'Temporary tube' keeps heart unblocked

The stent could reduce the need for further operations

A biodegradeable tube inserted into one of the arteries supplying the heart could save some patients from further operations.

Thousands of patients each year in the UK have stainless steel wire mesh "stents" pushed into clogged blood vessels to physically hold them open and maintain blood flow.

If they have found a polymer that seems to work, that would be exciting

Dr David Smith, consultant cardiologist

This is normally done after the blood vessel has been "stretched" by a balloon inflated inside it - a procedure called angioplasty.

But this stretching can cause damage, and the body's efforts to heal itself, frustrated by the presence of the stent, can lead to the vessel becoming re-clogged.

This may leave the patient needing another procedure to open up the blood vessel.

Researchers have been looking for materials which are strong enough to perform the role of a stent, but which do not provoke the same level of response from the body.

Performed better

Although biodegradeable polymers were tried out on dogs in the late 1980s, up until now they generally performed worse than stainless steel.

Now a Japanese team, based at the Shiga Medical Centre, claims to have found a polymer that works well, and 15 patients have received them.

The rate of re-clogging, or restenosis, they report, was less than in patients given metal stents.

By the time the polymer disappears, the vessel should be fixed at the correct width, and will not narrow again.

Dr Hideo Tamai, who led the research, said: "There are many long term safety concerns associated with metal stents.

Larger study planned

"Those that remain in place for long periods may become obstacles to additional treatments, such as repeat angioplasty or bypass grafting."

A larger study in the US is now planned.

Dr David Smith, a consultant cardiologist from the Royal Devon and Exeter Hospital, and hononary secretary of the British Cardiovascular Intervention Society, said: "The idea of stents mades from biodegradeable polymers has been around for a while, but the problem is finding an appropriate polymer.

"Up until now, the polymers have always caused a greater response than metal stents.

"If they have found a polymer that seems to work, that would be exciting."

The research was reported in the American journal Circulation.

Some experts hope that a biodegradeable stent could be engineered to, as it disintegrates, release drugs designed to prevent re-clogging.