NEWS & TECHNOLOGY
Hearts kept alive outside the body A technique that sends hearts to sleep could let them keep for days Clare Wilson
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A NEW way of keeping donated hearts alive for a day or more could bring an end to people dying while on the transplant waiting list. The method was tested on the first patient in August, with a heart kept in a “deep sleep” state for 3 hours. It will be tested on five more people for this same time and, if all goes well, the storage time will be gradually raised to 24 hours. Stig Steen at Lund University in Sweden, who developed the technique, says it could potentially be extended to several days. Keeping hearts alive for longer outside the body would mean more are available for transplants. In the UK, over a thousand people die yearly for want of a new heart. Distance between donor and recipient is a particular problem, because hearts can currently be kept alive outside the body for only a few hours before they weaken. NHS Foundation Trust in London, The usual way to transport which is spearheading use of the hearts involves keeping the device in the UK. organs at 4°C, without an oxygen But the system developed in supply. The longer this goes on, Sweden takes an intermediate the worse the heart will work route, keeping the heart at 8°C, when transplanted. The upper and perfusing it with a blood-like limit is about 4 hours. “We say no to a lot of good hearts,” says Steen. fluid containing high levels of potassium that stops the heart “With the new way, we can take from beating. In this state, the hearts from theoretically the organ’s cells are less active than whole world. We can get the at 37°C, and its need for oxygen is perfect fit for each patient.” slashed. “It’s like being in a deep One recent advance is a device sleep,” says Steen. that keeps the heart beating at As a result, the heart can be body temperature, perfused perfused at a lower rate than with blood from the donor. Manufacturer TransMedics, based when it’s beating, which should put less stress on its blood vessels. in Andover, Massachusetts, says hearts can be kept on the machine This may make the heart last for between 7 and 12 hours. “This “We should be able to take has dramatically increased the hearts from the whole number of heart transplants we world to get the perfect can do,” says André Simon of the fit for each patient” Royal Brompton and Harefield 6 | NewScientist | 14 October 2017
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longer, says John Dark of Newcastle University, UK. The system has been tested on 100 pigs, with hearts kept “asleep” for 24 hours before being transplanted. Being able to maintain a human heart outside of the body for 24 hours would be a great advantage, says Simon.
Self-healing hearts The patient who received a heart in this way in August was a 52-year-old Swedish man dying of heart failure. Stored for 3 hours, the heart automatically resumed beating once it warmed up inside the man’s body and his blood flushed away the potassium. The man is now recovering at home, says Steen. Both TransMedics’s device and the Swedish technique have other
advantages over storage at 4°C. Hearts are usually taken from people who are brain-dead, a state that disturbs levels of many blood chemicals, damaging heart tissue. But providing the heart with a blood-like fluid means the muscles recover. “When you perfuse the heart with normal concentrations of everything, the heart repairs itself,” says Steen. Other teams are working on storing donated lungs, liver and kidneys for longer outside the body. A device that keeps the liver functioning at body temperature has doubled preservation time to 24 hours, says Peter Friend at the University of Oxford. Steen says his system could also work for other organs, and hopes it will eventually become routine for transplant organs to be sent across continents. Q