Studies on Pulmonary Circulation by <SUP>131</SUP>I Radiocardiography.

Abstract

The pulmonary circulation time measured by the right heart catheterization actually includes the circulation time from the left ventricle to an arm where the blood sample is taken. Therefore, it does not represent the accurate pulmonary circulation time. It is not accurate as well to measure the pulmonary blood volume by the right heart catheterization.The radio-cardiogram obtained by the use of radio-isotope records two peaks on its curve, the one representing the time when the isotope used is passing through the right heart, and the another representing the time when it passing through the left heart. Thus obtained pulmonary circulation represents the circulation time from right to left heart and is much more accurate. It is called ""R-L time"".To avoid the inaccuracy of the traditional dye dilution method, the pulmonary circulation time was measured from the radio-cardiogram obtained by the use of 131I. Method Total of 44 cases were studied, including 7 normal subjects, 20 cases of pulmonary diseases and 17 cases of cardiac diseases.On the chest of a patient in supine position, a scintilation detector was placed at the center of the cardiac siluette under fluoroscopy or at the center of the absolute cardiac dullness. 20 to 60 μc of 131I diluted with 0.3 to 1.1 cc of normal saline was instantly injected into cubital vein and radiocardiogram was obtained by the use of scintilation counter and scintilation ratemeter, from which R-L time was measured. Immediately afterward cardiac output was measured by the dye dilution method and the pulmonary blood volume was calculated according to the formula of Stewart-Hamilton. Hemodynamic changes by exercise were also observed in these patients.Result and Conclusion 1) Means of resting R-L time were 3.9 sec. in normal subject, 7.7 sec. in mitral stenosis, 5.2 sec. in hypertension, 5.7 sec. in coronary disease, 4.3 sec. in pulmonary tuberculosis, 4.7 sec. in bronchial asthma, 5.1 sec. in bronchiectasis and 5.3 sec. in pulmonary emphysema. This shows that the pulmonary circulation time was markedly prolonged in cardiac disease even at rest.2) Pulmonary blood volume calculated from the R-L time was much lower than that from the dye dilution method.3) By exercise, R-L time was altered along with changes in mean circulation time measured by the dye dilution method. In most of the cases, R-L time was shorted when mean circulation time was shortened, and R-L time was prolonged when mean circulation time was prolonged.4) By exercise, R-L time was shortened, cardiac output was increases and pulmonary blood volume was slightly decreased in healthy subjects and in pulmonary diseases. On the contrary, in many cases of cardiac diseases, especially in coronary disease, R-L time was prolonged, cardiac output was decreased and pulmonary blood volume was slightly increased. In cardiac disease, already increased pulmonary blood volume at rest was more increased by exercise and pulmonary congestion developed consequently.5) The prolongation of the R-L time by exercise suggests decreased reserve capacity of the heart. To know the cardiac reserve capacity, the method is recommendable as a non-operative procedure which can be done easily and repeatedly.