The Emerging Role of Three-Dimensional Echocardiography in Mitral Valve Repair

Quantitative three-dimensional echocardiographic analysis of the bicuspid aortic valve and aortic root: A single modality approach

BACKGROUND

Patients with bicuspid aortic valves (BAV) are heterogeneous with regard to patterns of root remodeling and valvular dysfunction. Two-dimensional echocardiography is the standard surveillance modality for patients with aortic valve dysfunction. However, ancillary computed tomography or magnetic resonance imaging is often necessary to characterize associated patterns of aortic root pathology. Conversely, the pairing of three-dimensional (3D) echocardiography with novel quantitative modeling techniques allows for a single modality description of the entire root complex. We sought to determine 3D aortic valve and root geometry with this quantitative approach.

METHODS

Transesophageal real-time 3D echocardiography was performed in five patients with tricuspid aortic valves (TAV) and in five patients with BAV. No patient had evidence of valvular dysfunction or aortic root pathology. A customized image analysis protocol was used to assess 3D aortic annular, valvular, and root geometry.

RESULTS

Annular, sinus and sinotubular junction diameters and areas were similar in both groups. Coaptation length and area were higher in the TAV group (7.25 ±  0.98 mm and 298 ± 118 mm² , respectively) compared to the BAV group (5.67 ± 1.33 mm and 177 ± 43 mm² ; P = .07 and P = .01). Cusp surface area to annular area, coaptation height, and the sub- and supravalvular tenting indices did not differ significantly between groups.

CONCLUSIONS

Single modality 3D echocardiography-based modeling allows for a quantitative description of the aortic valve and root geometry. This technique together with novel indices will improve our understanding of normal and pathologic geometry in the BAV population and may help to identify geometric predictors of adverse remodeling and guide tailored surgical therapy.

Quantitative Description of Mitral Valve Geometry Using Real-Time Three-Dimensional Echocardiography

Objectives

Leaflet and annular geometry are important determinants of mitral valve (MV) stress. Repair techniques which optimize valvular geometry will reduce stress and potentially increase repair durability. The development of such procedures will require image processing methodologies that provide a quantitative description of three-dimensional valvular geometry. Using three-dimensional echocardiography in conjunction with novel geometric modeling and rendering techniques, we have developed a high-resolution, quantitative, three-dimensional methodology for imaging the human MV.

Methods

Five normal adults underwent MV imaging using real-time three-dimensional echocardiography. Using specially designed image analysis software, multiple valvular geometric parameters, including the magnitude and orientation of leaflet curvature, leaflet surface area, annular height, intercommissural width, septolateral annular diameter, and annular area were determined for each subject. Image rendering techniques that allow for the clear and concise presentation of this detailed information are also presented.

Results

Although three-dimensional annular and leaflet geometry were found to be highly conserved among normal human subjects, substantial regional variation in leaflet geometry was observed. Interestingly, leaflet geometric heterogeneity was most pronounced in the midposterior leaflet, the region most commonly involved in leaflet flail in subjects with myxomatous disease.

Conclusions

The image processing and graphical rendering techniques that we have developed can be used to provide a complete description of three-dimensional MV geometry in human subjects. Widespread application of these techniques to normal subjects and patients with MV disease will provide insight into the geometric basis of both valvular pathology and repair durability.

On the simulation of mitral valve function in health, disease, and treatment

The mitral valve (MV) is the heart valve that regulates blood ?ow between the left atrium and left ventricle (LV). In situations where the MV fails to fully cover the left atrioventricular ori?ce during systole, the resulting regurgitation causes pulmonary congestion, leading to heart failure and/or stroke. The causes of MV insuf?ciency can be either primary (e.g. myxomatous degeneration) where the valvular tissue is organically diseased, or secondary (typically inducded by ischemic cardiomyopathy) termed ischemic mitral regurgitation (IMR), is brought on by adverse LV remodeling. IMR is present in up to 40% of patients and more than doubles the probability of cardiovascular morbidity after 3.5 years. There is now agreement that adjunctive procedures are required to treat IMR caused by lea?et tethering. However, there is no consensus regarding the best procedure. Multicenter registries and randomized trials would be necessary to prove which procedure is superior. Given the number of proposed procedures and the complexity and duration of such studies, it is highly unlikely that IMR procedure optimization will be achieved by prospective clinical trials. There is thus an urgent need for cell and tissue physiologically based quantitative assessments of MV function to better design surgical solutions and associated therapies. Novel computational approaches directed towards optimized surgical repair procedures can substantially reduce the need for such trial-and-error approaches. We present the details of our MV modeling techniques, with an emphasis on what is known and investigated at various length scales.

Role of modern 3D echocardiography in valvular heart disease

Three-dimensional (3D) echocardiography has been conceived as one of the most promising methods for the diagnosis of valvular heart disease, and recently has become an integral clinical tool thanks to the development of high quality real-time transesophageal echocardiography (TEE). In particular, for mitral valve diseases, this new approach has proven to be the most unique, powerful, and convincing method for understanding the complicated anatomy of the mitral valve and its dynamism. The method has been useful for surgical management, including robotic mitral valve repair. Moreover, this method has become indispensable for nonsurgical mitral procedures such as edge to edge mitral repair and transcatheter closure of paravaluvular leaks. In addition, color Doppler 3D echo has been valuable to identify the location of the regurgitant orifice and the severity of the mitral regurgitation. For aortic and tricuspid valve diseases, this method may not be quite as valuable as for the mitral valve. However, the necessity of 3D echo is recognized for certain situations even for these valves, such as for evaluating the aortic annulus for transcatheter aortic valve implantation. It is now clear that this method, especially with the continued development of real-time 3D TEE technology, will enhance the diagnosis and management of patients with these valvular heart diseases.

Feasibility of in vivo human aortic valve modeling using real-time three-dimensional echocardiography

BACKGROUND

Surgical techniques for aortic valve (AV) repair are directed toward restoring normal structural relationships in the aortic root and rely on detailed assessment of root and valve anatomy. Noninvasive three-dimensional (3D) imaging and modeling may assist in patient selection and operative planning.

METHODS

Transesophageal real-time 3D echocardiographic images of 5 patients with normal AVs were acquired. The aortic root and the annulus were manually segmented at end diastole using a 36-point rotational template. The AV leaflets and the coaptation zone were manually segmented in parallel 1-mm cross sections. Quantitative 3D models of the AV and root were generated and used to measure standard anatomic parameters and were compared to conventional two-dimensional echocardiographic measurements. All measurements are given as mean±SD.

RESULTS

Annular, sinus, and sinotubular junction areas were 4.1±0.6 cm2, 7.5±1.2 cm2, and 3.9±1.0 cm2, respectively. Root diameters (measured in three locations) by 3D model inspection and two-dimensional echocardiography measurement correlated (R2=0.75). Noncoapted areas of the left, right, and noncoronary leaflets were 1.9±0.2 cm2, 1.6±0.3 cm2, and 1.6±0.3 cm2, respectively. Mean coaptation areas for the left-right, left-noncoronary, and right-noncoronary coaptation zones were 87.7±36.9 mm2, 69.9±20.7 mm2, and 114.2±23.0 mm2, respectively. The mean ratio of noncoapted leaflet area to annular area was 1.3±0.2.

CONCLUSIONS

High-resolution 3D models of the in vivo normal human aortic root and valve were generated using 3D echocardiography. Quantitative 3D models and analysis may assist in characterization of pathology and decision making for AV repair.

Real-time three-dimensional transesophageal echocardiography to predict artificial chordae length for mitral valve repair

Background

Artificial chordae replacement is an effective technique for mitral valve repair, however, it is difficult to accurately determine the length of artificial chordae. This study aimed to assess the reliability and accuracy of real-time three-dimensional transesophageal echocardiography (TEE) to predict the length of artificial chordae preoperatively.

Methods

From December 2008 to December 2010, 48 patients with severe mitral regurgitation successfully underwent mitral valve repair using artificial chordae replacement. The patients were divided into a TEE pre-measurement group (n = 26) and a direct measurement group (n = 22), according to the method used to determine the length of artificial chordae. Cardiopulmonary bypass time, aortic cross-clamp time, and the recurrence rate of moderate or severe mitral regurgitation were compared between the two groups.

Results

There were no operative deaths in either group. The mean cardiopulmonary bypass time was 113.0 ± 18.7 min and 127.0 ± 28.9 min (p < 0.05), and the aortic cross-clamp time was 70.0 ± 16.6 min and 86.0 ± 20.7 min (p < 0.05) in the TEE pre-measurement group and direct measurement group, respectively. The difference between the pre-measured artificial chordal length and actual constructed artificial chordal length was not significant in the TEE pre-measurement group (p > 0.05). Although the difference in the incidence of moderate or severe mitral regurgitation between the two groups was not significant (p > 0.05), the incidence in the TEE pre-measurement group (3.8%) was lower than that in the direct measurement group (18.2%).

Conclusions

Real-time three-dimensional transesophageal echocardiography can accurately predict the length of artificial chordae required for mitral valve repair, and shortens cardiopulmonary bypass time and aortic cross-clamp time while improving the results of mitral valve repair.

Ischemic mitral regurgitation: recent advances

This article reviews recent developments in the pathophysiology and management of ischemic mitral regurgitation. Recent imaging studies using three-dimensional echocardiography have added clarity to the mechanism responsible for this condition. This article also discusses recent studies on outcomes of surgical repair, including current results and potential risks of restrictive annuloplasty. Because of the limitations imposed by restrictive annuloplasty, adjunctive surgical methods focusing on the left ventricle or papillary muscles are being investigated to address this disease. In the interim, a downsized complete rigid or semirigid annuloplasty repair appears to offer good midterm outcomes.

A study of functional anatomy of aortic-mitral valve coupling using 3D matrix transesophageal echocardiography

BACKGROUND

Mitral and aortic valves are known to be coupled via fibrous tissue connecting the two annuli. Previous studies evaluating this coupling have been limited to experimental animals using invasive techniques. The new matrix array transesophageal transducer provides high-resolution real-time 3D images of both valves simultaneously. We sought to develop and test a technique for quantitative assessment of mitral and aortic valve dynamics and coupling.

METHODS AND RESULTS

Matrix array transesophageal (Philips iE33) imaging was performed in 24 patients with normal valves who underwent clinically indicated transesophageal echocardiography. Custom software was used to detect and track the mitral and aortic annuli in 3D space throughout the cardiac cycle, allowing automated measurement of changes in mitral and aortic valve morphology. Mitral annulus surface area and aortic annulus projected area changed reciprocally over time. Mitral annulus surface area was 8.0+/-2.1 cm(2) at end-diastole and decreased to 7.7+/-2.1 cm(2) in systole, reaching its maximum (10.0+/-2.2 cm(2)) at mitral valve opening. Aortic annulus projected area was 4.1+/-1.2 cm(2) at end-diastole, then increased during isovolumic contraction reaching its maximum (4.8+/-1.3 cm(2)) in the first third of systole and its minimum (3.6+/-1.0 cm(2)) during isovolumic relaxation. The angle between the mitral and aortic annuli was maximum (136+/-13 degrees ) at end-diastole and decreased to its minimum value (129+/-11 degrees ) during systole.

CONCLUSIONS

This is the first study to report quantitative 3D assessment of the mitral and aortic valve dynamics from matrix array transesophageal images and describe the mitral-aortic coupling in a beating human heart. This ability may have impact on patient evaluation for valvular surgical interventions and prosthesis design.

Future potential of echocardiography in heart failure

Echocardiography represents a convenient, portable and noninvasive method to provide important anatomic and physiologic information to inform the management of heart failure patients. Traditional echo assessments include diagnostic, etiologic and prognostic data from ventricular size, geometry and performance. Newer echocardiographic techniques are receiving greater utilization, however, and promise to further enhance diagnostic abilities in heart failure. This article reviews traditional anatomic assessments, echo-based cardiac hemodynamics, 3D echocardiography, quantification of myocardial tissue mechanics and hand-carried echocardiography. These developments in echocardiography underlie future trends toward echo objectivity, improved imaging of patients with poor acoustic windows, miniaturization and simplicity in focused exams and the expanded application of old and new techniques.

Beating-heart patch closure of muscular ventricular septal defects under real-time three-dimensional echocardiographic guidance: a preclinical study

OBJECTIVES

Safe and effective device closure of ventricular septal defects remains a challenge. We have developed a transcardiac approach to close ventricular septal defects using a patch delivery and fixation system that can be secured under real-time three-dimensional echocardiographic guidance.

METHODS

In Yorkshire pigs (n = 8) a coring device was introduced into the left ventricle through a purse-string suture placed on the left ventricular apex, and a muscular ventricular septal defect was created. The patch deployment device containing a 20-mm polyester patch was advanced toward the ventricular septal defect through another purse-string suture on the left ventricular apex, and the patch was deployed under real-time three-dimensional echocardiographic guidance. The anchor delivery device was then introduced into the left ventricle through the first purse-string suture. Nitinol anchors to attach the patch around the ventricular septal defect were deployed under real-time three-dimensional echocardiographic guidance. After patch attachment, residual shunts were sought by means of two-dimensional and three-dimensional color Doppler echocardiography. The heart was then excised, and the septum with the patch was inspected.

RESULTS

A ventricular septal defect was created in the midventricular (n = 4), anterior (n = 2), and apical (n = 2) septum. The mean size was 9.8 mm (8.2-12.0 mm), as determined by means of two-dimensional color Doppler scanning. The ventricular septal defects were completely closed in 7 animals. In one a 2.4-mm residual shunt was identified. No anatomic structures were compromised.

CONCLUSIONS

Beating-heart perventricular muscular ventricular septal defect closure without cardiopulmonary bypass can be successfully achieved by using a catheter-based patch delivery and fixation system under real-time three-dimensional echocardiographic guidance. This approach might be a better alternative to cardiac surgery or transcatheter device closure.

Imaging studies in patients with heart failure: current and evolving technologies

Technological advances continue to expand the clinical role of echocardiography in the intensive care unit, particularly in patients with heart failure. It has many advantages over tomographic techniques such as echo cardiac magnetic resonance imaging and cardiac computed tomography, can provide rapid bedside cardiac assessment, and facilitate emergent decision-making for critically ill patients. Image quality problems in the intensive care setting have largely been overcome by the use of harmonic imaging, contrast opacification, and when indicated, transesophageal echocardiography. Newer techniques promise to advance the scope and prognostic power of echocardiography, and to expand the portability and availability of this tool.

Etiologic classification of degenerative mitral valve disease: Barlow's disease and fibroelastic deficiency

Barlow's disease and fibroelastic deficiency are the two dominant forms of degenerative mitral valve disease and have unique differentiating characteristics on clinical and echocardiographic assessment. Preoperative differentiation of patients by both cardiologists and surgeons is important because the techniques, surgical skill, and expertise required to achieve a repair vary among these etiological subsets. Barlow's patients often have multiple complex lesions, thus high rates of repair are only likely to be achieved by a reference mitral valve repair surgeon. In contrast, many forms of fibroelastic disease should be repaired at a high rate by experienced general cardiac surgeons. In this article, we highlight the differentiation of Barlow's disease and fibroelastic deficiency.

Regional and global patterns of annular remodeling in ischemic mitral regurgitation

BACKGROUND

The mammalian mitral annulus is saddle shaped. Experimental studies have shown that loss of saddle shape occurs in ischemic mitral regurgitation. However, neither the temporal pattern of global annular remodeling nor the geometric pattern of regional annular remodeling has been described. We sought to characterize these changes using real-time three-dimensional echocardiography in an ovine model.

METHODS

Ten sheep underwent real-time three-dimensional echocardiography at baseline and 1 hour and 8 weeks after posterobasal myocardial infarction. Multiple mitral annular geometric indexes were measured at each time point to assess regional and global annular remodeling.

RESULTS

One hour after infarction, global annular height decreased from 5.8 +/- 0.5 mm to 4.0 +/- 0.4 mm (p < 0.001) while intercommissural width increased from 29.0 +/- 1.3 mm to 35.7 +/- 1.7 mm (p = 0.023), resulting in a decrease in the global annular height to commissural width ratio from 20.0% +/- 1.6% to 11.2% +/- 0.9% (p < 0.001). Eight weeks after infarction, global annular height decreased to 3.9 +/- 0.2 mm (p < 0.05) while intercommissural width increased to 40.7 +/- 1.5 mm (p < 0.001), resulting in an additional decrease in the global annular height to commissural width ratio to 9.4% +/- 0.4% (p < 0.001). Although annular remodeling involved the entire mitral annulus, there was regional heterogeneity in its extent.

CONCLUSIONS

Significant global annular flattening and dilatation occur during the development of ischemic mitral regurgitation in an ovine model. Regional annular remodeling is heterogeneous and is not limited the posterior commissure or the posterior annulus.