Pulmonary hypertension in congenital heart disease

Abstract

With the aid of the cardiac catheterization technic a study has been made of the incidence and severity of pulmonary hypertension in a selected group of patients with single cardiac anomalies; twenty-four cases of atrial septal defect, twenty-four cases of patent ductus arteriosus and twenty cases of ventricular septal defect. For all these patients, none of whom were in congestive failure, the diagnosis had been made with a high degree of certainty. Although pulmonary blood flow was not significantly different in the three groups, a mean pressure in the pulmonary artery of more than 40 mm. of mercury was observed in only one case of atrial septal defect, but occurred in fourteen of the cases of ventricular septal defect and in ten of patent ductus arteriosus. Severe hypertension was also found in two additional atypical cases of atrial septal defect. When moderate or severe pulmonary hypertension was present, it was due to increased pulmonary resistance as the pulmonary blood flow usually was decreased or within the range of normal. The available data establish, but do not permit a complete explanation of, the differences in pulmonary resistance between the group of patients with atrial septal defect and the groups with ventricular septal defect and patent ductus arteriosus. Maintenance of a high pulmonary resistance is essential for survival in many cases of ventricular septal defect and patent ductus arteriosus. This increased resistance may be due in part at least to a persistence of the fetal structure in the small pulmonary arteries and arterioles, the cause of which is, however, unknown. The development of compensatory vascular changes to reduce excessive pulmonary blood flow and the development of degenerative vascular changes may be caused by increased pulmonary flow. But, since the level of pulmonary blood flow was not significantly different among the three groups studied, the volume of flow alone cannot account for the development of the changes in pulmonary resistance found. It is suggested that factors of kinetic energy involved in the ejection of large volumes of blood from a high to a low pressure system such as occurs in many cases of ventricular septal defect and patent ductus arteriosus contribute important components to the pulmonary pressure pulse in these conditions, that are not present in the pulmonary pulse associated with the usual cases of atrial septal defect, in which the right ventricular ejection pattern is essentially normal. Such kinetic energy factors may contribute to the differences in calculated resistances in the pulmonary bed which have been obtained and may be conducive to degenerative occlusive changes in the pulmonary arterioles.