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

Right Ventricular Volumes, Ejection Fraction, and Systolic Function Indices in Normal Neonates by Three-Dimensional Speckle-Tracking Echocardiography

The aim of this study was to test the feasibility of measuring right ventricular (RV) volumes, ejection fraction (EF), and systolic function indices in neonates using three-dimensional speckle-tracking echocardiography (3D-STE). Thirty-eight neonates underwent complete echocardiographic evaluation, including the acquisition of three full-volume 3D datasets or more from each of the apical, parasternal, and subcostal windows while naturally sleeping. Datasets were analyzed using a commercially available software (Tomtec). Global RV 3D volumes and EF were measured. In addition, 2D free wall longitudinal strain (LS), tricuspid valve annulus (TVA), tricuspid annular plane systolic excursion (TAPSE) and its index to RV length (TAPSEi), and fractional area change (FAC) were obtained from a non-shortened apical 4-chamber view of the RV, derived from the 3D dataset. Three or more datasets obtained from the apical window were available for analysis for each subject. At least one dataset was adequate for analysis in all subjects. Mean indexed 3D diastolic, systolic, stroke volumes, and EF were measured at 28.5 ± 3.4 ml/m², 13 ± 2.0 ml/m², 15.6 ± 1.9 ml/m², and 54.6 ± 3.2%, respectively. Free wall 2D LS was calculated at (- 27.9 ± 2.5%). In addition, mean TVA measured 11.1 ± 0.8 mm, TAPSE measured 6.8 ± 0.9 mm, and TAPSEi and FAC were calculated at 24.2 ± 2.1 and 46 ± 3.4%, respectively. 3D-STE is feasible in normal neonates without the need for sedation. Reference values of RV 3D volumes and 2D indices of systolic function were obtained. These data could be helpful in patients where the size or systolic function of the RV is in question. Larger studies are required to establish nomograms for the above indices in this age group.

Tricuspid annular plane systolic excursion is correlated with poor outcome in surgery for rheumatic heart valvular disease

BACKGROUND

Right ventricular (RV) function is a major determinant of clinical outcome, but its function indices have not been studied well in surgery for rheumatic valvular heart disease. The aim of this study was to determine the correlation of tricuspid annular plane systolic excursion (TAPSE) with outcome of rheumatic heart valve surgery.

METHODS

A prospective comparative study was conducted including 100 eligible patients who were divided into two groups based on RV function as assessed by TAPSE measured by two-dimensional (2D) echocardiography preoperatively. Those with TAPSE less than 15 mm were included in group 1 and those with TAPSE of 15 or more were included in group 2.

RESULTS

50 patients were included in group 1 and 50 patients in group 2. Mean age of the patients was 56.78 ± 15.21 years in group 1 and 54.46 ± 15.03 years in group 2 (P = 0.444). 34 (34%) patients underwent aortic valve replacement (AVR), 35 (35%) underwent both aortic and mitral valves replacement, and 31 (31%) ones had mitral valve replacement (MVR). A significant difference was found between the duration of ventilation (5.15 ± 2.80 hours in group 1 vs. 3.72 ± 2.71 hours in group 2, P = 0.001), postoperative inotropic requirement [more than 24 hours in 18 (36%) patients in group 1 vs. 7 (14%) patients in group 2, P = 0.003], total intensive care unit (ICU) stay (8.92 ± 3.62 days in group 1 vs. 5.20 ± 2.06 days in group 2, P = 0.001), and mortality [7 (14%) in group 1 vs. 2 (4%) in group 2, P = 0.038].

CONCLUSION

TAPSE less than 15 mm in patients undergoing surgical correction for rheumatic valvular heart disease leads to poor outcomes. These patients need special attention perioperatively.

A closer look at right ventricular 3D volume quantification by transthoracic echocardiography and cardiac MRI

AIM

To compare right ventricular (RV) volumetry using state-of-the-art three-dimensional (3D) transthoracic echocardiography (3DE) and cardiac magnetic resonance imaging (CMR) near-simultaneously in a clinical setting.

MATERIALS AND METHODS

Forty-seven consecutive patients received comprehensive echocardiography including 3DE within 30 minutes of CMR. RV volumetry was performed offline with semi-automated 3D endocardial border tracing as well as manual delineation of the compacted myocardium in short-axis views by CMR.

RESULTS

Forty-two examinations (89%) could be analysed offline by 3D RV reconstruction. Mean RV volumes assessed by CMR and 3DE were 215±63 and 127±42 ml for end-diastole (RV-EDV), as well as 110±43 and 62±27 ml for end-systole (RV-ESV). RV-EDV, RV-ESV, and RV stroke volume measured by 3DE were significantly lower than RV volumetry by CMR. Mean bias were -88, -48, and -41 ml, respectively. Mean RV ejection fraction (-EF) showed a non-significant deviation of +2% between 3DE and CMR and the correlation coefficient was r=0.58 for RV-EF.

CONCLUSION

RV-EF can be assessed reliably using transthoracic 3DE in patients with good image quality; however, absolute RV volumes measured by 3DE show a systematic deviation to CMR volumetry that has been previously neglected and requires careful interpretation regarding anatomical cardiac imaging.

A mathematical model of human heart including the effects of heart contractility varying with heart rate changes

Incorporating the intrinsic variability of heart contractility varying with heart rate into the mathematical model of human heart would be useful for addressing the dynamical behaviors of human cardiovascular system, but models with such features were rarely reported. This study focused on the development and evaluation of a mathematical model of the whole heart, including the effects of heart contractility varying with heart rate changes. This model was developed based on a paradigm and model presented by Ottesen and Densielsen, which was used to model ventricular contraction. A piece-wise function together with expressions for time-related parameters were constructed for modeling atrial contraction. Atrial and ventricular parts of the whole heart model were evaluated by comparing with models from literature, and then the whole heart model were assessed through coupling with a simple model of the systemic circulation system and the pulmonary circulation system. The results indicated that both atrial and ventricular parts of the whole heart model could reasonably reflect their contractility varying with heart rate changes, and the whole heart model could exhibit major features of human heart. Results of the parameters variation studies revealed the correlations between the parameters in the whole heart model and performances (including the maximum pressure and the stroke volume) of every chamber. These results would be useful for helping users to adjust parameters in special applications.

Validity of the surface electrocardiogram criteria for right ventricular hypertrophy: the MESA-RV Study (Multi-Ethnic Study of Atherosclerosis-Right Ventricle)

OBJECTIVES

The study aimed to assess the diagnostic properties of electrocardiographic (ECG) criteria for right ventricular hypertrophy (RVH) measured by cardiac magnetic resonance imaging (cMRI) in adults without clinical cardiovascular disease.

BACKGROUND

Current ECG criteria for RVH were based on cadaveric dissection in small studies.

METHODS

MESA (Multi-Ethnic Study of Atherosclerosis) performed cMRIs with complete right ventricle (RV) interpretation on 4,062 participants without clinical cardiovascular disease. Endocardial margins of the RV were manually contoured on diastolic and systolic images. The ECG screening criteria for RVH from the 2009 American Heart Association Recommendations for Standardization and Interpretation of the ECG were examined in participants with and without left ventricular (LV) hypertrophy or reduced ejection fraction. RVH was defined using sex-specific normative equations based on age, height, and weight.

RESULTS

The study sample with normal LV morphology and function (n = 3,719) was age 61.3 ± 10.0 years, 53.5% female, 39.6% Caucasian, 25.5% African American, 21.9% Hispanic, and 13.0% Asian. The mean body mass index was 27.9 ± 5.0 kg/m(2). A total of 6% had RVH, which was generally mild. Traditional ECG criteria were specific (many >95%) but had low sensitivity for RVH by cMRI. The positive predictive values were not sufficiently high as to be clinically useful (maximum 12%). The results did not differ based on age, sex, race, or smoking status, or with the inclusion of participants with abnormal LV mass or function. Classification and regression tree analysis revealed that no combination of ECG variables was better than the criteria used singly.

CONCLUSIONS

The recommended ECG screening criteria for RVH are not sufficiently sensitive or specific for screening for mild RVH in adults without clinical cardiovascular disease.

Review of novel clinical applications of advanced, real-time, 3-dimensional echocardiography

Advances in computer processing speed and memory along with the advent of the microbeam former that can sample an entire crystal of the ultrasound transducer made possible the performance of 3-dimensional echocardiography in real time (RT3DE). The miniaturization of a 3-dimensional transducer permitting its extension to transesophageal mode rapidly expanded its use in a variety of conditions. Recent development of user-friendly automated/semiautomated cropping and display software may make it rather simple, even for the novice to gather useful information from RT3DE. We discuss the background, technique, and cutting-edge research and novel clinical applications of advanced RT3DE, including left ventricular dyssynchrony assessment, 3-D speckle tracking, myocardial contrast echocardiography, complete 4-dimensional (4-D) shape and motion analysis of the left ventricle, 4-D volumetric analysis of the right ventricle, 3-D volume rendering of the mitral valve, and other percutaneous and surgical procedural applications.

Variables influencing the accuracy of 2-dimensional and real-time 3-dimensional echocardiography for assessment of small volumes, areas, and distances: an in vitro study using static tissue-mimicking phantoms

OBJECTIVES

The aim of this study was to assess the validity, accuracy, and reproducibility of real-time 3-dimensional (3D) echocardiography for small distances, areas, and volumes.

METHODS

Real-time 3D echocardiography using matrix technology was performed in small calibrated tissue-mimicking phantoms and compared with 2-dimensional (2D) echocardiography. In a systematic variation of variables on data acquisition and analysis including different 3D workstations (manual disk summation versus semiautomatic border detection), the relative contributions of sources of errors were determined. The clinical relevance of the in vitro findings was assessed in 5 neonates and infants.

RESULTS

Distance calculation was valid (mean relative error ± SD, -0.15% ± 1.2%). Underestimation of areas and volumes was significant for both 2D and 3D echocardiography (area: 2D, -7.0% ± 2.9%; 3D, -6.0% ± 2.8%; volume: 2D, -13.1% ± 4.5%; 3D, -6.7% ± 2.5%; P < .05). Adjustment of compression and gain on data acquisition (difference of the means: 2D, 11.6%; 3D, 17.9%), gain on postprocessing (3D, 3.4%), and the border detection algorithm on analysis (2D, 4.8%; 3D, 16.6%) had a highly significant effect on volume and area calculations (P < .001). In vivo, compression and gain on acquisition (3D, 19.1%) and the 3D workstation on analysis (3D, 22.2%) had a highly significant impact on left ventricular volumetry (P < .001).

CONCLUSIONS

Real-time 3D echocardiography is a reliable method for calculation of small distances, areas, and volumes comparable with the size of the neonatal and infant heart. Variables influencing boundary identification during image acquisition and analysis have a significant impact on 2D and 3D area and volume calculations. Standardized protocols are mandatory to avoid these sources of error in both clinical practice and research.

Right ventricular dysfunction and failure in chronic pressure overload

Right ventricular (RV) dysfunction is the main cause of death in pulmonary arterial hypertension (PAH). Our understanding of the pathophysiology of RV dysfunction is limited but improving. Methods to better diagnose RV dysfunction earlier and treatments specifically designed to minimize or reverse the remodeling process are likely to improve outcomes. We review the current understanding of RV dysfunction in chronic pressure overload and introduce some novel insights based on recent investigations into pathophysiology, diagnosis, and treatment.

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.

Rapid and accurate quantification of right ventricular volume and stroke volume by real-time 3-dimensional triplane echocardiography

BACKGROUND

Previous studies have demonstrated that 3-Dimensional (3-D) echocardiography can determine right ventricular (RV) volume accurately. However, this technique has not been feasible in everyday clinical practice because of the necessity of time-consuming off-line processes.

HYPOTHESIS

A newly developed real-time 3-D triplane echocardiography, which acquires 3 apical rotational cross-sectional images simultaneously, holds the promise to resolve these problems.

METHODS AND RESULTS

Sixteen excised formalin fixed porcine hearts and 24 healthy human subjects underwent real-time 3-D triplane echocardiography. In an anatomic in vitro study, the actual volume of RV was obtained by spilling water in the RV cavity into a graduated cylinder for measurement, which served as a reference standard for comparison. For healthy subjects, the RV stroke volume (SV) was measured by triplane echocardiography which was compared with the left ventricular (LV) SV obtained by conventional 2-Dimensional echocardiography (2-DE). Excellent correlation and agreement between 3-D triplane imaging derived RV volume and the actual one for excised porcine hearts were observed (r = 0.979, p < 0.001, mean difference 2.2 mL). In healthy human subjects, good correlation and agreement between 3-D triplane imaging derived RV SV and LV SV measured by 2-DE were obtained (r = 0.970, p < 0.001, mean difference 5.9 mL).

CONCLUSIONS

Real-time 3-D triplane echocardiography provides us a new method for rapid and accurate quantification of RV volume. Furthermore, this new method holds the promise for evaluating RV volume and SV in routine clinical practice.

Feasibility of a new generation three-dimensional echocardiography for right ventricular volumetric and functional measurements

Right ventricular (RV) dimensions and function are of diagnostic and prognostic importance in cardiac disease. Because of the peculiar morphology of the right ventricle, 2-dimensional echocardiography has several limitations in RV evaluation. Recently, new 3-dimensional transthoracic echocardiographic software adapted for RV morphology was introduced. The aims of this study were to evaluate the feasibility of 3-dimensional RV analysis in a large population and to compare and correlate 3-dimensional RV data with classic 2-dimensional and Doppler parameters, including tricuspid annular plane systolic excursion and peak systolic velocity on Doppler tissue imaging, RV fractional shortening area, RV stroke volume (by the Doppler method), and pulmonary arterial systolic pressure. Two hundred subjects were studied: 48 normal controls and 152 patients with valvular heart disease (104 patients), idiopathic dilated cardiomyopathy (20 patients), or pulmonary hypertension (28 patients). The mean times for 3-dimensional acquisition and 3-dimensional reconstruction were 3 +/- 1 and 4 +/- 2 minutes, respectively. Imaging quality was good in most cases (85%). The mean RV diastolic and systolic volumes were 103 +/- 38 and 46 +/- 28 ml, respectively. The RV ejection fraction (RVEF) was correlated negatively with pulmonary arterial systolic pressure and positively with tricuspid annular plane systolic excursion, peak systolic velocity, and fractional shortening area. The pathologic group was characterized by larger RV volumes and lower RVEFs. Three-dimensional echocardiography clearly showed that in the pathologic group, patients with pulmonary hypertension had the largest RV volumes and the lowest RVEFs and that those with idiopathic dilated cardiomyopathy were characterized by RVEFs lower than those of patients with valvular disease. In conclusion, this new quantitative 3-dimensional method to assess RV volumes and function is feasible, relatively simple, and not time consuming. Data obtained with 3-dimensional analysis are well correlated with those obtained by 2-dimensional and Doppler methods and can differentiate normal and pathologic subjects.

Comparison of Novel Echocardiographic Parameters of Right Ventricular Function with Ejection Fraction by Cardiac Magnetic Resonance

BACKGROUND

Assessment of right ventricular (RV) function by echocardiography is challenging. Newer techniques such as tissue Doppler echocardiography and strain echocardiography may allow accurate and quantitative assessment of RV function. We sought to determine which echocardiographic variable or variables best correlated with RV ejection fraction (RVEF) by cardiac magnetic resonance.

METHODS

We performed conventional echocardiography, tissue Doppler echocardiography, strain echocardiography, and cardiac magnetic resonance on 53 individuals, of which 10 patients had arrhythmogenic RV dysplasia without pulmonary hypertension, and 43 were control subjects. RV fractional area change (FAC), Tei index, isovolumic acceleration, peak systolic velocity (S'), tissue displacement, systolic strain (Ss) rate, and Ss were measured.

RESULTS

RVEF, FAC, S', tissue displacement, isovolumic acceleration, Ss rate, and Ss were significantly lower in patients compared with control subjects (P < or = .05 in all) but not the Tei index (P = .07). Regression analysis revealed a significant correlation between S', tissue displacement, Ss rate, Ss, and FAC with RVEF (P < .05 for all) but not with isovolumic acceleration and Tei index (P = .13 and .39, respectively). Multivariate analysis demonstrated a persistent significant relationship between S' and FAC with RVEF (both P < .05). However, feasibility, and intraobserver and interobserver agreement, were substantially lower for FAC. A cut-off value of 8.8 cm/s for S' had sensitivity and specificity of 80% and 79% (area under the curve 0.87, P = .01), respectively, for prediction of RVEF less than 45%.

CONCLUSION

Tissue Doppler echocardiographically derived S' best correlates with cardiac magnetic resonance-derived RVEF with high reproducibility and may facilitate simple and quantitative assessment of RV function.

Pregnancy: Maternal and Fetal Heart Disease

Cardiac disorders complicate less than 1% of all pregnancies. Physiologic changes in pregnancy may mimic heart disease. In order to differentiate these adaptations from pathologic conditions, an in-depth knowledge of cardiovascular physiology is mandatory. A comprehensive history, physical examination, electrocardiogram, chest radiograph, and echocardiogram are sufficient in most cases to confirm the diagnosis. Care of women with cardiac disease begins with preconception counseling. Severe lesions should be taken care of prior to contemplating pregnancy. Management principles for pregnant women are similar to those for the non-pregnant state. A team approach comprised of a maternal fetal medicine specialist, cardiologist, neonatologist, and anesthesiologist is essential to assure optimal outcome for both the mother and the fetus. Although fetal heart disease complicates only a small percentage of pregnancies, congenital heart disease causes more neonatal morbidity and mortality than any other congenital malformation. Unfortunately, screening approaches for fetal heart disease continue to miss a large percentage of cases. This weakness in fetal screening has important clinical implications, because the prenatal detection and diagnosis of congenital heart disease may improve the outcome for many of these fetal patients. In fact, simply the detection of major heart disease prenatally can improve neonatal outcome by avoiding discharge to home of neonates with ductal-dependent congenital heart disease. Fortunately, recent advances in screening techniques, an increased ability to change the prenatal natural history of many forms of fetal heart disease, and an increasing recognition of the importance of a multidisciplinary, team approach to the management of pregnancies complicated with fetal heart disease, together promise to improve the outcome of the fetus with congenital heart disease.

Reproducibility of Right Ventricular Volumes and Ejection Fraction Using Real-time Three-Dimensional Echocardiography

OBJECTIVES

The nongeometric nature of the right ventricle (RV) makes it difficult to measure. We sought to determine whether real-time three-dimensional echocardiography (RT3DE) is superior to two-dimensional echocardiography (2DE) for the follow-up of RV function by validation vs cardiac MRI.

METHODS

RV volumes and ejection fraction (EF) were studied with 2DE (including area-length [A-L], the modified two-dimensional subtraction [2DS] method, and the Simpson method of discs), RT3DE, and MRI in 50 patients with left ventricular wall motion abnormalities, the results of which suggested possible RV infarction. Test-retest variation was performed by a complete restudy using a separate sonographer within 24 h without the alteration of hemodynamics or therapy. Interobserver and intraobserver variations were noted in a subgroup of 20 patients.

RESULTS

EF estimations were similar using each technique. The mean (+/- SD) MRI end-diastolic volume (87 +/- 22 mL) was only slightly underestimated by RT3DE (mean difference, -3 +/- 10; p < 0.05), with a greater mean difference for 2DE A-L (-29 +/- 10; p < 0.05), and the Simpson method of discs (-29 +/- 23; p < 0.05), and was greatly overestimated by 2DS (mean difference, 26 +/- 23; p < 0.05). Similarly, the mean MRI end-systolic volume (46 +/- 17 mL) was only slightly underestimated by RT3DE (-4 +/- 7; p < 0.05), compared with 2DE A-L (-16 +/- 8; p < 0.05) and the Simpson method of discs (-16 +/- 8; p < 0.05), and was overestimated by 2DS (14 +/- 13; p < 0.05). RT3DE findings had a higher correlation with each parameter than any 2DE technique. There was also good intraobserver and interobserver correlation between RT3DE by two sonographers. RT3DE had less test-retest variation of RV volumes and EF than any 2DE measure.

CONCLUSIONS

RT3DE is more accurate than two-dimensional approaches and reduces the test-retest variation of RV volumes and EF measurements in follow-up RV assessment.

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.

Variables Influencing the Accuracy of Right Ventricular Volume Assessment by Real-time 3-Dimensional Echocardiography: An In Vitro Validation Study

BACKGROUND

Preliminary experience with matrix-array real-time (RT) 3-dimensional echocardiography (3DE) in pediatric patients has demonstrated consistently lower right ventricular volume (RVV) compared with magnetic resonance imaging. Our hypothesis was that variables in RT 3DE acquisition and offline analysis, including gain settings, thickness, and orientation of disks, could alter RVV measurements.

METHODS

Displacements of water from latex models derived from excised lamb hearts were used for comparison. RT 3DE volume acquisitions were performed using a matrix-array probe (2-4 MHz); RVVs were calculated offline using summation of disks method.

RESULTS

No significant difference and excellent agreement was found for comparison of RT 3DE with displacement of water using 5-mm cut planes, optimal gain settings, and short-axis tracings. Different gain settings and long-axis tracings significantly affected RVV. A slice thickness of 13 mm or greater affected volume measurements.

CONCLUSIONS

RT 3DE can accurately measure RVV. Specific variables will alter volumes measurements and must be considered in clinical studies.

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.

Real-time three-dimensional echocardiography: technological gadget or clinical tool?

The complex anatomy of cardiac structures requires three-dimensional spatial orientation of images for a better understanding of structure and function, thereby improving image interpretation. Real-time three-dimensional echocardiography is a recently developed technique based on the design of an ultrasound transducer with a matrix array that rapidly acquires image data in a pyramidal volume. The simultaneous display of multiple tomographic images allows three-dimensional perspective and the anatomically correct examination of any structure within the volumetric image. As a consequence, it is less operator-dependent and hence more reproducible. Dedicated software systems and technologies are based on high-performance computers designed for graphic handling of three-dimensional images by providing possibilities beyond those obtainable with echocardiography. This methodology allows simultaneous display of multiple superimposed planes in an interactive manner as well as a quantitative assessment of cardiac volumes and ventricular mass in a three-dimensional format without a pre-established assumption of cardiac chamber geometry. In addition, myocardial contraction and/or perfusion abnormalities are clearly identified. Finally, real-time three-dimensional colour Doppler flow mapping enables complete visualisation of the regurgitant jet and new ways of assessing regurgitant lesion severity. Thus, this technique expands the abilities of non-invasive cardiology and may open new doors for the evaluation of cardiac diseases. In this article, current and future clinical applications of real-time three-dimensional echocardiography are reviewed.

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.

In Vitro Validation of Right Ventricular Volume and Mass Measurement by Real-Time Three-Dimensional Echocardiography

OBJECTIVE

To evaluate initially the feasibility and accuracy of real-time three-dimensional echocardiography (RT-3DE) for quantifying right ventricular (RV) volume and wall mass in an in vitro experimental study.

METHODS

In ten excised porcine hearts, measurements of RV volume and free wall mass with RT-3DE were outlined and calculated by 2-, 4-, 8- and 16-plane methods with Tom Tec 4D Cardio-View RT 1.0. The results were compared with those of 2D length method and 2D biplane Simpson method. The values of RV silicone latex cast and free wall mass measured by water displacement were served as reference values.

RESULTS

RV shapes of excised porcine hearts with RT-3DE were similar to those of the actual anatomic RVs and RV silicone latex casts. From the findings of analysis of variance and Student-Newman-Keuls test, there was no significant difference between measurements of RV volume with RT-3DE 16-plane (mean 64.05 ml), 8-plane (61.83 ml) and the reference values of RV silicone latex casts (62.94 ml). No significant difference was found between measurements of RV free wall mass with 16-plane (72.81 g), 8-plane (71.05 g) and the reference values of RV free wall masses (76.21 g). However, there was significant difference between measurements of RV volume and free wall mass with 2-plane, 2D biplane Simpson method and the reference values. Furthermore, the measurements of RV volume and free wall mass with 16-plane and 8-plane were better correlated with the reference values than those with 4-plane and 2D length method.

CONCLUSIONS

RT-3DE will be a valuable technique for quantifying irregular crescentic RV volume and wall mass.

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.

Real-time 3-Dimensional Doppler Echocardiography for the Assessment of Stroke Volume: An In Vivo Human Study Compared with Standard 2-Dimensional Echocardiography

BACKGROUND

Invasive monitors and noninvasive 2-dimensional echocardiography are the standard clinical methods for stroke volume (SV) and cardiac output computation. We studied the use of real-time color Doppler 3-dimensional (3D) echocardiography (3DE) for the assessment of SV in human beings.

METHODS

In all, 55 pediatric and adult patients with good transthoracic windows and a normal aortic valve were studied. Real-time 3DE color Doppler volumes incorporating the left ventricular outflow tract and aortic valve were taken. SV was calculated from the color Doppler data in the 3DE DICOM dataset. This was compared with 2-dimensional echocardiography SV calculation from the pulsed wave velocity through the aortic valve along with the left ventricular outflow tract diameter.

RESULTS

Five patients were excluded because of mismatching of the 3D color Doppler segments in the 3D volume. The 3D Doppler volumes from the remaining 50 patients were analyzed. There was good correlation between the patients' averaged 3DE SV calculations and the 2-dimensional echocardiography pulsed wave SV estimation (y = 0.84x + 7.8, r2 = 0.90).

CONCLUSION

Real-time 3D Doppler echocardiography can be used to accurately calculate SV and cardiac output, compared with conventional pulsed Doppler measurement, in pediatric and adult patients from transthoracic imaging.

Three-Dimensional Echocardiography: Rational Mode of Component Images for Left Ventricular Volume Quantitation

Three-dimensional echocardiography (3DE) improves the accuracy of left ventricle (LV) volumetry compared with the two-dimensional echocardiography (2DE) approach because geometric assumptions in the algorithms may be eliminated. The relationship between accuracy of mode (short- versus long-axis planimetry) and the number of component images versus time required for analysis remains to be determined. Sixteen latex models simulating heterogeneously distorted (aneurysmatic) human LVs (56-303 ml; mean 182+/-82 ml) were scanned from an 'apical' position (simultaneous 2DE and 3DE). For 3DE volumetry, the slice thickness was varied for the short (C-scan) and long axes (B-scan) in 5-mm steps between 1 and 25 mm. The mean differences (true-echocardiographic volumes) were 16.5+/-44.3 ml in the 2DE approach (95% confidence intervals -27.8 to +60.8) and 0.6+/-4.0 ml (short axis; 95% confidence intervals -3.4 to +4.6) as well as 2.1+/-9.9 ml (long axis; 95% confidence intervals -7.8 to +12.0) in the 3DE approach (in both cases, the slice thickness was 1 mm). Above a slice thickness of 15 mm, the 95% confidence intervals increased steeply; in the short versus long axes, these were -6.5 to +8.5 versus -7.0 to +10.6 at 15 mm and -10.1 to +15.7 versus -11.3 to +10.9 at 20 mm. The intra-observer variance differed significantly (p<0.001) only above 15 mm (short axis). Time required for analysis derived by measuring short-axis slice thicknesses of 1, 15, and 25 mm was 58+/-16, 7+/-2 and 3+/-1 min, respectively. The most rational component image analysis for 3DE volumetry in the in vitro model uses short-axis slices with a thickness of 15 mm.

The use of live three-dimensional Doppler echocardiography in the measurement of cardiac output

OBJECTIVES

The purpose of this study was to investigate whether cardiac output (CO) could be accurately computed from live three-dimensional (3-D) Doppler echocardiographic data in an acute open-chested animal preparation.

BACKGROUND

The accurate measurement of CO is important in both patient management and research. Current methods use invasive pulmonary artery catheters or two-dimensional (2-D) echocardiography or esophageal aortic Doppler measures, with the inherent risks and inaccuracies of these techniques.

METHODS

Seventeen juvenile, open-chested pigs were studied before undergoing a separate cardiopulmonary bypass procedure. Live 3-D Doppler echocardiography images of the left ventricular outflow tract and aortic valve were obtained by epicardial scanning, using a Philips Medical Systems (Andover, Massachusetts) Sonos 7500 Live 3-D Echo system with a 2.5-MHz probe. Simultaneous CO measurements were obtained from an ultrasonic flow probe placed around the aortic root. Subsequent offline processing using custom software computed the CO from the digital 3-D Doppler DICOM data, and this was compared to the gold standard of the aortic flow probe measurements.

RESULTS

One hundred forty-three individual CO measurements were taken from 16 pigs, one being excluded because of severe aortic regurgitation. There was good correlation between the 3-D Doppler and flow probe methods of CO measurement (y = 1.1x - 9.82, R(2) = 0.93).

CONCLUSIONS

In this acute animal preparation, live 3-D Doppler echocardiographic data allowed for accurate assessment of CO as compared to the ultrasonic flow probe measurement.

Evaluation of right ventricular volume and systolic function by realtime three-dimensional echocardiography

The optimal plane for measurement of the right ventricular (RV) volumes by real-time three-dimensional echocardiography (RT3DE) was determined and the feasibility and accuracy of RT3DE in studying RV systolic function was assessed. RV "Full volume" images were acquired by RT3DE in 22 healthy subjects. RV end-diastolic volumes (RVEDV) and end-systolic volumes (RVESV) were outlined using apical biplane, 4-plane, 8-plane, 16-plane offline separately. RVSV and RVEF were calculated. Meanwhile tricuspid annual systolic excursion (TASE) was measured by M-mode echo. LVSV was outlined by 2-D echo according to the biplane Simpson's rule. The results showed: (1) There was a good correlation between RVSV measured from series planes and LVSV from 2-D echo (r = 0.73; r = 0.69; r = 0.63; r = 0.66, P < O. 25-0. 0025); (2) There were significant differences between RVEDV in biplane and those in 4-, 8-, 16-plane (P < 0.001). There was also difference between RV volume in 4-plane and that in 8-plane (P < 0.05), but there was no significant difference between RV volume in 8-plane and that in 16-plane (P > 0.05); (3) Inter-observers and intro-observers variability analysis showed that there were close agreements and relations for RV volumes (r = 0.986, P < 0.001; r = 0.93, P < 0.001); (4) There was a significantly positive correlation of TASE to RVSV and RVEF from RT3DE (r = 0.83; r = 0.90). So RV volume measures with RT3DE are rapid, accurate and reproducible. In view of RV's complex shape, apical 8-plane method is better in clinical use. It may allow early detection of RV systolic function.

Real-Time Three-Dimensional Echocardiography Using a Novel Matrix Array Transducer

Three-dimensional echocardiography has multiple advantages over two-dimensional echocardiography, such as accurate left ventricular quantification and improved spatial relationships. However, clinical use of three-dimensional echocardiography has been impeded by tedious and time-consuming methods for data acquisition and post-processing. A newly developed matrix array probe, which allows real-time three-dimensional imaging with instantaneous on-line volume-rendered reconstruction, direct manipulation of thresholding, and cut planes on the ultrasound unit may overcome the aforementioned limitations. This report will review current methods of three-dimensional data acquisition, emphasizing the real-time methods and clinical applications of the new matrix array probe.