Measurement of Coronary Blood Flow Using Radioactive Iodine Compared with Nitrous Oxide

The short time required for arterial blood to pass from the heart through the coronary sinus requires fast recording. Curves recorded simultaneously from the precordium and from either the proximal pulmonary artery or the coronary sinus afforded no means for approximating coronary blood flow. These results are interpreted as indicating that the radioisotope-dilution method for the determination of coronary blood flow is impracticable in the dog, with our present instrumentation. This is because of the inherent uncertainty and the numerous technical difficulties involved in putting a bolus into a coronary artery and recording from coronary-sinus blood, when using as standards of reference a nitrous-oxide flow and the Fick cardiac-output measurements.