Mechanical cardiac support and replacement are the subject of much research effort and funding. With far fewer donor hearts available for transplantation in the US than patients requiring them, there is a growing need for an artificial alternative.

The principal reason for heart transplantation and heart replacement is end-stage cardiac failure. Essentially a complex and super-efficient pump, the heart fails as a result of muscular damage. This can be caused by infection or may result from a severe heart attack in which much of the heart muscle dies.

Heart failure leads to increasing shortness of breath, retention of fluid and lack of energy. Ultimately, the person becomes bed-bound and is reliant on a powerful cocktail of drugs, which become less effective with time, to stay alive.

Cardiac replacement began as a stop-gap measure for the acute resuscitation of desperately ill patients - a bridge to transplantation - and it has now reached a stage where it can be considered as a permanent alternative to cardiac transplantation.

Since the development of the heart-lung machine in 1953, researchers have continued to improve devices used for cardiac support. The last 10 years have seen particular progress.

Pulsatile devices are now available which can be implanted into the chest. Some are approved only for use as a bridge to transplantation use, while the most advanced are fully artificial hearts designed for permanent use.

Considerable challenges remain before permanent artificial heart implants could be considered normal treatment. Infection is a major problem, affecting 50 per cent of recipients. Some bacteria and viruses are particularly adept at adhering to the surfaces of the implant within the chest, bringing with them the risk of chronic infection.

The artificial devices are also prone to throwing off clots. This can lead to strokes, when blood clots travel to the brain. They also set up an immune response in the same way as transplanted kidneys and hearts. A strong cocktail of anti-inflammatory agents and immunity-suppressing drugs is therefore needed.

The most recent research points to the development of high blood pressure in patients in receipt of artificial devices. The rate of hypertension can be as high as 70 per cent.

The next decade will see artificial hearts used as a permanent treatment for certain patients with heart failure. According to a recent review of the topic in the journal Circulation, "it is entirely possible that artificial devices will evolve into small, unobtrusive devices that will run on small, portable, long-lasting battery supplies that will not require external connection".

In the meantime, we in the Republic are fortunate to have a reasonable supply of donor hearts available to meet our requirements.

Mr Peter Houghton, who suffered a severe heart attack in 1997, has done very well with the Jarvik 2000 pump. It is attached to his heart and, linked to a belt battery via a cable running up his back into his head and out through his skull, it is circulating blood throughout his body, thus keeping him alive. His progress will be monitored carefully on both sides of the Atlantic.

In the same way that Dr Christian Barnard did the unthinkable with the first heart transplant, which has now become a routine procedure, the use of artificial heart replacement is set to become the medical norm within the next decade.