Study Backs Idea That Heart Can Repair Itself
Doctors have long assumed that damage from a heart attack or other ailment is irreversible and that the heart cannot regenerate tissue the way other organs can. But last year, a team of American and Italian researchers demonstrated that heart muscle cells multiplied after a heart attack.

And now they have shown that in heart transplant patients, primitive cells from the patient travel to the new heart and grow new muscle and blood vessels. Studying men who received transplanted hearts from women, the researchers discovered male cells in the donated female hearts — cells that could only have come from their own bodies.
http://www.nytimes.com/2002/01/03/health/03HEAR.html?todaysheadlines&pagewanted=all