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 Monday, 20 January, 2003, 00:42 GMT
Deadly gas 'cuts heart risk'
Blood vessels
Blood vessels can be damaged in angioplasty
Exposure to low levels of carbon monoxide could reduce the risk of new episodes of heart disease for at-risk patients, research suggests.

Carbon monoxide (CO) is usually thought of as poisonous, but scientists discovered it could have a beneficial effect.

US researchers carried out tests on rats which suggested a simple one-hour treatment of CO can reduce long-term damage.

The study looked at treatments to repair damage to two of the body's main arteries.

These findings demonstrate a significant protective role for CO

Dr Leo Otterbein, University of Pittsburgh
The looked at aortic grafts, needed when the aorta - the major vessel through which blood leaves the heart - is damaged.

They also examined angioplasty, the treatment for blockages in the carotid artery, which supplies blood to the head.

In angioplasty, a small balloon is inserted into an artery to unblock it.

Both treatments themselves carry a risk of arteriosclerosis, the blocking and narrowing of the arteries.

Artery damage

Some of the rats who had aortic grafts were exposed to 250 parts per million (PPM) of carbon monoxide (CO) immediately after the operation, and for the further 56 days of the study.

In those rats which were not exposed to CO, signs of arteriosclerosis developed after 20 to 30 days, and were significant by 50 to 60 days.

In those which had, indications of arteriosclerosis were reduced by almost two thirds.

The researchers, from the University of Pittsburgh, damaged the carotid artery of a separate group of rats, like that which could be caused by angioplasty.

Again, some were exposed to CO - 250ppm for an hour prior to the injury - and some were not. All breathed normal air for two weeks after the procedure.

Those which were exposed to CO had a 74% reduction in signs of arteriosclerosis than those which were not, when checked two weeks later.


A naturally occurring CO-producing enzyme in the body is already known to protect against blood vessels being injured after transplantation.

But it had not been known if direct exposure to CO could have the same effect.

The researchers suggest CO might have a protective effect because it can blocks the process involved in forming arteriosclerotic lesions.

The rats in the study showed no negative effects from CO exposure. Further tests are underway on pigs.

Dr Leo Otterbein of the University of Pittsburgh's division of pulmonary and critical care medicine, who led the research, said: "These findings demonstrate a significant protective role for CO in vascular injury and support its use as a therapeutic agent."

His co-author, general surgeon Dr Brian Zuckerman, added: "Currently the best available treatment of clogged arteries is through angioplasty and a stent or via bypass surgery.

"But these have their limitations and a significant failure rate. If you could pre-treat patients with CO it might result in a better long term outcome."

Belinda Linden, head of medical information at the British Heart Foundation, described the research as interesting.

She said: "It is important to look at the many ways there are to control the process of damage to the artery lining.

"However, many research articles have reflected concern about the potential damaging effect of exposure to low levels of carbon monoxide.

"Until there is conclusive evidence from clinical trials we need to be sure that the public are aware of the detrimental effect of smoking and pollution on patients with coronary heart disease and chronic lung disorders."

The research is published in the online version of the journal Nature Medicine.

See also:

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