The heart of the newborn child: an anatomical study based upon transverse serial sections.

This study of the newborn child heart is based mainly on observations made on thin (0.2 mm) serial transverse sections of an entire thorax. Several features of the cardiovascular system associated with the fetal circulation are discussed. Despite considerable differences between the cardiac form in the newborn child and that in later postnatal life, the orientation of the heart in the newborn child has already attained many of its postnatal features. For example, it lies more nearly in the horizontal than the vertical plane and the atrial and ventricular septa are in line with each other at an angle of about 45 degrees to the median plane. This angulation of the septa determines that the right atrium and ventricle lie as much in front of the corresponding chambers of the left heart as they do to their right side. The cardiothoracic ratio and thoracic index are derived from a section through the thorax of the newborn child and these values are compared with those from a section through an adult man. A major purpose of this communication is to make a plea that the nomenclature given to all cardiac structures, even in the newborn child, should be consistent with the heart in situ in the anatomical position.