Fiberoptic-Dye Dilution Method for Measurement of Cardiac Output Comparison with the Direct Fick and the Angiocardiographic Methods

A new method for the measurement of cardiac output has been tested in 69 patients undergoing catheterization of the right and left sides of the heart. It is based on the recently described fiberoptic hemoreflection method. In order to verify the validity of these measurements, correlations with stroke indices determined by the Fick principle and by biplane angiocardiography were also carried out. Details of the biplane angio-cardiographic technique and of the fiberoptic calibration methods are given. Comparisons were carried out in 37 instances between the results after injections in the pulmonary artery (mean stroke index, 40.8 mI/M2) and in the left ventricle (mean, 42.9 ml/m2). Good agreement was found, r =0.930, with a mean difference of 2.1 ml/m2. Stroke indices by fiberoptics (FO) were first compared with those obtained by the standard Fick method. In 100 determinations the mean stroke index by FO was 45.7 ml/m2, and Fick 49.0 ml/m2 (r 0.859; confidence limits, 0.77 <p <0.93). Correlations were then carried out in 42 instances between stroke index by FO (mean, 49.1 ml/m2) and by angiocardiography (mean, 48.2 ml/M2, r 0.799; confidence limits, 0.65 < p < 0.90). Various factors influencing the angiocardiographic method for determining stroke index are discussed. It is concluded, that the fiberoptic-indicator dilution method is an accurate system to determine cardiac output regardless of the site of injection (LV or PA). Its ver-satility, the lack of need for blood withdrawal, and the generally satisfactory agreement with angiocardiographic or standard Fick method recommend its general application when cardiac output determinations are required during the process of cardiac catheteri-zation, provided sampling is carried out in the aorta. Additional Indexing Words: Stroke volume Pulmonary artery injection of dye T HE INSTANTANEOUS measurement of the concentration of indocyanine green in the aorta by means of a fiberoptic cathete