Use of 3-Dimensional Color Doppler Echocardiography to Measure Stroke Volume in Human Beings: Comparison with Thermodilution

Color Flow Ultrasound Spatial Sampling Beam Density for Partial Volume-Corrected Three-Dimensional Volume Flow (3DVF): Theory, Simulation, and Experiment

OBJECTIVE

The purpose of this study was to quantify the accuracy of partial volume-corrected three-dimensional volume flow (3DVF) measurements as a function of spatial sampling beam density using carefully-designed parametric analyses in order to inform the target applications of 3DVF.

METHODS

Experimental investigations employed a mechanically-swept curvilinear ultrasound array to acquire 3D color flow (6.3 MHz) images in flow phantoms consisting of four lumen diameters (6.35, 4.88, 3.18 and 1.65 mm) with volume flow rates of 440, 260, 110 and 30 mL/min, respectively. Partial volume-corrected three-dimensional volume flow (3DVF) measurements, based on the Gaussian surface integration principle, were computed at five regions of interest positioned between depths of 2 and 6 cm in 1 cm increments. At each depth, the color flow beam point spread function (PSF) was also determined, using in-phase/quadrature data, such that 3DVF bias could then be related to spatial sampling beam density. Corresponding simulations were performed for a laminar parabolic flow profile that was sampled using the experimentally-measured PSFs. Volume flow was computed for all combinations of lumen diameters and the PSFs at each depth.

RESULTS

Accurate 3DVF measurements, i.e., bias less than ±20%, were achieved for spatial sampling beam densities where at least 6 elevational color flow beams could be positioned across the lumen. In these cases, greater than 8 lateral color flow beams were present. PSF measurements showed an average lateral-to-elevational beam width asymmetry of 1:2. Volume flow measurement bias increased as the color flow beam spatial sampling density within the lumen decreased.

CONCLUSION

Applications of 3DVF, particularly those in the clinical domain, should focus on areas where a spatial sampling density of 6 × 6 (lateral x elevational) beams can be realized in order to minimize measurement bias. Matrix-based ultrasound arrays that possess symmetric PSFs may be advantageous to achieve adequate beam densities in smaller vessels.

CARDIAC OUTPUT IN CRITICALLY ILL PATIENTS CAN BE ESTIMATED EASILY AND ACCURATELY USING THE MINUTE DISTANCE OBTAINED BY PULSED-WAVE DOPPLER

ABSTRACT

Background: Cardiac output (CO) assessment is essential for management of patients with circulatory failure. Among the different techniques used for their assessment, pulsed-wave Doppler cardiac output (PWD-CO) has proven to be an accurate and useful tool. Despite this, assessment of PWD-CO could have some technical difficulties, especially in the measurement of left ventricular outflow tract diameter (LVOTd). The use of a parameter such as minute distance (MD) which avoids LVOTd in the PWD-CO formula could be a simple and useful way to assess the CO in critically ill patients. Therefore, the aim of this study was to evaluate the correlation and agreement between PWD-CO and MD. Methods: A prospective and observational study was conducted over 2 years in a 30-bed intensive care unit (ICU). Adult patients who required CO monitoring were included. Clinical echocardiographic data were collected within the first 24 h and at least once more during the first week of ICU stay. PWD-CO was calculated using the average value of three LVOTd and left ventricular outflow tract velocity-time integral (LVOT-VTI) measurements, and heart rate. Minute distance was obtained from the product of LVOT-VTI × heart rate. Pulsed-wave Doppler cardiac output was correlated with MD using linear regression. Cardiac output was quantified from the MD using the equation defined by linear regression. Bland-Altman analysis was also used to evaluate the level of agreement between CO calculated from MD (MD-CO) and PWD-CO. The percentage error was calculated. Results: A total of 98 patients and 167 CO measurements were analyzed. Sixty-seven (68%) were male, the median age was 66 years (interquartile range [IQR], 53-75 years), and the median Acute Physiology and Chronic Health Evaluation II score was 22 (IQR, 16-26). The most common cause of admission was shock in 81 patients (82.7%). Sixty-nine patients (70.4%) were mechanically ventilated, and 68 (70%) required vasoactive drugs. The median CO was 5.5 L/min (IQR, 4.8-6.6 L/min), and the median MD was 1,850 cm/min (IQR, 1,520-2,160 cm/min). There was a significant correlation between PWD-CO and MD-CO in the general population ( R2 = 0.7; P < 0.05). This correlation improved when left ventricular ejection fraction (LVEF) was less than 60% ( R2 = 0.85, P < 0.05). Bland-Altman analysis showed good agreement between PWD-CO and MD-CO in the general population, the median bias was 0.02 L/min, the limits of agreement were -1.92 to +1.92 L/min. The agreement was better in patients with LVEF less than 60% with a median bias of 0.005 L/min and limits of agreement of -1.56 to 1.55 L/min. The percentage error was 17% in both cases. Conclusion: Measurement of MD in critically ill patients provides a simple and accurate estimate of CO, especially in patients with reduced or preserved LVEF. This would allow earlier cardiovascular assessment in patients with circulatory failure, which is of particular interest in difficult clinical or technical conditions.

From left ventricular ejection fraction to cardiac hemodynamics: role of echocardiography in evaluating patients with heart failure

In clinical practice heart failure (HF) patients are generally classified on the basis of left ventricular (LV) ejection fraction. This approach, however, has important limitations. According to the definition of HF as a clinical syndrome that results from any impairment of LV filling or ejection of blood, a more articulated hemodynamic categorization of HF patients taking into account both LV forward flow and filling pressure would be desirable. However, the reliability of hemodynamic measures using echocardiographic techniques, which are the most used in current clinical practice for evaluation of HF patients, needs to be clarified. The aim of this article, therefore, is to verify whether echocardiography has acceptable feasibility, accuracy and reproducibility for the noninvasive evaluation of LV hemodynamics. This evaluation is necessary to progress to a hemodynamic characterization of HF patients that would ultimately overcome the HF classification based on ejection fraction.

Automatic quantification of aortic regurgitation using 3D full volume color doppler echocardiography: a validation study with cardiac magnetic resonance imaging

Recent advances in real-time three-dimensional (3D) echocardiography provide the automated measurement of mitral inflow and aortic stroke volume without the need to assume the geometry of the heart. The aim of this study is to explore the ability of 3D full volume color Doppler echocardiography (FVCDE) to quantify aortic regurgitation (AR). Thirty-two patients with more than a moderate degree of AR were enrolled. AR volume was measured by (1) two-dimensional-CDE, using the proximal isovelocity surface area (PISA) and (2) real-time 3D-FVCDE with (3) phase-contrast cardiac magnetic resonance imaging (PC-CMR) as the reference method. Automated AR quantification using 3D-FVCDE was feasible in 30 of the 32 patients. 2D-PISA underestimated the AR volume compared to 3D-FVCDE and PC-CMR (38.6 ± 9.9 mL by 2D-PISA; 49.5 ± 10.2 mL by 3D-FVCDE; 52.3 ± 12.6 mL by PC-CMR). The AR volume assessed by 3D-FVCDE showed better correlation and agreement with PC-CMR (r = 0.93, p < 0.001, 2SD: 9.5 mL) than did 2D-PISA (r = 0.76, p < 0.001, 2SD: 15.7 mL). When used to classify AR severity, 3D-FVCDE agreed better with PC-CMR (k = 0.94) than did 2D-PISA (k = 0.53). In patients with eccentric jets, only 30% were correctly graded by 2D-PISA. Conversely, almost all patients with eccentric jets (86.7%) were correctly graded by 3D-FVCDE. In patients with multiple jets, only 3 out of 10 were correctly graded by 2D-PISA, while 3D-FVCDE correctly graded 9 out of 10 of these patients. Automated quantification of AR using the 3D-FVCDE method is clinically feasible and more accurate than the current 2D-based method. AR quantification by 2D-PISA significantly misclassified AR grade in patients with eccentric or multiple jets. This study demonstrates that 3D-FVCDE is a valuable tool to accurately measure AR volume regardless of AR characteristics.

Accuracy of Echocardiographic Cardiac Index Assessment in Subjects with Preserved Left Ventricular Ejection Fraction

INTRODUCTION

We aimed to determine the accuracy of the echocardiographic assessment of cardiac index (CI) in subjects with preserved left ventricular ejection fraction (LVEF).

METHODS

Thirty-three subjects with LVEF >50%, normal sinus rhythm, and a broad spectrum of hemodynamic profiles underwent echocardiography immediately followed by right heart catheterization. As gold standards, CI was assessed using thermodilution [CI (TD)] and the Fick method [CI (F)]. Echocardiographic CI was assessed by four methods: from the left ventricular outflow tract (LVOT) velocity time integral and the LVOT diameter as measured [CI (LVOTm)] as well as estimated from body surface area [CI (LVOTe)], and from stroke volume indices assessed using the biplane [CI (BP)] and monoplane [CI (MP)] methods.

RESULTS

The mean CI (TD), CI (F), CI (LVOTm), CI (LVOTe), CI (BP), and CI (MP) were 3.0 ± 0.9, 3.1 ± 0.7, 2.8 ± 0.6, 3.3 ± 0.6, 2.0 ± 0.6, and 2.2 ± 0.7 L/min/m(2) . There were modest correlations between CI (TD) and CI (F) and all four noninvasive measures of CI with r(2) values ranging from 0.09 to 0.30. CI (LVOTm) underestimated CI (TD) and CI (F) by 0.3 and 0.3 L/min/m(2) , CI (LVOTe) overestimated CI (TD) and CI (F) by 0.3 and 0.2 L/min/m(2) , and CI (BP) and CI (MP) underestimated CI (TD) and CI (F) by 1.1 and 1.1 L/min/m(2) and 0.9 and 0.9 L/min/m(2) , respectively, with large limits of agreement for all comparisons.

CONCLUSIONS

In subjects with nondilated left ventricles with preserved LVEF, flow- or volume-based measures of CI by 2D echocardiography may not accurately reflect CI (TD) and CI (F). Further larger studies are required to verify our findings and to evaluate the accuracy of contrast and 3D echocardiography in this setting.

Quantitative assessment of mitral inflow and aortic outflow stroke volumes by 3-dimensional real-time full-volume color flow doppler transthoracic echocardiography: an in vivo study

OBJECTIVES

Noninvasive quantification of left ventricular (LV) stroke volumes has an important clinical role in assessing circulation and monitoring therapeutic interventions for cardiac disease. This study validated the accuracy of a real-time 3-dimensional (3D) color flow Doppler method performed during transthoracic echocardiography (TTE) for quantifying volume flows through the mitral and aortic valves using a dedicated offline 3D flow computation program compared to LV sonomicrometry in an open-chest animal model.

METHODS

Forty-six different hemodynamic states in 5 open-chest pigs were studied. Three-dimensional color flow Doppler TTE and 2-dimensional (2D) TTE were performed by epicardial scanning. The dedicated software was used to compute flow volumes at the mitral annulus and the left ventricular outflow tract (LVOT) with the 3D color flow Doppler method. Stroke volumes by 2D TTE were computed in the conventional manner. Stroke volumes derived from sonomicrometry were used as reference values.

RESULTS

Mitral inflow and LVOT outflow derived from the 3D color flow Doppler method correlated well with stroke volumes by sonomicrometry (R = 0.96 and 0.96, respectively), whereas correlation coefficients for mitral inflow and LVOT outflow computed by 2D TTE and stroke volumes by sonomicrometry were R = 0.84 and 0.86. Compared to 2D TTE, the 3D method showed a smaller bias and narrower limits of agreement in both mitral inflow (mean ± SD: 3D, 2.36 ± 2.86 mL; 2D, 10.22 ± 8.46 mL) and LVOT outflow (3D, 1.99 ± 2.95 mL; 2D, 4.12 ± 6.32 mL).

CONCLUSIONS

Real-time 3D color flow Doppler quantification is feasible and accurate for measurement of mitral inflow and LVOT outflow stroke volumes over a range of hemodynamic conditions.

Clinical application of three-dimensional echocardiography

Echocardiography is one of the most valuable diagnostic tools in cardiology. Technological advances in ultrasound, computer and electronics enables three-dimensional (3-D) imaging to be a clinically viable modality which has significant impact on diagnosis, management and interventional procedures. Since the inception of 3D fully-sampled matrix transthoracic and transesophageal technology it has enabled easier acquisition, immediate on-line display, and availability of on-line analysis for the left ventricle, right ventricle and mitral valve. The use of 3D TTE has mainly focused on mitral valve disease, left and right ventricular volume and functional analysis. As structural heart disease procedures become more prevalent, 3D TEE has become a requirement for preparation of the procedure, intra-procedural guidance as well as monitoring for complications and device function. We anticipate that there will be further software development, improvement in image quality and workflow.

Evaluation of a new 3-dimensional color Doppler flow method to quantify flow across the mitral valve and in the left ventricular outflow tract: an in vitro study

OBJECTIVES

The aim of this study was to assess the accuracy, feasibility, and reproducibility of determining stroke volume from a novel 3-dimensional (3D) color Doppler flow quantification method for mitral valve (MV) inflow and left ventricular outflow tract (LVOT) outflow at different stroke volumes when compared with the actual flow rate in a pumped porcine cardiac model.

METHODS

Thirteen freshly harvested pig hearts were studied in a water tank. We inserted a latex balloon into each left ventricle from the MV annulus to the LVOT, which were passively pumped at different stroke volumes (30-80 mL) using a calibrated piston pump at increments of 10 mL. Four-dimensional flow volumes were obtained without electrocardiographic gating. The digital imaging data were analyzed offline using prototype software. Two hemispheric flow-sampling planes for color Doppler velocity measurements were placed at the MV annulus and LVOT. The software computed the flow volumes at the MV annulus and LVOT within the user-defined volume and cardiac cycle.

RESULTS

This novel 3D Doppler flow quantification method detected incremental increases in MV inflow and LVOT outflow in close agreement with pumped stroke volumes (MV inflow, r = 0.96; LVOT outflow, r = 0.96; P < .01). Bland-Altman analysis demonstrated overestimation of both (MV inflow, 5.42 mL; LVOT outflow, 4.46 mL) with 95% of points within 95% limits of agreement. Interobserver variability values showed good agreement for all stroke volumes at both the MV annulus and LVOT.

CONCLUSIONS

This study has shown that the 3D color Doppler flow quantification method we used is able to compute stroke volumes accurately at the MV annulus and LVOT in the same cardiac cycle without electrocardiographic gating. This method may be valuable for assessment of cardiac output in clinical studies.

Three-Dimensional Echocardiography: Advancements in Qualitative and Quantitative Analyses of Mitral Valve Morphology in Mitral Valve Prolapse

Degenerative mitral valve disease (MVD) is the leading cause of organic mitral regurgitation (MR), one of the most common valvular heart disease in western countries. Substantial progresses in the surgical treatment of degenerative MVD have improved life expectancy of patients with significant MR. However, prognosis, surgical decision and timing of surgery strongly depend on the accurate characterization of mitral valve (MV) anatomy and pathology and on the precise quantification of MR. Three-dimensional (3D) echocardiography, a major technological breakthrough in the field of cardiovascular imaging, provides several advantages over two-dimensional (2D) imaging in the qualitative and quantitative evaluations of MV apparatus. In this review, we focus on the contribution of this new modality to the diagnosis of degenerative MVD, the quantitative assessment of MR severity, the selection and monitoring of surgical and percutaneous procedures, the evaluation of procedural outcomes. The results of a systematic and exhaustive search of the existing literature, restricted to real-time 3D echocardiography in adults, are here reported.

Automated quantification of mitral regurgitation by three dimensional real time full volume color Doppler transthoracic echocardiography: a validation with cardiac magnetic resonance imaging and comparison with two dimensional quantitative methods

BACKGROUND

Accurate assessment of mitral regurgitation (MR) severity is crucial for clinical decision-making and optimizing patient outcomes. Recent advances in real-time three dimensional (3D) echocardiography provide the option of real-time full volume color Doppler echocardiography (FVCD) measurements. This makes it practical to quantify MR by subtracting aortic stroke volume from the volume of mitral inflow in an automated manner.

METHODS

Thirty-two patients with more than a moderate degree of MR assessed by transthoracic echocardiography (TTE) were consecutively enrolled during this study. MR volume was measured by 1) two dimensional (2D) Doppler TTE, using the proximal isovelocity surface area (PISA) and the volumetric quantification methods (VM). Then, 2) real time 3D-FVCD was subsequently obtained, and dedicated software was used to quantify the MR volume. MR volume was also measured using 3) phase contrast cardiac magnetic resonance imaging (PC-CMR). In each patient, all these measurements were obtained within the same day. Automated MR quantification was feasible in 30 of 32 patients.

RESULTS

The mean regurgitant volume quantified by 2D-PISA, 2D-VM, 3D-FVCD, and PC-CMR was 72.1 ± 27.7, 79.9 ± 36.9, 69.9 ± 31.5, and 64.2 ± 30.7 mL, respectively (p = 0.304). There was an excellent correlation between the MR volume measured by PC-CMR and 3D-FVCD (r = 0.85, 95% CI 0.70-0.93, p < 0.001). Compared with PC-CMR, Bland-Altman analysis for 3D-FVCD showed a good agreement (2 standard deviations: 34.3 mL) than did 2D-PISA or 2D-VM (60.0 and 62.8 mL, respectively).

CONCLUSION

Automated quantification of MR with 3D-FVCD is feasible and accurate. It is a promising tool for the real-time 3D echocardiographic assessment of patients with MR.

Quantification of Chronic Functional Mitral Regurgitation by Automated 3-Dimensional Peak and Integrated Proximal Isovelocity Surface Area and Stroke Volume Techniques Using Real-Time 3-Dimensional Volume Color Doppler Echocardiography

Background—

The aim of this study was to test the accuracy of an automated 3-dimensional (3D) proximal isovelocity surface area (PISA) (in vitro and patients) and stroke volume technique (patients) to assess mitral regurgitation (MR) severity using real-time volume color flow Doppler transthoracic echocardiography.

Methods and Results—

Using an in vitro model of MR, the effective regurgitant orifice area and regurgitant volume (RVol) were measured by the PISA technique using 2-dimensional (2D) and 3D (automated true 3D PISA) transthoracic echocardiography. The mean anatomic regurgitant orifice area (0.35±0.10 cm 2 ) was underestimated to a greater degree by the 2D (0.12±0.05 cm 2 ) than the 3D method (0.25±0.10 cm 2 ; P <0.001 for both). Compared with the flowmeter (40±14 mL), the RVol by 2D PISA (20±19 mL) was underestimated ( P <0.001), but the 3D peak (43±16 mL) and integrated PISA-based (38±14 mL) RVol were comparable ( P >0.05 for both). In patients (n=30, functional MR), 3D effective regurgitant orifice area correlated well with cardiac magnetic resonance imaging RVol r =0.84 and regurgitant fraction r =0.80. Compared with cardiac magnetic resonance imaging RVol (33±22 mL), the integrated PISA RVol (34±26 mL; P =0.42) was not significantly different; however, the peak PISA RVol was higher (48±27 mL; P <0.001). In addition, RVol calculated as the difference in automated mitral and aortic stroke volumes by real-time 3D volume color flow Doppler echocardiography was not significantly different from cardiac magnetic resonance imaging (34±21 versus 33±22 mL; P =0.33).

Conclusions—

Automated real-time 3D volume color flow Doppler based 3D PISA is more accurate than the 2D PISA method to quantify MR. In patients with functional MR, the 3D RVol by integrated PISA is more accurate than a peak PISA technique. Automated 3D stroke volume measurement can also be used as an adjunctive method to quantify MR severity.

Agreement between cardiac outputs by four-dimensional echocardiography and thermodilution method is poor

OBJECTIVE

The objective of the study was to determine the agreement of cardiac output (CO) measured by four-dimensional echocardiography (4D echo) to simultaneously obtain CO from pulmonary artery catheter (PAC) using thermodilution technique.

MATERIALS AND METHODS

Sixty-three comparable readings from 27 patients scheduled for elective coronary artery bypass were included. All echocardiographic measurements were obtained by one experienced echocardiographer. All echo images were analyzed independently and blinded from PAC-obtained measurements. Analysis was primarily done by Bland and Altman plot. The collected data were further controlled for interobserver bias and image quality.

RESULTS

Differences in CO measurements increased with higher CO, hence values were logarithmically transformed. On the logaritmic scale, the 4D echo underestimated CO by 0.37 l/min compared with PAC, indicating that PAC measurements were 1.45 times higher than the 4D echo (95% confidence interval 1.32-1.52) and limits of agreement 0.97-2.14). The interobserver bias of 4D echo measurement analysis was 0.29 l/min (95% confidence interval 0.16-0.42) and limits of agreement -0.8-1.38). No difference was seen in image quality between comparisons with good agreement compared with comparisons with poor agreement.

CONCLUSION

The agreement between COs by 4D echo and standard PAC thermodilution technique was poor. 4D echo underestimates CO as compared with PAC. This is most likely caused by the analysis software or low frame rate inherent to the technique.

A novel operator-independent algorithm for cardiac output measurements based on three-dimensional transoesophageal colour Doppler echocardiography

AIMS

Cardiac output (CO) measurements from three-dimensional (3D) trans-mitral Doppler echocardiography are prone to error as manual selection of the region of interest (i.e. the site of measurement) is required. We newly developed an automated, user-independent algorithm to select the site of colour Doppler CO measurement. We aimed to validate this new method by benchmarking it against thermodilution, the current gold standard for CO measurements.

METHODS AND RESULTS

Transoesophageal colour 3D Doppler echocardiographic studies were obtained from 15 patients who also had received a pulmonary catheter for invasive CO measurements. Trans-mitral flow was determined using a novel operator-independent algorithm to automatically select the optimal site of measurement. The operator-independent CO measurements were referenced against thermodilution. A good correlation was found between operator-independent Doppler flow computations and thermodilution with a mean bias of 0.09 L/min, standard deviation of bias 1.3 L/min, and a 26% error (2 SD/mean CO). Mean CO was 4.94 L/min (range 3.10-7.10 L/min).

CONCLUSION

Our findings demonstrate that CO computation from transoesophageal colour 3D Doppler echo can be automated concerning the site of velocity measurement. Our operator-independent algorithm provides an objective and reproducible alternative to thermodilution.

Haemodynamics and blood flow measured using ultrasound imaging

Visualization of, and measurements related to, haemodynamic phenomena in arteries may be made using ultrasound systems. Most ultrasound technology relies on simple measurements of blood velocity taken from a single site, such as the peak systolic velocity for assessment of the degree of lumen reduction caused by an arterial stenosis. Real-time two-dimensional (2D) flow field visualization is possible using several methods, such as colour flow, blood flow imaging, and echo particle image velocimetry; these have applications in the examination of the flow field in diseased arteries and in heart chambers. Three-dimensional (3D) and four-dimensional ultrasound systems have been described. These have been used to provide 2D velocity profile data for the estimation of volumetric flow. However, they are limited for haemodynamic evaluation in that they provide only one component of the velocity. The provision of all seven components (three space, three velocity, and one time) is possible using image-guided modelling, in which 3D ultrasound is combined with computational fluid dynamics. This method also allows estimation of turbulence data and of relevant quantities such as the wall shear stress.

Assessing aortic valve area in aortic stenosis by continuity equation: a novel approach using real-time three-dimensional echocardiography

AIMS

Two-dimensional echocardiographic (2DE) continuity-equation derived aortic valve area (AVA) in aortic stenosis (AS) relies on non-simultaneous measurement of left ventricular outflow tract (LVOT) velocity and geometric assumptions of LVOT area, which can amplify error, especially in upper septal hypertrophy (USH). We hypothesized that real-time three-dimensional echocardiography (RT3DE) can improve accuracy of AVA by directly measuring LVOT stroke volume (SV) in one window.

METHODS AND RESULTS

RT3DE colour Doppler and 2DE were acquired in 68 AS patients (74 +/- 12 yrs) prospectively. SV was derived from flow obtained from a sampling curve placed orthogonal to LVOT (Tomtec Imaging). Agreement between continuity-equation derived AVA by RT3DE (AVA(3D-SV)) and 2DE (AVA(2D)) and predictors of discrepancies were analysed. Validation of LVOT SV was performed by aortic flow probe in a sheep model with balloon inflation of septum to mimic USH. There was only modest correlation between AVA(2D) and AVA(3D-SV) (r = 0.71, difference 0.11 +/- 0.23 cm(2)). The degree of USH was significantly associated with difference in AVA calculation (r = 0.4, P = 0.005). In experimentally distorted LVOT geometry in sheep, RT3DE correlated better with flow probe assessment (r = 0.96, P < 0.001) than 2DE (r = 0.71, P = 0.006).

CONCLUSION

RT3DE colour Doppler-derived LVOT SV in the calculation of AVA by continuity equation is more accurate than 2D, including in situations such as USH, common in the elderly, which modify LVOT geometry.

Current Status of Three-Dimensional Color Flow Doppler

Three-dimensional (3D) color Doppler echocardiography is a relatively new noninvasive tool that displays and quantitates regurgitant flow and also enables estimation of cardiac output, stroke volume, pulmonary outflow, and shunt calculations. This article provides an overview of the current methodology of 3D color flow, and its advantages and limitations.