The Use of Fiberoptics in Clinical Cardiac Catheterization

The fiberoptic instrument and catheters described in the preceding study were employed in the measurement of indocyanine-green concentrations in the circulatory system by a simple change of filters. Cardiac output was calculated from the recorded curves in 19 instances. In 13 of these, the results were compared with cardiac output determinations simultaneously obtained by a conventional method. There was good agreement for each of the values obtained (range 2.37 to 7.32L./min., r = 0.985). The only blood withdrawn in each patient was the 8 ml. needed for calibration. Distinct step-function was seen in the descending as well as the ascending portions of the curves. In three instances left ventricular injections were done and end-diastolic and end-systolic volumes calculated. The results are similar to those reported for thermodilution methods. From the rapidly changing concentration of dye within one cardiac cycle in the presence of aortic regurgitation, a formula was derived by which the amount of regurgitation could be calculated. This method was tested in a model where regurgitation varied up to twice the forward stroke volume by means of a ther-modilution method. Good agreement between measured and calculated degrees of regurgitation (r = 0.928) in 26 observations is shown. The application of the formula to a patient with proven aortic regurgitation is demonstrated.