A simplified, practical echocardiographic approach for 3-dimensional surfacing and quantitation of the left ventricle: clinical application in patients with abnormally shaped hearts

Integration of three-dimensional echocardiography into the modern-day echo laboratory

Three-dimensional echocardiography (3DE) has emerged in recent decades from a conceptual, research tool to an important, useful imaging technique that can informatively impact daily clinical practice. However, its adoption into the modern-day echo laboratory requires the acknowledgment of its value, coupled with proper leadership, education, and resources to implement and integrate its use with conventional echo techniques. 3DE integration involves important updates regarding equipment and patient selection, assimilation of 3D protocols into current clinical routine, laboratory workflow adaptation, storage, and reporting. This review will provide a practical blueprint and key points of how to integrate 3DE into today's echo laboratory, necessary resources to implement 3D workflow, logistical challenges that remain, and future directions to further improve assimilation of this relevant echo technique into the laboratory.

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.

How accurately, reproducibly, and efficiently can we measure left ventricular indices using M-mode, 2-dimensional, and 3-dimensional echocardiography in children?

BACKGROUND

Measurements of left ventricular (LV) size, mass, and function are the most common and important tasks for echocardiography in clinical practice and research in children with congenital and acquired heart diseases. There are little data to compare the utility of M-mode (MM), 2-dimensional (2D), and 3-dimensional (3D) echocardiographic techniques for quantification of LV indices. The objective of the study was to assess the accuracy, reproducibility, and efficiency of these echocardiographic methods for measurement of LV indices in children.

METHODS

A prospective study was conducted in 20 consecutive children (mean 10.6 +/- 2.8 years, 11 male and 9 female subjects) using conventional MM, 2D, and real-time 3D echocardiography (RT3DE). A Sonos 7500 system (Philips Medical Systems, Andover, MA) was used. M-mode and 2DE measurements were made according to the American Society of echocardiography recommendations. To include the entire LV for volumetric measurement, full-volume 3D data sets were acquired from 4 electrocardiogram gated subvolumes. The 3DE measurements were made off-line manually using 4-plane and 8-plane algorithms by 4D Echo-View (TomTec Imaging Systems, Munich, Germany) and a semiautomated algorithm by QLAB (Philips Medical Systems). Magnetic resonance imaging studies were also performed to determine the LV indices by a disk summation method based on the Simpson principle.

RESULTS

The correlation and agreement between MM, 2D, and RT3D echocardiography and magnetic resonance imaging measurements are good (r = 0.81-0.97) for the 3 methods. The correlation was superior for RT3DE compared with 2DE and MM. The correlation and agreement were similar for the three 3DE methods. The intra- and interobserver variabilities ranged from MM (4.3%-4.8% and 7.0%-8.7%), 2DE (3.3%-4.5% and 5.5%-7.3%), and 3DE (0.4%-2.3%, and 0.2%-4.8%). The total time (acquisition and analysis) used for MM measurements was the least compared with 2DE and 3DE. The total time for 3DE using the semiautomated algorithms was not significantly different compared with that for 2DE.

CONCLUSIONS

Our study showed that MM provides the most efficient assessment of LV indices but is the least accurate and reproducible technique compared with 2DE and 3DE. Three-dimensional echocardiography using both automated and manual analysis algorithm is superior to MM and 2DE for measurements of LV indices, and the automated 3DE algorithm is as efficient as 2DE. Therefore, 3DE using the automated algorithm is the method of choice for quantification of LV indices.

Real-Time Three-Dimensional Echocardiographic Acquisition and Quantification of Left Ventricular Indices in Children and Young Adults with Congenital Heart Disease: Comparison with Magnetic Resonance Imaging

BACKGROUND

Echocardiographic assessment of left ventricular (LV) contractility and dimensions is important in the management of patients with congenital heart disease. Conventional two-dimensional measures are limited because of volume or pressure-overloaded right ventricles that may distort the septal planes. Real-time three-dimensional echocardiography (RT3DE) has overcome these limitations; however, postprocessing image reconstruction and analysis are required. We compared LV indices calculated by new online RT3DE software with those obtained by magnetic resonance imaging (MRI) in patients with congenital heart disease.

METHODS

Twelve patients (ages 1-33 years, median age = 15.9 years) with congenital heart disease underwent RT3DE and cardiac MRI. End-diastolic and end-systolic LV volumes, stroke volume, ejection fraction, and mass were calculated online using biplane method-of-discs and semiautomated border detection echocardiographic techniques.

RESULTS

All RT3DE volumes correlated strongly with MRI (r = 0.93-0.99, P < .001). Ejection fraction had a lower correlation (r = 0.69, P = .013). There was no significant underestimation or overestimation of MRI values by RT3DE. Both biplane method-of-discs and semiautomated border detection echocardiographic techniques had excellent volume correlation (r = 0.94-0.99, P < .001). Interobserver variability was 7%.

CONCLUSIONS

Combined RT3DE acquisition and analysis machines can accurately assess the LV in patients with congenital heart disease, thus impacting clinical management and perhaps obviating the need for MRI in some cases.

Rapid full volume data acquisition by real-time 3-dimensional echocardiography for assessment of left ventricular indexes in children: A validation study compared with magnetic resonance imaging

OBJECTIVE

We sought to assess the feasibility, accuracy, and reproducibility of a rapid full volume acquisition strategy using real-time (RT) 3-dimensional (3D) echocardiography (3DE) for measurement of left ventricular (LV) volumes, mass, stroke volume (SV), and ejection fraction (EF) in children.

METHODS

A total of 19 healthy children (mean 10.6 +/- 2.8 years, 11 male and 9 female) were prospectively enrolled in this study. RT 3DE was performed using an ultrasound system to acquire full volume 3D dataset from the apical window with electrocardiographic triggering in 8 s/dataset. The images were processed offline using software. The LV endocardial and epicardial borders were traced manually to derive LV end-systolic volume, end-diastolic volume, mass, SV, and EF. Magnetic resonance imaging (MRI) studies were performed on a 1.5-T scanner using a breath hold 2-dimensional cine-FIESTA (fast imaging employing steady-state acquisition) sequence.

RESULTS

All RT 3DE and MRI data were acquired successfully for analysis. Measurements of LV end-systolic volume, end-diastolic volume, mass, SV, and EF by RT 3DE correlated well by Pearson regression ( r = 0.86-0.97, P < .001) and agreed well by Bland-Altman analysis with MRI. The interobserver and intraobserver variability of RT 3DE measurements were less than 5%.

CONCLUSIONS

This prospective study demonstrated that RT 3DE measurements of LV end-systolic volume, end-diastolic volume, mass, SV, and EF in children using rapid full volume acquisition strategy are feasible, accurate, and reproducible and are comparable with MRI measurements.

Quantitative analysis of gated SPECT images using an efficient physical deformation model

In this paper, we present quantitative analysis of cardiac images using an efficient physical deformation model to evaluate ventricular function. By using this model we can accurately and efficiently compute ventricular volume, myocardial mass, endo- and epi-cardial wall motions and wall thickness over a full cardiac cycle. Patients with cardiac diseases were studied in our modeling and measurement framework using gated single-photon emission computed tomographic images. The results show that quantitative analysis using the model is very useful for the assessment of the extent and severity of myocardial ischemia or infarction. And it could be helpful to improve the decision-making process in the treatment of patients with cardiac diseases.

Quantification of left ventricular volumes and ejection fraction using freehand transthoracic three-dimensional echocardiography: comparison with magnetic resonance imaging

OBJECTIVES

Our aim was to validate 3-dimensional echocardiography (3DE) for assessment of left ventricular (LV) end-diastolic volume, end-systolic volume (ESV), stroke volume, and ejection fraction (EF) using the freehand-acquisition method. Furthermore, LV volumes by breath hold-versus free breathing-3DE acquisition were assessed and compared with magnetic resonance imaging (MRI).

METHODS

From the apical position, a fan-like 3DE image was acquired during free breathing and another, thereafter, during breath hold. In 27 patients, 28 breath hold- and 24 free breathing-3DE images were acquired. A total of 17 patients underwent both MRI and 3DE. MRI contours were traced along the outer endocardial contour, including trabeculae, and along the inner endocardial contour, excluding trabeculae, from the LV volume.

RESULTS

All 28 (100%) breath hold- and 86% of free breathing-3DE acquisitions could be analyzed. Intraobserver variation (percentual bias +/- 2 SD) of end-diastolic volume, ESV, stroke volume, and EF for breath-hold 3DE was, respectively, 0.3 +/- 10.2%, 0.3 +/- 14.6%, 0.1 +/- 18.4%, and -0.1 +/- 5.8%. For free-breathing 3DE, findings were similar. A significantly better interobserver variability, however, was observed for breath-hold 3DE for ESV and EF. Comparison of breath-hold 3DE with MRI inner contour showed for end-diastolic volume, ESV, stroke volume, and EF, a percentual bias (+/- 2 SD) of, respectively, -13.5 +/- 26.9%, -17.7 +/- 47.8%, -10.6 +/- 43.6%, and -1.8 +/- 11.6%. Compared with the MRI outer contour, a significantly greater difference was observed, except for EF.

CONCLUSIONS

3DE using the freehand method is fast and highly reproducible for (serial) LV volume and EF measurement, and, hence, ideally suited for clinical decision making and trials. Breath-hold 3DE is superior to free-breathing 3DE regarding image quality and reproducibility. Compared with MRI, 3DE underestimates LV volumes, but not EF, which is mainly explained by differences in endocardial contour tracing by MRI (outer contour) and 3DE (inner contour) of the trabecularized endocardium. Underestimation is reduced when breath-hold 3DE is compared with inner contour analysis of the MRI dataset.

Effect of three-dimensional valve shape on the hemodynamics of aortic stenosis: three-dimensional echocardiographic stereolithography and patient studies

OBJECTIVES

This study tested the hypothesis that the impact of a stenotic aortic valve depends not only on the cross-sectional area of its limiting orifice but also on three-dimensional (3D) valve geometry.

BACKGROUND

Valve shape can potentially affect the hemodynamic impact of aortic stenosis by altering the ratio of effective to anatomic orifice area (the coefficient of orifice contraction [Cc]). For a given flow rate and anatomic area, a lower Cc increases velocity and pressure gradient. This effect has been recognized in mitral stenosis but assumed to be absent in aortic stenosis (constant Cc of 1 in the Gorlin equation).

METHODS

In order to study this effect with actual valve shapes in patients, 3D echocardiography was used to reconstruct a typical spectrum of stenotic aortic valve geometrics from doming to flat. Three different shapes were reproduced as actual models by stereolithography (computerized laser polymerization) with orifice areas of 0.5, 0.75, and 1.0 cm(2) (total of nine valves) and studied with physiologic flows. To determine whether valve shape actually influences hemodynamics in the clinical setting, we also related Cc (= continuity/planimeter areas) to stenotic aortic valve shape in 35 patients with high-quality echocardiograms.

RESULTS

In the patient-derived 3D models, Cc varied prominently with valve shape, and was largest for long, tapered domes that allow more gradual flow convergence compared with more steeply converging flat valves (0.85 to 0.90 vs. 0.71 to 0.76). These variations translated into differences of up to 40% in pressure drop for the same anatomic area and flow rate, with corresponding variations in Gorlin (effective) area relative to anatomic values. In patients, Cc was significantly lower for flat versus doming bicuspid valves (0.73 +/- 0.14 vs. 0.94 +/- 0.14, p < 0.0001) with 40 +/- 5% higher gradients (p < 0.0001).

CONCLUSIONS

Three-dimensional valve shape is an important determinant of pressure loss in patients with aortic stenosis, with smaller effective areas and higher pressure gradients for flatter valves. This effect can translate into clinically important differences between planimeter and effective valve areas (continuity or Gorlin). Therefore, valve shape provides additional information beyond the planimeter orifice area in determining the impact of valvular aortic stenosis on patient hemodynamics.

Quantitation of ventricular size and function: principles and accuracy of transthoracic rotational scanning

Two-dimensional echocardiography is a readily applicable method for the quantification of ventricular volumes. However, it is limited by assumptions regarding ventricular shape. Three-dimensional echocardiography has emerged as a more accurate and reproducible approach to ventricular volume and functional assessment compared with two-dimensional echocardiography. We review the principles of transthoracic rotational scanning and its clinical application for quantitative assessment of ventricular volume and function.

Volumetric analysis of the right ventricle in children with congenital heart defects: comparison of biplane angiography and transthoracic 3-dimensional echocardiography

BACKGROUND

Three-dimensional echocardiography is a non-invasive imaging technique. The fact that it permits volumetric analyses independently of geometrical assumptions makes it a putatively useful method for the precise measurement of the volumes of the irregularly shaped right ventricles in children. The aim of this study was to assess the feasibility of this method and its agreement with angiocardiography based estimates of right ventricular volume in children with congenital heart disease.

METHODS

We studied 102 children with congenital heart disease. The angiocardiographic right ventricular volumetry was performed using a biplanar technique using Simpson's rule and corrected with Lange's correction factors. The echo data sets were registered trans-thoracically with a rotating transmitter. Volumes were calculated after manual planimetry by adding the volumes of the individual slices.

RESULTS

Calculation of right ventricular volume echocardiographically was possible only in 34% of patients, mostly infants and toddlers. In comparison to angiocardiography, the measured volumes were 1.1 +/- 6.9 ml (19.5 +/- 34.1%) or 6.3 +/- 9.4 ml (42.5 +/- 33.6%) smaller during systole or diastole, respectively. The limits of agreement were -12.5 and 13.6 ml, or 12.45 and 25.15 ml during systole or diastole, respectively. When plotted to a logarithmical scale, the correlation coefficients r2 were 0.70 for systolic and 0.79 for diastolic measurements.

CONCLUSION

Transthoracic 3-dimensional echocardiography with a rotating transmitter is feasible for volumetry only in small children. The volumes measured were significantly smaller than the ones calculated from the angiocardiographic images. The correlation between the two methods is moderate.

Influence of echocardiographic scan plane location and number on the accuracy of three-dimensional left ventricular volume and shape determination

Quantitative 3-dimensional (3-D) echocardiography provides accurate assessment of left ventricular (LV) volume, shape, and function, but depends on manual endocardial border tracing. This study determined the minimal number of borders that need to be traced to obtain an accurate analysis of not only the volume of the left ventricle but also its shape, using the integrated methods for quantitative 3-D echocardiography developed by our laboratory. Transthoracic 3-D echocardiographic studies were obtained in 9 normal subjects and 6 patients with heart disease by freehand scanning. The LV endocardium was manually traced in 17 +/- 5 imaging planes and reconstructed in 3 dimensions. The volume and shape of each reconstruction were compared with values measured from surfaces reconstructed from 8 subsets containing 2 to 7 borders; each subset was acquired from different combinations of spatially distributed parasternal and apical views. Accurate measurements were obtained from data sets having > or = 5 borders, regardless of whether the image planes were predominantly apical or parasternal views. In conclusion, the LV border should be traced in > or = 5 imaging planes to obtain accurate measurements of volume and shape. The piece-wise smooth reconstruction method and freehand scanning using a magnetic field tracing system allow the borders to be acquired from whatever combination of acoustic windows and views provides optimal image quality.