Artificial arteries designed like gun barrels could revolutionise heart bypass surgery and save the NHS millions, researchers claim.

Scientists are working on synthetic grafts with a twist and internal "rifling" - helical grooves - that causes blood to spiral through them in much the same way a bullet fired from a gun is made to spin.

The smoother flow is expected to reduce wear and tear at the junction points where the graft is attached, thereby increasing its life span.

By-pass surgery involves patching in a healthy blood vessel to route blood around a length of artery narrowed or clogged by disease.

Coronary artery bypass operations to supply heart muscle with sufficient blood are the most common form of heart surgery in England, with 20,000 performed each year.

However, the grafts have a limited lifespan of between eight and 15 years.

Dr Amir Keshmiri, senior lecturer in fluid dynamics at Manchester Metropolitan University, who is leading the 18-month £200,000 project, said: "The impact could be huge. If it works, it will improve the fluid dynamics of the blood and delay the failure of the graft. It could save millions of pounds and a lot of time for health services.

"In a lot of cases, the graft junction fails and blocks the blood flow. We want to be able to avoid these hotspots by optimising the graft design by inducing a spiral flow.

"If you can get the blood to swirl before joining the junction it will help the fluid dynamics through accelerating the blood to improve the life of the graft. The body is familiar with the spiral flow and encourages it in different parts of the body, so we can apply the same idea to the grafts."

Spiral flow occurs naturally in the arterial system, supported by the rotational pumping of the heart and the curved geometry of blood vessels.

Dr Keshmiri said the new technique could be expanded to include grafts used in haemodialysis treatment for kidney patients.

The research is modelled on earlier work in the nuclear industry, where spirally flowing coolant is used to enhance the heat transfer of reactor cooling rods.

The grafts will be made from a plastic-like polymer material called Dacron.