Suzana Horowitz

The mitral valve orifice method for noninvasive two-dimensional echo Doppler determinations of cardiac output.

We developed and validated a mitral valve orifice method for Doppler cardiac output determination. In 15 open-chest dogs, cardiac output was controlled and measured by a roller pump interposed between the right atrium and pulmonary artery as a right-heart bypass. Left heart flows were measured in the open-chest dog model by Doppler measurements at the mitral valve orifice and compared not only to volume flow measured by the roller pump, but to electromagnetic flow meters as well. The maximum mitral valve orifice area was measured off short-axis two-dimensional echocardiographic views by planimetry. The maximal orifice was then adjusted for its diastolic variation in size by calculating a ratio of mean-to-maximal mitral valve separation on a derived M-mode echocardiogram. Flow was sampled parallel to mitral valve inflow in a four-chamber plane. The multiplication of mean flow throughout the cardiac cycle by the mean mitral valve area after correction for diastolic size variation yielded a cardiac output determination that could be compared to the roller pump measurement. Fifty-two cardiac output determinations over roller pump values of 1–5 1/min yielded a high correlation between roller pump flows and Doppler (r = 0.97 + 0.23 1/min). Our study shows that the mitral valve orifice provides an accurate site for Doppler cardiac output measurements.

The effect of variations of pulsed Doppler sampling site on calculation of cardiac output: an experimental study in open-chest dogs.

We measured aortic flow by two-dimensional Doppler echocardiography in an open-chest dog model to examine how variations in Doppler sample volume length and position influence aortic hemodynamic flow calculations. Fourteen dogs underwent right-heart bypass, in which venous return from the venae cavae drained by gravity to a reservoir. A variable-speed roller pump returned the blood to the pulmonary artery, fixing left-sided cardiac input and output. Echo Doppler measurements were performed using a 3.5-MHz transducer placed directly on the aortic arch to determine internal aortic cross-sectional area. The transducer was then directed to image the aortic arch for Doppler velocity measurements and the various sampling sites were investigated. Doppler cardiac output could then be determined for each of the various sample volumes over a range of known roller pump settings. Doppler velocity was analyzed using fast Fourier transform spectral analysis. Mean velocity over the cardiac cycle was obtained by planimetry of the area under the Doppler velocity curve with a minicomputer. Doppler-derived determinations of cardiac output achieved a correlation of r = 0.98–0.99 to values obtained by the roller pump over a range of cardiac outputs from 0.75–5 1/min. The standard error of the estimate was 0.2 I/min. In this laminar flow model, there was no difference between the predictive accuracy of any of the sampling sites over the range of roller pump flows. Our study shows that Doppler velocity measurements can be used to quantify aortic flow over a clinically useful range and that variations of sample length and position did not produce significant differences in calculated flows.

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 Jne 9, 2017 http://ciajournals.org/ D ow nladed from

Validation of a Doppler echocardiographic method for calculating severity of discrete stenotic obstructions in a canine preparation with a pulmonary arterial band.

The purpose of this study was to develop an open-chest animal preparation to validate the accuracy of a two-dimensional Doppler echocardiographic method for estimating pressure drops across discrete stenotic obstructions. Six mongrel dogs underwent median sternotomy and catheters were placed in the right ventricle, distal main pulmonary artery, and aorta of each. A 1/8 inch umbilical tape was sewn to the posterior rim of the pulmonary artery just above the anulus and was progressively tightened to vary the degree of stenosis. Ultrasound and Doppler studies were performed with a 2.5 MHz phased-array unit with capabilities for pulsed or continuous-mode Doppler and real-time imaging. Peak systolic main pulmonary arterial flow velocities were recorded by Doppler echocardiography within the jet distal to the band from an oblique parasternal short-axis echocardiographic view and corrected for angle of incidence between the direction of Doppler sampling and the presumed direction of flow. Doppler velocities were converted to gradients with a simplification of the Bernoulli equation (gradient = 4 X maximal Doppler flow velocity2 ). Maximal Doppler-determined systolic pulmonary arterial velocities showed a good linear correlation with the 63 measured pressure drops (r = .95, SEE +/- 36.3 cm/sec). An excellent correlation was also found between Doppler-calculated and actual pressure gradients (r = .96, SEE +/- 7.26 mm Hg). Our results suggest that this Doppler method for measuring gradients across discrete stenotic obstructions may be quite accurate in clinical applications.

Prognostic value of left ventricular size measured by echocardiography in infants with total anomalous pulmonary venous drainage

Abstract Left ventricular size may be a determinant of survival in infants with total anomalous pulmonary venous drainage. Right and left ventricular size were measured by M-mode and 2-dimensional (2-D) echocardiography in 13 patients aged 1 day to 4 months (mean weight 4.3 ± 0.42 kg [standard error of the estimate]) who underwent surgery before age 4 months because of severe cyanosis or cardiac failure. Seven patients had venous drainage to a vertical vein, 4 had drainage to the right atrium, and 2 had drainage to the inferior vena cava. Patients were divided into 2 groups: survivors (Group A, n = 8) and nonsurvivors (Group B, n = 5). Death was not statistically related to pulmonary artery pressure, pulmonary venous obstruction, age, or weight at the time of surgery. Right and left ventricular sizes at end-diastole measured from M-mode traces and 2-D echocardiographic 4-chamber views were compared with those from 15 weight-matched control infants. On M-mode and 2-D echocardiography, nonsurvivors had significantly larger right ventricles and smaller left ventricular dimensions than did either control subjects or surviving patients with total anomalous pulmonary venous drainage. The ratio of right to left ventricular size on M-mode and 2-D echocardiography also differed among the 3 infant groups (p

Can Tracking of Contrast Echocardiographic Targets Be Used to Measure Intracardiac Flow Velocities

Recent studies suggest that the slopes of linearly moving echocardiographic contrast targets (microbubbles) can be used to predict flow velocities in the right heart. The purpose of this study was to assess the accuracy of velocities measured with contrast echocardiography by comparing them with those recorded with a previously calibrated quantitative range-gated 2-dimensional echocardiographic Doppler flow meter. Venous saline echocardiographic contrast injections and Doppler studies were performed in 10 patients, aged 6 months to 16 years, who had been operated on for lesions in the left side of the heart. Blood velocities were measured on a Doppler flow meter along the direction of flow in the main pulmonary artery just distal to the pulmonary valve in a short-axis plane. Immediately after the Doppler study, an M-mode echocardiogram of the pulmonary valve was derived from the same plane as that used for the preceding Doppler sample volume, passing through the pulmonary valve; 2 to 10 ml of normal saline solution was forcefully hand-injected through a previously positioned peripheral venous line and recorded on strip chart and videotape at a paper speed of 100 mm/s. Pulmonary flow velocities by contrast echocardiography were measured as the slopes of the moving contrast echocardiographic targets seen just beyond the pulmonary valve leaflets. Measurable microbubbles had to follow the constraints described in a previous study by Shiina et al. 3 Doppler velocities were read directly from the machine calibration marks (centimeters per second) recorded with the fast Fourier output. Instantaneous and peak velocities were determined at time-matched systolic points in cardiac cycles of identical R-R intervals. Significant but low level correlations were found between contrast echocardiography and Doppler instantaneous (r = +0.45) or peak (r = +0.11) systolic velocities. Our results suggest that while contrast echocardiographic microbubbles can be measured to yield a velocity, they do not behave like moving red blood cells that reflect ultrasound to produce a Doppler shift. Therefore, contrast echocardiography cannot be used reliably to measure flow velocities in the right heart.

146 LONG TERM LEFT VENTRICULAR POSTERIOR WALL ECHOCARDIO- GRAPHIC CHANGES IN DUCHENNE MUSCULAR DYSTROPHY

Cardiac pathology in Duchennes muscular dystrophy (DMD) is principally left ventricular posterior wall (LVPW) fibrosis. The aim of this study was to track long term LVPW echocardiographic (echo) changes in DMD. Echoes were recorded each 12 months from 19 boys with known DMD over 3 years and compared to controls. LVPW endo- and epicardium were digitized and % thickening and % thinning at standardized time intervals were determined; 15/19 had two-dimensional echoes. As previously reported, impaired diastolic relaxation was an early finding. The ratio of peak systolic LVPW to end diastolic LVPW was 2.06 (controls) to 1.83 (boys with DMD) (p<.01), but a given boys ratio was not predictive. All 19 had LVPW thickness, adjusted for body size, below the control mean (p<.01). The major finding was that two wall pattern groups emerged: Group I-LVPW thickness increased normally with time and body surface area but at a low percentile curve. Group II-LVPW decreased progressively and in 4, almost no systolic LVPW thickening was found. Two-dimensional echoes were studied for change in cavity size during contraction. All Group I patients had normal two-dimensional echoes. All Group II patients had abnormally decreased LV free wall contraction. Sequential abnormal findings in DMD patients are impaired LVPW relaxation, decreased LVPW thickness in systole and end diastole, and a contraction impairment imaged with two-dimensional echo.

145 THE EFFECT OF IONOTROPIC AGENTS ON THE ECHO IMAGED LEFT VENTRICULAR POSTERIOR WALL

The purpose of this investigation was to determine the influence of ionotropic agents upon systolic thickening and diastolic thinning of the left ventricular posterior wall. Two populations were investigated: #1--14 children with congenital cardiac disease who had echoes recorded at catheterization before and during isoproterenol infusion, and #II--8 boys with Duchennes muscular dystrophy who participated in a double-blind, placebo controlled, cross-over study of the effects of digoxin. All echoes were analyzed by digitizing left ventricular posterior wall endo- and epicardium and evaluating % systolic time and % diastolic time at standardized time intervals. No significant differences occurred when control and ionotropic group values were compared for either group at any percentage of systolic or diastolic time. Thus, the sequence of contraction and relaxation was unaltered by ionotropic agents. However, when wall thickness values at standardized time intervals were compared before and during administration of ionotropic agents, significantly greater (p<.01) systolic wall thickening was present at each time interval. A 15% mean additional systolic thickness occurred for isoproterenol and 10% mean increase occurred for digoxin. This investigation shows that ionotropic agents do not alter the shape of the systolic time or diastolic time curves but significantly change systolic contraction magnitude.