Yvonne Keeler examines her old pacemaker

The Birmingham team were the first to do this by inventing a device with electrical wires that ran under the skin up to the heart and an external box which supplied the electrical pulse.

Yvonne Keeler was among the first people to be given a pacemaker. She carried it around hidden in her handbag.

She said: "I used to hide it then because I did not want anyone to know."

Soon the external pacemakers were replaced by a device that could be implanted by surgeons. However, the first versions could only stimulate the heart to beat at one fixed rate.

Over the years, pacemakers have become much more sophisticated. Modern versions beat slowly when the patient is at rest, and speed up during exercise.

Pacemakers originally involved complex surgery

Dr Michael Gammage, of the Queen Elizabeth Hospital, said: "The original pacemaker needed to be implanted by a surgeon and required fairly major surgery to actually put them in, whereas nowadays the pacemakers are very small, are implanted generally by physicians and under local anaesthetic in a very short procedure which causes very little discomfort for the patient who is very rapidly mobile and back home."

Some implants now even have the ability to listen to everything the heart does and create a permanent record.

The idea is that if a cardiac patient suddenly gets ill doctors can "ask" the implants what's gone wrong - just as a plane crash investigator might turn to a black box flight recorder.

The next step will be to implant pacemakers in healthy people.

Steve Mahle, of Medtronic, said: "One of the most exciting prospects for the future is the ability to provide virtually everyone with a small implantable device that would record their physiological performance."