Evaluation of pulmonary and systemic blood flow by 2-dimensional Doppler echocardiography using fast fourier transform spectral analysis

This study was designed to assess the accuracy and problems of noninvasively measuring right and left cardiac output by range-gated pulsed Doppler echocardiography. Sixteen children with cardiac disease, aged 3 months to 17 years, served as the subjects; 2-dimensional range-gated pulsed Doppler echocardiographic data were unobtainable in 2 children, leaving 14 for study. Diagnoses included shunt lesions, valvular abnormalities, coarctation, repaired defects, and Kawasaki's disease. The equipment for this study included a 2-dimensional echocardiographic Doppler sample volume locator. The Doppler frequency shift was analyzed by fast Fourier transform. Twenty 2-dimensional range-gated pulsed Doppler echocardiographic measurements (10 pulmonary and 10 aortic) were made simultaneously with indicator dilution outputs or angiographic outputs. In 4 subjects, 2-dimensional range-gated pulsed Doppler echocardiographic aortic outputs were not possible. For this study, vessel diameter was determined by both echocardiography and angiography, Doppler intercept angle by 2-dimensional echocardiography, and velocity by 2-dimensional range-gated pulsed Doppler echocardiography. Comparison of cardiac output measurements obtained by invasive methods and by 2-dimensional range-gated pulsed Doppler echocardiography (angiographic vessel measurement) showed a correlation of +0.94 (standard error of the estimate [SEE] = 0.53) with a slope of y = 0.83 × + 0.61, indicating that the slope and line of identity were almost equal and the offset from 0 was small. For 2-dimensional range-gated pulsed Doppler echocardiography (echocardiographic vessel measurement), the correlation was +0.94 for aortic flow but only +0.72 for pulmonary flow. Problems encountered in some patients included turbulence, which made velocity measurements unreliable, difficulty in obtaining aortic flow by Doppler echocardiography due to transducer configuration, and measurement of pulmonary diameter by echocardiography. The results indicate that 2-dimensional range-gated pulsed Doppler echocardiographic outputs are accurate under conditions of nonturbulent or minimally turbulent flow and adequate imaging, but only when vessel diameter can be accurately measured.