Electrocardiographic ST segment depression and clinical function in children with Fontan circulation.

Previous studies noted that Fontan patients have electrocardiographic ST depressions during exercise tests and on 24-hour ambulatory electrocardiographic (ECG) monitoring. This study investigated whether the ST depressions were correlated to clinical function (NYHA Functional Classification). Forty-five children in two groups were examined--15 patients with Fontan circulation and 30 with a structurally normal heart, matched for sex, height, and weight. Clinical and echocardiographic examinations were performed. The clinical state was defined as NYHA functional classes I-IV. All 45 children underwent 24-hour ECG and an analysis of ST changes was performed, with ST segment depression > 0.20 mV at ST 60 regarded as significant. Twelve of 15 patients had significant 24-hour ECG ST depressions; in 9 of 12 patients these occurred on more than one occasion. Comparing 24-hour ECG recordings from patients in NYHA I with patients in NYHA II or III showed a significant difference in depth (p = 0.0023), duration (p = 0.0016), and number of ST depressions (p = 0.0001). None of the matched healthy children showed ST depressions. Repeated ST analysis on 24-hour ECG shows that the ST depressions seem to be correlated to functional status and this may be a useful tool in clinical praxis.

Electrocardiographic ST-segment depression in children with fontan circulation.

Despite successful operation, many patients palliated with a Fontan-type procedure continue to show effort limitation. We previously observed that these children showed electrocardiographic ST depression during exercise tests. The purpose of the study was to investigate whether electrocardiographic ST depression is a common finding in children with Fontan circulation. Forty-two children in two groups were examined: group A consisted of 14 patients who had all undergone a modified Fontan procedure, and group B consisted of 28 children with a structurally normal heart, matched for length, weight and gender to group A. Complete echocardiographic examinations were performed in all patients and controls. All 14 patients and all 28 healthy children underwent standard 24 h ambulatory electrocardiographic monitoring. All the recordings were analysed by a PC-based Holter system where an analysis of ST changes was performed. Seven patients and 14 matched healthy children were exercised on bicycle ergometers. Four patients and eight matched healthy children underwent exercise testing by walking/running a treadmill. Ten of 13 patients analysed had significant ST depressions on ambulatory electrocardiogram (>0.20 mV). Three of the 10 patients with ST depression were on digoxin. Three patients showed depressions of the ST segment in the electrocardiogram during exercise, with a maximal depression of 0.20-0.35 mV. None of the 28 matched healthy children showed electrocardiographic ST depression on the ambulatory 24 h ECG. These findings indicate that ST depression in daily activity is a common finding in children with Fontan circulation.

The abnormal contralateral atrioventricular valve in mitral and tricuspid atresia in neonates: An echocardiographic study.

Abnormalities of the mitral valve (MV) or the tricuspid valve (TV) morphology and/or function in patients with functional single ventricle may result in early morbidity and death. The purpose of this study was to determine the incidence of contralateral atrioventricular valve (AVV) pathologies in mitral valve atresia (MA) and tricuspid valve atresia (TA). We retrospectively reviewed the echocardiographic data of 50 neonates with MV and 20 with TA. Appearance of the papillary muscles, chordae tendinae, and valve leaflets was assessed. AVV regurgitation was semiquantitated by color-flow Doppler and the AVV annulus diameter was measured and indexed to body surface area. MV abnormalities were found in 9 of 20 (45%) of patients with TA. The MV was myxomatous in 9 patients, the leaflets were redundant in 5 patients, and prolapsing occurred in 4 patients. Mild regurgitation was found in 2 patients. In 18 of 20 (90%) patients MV annulus size was larger than 95% of predicted normal values. TV abnormalities were found in 12 of 50 (24%) patients with MA. The TV was myxomatous in 4 patients, prolapsing in 2, and redundant in 3, and moderate TV regurgitation was found in 3 patients. In 29 of 50 (58%) patients TV annulus size was larger than 95% of predicted normal values. Contralateral AVV abnormalities in tricuspid and mitral valve atresia are common and should be assessed carefully before surgical procedures.

Late fenestration closure in the hypoplastic left heart syndrome: comparison of hemodynamic changes.

BACKGROUND AND OBJECTIVES: Although survival of patients with the hypoplastic left heart syndrome treated by staged surgical palliation has improved, hemodynamic data after fenestrated Fontan operation and after fenestration closure have not been reported in this patient population. We sought to describe the hemodynamic status of these patients at cardiac catheterization performed for the purpose of fenestration closure and to compare these data with data from contemporary patients with other forms of univentricular heart. METHODS AND RESULTS: Hemodynamic responses to fenestration closure during cardiac catheterization were reviewed in 40 consecutive patients, including 20 with the hypoplastic left heart syndrome and 20 with other forms of univentricular heart defects. Hemodynamics before fenestration closure (arterial saturation and pressure, Fontan baffle saturation and pressure, pulmonary capillary wedge pressure, systemic arteriovenous oxygen content difference, and right-to-left shunt fraction) were nearly identical between the two groups. Significant (p < 0.05) changes after fenestration closure included increases in arterial saturation (9%), mean arterial pressure (3 mm Hg), and baffle pressure (1 mm Hg) and arteriovenous oxygen content difference (18 ml/L), with near elimination of right-to-left shunting. Cardiac output decreased by 21% and systemic oxygen transport by 13%, with no differences between the two patient groups. Mean baffle pressures were <17 mm Hg in 32 patients (80%). CONCLUSIONS: Hemodynamics after fenestrated Fontan operation and responses to fenestration closure in patients with the hypoplastic left heart syndrome were remarkably similar to that in patients with other univentricular heart defects.

Pulmonary venous blood flow pattern in patients with univentricular hearts following total cavo-pulmonary connection.

The objective of the study was evaluation of the pulmonary venous blood flow (PVF) pattern and the influence of ventricular function and atrioventricular valve regurgitation on this flow in patients with univentricular hearts post total cavo-pulmonary connection (TCPC). Transthoracic or transoesophageal echocardiographic studies were performed in 24 children with normal hearts (group A) and in 24 patients with univentricular hearts (group B). Ventricular function and atrioventricular valve regurgitation was semiquantitatively assessed. Systolic/diastolic maximal velocities and velocity time integrals (VTI) were measured from PVF tracings. Ejection fraction was measured by radionuclide angiography in 11 patients. Twelve patients underwent heart catheterization and angiography. In group B the PVF showed a biphasic flow velocity curve. The systolic integrals were smaller and the diastolic integrals were larger than in group A (6.4 vs. 13.0 cm, P = 0.0001, and 13.9 vs. 10.0 cm, P = 0.005). The pulmonary venous systolic flow fraction in 13 patients with an open fenestration and/or atrioventricular valve regurgitation grade 2-3 was significantly lower than in those 11 patients without fenestration and none/small regurgitation (0.19 vs. 0.40, P = 0.05). In conclusion, the PVF pattern in children with univentricular hearts pallitated with TCPC is similar to the PVF pattern found in individuals with biventricular hearts showing a biphasic flow velocity curve despite the absence of pulsatile pulmonary artery flow. The PVF in patients with TCPC-palliated univentricular hearts is influenced by atrioventricular valve regurgitation and fenestration flow.

Left ventricular stroke work in mitral regurgitation: an animal experimental study.

BACKGROUND AND AIMS OF THE STUDY: Most studies on mitral regurgitation have focused on evaluating the regurgitant volume. The effects of mitral regurgitation and its associated cardiac workload on left ventricular function and mechanics may be equally important both in assessing the impact of regurgitation as well as in planning and evaluating therapy. The present study was undertaken to investigate the interrelationships of the regurgitant volume, hemodynamics and left ventricular work in an experimental animal model of chronic mitral regurgitation in which the regurgitant volume could be measured directly with electromagnetic flow probes. METHODS: A total of 21 hemodynamic states were studied in six sheep with surgically created mitral regurgitation. Regurgitant flow rates were obtained from electromagnetic flow meters. Left ventricular and atrial pressures were recorded using high-fidelity catheters. Regurgitant jet velocity was recorded by continuous wave Doppler. Left ventricular stroke work and energy losses due to the regurgitation were calculated. RESULTS: There was a close correlation between left ventricular stroke work and both jet energy and left atrial systolic pressure rise (r = 0.81, p = 0.0001 and r = 0.92, p = 0.0001, respectively). A moderate correlation to the regurgitant volume was found (r = 0.52, p = 0.01). CONCLUSIONS: The regurgitant volume itself is only one of the determinants of left ventricular stroke work in mitral regurgitation. Other factors such as left atrial mechanical properties and the regurgitant kinetic jet energy are at least as important for assessing cardiac work in patients with mitral regurgitation.

Computer simulation of circulation in patient with total cavo-pulmonary connection: inter-relationship of cardiac and vascular pressure, flow, resistance and capacitance.

The aim is to develop a computer model representative of the circulation in a patient with a uni-ventricular heart surgically palliated by a total cavo-pulmonary connection (TCPC). The effects of known hazardous exposures on this type of circulation are investigated. A model of the cardiovascular system is built using standard components such as transmission lines, restrictors and capacitances. The chamber of the heart consists of a volume connected to checkvalves, and an oscillating source flow connected to the volume represents the pumping of the heart. The following are simulated: exposure to cold, heat, high altitude, accelerating forces, blood loss, reduction in ventricular function, atrioventricular-valve regurgitation and treatment with afterload-reducing agents. During simulations, all the parameters can be changed, independently of each other, and the resulting changes in flow, resistance and pressure are recorded. Exposure to cold, reduced ventricular function and atriventricular-valve regurgitation result in a decrease in cardiac output (14, 58 and 45%, respectively). At high altitude, an increase of 18% is noted in the central venous pressure. Afterload-reducing agents increase the cardiac output by 8% and reduce central aortic pressure by 23%. Blood loss results in a marked reduction in perfusion pressure. It is concluded that the computer model is a useful instrument for simulation of a TCPC or Fontan circulation. The original criteria for this surgical procedure are those showing the most marked haemodynamic responses to different stimulus.

Quantification of mitral flow by Doppler color flow mapping.

This study was performed to develop and validate Doppler color flow methods for quantifying forward transmitral flow rates and volumes with isovelocity aliasing contours. We undertook computer modeling of flows and studied an animal model with strictly controlled mitral flows. Finite element analysis was first used to establish the isovelocity surface contours reconstructed from the magnitudes and directions of the velocity vectors proximal to the normal mitral orifice. We modeled finite element-simulated Doppler color flow isovelocity surfaces and computed non-angle-dependent simulated isovelocities to compare them. Then 24 pharmacologically induced hemodynamic states in six sheep in which mitral regurgitation had been previously created surgically were studied. Three methods were used for peak flow (PF) computation: (1) the classic hemispheric methods: PF = 2 pi r2.aliasing velocity; (2) a modified hemispheric method: PF = 2 pi r2.aliasing velocity Vo/Vo-aliasing velocity; and (3) a new segment of sphere method: PF = pi p2.aliasing velocity, where p is the chord from the zenith of the first aliasing contour to the circumference at its base. Mean volume flow was also calculated in combination with phasic flow information from continuous-wave Doppler echocardiography: mean volume flow = PF.VTI/Vmax.heart rate, where VTI and Vmax are the velocity-time integral and maximal velocity of mitral inflow by continuous-wave Doppler echocardiography. Compared with the flow rates obtained by electromagnetic flowmeters, different correlations and agreements were achieved for these methods. Correlation (r = 0.86) and agreement were best for the segment of sphere method for computation of forward mean volume flows in our model. Color flow Doppler quantitation with a segment of sphere or modified hemispheric method appears applicable for quantification of forward transmitral valve flow rates and volumes with reasonable accuracy.

Three-dimensional reconstruction of color Doppler flow convergence regions and regurgitant jets: an in vitro quantitative study.

OBJECTIVES: This study sought to investigate the applicability of a current implementation of a three-dimensional echocardiographic reconstruction method for color Doppler flow convergence and regurgitant jet imaging. BACKGROUND: Evaluation of regurgitant flow events, such as flow convergences or regurgitant jets, using two-dimensional imaging ultrasound color flow Doppler systems may not be robust enough to characterize these spatially complex events. METHODS: We studied two in vitro models using steady flow to optimize results. In the first constant-flow model, two different orifices were each mounted to produce flow convergences and free jets--a circular orifice and a rectangular orifice with orifice area of 0.24 cm(2). In another flow model, steady flows through a circular orifice were directed toward a curved surrounding wall to produce wall adherent jets. Video composite data of color Doppler flow images from both free jet and wall jet models were reconstructed and analyzed after computer-controlled 180 degrees rotational acquisition using a TomTec computer. RESULTS: For the free jet model there was an excellent relation between actual flow rates and three-dimensional regurgitant jet volumes for both circular and rectangular orifices (r = 0.99 and r = 0.98, respectively). However, the rectangular orifice produced larger jet volumes than the circular orifice, even at the same flow rates (p < 0.0001). Calculated flow rates by the hemispheric model using one axial measurement of the flow convergence isovelocity surface from two-dimensional color flow images underestimated actual flow rate by 35% for the circular orifice and by 44% for the rectangular orifice, whereas a hemielliptic method implemented using three axial measurements of the flow convergence zone derived using three-dimensional reconstruction correlated well with and underestimated actual flow rate to a lesser degree (22% for the circular orifice, 32% for the rectangular orifice). In the wall jet model, the jets were flattened against and spread along the wall and had reduced regurgitant jet volumes compared with free jets (p < 0.01). CONCLUSIONS: Three-dimensional reconstruction of flow imaged by color Doppler may add quantitative spatial information to aid computation methods that have been used for evaluating valvular regurgitation, especially where they related to complex geometric flow events.

Dynamics of left ventricular thrombi in patients with acute anterior myocardial infarction treated with thrombolytics.

BACKGROUND: Limited data exist concerning left ventricular thrombi during and after hospitalization in patients treated according to modern principles. The purpose of the present study was to examine the formation and resolution of left ventricular thrombi during the first month in patients with acute anterior myocardial infarction treated with streptokinase and aspirin. METHODS: Seventy-seven consecutive patients were studied prospectively during the hospital stay and 1-month follow-up study. Aspirin was used routinely, whereas anticoagulants were only used after a decision by the attending physician. Echocardiography was performed within 3 days of admission, before hospital discharge and after 1 month of follow-up. RESULTS: At the first examination, 17 of 77 patients (22%) had a thrombus. At discharge, 73 patients remained in the study. In five (31%) of the 16 patients with early thrombus, the thrombus persisted; in 18 (32%) of the 57 patients without early thrombus, a new thrombus was diagnosed. One month later, 65 patients remained eligible for follow-up study. In three of 20 patients (15%) the thrombus from the second examination persisted and in four of 45 patients (9%) a new thrombus was diagnosed. The disappearance rate between the second and third examination was high irrespective of whether patients were treated with anticoagulants (eight of nine, 89%) or not (nine of 11, 82%). Extensive left ventricular segmental dysfunction and signs of congestive heart failure were associated with the appearance of a left ventricular thrombus. No embolic events were recorded. CONCLUSION: In patients with anterior myocardial infarction treated with streptokinase and aspirin the development and disappearance of left ventricular thrombi is a highly dynamic process. A large proportion of thrombi resolve without additional anticoagulant therapy.

Dynamic change in mitral regurgitant orifice area: comparison of color Doppler echocardiographic and electromagnetic flowmeter-based methods in a chronic animal model.

OBJECTIVES: The aim of the present study was to investigate dynamic changes in the mitral regurgitant orifice using electromagnetic flow probes and flowmeters and the color Doppler flow convergence method. BACKGROUND: Methods for determining mitral regurgitant orifice areas have been described using flow convergence imaging with a hemispheric isovelocity surface assumption. However, the shape of flow convergence isovelocity surfaces depends on many factors that change during regurgitation. METHODS: In seven sheep with surgically created mitral regurgitation, 18 hemodynamic states were studied. The aliasing distances of flow convergence were measured at 10 sequential points using two ranges of aliasing velocities (0.20 to 0.32 and 0.56 to 0.72 m/s), and instantaneous flow rates were calculated using the hemispheric assumption. Instantaneous regurgitant areas were determined from the regurgitant flow rates obtained from both electromagnetic flowmeters and flow convergence divided by the corresponding continuous wave velocities. RESULTS: The regurgitant orifice sizes obtained using the electromagnetic flow method usually increased to maximal size in early to midsystole and then decreased in late systole. Patterns of dynamic changes in orifice area obtained by flow convergence were not the same as those delineated by the electromagnetic flow method. Time-averaged regurgitant orifice areas obtained by flow convergence using lower aliasing velocities overestimated the areas obtained by the electromagnetic flow method ([mean +/- SD] 0.27 +/- 0.14 vs. 0.12 +/- 0.06 cm2, p < 0.001), whereas flow convergence, using higher aliasing velocities, estimated the reference areas more reliably (0.15 +/- 0.06 cm2). CONCLUSIONS: The electromagnetic flow method studies uniformly demonstrated dynamic change in mitral regurgitant orifice area and suggested limitations of the flow convergence method.

Doppler evaluation of severity of mitral regurgitation: relation to pulmonary venous blood flow patterns in an animal study.

OBJECTIVES: This study examined the influence of regurgitant volume on pulmonary venous blood flow patterns in an animal model with quantifiable mitral regurgitation. BACKGROUND: Systolic pulmonary venous blood flow is influenced by atrial filling and compliance and ventricular output and by the presence of mitral regurgitation. The quantitative severity of the regurgitant volume itself is difficult to judge in clinical examinations. METHODS: Six sheep with chronic mitral regurgitation produced by previous operation to create chordal damage were examined. At reoperation the heart was exposed and epicardial echocardiography performed. Pulmonary venous blood flow waveforms were recorded by pulsed Doppler under color flow Doppler guidance using a Vingmed 750 scanner. The pulmonary venous systolic inflow to the left atrium was expressed as a fraction of the total inflow velocity time integral. Flows across the aortic and mitral valves were recorded by electromagnetic flowmeters balanced against each other. Pressures in the left ventricle and left atrium were measured directly with high fidelity manometer-tipped catheters. Preload and afterload were systematically manipulated, resulting in 24 stable hemodynamic states. RESULTS: Simple logarithmic correlation between the regurgitant volume and size of a positive or negative pulmonary venous inflow velocity time integral during systole was good (r = -0.841). By stepwise linear regression analysis with pulmonary venous negative systolic velocity time integral as a dependent variable compared with the regurgitant volume, fractional shortening, left atrial v wave size, systemic vascular resistance and left ventricular systolic pressure, only contributions from v wave size and regurgitant volume (r = 0.80) reached statistical significance in determining pulmonary venous negative systolic flow. CONCLUSIONS: Evaluation of systolic pulmonary venous blood flow velocity time integral can give valuable information helpful for estimating the regurgitant volume secondary to mitral regurgitation.

Hemodynamic changes during dipyridamole stress in patients with aortic stenosis.

Dipyridamole is a potent vasodilator used in pharmacologic stress testing. Patients with severe aortic stenosis are not suitable for exercise, and are usually not subjected to testing with vasodilator substances. The aim of the present study was to investigate hemodynamic changes during dipyridamole stress test in patients with aortic stenosis and to see if these changes where reversible by theophylline, an aminophylline derivative. Ten patients with aortic stenosis underwent right and left heart catheterization. Simultaneous recordings of cardiac output, left ventricular and aortic pressures were performed at baseline, after intravenous dipyridamole infusion (0.56 mg/kg dissolved in 250 ml of saline given over four minutes), and after intravenous theophylline injection (115 mg). There was an increase in heart rate, stroke volume and flow, and a decrease in systolic and diastolic blood pressure and in systemic vascular resistance after dipyridamole infusion. Left ventricular stroke work index and pressure time per minute increased after dipyridamole infusion suggesting an increase in myocardial oxygen demand, but there was no significant change compared to baseline after theophylline administration. Less than one third of left ventricular work was due to the resistance of the aortic valve. The aortic valve area changed with changes in flow. It is concluded that cardiac output, left ventricular work and myocardial oxygen demand after dipyridamole infusion increased in patients with aortic stenosis. The systemic vascular resistance seems to be more important determinant of cardiac output than the aortic valve obstruction. The calculated valve area appears to be flow-dependent.(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation of mitral regurgitation using a digitally determined color Doppler flow convergence 'centerline' acceleration method. Studies in an animal model with quantified mitral regurgitation.

BACKGROUND: The imaging and measurement of the proximal flow convergence region in the left ventricle have been reported to be useful for identifying the site of mitral regurgitation (MR) and for evaluating its severity. However, the application of this method has not gained general acceptance. There have been few in vivo studies with quantified reference standards for determining regurgitant volume, and those that have been reported used spectral Doppler standards and/or nonsimultaneously performed contrast ventriculography. The purpose of the present study was to evaluate the proximal flow convergence centerline velocity-distance profile method applied to chronic MR resulting from flail mitral leaflets in an animal model in which regurgitant flow rates and regurgitant volumes were determined simultaneously with electromagnetic flow probes and flowmeters. METHODS AND RESULTS: In six sheep, a total of 18 hemodynamically different states were obtained when the animals were restudied 6 months after surgical induction of MR produced by severing chordae tendineae to the anterior (three sheep) or posterior (three sheep) mitral leaflet. Echocardiographic studies with a Vingmed 750 were performed to obtain complete proximal axial flow acceleration velocity-distance profiles for each hemodynamic state. The color Doppler velocity data were directly transferred in digital format from the ultrasound instrumentation to a microcomputer. The severity of MR was assessed by the magnitude of the mitral regurgitant fraction determined using both mitral and aortic electromagnetic flow probes balanced against each other to yield regurgitant volume. MR was classified as grade I when the regurgitant fraction was < 20%, as grade II when it was 20% to 35%, and as grade III to IV when it was > 35%. Thus, of the 18 hemodynamic states, 4 (from two sheep) were grade I, 7 (from five sheep) were grade II, and 7 (from three sheep) were grade III to IV. All of the velocity-distance acceleration curves showed organized acceleration fields with highly significant correlations using multiplicative regression fits (y = a.x-b, r = .90 to .99, all P < .01). Grade III to IV MR resulted in rightward and upward shifts of the velocity-distance profile curves compared with those produced by grade II and grade I MR. All of the centerline velocity-distance profiles for grade III or IV regurgitation resided in a domain encompassed by velocities > 0.5 m/s at distances from the orifice > 0.6 cm; the profiles for grade I regurgitation resided in a domain encompassed by velocities < 0.3 m/s at distances from the orifice of < 0.45 cm. The profiles for grade II regurgitations resided in a domain between them. Regression analysis for the distance at which a velocity of 0.5 m/s was first reached bore a close relation to regurgitant fraction (r = .92, P < .0001) and peak regurgitant flow rate (r = .89, P < .0001). In addition, an equation for quantitatively correlating both a and b (coefficients from the multiplicative regression fits) with the peak regurgitant flow rate (Qpeak in L/min) was derived from stepwise regression analysis: Qpeak = 12a + 2.7b-2.4 (r = .96, P < .0001, SEE = .45 L/min). CONCLUSIONS: In this study, using quantified MR volume, we demonstrate that the proximal flow convergence axial centerline velocity-distance profile method can be used for evaluating the severity of MR without any assumption about isovelocity surface shape geometry.

Evaluation of ventricular septal defect by transesophageal echocardiography: intraoperative assessment.

The miniaturization of transesophageal echocardiography (TEE) probes, together with the development of the capability for biplane imaging from the esophagus, have increased the use of TEE in pediatric cardiology. The aim of this study was to evaluate the TEE findings in patients with ventricular septal defect (VSD) before and after closure primarily by means of pediatric biplane probes. This study group included 69 patients who underwent VSD closure as an isolated repair or as a part of a definitive repair of a more complicated lesion. Ages ranged from 6 days to 15.6 years (median 1 year, 4 months), with operative weights ranging from 2.9 kg to 68 kg (median 10 kg). Preoperative and follow-up transthoracic echocardiograms (TTE) were also performed. Intraoperative TEE was performed without complication in all 69 patients. Preoperative results: (1) anatomic findings: Two muscular VSDs were detected by matrix TEE but could not be observed by TTE. A patient with preoperative TTE diagnosis of an ostium primum ASD was found to have atrioventricular (AV) canal by TEE. In three of six AV canal type VSDs, both TTE and TEE demonstrated left ventricular-right atrial shunting (2) aortic regurgitation associated with VSD: Aortic regurgitation as a result of right coronary cusp prolapse was detected in one of five supracristal VSDs in which the biplane or matrix TEE was used.(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation of anatomical obstruction by Doppler echocardiography and magnetic resonance imaging in patients with coarctation of the aorta.

OBJECTIVE: To evaluate a new Doppler echocardiographic index of obstruction in patients with native coarctation or recoarctation. PATIENTS: 32 patients (mean age 20, range 3 months--50 years). METHODS: Magnetic resonance imaging (MRI) was used to investigate the descending aorta. The cross sectional area of the obstruction was compared with the area of the abdominal aorta as an index of obstruction (CoA index). Doppler echocardiography was used to record the velocities in the coarctation jet and in the abdominal aorta. According to the continuity equation the ratio of these velocities should equal the ratios of the cross sectional areas. The gradients and diastolic half time of the Doppler curve were calculated. RESULTS: There was a close correlation between the MRI index of obstruction and the Doppler velocity ratio (r = 0.92). The sensitivity and specificity of this ratio in detecting a CoA index equal to or less than 0.25 were better than those obtained with gradients only or the combination of gradients and diastolic half time. CONCLUSION: The new Doppler velocity ratio correlated closely with an anatomical index of obstruction. It was easy to record in most patients and it avoided difficulties about the choice of instantaneous or peak to peak gradients and whether or not to subtract proximal velocities for the calculation of gradients.