The Identification of Right-to-Left Shunts

SEVERAL METHODS are now used in conjunction with cardiac catheterization for localizing and quantitating right-to-left shunts. These include the recording of indicator-dye concentration curves after selective intracardiac dye injection,14 the external recording of radioactivity following injection of radioactive materials,5 6 and the use of cardioangiograms or cineangiograms to picture the course taken by contrast media introduced selectively through the cardiac catheter.7 Such methods may provide both qualitative and quantitative information, but in some instances they embody either theoretical or practical disadvantages to the patient. These include the theoretic hazards inseparable from the use of radioactive materials, the cost of special equipment and its early obsolescence owing to improvements in design, and finally the small increase in risk associated with repeated angiocardiograms. We believe that we are justified in reporting our results using a qualitative, simple, and safe method of identifying the origins of right-to-left shunts. This information, in addition, permits accurate selection of the best site from which to perform intracardiac injections of contrast media. While the use of indicator-dilution curves has been recommended for such preliminary localization of shunts,8 the test to be described requires no special equipment. Although it does not lend itself to quantitative interpretation, the ether test will always give a definite positive or negative result.