Analysis of global systolic and diastolic left ventricular performance using volume-time curves by real-time three-dimensional echocardiography

Beneficial cardiovascular effects of bariatric surgical and dietary weight loss in obesity

OBJECTIVES

We hypothesized that, in obese persons without comorbidities, cardiovascular responses to excess weight are reversible during weight loss by either bariatric surgery or diet.

BACKGROUND

Obesity is associated with cardiac hypertrophy, diastolic dysfunction, and increased aortic stiffness, which are independent predictors of cardiovascular risk.

METHODS

Thirty-seven obese (body mass index 40 +/- 8 kg/m(2)) and 20 normal-weight subjects (body mass index 21 +/- 2 kg/m(2)) without identifiable cardiac risk factors underwent cardiac magnetic resonance imaging for the assessment of the left and right ventricles and of indexes of aortic function. Thirty of the obese subjects underwent repeat imaging after 1 year of significant weight loss, achieved in 17 subjects by diet and in 13 subjects by bariatric surgery. Seven obese subjects underwent repeat imaging after 1 year of continued obesity.

RESULTS

Left and right ventricular masses were significantly increased, left ventricular diastolic function impaired, and aortic distensibility reduced in the obese. Both diet and bariatric surgery led to comparable, significant decreases in left and right ventricular masses, end-diastolic volume, and diastolic dysfunction, and an increase in aortic distensibility at all levels of the aorta, most pronounced distally (e.g., distal descending aorta 5.1 +/- 1.8 mm Hg(-1) x 10(-3) before weight loss and 6.8 +/- 2.5 mm Hg(-1) x 10(-3) after weight loss; p < 0.001). No improvements were observed in continued obesity.

CONCLUSIONS

Irrespective of method, 1 year of weight loss leads to partial regression of cardiac hypertrophy and to reversal of both diastolic dysfunction and aortic distensibility impairment. These findings provide a potential mechanism for the reduction in mortality seen with weight loss.

A dual propagation contours technique for semi-automated assessment of systolic and diastolic cardiac function by CMR

BACKGROUND

Although cardiovascular magnetic resonance (CMR) is frequently performed to measure accurate LV volumes and ejection fractions, LV volume-time curves (VTC) derived ejection and filling rates are not routinely calculated due to lack of robust LV segmentation techniques. VTC derived peak filling rates can be used to accurately assess LV diastolic function, an important clinical parameter. We developed a novel geometry-independent dual-contour propagation technique, making use of LV endocardial contours manually drawn at end systole and end diastole, to compute VTC and measured LV ejection and filling rates in hypertensive patients and normal volunteers.

METHODS

39 normal volunteers and 49 hypertensive patients underwent CMR. LV contours were manually drawn on all time frames in 18 normal volunteers. The dual-contour propagation algorithm was used to propagate contours throughout the cardiac cycle. The results were compared to those obtained with single-contour propagation (using either end-diastolic or end-systolic contours) and commercially available software. We then used the dual-contour propagation technique to measure peak ejection rate (PER) and peak early diastolic and late diastolic filling rates (ePFR and aPFR) in all normal volunteers and hypertensive patients.

RESULTS

Compared to single-contour propagation methods and the commercial method, VTC by dual-contour propagation showed significantly better agreement with manually-derived VTC. Ejection and filling rates by dual-contour propagation agreed with manual (dual-contour - manual PER: -0.12 +/- 0.08; ePFR: -0.07 +/- 0.07; aPFR: 0.06 +/- 0.03 EDV/s, all P = NS). However, the time for the manual method was approximately 4 hours per study versus approximately 7 minutes for dual-contour propagation. LV systolic function measured by LVEF and PER did not differ between normal volunteers and hypertensive patients. However, ePFR was lower in hypertensive patients vs. normal volunteers, while aPFR was higher, indicative of altered diastolic filling rates in hypertensive patients.

CONCLUSION

Dual-propagated contours can accurately measure both systolic and diastolic volumetric indices that can be applied in a routine clinical CMR environment. With dual-contour propagation, the user interaction that is routinely performed to measure LVEF is leveraged to obtain additional clinically relevant parameters.

Real-time three-dimensional echocardiography provides advanced haemodynamic information associated with intra-dialytic hypotension in patients with autonomic dysfunction

BACKGROUND

Real-time three-dimensional echocardiography (RT3DE) has emerged as a more accurate and effective tool for assessing left ventricular (LV) function, compared to traditional two-dimensional (2D) methods. In this study, we used this new tool to revise the controversial relationship between LV function and intra-dialytic hypotension.

METHODS

This study enrolled 29 intra-dialytic hypotensive patients (the IDH group) and 34 controls (the CON group) on regular maintenance haemodialysis. The RT3DE- and 2D-derived ejection fraction (EF), stroke volume index (SVI) and ratio of early transmitral inflow velocity to diastolic early tissue velocity were assessed at pre-dialysis and mid-dialysis. The intravascular volume was assessed by the inferior vena cava collapsibility index.

RESULTS

Pre-dialysis evaluation showed no difference in RT3DE- and 2D-derived parameters between the two groups. At mid-dialysis, the IDH group had a lower 2D EF (54 +/- 9.1 versus 62 +/- 6.8% in the CON group, P < 0.001), RT3DE EF (53 +/- 6 versus 60 +/- 7% in the CON group, P < 0.001) and SVI (24.3 +/- 8 versus 30.6 +/- 12.2 mL in the CON group, P = 0.02). From pre-dialysis to mid-dialysis, the IDH group had greater decrease in the change in 2D EF (-4.8% +/- 12.6% versus 5% +/- 13.7% in the CON group, P = 0.004), RT3DE EF (-11.8 +/- 10.3 versus -3.4 +/- 11.5% in the CON group, P = 0.003) and SVI (-17.3 +/- 18.5 versus -9.2 +/- 19.8% in the CON group, P = 0.004). The calculated cardiac index change also showed a greater decrease in the IDH group (-17.8 +/- 20.2 versus -5.7 +/- 18.5% in the CON group, P = 0.02). No significant difference in the ratio of early transmitral inflow velocity to diastolic early tissue velocity, heart rate, systemic vascular resistance index or inferior vena cava collapsibility index was found between the two groups at the baseline or mid-dialysis. A lack of an increase in heart rate and the systemic vascular resistance index in the IDH group during the hypotensive episodes implies that these patients have autonomic dysfunction. Multivariate analysis showed that the RT3DE EF change of < -9.5% (odds ratio = 6, P = 0.003) and the presence of diabetes (odds ratio = 4.4, P = 0.013) had significant and independent associations with intra-dialytic hypotension.

CONCLUSIONS

By adopting RT3DE to assess LV performance, our data demonstrated that an inadequate compensation in the LV systolic function is the main mechanism mediating the occurrence of intra-dialytic hypotension in patients with autonomic dysfunction.

Real-time 3-dimensional echocardiographic quantification of left ventricular volumes: multicenter study for validation with magnetic resonance imaging and investigation of sources of error

OBJECTIVES

We sought to study: 1) the accuracy and reproducibility of real-time 3-dimensional echocardiographic (RT3DE) analysis of left ventricular (LV) volumes in a multicenter setting, 2) interinstitutional differences in relationship with the investigators' specific experience, and 3) potential sources of volume underestimation.

BACKGROUND

Reproducibility and accuracy of RT3DE evaluation of LV volumes has not been validated in multicenter studies, and LV volumes have been reported to be underestimated compared to cardiac magnetic resonance (CMR) standard.

METHODS

A total of 92 patients with a wide range of ejection fractions underwent CMR and RT3DE imaging at 4 different institutions. Images were analyzed to obtain LV end-systolic volume (ESV) and end-diastolic volume (EDV). Reproducibility was assessed using repeated analyses. The investigation of potential sources of error included: phantom imaging, intermodality analysis-related differences, and differences in LV boundary identification, such as inclusion of endocardial trabeculae and mitral valve plane in the LV volume.

RESULTS

The RT3DE-derived LV volumes correlated highly with CMR values (EDV: r = 0.91; ESV: r = 0.93), but were 26% and 29% lower consistently across institutions, with the magnitude of the bias being inversely related to the level of experience. The RT3DE measurements were less reproducible (4% to 13%) than CMR measurements (4% to 7%). Minimal changes in endocardial surface position (1 mm) resulted in significant differences in measured volumes (11%). Exclusion of trabeculae and mitral valve plane from the CMR reference eliminated the intermodality bias.

CONCLUSIONS

The RT3DE-derived LV volumes are underestimated in most patients because RT3DE imaging cannot differentiate between the myocardium and trabeculae. To minimize this difference, tracing the endocardium to include trabeculae in the LV cavity is recommended. With the understanding of these intermodality differences, RT3DE quantification of LV volume is a reliable tool that provides clinically useful information.

Real-time three-dimensional echocardiographic assessment of left ventricular remodeling index in patients with hypertensive heart disease and coronary artery disease

Left ventricular remodeling index (LVRI) was assessed in patients with hypertensive heart disease (HHD) and coronary artery disease (CAD) by real-time three-dimensional echocardiography (RT3DE). RT3DE data of 18 patients with HHD, 20 patients with CAD and 22 normal controls (NC) were acquired. Left ventricular end-diastolic volume (EDV) and left ventricular end-diastolic epicardial volume (EDVepi ) were detected by RT3DE and two-dimensional echocardiography Simpson biplane method (2DE). LVRI (left ventricular mass /EDV) was calculated and compared. The results showed that LVRI measurements detected by RT3DE and 2DE showed significant differences inter-groups (P<0.01). There was no significant difference in NC group (P>0.05), but significant difference in HHD and CAD intra-group (P<0.05). There was good positive correlations between LVRI detected by RT3DE and 2DE in NC and HHD groups (r=0.69, P<0.01; r=0.68, P<0.01), but no significant correlation in CAD group (r=0.30, P>0.05). It was concluded that LVRI derived from RT3DE as a new index for evaluating left ventricular remodeling can provide more superiority to LVRI derived from 2DE.

Quantification of regional volume and systolic function of the left ventricle by real-time three-dimensional echocardiography

Real-time three-dimensional (3D) echocardiography (RT-3DE) provides a unique technique to evaluate left ventricular regional function in a 3D format. We aimed to explore whether the left ventricular segmental volume and systolic function is uniform and to establish normal values of volume and systolic function parameters of 16 regions in healthy subjects. RT-3DE was performed in 41 normal subjects and four-dimensional (4D)-left ventricle (LV) analysis software and a TomTec workstation were used to analyze data for regional end-diastolic volume (EDV(R)), regional end-systolic volume (ESV(R)), regional stroke volume (SV(R)), regional ejection fraction (EF(R)), ratio of SV(R) to global SV (SV(R/G)) and ratio of SV(R) to global EDV (EF(R/G)). All regional volume and systolic function parameters were not uniform among the left ventricular walls. They all increased in the order of inferior, posterior, lateral, septal, anterior and antero-septal walls with an increasing trend from the apical, middle to basal segments. The systolic function (EF(R), SV(R/G) and EF(R/G)) of the anterior and antero-septal walls was significantly higher than that of the lateral, inferior and posterior walls. And the intra- and interobserver variability for EDV(R), ESV(R), SV(R/G) and EF(R/G) ranged from 2.9% to 5.8%. In conclusion, the regional volume and systolic function of the left ventricle is not uniform and, therefore, a normal left ventricle cannot be regarded as a symmetric model for assessing the regional systolic function. This information may improve the accuracy of RT-3DE techniques in the assessment of the left ventricular regional function. (E-mail: zhangyun@sdu.edu.cn and yaogh@yahoo.com).

Dual-source CT with improved temporal resolution in assessment of left ventricular function: a pilot study

OBJECTIVE

Functional analysis using MDCT has been limited by insufficient temporal resolution. The aim of this study was to assess the performance of a dual-source CT system with improved temporal resolution in the determination of both volume- or time-dependent functional parameters and regional wall motion in comparison with cine MRI.

SUBJECTS AND METHODS

Twenty patients (15 of whom had previous myocardial infarction) were prospectively examined using dual-source CT. MRI was used as the standard of reference. Using the Simpson's method, ventricular volumes were determined for the whole of the cardiac cycle and results compared using Parson's correlation and Bland-Altman analysis. Regional wall motion was assessed on cine images and compared using weighted kappa statistics.

RESULTS

Dual-source CT revealed a strong correlation with cine MRI regarding the quantification of end-diastolic volume (r = 0.98), end-systolic volume (r = 0.99), stroke volume (r = 0.96), and ejection fraction (r = 0.95). Good correlation was obtained for peak ejection rate (r = 0.79) and peak filling rate (r = 0.84), whereas agreement proved only moderate for time-to-peak ejection rate (r = 0.68) or time-to-peak filling rate from end-systole (r = 0.64). The mean difference for ejection fraction was negligible (bias, 0.72%). Good agreement between both techniques was likewise found for regional wall motion (kappa = 0.88).

CONCLUSION

With the improvement of temporal resolution between 42 and 83 milliseconds, dual-source CT not only enables accurate assessment of global functional parameters, but it also allows for quantification of time-dependent variables and reliable evaluation of regional wall motion.

Diastolic ventricular aspiration: a mechanism supporting the rapid filling phase of the human ventricles

During the rapid filling phase of the heart cycle, the internal volumes of the two ventricular cavities approximately double, while the intraventricular pressures rise typically only by an amount of less than 1 kPa. Such a small pressure increase cannot be the sole driving mechanism for the large inflow of blood associated with ventricular expansion during this period. Instead, the rapid filling phase is to be interpreted as being mediated primarily by the heart recoiling elastically from its contracted state, causing blood to be aspirated rapidly into the ventricles. In order to study the role of this mechanism, elastic finite element (FE) simulations of ventricular expansion were performed, taking into account the large deformations occurring during this period and the effective compressibility of the myocardium due to intramural fluid flow. Thereby, a realistic three-dimensional geometry derived from magnetic resonance imaging (MRI) measurements of both human ventricles was used. To validate our FE analyses, the results were compared with published measurements relating to the rapid filling phase of the human left ventricle. Our study shows that, under normal physiological conditions, ventricular aspiration plays a key role in the ventricular filling process.

Preliminary clinical study of real-time three-dimensional echocardiographic volume-time curve in evaluating left ventricular diastolic function

The volume-time curve change in patients with normal left ventricular (LV) diastolic function and diastolic dysfunction was evaluated by real-time three-dimensional echocardiography (RT3DE). LV diastolic dysfunction was defined by E'<A' in pulse-wave tissue Doppler for inter-ventricular septal (IVS) of mitral annulus. In 24 patients with LV diastolic dysfunction, including 12 patients with delayed relaxation (delayed relaxation group) and 12 patients with pseudo-normal function (pseudo-normal group) and 24 normal volunteers (control group), data of full-volume image were acquired by real-time three-dimensional echocardiography and subjected to volume-time curve analysis. EDV (end-diastolic volume), ESV (end-systolic volume), LVEF (left ventricular ejection fraction), PER (peak ejection rate), PFR (peak filling rate) from RT3DE were examined in the three groups. Compared to the control group, PFR (diastolic filling index of RT3DE) was significantly reduced in the delayed relaxation group and pseudo-normal group (P<0.05). There were no significant differences in EDV, ESV, LVEF, PER (P>0.05). It is concluded that PFR, as a diastolic filling index of RT3DE, can reflect the early diastolic function and serve as a new non-invasive, quick and accurate tool for clinical assessment of LV diastolic function.

Quantification of left ventricular volumes and function in patients with cardiomyopathies by real-time three-dimensional echocardiography: a head-to-head comparison between two different semiautomated endocardial border detection algorithms

OBJECTIVE

We evaluated two different commercially available real-time 3-dimensional echocardiographic semiautomated border detection algorithms for left ventricular (LV) volume analysis in patients with cardiomyopathy and distorted LV geometry.

METHODS

A total of 53 patients in sinus rhythm with various types of cardiomyopathy (mean age 56 +/- 11 years, 28 men) and adequate 2-dimensional image quality were included. The real-time 3-dimensional echocardiographic multiplane interpolation (MI) and full volume reconstruction (FVR) methods were used for LV volume analysis. Magnetic resonance imaging was used as the reference method.

RESULTS

A strong correlation (R(2) > 0.95) was found for all LV volume and ejection fraction measurements by either real-time 3-dimensional echocardiographic method. Analysis time was shorter with the FVR method (6 +/- 2 vs 15 +/- 4 minutes, P < .01) as compared with the MI method. Bland-Altman analysis showed greater underestimation of end-diastolic and end-systolic volumes by MI compared with FVR. For the MI method a bias of -24.0 mL (-15.0% of the mean) for end-diastolic volume and -11.3 mL (-18.0% of the mean) for end-systolic volume was found. For FVR analysis these values were -9.9 mL (-6.0% of the mean) and -5.0 mL (-9.0% of the mean), respectively. Ejection fraction was similar for the MI and FVR method with a mean difference compared with magnetic resonance imaging of 0.6 (1.0%) and 0.8 (1.3%), respectively.

CONCLUSION

In patients with cardiomyopathy, distorted LV geometry, and good 2-dimensional image quality, the FVR method is faster and more accurate than the MI method in assessment of LV volumes.

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.

Real-time three-dimensional echocardiography: a pilot feasibility study in an Italian cardiologic center

BACKGROUND

The majority of studies demonstrating the diagnostic potential of three-dimensional (3-D) echocardiography have been conducted on selected series of patients in research laboratories.

AIM

To investigate the feasibility and usefulness of real-time 3-D transthoracic echocardiography in daily routine practice.

METHODS

Two hundred consecutive patients underwent standard two-dimensional (2-D) transthoracic echocardiography (TTE) and real-time (RT) 3-D TTE with a commercially available ultrasound system (Sonos 7500 LIVE 3D, Philips Medical Systems). The quality of 3-D acquisitions and post-processed images was graded as: bad, satisfactory, good and demo. In each case, the results of 3-D TTE were compared with 2-D images to disclose additional qualitative information provided by 3-D examination. An additional qualitative information score was given for each cardiac structure.

RESULTS

The mean time of the 3-D examination was 11+/-4 min. The mean time of 2-D transthoracic studies in our laboratory is 25 min and the total time in this series was therefore approximately 36 min. The mean number of acquisitions in our series was 11.5 per patient. The quality was evaluated as bad/insufficient in 7.0%, satisfactory/sufficient in 29.6%, good in 40.2% and demo in 23.2% of all datasets and reconstructions. The structures with greater additional qualitative information scores comprise the anterior and posterior mitralic leaflets, antero-lateral and postero-medial papillary muscles and leaflets of tricuspid valve. The intra- and interobserver reproducibility of quality grading was good and there are few interobserver discrepancies, which were resolved by two physicians, experienced in 3-D echocardiography, not involved in the study.

CONCLUSIONS

RT 3-D TTE may be used in clinical settings with high feasibility rate and may provide additional, clinically quite relevant qualitative information. This technique may expand the abilities of non-invasive cardiology and open new doors for the evaluation of cardiac disease.

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.

Assessment of left ventricular asynchrony using volume-time curves of 16 segments by real-time 3 dimensional echocardiography: Comparison with tissue Doppler imaging

BACKGROUND

Recent technical developments with high-resolution real-time 3 dimensional echocardiography (RT3DE) facilitate the acquisition of high quality images and the analysis of segmental volume-time curves (VTCs).

AIMS

To assess left ventricular (LV) asynchrony using the VTCs of 16 segments by RT3DE, and to evaluate accuracy compared to tissue Doppler imaging (TDI).

METHODS

Twenty-three heart failure (HF) patients (LVEF: 25+/-6%, age: 60+/-13 years) and 16 normal controls underwent TDI and RT3DE. The standard deviation (SD3) of the end systolic time reaching minimal systolic volume for the 16 segments on VTCs was obtained by RT3DE. The standard deviation (SD2) of the electromechanical coupling time for the 8 segments was measured using TDI.

RESULTS

SD3 was markedly higher in HF patients than in controls (7.7+/-2.5 vs 1.5+/-1.0%, P<0.01) and increased as LVEF decreased (r=-0.85, P<0.01). SD2 was also significantly higher in HF patients (27.0+/-8.6 vs 12.6+/-5.0 ms, P<0.01) and had a good negative correlation with LVEF (r=-0.72, P<0.01). SD3 was well correlated to SD2 (r=0.66, P<0.01).

CONCLUSIONS

We suggest that analysis of VTCs in 16 segments using RT3DE may be a useful alternative to TDI for the evaluation of LV asynchrony.

Evaluation of left ventricular function with cardiac magnetic resonance imaging using Fourier fitting

The aims of this study were to investigate the applicability of Fourier fitting in the magnetic resonance (MR) evaluation of left ventricular (LV) function and to determine the optimal number of harmonics for fitting. Cine cardiac MR imaging was performed in 10 subjects, and an LV time-volume curve was generated. Fourier fitting was applied to the original curve using 1-10 harmonics, and the qualities of the time-volume curve and first-derivative curve were evaluated. LV functional parameters were calculated from curves generated with and without fitting. The quality of the original time-volume curve was good, and Fourier fitting had no substantial effect on functional parameters obtained directly from the time-volume curve such as ejection fraction. The first-derivative curve generated without fitting showed substantial artificial fluctuation. The application of Fourier fitting depressed the fluctuation and tended to decrease estimates of peak ejection rate and peak filling rate. Five or six harmonics appeared to be appropriate for obtaining a high-quality first-derivative curve. In conclusion, Fourier fitting was indicated to aid in reducing the artificial fluctuation of the first-derivative curve generated from cine cardiac MR imaging and to contribute to the evaluation of functional parameters derived from the first-derivative curve.

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.

Live 3D Echocardiography: A Replacement for Traditional 2D Echocardiography?

OBJECTIVE

We describe the development of real-time 3D imaging and review the previously used versions of 3D echocardiography so that the reader will appreciate why current developments truly do represent a quantum leap in the technology.

CONCLUSION

Three-dimensional echocardiography has now been shown to have several advantages over 2D echocardiography, particularly for volume measurements, visualization of septal defects, and whole-valve evaluation. Given these data, it is clear that 3D echocardiography is here to stay and soon will become part of routine echocardiographic examinations.

Volumetric analysis of regional left ventricular function with real-time three-dimensional echocardiography: validation by magnetic resonance and clinical utility testing

BACKGROUND

Quantitative information on regional left ventricular volumes from real-time three-dimensional echocardiographic (RT3DE) images has significant clinical potential but needs validation.

AIM

To validate these measurements against cardiac magnetic resonance (CMR) and test the feasibility of automated detection of regional wall motion (RWM) abnormalities from RT3DE data.

METHODS

RT3DE (Philips) and CMR (Siemens) images were obtained from 31 patients and analysed by using prototype software to semiautomatically calculate indices of regional left ventricular function, which were compared between RT3DE and CMR (linear regression, Bland-Altman). Additionally, CMR images were reviewed by an expert, whose RWM grades were used as a reference for automated classification of segments as normal or abnormal from RT3DE and from CMR images. For each modality, normal regional ejection fraction (REF) values were obtained from 15 patients with normal wall motion. In the remaining 16 patients, REFs were compared with thresholds that were derived from patients with normal wall motion and optimised using receiver operating characteristic analysis.

RESULTS

RT3DE measurements resulted in good agreement with CMR. Regional indices calculated in patients with normal wall motion varied between segments, but overall were similar between modalities. In patients with abnormal wall motion, RWM was graded as abnormal in 74% segments. CMR and RT3DE thresholds were similar (16-segment average 55 (10)% and 56 (7)%, respectively). Automated interpretation resulted in good agreement with expert interpretation, similar for CMR and RT3DE (sensitivity 0.85, 0.84; specificity 0.81, 0.78; accuracy 0.84, 0.84, respectively).

CONCLUSION

Analysis of RT3DE data provides accurate quantification of regional left ventricular function and allows semiautomated detection of RWM abnormalities, which is as accurate as the same algorithm applied to CMR images.

Quantitative assessment of left ventricular size and function: side-by-side comparison of real-time three-dimensional echocardiography and computed tomography with magnetic resonance reference

BACKGROUND

Cardiac CT (CCT) and real-time 3D echocardiography (RT3DE) are being used increasingly in clinical cardiology. CCT offers superb spatial and contrast resolution, resulting in excellent endocardial definition. RT3DE has the advantages of low cost, portability, and live 3D imaging without offline reconstruction. We sought to compare both CCT and RT3DE measurements of left ventricular size and function with the standard reference technique, cardiac MR (CMR).

METHODS AND RESULTS

In 31 patients, RT3DE data sets (Philips 7500) and long-axis CMR (Siemens, 1.5 T) and CCT (Toshiba, 16-slice MDCT) images were obtained on the same day without beta-blockers. All images were analyzed to obtain end-systolic and end-diastolic volumes and ejection fractions using the same rotational analysis to eliminate possible analysis-related differences. Intertechnique agreement was tested through linear regression and Bland-Altman analyses. Repeated measurements were performed to determine intraobserver and interobserver variability. Both CCT and RT3DE measurements resulted in high correlation (r2 > 0.85) compared with CMR. However, CCT significantly overestimated end-diastolic and end-systolic volumes (26 and 19 mL; P < 0.05), resulting in a small but significant bias in ejection fraction (-2.8%). RT3DE underestimated end-diastolic and end-systolic volumes only slightly (5 and 6 mL), with no significant bias in EF (0.3%; P = 0.68). The limits of agreement with CMR were comparable for the 2 techniques. The variability in the CCT measurements was roughly half of that in either RT3DE or CMR values.

CONCLUSIONS

CCT provides highly reproducible measurements of left ventricular volumes, which are significantly larger than CMR values. RT3DE measurements compared more favorably with the CMR reference, albeit with higher variability.

Quantification of Regional Left Ventricular Wall Motion from Real-time 3-Dimensional Echocardiography in Patients with Poor Acoustic Windows: Effects of Contrast Enhancement Tested Against Cardiac Magnetic Resonance

OBJECTIVE

Regional left ventricular function can be assessed by real-time 3-dimensional echocardiography (RT3DE) in patients with good image quality. Our goals were to: (1) test the feasibility of RT3DE quantification of regional wall motion (RWM) in patients with poor acoustic windows who require contrast for endocardial visualization; and (2) validate these measurements against cardiac magnetic resonance (CMR) reference.

METHODS

RT3DE datasets and CMR images were obtained in 24 patients. In 16 of 24 patients with suboptimal endocardial definition, RT3DE imaging was repeated with intravenous contrast and triggering at end systole and end diastole. RT3DE datasets were analyzed using custom software designed to semiautomatically detect and segment the endocardial surface and calculate RWM values. CMR images were analyzed using commercial software to obtain reference values for RWM.

RESULTS

In 8 of 24 patients with good endocardial definition, RT3DE values of RWM correlated well with CMR (r = 0.73) with a small bias (-1.0 mm). In the remaining 16 patients, analysis of nonenhanced RT3DE datasets yielded lower correlation with CMR (r = 0.61) and a slightly greater bias (-1.5 mm). The agreement with CMR improved significantly (r = 0.76, bias -1.1 mm) with contrast enhancement.

CONCLUSIONS

The agreement between RT3DE and CMR values of RWM is directly related to RT3DE image quality. In patients with poor acoustic windows, dual-triggered contrast enhancement improves the accuracy of RWM quantification to a level similar to that noted in patients with good images without contrast.

Volumetric Quantification of Global and Regional Left Ventricular Function From Real-Time Three-Dimensional Echocardiographic Images

Background— Real-time 3D echocardiographic (RT3DE) data sets contain dynamic volumetric information on cardiac function. However, quantification of left ventricular (LV) function from 3D echocardiographic data is performed on cut-planes extracted from the 3D data sets and thus does not fully exploit the volumetric information. Accordingly, we developed a volumetric analysis technique aimed at quantification of global and regional LV function.

Methods and Results— RT3DE images obtained in 30 patients (Philips 7500) were analyzed by use of custom software based on the level-set approach for semiautomated detection of LV endocardial surface throughout the cardiac cycle, from which global and regional LV volume (LVV)–time and wall motion (WM)–time curves were obtained. The study design included 3 protocols. In protocol 1, time curves obtained in 16 patients were compared point-by-point with MRI data (linear regression and Bland-Altman analyses). Global LVV correlated highly with MRI ( r =0.98; y =0.99 x +2.3) with minimal bias (1.4 mL) and narrow limits of agreement (±20 mL). WM correlated highly only in basal and midventricular segments ( r =0.88; y =0.85 x +0.7). In protocol 2, we tested the ability of this technique to differentiate populations with known differences in LV function by studying 9 patients with dilated cardiomyopathy and 9 normal subjects. All calculated indices of global and regional systolic and diastolic LV function were significantly different between the groups. In protocol 3, we tested the feasibility of automated detection of regional WM abnormalities in 11 patients. In each segment, abnormality was detected when regional shortening fraction was below a threshold obtained in normal subjects. The automated detection agreed with expert interpretation of 2D WM in 86% of segments.

Conclusions— Volumetric analysis of RT3DE data is clinically feasible and allows fast, semiautomated, dynamic measurement of LVV and automated detection of regional WM abnormalities.

A finite element study relating to the rapid filling phase of the human ventricles

During the rapid diastolic filling phase at rest, the ventricles of the human heart double approximately in volume. In order to investigate whether the ventricular filling pressures measured under physiological conditions can give rise to such an extensive augmentation in ventricular volumes, a finite element model of the human right and left ventricles has been developed, taking into account the nonlinear mechanical behavior and effective compressibility of the myocardial tissue. The results were compared with the filling phase of the human left ventricle as extrapolated from measurements documented in the literature. We arrived at the conclusion that the ventricular pressures measured during the rapid filling phase cannot be the sole cause of the rise of the observed ventricular volumes. We rather advocate the assumption that further dilating mechanisms might be part of ventricular activity thus heralding a multiple function of the ventricular muscle body. A further result indicates that under normal conditions the influence of the viscoelasticity of the tissue should not be disregarded in ventricular mechanics.

Guiding and optimization of resynchronization therapy with dynamic three-dimensional echocardiography and segmental volume-time curves: a feasibility study

OBJECTIVE

To assess a new approach for guiding and hemodynamic optimization of resynchronization therapy, using three-dimensional (3D) transthoracic echocardiography.

BACKGROUND

Resynchronization therapy for heart failure provides the greatest hemodynamic benefit when applied to the most delayed left ventricular (LV) site. Currently, the ideal LV pacing site is selected according to acute invasive hemodynamic assessment and/or tissue Doppler imaging.

METHODS

A total of 16 patients with advanced heart failure and an implanted biventricular pacemaker were included in this study. Transthoracic apical LV images at equidistant intervals were obtained using a prototype, fast-rotating second harmonic transducer to reconstruct 3D LV datasets during sinus rhythm (SR), right ventricular (RV) apical and biventricular pacing mode. A semi-automated contour analysis system (4D LV analysis, TomTec, Germany) was used for segmental wall motion analysis and identification of the most delayed contracting segment and calculation of global LV function.

RESULTS

Data acquisition duration was 10 s and analyzable 3D images were obtained in 12 patients. Of these patients, data during SR were available in 9 and during biventricular pacing in 11. The greatest contraction delay during SR was found in the anterior and antero-septal segments in five of nine patients. Biventricular pacing resulted in reduction of the contraction delay in seven of eight patients. The global LV function did not change significantly.

CONCLUSION

3D echocardiography with appropriate analytic software allows detection of the most delayed LV contracting segment and can be used to select the optimal pacing site during resynchronization therapy.

High-resolution transthoracic real-time three-dimensional echocardiography: quantitation of cardiac volumes and function using semi-automatic border detection and comparison with cardiac magnetic resonance imaging

OBJECTIVES

We sought to validate high-resolution transthoracic real-time (RT) three-dimensional echocardiography (3DE), in combination with a novel semi-automatic contour detection algorithm, for the assessment of left ventricular (LV) volumes and function in patients.

BACKGROUND

Quantitative RT-3DE has been limited by impaired image quality and time-consuming manual data analysis.

METHODS

Twenty-four subjects with abnormal (n = 14) or normal (n = 10) LVs were investigated. The results for end-diastolic volume (EDV), end-systolic volume (ESV), and ejection fraction (EF) obtained by manual tracing were compared with the results determined by the semi-automatic border detection algorithm. Moreover, the results of the semi-automatic method were compared with volumes and EF obtained by cardiac magnetic resonance imaging (CMRI).

RESULTS

Excellent correlation coefficients (r = 0.98 to 0.99) and low variability (EDV -1.3 +/- 8.6 ml; ESV -0.2 +/- 5.4 ml; EF -0.1 +/- 2.7%; p = NS) were observed between the semi-automatically and manually assessed data. The RT-3DE data correlated highly with CMRI (r = 0.98). However, LV volumes were underestimated by RT-3DE compared with CMRI (EDV -13.6 +/- 18.9 ml, p = 0.002; ESV -12.8 +/- 20.5 ml, p = 0.005). The difference for EF was not significant between the two methods (EF 0.9 +/- 4.4%, p = NS). Observer variability was acceptable, and repeatability of the method was excellent.

CONCLUSIONS

The RT-3DE, in combination with a semi-automatic contour tracing algorithm, allows accurate determination of cardiac volumes and function compared with both manual tracing and CMRI. High repeatability suggests applicability of the method for the serial follow-up of patients with cardiac disease.

Live Three-Dimensional Echocardiography: Imaging Principles and Clinical Application

Live three-dimensional echocardiography (L3DE) is an important breakthrough in the field of medical ultrasound. It will provide a great potential tool for clinical diagnosis and treatment. In this article, the authors first review the bottlenecks in 3D cardiac imaging and the technical principles of L3DE that have been used to overcome some of these problems. We then discuss the scanning methods, clinical usefulness, and the future of L3DE, drawing on our experiences in examining 124 human patients and in conducting animal verification studies with a live 3D ultrasound system.

Assessment of left ventricular function by three-dimensional echocardiography

Accurate determination of LV volume, ejection fraction and segmental wall motion abnormalities is important for clinical decision-making and follow-up assessment. Currently, echocardiography is the most common used method to obtain this information. Three-dimensional echocardiography has shown to be an accurate and reproducible method for LV quantitation, mainly by avoiding the use of geometric assumptions. In this review, we describe various methods to acquire a 3D-dataset for LV volume and wall motion analysis, including their advantages and limitations. We provide an overview of studies comparing LV volume and function measurement by various gated and real-time methods of acquisition compared to magnetic resonance imaging. New technical improvements, such as automated endocardial border detection and contrast enhancement, will make accurate on-line assessment with little operator interaction possible in the near future.