Postnatal development of the pig heart.

The small amount of data concerning the normal postnatal development of the pig heart has prompted us to study and quantify these changes from birth to the sixth month of postnatal life. The method used consisted of separation of the various cardiac components. Their individual weights are assessed, and width and length of both ventricles were determined. The free wall myocardial thickness of both ventricles was also measured. Major differences in the growth pattern of the ventricles were clearly shown. At birth the free will of the left ventricle was already thicker than that of the right ventricle. This difference became more accentuated with growth. Similar findings in terms of mass were found, but the difference between the two free walls was reduced. There was disproportionate postnatal growth in favour of the left ventricle in all measurements taken except length. The right ventricle was longer in the newborn period.