A New Approach to Pulmonary Blood Volume Determination in Congenital Heart Disease with Left-to-Right Shunts

¹ From the Department of Pediatrics and the Cardiopulmonary Laboratory, National Taiwan University School of Medicine, Taipei, Taiwan, Republic of China

In 16 dogs and in 40 infants and children with congenital heart disease (CHD), indocyanine green was injected into the main pulmonary artery and left atrium, and paired dye-dilution curves were inscribed. Analysis of 54 pairs of dye curves inscribed in dogs and children with no left-to-right (L-R) shunts revealed that the correlation between pulmonary mean transit time and peak time difference was good (ry·xx² = 0.889; P_r < 0.001), in the form of a parabola expressed by the equation, y_c = 0.99 + 0.31x + 0.l7x². Forty-seven pairs of atypical curves were inscribed in CHD with L-R shunts, in which pulmonary mean transit time was derived from peak time difference through use of the regression equation. Pulmonary blood flow (PBF) was calculated by either the forward-triangle or Fick's method. Pulmonary blood volume (PBV) was calculated as the product of pulmonary mean transit time and PBF. The validity of the method was checked by gamma function analysis. This method proved to be reasonably accurate and useful for determination of the hitherto unmeasured PBV in CHD with L-R shunts.