A pulsed Doppler echocardiographic method for calculation of pulmonary and systemic flow: accuracy in a canine model with ventricular septal defect.

Abstract

The accuracy of a quantitative, 2-dimensional, range-gated, Doppler echocardiographic method for estimating systemic and pulmonary flows was assessed by comparing them with simultaneous electromagnetic (EM) flow-meter determinations in an open-chest canine model with a ventricular septal defect, the size of which was varied. With each step-by-step variation in defect size, systemic and pulmonary flows were estimated by the Doppler method and matched to simultaneous pulmonary and aortic EM flow-meter recordings. The Doppler value for systemic blood flow was obtained by measuring the size of the aorta on a 2-dimensional echocardiographic image and sampling blood flow velocity in the ascending aorta. Because of high flow velocities and spectral broadening on the pulmonary artery Doppler flow curves in the presence of ventricular septal defects, pulmonary blood flow was measured as pulmonary venous return through the mitral valve orifice, with the size of the mitral orifice measured on the short axis by 2-dimensional echocardiography and with transflow curves obtained from apical views. For a total of 32 left-to-right shunt magnitudes obtained in 10 dogs, excellent correlations were found between ascending aortic Doppler and EM flow-meter values (r = 0.91, SEE [standard error of the estimate] = 0.11), between Doppler mitral valve flow and EM flow-meter main pulmonary artery flow values (r = 0.93, SEE = 0.52). This study demonstrates the accuracy of this 2-dimensional echocardiographic Doppler method for measuring pulmonary and systemic flows and their ratios in the presence of ventricular septal defects.