There is hope for transplant patients, from technology which may keep a heart alive for 24 hours.
At the moment, a donated heart can usually only last around four hours as it is rushed to the person who needs it.
But by pumping fluid through its blood vessels, and using pulses of oxygen which mimic a heartbeat, scientists have been able to keep pigs' hearts for 24 hours.
They say the technology could be available for human hearts in a year.
The breakthrough, using a device which fits into a small suitcase, could cut waiting lists for transplants.
There is hope for transplant patients, from technology which may keep a heart alive for 24 hours
The latest figures show there are 328 people in the UK on the waiting list for a heart, including 39 children.
Many are forced to wait until it is too late, and figures suggest around three-quarters of donated hearts cannot be used in the UK.
Dr Rafael Veraza, from the University of Texas Health at San Antonio, presented the findings on pig hearts, which still appeared to be oxygenated with viable cells after 24 hours, at the annual meeting of the American Association for the Advancement of Science in Seattle.
He said: 'The first heart was transported more than 50 years ago by putting it on ice, and decades later it is done much the same way.
'But being able to keep a heart viable for 24 hours means you could transport it almost anywhere in the world, and this could save many lives.'
While the main reason that hearts are not taken from UK donors is because they are unsuitable, experts say the time between removing an organ and transplanting it is 'crucial'.
A heart transplant is an operation to replace a damaged or failing heart with a healthy heart from a donor who's recently died.
It may be recommended when a person's life is at risk because their heart no longer works effectively.
Why heart transplants are carried out
A heart transplant may be considered if you have severe heart failure and medical treatments are not helping.
Conditions that may eventually require a heart transplant include:coronary heart disease – a build-up of fatty substances in the arteries supplying the heart, which block or interrupt blood flow to the heart cardiomyopathy – where the walls of the heart have become stretched, thickened or stiff congenital heart disease – birth defects that affect the normal workings of the heart
If your doctor thinks you might benefit from a heart transplant, you'll need to have an in-depth assessment to check whether you're healthy enough to have one before being placed on a waiting list.
What happens during a heart transplant?
A heart transplant needs to be carried out as soon as possible after a donor heart becomes available.
The procedure is performed under general anaesthetic, where you're asleep.
While it's carried out, a heart-lung bypass machine will be used to keep your blood circulating with oxygen-rich blood.
A cut is made in the middle of the chest. Your own heart is then removed, and the donor heart is connected to the main arteries and veins. The new heart should then begin beating normally.
Outlook for heart transplants
Most people can eventually return to their normal activities after a heart transplant and experience a significant improvement in their symptoms for many years.
But it's a major operation and some of the complications can be life threatening.
Overall:80 to 90 in every 100 people will live at least a year 70 to 75 in every 100 people will live at least 5 years 50 in every 100 people will live at least 10 years
Some people have survived for more than 25 years after a heart transplant.
The average person waits almost three years - 1,085 days - for a heart transplant, with NHS Blood and Transplant reporting in 2018 that one man, 45-year-old Gareth Evans from Stockport, had been on the waiting list for nine years.
The key to preserving hearts for a full day is to mimic the conditions in the human body as much as possible.sonos sonos One (Gen 2) - Voice Controlled Smart