Diagnostic applications of indicator-dilution technics in congenital heart disease.

Introduction • The diagnostic use of indicator-dilution technics in the study of congenital heart disease dates, for practical purposes, from 1950 with the nearly simultaneous description of methods for continuous recording of the concentration of Evans blue dye from Johns Hopkins University and from the Mayo Clinic." The diagnostic applications of indicatoi'-dilution technics have been intensively applied and developed at the clinic since that time using the technic of intravascnlar injection of: colored dyes almost exclusively." These various technics have proved of great value and for the last 10 years have, in this laboratory, been considered an indispensable tool in diagnostic studies of patients with congenital heart disease. They attain particular value when used in conjunction with various technics for catheterization of the right and left sides of the heart, and with combinations thereof." During this period more than 12,000 indicator-dilution curves of various types have been recorded in more than 3,600 patients studied in the cardiovascular laboratory. The diagnostic as well as the investigative value of these technics has gradually received progressively widespread recognition." The rate of this progression has, however, been greatly accelerated in the last 2 or 3 years with more general availability of suitable instrumentation and particularly with the introduction of foreign gases for use as indicators in these technics. The first of these gases was nitrous oxide,' the use of which was rapidly followed by the use of the radio-