If you've ever been chucked by a boyfriend or girlfriend, you'll have been consoled with the expression 'no-one ever died of a broken heart'. Yet a broken heart is one of the UK's biggest killers, accounting for 120,000 deaths - 20% of total mortality - every year. And although there have been major advances in drug treatments, pacemakers and bypass surgery, a transplant from a human donor has been the only way forward for someone with a seriously dodgy ticker. But things are changing in the cardiac ward. Alongside an artificial heart from America - designed to last a lifetime rather than just until a human donor can be found - there is talk of putting pig hearts into people and of new hearts being grown in the lab.
THE CHALLENGE: Despite its hefty romantic burden, the heart is a simple organ compared to the liver or kidneys. It's a muscular pump a little larger than your clenched fist, with four chambers arranged in two sets (a smaller atrium atop a larger ventricle on each side) and a series of valves to control the flow of blood. Deoxygenated blood enters the right side and is squeezed out into the pulmonary artery to the lungs, picking up oxygen before returning to the left side of the heart to be squirted out round the rest of the body.
So what's the big deal? In a word, stamina. The average human heart beats 2.5 billion times in a lifetime, pumping about a million litres of blood. Every time the heart muscle contracts - about 72 times a minute - it does so with all its strength. But your heart can't stop for a rest, or it's game over after about four minutes.
THE SOLUTION: The use of animal organs in human patients has many transplant surgeons anticipating an endless supply of replacement parts. Pigs are the great pink hope of this technique - called xenotransplantation - because of their physiological similarity to humans. But problems with rejection of the foreign heart by the patient's immune system will keep xenotransplants in the realm of theory for some years. And though scientists hope that the discovery of a fish that can regrow its heart tissue when damaged might lead to whole-organ culture, this too is a long way off.
Artificial hearts made of PVC and rubber appeared in the late '50s but it took more than 40 years for the first full replacement heart - the Abiocor - to become available. The grapefruit-sized Abiocor is a twin-bodied electric pump, battery-powered through an inductive system that avoids the need for wires penetrating the chest cavity. Clinical trials are under way, but becoming the bionic man or woman is not without its downside - two pioneers have died from stroke. Even healthy recipients will have to get used to a new soundtrack. Electric hearts don't beat, they hum.