What is the substance called that keeps a donors heart alive while awaiting transplant??

Answer 1

You are probably referring to cardioplegia, a solution that keeps the heart from beating during preservation. Another very important substance is ice, which is used on the outside of the donor's heart to keep it cool.

Answer 2

Well to summerise your question this might help you :

Donor Cardiectomy
-Visualize/palpate the heart
-Divide the:
SVC
Left superior pulmonary vein
Incise IVC
-Clamp aorta
-Administer cardioplegia
-Avoid coronary sinus injury during liver procurement
-Divide aorta and pulmonary artery

There are other prerequistes e.g Donor should be less than 45 years of age, Brain death of donor, no Diabetes and so on.

Although the topic is interseting but very long full of dos and don't.