cardiomyocyte

noun

car·​dio·​myo·​cyte ˌkär-dē-ō-ˈmī-ə-ˌsīt 

: a muscle cell of the heart

A deficiency of cardiomyocytes underlies most cases of heart failure, and scientists have long sought to repopulate the heart with new cardiomyocytes.

—Charles E. Murry et al., The New England Journal of Medicine

… they have converted human embryonic stem cells into cardiomyocytes, the muscle cells that drive the beating of the heart.

—John Travis, Science News