ABSTRACT
Introduction During development, increases in heart size results as a consequence of the differentiation and proliferation of cardiomyocytes, neurons, interstitial cells, and components of the vasculature. At birth, cardiomyocytes undergo a gradual transition from hyperplastic to hypertrophic growth, such that subsequent increases in myocardial mass result largely from increased myocyte size rather than increased number. In contrast, the other cell types present in the heart retain the ability to proliferate. Consequently, in adults, although cardiomyocytes constitute approximately 90% of the mass of the heart, they constitute less than 20% of the total number of cells present.
