The treatment is taking place in Edinburgh

Doctors believe the technique could help the 15% of patients who cannot currently be treated.

Heart disease is Scotland's biggest killer, with thousands of people being treated for the condition every year.

Techniques like bypass surgery have improved recently, but one patient in every seven cannot be treated because their blood vessels are too thin or too badly blocked.

Now researchers think they have found a way to prompt the body into repairing itself.

Growth factor

A patient at Edinburgh Royal Infirmary has had a human gene which stimulates growth injected into his heart.

Heart experts have harnessed the power of gene therapy for his treatment.

Consultant cardiologist Dr Neil Uren said they were using a natural process.

What we are trying to do is to stimulate more and more blood vessels to grow Dr Neil Uren

He said: "We are trying to stimulate the natural process of collateral growth.

"Many patients with quite bad cardiac disease do develop their own small blood vessels called collaterals.

"These tend to reduce the amount of problems that the muscle has, so they reduce the amount of angina.

"What we are trying to do is to stimulate more and more blood vessels to grow."

Cold virus

The big challenge for scientists has been how to get the growth factor into the right cells in the body.

Their solution is allowing the gene to hitch a ride on the back of a deactivated common cold virus.

Dr Uren said: "The virus has been modified so that it doesn't cause any infection.

The patient is benefiting from new therapy

"When it is injected into the heart through the coronary circulation it delivers the gene to the cells of the heart - the muscle cells, the blood vessel cells.

"The gene goes into the inside of the cell and produces protein. That protein is then released into the heart and stimulates the new blood vessels to grow."

The results of the trial will not be known for six months.

If it proves a success the treatment could become available more widely within three years.

Campbell Chalmers, of Chest Heart and Stroke Scotland, described it as an important development.