Researchers are planning transplants that may revive tissues thought to be hopelessly damaged, including the heart and brain. The plan is to infuse mitochondria or a placebo solution into the coronary arteries of people having bypass surgery or ? an even more dire situation for the heart ? having both bypass and valve surgery. The patients would be those whose hearts are so damaged that it would be difficult to wean them from heart-lung machines after surgery. For these patients, mitochondrial transplants are an appealing option.