[Quantitative assessment of regurgitant fraction in aortic regurgitation: comparison of two-dimensional Doppler echocardiography with other methods].

To determine proper operative procedures for aortic regurgitation (AR), we attempted to evaluate the severity of AR by two-dimensional Doppler echocardiography (TDE), using 15 mongrel dogs with experimentally-induced AR. Furthermore, the left ventricular (LV) suction method was investigated for the significance in estimating the severity of AR, cardiac outputs were measured by the thermodilution technique, TDE, and electromagnetic flowmeter (EMF). The values obtained by each method were compared. In dogs with AR, regurgitant fraction (RF) was calculated from stroke volumes obtained by TDE and EMF, as follows: RF [TDE] = (LVO-RVO)/LVO (LVO: left ventricular output; RVO: right ventricular output) RF [EMF] = [total stroke volume (T)-effective stroke volume (E)]/T The effects of alterations in afterload and pump flow rates on regurgitant fractions and regurgitant volumes measured by the LV suction method were also studied. The following results were obtained: Good correlations were observed between RVO and LVO measured by TDE, and those measured by the thermodilution technique and EMF, respectively. In dogs with AR, regurgitant fractions measured by TDE correlated well with those measured by EMF. These results strongly suggested that the Doppler index (RF) was accurate and useful for estimating the severity of AR clinically. Regurgitant volumes measured by the LV suction method were not influenced by the pump flow rate, and they correlated well with square root values of the mean diastolic pressure in the aorta. In the LV suction method, Bernoulli's theorem held good between the regurgitant volumes and the mean diastolic pressures in the aorta of the dogs with AR. Considering the factors of mean diastolic pressure in the aorta and diastolic time, regurgitant volumes measured by EMF in the beating heart showed excellent agreement with those measured by the LV suction method in ventricular fibrillation. Therefore, to evaluate quantitatively the pathophysiological changes of the aortic valve in patients with AR, we should estimate the severity of AR using regurgitant volumes corrected for the cardiac cycle at the same mean diastolic pressure in the aorta.