Three-dimensional echocardiography using a transoesophageal imaging probe. Potentials and technical considerations

A comparison of echocardiographic modalities to guide structural heart disease interventions

Percutaneous techniques to treat structural heart disease are rapidly evolving based on innovative interventions and the considerable advancement in image guidance technology. While two-dimensional transthoracic and transesophageal echocardiography have been integral to procedural planning and execution, intracardiac and three-dimensional echocardiography supply unique visualization of target structures with a potential improvement in patient safety and procedural efficacy. The choice of image guidance modality is based on specific differences between imaging systems, as well as other variables including cost, patient safety, operator expertise, and complexity of procedure. We will compare the adjunctive imaging tools for structural heart disease interventions, with a focus on intracardiac echocardiography and real-time three-dimensional transesophageal echocardiography.

The Added Value of Real-time 3-Dimensional Echocardiography in the Diagnosis of Isolated Cleft Mitral Valve in Adults

We evaluated the potential advantage of real-time 3-dimensional echocardiography on the assessment of mitral valve morphology and function in patients with isolated cleft mitral valve. Five patients, aged 33 +/- 9 years, with isolated cleft mitral valve and no associated cardiac anomalies, were studied. Real-time 3-dimensional echocardiography demonstrated the cleft in each case and allowed the measurement of its width and depth, the extent of cleft edge fibrosis and retraction, and the presence of accessory chordae and their attachment to the septum. Four patients had moderate or severe mitral regurgitation and in one patient the regurgitation was mild. In all patients the mitral regurgitant jet originating from the cleft was detected, and in one patient, a second jet was detected and not seen in the 2-dimensional study. Real-time 3-dimensional echocardiography is a reliable and reproducible technique that provides accurate and detailed echocardiographic characterization of the isolated cleft mitral valve in adults.

Real-time three-dimensional echocardiography for rheumatic mitral valve stenosis evaluation

OBJECTIVES

Our aim was to assess which echo-Doppler method has the best agreement with the mitral valve area (MVA) invasively evaluated by the Gorlin's formula. We also evaluated the feasibility and reproducibility of real-time three-dimensional echocardiography (RT3D) for the estimation of MVA and the Wilkins score in patients with rheumatic mitral stenosis (RMVS).

BACKGROUND

Real-time three-dimensional echocardiography is a novel technique that allows us to visualize the mitral valvular anatomy in any desired plane orientation. The usefulness and accuracy of this technique for evaluating RMVS has not been established.

METHODS

We studied a series of consecutive patients with RMVS from two tertiary care hospitals. Mitral valvular area was determined by conventional echo-Doppler methods and by RT3D, and their results were compared with those obtained invasively. Real-time three-dimensional echocardiography planimetry and mitral score were measured by two independent observers and then repeated by one of them.

RESULTS

Eighty patients with RMVS comprised our study group (76 women; 50.6 +/- 13.9 years). Compared with all other echo-Doppler methods, RT3D had the best agreement with the invasively determined MVA (average difference between both methods and limits of agreement: 0.08 cm(2) [-0.48 to 0.6]). Interobserver variability was as good for RT3D (intraclass correlation coefficient [ICC] = 0.90) as for pressure half-time (PHT) (ICC = 0.95). For PHT and RT3D, the intraobserver variability was similar (ICC 0.92 and 0.96, respectively). Real-time three-dimensional echocardiography valvular score evaluation showed a better interobserver agreement with RT3D than with 2D echocardiography.

CONCLUSIONS

Real-time three-dimensional echocardiography is a feasible, accurate, and highly reproducible technique for assessing MVA in patients with RMVS. Real-time three-dimensional echocardiography has the best agreement with invasive methods.

Additional value of three-dimensional transesophageal echocardiography for patients with mitral valve stenosis undergoing balloon valvuloplasty

The objective of this study was to validate the additional value of 3-dimensional (3D) transesophageal echocardiography (TEE) for patients with mitral valve stenosis undergoing percutaneous mitral balloon valvotomy (PTMV). Therefore, in a series of 21 patients with severe mitral valve stenosis selected for PTMV, 3D TEE was performed before and after PTMV. The mitral valve area was assessed by planimetry pre- and post-PTMV; the mitral valve volume was assessed and attention was paid to the amount of fusion of the commissures. These results were compared with findings by 2-dimensional transthoracic echocardiography using pressure half-time method for assessment of mitral valve area, and were analyzed for the prediction of successful outcome. Pre-PTMV the mitral valve area assessed by 3D TEE was 1.0 +/- 0.3 cm(2) vs 1.2 +/- 0.4 cm(2) assessed by 2-dimensional transthoracic echocardiography (P =.03) and post-PTMV it was 1.8 +/- 0.5 cm(2) vs 1.9 +/- 0.6 cm(2) (not significant), respectively. The mitral valve volume could be assessed by 3D TEE (mean 2.4 +/- 2.5 cm(3)) and was inversely correlated to a successful PTMV procedure (P <.001). The 3D TEE method enabled a better description of the mitral valvular anatomy, especially post-PTMV. We conclude that 3D TEE will have additional value over 2-dimensional echocardiography in this group of patients, for selection of patients pre-PTMV, and for analyzing pathology of the mitral valve afterward.

Improved assessment of mitral valve stenosis by volumetric real-time three-dimensional echocardiography

OBJECTIVES

This study was performed to determine the feasibility, accuracy and reproducibility of real-time volumetric three-dimensional echocardiography (3-D echo) for the estimation of mitral valve area in patients with mitral valve stenosis.

BACKGROUND

Planimetry of the mitral valve area (MVA) by two-dimensional echocardiography (2-D echo) requires a favorable parasternal acoustic window and depends on operator skill. Transthoracic volumetric 3-D echo allows reconstruction of multiple 2-D planes in any desired orientation and is not limited to parasternal acquisition, and could thus enhance the accuracy and feasibility of calculating MVA.

METHODS

In 48 patients with mitral stenosis (40 women; mean age 61 +/- 13 years) MVA was determined by planimetry using volumetric 3-D echo and compared with measurements obtained by 2-D echo and Doppler pressure half-time (PHT). All measurements were performed by two independent observers. Volumetric data were acquired from an apical view.

RESULTS

Although 2-D echo allowed planimetry of the mitral valve in 43 of 48 patients (89%), calculation of the MVA was possible in all patients when 3-D echo was used. Mitral valve area by 3-D echo correlated well with MVA by 2-D echo (r = 0.93, mean difference, 0.09 +/- 0.14 cm2) and by PHT (r = 0.87, mean difference, 0.16 +/- 0.19 cm2). Interobserver variability was significantly less for 3-D echo than for 2-D echo (SD 0.08cm2 versus SD 0.23cm2, p < 0.001). Furthermore, it was much easier and faster to define the image plane with the smallest orifice area when 3-D echo was used.

CONCLUSIONS

Transthoracic real-time volumetric 3-D echo provides accurate and highly reproducible measurements of mitral valve area and can easily be performed from an apical approach.

Stereolithographic biomodeling to create tangible hard copies of cardiac structures from echocardiographic data: in vitro and in vivo validation

OBJECTIVES

This study investigated the feasibility, accuracy and clinical potential of creating polymer hard copies of echocardiographic data using stereolithography.

BACKGROUND

Three-dimensional (3D) echocardiography has so far been limited by the need to display reconstructed 3D objects on a two-dimensional screen. Thus, tangible stereolithographic polymer models created from echocardiographic data could enhance our spatial perception of cardiac anatomy and pathology.

METHODS

Hard-copy replicas of water-filled latex balloon phantoms (n = 7) and porcine liver specimens (n = 12) were generated from echocardiographic images using stereolithography (computerized laser polymerization). In addition, we created 24 models of the mitral valve from 12 transesophageal studies (normal = 6, mitral stenosis n = 4, prolapse/flail leaflet n = 8, annular dilation n = 2, leaflet restriction n = 2 and following mitral valve repair n = 2).

RESULTS

Excellent agreement was found for comparison of volumes (r = 0.98, SEE = 3.46 mm3, mean difference = 0.25 +/- 3.33 mm3) and maximal dimensions (r = 0.99, SEE = 0.16 cm, mean difference = 0.03 +/- 0.16 cm) between phantoms and their corresponding replicas. Visual and tactile examination of mitral valve models by two blinded observers allowed correct depiction of mitral valve anatomy and pathology in all cases.

CONCLUSIONS

Stereolithographic modeling of echocardiographic images is feasible and provides tangible polyacrylic models that are true to scale, shape and volume. Such models offer accurate depiction of mitral valve anatomy and pathology in patients studied with transesophageal echocardiography. This technique could have substantial impact on diagnosis, management and preoperative planning in complex cardiovascular disorders.

Three-dimensional ultrasound imaging

The objective of this article is to provide scientists, engineers and clinicians with an up-to-date overview on the current state of development in the area of three-dimensional ultrasound (3-DUS) and to serve as a reference for individuals who wish to learn more about 3-DUS imaging. The sections will review the state of the art with respect to 3-DUS imaging, methods of data acquisition, analysis and display approaches. Clinical sections summarize patient research study results to date with discussion of applications by organ system. The basic algorithms and approaches to visualization of 3-D and 4-D ultrasound data are reviewed, including issues related to interactivity and user interfaces. The implications of recent developments for future ultrasound imaging/visualization systems are considered. Ultimately, an improved understanding of ultrasound data offered by 3-DUS may make it easier for primary care physicians to understand complex patient anatomy. Tertiary care physicians specializing in ultrasound can further enhance the quality of patient care by using high-speed networks to review volume ultrasound data at specialization centers. Access to volume data and expertise at specialization centers affords more sophisticated analysis and review, further augmenting patient diagnosis and treatment.

Three-dimensional fetal echocardiography

The complex anatomy and dynamics of the heart make it a challenging organ to image. The fetal heart is particularly difficult because it is located deep within the mother's abdomen and direct access to electrocardiographic information is difficult. Thus more complex imaging and analysis methods are necessary to obtain information regarding fetal cardiac anatomy and function. This information can be used for medical diagnosis, model development and theoretical validation. The objective of this article is to provide scientists and engineers with an overview of three-dimensional fetal echocardiography.

MRI and echocardiography: how do they compare in adults?

TTE with color flow imaging remains the most appropriate initial method for imaging CHD in adults. In many patients with minor abnormalities, this will be the only imaging required. For complicated intracardiac anomalies not well shown by TTE, TEE or MRI are usually adequate with the choice of technique being dependent on the availability of appropriate equipment and expertise. For great vessel abnormalities, further evaluation with MRI and MRA is most appropriate. In patients suspected of having significant systemic or pulmonary venous abnormalities or abnormalities of the aortic arch, MRI and MRA should be regarded as the definitive imaging technique. MRI and MRA are robust methods for evaluating intracardiac disease and can provide accurate information on cardiac chamber anatomy relationships, valvar lesions, and shunts. However, in most patients, this information is provided more rapidly and cost effectively by color Doppler echocardiography.

Quantitative assessment of the operative results after extended myectomy and surgical reconstruction of the subvalvular mitral apparatus in hypertrophic obstructive cardiomyopathy using dynamic three-dimensional transesophageal echocardiography

OBJECTIVES

The aim of this study was to examine the value of dynamic three-dimensional (3D) transesophageal echocardiography (TEE) for the postoperative evaluation after extended myectomy and surgical reconstruction of the subvalvular mitral valve apparatus in patients with hypertrophic obstructive cardiomyopathy (HOCM).

BACKGROUND

Two-dimensional imaging techniques such as echocardiography, computed tomography and magnetic resonance imaging have not been able to precisely quantify the effects of surgical therapy on the morphology of the left ventricular outflow tract (LVOT).

METHODS

Multiplane TEE with 3D reconstruction was performed in 11 patients before and after the operation and in 16 normal control subjects for comparison. The preoperative maximal systolic pressure gradient in the LVOT was 69 +/- 59 mm Hg. The following variables were measured within the dynamic 3D data set: depth, width, length and cross-sectional area (CSA) gain caused by the myectomy trough, minimal CSA of the LVOT at each time point and its cyclic changes and maximal mitral leaflet deviation during systole.

RESULTS

Functional class improved from 3.0 +/- 0.2 before the operation to 1.5 +/- 0.6 after it. The maximal systolic pressure gradient in the outflow tract decreased to 26 +/- 21 mm Hg postoperatively (p < 0.001). Minimal CSA of the outflow tract increased from 1.1 +/- 1.2 to 3.8 +/- 1.9 cm2 postoperatively (p < 0.001), similar to the value of the control group (4.2 +/- 1.5 cm2, p = NS). The area gain due to the myectomy trough was 1.3 +/- 1.0 cm2, corresponding to 48 +/- 12% of the total operative area difference. Maximal systolic depth of the myectomy was 7 +/- 2 mm, maximal width was 20 +/- 8 mm and length was 28 +/- 7 mm. Maximal deviation of the mitral leaflets fell from 15 +/- 7 to 6 +/- 7 mm postoperatively (p < 0.01). In five patients mass measurements of the intracavitary portion of the papillary muscle (PM) revealed an increase from 7.3 +/- 1.0 to 12.1 +/- 2.5 g due to surgical mobilization of PMs (p < 0.01).

CONCLUSIONS

3D TEE quantifies the differences in outflow tract morphology before and after surgery for HOCM. This technique may have an impact on the planning of operative interventions and allow for the evaluation of its results.