The Tin Man in The Wizard of Oz yearned for one, but a mechanical heart has also been the dream of surgeons for many years. With the increasing burden of heart disease and a chronic shortage of donor organs, it is cheering to think that science could design a prosthetic organ capable of reproducing the essential functions of the body’s main pump.

The latest device is an exciting fusion of titanium, animal tissue and aeronautical technology, which has proved capable of adapting its rhythm to the body’s changing demands, while avoiding the risk of rejection and blood clots associated with other devices in trials on calves and sheep. But we are a long way from cheap, spare parts that could make us as good as new.

Existing pneumatic hearts are intended only to be used as a stop-gap during transplant operations or while patients await a scarce donor organ. For most patients there is still nothing. Yet the number of deceased heart transplants in the UK fell by 18 per cent to only 127 operations last year.

A more long-standing problem for artificial hearts is powering the beat without restricting a patient’s mobility. Peter Houghton, from Birmingham, survived more than seven years after being the first man in the world to be fitted with the Jarvik permanent artificial heart in June 2000. But in his case the pump was assisting, rather than replacing his own heart, and needed to be recharged every four hours.

Patients with the latest fully implantable model, Abicor, can expect to live up to five months after surgery - twice as long as they could have expected without it.

With increased understanding of the heart and continuing improvements in engineering, computer science, electronics, battery technology and fuel cells, a practical artificial heart may become a reality.

A more immediate way to save lives, however, would be for more people to carry a donor card.

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