.org/news/2017-05-source-dangerous-electrical-instability-heart.html
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User comments

May 03, 2017
One of the most common triggers for atrial fibrillation is MSG. Some people are much more sensitive than others. Emergency room medics are sometimes trained to recognise this, and administer cream of tartar as an antidote. How do I know this? Guess.

May 03, 2017
@solon
One of the most common triggers for atrial fibrillation is MSG
links/references?

i think you're thinking of palpitation or tachycardia, not AFib, which is different

i know that stimulants, sugars, MSG and etc can be causes of tachycardia and are considered a huge problem when people react because they feel something different in their chest, but i would prefer to see a study showing that MSG is a specific trigger for AFib as this is not something i've read any time, though there was historical argument along with caffeine - see also: http://www.online...fulltext
How do I know this? Guess
likely you're basing this on your own personal experience and what you believe you understood from the ER visit

May 03, 2017
PS @Solon
the most common triggers are: alcohol, sleep deprivation, and emotional stress

however, Stimulants such as caffeine or exercise may also precipitate AFib events

if you're interested in reading up a little, here is a link (2006 Guidelines for the Management of patients with AFib) : http://ac.els-cdn...b5a1473d

May 03, 2017
"i think you're thinking of palpitation or tachycardia, not AFib, which is different"

Yes, I was tachycardia, but my understanding from the ER tech is that AFib was the next stage, and that deaths from AFib were known to occur and could be linked in some cases with s severe case of Chinese restaurant syndrome. No processed food at all for 3 years now, and many chronic ailments have cleared up too, bad asthma completely gone, random fibromyalgia-like episodes, high BP, vision irregularities and complete loss of vision on one occasion, ugly scalp flaking, deep facial lines and weird curly stiff hairs growing from eyebrows and ears, aching muscles and popping joints. ALL gone. Feeling 10 years younger.

May 04, 2017
Yes, I was tachycardia, but my understanding from the ER tech is that AFib was the next stage
@Solon
it can be, but it doesn't mean it is definitely
and that deaths from AFib were known to occur and could be linked in some cases with s severe case of Chinese restaurant syndrome
ok, from the literature: MSG can be reactive if you're allergic, or it can also be a neurotoxic product causing Cerebral Ischemia (Ischemic Brain Damage) if perhaps you're injecting this directly into your head, but there is no strong evidence that MSG is a cause of your chinese rest. syndrome

the reactions you're having to MSG are due to an allergy or sensitivity to glutamate (or sugars)
there are indications (tentative) that MSG leads to the development of significant inflammation, central obesity, and type 2 diabetes, but until said study is validated i would not state this is factual
http://www.scienc...07001400

2Bcont'd

May 04, 2017
@Solon cont'd
MSG is used quite a bit in various ways in our food chain, especially as a preservative and additive for processed foods - if you've stopped using it, then great for you (see above)

here is another book that might be helpful, should you want to think it over: https://www.amazo...U#navbar

similar to you, i've stopped eating processed foods
using the above diet with modifications (like using sucralose because the sugar taste is there but the body can't metabolise it) i've managed to drop my A1C to normal range from a diagnosis of diabetic (type 2)

i would recommend talking to a good DR first though, especially if they're one who will attempt to use natural means before pharmaceutical ones, like my DR

all in all, AFib is pretty common, and though prolonged tachycardia is potentially problematic and *may* lead to AFib, don't let it stress you out too much until the DR says it's time to worry

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