How a tiny gas implant could save you from a heart attack 

Carbon monoxide is a toxin, but could it also work as a medicine? That is the suggestion from a new study by the University of Sheffield.

Researchers tested an implant that releases tiny amounts of carbon monoxide gas into blocked arteries and found it could keep them clear. They say it could be a new way to fight heart disease and may even protect patients against another heart attack.

The implant is a tiny metal tube called a stent, similar to those inserted into tens of thousands of people in the UK every year to open up clogged arteries.

Ironic: Carbon monoxide is a toxin, but it could be a new way to fight heart disease and may even protect patients against heart attacks

But unlike most conventional stents, which are either bare metal or impregnated with a drug to prevent blockages, it has a special coating made up of molecules that gradually emit low levels of carbon monoxide gas into the blood vessel.

Each year in the UK, around 50 people die and 4,000 become ill from inhaling the odourless carbon monoxide fumes emitted by faulty boilers and gas cookers, as well as barbecues, coal fires and car exhausts.

The gas hijacks the haemoglobin, which is responsible for carrying oxygen in the blood to the major organs. Symptoms of poisoning include headaches, nausea and vomiting, vertigo, weakness and poor concentration if exposure is low. High-level exposure results in oxygen starvation and death.

But despite it being lethal in large doses, in recent years scientists have discovered the gas is made in tiny concentrations by many cells in the body and appears to have an important role.

It has, for example, been shown to reduce inflammation, widen blood vessels, increase blood flow, prevent unwanted blood clotting and suppress the activity of cells which attack transplanted organs. 

Scientists have been exploring ways to get optimal levels of the gas delivered to the organs that would benefit. The issue, of course, was that inhaling the gas meant the dose was difficult to control, and is potentially fatal.

Life-saving? The implant is a tiny metal tube called a stent, similar to those inserted into tens of thousands of people in the UK every year to open up clogged arteries

Life-saving? The implant is a tiny metal tube called a stent, similar to those inserted into tens of thousands of people in the UK every year to open up clogged arteries

But now scientists have developed compounds called CORMs (carbon monoxide releasing molecules), which are essentially compounds that bind to carbon monoxide and only release it under certain conditions.

The carbon monoxide is, therefore, released in the body only in the area where it may be beneficial, as opposed to it being breathed into the lungs where it can be toxic.

In particular for heart disease patients, the CORMs have been attached to stents — tiny collapsible ‘cages’ that are fed up via the upper thigh into the heart, where they are opened up to squash a blockage in the artery.

Although they relieve chest pain and restore blood flow to the heart, stents can also cause scar tissue damage to the lining of the artery. This triggers inflammation which can gradually narrow the artery again and dramatically reduce blood flow — a problem known as restenosis. Studies suggest one-third of patients fitted with so-called bare metal stents experience restenosis.

Rates are lower with a new generation of drug‑eluting stents (which are coated in medicine that is slowly released around the sight of the blockage), but a significant proportion still develop restenosis within months.

Stents have saved many lives and more than 70,000 people a year in England alone have them fitted. But the problem of restenosis still affects a large proportion of patients. The first sign that it has developed is severe chest pain or a heart attack.

In heart disease patients, carbon monoxide gas is thought to restrict the release of leukocytes — blood cells released in large numbers when blood vessels are diseased or injured. This rush of leukocytes can trigger swelling in tissue that lines the blood vessels

The new stent is designed to release enough of the gas to dampen down inflammation and sustain healthy blood flow, without causing any harm to patients.

As part of a project funded by the British Heart Foundation, researchers at the University of Sheffield studied the effects of CORMS on inflammation in blocked arteries in animals.

The results of the new trial, published in the journal Heart, showed releasing the molecule into the area around the blockage not only prevented inflammation — and, therefore, the risk of further blockages — but also significantly reduced the death of healthy heart cells due to lack of oxygen.

Now they are conducting further animal tests to see if coating ordinary stents with the gas-emitting molecules can prevent blockages caused by restenosis.

The results of this research are due in the next couple of years.

Commenting on the new implant, Martin Cowie, a professor of cardiology at Imperial College London, said: ‘Carbon monoxide-releasing chemicals have shown promise in animal experiments.

‘But much more work is needed to see if this concept translates into benefit for patients.’

 



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