Estimation of Intracardiac Shunts in Congenital Heart Disease: A comparison of the dy-edilution and the Fick methods

ABSTRACT

During cardiac catheterizations in 20 cases with congenital heart disease, intracardiac shunts were measured by two methods, dye dilution method and the Fick method, and the results were compared. Arterial dilution curves were used for the estimation of both the right-to-left and left-to-right shunts-Venous dilution curves were used for measurement of left-to-right shunts. In cases with a left-to-right shunt, the amount of the shunt was expressed as per cent of total pulmonary blood flow and, in cases with a right-to-left shunt, as per cent of total systemic blood flow. The following results were obtained. 1. In 8 cases with a right-to-left shunt, the amount of the shunt was 35.6 +/-18.1% by the Fick method and 34.0 +/-19.2% by arterial dilution curves. The difference was not statistically significant(p> 0.l). In 15 cases with a left-to-right shunt, the amount of shunt was 41.3 +/-26.6% by the arterial dilution curve and 36.6 +/-14.O% by the Fick method. The difference was not statistically significant(p> 0.1). Also venous dilution curve was performed in 8 cases of left-to-right shunt and the amount of the shunt was 33.0 +/-21.0%, as compared to 35.5 +/-17.3% by the Fick methods. The difference was not statistically significant (p> 0.1). 2. Arterial dilution curves could be used to localize right-to-left shunts and venous dilution curves left-to-right shunts, whereas tile Fick method was helpful only for the localization of left-to-right shunts. 3. It was possible to detect small left-to-right (less than 10%) and right-to-left (less than 5%) shunts by dye dilution curves, which was not possible with the Fick method. 4. In detection of small intracardiac shunts as well as in shunt localization, the dye dilution method was more accurate than the Fick method. The difference of the amount of the shunt estimated by the two methods was not statistically significant.