By using the amount of carbon 14 in the atmosphere from above-ground nuclear testing in the 1950s and 1960, researchers have determined that cells in the human heart develop into adulthood.

But as humans age, the percentage of new heart cells decreases markedly. By age 25, renewal of heart cells gradually decrease from 1 percent turning over annually to .45 percent by the age of 75. About 50 percent of the heart cells a human is born with will regenerate during a lifetime.

Myocardial damage often results in chronic heart failure because of the loss and insufficient regeneration of heart cells. But this new finding may mean that patients, who have suffered myocardial damage as a result of a heart attack, may have some good news.

Lawrence Livermore National Laboratory scientist Bruce Buchholz with colleagues from the Karolinska Institute, Université Claude Bernard Lyon, Lund University and Lund University Hospital, found that cells in a human heart can develop into adulthood and the age of heart cells is, on average, six years younger than the individual.

Using the Laboratory's Center for Accelerator Mass Spectrometry, Buchholz measured the amount of carbon 14 in DNA to establish the age of caridiomyocytes (cardiac muscle cells) in humans…