A pair of "magic trousers" designed to squeeze blood from the legs to congested chest veins is being clinically tested by 300 patients at an NHS heart centre.

The invention has cured a number of angina cases and allowed chronically ill sufferers from other related conditions to walk again, according to doctors at the Royal Infirmary in Hull. The apparatus inflates and vibrates to force blood up into the body from its wearer's feet, legs and thighs.

"It squeezes them like a tube of toothpaste," said Amal Louis, clinical lecturer in cardiology at the Royal Infirmary. "The blood bypasses blockages and makes its way through other, narrow blood vessels round the heart muscle. It's really like having a natural heart bypass."

Pioneered in the US, the trousers have pressure pads round the calf, thighs and buttocks, which inflate at intervals, replicating the patient's heart rhythm.

"The system has cured some people of angina and helped other people relieve the symptoms," said Dr Louis.

The £5,000 trousers have also proved cost-effective in the first stage of the trials, avoiding repeated referrals and some expensive medication. Known clinically as enhanced external counter pulsation, treatment consists of wearing the trousers in bed for an hour a day over a period of seven weeks.

Zipped into his experimental pair yesterday John Gell, 60, said that the effect of the trousers was "unbelievable". An angina victim for the past year, he said: "In the last 10 days I have only had three angina attacks normally I would have had many more.

"Living in Withernsea [East Yorkshire], I had to organise the distance I could walk by the number of seats on the mile walk into town. Now I can make it all the way there without stopping, and I'm only on my fourth week of treatment."