The pulmonary and systemic circulations in congenital heart disease.

The application of cardiac catheterization to the study of the human circulation (Forssmann, 1929; Cournand and Ranges, 1941) provided a new technique for obtaining information about the pulmonary circulation and also for the study of the physiological effects of congenital heart disease (Bing et al., 1947a; Dexter et al., 1947b; Cournand et al., 1949). Extensive studies have been made in which the pulmonary circulation in congenital heart disease has been investigated and in particular the pulmonary blood flow and peripheral resistance have been evaluated (for instance Bing et al., 1947b.; Handelsman et al., 1948; Hickam, 1949; Wood, 1950). It has long been known, however, for the systemic circulation that the elasticity of the arterial walls in relation to their Windkessel (pressure reservoir) function is of great importance as well as the peripheral resistance (Frank, 1899 and 1926; Broemser and Ranke, 1930; Wezler and Boger, 1939). Cournand (1947) has recently pointed out that the same consideration applies to the pulmonary circulation but so far no quantitative estimations of the " elasticity resistance " in the pulmonary circulation have been presented. Cardiac catheterization used for the investigation of congenital heart disease yields data that may be used for the study of the systemic circulation as well as the pulmonary, so that it is possible to compare the effect of the cardiac abnormality on the two circulations although hitherto attention has usually been concentrated on the pulmonary circulation. Formulae that give mathematical expression to the arterial Windkessel function are available and some are applicable to the data obtained by catheterization studies in normal subjects or in those with many forms of acquired or congenital heart disease. These or other formulae applied to the analysis of the changes occurring in the two circulations are capable of yielding valuable results enabling these changes to be studied with greater precision. From cardiac catheterization studies made in patients with suspected or proven congenital heart disease we have been able to make such an analysis in a variety of conditions and have confirmed the importance of the elasticity resistance in the pulmonary arterial system and of the interrelationship of the various components that determine the arterial blood pressure.