Heart Cells “Crooners who lament that broken hearts never mend may need to find another tune.” Scientist are finding new evidence that suggests that, contrary to scientific consensus, heart muscle cells do divide and the number of cells can increase. The vast majority of heart muscle cells, or myocytes, had been thought to stop dividing by the time a person reaches the age of 9. These cells then pump blood for the rest of a healthy person's life. In people stricken by a heart attack, the cells die and are replaced by scar tissue. The first report of a human myocyte caught in the act of dividing appeared in July 21. (Pr