Three-dimensional echocardiographic reconstruction of right ventricular volume: in vitro comparison with two-dimensional methods

[Comparative assessment of the effects of dobutamine and levosimendan on right ventricular ejection fraction in patients with biventricular heart failure]

Aim    The primary objective of this study was to comparatively assess the effects of levosimendan and dobutamine on RVEF, right ventricular diastolic function, and hormonal balance in patients with biventricular heart failure. The secondary objective was to investigate the relationship between the RVEF and the peak systolic velocity (Sa), an indicator of right ventricular systolic function, as measured by tissue Doppler echocardiography from the tricuspid annulus, and by the tricuspid annular plane systolic excursion (TAPSE).Material and Methods    The population of this cross-sectional, single-center, prospective study was comprised of 81 patients, who between December 2019 and January 2022, applied to the study health institution with diagnosis of ADHF. The study sample included 67 biventricular heart failure patients with left ventricular ejection fraction (LVEF) <35 % and RVEF <50 %, as measured by the ellipsoidal shell model, and who met the other study inclusion criteria. Of these 67 patients, 34 were treated with levosimendan, and 33 were treated with dobutamine. RVEF, LVEF, Sa, peak early (Ea) and peak late (Aa) annular velocities, Ea / Aa ratio, TAPSE, systolic pulmonary artery pressure (SPAP), n-terminal pro-brain natriuretic peptide (NT-pro BNP), and functional capacity (FC) were measured before treatment and at 48 hrs of treatment. The within group pre- and post-treatment differences (Δs) of these variables were compared.Results    RVEF, SPAP, and BNP, and FC significantly improved in both treatment groups (p<0.05 for all). Sa (p<0.01), TAPSE (p<0.01), LVEF (p<0.01), and Ea / Aa (p<0.05) improved only in the levosimendan group. The pre- and post-treatment Δs for RVEF, LVEF, SPAP, Sa, TAPSE, FC, and Ea / Aa were higher in the levosimendan group than in the dobutamine group (p<0.05 for all).Conclusion    Compared to dobutamine, levosimendan produced greater improvement in right ventricular systolic and diastolic function in patients with biventricular heart failure and in need of inotropic therapy support.

3D Echo systematically underestimates right ventricular volumes compared to cardiovascular magnetic resonance in adult congenital heart disease patients with moderate or severe RV dilatation

BACKGROUND

Three dimensional echo is a relatively new technique which may offer a rapid alternative for the examination of the right heart. However its role in patients with non-standard ventricular size or anatomy is unclear. This study compared volumetric measurements of the right ventricle in 25 patients with adult congenital heart disease using both cardiovascular magnetic resonance (CMR) and three dimensional echocardiography.

METHODS

Patients were grouped by diagnosis into those expected to have normal or near-normal RV size (patients with repaired coarctation of the aorta) and patients expected to have moderate or worse RV enlargement (patients with repaired tetralogy of Fallot or transposition of the great arteries). Right ventricular end diastolic volume, end systolic volume and ejection fraction were compared using both methods with CMR regarded as the reference standard

RESULTS

Bland-Altman analysis of the 25 patients demonstrated that for both RV EDV and RV ESV, there was a significant and systematic under-estimation of volume by 3D echo compared to CMR. This bias led to a mean underestimation of RV EDV by -34% (95%CI: -91% to + 23%). The degree of underestimation was more marked for RV ESV with a bias of -42% (95%CI: -117% to + 32%). There was also a tendency to overestimate RV EF by 3D echo with a bias of approximately 13% (95% CI -52% to +27%).

CONCLUSIONS

Statistically significant and clinically meaningful differences in volumetric measurements were observed between the two techniques. Three dimensional echocardiography does not appear ready for routine clinical use in RV assessment in congenital heart disease patients with more than mild RV dilatation at the current time.

Dynamic assessment of right ventricular volumes and function by real-time three-dimensional echocardiography: a comparison study with magnetic resonance imaging in 100 adult patients

BACKGROUND

The aim of this study was to validate a novel real-time three-dimensional echocardiographic (RT3DE) analysis tool for the determination of right ventricular volumes and function in unselected adult patients.

METHODS

A total of 100 consecutive adult patients with normal or pathologic right ventricles were enrolled in the study. A dynamic polyhedron model of the right ventricle was generated using dedicated RT3DE software. Volumes and ejection fractions were determined and compared with results obtained on magnetic resonance imaging (MRI) in 88 patients with adequate acquisitions.

RESULTS

End-diastolic, end-systolic, and stroke volumes were slightly lower on RT3DE imaging than on MRI (124.0 +/- 34.4 vs 134.2 +/- 39.2 mL, P < .001; 65.2 +/- 23.5 vs 69.7 +/- 25.5 mL, P = .02; and 58.8 +/- 18.4 vs 64.5 +/- 24.1 mL, P < .01, respectively), while no significant difference was observed for ejection fraction (47.8 +/- 8.5% vs 48.2 +/- 10.8%, P = .57). Correlation coefficients on Bland-Altman analysis were r = 0.84 (mean difference, 10.2 mL; 95% confidence interval [CI], -31.3 to 51.7 mL) for end-diastolic volume, r = 0.83 (mean difference, 4.5 mL; 95% CI, -23.8 to 32.9 mL) for end-systolic volume, r = 0.77 (mean difference, 5.7 mL; 95% CI, -24.6 to 36.0 mL) for stroke volume, and r = 0.72 (mean difference, 0.4%; 95% CI, -14.2% to 15.1%) for ejection fraction.

CONCLUSION

Right ventricular volumes and ejection fractions as assessed using RT3DE imaging compare well with MRI measurements. RT3DE imaging may become a time-saving and cost-saving alternative to MRI for the quantitative assessment of right ventricular size and function.

Right ventricle three-dimensional echography in corrected tetralogy of fallot: accuracy and variability

AIMS

To evaluate right ventricular (RV) volume and ejection fraction (EF) in adult normal subjects and repaired tetralogy of Fallot (ToF) with 3D trans-thoracic echocardiography (3DE) and a semi-automatic border detection algorithm.

METHODS AND RESULTS

Fourteen healthy volunteers and 20 patients with repaired ToF (mean age 31 +/- 14) underwent 3DE and MRI within the same day. Right ventricular end-systolic volume (ESV) and end-diastolic volume (EDV) and EF were measured by two observers using 3DE and compared with MRI measurements. Intra- and interobserver variability of 3DE and agreement between both methods were evaluated using Bland-Altman analysis. Over or underestimation of 3DE in comparison to MRI was assessed using paired t-test. Intra- and interobserver variability of 3DE was excellent with intraclass coefficient of correlation (ICC) ranging from 0.85 to 0.99 and from 0.85 to 0.98, respectively. Three-dimensional echocardiography underestimated ESV and EDV (P < 0.001) but agreement between 3DE and MRI was excellent (ICC = 0.88 and 0.87, respectively). Ejection fraction was 47.7 +/- 7.8 with 3DE and 47.9 +/- 6.7 with MRI, agreement between both methods was good (ICC = 0.72).

CONCLUSION

Three-dimensional echocardiography combined to semi-automated quantification software shows fair agreement with MRI for RV volumes and EF measurement in patients with repaired ToF and adequate intra- and interobserver variability. These results suggest applicability for serial follow-up of patients with right heart congenital disease. However, the accuracy of 3DE echo diminishes with larger RV volumes, in part due to current difficulty to include the entire RV in the imaged sector. Technical progress in transducers beam geometry is likely to address this issue.

Assessment of right ventricular function by real-time three-dimensional echocardiography improves accuracy and decreases interobserver variability compared with conventional two-dimensional views

AIMS

Two-dimensional echocardiographic (2DE) assessment of right ventricular (RV) function is difficult, often resulting in inconsistent RV evaluation. Real-time three-dimensional echocardiography (RT3DE) allows the RV to be viewed in multiple planes, which can potentially improve RV assessment and limit interobserver variability when compared with 2DE.

METHODS AND RESULTS

Twenty-five patients underwent 2DE and RT3DE. Views of 2DE (RV inflow, RV short axis, and apical four-chamber) were compared with RT3DE views by four readers. RT3DE data sets were sliced from anterior-posterior (apical view) and from base to apex (short axis) to obtain six standardized planes. Readers recorded the RV ejection fraction (RVEF) from 2DE and RT3DE images. RVEF recorded by RT3DE (RVEF(3D)) and 2D (RVEF(2D)) were compared with RVEF by disc summation (RVEF(DS)), which was used as a reference. Interobserver variability among readers of RVEF(3D) and RVEF(2D) was then compared. Overall, mean RVEF(DS), RVEF(3D), and RVEF(2D) were 37 +/- 11%, 38 +/- 10%, 41 +/- 10%, respectively. The mean difference of RVEF(3D)-RVEF(DS) was significantly less than RVEF(2D)-RVEF(DS) (3.7 +/- 4% vs. 7.1 +/- 5%, P = 0.0066, F-test). RVEF(3D) correlated better with RVEF(DS) (r = 0.875 vs. r = 0.69, P = 0.028, t-test). RVEF(3D) was associated with a 39% decrease in interobserver variability when compared with RVEF(2D) [standard deviation of mean difference: 3.7 vs. 5.1, (RT3DE vs. 2DE), P = 0.018, t-test].

CONCLUSIONS

RT3DE provides improved accuracy of RV function assessment and decreases interobserver variability when compared with 2D views.

Three-dimensional adult echocardiography: where the hidden dimension helps

The introduction of three-dimensional (3D) imaging and its evolution from slow and labor-intense off-line reconstruction to real-time volumetric imaging is one of the most significant developments in ultrasound imaging of the heart of the past decade. This imaging modality currently provides valuable clinical information that empowers echocardiography with new levels of confidence in diagnosing heart disease. One major advantage of seeing the additional dimension is the improvement in the accuracy of the evaluation of cardiac chamber volumes by eliminating geometric modeling and the errors caused by foreshortened views. Another benefit of 3D imaging is the realistic views of cardiac valves capable of demonstrating numerous pathologies in a unique, noninvasive manner. This article reviews the major technological developments in 3D echocardiography and some of the recent literature that has provided the scientific basis for its clinical use.

Three-Dimensional Echocardiographic Evaluation of the Heart Chambers: Size, Function, and Mass

The major advantage of three-dimensional (3D) ultrasound imaging of the heart is the improvement in the accuracy of the echocardiographic evaluation of cardiac chamber volumes, which is achieved by eliminating the need for geometric modeling and the errors caused by foreshortened 2D views. In this article, we review the literature that has provided the scientific basis for the clinical use of 3D ultrasound imaging of the heart in the assessment of cardiac chamber size, function, and mass, and discuss its potential future applications.

Normal Values of Right Ventricular Size and Function by Real-time 3-Dimensional Echocardiography: Comparison with Cardiac Magnetic Resonance Imaging

BACKGROUND

Assessment of right ventricular function by 2-dimensional echocardiography (2DECHO) is difficult because of its complex shape. Real-time 3-dimensional echocardiography (RT3DECHO) may be superior.

METHODS

End-diastolic volume, end-systolic volume, stroke volume, and ejection fraction obtained by 2DECHO, RT3DECHO short-axis disk summation (DS), and RT3DECHO apical rotation were compared with cardiac magnetic resonance imaging in 71 healthy individuals.

RESULTS

RT3DECHO DS showed less volume underestimation compared with 2DECHO and RT3DECHO apical rotation. Test-retest variability for RT3DECHO DS end-diastolic volume, end-systolic volume, stroke volume, and ejection fraction were 3.3%, 8.7%, 10%, and 10.3%, respectively. Normal reference ranges of indexed volumes (mean +/- 2SD) for right ventricular end-diastolic volume, end-systolic volume, stroke volume, and ejection fraction were 38.6 to 92.2 mL/m(2), 7.8 to 50.6 mL/m(2), 22.5 to 42.9 mL/m(2), and 38.0% to 65.3%, respectively, for women and 47.0 to 100 mL/m(2), 23.0 to 52.6 mL/m(2), 14.2 to 48.4 mL/m(2), and 29.9% to 58.4%, respectively, for men.

CONCLUSIONS

RT3DECHO DS is superior to RT3DECHO apical rotation and 2DECHO for right ventricular quantification, and performs acceptably when compared with cardiac magnetic resonance imaging in healthy individuals.

Cardiac MRI Is an Important Complementary Tool to Doppler Echocardiography in the Management of Patients with Pulmonary Regurgitation

Cardiac MRI (CMR) is a noninvasive diagnostic tool with comprehensive capabilities similar to that of two-dimensional echocardiography with Doppler. In addition to the ability to evaluate the etiology and severity of pulmonary valve regurgitation (PR), CMR is well designed to serially monitor the impact of the PR on the right ventricle (RV). Importantly, RV dilation and dysfunction is a critical determinate to time surgical intervention. CMR gives the silent RV, suffering from PR, a voice.

Three-Dimensional Echocardiography

Over the past 3 decades, echocardiography has become a major diagnostic tool in the arsenal of clinical cardiology for real-time imaging of cardiac dynamics. More and more, cardiologists' decisions are based on images created from ultrasound wave reflections. From the time ultrasound imaging technology provided the first insight into the human heart, our diagnostic capabilities have increased exponentially as a result of our growing knowledge and developing technology. One of the most significant developments of the last decades was the introduction of 3-dimensional (3D) imaging and its evolution from slow and labor-intense off-line reconstruction to real-time volumetric imaging. While continuing its meteoric rise instigated by constant technological refinements and continuing increase in computing power, this tool is guaranteed to be integrated in routine clinical practice. The major proven advantage of this technique is the improvement in the accuracy of the echocardiographic evaluation of cardiac chamber volumes, which is achieved by eliminating the need for geometric modeling and the errors caused by foreshortened views. Another benefit of 3D imaging is the realistic and unique comprehensive views of cardiac valves and congenital abnormalities. In addition, 3D imaging is extremely useful in the intraoperative and postoperative settings because it allows immediate feedback on the effectiveness of surgical interventions. In this article, we review the published reports that have provided the scientific basis for the clinical use of 3D ultrasound imaging of the heart and discuss its potential future applications.

Quantitation of Right Ventricular Volumes and Ejection Fraction by Three-Dimensional Echocardiography in Patients: Comparison with Magnetic Resonance Imaging and Radionuclide Ventriculography

Three-dimensional echocardiography (3DE) provides volumetric measurements without geometric assumptions. Volume-rendered 3DE has been shown to be accurate for the measurement of right ventricular (RV) volumes in vitro and in animal studies; however, few data are available regarding its accuracy in patients. This study examined the accuracy of 3DE for quantitation of RV volumes and ejection fraction (EF) in patients, compared to magnetic resonance imaging (MRI) and radionuclide ventriculography (RNV). Twenty patients underwent MRI, gated equilibrium RNV, and 3DE using rotational acquisition from both the transesophageal and transthoracic approaches. RV volumes and EF were calculated from the 3DE data using multislice analysis (true Simpson's rule). RV volumes calculated by MRI (end-diastolic volume (EDV) 109.4 +/- 34.3 mls, end-systolic volume (ESV) 59.6 +/- 31.0 mls, and EF 47.7 +/- 17.1%) agreed closely with 3DE. For transesophageal echocardiography, EDV was 108.1 +/- 29.7 mls (r = 0.86, mean difference 1.3 +/- 17.8 mls); ESV was 62.5 +/- 23.8 mls (r = 0.85, mean difference 2.8 +/- 15.1 mls); and EF was 43.2 +/- 11.7% (r = 0.84, mean difference 4.5 +/- 9.7%). For transthoracic echocardiography, EDV was 107.7 +/- 27.5 mls (r = 0.85, mean difference 1.6 +/- 18.2 mls); ESV was 59.7 +/- 22.1 mls (r = 0.93, mean difference 3.2 +/- 19.6 mls); and EF was 45.2 +/- 11.5% (r = 0.86, mean difference 2.0 +/- 9.4%). There were close correlations, small mean differences and narrow limits of agreement between RNV-derived EF (43.4 +/- 12.1%) and both transesophageal (r = 0.95 mean difference 0.2 +/- 3.7%) and transthoracic 3DE (r = 0.95, mean difference 1.8 +/- 5.4%). Three-dimensional echocardiography is a promising new method of calculating RV volumes and EF, comparing well with MRI and RNV. The accuracy of transthoracic 3DE was comparable to that of the transesophageal approach. Three-dimensional echocardiography has the potential to be useful in the clinical assessment of RV disorders.

Modified RV short axis series--a new method for cardiac MRI measurement of right ventricular volumes

PURPOSE

The current standard image orientation employed in the MRI assessment of right ventricular volumes uses a series of short axis cine acquisitions located with respect to a horizontal long axis view with the first slice placed across the atrio-ventricular valve plane at end diastole. Inherent inaccuracies are encountered with the use of this image orientation due to difficulty in defining the tricuspid valve and the border between atrium and ventricle on the resultant images. Our experience indicates that because the tricuspid valve is usually not in-plane in the slice the atrio-ventricular margin is difficult to distinguish. This leads to inaccuracies in measurements at the base of the RV and miscalculation of the RV volume. The purpose of this study was to assess an alternative method of image orientation aimed at increasing the accuracy of RV volume measurements using current commercially available CMRI sequences. This technique, the modified RV short axis series, is oriented to the outflow tract of the right ventricle.

METHOD

We undertook a prospective study of 50 post cardiac transplant patients. A series of LV short axis multi-slice cine acquisition FIESTA images was acquired using the current standard technique. From this data set, LV and RV stroke volumes were derived on an Advantage Windows workstation using planimetry of the endocardial and epicardial borders in end systole and end diastole. Our new technique involved obtaining a set of multi-slice cine acquisition FIESTA images in a plane perpendicular to a line from the centre of the pulmonary valve to the apex of the RV. Planimetry of the RV was then performed and a stroke volume calculated using the same method of analysis. RV stroke volumes obtained from both techniques were compared with LV stroke volumes. Three operators independently derived RV data sets.

RESULTS

On the images acquired with the new technique, the tricuspid valve was easier to define leading to more accurate and reproducible planimetry of ventricular borders. RV stroke volumes calculated from the new method showed better agreement with LV stroke volumes than with the current method. These results were consistent across the three operators.

CONCLUSIONS

This new method improves visualisation of the tricuspid valve and makes analysis easier and less prone to operator error than the current standard technique for MRI assessment of RV volumes.

Transesophageal 3-dimensional versus cross-sectional echocardiographic assessment of the volume of the right ventricle in children with atrial septal defects

The study was designed to investigate the value of assessing right ventricular volume by transoesophageal 3-dimensional echocardiographic techniques compared with the standard transoesophageal cross-sectional approach. Echocardiography was performed using a multiplane probe. The 3-dimensional data sets were reconstructed after electrocardiographic and respiratory gated scanning, calculating the 3-dimensional volumes by the method of multiple slices. Cross-sectional determination of volume was performed using a modified area-length method, and the biplane multiple slice method following Simpson's rule. We studied 15 patients, with ages ranging from 6 to 19 years, and body surface areas from 1.1 to 1.67 square metres. It proved possible top determine volumes with both methods in all patients. As determined by 3-dimensional echo, volumes were greater, being 113.0 plus or minus 61.2 millilitres at end-systole, and 61.7 plus or minus 36 millilitres at end-diastole, than those calculated from cross-sectional images using Simpson's rule, which gave values of 92.5 plus or minus 52 millilitres, and 41.3 plus or minus 22 millilitres. Compared to the values obtained using the area-length method, at 116.9 plus or minus 61 millilitres, and 60.3 plus or minus 30 millilitres, there were only small differences at end-systole, with a bias of 1.4, and limits of agreement of 20.9 millilitres, as well as at end-diastole, when bias was minus 3.8, and limits of agreement 22.3 millilitres. Correlation was also good, with coefficients of 0.93, and 0.91, respectively. The mean difference between the volumes by 3-dimensional acquisition and the multiple slice method was larger, with higher limits of agreement, at end-diastole showing bias of 20.5, and limits of agreement of 30.1 millilitres, and for end-systole bias of 20.4, and limits of agreement of 32.2 millilitres. Our data confirm that cross-sectional echocardiographic assessment of right ventricular volumes in children with atrial septal defects is quick, and reasonably reliable in clinical practice when employing the area-length method.

Feasibility and variability of three dimensional echocardiography in arrhythmogenic right ventricular dysplasia/cardiomyopathy

Arrhythmogenic right ventricular dysplasia (ARVD/C) is a genetic cardiomyopathy characterized by fibrous fatty replacement of the right ventricular (RV) myocardium, leading to progressive RV failure and ventricular arrhythmias in young athletes. This study evaluated whether transthoracic, real-time, 3-dimensional echocardiography (3DE) can adequately assess RV morphology and function in ARVD/C by comparing 3DE with cardiac magnetic resonance (CMR), the current reference standard. Three-dimensional echocardiography was prospectively performed in 58 patients (23 with ARVD/C, 20 first-degree relatives with no ARVD/C, 8 with idiopathic ventricular tachycardia with no ARVD/C, and 7 healthy volunteers). All patients, except 15 patients with ARVD/C with implanted defibrillators, also underwent CMR. Three-dimensional echocardiography and CMR-derived RV volumes and ejection fractions were obtained by offline data analysis by blinded, independent observers. The mean age of the study group was 37 +/- 11 years (30 men). The feasibility of 3DE was high, and analyzable images were obtained in all subjects. Three-dimensional echocardiography revealed a wide variety of RV morphologic abnormalities in ARVD/C. There was a good correlation between 3DE and CMR for RV end-systolic volume (r = 0.72, p = 0.0001), RV end-diastolic volume (r = 0.50, p = 0.0001), and the RV ejection fraction (r = 0.88, p = 0.001). We found high intraobserver and moderate interobserver correlations for 3DE estimations of volumes and ejection fractions. In conclusion, 3DE measurements of RV volumes and ejection fractions closely correlate with CMR values and may be useful in the follow-up of patients with ARVD/C.

MR imaging assessment of cardiac function

Magnetic resonance (MR) imaging is an accurate and reproducible technique for assessment of ventricular function. Although echocardiography is the mainstay for evaluation of cardiac function, dobutamine stress MR imaging has been shown to be as safe as echocardiography for patients with coronary artery disease and more accurate in patients with suboptimal echocardiographic image quality. This article reviews MR imaging techniques, methods of pharmacologic stress, and clinical applications for assessment of cardiac function, primarily left ventricular function.

RV functional imaging: 3-D echo-derived dynamic geometry and flow field simulations

We describe a novel functional imaging approach for quantitative analysis of right ventricular (RV) blood flow patterns in specific experimental animals (or humans) using real-time, three-dimensional (3-D) echocardiography (RT3D). The method is independent of the digital imaging modality used. It comprises three parts. First, a semiautomated segmentation aided by intraluminal contrast medium locates the RV endocardial surface. Second, a geometric scheme for dynamic RV chamber reconstruction applies a time interpolation procedure to the RT3D data to quantify wall geometry and motion at 400 Hz. A volumetric prism method validated the dynamic geometric reconstruction against simultaneous sonomicrometric canine measurements. Finally, the RV endocardial border motion information is used for mesh generation on a computational fluid dynamics solver to simulate development of the early RV diastolic inflow field. Boundary conditions (tessellated endocardial surface nodal velocities) for the solver are directly derived from the endocardial geometry and motion information. The new functional imaging approach may yield important kinematic information on the distribution of instantaneous velocities in the RV diastolic flow field of specific normal or diseased hearts.

Three-dimensional echocardiographic determination of cardiac output at rest and under dobutamine stress: comparison with thermodilution measurements in the ischemic pig model

Determination of cardiac output is a potentially important clinical application of three-dimensional (3-D) echocardiography since it could replace invasive measurements with the Swan-Ganz-catheter. To date, there are no studies available to determine whether cardiac output measured by thermodilution can be predicted reliably under changing hemodynamic conditions. Fifteen pigs with ischemic myocardium were examined under four hemodynamic conditions at rest and under pharmacological stress with 5, 10, and 20 microg/kg/min dobutamine. The 3-D datasets were recorded by means of transesophageal echocardiography. The endocardial definition was enhanced by administering the contrast agent FS069 (Optison). Cardiac output was calculated as the product of stroke volume (end-diastolic - end-systolic volume) and heart rate. The invasive measurements were performed with a continuous thermodilution system. In general, there was moderate correlation between 3-D echocardiography and thermodilution(r = 0.72, P < 0.001). At rest, the 3-D echocardiographic measurements were slightly but significantly lower than the invasive measurements (mean difference 0.6 +/- 0.5L/min,P < 0.001). Under stress with 5, 10, and 20 microg/kg/min dobutamine, there was a marked increase in the deviation (1.3 +/- 0.5L/min,P < 0.001; 1.6 +/- 0.7 L/min,P < 0.001; and 2.1 +/- 1.1L/min,P < 0.001, respectively). The deviation was based on two factors: (1). Under stress, the decreasing number of frames per cardiac cycle acquired with 3-D echocardiography led to imprecise recording of end-diastolic and end-systolic volumes, and thus to an underestimation of cardiac output. At least 30 frames per cardiac cycle are needed to eliminate this effect. (2). There is a systematic difference between 3-D echocardiographic and invasive measurements, which is independent of the imaging rate. This is based on an overestimation of the true values by thermodilution. In conclusion, cardiac output can be determined correctly by 3-D echocardiography for normal heart rates at rest. At elevated heart rates, the temporal resolution of 3-D systems currently available is not adequate for reliable determination. In performing and evaluating future clinical comparative studies, the systematic difference between 3-D echocardiography and thermodilution, based on overestimation by thermodilution, must be taken into account.

Accuracy of real-time three-dimensional echocardiography for quantifying right ventricular volume: static and pulsatile flow studies in an anatomic in vitro model

OBJECTIVE

The complex structural geometry of the right ventricle hinders accurate assessment of right ventricular volume and function on conventional two-dimensional echocardiography. We sought to evaluate the accuracy of real-time three-dimensional echocardiography for quantifying the volume of the right ventricle in an in vitro experimental study.

METHODS

We developed 39 anatomically accurate latex phantoms of human and porcine right ventricles (range, 24-108 mL) for 39 static and 10 pulsatile models. Real-time three-dimensional scanning was performed with the models placed in a water bath and with a 3.5-MHz probe. In the dynamic models a pulsatile flow pump generated 2 different stroke volumes (29 and 64 mL/beat). Static chamber volumes and stroke volumes were verified by water displacement, which served as a reference standard. Three-dimensional echo right ventricle volumes were determined by tracing derived B- and C-scans, using the Simpson rule.

RESULTS

Multiple regression analyses showed an excellent correlation between real-time three-dimensional echocardiographic determinations and the static volumes (B-scan, r = 0.99; C-scan, r = 0.98; P < .001), as well as stroke volumes in the dynamic model (B-scan, r = 0.90; C-scan, r = 0.86; P < .001). However, the C-scans tended to underestimate cavity and stroke volumes more than the B-scans (mean difference for static volume: B-scan, 1.4% +/- 9.8%; C-scan, -7.4% +/- 8.0%; P < .001; mean difference for stroke volumes: B-scan, 3.0% +/- 19.1%; C-scan, -2.5% +/- 20.9%; P < .001).

CONCLUSIONS

Real-time three-dimensional echocardiography can accurately quantify right ventricle cavity volumes and stroke volumes without geometric assumptions.

Three-dimensional echocardiographic measurement of left and right ventricular mass and volume: in vitro validation

INTRODUCTION

Three-dimensional (3D) echocardiography has been shown to offer highly accurate measurements of left ventricular (LV) volume and mass. The present study evaluated the accuracy of 3D surface reconstruction by the piecewise smooth subdivision method in measuring volume and mass not only in the LV but also in the more complexly shaped right ventricle (RV).

METHODS

3D echo scans were obtained of in vitro LV's (n = 15) and RVs (n = 10). From digitized images, ventricular borders were traced and used in surface reconstructions. Mass and volume determined from the reconstructions were compared to true volume and mass determined prior to imaging. Additionally casts of two RVs were made and laser-scanned. Distances between the laser-identified points on the RV surface and the corresponding 3D echo reconstructions were measured.

RESULTS

3D LV volume agreed well with the true volume (y = 0.99x + 1.73, r = 0.99, SEE = 3.35 ml, p < 0.0001), as did 3D LV mass (y = 0.99x - 4.71, r = 0.99, SEE = 9.85 g, p < 0.0001). 3D RV volume overestimated true volume (y = 1.11x + 1.77, r = 0.99, SEE = 3.36 ml, p < 0.001) by 6.23+/-3.70 ml (p < 0.0001). 3D mass agreed well with RV mass (y = 0.78x + 17.32, r2 = 0.93, SEE = 3.54 g, p < 0.0001). 3D echo reconstructions matched the laser-scanned RV closely with residual distances of 1.1+/-0.9 and 1.4+/-1.2 mm, respectively.

CONCLUSIONS

3D echo using freehand scanning combined with surface reconstruction by the piecewise smooth subdivision surface method enables accurate determination of LV mass and volume, of RV mass and volume, and of the RV's complex shape.

Real-time 3-dimensional echocardiographic evaluation of left ventricular volume: correlation with magnetic resonance imaging--a validation study

BACKGROUND

The purpose of our study was to validate the ability of real-time 3-dimensional echocardiography (RT3D) to measure cardiac volume.

METHODS

We studied 25 patients with various cardiac disorders who had a regular heart rhythm and a good precordial echocardiographic window. Each patient underwent complete transthoracic echocardiography (TTE), RT3D, and magnetic resonance imaging (MRI) studies. Left ventricular dimension was calculated from slices of the whole left ventricle obtained by 7 different equidistant azimuth tilts. Planimetry of the endocardial (for volume data) and epicardium (for mass data) surface was performed for each azimuth tilt. The left ventricular end-diastolic volume (LVEDV) and the left ventricular end-systolic volume (LVESV) were calculated. The cardiac mass data were derived with the formula (Epicardial volume - LVEDV) x 1.055. The parameters of LVEDV, LVESV, stroke volume, ejection fraction, and cardiac mass were compared with those derived from MRI.

RESULTS

No statistically significant differences were found between the data from RT3D and MRI (P > or =.05). Good correlations were found between these two methods for left ventricle volume and mass measurements (r from 0.92 to 0.99). However, a weaker correlation was found with larger chamber sizes because extrapolation was necessary for the volume of myocardial segments that were not covered by the small sector angle.

CONCLUSIONS

For data acquisition, RT3D is faster than either TTE or MRI. It is also better than MRI for measuring cardiac volume and mass. To improve results with larger cardiac chamber sizes, enlargement of the sector angle will be necessary.

Superiority of 3-dimensional versus 2-dimensional echocardiography for left ventricular volume assessment in small piglet hearts

To evaluate the accuracy of 3-dimensional (3D) echocardiography in the estimation of left ventricular (LV) volume in vivo, we studied 15 newborn piglets ranging in weight from 2.6 to 11.8 kg. Measurements of beating LV volumes by 3D echocardiograms were compared with measurements by conductance catheter and transthoracic 2-dimensional (2D) echocardiograms with the use of Simpson's rule. The results of both 3D and 2D echocardiograms correlated strongly with the actual volume (r = 0.98 and 0.95 for LV end-diastolic volume, and 0.998 and 0.95 for LV end-systolic volume, respectively). However, the standard error of estimate (SEE) for 2D echocardiography was larger than for 3D. The SEE values for LV end-diastolic volume for 2D and 3D echocardiograms were 2.30 mL and 1.85 mL, respectively, and 1.52 mL and 0.5 mL for LV end-systolic volume. We conclude that 3D echocardiography not only accurately measures LV volume and systolic function in a newborn heart, it is more precise than measurements from 2D echocardiography in the assessment of small beating hearts.

Reconstruction of 3-dimensional right ventricular shape and volume from 3 orthogonal planes

This study validates a reconstructive technique that describes 3-dimensional right ventricular (RV) shape and volume with the use of 3 standard echocardiographic planes. The volume of 24 cast models of lamb right ventricles (12 normal, 12 hypertensive) was determined by water displacement. Reconstruction of the cast shapes was calculated from 2 sets of digitized data: cast cross-sectional digitized tracings and echocardiographic cross-sectional tracings. Regional volume ratios from both data sets were assessed to quantitatively specify RV regional volume differences between normotensive and hypertensive right ventricles. This method described the 3-dimensional RV shape with no differences between reconstructed volumes and true volumes for either normotensive or hypertensive casts. Between hypertensive and normal groups, regional volume ratios yielded a difference in free wall ratios that was observed to be greater in the hypertensive cast group (P =.007).

In Vitro Feasibility and Accuracy of Three-Dimensional Echocardiography for Ventricular Volume Assessment in Very Small Hearts

To evaluate the in vitro accuracy of three-dimensional echocardiography (3-DE) for estimation of ventricular volume in very small hearts, left ventricular (LV) volume was determined by 3-DE in the excised hearts of 10 guinea pigs and 10 rabbits, and right ventricular (RV) volume was determined in 20 rabbits. The effect of edge enhancement, Sigma filter, and slice distance (1 mm versus 0.5 mm) was assessed in each heart. True volumes were obtained from ventricular casts. Mean cast volume was 1.38 +/- 0.83 mL for LVs and 1.63 +/- 1.01 mL for RVs. Correlations between 3-DE and true volumes were r > 0.99 (P < 0.0001) for both ventricles. Accuracy was not affected by ventricular type, slice distance, or Sigma filter. Mean percent difference from true volume was significantly less (P = 0.03) with edge enhancement. Ventricular volume can be assessed reliably by 3-DE in very small hearts. The edge enhancement feature improved the accuracy of the measurements.

Real-time, three-dimensional echocardiography: feasibility of dynamic right ventricular volume measurement with saline contrast

BACKGROUND

The asymmetry and complex shape of the right ventricle have made it difficult to determine right ventricular (RV) volume with 2-dimensional echocardiography. Three-dimensional cardiac imaging improves visualization of cardiac anatomy but is also complex and time consuming. A newly developed volumetric scanning system holds promise of obviating past limitations.

METHODS

Real-time, transthoracic 3-dimensional echocardiographic images of the right ventricle were obtained with a high-speed volumetric ultrasound system that uses a 16:1 parallel processing schema from a 2.5 MHz matrix phased-array scanner to interrogate an entire pyramidal volume in real time. The instrumentation was used to measure RV volume in 8 excised canine hearts; dynamic real-time 3-dimensional images were also obtained from 14 normal subjects.

RESULTS

Three-dimensional images were obtained in vitro and in vivo during intravenous hand-agitated saline injection to determine RV volumes. The RV volumes by real-time 3-dimensional echocardiography are well correlated with those of drained in vitro (y = 1.26x - 9.92, r = 0.97, P <.0001, standard error of the estimate = 3.26 mL). For human subjects, the end-diastolic and end-systolic RV volumes were calculated by tracing serial cross-sectional, inclined C scans; functional data were validated by comparing the scans with conventional 2-dimensional echocardiographic indexes of left ventricular stroke volume.

CONCLUSIONS

These data indicate that RV volume measurements of excised heart by real-time 3-dimensional echocardiography are accurate and that beat-to-beat RV quantitative measurement applying this imaging method is possible. The new application of real-time 3-dimensional echocardiography presents the opportunity to develop new descriptors of cardiac performance.

Vein graft surveillance with scanhead tracking duplex ultrasound imaging: a preliminary report

A severe arterial occlusion in the leg usually is bypassed by implanting a saphenous vein harvested from the limb. Once implanted, the vein functions well but over time may develop stenoses that may lead to occlusion. In order to detect and correct the stenoses that may lead to graft failure, frequent surveillance of the vein graft is required. A new ultrasound imaging method was developed to display the panoramic view of the vein graft in combination with its blood flow velocity waveform for surveillance. The panoramic view is the projection (ray-casting) image of multiple B-mode images with sequential longitudinal view of the vein graft. The velocity waveform also is recorded along the vessel with pulsed Doppler ultrasound. The acquired images and waveforms from the ultrasound scanner are registered individually in three-dimensional space with an electromagnet-based position and orientation sensor located on the scanhead. A prominent point on the scar from the surgery is used as the fiducial mark for spatial registration, so that the same lesion in the vein graft can be tracked automatically at each visit for retrospective study.

An echocardiographic and magnetic resonance imaging comparative study of right ventricular volume determination

Assessment of right ventricular volume and function is important in many clinical settings involving heart or lung disease. However, the complexity of the right ventricular anatomy has prevented accurate volume determination by two-dimensional echocardiography. In the present study, 5 models incorporating standard echocardiographic views, were used to determine right ventricular volume in 10 human subjects. Two models were contingent on the true crescentic appearance of the right ventricle, whereas the remaining 3 calculated the right ventricular volume as a pyramid, an ellipsoid or other tapering geometrical figures, respectively. Subsequently, echocardiographic right ventricular volumes were compared to magnetic resonance imaging derived volumes. Correlation analysis and agreement measurement between the echocardiographic and magnetic resonance end-diastolic volume were performed in 10 out of 10 subjects and in 9 out of 10 subjects for the end-systolic volume. The 2 crescentic models resulted in the most reliable estimation of right ventricular volume. Those findings suggest that models based on right ventricular anatomical landmarks are feasible and should be preferred in echocardiographic studies.

Determination of left ventricular mass and circumferential wall thickness by three-dimensional reconstruction: in vitro validation of a new method that uses a multiplane transesophageal transducer

Elevated left ventricular mass and increased wall thickness have important prognostic implications in clinical medicine. However, these parameters have been incompletely characterized by one- and two-dimensional echocardiography. Therefore this study was performed to validate in vitro measurement of left ventricular mass and circumferential wall thickness with a multiplane transesophageal transducer and three-dimensional reconstruction. Results for mass measurements were also compared with a standard method for the determination of left ventricular mass, the Penn convention. Fourteen necropsied left ventricles were scanned in a water bath by a volume-rendering, three-dimensional reconstruction system. There was an excellent correlation and high agreement for determination of three-dimensional left ventricular mass (r = 0.98; standard error of the estimate [SEE] = 9.6 gm; y = 1.02x + 0.46) and wall thickness (r = 0.93; SEE = 1.4 mm; y = 0.95x + 1.64) compared with anatomic measurements. Left ventricular mass by a simulated Penn convention revealed a lower correlation and larger error compared with three-dimensional measurements (r = 0.72; SEE = 42.8 gm; y = 1.01x + 9.61). Therefore determination of left ventricular mass by three-dimensional reconstruction was validated in vitro and was superior to one-dimensional echocardiographic methods.

Echocardiographic Assessment of Right Ventricular Volume and Function

Echocardiographic evaluation of right ventricular volume and function has become a subject of growing interest with the increasing awareness of the important role of the right ventricle in the entire circulation. However, the anatomically complex and load-dependent shaped right ventricle shape is difficult to describe by a simple geometric figure and its volume and function are, therefore, difficult to assess in a simple manner. A number of echocardiographic methods for evaluating right ventricular volume and function have emerged; to date, however, their quantification remains a clinical challenge. The major goal is to develop a reproducible method that will allow for quantitative comparisons between patients or serially within a given patient. This discussion examines the available methods with specific attention to their reliability and limitations. Visual inspection or measurement of single plane indices is limited by their lack of standardization and failure to describe the entire right ventricle. Simpson's rule requires computer calculations and assumes an elliptic symmetry present in the left, but not the right ventricle. Application of the area-length method to the subcostal outflow tract and apical four-chamber views is a particularly practical current approach. Three-dimensional echo reconstruction, which eliminates the need for geometric assumptions and individual standardized views, although only in its infancy, promises to be the most accurate method for right ventricular volume calculation and in the future should emerge as the standard for research and many clinical applications.

Transthoracic three-dimensional echocardiographic reconstruction of left and right ventricles: in vitro validation and comparison with magnetic resonance imaging

Two-dimensional (2D) echocardiographic and angiographic measurements of ventricular volumes are limited by geometric assumptions concerning cavity shape. We compared in vitro the accuracy of a three-dimensional (3D) echocardiographic system suitable for transthoracic imaging to magnetic resonance imaging (MRI) in the measurement of left and right ventricular volumes. Ventricular cast volumes from 14 excised formalin-fixed sheep hearts filled with an agarose solution were compared with data derived from 3D echocardiography and MRI. Left and right ventricular volumes from 3D echocardiographic reconstructions agreed well with actual volumes without significant underestimation or overestimation. MRI progressively underestimated left ventricular volumes as these increased and systematically underestimated right ventricular volumes. Our echocardiographic system designed for 3D transthoracic imaging combines excellent measurements of left and right ventricular volumes and the computed reconstruction of tomographic slices with the full spatial resolution of the original 2D images. Thus in this in vitro model, 3D echocardiography exhibited greater accuracy than MRI.

Feasibility of a two-dimensional echocardiographic method for the clinical assessment of right ventricular volume and function in children

The relative ease of acquisition and safety of two-dimensional echocardiography has established it as the mainstay for routine cardiac imaging. Translation of imaging data into useful quantitative information, however, requires fitting the ventricle to a specific geometric model. Because of its complex shape and anterior position, many attempts at right ventricular quantitation by two-dimensional echocardiography have been criticized as impractical and not reproducible. A simple method incorporating subcostal and apical imaging was introduced in 1984. This approach appeared to combine accuracy and practicability but was never validated in a clinical setting because of the difficulties of subcostal imaging in adults. This study assessed the feasibility and accuracy of this technique in the pediatric population. Results of volume comparison to values derived by magnetic resonance imaging were r = 0.96, standard error of the estimate (SEE) = 19.3 ml, and mean difference = 15 +/- 19.4 ml and r = 0.97, SEE = 12.3 ml, and bias = 5 +/- 11.8 ml for diastolic and systolic volumes, respectively. Comparison of estimates of ejection fraction with magnetic resonance imaging demonstrated r = 0.90, SEE = 5.9%, and bias = 3% +/- 5.7%. Interobserver and intraobserver variability was 9.9% and 8.2%, respectively, for systolic volumes and 11.5% and 8.9%, respectively, for diastolic volumes. Evaluation of right ventricular size and function by this approach is comparable to determinations by magnetic resonance imaging and may be clinically useful in the management of pediatric patients.

A systematic approach to echocardiographic image acquisition and three-dimensional reconstruction with a subxiphoid rotational scan

Rotational scanning from the subxiphoid position is an image acquisition technique used for reconstruction of dynamic three-dimensional echocardiographic images in infants and small children. The orientation of the heart within the three-dimensional data set is variable and dependent on the image plane at which rotational scanning was initiated. We describe an image acquisition technique that standardizes the orientation of the heart within the three-dimensional data set, thereby permitting a systematic approach to the reconstruction of three-dimensional renderings. Thirteen infants and small children with congenital heart disease were studied by this approach. Illustrative examples are provided. The average time required to derive a three-dimensional rendering was 37 +/- 9 minutes. We conclude that subxiphoid rotational scanning by a systematic approach to image acquisition and reconstruction can be applied successfully to the derivation of three-dimensional renderings of congenital cardiac defects.

Automatic border detection and three-dimensional reconstruction with echocardiography

This article reviews two important innovations in echocardiography resulting from the recent advances in the capabilities of microprocessors. The first, automatic endocardial border detection, has been implemented on computers contained entirely within echocardiograph machines and is gaining wide clinical use. The second, three-dimensional imaging, is currently under intense investigation and shows great promise for clinical application. It requires, however, further development of the specialized transducer apparatus necessary for image acquisition and the sophisticated computer-processing capability necessary for image reconstruction and display.

Three-dimensional echocardiography: the influence of number of component images on accuracy of left ventricular volume quantitation

One approach to three-dimensional echocardiography is to reconstruct the surface of cardiac structures from two-dimensional images positioned in three-dimensional space. This approach has yielded accurate measures; however, the relationship between the number of nonparallel images used in three-dimensional echocardiographic reconstruction to the accuracy of the volume calculated has not been determined. With a canine model in which instantaneous left ventricular volume could be measured in vivo, images were obtained from intersecting long- and short-axis scans and stored with their spatial coordinates. The left ventricle was reconstructed and its volume calculated. The difference between three-dimensional echocardiographic and true volume was determined in 84 different cavitary volumes (4 to 85 ml). In each case, long- and short-axis images were deleted serially from the original data set (maximum of 27) until there were only three images left in the reconstruction. After each set of deletions, left ventricular volume was recalculated with the remaining images. Three-dimensional echocardiography accurately quantified ventricular volume with eight to 12 intersecting images, with a mean error of less than 1 ml and an SD of 5 ml. With a reduction of component images below eight, there were progressive increases in both absolute and mean percentage error. Accurate assessment of stroke volume and ejection fraction in this beating heart model also required eight to 12 images. Left ventricular volume and systolic function can be quantitated by three-dimensional echocardiography with as few as eight to 12 intersecting or nonparallel images.

Quantitative three-dimensional reconstruction of left ventricular volume with complete borders detected by acoustic quantification underestimates volume

Recently a new acoustic-quantification (AQ) technique has been developed to provide on-line automated border detection with an integrated backscatter analysis. Prior studies have largely correlated AQ areas with volumes without direct comparison of volumes for agreement. By using complete AQ-detected borders as the input to a validated method for three-dimensional echocardiographic (3DE) reconstruction, we can compare an entire cavity volume measured with the aid of AQ against a directly measured volume. This would also explore the possibility of applying AQ to 3DE reconstruction to reduce tracing time and enhance routine applicability. To compare reconstructed volumes with actual values in a stable standard allowing direct volume measurement, the left ventricles of 13 excised animal hearts were studied with a 3DE system that automatically combines two-dimensional (2D) images and their locations. Intersecting 2D views were obtained with conventional scanning and AQ imaging, with gains optimized to permit 3D reconstruction by detecting the most continuous AQ borders for each view, with maximal cavity size. Reconstruction was performed with manually traced central endocardial reflections and AQ-detected borders visually reproduced the left ventricular shapes; the AQ reconstructions, however, were consistently smaller. The reconstructed left ventricular (LV) volumes correlated well with actual values by both manual and AQ techniques (r = 0.93 and 0.88, with standard errors of 2.3 cc and 2.0 cc, p = not significant [NS]). Agreement with actual values was relatively close for the manually traced borders (y = 0.93x + 0.68, mean difference = -0.8 +/-2.2 cc). AQ-derived reconstructions consistently underestimated LV volume by 39 +/- 10% (y = 0.62x-0.09, mean difference = -7.8 +/- 3.0 cc, different from manually traced and actual volumes by analysis of variance [ANOVA], F = 69, p<0.00001). The AQ-detected threshold signal was displaced into the cavity, and volume between walls and false tendons was excluded, leading to underestimation, which increased with increasing cavity volume (r = 0.76). The AQ technique can therefore be applied to 3DE reconstruction, providing volumes that correlate well with directly measured values in a stable in vitro standard, minimizing observer decisions regarding manual border placement after image acquisition. However, when the complete borders needed for 3D reconstruction are used, absolute volumes are underestimated with current algorithms that integrate backscatter and displace the detected threshold into the ventricular cavity.

Ultrasonic three-dimensional reconstruction of the heart

The recent advances in ultrasound equipment, digital image acquisition, and display techniques made three-dimensional (3D) echocardiography a clinically feasible and exciting technique which allows objective analysis of structure and pathological conditions of complex geometry. In this report, different image acquisition techniques are described and compared. In our experience, with rotational scanning the acquisition of cross-sections for 3D reconstruction becomes an integral part of a routine diagnostic study, both with a multiplane transesophageal imaging transducer, and in precordial echocardiography. After digital reformatting and image processing, a volumetric data set is obtained, which allows the display of synthetic cross-sections in various orientations independent from the point of origin of the sector scan [anyplane two-dimensional (2D) imaging]. This also offers the possibility of volume quantification, without the assumption of theoretical geometrical model of the cavity. Finally, dynamic volume rendered display can be applied for the objective display of the anatomy and the complex relationship among the different structures.

Three-dimensional echocardiography: in vivo validation for right ventricular free wall mass as an index of hypertrophy

OBJECTIVES

This study tested the ability of three-dimensional echocardiography to reconstruct the right ventricular free wall and determine its mass in vivo using a system that automatically combines two-dimensional images with their spatial locations.

BACKGROUND

Right ventricular free wall thickness is limited as an index of right ventricular hypertrophy because right ventricular mass may increase by dilation without increased thickness and because trabeculations and oblique views can exaggerate thickness in individual M-mode and two-dimensional scans. Three-dimensional echocardiography may have potential advantages because it can integrate the entire free wall mass, uninfluenced by oblique views or geometric assumptions.

METHODS

The three-dimensional system was applied to 12 beating canine hearts to reconstruct the right ventricular free wall in intersecting views. The corresponding mass was compared with actual weights of the excised right ventricular free wall (15.5 to 78 g). For comparison, right ventricular sinus and outflow tract thickness were also measured by two-dimensional echocardiography, and the ability to predict mass from these values was determined.

RESULTS

The three-dimensional algorithm successfully reproduced right ventricular free wall mass, which agreed well with actual values: y = 1.04x + 0.02, r = 0.985, SEE = 2.7 g (5.7% of the mean value). The two-dimensional predictions showed increased scatter: The variance of mass estimation, based on thickness, was 9.5 to 12.5 (average 11) times higher than the three-dimensional method (p < 0.02).

CONCLUSIONS

Despite the irregular crescentic shape of the right ventricle, its free wall mass can be accurately measured by three-dimensional echocardiography in vivo, providing closer agreement with actual mass than predictions based on wall thickness. This method, with the increased efficiency of the three-dimensional system, can potentially improve our ability to evaluate the presence and progression of right ventricular hypertrophy.

Three-dimensional reconstruction of ventricular septal defects: validation studies and in vivo feasibility

OBJECTIVES

The purpose of this study was to demonstrate the feasibility of in vivo three-dimensional reconstruction of ventricular septal defects and to validate its quantitative accuracy for defect localization in excised hearts (used to permit comparison of three-dimensional and direct measurements without cardiac contraction).

BACKGROUND

Appreciating the three-dimensional spatial relations of ventricular septal defects could be useful in planning surgical and catheter approaches. Currently, however, echocardiography provides only two-dimensional views, requiring mental integration. A recently developed system automatically combines two-dimensional echocardiographic images with their spatial locations to produce a three-dimensional construct.

METHODS

Surgically created ventricular septal defects of varying size and location were imaged and reconstructed, along with the left and right ventricles, in the beating heart of six dogs to demonstrate the in vivo feasibility of producing a coherent image of the defect that portrays its relation to surrounding structures. Two additional gel-filled excised hearts with defects were completely reconstructed. Quantitative localization of the defects relative to other structures (ventricular apexes and valve insertions) was then validated for seven defects in excised hearts. The right septal margins of the exposed defects were also traced and compared with their reconstructed areas and circumferences.

RESULTS

The three-dimensional images provided coherent images and correct spatial appreciation of the defects (two inlet, two trabecular, one outlet and one membranous Gerbode in vivo; one inlet and one apical in excised hearts). The distances between defects and other structures in the excised hearts agreed well with direct measures (y = 1.05x-0.18, r = 0.98, SEE = 0.30 cm), as did reconstructed areas (y = 1.0x-0.23, r = 0.98, SEE = 0.21 cm2) and circumferences (y = 0.97x + 0.13, r = 0.97, SEE = 0.3 cm).

CONCLUSIONS

Three-dimensional reconstruction of ventricular septal defects can be achieved in the beating heart and provides an accurate appreciation of defect size and location that could be of value in planning interventions.