Table 1.

Cardiomyocyte transition from hyperplasia to hypertrophy

Age range	Cardiomyocyte type	Key points	Citation
<0 weeks	Ventricular	Hyperplasia contributes to increased heart size before birth  Total cell volume per cardiomyocyte nucleus remains consistent before birth	Mayhew et al. (1998)
≤16 weeks	Ventricular	Hyperplasia ceases soon after birth  Number of cardiomyocyte nuclei increases throughout gestation	Mayhew et al. (1997)
≤1 year	Atrial	Narrow window of postnatal proliferation  Postnatal cardiomyocyte proliferative potential is highest in patients <3 months old	Ye et al. (2016)
0–59 years	Left ventricular	Hypertrophy begins after birth  Infants have highest rates of cardiomyocyte mitosis and cytokinesis.  Cardiomyocyte volume is eight times larger in adults	Mollova et al. (2013)
0–73 years	Left and right ventricular	Transition to hypertrophy occurs almost immediately  Total number of cardiomyocytes is established postnatally within 1 month.  Volume of myocyte nuclei decreases, whereas hypertrophy increases from birth to adulthood	Bergmann et al. (2015)
0–75 years	Left ventricular	One nucleus per cardiomyocyte  Cardiomyocytes remain mononucleated; nuclear content increases with age	Takamatsu et al. (1983)
0–90 years	Left ventricular	DNA synthesis occurs with hypertrophy  Myocytes are diploid at birth, but increased polyploidy is observed with age	Eisenstein & Wied (1970)