Detection and Measurement of Experimentally Produced Aortic Regurgitation by Means of Indicator-Dilution Curves Recorded from the Left Ventricle

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Abstract
In dogs studied without thoracotomy the detection of immediately appearing indicator in the left ventricle following its injection approximately 1 cm downstream from the aortic valve can be used as a reliable index of the presence or absence of aortic regurgitation. With this type of injection and under the conditions of these experiments, the ratio of the area encompassed by the immediately appearing portion of the dilution curve recorded from the left ventricle to the area encompassed by the primary portion of the curve recorded at the femoral artery bears a close positive correlation (correlation coefficient: 0.9) to the severity of aortic regurgitation as estimated by back perfusion of the valve at necropsy. Within limitations, the position of the tip of the sampling catheter in the left ventricle in dogs with aortic regurgitation is not an important determinant of the amount of immediately appearing indicator detected in this chamber. Furthermore, although the amount of indicator detected in the left ventricle following injections of very short duration is time-dependent, if the duration of the injection is extended to cover the full systolic or diastolic phase of one heartbeat or continues over one or more heartbeats, the exact timing of this injection in relation to the cardiac cycle is not an important determinant of this variable. It is concluded that under these conditions the positive correlation established between the amount of immediately appearing dye detected in the left ventricle (expressed as the regurgitant fraction) and the severity of aortic regurgitation determined by back perfusion at necropsy can be used as a valid means of estimating the severity of aoritic regurgitation in dogs. The applicability of this indicator-dilution method to the study of clinical aortic reguragitation merits further study.