Quantification of left to right atrial shunts with velocity-encoded cine nuclear magnetic resonance imaging.

OBJECTIVES. The purpose of this study was to evaluate the ability of velocity-encoded nuclear magnetic resonance (NMR) imaging to quantify left to right intracardiac shunts in patients with an atrial septal defect. BACKGROUND. Quantification of intracardiac shunts is clinically important in planning therapy. METHODS. Velocity-encoded NMR imaging was used to quantify stroke flow in the aorta and in the main pulmonary artery in a group of patients who were known to have an increased pulmonary to systemic flow ratio (Qp/Qs). The velocity-encoded NMR flow data were used to calculate Qp/Qs, and these values were compared with measurements of Qp/Qs obtained with oximetric data derived from cardiac catheterization and from stroke volume measurements of the two ventricles by using volumetric data from biphasic spin echo and cine NMR images obtained at end-diastole and end-systole. RESULTS. Two independent observers measured Qp/Qs by using velocity-encoded NMR imaging in 11 patients and found Qp/Qs ranging from 1.4:1 to 3.9:1. These measurements correlated well with both oximetric data (r = 0.91, SEE = 0.35) and ventricular volumetric data (r = 0.94, SEE = 0.30). Interobserver reproducibility for Qp/Qs by velocity-encoded NMR imaging was good (r = 0.97, SEE = 0.20). CONCLUSIONS. Velocity-encoded NMR imaging is an accurate and reproducible method for measuring Qp/Qs in left to right shunts. Because it is completely noninvasive, it can be used to monitor shunt volume over time.     

Calculation of intracardiac shunt using Doppler echocardiography

The purpose of this study was to assess the accuracy of a quantitative two-dimensional Doppler echocardiographic method for estimation of intracardiac shunts. The ratio of pulmonary to systemic flow (Qp/Qs) was evaluated by duplex Doppler echocardiography in 20 patients with various intracardiac shunts. Right and left ventricular stroke volumes (RSV, LSV) were determined from the recordings of ejection blood flow velocity and diameter at the level of the pulmonary and aortic orifices in each ventricular outflow tract. The ratio RSV/LSV, determined by duplex Doppler echocardiography, was compared with Qp/Qs by oxymetry. The Doppler echocardiograms were of sufficient quality for shunt calculation in 15/20 patients (75%). The RSV/LSV for ten normal subjects was 0.99 +/- 0.05 (mean +/- SD), whereas the RSV/LSV for 15 patients with intracardiac shunts, 2.6 +/- 0.5, was significantly higher than that for normal subjects (p less than 0.01). In 12/15 patients, the Doppler study estimated the severity of intracardiac shunting correctly. The presence of complex anatomic situations, a wide pulmonary artery or significant semilunar regurgitation seem to have a negative impact on the Doppler echocardiographic shunt calculation. Our findings indicate that, with a few limitations, the Doppler index RSV/LSV is clinically useful in the estimation of the magnitude of the shunt flow in patients with intracardiac shunts.     

Echocardiographic evaluation of the significance of shunt in secondary communications and in partial abnormal pulmonary venous returns]

Although echocardiography has been useful in diagnosing significant left-to-right shunts at the atrial level, few studies using this technique to quantitate shunt size have been performed. Echocardiograms and hemodynamic data from 28 patients, ages 15 to 58 (mean : 30 years) were reviewed. Twenty patients had isolated atrial septal defects (ASD), 6 patients has associated partial pulmonary venous returns (PPVR) and 2 patients had isolated PPVR. Echocardiograms in the supine position were performed within 24 hours preceding cardiac catheterization. The presence or absence of paradoxical septal motion was noted and right ventricular diameter index (RVDE : right ventricular diameter/body surface area) was calculated. Hemodynamic parameters studied included pulmonary to systemic flow ratio (Qp/Qs) determined by oxymetry, right ventricular pressure (RVP) and pulmonary resistance (PR). One patient with a Qp/Qs of 1.3 had normal septal motion. Type A paradoxical septal motion was noted in 22 cases, type B in 5 cases. For these 27 patients, the average RVDI was 2.42 (range 1.45 to 3.7), Qp/Qs ranged from 1.5 to 5 (mean : 2.45), RVP from 23 to 71 mmHg (mean : 39) and PR from 0.6 to 4 units (mean : 1.79). A very strons correlation between RVDI and Qp/Qs was observed from equation Qp/Qs : 1.19 RVDI-0.43 with a standard error of 0.4. This relationship was not altered by either RVP or PR values, which also had no apparent correlation with RVDI. This study indicates that echocardiographic measurement of RVDI is a reliable and non-invasive method of evaluating the size of left to right shunts at the atrial level.     

Quantification of pulmonary and systemic blood flow by magnetic resonance velocity mapping in the assessment of atrial-level shunts

The objective of this study was to assess the feasibility and accuracy of magnetic resonance (MR) velocity mapping to calculate pulmonary-to-systemic flow ratio (Qp : Qs) in patients with a suspected or diagnosed atrial-level shunt. During a one-year period, all patients referred to our department for further evaluation of an atrial-level shunt underwent the same imaging protocol. Multiphase-multisection gradient-echo MR image sets of the heart were acquired to measure left and right ventricular stroke volumes for validation. Ascending aorta and main pulmonary artery volume flow were measured with MR velocity mapping. Qp : Qs ratios were calculated from both stroke volume data and flow data. Twelve patients, including 6 children, were studied. Six patients had an established diagnosis of atrial septal defect, and the other 6 patients were suspected to have an atrial-level shunt. Measurements of left and right ventricular stroke corresponded closely with those of aortic (r=0.98) and pulmonary flow (r=0.99) respectively, and Qp : Qs flow ratios agreed with stroke volume ratios (r=0.92). In 5 patients with a suspected shunt, the diagnosis could be rejected. Shunts were demonstrated in the other 7 patients. MR velocity mapping offers an accurate method to measure aortic and pulmonary artery volume flow that can be useful in the evaluation of atrial-level shunts, in order to establish a definite diagnosis and/or to quantify the Qp : Qs ratio.     

Pulse Densitometer Indocyanine Green Dilution Curves: A Simple Applicable and Accurate Method for Determination of Cardiac Shunts

Objective. Adequate hemodynamic evaluation is crucial in the management of patients with congenital heart disease. Although non‐invasive diagnostic tools have reduced the need for invasive procedures, cardiac catheterization is still mandatory for absolute quantification of pressures, flows and vascular resistances in selected patients. We therefore investigated the feasibility of a new technique, non‐invasive pulse densitometry (PD) in patients with intracardiac shunts and compared its results with the established standards: cuvette densitometry (CD) and oximetry (OX). Design. Measurement method comparison study. Outcome measure. In 12 patients with intracardiac shunt, dye dilution curves, using both pulse and cuvette densitometry, were recorded and oximetry was performed. Left‐to‐right shunt expressed as percentage of pulmonary blood flow Qp, was calculated from dye dilution and oximetry. In 4 patients with atrial septal defect, dye dilution curves were also recorded after closure of the defect with a device. Results. The mean difference ± SD between the shunt derived from PD and CD was 2.8 ± 10.0% of Qp, 95% confidence interval ?2.5 to 8.2. (Shunt‐PD vs. Shunt‐CD was 32.3 ± 23.9% vs. 29.5 ± 23.9% of Qp resp., n = 16). The mean difference ± SD between the shunt derived from PD and OX was 0.8 ± 9.8% of Qp, 95% confidence interval ?5.4 to 7.0 (Shunt‐PD vs. Shunt‐OX was 41.5 ± 20.3% vs. 40.7 ± 19.7% of Qp resp., n = 12). Conclusion. Transcutaneous recording of dye dilution curves with a pulse dye densitometer allows easy and accurate quantification of intracardiac left‐to‐right shunt flows over a wide range in both children and adults with congenital heart diseases.     

Quantification of left to right cardiac shunts by multiple deconvolution analysis

A new method for quantification of left to right cardiac shunts was studied in 17 patients scheduled for cardiac catheterization who had also undergone radionuclide angiocardiography. The observed pulmonary transit curve was deconvoluted in two different ways: (1) by the superior vena caval (“bolus”) time-activity curve, to yield the deconvoluted pulmonary transit curve, which represented the theoretical pulmonary transit curve with a perfect bolus injection, and (2) by the right ventricular time-activity curve, to yield the pulmonary transfer function, which represented the theoretical pulmonary transit curve with a perfect bolus injection and with no intracardiac shunts. The pulmonary transfer function was superimposed on the deconvoluted pulmonary transit curve, and the area A under it obtained. The pulmonary transfer function was then subtracted from the deconvoluted pulmonary transit curve. The pulmonary transfer function was scaled to fit the resulting shunt recirculation peak in the difference curve, and the area B under this scaled pulmonary transfer function obtained. Shunt size was quantified as the pulmonary (QP) to systemic (QS) flow ratio QP/QS = A/(A − B). The method correlated closely with oximetry (r = 0.93). Use of this multiple deconvolution analysis technique provides accurate shunt quantification and reduces subjective operator decisions.     

Radionuclide evaluation of circulatory shunts

With first-pass radionuclide angiography, it is possible to visualize sequentially the cardiovascular structures and to obtain computer-generated time-activity curves for regions of interest over these structures. Analysis of these curves permits the detection, localization, and quantitation of intracardiac shunts and shunts between the great arteries. The authors present the formulae used for the quantitative analysis and discuss clinical applications.     

Assessment of the sensitivity of hydrogen inhalation in the detection of left-to-right shunting

For the detection of left-to-right intracardiac shunting, the oximetric and standard indocyanine green techniques are relatively insensitive, in that neither can reliably detect a shunt with a ratio of pulmonary to systemic flow (Qp/Qs) less than 1.3 (percentage shunt, 23%). Although the hydrogen inhalation method is said to be much more sensitive in this regard, no previous study has measured its sensitivity. Accordingly, in 15 patients (4 men, 11 women, aged 38 to 67 years) without intracardiac shunting, hydrogen inhalation was performed 1) without and 2) with an artificially created femoral arteriovenous shunt of known size, and cardiac output was measured by thermodilution. For the 15 subjects with cardiac outputs of 3.64 to 8.10 liters/min, shunts of 22 to 248 ml/min were created, so that the shunts ranged from 0.5% to 3.3%. Hydrogen inhalation detected all shunts greater than or equal to 1.3% (Qp/Qs greater than or equal to 1.01). Of the 10 shunts less than 1.3%, it detected 5, with the smallest being 0.7%. Thus, the hydrogen inhalation technique is extremely sensitive in identifying the presence of left-to-right shunting, far more sensitive than the oximetric and standard indocyanine green methods.     

Quantification of left to right shunt in atrial septal defect using systolic time intervals derived from pulsed Doppler velocimetry.

Systolic time intervals derived from Doppler velocimetry measurements were used instead of direct pulmonary to systemic flow ratio measurements in adults with atrial septal defect to quantify left to right atrial shunts. Thirteen normal subjects and 25 patients with uncomplicated atrial septal defect confirmed by cardiac catheterisation were studied. The pulmonary to systemic flow ratio (Qp:Qs) expressing the shunt size was determined by the Fick method; in normal subjects the Qp:Qs ratio was assumed to be equal to 1.0. The pulsed Doppler analogue velocity recording of flow in the pulmonary artery and the ascending aorta was taken as indicating the ejection time of each ventricle and the Q wave of the electrocardiogram as indicating the onset of systole. From these measurements the ratios of the pre-ejection periods to the ejection times (haemodynamic ratio) were calculated for each ventricle and the ratios of each variable (pre-ejection period, ejection time, and haemodynamic ratio) were calculated for both ventricles. Significant differences were found between the normal subjects and the patients with atrial septal defect for all these ratios. When the Doppler findings and the Fick measurements of Qp:Qs were compared the best linear correlation coefficient was for the left to right haemodynamic ratio. It is concluded that the use of a ratio involving several variables, such as the pre-ejection period and the ejection time for both ventricles, improves the reliability of this method, which appears to be applicable in adults.     

Quantification of left to right shunt in atrial septal defect using systolic time intervals derived from pulsed Doppler velocimetry

Systolic time intervals derived from Doppler velocimetry measurements were used instead of direct pulmonary to systemic flow ratio measurements in adults with atrial septal defect to quantify left to right atrial shunts. Thirteen normal subjects and 25 patients with uncomplicated atrial septal defect confirmed by cardiac catheterisation were studied. The pulmonary to systemic flow ratio (Qp:Qs) expressing the shunt size was determined by the Fick method; in normal subjects the Qp:Qs ratio was assumed to be equal to 1.0. The pulsed Doppler analogue velocity recording of flow in the pulmonary artery and the ascending aorta was taken as indicating the ejection time of each ventricle and the Q wave of the electrocardiogram as indicating the onset of systole. From these measurements the ratios of the pre-ejection periods to the ejection times (haemodynamic ratio) were calculated for each ventricle and the ratios of each variable (pre-ejection period, ejection time, and haemodynamic ratio) were calculated for both ventricles. Significant differences were found between the normal subjects and the patients with atrial septal defect for all these ratios. When the Doppler findings and the Fick measurements of Qp:Qs were compared the best linear correlation coefficient was for the left to right haemodynamic ratio. It is concluded that the use of a ratio involving several variables, such as the pre-ejection period and the ejection time for both ventricles, improves the reliability of this method, which appears to be applicable in adults.     

Quantitative radionuclide angiocardiography: Detection and quantitation of left to right shunts

In 105 patients detection and quantitation of left to right shunts was performed using quantitative radionuclide angiocardiography. The radionuclide angiocardiograms were acquired and analyzed by a gamma camera interfaced to a digital computer system. Pulmonary to systemic flow ($\text{Qp}\text{Qs}$) ratios were calculated by analysis of pulmonary time-activity histograms using a gamma variate model. All patients were studied with cardiac catheterization, left ventricular angiocardiography and radionuclide angiocardiography. The radionuclide method allowed precise detection and quantitation of left to right shunts with a $\text{Qp}\text{Qs}$ ratio of 1.2 to 3.0. There was good agreement between the $\text{Qp}\text{Qs}$ ratio calculated by oximetry at cardiac catheterization and radionuclide angiocardiography (r = 0.94). The information gathered with this nontraumatic method appears sufficiently reliable to be used in the management of patients.     

Variability of right-sided cardiac oxygen saturations in adults with and without left-to-right intracardiac shunting

In many catheterization laboratories and intensive care units, oxygen saturation of single blood specimens is measured from the superior vena cava (SVC), right atrium (RA) and pulmonary artery (PA) during right-sided catheterization, but variability of such single measurements in adults with and without intracardiac left-to-right shunting has not been assessed. Oxygen saturation of SVC, RA and PA single blood samples were measured in 1,031 adults (524 men, 507 women, aged 50 +/- 13 years [mean +/- standard deviation SD]). In the 980 patients without shunting, differences in saturation between SVC and RA, RA and PA and SVC and PA were 3.9 +/- 2.4%, 2.3 +/- 1.7%, and 4.0 +/- 2.5%, respectively, so that the normal limits of variability (mean +/- 2 standard deviations) for these saturation differences were 8.7%, 5.7% and 9.0%, respectively. Of the 51 patients with left-to-right shunting, these limits of variability of oxygen saturation correctly identified 46 (90%), and the 5 with shunting whose saturation differences were below these limits had small shunts (Qp/Qs ratios of 1.9 or less). Thus, assessment of oxygen saturation from single blood specimens obtained from the SVC, RA and PA offers excellent sensitivity (more than 90%), specificity (94 to 95%) and predictive accuracy (94% or more) in identifying patients with and without intracardiac left-to-right shunting. The sensitivity of these limits is especially high in patients with large shunts (Qp/Qs of 2 or more).     

Determination of left to right shunt by thermodilution in patients with ventricular septal defect

A modified thermodilution technique was used to determine the quantity of shunt in patients suffering from congenital heart disease with a left to right shunt. In our modification, the thermistor was placed within the pulmonary artery and an indicator was injected into both sides of the heart. In a series of 33 cardiac catheterizations in children (1-17 years) with ventricular septal defect (VSD), pulmonary blood flow (Qp), systemic blood flow (Qs) and the ratio of Qp to Qs (Qp/Qs) were determined by this and ordinary oximetry (Fick) methods. Correlation coefficients between indexes obtained by these methods were 0.54 (Qp), 0.78 (Qs), and 0.75 (Qp/Qs). The estimates of Qp and Qp/Qs obtained by thermodilution were smaller than those obtained by the Fick method. This modification of thermodilution is simple, rapid, and useful in clinical practice.     

Rapid method for determination of shunt ratio using a thermodilution technique

A new technique using thermodilution by which shunt ratio can be rapidly and conveniently determined in patients with left-to-right intracardiac shunts is described. A flow-directed balloon-tip thermistor catheter was positioned in the pulmonary artery to measure cardiac output in 20 patients with left-to-right intracardiac shunts. Shunt ratio measured by the Fick technique (Qp:Qs_F) varied between 1.3:1 and 3.6:1. Early recirculation was seen on the downslope of the thermodilution curves (TC). The first-pass curve before the point of early recirculation was extrapolated to the baseline and the area inscribed by this portion of the TC (A) was measured by planimetry. The area inscribed by the entire TC (A + B) was also measured by planimetry. Shunt size was determined by calculating the ratio (A + B):A. Shunt ratio determined by this technique (Qp:Qs_Th) correlated well with Qp:Qs_F (r = 0.89). The thermodilution technique provides a simple, rapid, and accurate method for determining the magnitude of left-to-right intracardiac shunts.     

Comparison of exercise capacity evaluated by cardiopulmonary exercise test and hemodynamic parameters in patients with atrial septal defect]

We evaluated the maximal exercise tolerance using cardiopulmonary exercise testing, and investigated the relation of the hemodynamic parameters such as mean pulmonary artery pressure (PAm) and pulmonic-to-systemic flow ratio (Qp/Qs) to exercise tolerance in 18 adult patients consecutively. All the patients had atrial septal defect (ASD). Maximal oxygen uptake (VO2 max) averaged only 21.6 +/- 5.6 ml/min/kg and 63.5 +/- 16.2% of the predicted values (VO2max). And anaerobic threshold averaged 12.5 +/- 2.3 ml/min/kg and 56.7 +/- 12.4% of the predicted values. There were 2 patients who had marked pulmonary hypertension (PH, PAm more than 44 mmHg). Maximal exercise tolerance of these patients was severely impaired, and %VO2max was only 45.9% and 46.2% respectively. In patients without PH (PAm less than 20 mmHg), however %VO2 max ranged widely from 100.3 to 44.7% and PAm correlated with %VO2max weakly (r = -0.53, p less than 0.05). But there was a significant inverse relationship between Qp/Qs and %VO2max(r = -0.85, p less than 0.01). In 16 patients without PH, maximal O2-pulse during exercise was also inversely correlated with Qp/Qs (r = -0.76, p less than 0.01). The relation between PAm and %VO2max suggests that afterload on the right ventricle may be an important determinant of exercise capacity in patients with PH. And the relation between Qp/Qs and %VO2max or Qp/Qs and % maximal O2-pulse suggests that Qp/Qs may also be a very important determinant factor of exercise capacity in patients without PH.     

Quantification of intracardiac shunts by gold-195m, a new radionuclide with a short half life

Gold-195m, a radionuclide with a short half life (30.5 s) was used to quantify left to right intracardiac shunts. The results of this method were compared with those obtained with technetium-99m, a method that was validated against oximetry. In five patients the pulmonary to systemic flow ratio (greater than 3:1) obtained by both radionuclides indicated that the level of shunting was too high to be measured accurately. In one patient fragmentation of the bolus meant that no satisfactory gamma fit could be obtained. In the remaining 16 patients there was no significant difference between two successive 195mAu studies. The agreement between 99mTc results and 195mAu results was excellent. Oxygen administration, straight leg raising exercise, and the use of oblique projections did not affect the values of the pulmonary to systemic flow ratio. The technique of quantification of intracardiac shunts by 195mAu gives reproducible and accurate results and the low radiation dose means that it is suitable for use in children with suspected left to right shunts.     

Quantification of intracardiac shunts by gold-195m, a new radionuclide with a short half life.

Gold-195m, a radionuclide with a short half life (30.5 s) was used to quantify left to right intracardiac shunts. The results of this method were compared with those obtained with technetium-99m, a method that was validated against oximetry. In five patients the pulmonary to systemic flow ratio (greater than 3:1) obtained by both radionuclides indicated that the level of shunting was too high to be measured accurately. In one patient fragmentation of the bolus meant that no satisfactory gamma fit could be obtained. In the remaining 16 patients there was no significant difference between two successive 195mAu studies. The agreement between 99mTc results and 195mAu results was excellent. Oxygen administration, straight leg raising exercise, and the use of oblique projections did not affect the values of the pulmonary to systemic flow ratio. The technique of quantification of intracardiac shunts by 195mAu gives reproducible and accurate results and the low radiation dose means that it is suitable for use in children with suspected left to right shunts.     

超声测量肺循环阻力和体循环阻力比值

探讨超声测量肺循环阻力和体循环阻力比值（ＰＶＲ／ＳＶＲ）的方法。超声测量４３例先天性心脏病患儿左、右室射血前期（ＬＰＥＰ,ＲＰＥＰ）、射血期（ＬＥＴ,ＲＥＴ）和加速期（ＬＡＴ,ＲＡＴ）,同时测量主、肺动脉血流量（Ｑｓ,Ｑｐ）。进而计算ＲＰＥＰ：Ｑｐ、ＲＰＥＰ：ＥＴ：Ｑｐ、ＲＰＥＰ：ＡＴ：Ｑｐ、ＲＰＥＰ：Ｑｐ／ＬＰＥＰ：Ｑｓ、ＲＰＥＰ：ＥＴ：Ｑｐ／ＬＰＥＰ：ＥＴ：Ｑｓ和ＲＰＥＰ：ＡＴ：Ｑｐ／ＬＰＥＰ：ＡＴ：Ｑｓ。结果：超声测量ＲＰＥＰ：Ｑｐ、ＲＰＥＰ：ＥＴ：Ｑｐ和ＲＰＥＰ：ＡＴ：Ｑｐ与心导管测量的ＰＶＲ／ｍ２比较,ｒ分别为０．６６、０．６５和０．７５。超声测量ＲＰＥＰ：Ｑｐ／ＬＰＥＰ：Ｑｓ、ＲＰＥＰ：ＥＴ：Ｑｐ／ＬＰＥＰ：ＥＴ：Ｑｓ和ＰＲＥＰ：ＡＴ：Ｑｐ／ＬＰＥＰ：ＡＴ：Ｑｓ与心导管测量ＰＶＲ／ＳＶＲ比较,ｒ分别为０．７８、０．７８和０．８９。其中ＲＰＥＰ：ＡＴ：Ｑｐ／ＬＰＥＰ：ＡＴ：Ｑｓ与ＰＶＲ／ＳＶＲ相关最好。超声测量ＲＰＥＰ：ＡＴ：Ｑｐ／ＬＰＥＰ：ＡＴ：Ｑｓ能较准确地估测ＰＶＲ／ＳＶＲ。     

Accuracy of Doppler echocardiography in quantification of left to right shunts in adult patients with atrial septal defect

In previous experimental and pediatric studies, the ratio of pulmonary to systemic flow (Qp/Qs) was accurately estimated by Doppler echocardiography in various cardiac shunt lesions. The purpose of this study was to assess the accuracy of pulsed Doppler echocardiography in determining the magnitude of shunt flow in adult patients with an ostium secundum type atrial septal defect. In 32 patients with high quality echocardiograms and excellent Doppler signals, blood flow was measured in the right and left ventricular outflow tract by Doppler echocardiography. In 16 patients without heart disease, the correlation (r) between systemic (Qs) and pulmonary (Qp) blood flow was 0.96 (SEE = 0.417 liter/min, y = 1.05x - 0.21) and the mean Qp/Qs ratio was 1.01 +/- 0.09. In 16 patients with an atrial septal defect, the Qp/Qs ration measured by oximetry ranged from 1.34 to 4.61 and by pulsed Doppler echocardiography from 1.31 to 4.46 (p = NS). In these 16 patients, the correlation between the Qp/Qs ratio determined by oximetry and pulsed Doppler echocardiography was significant (r = 0.82, SEE = 0.54). In the total group of 32 patients, the correlation was stronger (r = 0.93, SEE = 0.37). Systematic differences between the invasive and noninvasive shunt calculations did not occur. Thus, in adult patients with an atrial septal defect of the secundum type and high quality echocardiograms, the magnitude of left to right shunt can be accurately assessed by pulsed Doppler echocardiography. In the absence of pulmonary hypertension, pulsed Doppler echocardiography provides precise information for the decision to undertake conservative or operative treatment.     

Transatrial septal velocity measurement by Doppler echocardiography in atrial septal defect: correlation with Qp:Qs ratio

Right atrial velocities measured perpendicular to the atrial septum by Doppler echocardiography in patients with atrial septal defects (ASD) have a discernible morphology that may bear a relation to shunt magnitude. The integral of the right atrial Doppler waveform was compared with shunt magnitude measured at cardiac catheterization or nuclear shunt scan in 17 ASD patients. For control subjects, the mean right atrial velocity was 15 +/- 4 cm/s (+/- standard deviation) and that for ASD patients was 41 +/- 11 cm/s (p less than 0.001). Doppler pulmonary-to-systemic flow ratio (Qp:Qs) correlated with catheterization Qp:Qs ratio (n = 9, r = 0.85, SEE = 0.27) and with nuclear Qp:Qs ratios (n = 8, r = 0.60, SEE = 0.51). Mean transatrial septal velocity in ASD patients correlated with catheterization Qp:Qs ratio (n = 9, r = 0.8, SEE = 6.0) and with simultaneous Doppler Qp:Qs ratio (n = 16, r = 0.89, SEE = 4.9, y = 16.2 +/- 8.3). Although Qp:Qs ratio can be approximated by measuring pulmonary and systemic flow by Doppler echocardiography in many ASD patients, this newly described method allows estimation of Qp:Qs ratio. It is useful when these more conventional measurements cannot be performed because of turbulence or when inadequate imaging prevents Doppler pulmonary to systemic flow measurement.