Nuclear deoxyribonucleic acid content in congenital cardiac malformations.

Cytophotometric measurements of the DNA content of human heart muscle nuclei were performed on normal and congenitally malformed hearts of children. Congenital malformations of the heart lead to an early increase of the ploidy pattern as a sign of myocardial overload. This increase is significant. It starts, at the earliest, after the 3rd week of life. The degree of polyploidization of the muscle nuclei in malformed hearts is dependent on the type of overload. Pressure load produces a stronger shift to higher ploidy values than does volume load. The polyploidization is not dependent on either the heart weight at autopsy or the age of the child. It may be concluded that increasing functional requirement is the main cause of physiological and pathological polyploidization in hearts of children.