A two-dimensional Doppler echocardiographic method for calculation of pulmonary and systemic blood flow in a canine model with a variable-sized left-to-right extracardiac shunt.

The purpose of this study was to validate a two-dimensional range-gated Doppler echocardiographic method for measurement of pulmonary and systemic blood flow in a canine model with a surgically created extracardiac systemic-to-pulmonary shunt, the size of which could be varied. In five anesthetized open-chest dogs, a previously calibrated electromagnetic (EM) flowmeter was placed around the ascending aorta, and the femoral artery was dissected, cannulated, and connected to a previously calibrated roller pump. The return tubing from the roller pump was inserted into the main pulmonary artery to create a variable-sized systemic-to-pulmonary artery shunt. In this preparation with intact ventricular and atrial septa, pulmonary blood flow volume was measured as flow from the ascending aorta with the EM flowmeter probe; left-to-right shunt volume was measured from the calibrated roller pump flow, and systemic flow was measured by subtraction of roller pump flow from the EM flowmeter reading of the ascending aorta. In two additional dogs, a 16 mm diameter, 12 cm long Teflon graft was placed between the descending aorta and the main pulmonary artery to mimic more closely a patent ductus arteriosus. Flow through the shunt was measured with an EM flowmeter probe placed around the graft. Systemic and pulmonary flows were then calculated by a Doppler echocardiographic method from RR interval-matched beats and compared with simultaneously recorded EM flowmeter measurements from the ascending aorta, and left-to-right shunt flows to permit comparison of pulmonary and systemic flows and their ratios (QP:QS) by both methods. Doppler systemic flow was measured as systemic venous return at the right ventricular outflow tract. The size of the outflow tract and mean flow as a function of time were obtained by echocardiographic imaging and interrogation of the outflow tract from a short-axis view. Pulmonary blood flow could not be measured at the pulmonary artery because of high multidirectional velocities and spectral broadening of the flow curves similar to those obtained in children with patent ductus arteriosus. Therefore, pulmonary blood flow was measured as pulmonary venous return through the mitral valve. The mitral orifice was measured from a short-axis view, and Doppler flow curves were recorded from the apical four-chamber view. For 26 left-to-right shunts, excellent correlations were obtained between Doppler echocardiographic andEM flowmeter measurements of pulmonary flows (range 1.2 to 7.7 1/min; r = .99, SEE = + 0.16 1/min), systemic flows (range 0.6 to 5.7 1/min; r = .99, SEE = ± 0.13), and QP:QS ratios (range 0.9:1 to 4.2:1; r = .96, SEE = ± 0.21:1). Our study validates the accuracy of this Doppler echocardiographic method to measure pulmonary and systemic flows and their ratios in the presence of extracardiac aortic-to-pulmonary artery shunts. Circulation 68, No. 2, 437-445, 1983. From the Department of Pediatrics, University of Arizona, Health OUR PREVIOUS STUDIES and those of other inSciences Center, Tucson, and the Department of Pediatrics, University vestigators have demonstrated that two-dimensional of Groningen, Groningen, The Netherlands. Supported in part by a grant from the Jan Kornelis de Cock FoundaDoppler echocardiographic methods are accurate for tion, The Netherlands. Address for correspondence: Lilliam Valdes-Cruz, M.D., Departnoninvasive calculation of cardiac flows in the intact ment of Pediatrics (Pediatric Cardiology), University of California San circulation in man. 1-10 Our own work has also shown Diego University Hospital, CTF B102, 225 West Dickinson St., San that Doppler echocardiography accurately measures Diego, CA 92103. Received Feb. 4, 1983; revision accepted April 25, 1983. pulmonary and systemic flows and their ratios, even in Vol. 68, No. 2, August 1983 437 by gest on N ovem er 8, 2017 http://ciajournals.org/ D ow nladed from