Surgeons say they have performed the first transplant using a 'dead' heart. Could this fill the deficit of donor hearts?
In October 2014, multiple headlines reported that a heart had stopped beating and been revived, before being transplanted into a living recipient. Scientists in Australia told the story of how they had transplanted the 'dead' heart. Could this be the answer to the shortage of donor hearts? Oscar Howard 'Bud' Frazier and his colleague Dr William 'Billy' Cohn of the Texas Heart Institute don't think so.
Once a heart has stopped beating, says Cohn, there is only a very short time in which to get it removed from the body, restarted, and prepared for transport and transplantation before it deteriorates so much that it's useless for a transplant -- and the only chance of everything happening within the right timespan is in an operating theatre. Somebody who dies outside a hospital is extremely unlikely to be able to provide a heart for transplantation because of the delay involved. "Does that mean you can take a dead guy…whose heart has stopped beating, and resuscitate it and use it?" says Cohn. "Yes, if you can get his chest open and get his heart out within three minutes. This patient [the Australian researchers] did it on was in the operating room with his chest open with people standing around waiting for him to die."
Beating hearts are normally taken from brain-dead people and kept on ice for a few hours before they are transplanted into patients. They are only kept on ice if it's necessary to transport them (which, admittedly, it usually is). The quicker a heart can be transplanted, the better.
The law that defined 'brain death' wasn't passed until 1981. In the USA's Uniform Determination of Death Act, brain death is described as the following: if the brain has been irreversibly destroyed and the patient can only survive with the help of life support, or even if the person still has a living brainstem (has a heartbeat and is still breathing unaided) but the cerebrum has been destroyed, that person is dead. In the UK, as of 1995, a person is declared dead if they no longer have any activity in their brainstem.
The definition of 'death' differs in some countries, such as Pakistan or Romania; there, if someone's brain is irreversibly dead and they have no brain activity or blood supply to their brain, but their heart is beating, they are still classified as alive. Heart transplants are not performed in these parts of the world.
Although the revived heart made global headlines, the method is unlikely to greatly increase -- or even double -- the donor heart pool. The demand for heart transplants exceeds supply by about 2000 hearts per year, but as Cohn says, "there aren't 2000 people who die with their chest open in the operating room".
"If you actually had [a] cardiac arrest and your heart stopped at home, and you called the ambulance -- by the time they get there, the heart's not usable," he explains. "Really, once a heart stops and isn't getting oxygen, irreversible things start to happen. We've had patients that have gotten CPR for 35 or 40 minutes and come back, but the CPR keeps blood going and pumping oxygen into them. If you're just lying there dead, with no blood circulating or no oxygen, after five minutes or ten minutes it'd be hard to have a usable heart."
There are simply not enough biological hearts to go round, and it doesn't look as though that will change any time soon. That's why scientists all over the world are still so keen to build a device that could be taken off a shelf and sewn into somebody: a total artificial heart.
This post first appeared on Mosaic and republished here under Creative Commons licence.