Sinclair, J. D.

In studies on dogs, blood was sampled as for the recording of dye-dilution curves through monochromatic densitometers. Injection of hypertonic media into the superior vena cava caused transient increases in the optical density of blood in the pulmonary and femoral arteries so as to produce apparent “dye” curves. The injection of hypotonic and hemolyzing media produced negative deflections, representing decreases in the optical density of blood, as did brief ventilation with 5% and 50% carbon dioxide in oxygen. Similar changes were demonstrated in vitro. They were compensated for in vivo by the use of a dichromatic densitometer. The changes observed are attributed to altered physical properties of the erythrocytes, which consequently change their light-transmitting and light-reflecting characteristics. Such nonspecific changes in the optical density of blood may constitute an important source of error in monochromatic densitometry done on whole blood. Submitted on January 11, 1961

Indicator-dilution curves were recorded simultaneously from the left atrium and the femoral artery during injections of indocyanine green into the left ventricle in normal dogs and in dogs with chronic mitral regurgitation. A study was made-without the use of thoracotomy-of the effect of the following factors on the amount of early appearing indicator detected in the left atrium: (a) the timing of the injection of indicator in relation to the cardiac cycle, (b) the position of the injecting catheter in the left ventricle, and (c) the position of the sampling catheter in the left atrium. It was found that the time and site of the injection into the left ventricle had little effect on the amount of early appearing dye detected in the left atrium and that, although the position of the sampling catheter in the left atrium was important, reproducible results were attained when the sampling site was restricted to a region in close proximity to the mitral valve. A close correlation was demonstrated between the volume of regurgitation determined independently on a hydraulic basis and the volume estimated from the fraction of early appearing indicator detected in the left atrium. It is concluded that further work with this upstream-sampling technique is justified in order to study its possibilities as a practical method for detecting and quantitating mitral regurgitation in human beings.