A simple injection administered to patients even 12 hours after a heart attack or stroke could cut down their crippling effects by more than half.

British-based scientists have produced an injectible antibody that reduces by more than 60 percent the physical scarring of the heart and brain after an attack.

Heart attacks and strokes are caused by blood flow being blocked by a clot, starving parts of the body further downstream of oxygen.

But most of the permanent damage is caused later - when circulation is eventually restored - and a "default of nature" which means the body's own defences attack the oxygen starved cells.

This effect, which kicks in around nine to 12 hours after the attack or stroke, causes massive inflammation and more than 80 percent of the permanent damage.

It is this that often leads to death and massive reduction in the quality of life of stroke and heart attack survivors.

Now University of Leicester researchers have come up with an injection which can effectively stop the body attacking the oxygen starved cells.

The team first uncovered a key molecule in the process responsible for the immune attack. After identifying the enzyme - called Mannan Binding Lectin-Associated Serine Protease-2 (MASP-2) - they then developed an antibody to knock it out.

The protein - code-named OMS646 - is so effective that only two injections in the first week are needed to completely neutralise MASP-2 while the heart heals itself.