Human heart prior to dissection in a tissue bank. Parts of a heart taken from a donor or heart transplant recipient can be used in the treatment of other patients. The heart is dissected and its aortic, pulmonary and mitrial valves as well as some other tissues and conduit sections are removed. The extracted tissue is then treated in antibiotic solution before being cooled and stored in the vapour phase of liquid nitrogen, a procedure known as cryopreservation. Small samples are then tested for disease and if the tissue passes, it is stored until it is matched with an appropriate recipient.