A patch of tissue smaller than a postage stamp can mend broken hearts, research claims

Once injected into an ailing heart, shape-memory technology causes it to unfold into an expanding "bandage". Over time the scaffold breaks down, leaving behind the new growing tissue.

Tests have shown that injecting the patch into rats that have suffered heart attacks improves the animals' cardiac function.

Damaged ventricles pumped out more blood than they did without the patch.

Lead researcher Professor Milica Radisic, from the University of Toronto in Canada, said: "It can't restore the heart back to full health but if it could be done in a human we think it would significantly improve quality of life."

An implant requiring open heart surgery is not going to be widely available to patients, Prof. Radisic explained.

The alternative, an injected patch, was developed over a period of nearly three years.

After a large number of failures, the scientists came up with a design based on physical rather than chemical shape-memory properties.

This meant the unfolding process did not require additional injections and would not be affected by conditions within the body.

Injecting the patch into rats and pigs confirmed the heart cells survived the procedure well, the researchers reported in the journal Nature Materials.

Miles Montgomery, a PhD student in Prof Radisic's laboratory, said: "When we saw that the lab-grown cardiac tissue was functional and not affected by the injection process, that was very exciting.

"Heart cells are extremely sensitive, so if we can do it with them, we can likely do it with other tissues as well."

The team is investigating whether the patch can be improved or used to repair other organs such as the liver.

Prof Radisic, who points out the invention is still a long way from being tested on patients, added: "You could customise this platform, adding growth factors or other drugs that would encourage tissue regeneration."