How does the patient survive being heartless before the new heart is implanted and how does the new heart even begin to start working in a new body?
In: Biology
The patient is put on a heart-lung machine which oxygenates & circulates the blood while the operation takes place. Once the new heart is sutured, it is shocked by a defibrillator and begins beating again.
During the transplant the patient is put on cardiopulmonary bypass. Basically all of the blood that would be going to the heart instead enters a tube, goes through a machine that helps to pump it, then travels through tubes that connect to the blood vessels exiting the heart.
Once on bypass, the old heart is cut out and the new heart is put in with the blood vessels sutured to the new heart. The new heart then begins to pump on its own.
The timing of the heart beat is generally controlled by a group of cells in the top of the heart. The cells essentially leak electrolytes, then when the level reaches a certain point, those cells send out a signal to cause the heart to contract. Then the cells reset the electrolytes and start leaking again. The rest of the muscle cells are kind of like dominoes. Once one of them is triggered to contract, the cells around it are triggered to contract and this pattern spreads through the entire heart.
(IANAD) When they do surgery that requires stopping the heart, they divert the bloodflow to a machine (essentially an external mechanical heart) to keep the blood flowing where it needs to be flowing. That frees them up to remove the old heart (which is a complicated set of muscles and valves) and hook up the transplant heart. They sew up the connections, [and the heart has a group of cells] to tell the heart to pump. When the surgeons are ready, they re-divert the bloodflow to the new heart, which knows to beat because of its special cells.
Since the body recognizes that this new muscle is foreign material, the transplant recipient must take drugs the rest of their life to keep their body from attacking the foreign material.
I have a side question. I’ve been told that when a heart stops beating completely as opposed to being in fibrillation that someone can’t be revived. But obviously they get it going again in heart transplants. What’s the difference?
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