Abstract
In cardiac surgery, many problems remain unsolved about the pulmonary hypertension with which congenital cardiac anomalies with left to right shunt, are accompanied. The author studied on the pulmonary hypertension with special reference to precapillary pulmonary hypertension in ventricular septal defect from both hemodynamic and histological aspects. And for the purpose of hemodynamic analysis of pulmonary hypertension, theoretical considerations on pulmonary circulation were presented. Forty nine cases of ventricular septal defect were studied. The routine right heart catheterization was performed. At operation lung biopsies were obtained immediately after thoracotomy, and microscopic preparations were stained with Verhoeff's elastic tissue stains counterstained with Van Gieson's connective tissue stains. Histological studies were carried out on small pulmonary arteries and arterioles, and the ratios of medial thickness to diameter of small muscular arteries were measured separately with eyepiece micrometer and were averaged. A) Theoretical Considerations on Pulmonary Circulation. becomes more remarkable if the heart rate does In hemodynamics, pressure and flow are the most fundamental factors, and the relationship between pressure and flow is characterized by many parameters as mechanical properties of circulatory system. As the parameters which constitute "Impedance", comliance, resistance and inertance are considered. The formulae to calculate Resistance, Compliance and Inertance of pulmonary arterial tree were presented, and from the analogy of the differential equation describing the mechanical impedance of wave propargation in a elastic tube to that of electronic circuit consisting of resistance, inductance and capacitance in series, a equivalent four terminal network for the circulation model of the pulmonary arterial tree was designed. Thus the input impedance in pulmonary arterial tree and the transfer function between pulmo-nary artery pressure and pulmonary arteriolar blood flow were discussed.
