Postnatal Development of the Heart

Postnatal anatomical and functional development of the heart: A species comparison

“…In the rat and dog, the left ventricle is less spherical in the postnatal period, compared to adults, due to growthrelated changes in ventricular dimensions (House and Ederstrom, 1968;Grimm et al, 1973;Lee et al, 1975). Smith, 1928. Heart weight, in relation to body weight, is greater in the newborn than the adult in most common laboratory animals (House and Ederstrom, 1968;Lee et al, 1975;Rakusan, 1980). Subsequently, the heart:body weight ratio decreases with age (Table 2).…”

“…The heart doubles its birth weight by 6 months of age and triples by 1 year (Smith, 1928;Rakusan, 1980). It should be noted that heart weights in infants and small children are highly variable and available mean data show a deviation factor of 2-3 (Rakusan, 1980). After a brief surge during the early postnatal period, the increase in cardiac weight is proportional to the increase in body weight, resulting in a constant relative cardiac weight throughout the first half of life (Table 1).…”

“…The heart doubles its birth weight by 6 months of age and triples by 1 year (Smith, 1928;Rakusan, 1980). It should be noted that heart weights in infants and small children are highly variable and available mean data show a deviation factor of 2-3 (Rakusan, 1980).…”

“…The transition from prenatal to postnatal circulation involves three primary steps: 1) cessation of umbilical circulation; 2) the transfer of gas exchange function from the placenta to the lungs; and 3) closure of the prenatal shunts, at first functionally and then structurally (Rakusan, 1980(Rakusan, , 1984Friedman and Fahey, 1993;Smolich, 1995).…”

“…In the second year, the ratio of right ventricle:left ventricle volumes reaches 2:1 and does not change with age (Kyrieleis, 1963). Studies on the relation of the right and left ventricular weight at birth show high variability (Rakusan, 1980).…”