Estimation of the size of the patent ductus arteriosus from hemodynamic data.

The effects of patent ductus arteriosus upon the circulation were studied by Eppinger, Burwell, and Gross (1). Later, Dexter, Haynes, Burwell, Eppinger, Sosman, and Evans (2) described preoperative and postoperative hemodynamic studies obtained by cardiac catheterization in a patient with patent ductus arteriosus. Since the presence of a patent ductus arteriosus can. be detected by physical examination in more than 95 per cent of the patients having this condition (3), cardiac catheterization studies are needed as an aid to diagnosis only where the murmur is atypical, or when there is a possibility of an additional abnormality. When the single lumen cardiac catheter is used, it may be very difficult to distinguish between shunts of oxygenated blood into the upper right ventricle and shunts into the pulmonary artery (4). At times, aortography may be needed to settle the diagnosis unless the cardiac catheter is passed through the ductus arteriosus. Hemodynamic data may, however, be of assistance in estimating the size of the patent ductus arteriosus (5). This information may be of value in contemplating interruption of the ductus in very young children, or in adults over the age of forty. In addition, the suggestion of a very large channel may warn the surgeon of possible technical difficulties in its ligation or division. This paper describes in twelve patients a comparison between the diameter of the ductus as measured at operation and certain hemodynamic observations obtained preoperatively. In the preoperative study, the following values were determined: increase in oxygenation of pulmonary arterial over mixed venous blood; volume of left to right shunt through the ductus; the internal diameter of the ductus arteriosus calculated from an orifice formula (5).