Scientists reveal the mystery of sudden cardiac death

Jul 05, 2010

(PhysOrg.com) -- Scientists at The University of Manchester have solved a mystery connected with why people die from sudden cardiac arrest during sleep - potentially saving thousands of lives.

The pioneering research, using detailed computer models, could help save lives through preventative treatment of those most at risk from a form of called sick sinus syndrome.

This occurs when the activity of the heart’s pacemaker, the sinoatrial node, is impaired. Up to now, no-one has been able to work out why this happens.

But groundbreaking research by Professor Henggui Zhang at The University of Manchester shows how and activity of the nervous system can combine to seriously disrupt the heart’s normal rhythm.

This research means it would be possible to identify those most at risk of suffering sudden cardiac death, which can affect people of any age but particularly the healthy elderly and well-trained athletes.

It could then be possible to control the risk by using drugs or a pacemaker.

Sudden cardiac death occurs after an abrupt loss of consciousness within one hour of the onset of acute symptoms. This often happens during the night as heart rate slows dramatically at night times.

The form of sick sinus syndrome investigated is not connected with structural heart disease, but with that alter a protein called SCN5A that is involved in generation of electrical activity in the heart. Problems can occur for people of any age who possess this genetic abnormality.

Every year, hundreds of thousands of people around the world die from - many of them young and fit. It is estimated that about 30% of sudden cardiac deaths occur at nighttime.

The research has been made possible by developing models of cardiac electrical activity over 13 years and has now been published in the leading journal .

Using experimental measurements from the sinoatrial node together with detailed computer models, Professor Zhang, from the University’s School of Physics and Astronomy, has been able to simulate the electrical activity in cardiac tissue.

Their research, carried out with scientists from The University of Bristol, found that there is a chemical present in the nervous system which, in healthy individuals, acts to slow the heart rate.

But in sick sinus syndrome patients, it may entirely prevent electrical activity spreading across the heart, thereby compromising cardiac function leading to heart arrest.

These effects are associated with gene mutations which can be detected by tests.

Professor Zhang said: “Previously, we did not know why some people with sick sinus syndrome would die suddenly, but now we do know why risk can increase at night during sleep. Our findings may be an important step towards ways of preventing this.

“We may have to reduce the influence of a certain form of nerve activity on the hearts of sick sinus patients. This could be via drugs or pacemaker devices.

“The computer models we have made have created the effects of the chemicals on the heart and we then tested this experimentally with results that supported the computer predictions.

“Our laboratory experiments have been building up computer models to analyse the heart for the past 13 years. We are now in a position to test other forms of sick sinus syndrome so we can hopefully identify common features that can lead us to more effective treatments”

Professor Jules Hancox from the University of Bristol, who collaborated on the study, said: “The insights into sick sinus syndrome from this study are potentially of great importance.

“If other forms of sick sinus syndrome that involve mutations to different proteins in the heart are affected by nerve activity in the same way, this may identify a common target to reduce or eliminate risk of dangerous arrhythmia”.

Explore further: Scientists 1 step closer to cell therapy for multiple sclerosis patients

More information: Mechanistic Links Between Na+ Channel (SCN5A) Mutations and Impaired Cardiac Pacemaking in Sick Sinus Syndrome, Circulation Research.

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User comments : 6

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Oxensraiser?
1 / 5 (5) Jul 05, 2010
Seriously? Are we now trying to cure dying peacefully in your sleep? Holy shit most of us will die in a nursing home strapped to a bed covered in shit, out of our minds, and getting molested by Raul the orderly. Only thing you could save yourself from here is a peaceful death. We are all going to die despite what Ray Kurtzweil keeps trying to tell us. Might as well be peaceful.
Oxensraiser?
1 / 5 (4) Jul 05, 2010
By-the-by about 2/3rds of you reading this will be dying of cancer of some form or another. Makes a heart attack sound pretty sweet eh?
Skepticus
1 / 5 (4) Jul 05, 2010
Flushed with advances in medical sciences, The medicos have convinced themselves that their whole purpose in life and nothing else is but the goal of snatching everyone and all out of the jaws of Death. Who cares whether the next saved is another Einstein, Hitler or just another oxygen waster? The society's landscape is being littered and burdened with forced survivors and their supporting costs, those that natural Darwinian selection should have weeded out. How many of those millions that "survived" have contributed concretely to the society, except providing the selfish emotional comfort to their kin, in comparison to the benefit to the society as a whole? This is how a civilization rise and fall. Instead of cutting out the diseased and dead wood, we endeavor ourselves to keep the whole mess afloat and growing by all means, until one day it will all came crashing down on our heads, all in the name of "humane, compassion"...I would say: "lack of vision for the species"
slaveunit
5 / 5 (6) Jul 05, 2010
wow the negativity and stupidity of the comments so far is amazing in case you didnt read the article it said that many of those who died were young people. secondly broad and basic research into a wide variety of problems is essential many discoveries in unrelated field have come from research in areas people thought 'useless' and lastly as we have no proof there is anything after death and as the ability to help the 'weak' or the sick has led to many advances that helped the 'strong' (when they got sick or injured) i suggest skepticus shoves his nazi ideals somewhere the sun doesnt shine. Fact is all the research into helping the 'weak' will eventually lead to clinical immortality which will help the 'strong' too.
MarkyMark
not rated yet Jul 06, 2010
This is a good thing people!!!

To first poster the fact that some care homes providec poor care is a social and political problem not a medical one.

To the second one Grow up a bit Dawin was not always right and tho i agree we are still evolving i think that we have risen a bit from the hunter gatherer society where your point would be true.
tkjtkj
not rated yet Jul 06, 2010
I think it interesting that they make no mention at all of another powerful element in the story of night-time death:
ACTH. This hormone, released in a short burst in the early morning hours, is a very powerful hypertensive agent. In fact, it is used by researchers to induce hypertension in test animals.
It is not only cardiac deaths that happen in early mornings, but also stroke.. and hypertension is far better at explaining both cardiac arrest and stroke..
Further, if they've discovered a 'new substance' that slows the heart (the mechanism for which they *assume* to be via the SA node) then please tell us what it is.

I think this research is in an early phase... let us hope so.