A new way of keeping hearts alive but 鈥渁sleep鈥� in a box outside the body for a day or more could bring an end to people dying on the heart transplant waiting list.
The system was tested on the first patient in August, albeit with the heart kept in this state for just 3 hours, New 杏吧原创 can reveal. It will be tested on another five people for this same time and, if all goes well, the time will be gradually raised to 24 hours. at Lund University in Sweden, who developed the technique, says it could potentially be used for up to several days.
Any ability to keep hearts alive for longer outside the body boosts the number available for transplants. There is a shortage of all organs for transplant, with over a thousand people in the UK dying every year for want of one.
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In England, the shortfall may be eased by the forthcoming switch to an 鈥渙pt-out鈥� system of organ donation, announced last week. But it won鈥檛 disappear, partly because only a fraction of people who die in hospital have organs suitable for donation, and families will still be able to override their relatives鈥� wishes.
With hearts, a particular problem is distance between the donor and the patient, because hearts can only be kept alive outside the body for a few hours before weakening. 鈥淣ow we say no to a lot of good hearts,鈥� says Steen. 鈥淲ith the new way, we can take hearts from theoretically the whole world. We can get the perfect fit for each patient.鈥�
Heart in a box
The usual way to transport hearts is called cold ischaemic storage, and involves the organs being maintained at 4掳C, without an oxygen supply. But the longer the heart is kept like this, the worse it will work when transplanted. The upper limit is about 4 hours.
One recent advance is a device that keeps the heart . Manufacturer , based in Andover, Massachusetts, says hearts are successfully being kept on the machine for 7 to 12 hours. 鈥淭his has dramatically increased the number of heart transplants we can do,鈥� says of the Royal Brompton and Harefield NHS Foundation Trust in London, which is spearheading use of the device in the UK.
But the new system developed in Sweden takes an intermediate route, keeping the heart at 8掳C, and perfusing it with a blood-like fluid with high levels of potassium that stop the heart from beating. In this state the organ鈥檚 cells are less active than at 37掳C, and its need for oxygen is slashed. 鈥淚t鈥檚 like being in a deep sleep,鈥� says Steen.
As a result, the heart can be perfused at a lower rate than when it鈥檚 beating, which should put less stress on the blood vessels. This may make the heart last longer, says John Dark of Newcastle University, who hopes to start UK trials of the device next year. The device has been successfully tested on 100 pigs, with hearts before being transplanted. Being able to maintain a human heart outside of the body for 24 hours would be a great advantage, says Simon.
Healthier hearts
The first patient to receive a heart in this way, on 31 August, was a 52-year-old Swedish man who was dying of heart failure. Stored for 3 hours, the heart automatically restarted beating once it warmed up inside the man鈥檚 body and his blood flushed away the potassium. The operation was judged a success and the patient is now recovering at home, says Steen.
Both TransMedics鈥� device and the Swedish technique have other advantages over cold ischaemic storage. Hearts are usually taken from people who are brain-dead, a state that disturbs levels of many blood chemicals, damaging heart tissue. But preserving the heart while perfusing it with a blood-like fluid means that the muscles recover. 鈥淲hen you perfuse the heart with normal concentrations of everything, the heart repairs itself,鈥� says Steen.
This approach also provides the opportunity to test the heart鈥檚 health. This can be done by analysing chemicals released by the heart into the perfusion fluid, and may help ensure that only healthy organs are put into patients. However, Simon says that being able to examine the heart while it is beating is an advantage when assessing heart health.
Hearts aren鈥檛 the only organs being targeted for longer-term storage outside the body 鈥� other teams are working on lungs, liver and kidneys. A device that keeps the liver functioning at body temperature has doubled preservation time to 24 hours, says at the University of Oxford.
Steen says his system could also be used for other organs, and hopes it will eventually become routine for transplant organs to be sent across continents.
