The purpose of this study was to assess the accuracy of a quantitative two-dimensional range-gated Doppler echocardiographic method for estimating systemic and pulmonary flows in an open-chest canine preparation with a variable-sized atrial level shunt mimicking an atrial septal defect. In addition, we also report our initial experience with 10 children who had isolated atrial septal defects and who had pulmonary and systemic flow ratios (QP:QS) determined by Doppler echocardiography simultaneously with green dye-shunt calculations in the cardiac catheterization laboratory. Ten mongrel dogs weighing 20 to 30 kg were anesthetized, intubated, and mechanically ventilated. Previously calibrated electronmagnetic flow probes were placed around the ascending aorta and main pulmonary artery, and an atrial level shunt was created by inserting one-half inch diameter cannulae into the left and right atrial appendages and connecting both cannulae to ¾/4 inch tubing that passed through a previously calibrated extracorporeal mechanical roller pump. This permitted quantitation as well as regulation of shunt size and direction. With each step-by-step variation in shunt magnitude, systemic and pulmonary flows were estimated by Doppler echocardiography and were matched to the simultaneous electromagnetic flowmeter recordings. Doppler-estimated systemic blood flow was obtained by imaging and recording Doppler flow velocities in the ascending aorta with the transducer positioned directly over the vessel. Doppler pulmonary flow was obtained by imaging the main pulmonary artery on the short-axis view and by determining flow velocity with the sample volume placed distal to the pulmonic valve. A total of 32 interatrial shunts were produced in the 10 dogs. Aortic flows as determined by electromagnetic flowmeter ranged from 0.4 to 3.0 1/min, pulmonary flows ranged from 0.8 to 4.7 1/min, and QP:QS ratios ranged from 0.9:1 to 5.5:1. Excellent correlations were found between values determined by Doppler echocardiography and by electromagnetic flowmeter for ascending aortic flow (r = .96, SEE = 0.19 1/min), pulmonary flows (r = .97, SEE = 0.28 1/min), and QP:QS ratios (r = .96, SEE = 0.28). In the 10 patients with isolated atrial septal defects, QP:QS ratios determined by dye curves ranged from 1.6:1 to 4.8:1. The linear correlation comparing QP:QS ratios determined by Doppler echocardiography with those obtained by catheterization demonstrated a correlation coefficient of .91 with an SEE of 0.3:1. Our study validates the accuracy of a twodimensional Doppler echocardiographic method for estimating pulmonary and systemic blood flows and their ratios in the presence of atrial level shunts.Circulation 69, No. 1, 80-86, 1984
Many methods are available for digital computation of the impulse response from indicator-dilution measurements representing input and output signals. In all instances, the only criterion for validity of the computation is comparison of the reconvolution of the computed impulse response and the input with the actual output. In this paper, a model mathematical system was constructed with a known impulse response; noise and time variation could be introduced independently or simultaneously in the input and the output data. Six methods for digital computation of the impulse response were applied to data from this system and to actual dye-dilution data. Precision of reconvolution did not assure that the computed response would resemble the actual response of the system. Some numerical considerations also significantly affected the digital computation of a valid response.
The purpose of this study was Vol. 69, No. 6, June 1984 in tracking changes in gradients within the same animal was also analyzed. MethodsSurgical technique in the animal preparation. Six mongrel dogs weighing 20 to 30 kg were anesthetized with intravenous sodium pentobarbitol (30 mg/kg), intubated, and ventilated with a standard volume respirator. After a median sternotomy, the pericardium of each dog was opened and the heart was exposed. The ascending aorta and the main pulmonary artery were dissected and cleaned of fat and adventitia and an appropriately sized, precalibrated electromagnetic flow probe (GouldStatham SP2204) was placed around the ascending aorta approximately 2 cm above the aortic valve to continuously monitor cardiac output. Catheter-tipped micromanometers (Millar) or fluid-filled catheters connected to strain-gauge transducers (Statham P231D) were placed in the right ventricle, pulmonary artery, and aorta to record pressures continuously. Umbilical tape (l/' inch) was sewn to the posterior rim of the pulmonary artery just above the valve anulus and progressively tightened to produce varying degrees of stenosis. After each degree of constriction of the pulmonary arterial band, the animal was allowed at least 2 min to stabilize and adapt to
We have implemented a consultant-extender system that enables community physicians, in cooperation with regional specialists, to deliver adjuvant chemotherapy to patients with node-positive breast cancer. The system employs computer-generated care protocol forms that indicate the data to be collected and the drug dose(s), with the appropriate rules for their administration. This continuous process of monitoring and modifying therapy assures protocol compliance and facilitates quality of care assessment. Seventy-three physicians throughout Alabama delivered appropriate chemotherapy at nearly 97% of 2612 visits by 195 patients. Disease-free intervals of 149 of those patients treated in a prospective clinical trial are indistinguishable from those of comparable patients treated largely within academic centers. This system provides a mechanism for decentralizing speciality care, incorporating community physicians into clinical trials, and improving continuing medical education techniques.
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