Three-dimensional echocardiographic reconstruction of the mitral valve, with implications for the diagnosis of mitral valve prolapse

The effect of pure mitral regurgitation on mitral annular geometry and three-dimensional saddle shape

OBJECTIVE

Chronic ischemic mitral regurgitation is associated with mitral annular dilatation in the septal-lateral dimension and flattening of the annular 3-dimensional saddle shape. To examine whether these perturbations are caused by the ischemic insult, mitral regurgitation, or both, we investigated the effects of pure mitral regurgitation (low pressure volume overload) on annular geometry and shape.

METHODS

Eight radiopaque markers were sutured evenly around the mitral annulus in sheep randomized to control (CTRL, n = 8) or experimental (HOLE, n = 12) groups. In HOLE, a 3.5- to 4.8-mm hole was punched in the posterior leaflet to generate pure mitral regurgitation. Four-dimensional marker coordinates were obtained radiographically 1 and 12 weeks postoperatively. Mitral annular area, annular septal-lateral and commissure-commissure dimensions, and annular height were calculated every 16.7 ms.

RESULTS

Mitral regurgitation grade was 0.4 +/- 0.4 in CTRL and 3.0 +/- 0.8 in HOLE (P < .001) at 12 weeks. End-diastolic left ventricular volume index was greater in HOLE at both 1 and 12 weeks; end-systolic volume index was larger in HOLE at 12 weeks. Mitral annular area increased in HOLE predominantly in the commissure-commissure dimension, with no difference in annular height between HOLE versus CTRL at 1 or 12 weeks, respectively.

CONCLUSION

In contrast with annular septal-lateral dilatation and flattening of the annular saddle shape observed with chronic ischemic mitral regurgitation, pure mitral regurgitation was associated with commissure-commissure dimension annular dilatation and no change in annular shape. Thus, infarction is a more important determinant of septal-lateral dilatation and annular shape than mitral regurgitation, which reinforces the need for disease-specific designs of annuloplasty rings.

A methodology for assessing human mitral leaflet curvature using real-time 3-dimensional echocardiography

OBJECTIVES

Using 3-dimensional echocardiography in conjunction with novel geometric modeling and rendering techniques, we have developed a high-resolution, quantitative, 3-dimensional methodology for imaging the human mitral valve. Leaflet and annular geometry are important determinants of mitral valve stress. Repair techniques that 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 3-dimensional valvular geometry.

METHODS

Ten healthy adult subjects underwent mitral valve imaging with real-time 3-dimensional echocardiography. By using specially designed image analysis software, multiple valvular geometric parameters, including 2- and 3-dimensional 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 3-dimensional annular and leaflet geometry were found to be highly conserved between healthy human subjects in general, substantial intrasubject and intersubject regional geometric heterogeneity was observed in the midposterior leaflet, the region most commonly involved in leaflet flail in subjects with myxomatous disease.

CONCLUSIONS

The image-processing and graphic-rendering techniques that we have developed can be used to provide a complete description of 3-dimensional mitral valve geometry in human subjects. Widespread application of these techniques to healthy subjects and patients with mitral valve disease will provide insight into the geometric basis of both valvular pathology and repair durability.

The influence of annuloplasty ring geometry on mitral leaflet curvature

BACKGROUND

The effect of mitral leaflet curvature on stress reduction is an important mechanism in optimizing valve function. We hypothesize that annuloplasty ring shape could directly influence leaflet curvature and, potentially, repair durability. We describe an echocardiographically based methodology for quantifying mitral valve geometry and its application to the characterization of ovine mitral valve geometry before and after implantation of an annuloplasty ring.

METHODS

Multiple mitral annular and leaflet geometric variables were calculated for 8 naïve adult male sheep using real-time three-dimensional echocardiographic images. These indexes were recalculated after annuloplasty using a 30-mm Carpentier-Edward Physio ring (n = 4; Edwards Lifesciences, Irvine, CA) or a 30-mm saddle ring (n = 4).

RESULTS

After implantation of the Physio ring, the annular height to commissural width ratio (AHCWR) decreased from 19.4% +/- 2.3% to 11.1% +/- 2.5% (p = 0.06). After implantation of the saddle ring, AHCWR increased from 19.6% +/- 1.3% to 24.3% +/- 1.3% (p < 0.05). Statistically significant increases in three-dimensional Gaussian curvature occurred after implantation within six defined leaflet regions (A1 to A3, P1 to P3) of the saddle ring but only within the P1 and P3 leaflet regions with the Physio ring.

CONCLUSIONS

Annuloplasty ring shape affects leaflet curvature. Implantation of a saddle ring reflecting normal human annular geometry augmented ovine annular nonplanarity and increased three-dimensional leaflet curvature across the entire mitral valve surface. The Physio ring decreased annular nonplanarity and increased leaflet curvature only across limited regions of the posterior leaflet. These findings confirm the hypothesis that ring design influences leaflet curvature.

Mitral leaflet adaptation to ventricular remodeling: occurrence and adequacy in patients with functional mitral regurgitation

BACKGROUND

Functional mitral regurgitation (MR) is caused by systolic traction on the mitral leaflets related to ventricular distortion. Little is known about whether chronic tethering causes the mitral leaflet area to adapt to the geometric needs imposed by tethering, in part because of inability to reconstruct leaflet area in vivo. Our aim was to explore whether adaptive increases in leaflet area occur in patients with functional MR compared with normal subjects and to test the hypothesis that leaflet area influences MR severity.

METHODS AND RESULTS

A new method for 3-dimensional echocardiographic measurement of mitral leaflet area was developed and validated in vivo against 15 sheep heart valves, later excised. This method was then applied in 80 consecutive patients from 3 groups: patients with normal hearts by echocardiography (n=20), patients with functional MR caused by isolated inferior wall-motion abnormality or dilated cardiomyopathy (n=29), and patients with inferior wall-motion abnormality or dilated cardiomyopathy but no MR (n=31). Leaflet area was increased by 35+/-20% in patients with LV dysfunction compared with normal subjects. The ratio of leaflet to annular area was 1.95+/-0.40 and was not different among groups, which indicates a surplus leaflet area that adapts to left-heart changes. In contrast, the ratio of total leaflet area to the area required to close the orifice in midsystole was decreased in patients with functional MR compared with those with normal hearts (1.29+/-0.15 versus 1.78+/-0.39, P=0.001) and compared with patients with inferior wall-motion abnormality or dilated cardiomyopathy but no MR (1.81+/-0.38, P=0.001). After adjustment for measures of LV remodeling and tethering, a leaflet-to-closure area ratio <1.7 was associated with significant MR (odds ratio 23.2, 95% confidence interval 2.0 to 49.1, P=0.02).

CONCLUSIONS

Mitral leaflet area increases in response to chronic tethering in patients with inferior wall-motion abnormality and dilated cardiomyopathy, but the development of significant MR is associated with insufficient leaflet area relative to that demanded by tethering geometry. The varying adequacy of leaflet adaptation may explain in part the heterogeneity of this disease among patients. The results suggest the need to understand the mechanisms that underlie leaflet adaptation and whether leaflet area can potentially be modified as part of the therapeutic approach.

A multiplanar three dimensional echocardiographic study of mitral valvar annular function in children with normal and regurgitant valves

INTRODUCTION

The mitral valvar complex is difficult to visualise accurately in only two dimensions. Three-dimensional echocardiography gives new insight into the dynamic changes of intra-cardiac structures during the cardiac cycle. The aim of this study was to study the mitral annulus in systole and diastole in normal children using three-dimensional echocardiography, and to analyse the effect of regurgitation on annular function.

MATERIALS AND METHODS

Three-dimensional echocardiographic datasets, acquired in 11 consecutive subjects with mitral regurgitation, and 20 normal subjects, were analysed offline using simultaneous multiplanar review.

RESULTS

The mitral valvar annular area decreased in diastole, and increased in systole, in both groups. The annulus in patients with mitral regurgitation is dilated compared to normal subjects, the systolic value for those with regurgitation having a mean of 6.79 plus or minus 2.55 centimetres2/metres2, and the diastolic value a mean of 5.01 plus or minus 1.78 centimetres2/metres2, as opposed to a systolic mean value of 5.28 centimetres2/metres2 plus or minus 1.68, p = 0.091, and diastolic mean value of 3.05 centimetres2/metres2 plus or minus 0.90, in normal subjects (p less than 0.0001). The proportional change in mitral valvar annular area from systole to diastole showed a trend towards being smaller in those with mitral regurgitation, although this did not reach significance (24.8% versus 41.13%, p equal to 0.249). Analysis of subgroups of patients with moderate or severe mitral regurgitation showed mitral excursion, expressed as percentage of left ventricular length, to be significantly less than in normal subjects, at 12.78 plus or minus 5.10% versus 15.84 plus or minus 4.23% (p equal to 0.012).

CONCLUSIONS

Mitral valvar annular area in children decreases in diastole, and increases in systole. In those with mitral regurgitation, the annulus is dilated and the dynamic annular function is depressed.

Material properties of the ovine mitral valve anterior leaflet in vivo from inverse finite element analysis

We measured leaflet displacements and used inverse finite-element analysis to define, for the first time, the material properties of mitral valve (MV) leaflets in vivo. Sixteen miniature radiopaque markers were sewn to the MV annulus, 16 to the anterior MV leaflet, and 1 on each papillary muscle tip in 17 sheep. Four-dimensional coordinates were obtained from biplane videofluoroscopic marker images (60 frames/s) during three complete cardiac cycles. A finite-element model of the anterior MV leaflet was developed using marker coordinates at the end of isovolumic relaxation (IVR; when the pressure difference across the valve is approximately 0), as the minimum stress reference state. Leaflet displacements were simulated during IVR using measured left ventricular and atrial pressures. The leaflet shear modulus (G(circ-rad)) and elastic moduli in both the commisure-commisure (E(circ)) and radial (E(rad)) directions were obtained using the method of feasible directions to minimize the difference between simulated and measured displacements. Group mean (+/-SD) values (17 animals, 3 heartbeats each, i.e., 51 cardiac cycles) were as follows: G(circ-rad) = 121 +/- 22 N/mm2, E(circ) = 43 +/- 18 N/mm2, and E(rad) = 11 +/- 3 N/mm2 (E(circ) > E(rad), P < 0.01). These values, much greater than those previously reported from in vitro studies, may result from activated neurally controlled contractile tissue within the leaflet that is inactive in excised tissues. This could have important implications, not only to our understanding of mitral valve physiology in the beating heart but for providing additional information to aid the development of more durable tissue-engineered bioprosthetic valves.

Three-dimensional adult echocardiography: where the hidden dimension helps

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

Accuracy of real-time 3-dimensional echocardiography in the assessment of mitral prolapse. Is transesophageal echocardiography still mandatory?

BACKGROUND

Segmental analysis in mitral prolapse is important to decide the chances of valvular repair. Multiplane transesophageal echocardiography (TEE) is the only echocardiographic tool validated for this aim hitherto. The aim of the study was to assess if segmental analysis can be performed with transthoracic real-time 3-dimensional (3D) echocardiography as accurately as with TEE, hence representing a valid alternative to TEE.

METHODS

Forty-one consecutive patients diagnosed with mitral prolapse underwent TEE and a complete 3D echocardiography study, including parasternal and apical real-time; apical full-volume; and 3D color full-volume. Investigators performing TEE were blinded to the 3D results.

RESULTS

Three-dimensional echocardiogram was feasible in 40 to 41 patients (97.7%). Ages ranged from 15 to 92 years, and all possible anatomical patterns of prolapse were represented. Thirty-seven patients (90.2%) had mitral regurgitation of any degree. The level of agreement was k = 0.93 (P < or = .0001), sensitivity of 96.7%, specificity of 96.7%, likelihood ratio for a positive result of 29.0%, and likelihood ratio for a negative result of 0.03%. Four false positives were found, corresponding to scallops A2 (1), A3 (2), and P3 (1). Four false negatives were found, corresponding to scallops A1 (2) and P1 (2). Sensitivity and specificity in the scallop P2 were 100%.

CONCLUSION

Segmental analysis in mitral prolapse can be performed with transthoracic real-time 3D echocardiography as accurately as with TEE. False negatives tend to appear around the anterolateral commissure, whereas false positives tend to appear around the posteromedial commissure. Highest accuracy was reached in central scallops.

The genetics of mitral valve prolapse

Mitral valve prolapse (MVP) is a very common clinical condition that refers to a systolic billowing of one or both mitral valve leaflets into the left atrium. Improvements of echocardiographic techniques and new insights in mitral valve anatomy and physiology have rendered the diagnosis of this condition more accurate and reliable. MVP can be sporadic or familial, demonstrating autosomal dominant and X-linked inheritance. Three different loci on chromosomes 16, 11 and 13 have been found to be linked to MVP, but no specific gene has been described. Another locus on chromosome X was found to cosegregate with a rare form of MVP called 'X-linked myxomatous valvular dystrophy'. MVP is more frequent in patients with connective tissue disorders including Marfan syndrome, Ehlers-Danlos and osteogenesis imperfecta. The purpose of this review is to describe previous studies on the genetics and prevalence of MVP. The report warrants the need for further genetically based studies on this common, albeit not fully understood, clinical entity.

Efficacy of chordal cutting in alleviating ischemic mitral regurgitation: insights from 3-dimensional echocardiography

Background

Ischemic mitral regurgitation often complicates severe ischemic heart disease and adversely affects the prognosis in these patients. There is wide variation in the clinical spectrum of ischemic mitral regurgitation due to varying location and chronicity of ischemia and anomalies in annular and ventricular remodeling. As a result, there is lack of consensus in treating these patients. Treatment has to be individualized for each patient. Most of the available surgical options do not consistently correct this condition in all the patients. Chordal cutting is one of the newer surgical approaches in which cutting a limited number of critically positioned basal chordae have found success by relieving the leaflet tethering and thereby improving the coaptation of leaflets. Three-dimensional echocardiography is a potentially valuable tool in identifying the specific pattern of tethering and thus the suitability of this procedure in a given clinical scenario.

Case Presentation

A 66-year-old man with cardiomyopathy and ischemic mitral regurgitation presented to us with the features of congestive heart failure. The three-dimensional echocardiography revealed severe mitral regurgitation associated with the tethering of the lateral (P1) and medial (P3) scallops of the posterior leaflet of the mitral valve due to secondary chordal attachments. The ejection fraction was only 15% with severe global systolic and diastolic dysfunction. Mitral regurgitation was successfully corrected with mitral annuloplasty and resection of the secondary chordae tethering the medial and lateral scallops of the posterior leaflet of the mitral valve.

Conclusion

Cutting the second order chordae along with mitral annuloplasty could be a novel method to remedy Ischemic mitral regurgitation by relieving the tethering of the valve leaflets. The preoperative three-dimensional echocardiography should be considered in all patients with Ischemic mitral regurgitation to assess the complex three-dimensional interactions between the mitral valve apparatus and the left ventricle. This aids in timely surgical planning.

Description of regional mitral annular nonplanarity in healthy human subjects: a novel methodology

OBJECTIVE

Finite-element analysis demonstrates that the nonplanar shape of the mitral annulus diminishes mitral leaflet stress. It has therefore been postulated that repair with annuloplasty rings that maintain the nonplanar shape of the annulus could increase repair durability. Although the global nonplanarity of the mitral annulus has been adequately characterized, design of such a ring requires a quantitative description of regional annular geometry. By using real-time 3-dimensional echocardiography in conjunction with available image processing software, we developed a methodology for describing regional annular geometry and applied it to the characterization of the normal human mitral annulus.

METHODS

Five healthy volunteers underwent mitral valve imaging with real-time 3-dimensional echocardiography. Regional annular height was calculated at 36 evenly spaced intervals.

RESULTS

Maximal annular height/commissural width ratio was found to occur at the midpoint of the anterior annulus in all cases. These values averaged 26% +/- 3.1%, whereas those for the midposterior annulus averaged 18% +/- 3.0%. The average commissural width was 35.2 +/- 6.0 mm. Although substantial spatial heterogeneity was observed, regional annular height at a given rotational position was highly conserved among subjects when normalized to commissural width.

CONCLUSIONS

These quantitative imaging and analytic techniques demonstrate that the normal human mitral annulus is regionally heterogeneous in its nonplanarity, and they establish a means of describing annular geometry at a regional level. With wider application, these techniques may be used both to characterize pathologic annular geometry and to optimize the design of mitral valve annuloplasty devices.

Live/real-time three-dimensional transthoracic assessment of mitral regurgitation and mitral valve prolapse

Evaluation of the mitral valve requires appreciation of its complex geometry. To accurately guide surgical interventions and describe pathology, three-dimensional transthoracic echocardiography (TTE) is an immense improvement over the cumbersome mental reconstruction required by two-dimensional approaches. Here we describe real-time, three-dimensional transthoracic techniques for assessing mitral regurgitation and mitral valve prolapse.

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.

Molecular genetics of mitral valve prolapse

PURPOSE OF REVIEW

Mitral valve prolapse is a common disorder with a strong hereditary component. It is associated with important mitral regurgitation requiring surgical repair and other clinical complications. Genetic studies can provide clues to mechanism and therapy.

RECENT FINDINGS

Advances in phenotypic classification have led to linkage to sites on chromosomes 11, 13 and 16 and identification of the first mutation in familial mitral valve prolapse not related to connective tissue syndromes - an X-linked filamin A mutation. New understanding of mechanism based on studies in a mouse Marfan model emphasize the dynamic interplay of differentiating cells and growth factors, with strong potential for therapy.

SUMMARY

This new knowledge brings us closer to the ultimate goal of preventing the progression of mitral valve disease to the stage of clinical expression.

Three-Dimensional Echo for the Assessment of Valvular Heart Disease

Three-dimensional echocardiography (3DE) is a valuable tool to be used in addition to and not instead of two-dimensional echocardiography by providing complementary information and improved quantitative accuracy and reproducibility compared with two-dimensional techniques. 3DE has the potential to become the standard echocardiographic examination procedure for the assessment of valvular disease. This article describes applications of 3DE.

Dynamic Change in Mitral Annular Area and Motion During Percutaneous Mitral Annuloplasty for Ischemic Mitral Regurgitation: Preliminary Animal Study With Real-time 3-Dimensional Echocardiography

We used a novel 3-dimensional (3D) echocardiographic technique to evaluate the impact of a coronary sinus-based percutaneous transvenous mitral annuloplasty (PTMA) on dynamic changes in mitral annular geometry and motion during the cardiac cycle in 8 sheep with ischemic mitral regurgitation. Using real-time 3D echocardiographic data before and after PTMA, 10 points along the saddle-shaped annulus were identified. For every 3D volume/frame during a cardiac cycle, we assessed mitral annular area and excursion defined as the traveling distance of the annular center. The PTMA device reduced both minimum and maximal mitral annular area (9.5 +/- 0.9-7.0 +/- 0.6 and 12.8 +/- 1.3-9.8 +/- 1.5 cm(2), P < .001 for both, respectively) with reduction of mitral regurgitation jet area (5.1 +/- 2.3-1.2 +/- 0.8 cm(2), P < .001), whereas it did not significantly impair mitral annular excursion amplitude (8.3 +/- 1.1-7.0 +/- 1.9 mm, P = .13). This 3D echocardiographic method noninvasively enabled dynamic study of mitral annular geometry and motion with quantitative analysis of the impact of PTMA.

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.

A critical analysis of minor cardiovascular criteria in the diagnostic evaluation of patients with Marfan syndrome

PURPOSE

The prevalence of most minor cardiovascular manifestations in Marfan syndrome (MFS) is unknown. We assessed the prevalence of minor cardiovascular manifestations in MFS to evaluate their usefulness in a diagnostic setting.

METHODS

Seventy-seven patients with MFS (aged 4 months to 55 years) underwent echocardiography to assess the presence of mitral valve prolapse and the diameter of the main pulmonary artery. A subset of 29 adult patients with MFS also underwent magnetic resonance imaging evaluation of the diameters of the thoracoabdominal aorta.

RESULTS

Mitral valve prolapse was encountered in 66% of patients with MFS, with an equal distribution of classic and nonclassic mitral valve prolapse. The main pulmonary artery diameter was significantly larger in patients with MFS at all ages when compared with controls. In the adult group (> or = 14 years), we were able to provide a cutoff value of 23 mm to define pulmonary artery dilatation. The descending aorta was enlarged, but with substantial overlap with controls, thus precluding the use of a cutoff value.

CONCLUSIONS

Mitral valve prolapse and main pulmonary artery dilatation are common findings in MFS patients at all ages and are easy to assess with echocardiography. Cutoff values to define dilatation of the descending aorta are hard to define, making them of limited value in the diagnostic evaluation. We recommend echocardiographic evaluation of mitral valve prolapse and main pulmonary artery diameter in patients referred for cardiovascular diagnostic assessment for MFS.

Usefulness of Live/Real Time Three-Dimensional Transthoracic Echocardiography in the Identification of Individual Segment/Scallop Prolapse of the Mitral Valve

In this report, we present 34 patients in whom surgical intervention was undertaken for severe mitral insufficiency due to mitral valve prolapse (MVP). Location and severity of MVP and regurgitation were assessed preoperatively by live/real time three-dimensional transthoracic echocardiography and closely agreed with the surgical findings.

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

Although three-dimensional (3D) echocardiography is still in its evolution, cutting edge advances that allow quantifiable images of cardiac structures to be created in real-time will begin to increase its use drastically. One of the most promising uses of the technology is in the planning, optimization, and postoperative surveillance of mitral valve repair techniques and devices. This article reviews the development of 3D echocardiography and presents illustrations of how it may be applied to improving mitral valve repair techniques. It is conceivable in the near future that mitral repair procedures will be designed and customized for each patient preoperatively using data obtained from 3D echo images and computerized virtual surgery techniques. Such tools will allow the surgeon to design operations that thoroughly analyze valve geometry and stress distribution before ever entering the operating room.

Three-dimensional tricuspid annular function provides insight into the mechanisms of tricuspid valve regurgitation in classic hypoplastic left heart syndrome

BACKGROUND

Tricuspid regurgitation (TR) has a negative impact on outcome in hypoplastic left heart syndrome (HLHS). There is a paucity of data assessing the mechanisms of TR. Lateral forces from the left ventricle play an important role in normal tricuspid valve (TV) function. This study evaluates the role of real-time 3-dimensional echocardiography in the assessment of the TV annulus and subvalvular apparatus in HLHS.

METHODS

In all, 31 real-time 3-dimensional echocardiographic studies from 26 patients (1 day-17 years old) with classic HLHS were included. In all, 7 studies were before and 8 were after first-stage palliation; 8 were postcavopulmonary shunt and 8 were post-Fontan. Only patients with severe left ventricular attenuation were included. Studies were subdivided into two groups: mild TR (N = 20) and severe TR (STR) (N = 11). Data from 17 control subjects were used for comparison. TV annular area, bending angle (saddle shape), and position of anterior papillary muscle were analyzed.

RESULTS

All annular segments moved in equally during systole in mild TR, whereas septal-lateral diameter contraction was significantly diminished in STR. TV annular area was larger in HLHS (mild TR, 1265 +/- 325; STR, 1767 +/- 450 mm2/m2) than in control subjects (762 +/- 85) (P < .001). However, area change was reduced only in STR (12.4 +/- 4.6% vs control subjects 20.4 +/- 8.3%, P < .05). Annular shape was flat during systole in HLHS. Anterior papillary muscle was laterally displaced in STR.

CONCLUSIONS

TV annular dynamics were different in patients with HLHS as a result of lack of interaction form left ventricle. Annular function, especially in septal-lateral direction, was further impaired in STR.

Autologous Myoblast Transplantation for Chronic Ischemic Mitral Regurgitation

OBJECTIVES

This study was designed to assess whether post-myocardial infarction (MI) in-scar transplantation of skeletal myoblasts (SM) could reduce chronic ischemic mitral regurgitation (MR) by decreasing left ventricular (LV) remodeling.

BACKGROUND

Extensive work has confirmed the relationship between ischemic MR and post-myocardial infarction (MI) remodeling of the LV.

METHODS

An infero-posterior MI was created in 13 sheep, thereby resulting in increasing MR. Two months post-MI, the animals were randomized and in-scar injected with expanded autologous SM (n = 6, mean: 251 x 10(6) cells) or culture medium only (n = 7). Three-dimensional echocardiography was performed at baseline, before transplantation, and for two months thereafter (sacrifice), with measurements of LV end-diastolic and end-systolic volumes (ESV), ejection fraction (EF), MR stroke volume, and leaflet tethering distance; wall motion score index (WMSi) was assessed by two-dimensional echo.

RESULTS

Measurements were similar between groups at baseline and before transplantation. At sacrifice, transplantation was found to have reduced MR progression (regurgitant volume change: -1.83 +/- 0.32 ml vs. 5.9 +/- 0.7 ml in control group, p < 0.0001) and tethering distance (-0.41 +/- 0.09 cm vs. 0.44 +/- 0.12 cm in control group, p < 0.001), with significant improvement of EF (2.01 +/- 0.94% vs. -4.86 +/- 2.23%, p = 0.02), WMSi (-0.25 +/- 0.11 vs. 0.13 +/- 0.03 in controls, p < 0.01) and a trend to a lesser increase in ESV (23.3 +/- 3.5 ml vs. 35.4 +/- 4.2 ml in control group, p = 0.055).

CONCLUSIONS

Autologous skeletal myoblast transplantation attenuates mild-to-moderate chronic ischemic MR, which otherwise is progressive, by decreasing tethering distance and improving EF and wall motion score, thereby enhancing valve coaptation. These data shed additional light on the mechanism by which skeletal myoblast transplantation may be cardioprotective.

Acute geometric changes of the mitral annulus after coronary occlusion: a real-time 3D echocardiographic study

We performed real-time 3D echocardiography in sixteen sheep to compare acute geometric changes in the mitral annulus after left anterior descending coronary artery (LAD, n=8) ligation and those after left circumflex coronary artery (LCX, n=8) ligation. The mitral regurgitation (MR) was quantified by regurgitant volume (RV) using the proximal isovelocity surface area method. The mitral annulus was reconstructed through the hinge points of the annulus traced on 9 rotational apical planes (angle increment=20 degrees). Mitral annular area (MAA) and the ratio of antero-posterior (AP) to commissure-commissure (CC) dimension of the annulus were calculated. Non-planar angle (NPA) representing non-planarity of the annulus was measured. After LCX occlusion, there were significant increases of the MAA during both early and late systole (p<0.01) with significant MR (RV: 30+/-14 mL), while there was neither a significant increase of MAA, nor a significant MR (RV: 4+/-5 mL) after LAD occlusion. AP/CC ratio (p<0.01) and NPA (p<0.01) also significantly increased after LCX occlusion during both early and late systole. The mitral annulus was significantly enlarged in the antero-posterior direction with significant decrease of non-planarity compared to LAD occlusion immediately after LCX occlusion.

Use of Real-time 3-dimensional Transthoracic Echocardiography in the Evaluation of Mitral Valve Disease

Three-dimensional (3D) echocardiography (3DE) provides unique orientations of the mitral valve (MV) not obtainable by routine 2-dimensional echocardiography. However, this modality has not been adopted in routine clinical practice because of its cumbersome and time-consuming process. The recent introduction of a full matrix-array transducer has enabled online real-time 3DE (RT3DE) and rendering. This study was designed to: (1) determine the clinical use of RT3DE in patients with MV pathology and in a control group selected for their good acoustic windows (protocol I); and (2) to investigate the feasibility of imaging the MV apparatus in a large group of consecutively imaged patients to determine the acoustic window or perspective from which the MV leaflets, commissures, and orifice are best visualized (protocol II). In protocol I, 65 patients were selected based on MV pathology and good 2-dimensional echocardiography image quality. Protocol II included 150 patients who were consecutively imaged using RT3DE. Images were viewed online (protocol I) and offline on a digital review station (protocol II). RT3DE visualization of the MV apparatus was graded based on the percentage of leaflet dropout and definition. In protocol I, 78% of patients had adequate 3D MV reconstructions with complete visualization of the anterior mitral leaflet (AML) in 84% versus the posterior mitral leaflet (PML) in 77%. The mitral leaflets, commissures, and MV orifice were well seen in 98%; however, the submitral apparatus was only observed in 76% of the patients. RT3DE: (1) correctly identified the prolapsed/flailed scallop in 6 of 8 patients; (2) obtained en face orientation of the MV orifice in 9 of 11 patients with mitral stenosis, allowing accurate measurements of the orifice area and evaluation of the immediate effects of balloon mitral valvuloplasty; and (3) allowed postoperative evaluation of MV repair and the integrity of the struts of a bioprosthetic leaflet. In protocol II, 70% of patients had adequate RT3DE with complete visualization of the AML noted in 55% versus 51% for PML. The mitral leaflets, commissures, and MV orifice were observed in 69%. Irrespective of acquisition window, the AML was best seen from a ventricular perspective. In contrast, the PML was optimally examined from a parasternal window. Both the medial and lateral commissures were equally assessed from either imaging window. In conclusion, RT3DE of the MV is feasible in a large majority of patients. Using different MV acquisitions RT3DE provides important clinical information such as: (1) identification of a prolapsed/flail scallop; (2) measurement of stenotic valve areas; (3) evaluation of MV leaflet integrity postrepair; and (4) identification of a MV perforation. In general the AML is better visualized than the PML. The parasternal window is the optimal approach to visualize both AML and PMLs.

Characterizing the normal heart using quantitative three-dimensional echocardiography

We present normative data on cardiac volume, geometry and shape derived using three-dimensional echocardiography (3-DE). Three-dimensional reconstructions were created using the piecewise smooth surface subdivision (PSSS) reconstruction technique of the left and right ventricular (LV and RV) endocardium and the mitral and tricuspid annuli (MA and TA) of 67 normal subjects. We derived LV end-diastolic (ED) and end-systolic (ES) volume indices (VI) of 76.5 +/- 16.8 ml m(-2) and 35.3 +/- 14.1 ml m(-2), LV ejection fraction (EF) of 56.1 +/- 9.93%, RV EDVI and ESVI of 93.2 +/- 20.0 ml m(-2) and 49.9 +/- 13.5 ml m(-2) and RVEF of 47.3 +/- 7.69%, along with data on the geometry and shape of the MA, TA, LV and RV. There was no pattern of consistent understatement or overstatement of volumes or dimensions compared with other imaging modalities, and observed variance in data can largely be accounted for through examination of the physics or protocol of each modality.

Mitral Annular Disjunction in Advanced Myxomatous Mitral Valve Disease: Echocardiographic Detection and Surgical Correction

Mitral annular disjunction is a structural abnormality of the mitral annulus fibrosus described by pathologists in association with mitral leaflet prolapse and defined as a separation between the atrial wall-mitral valve (MV) junction and the left ventricular attachment allowing for hypermobility of the MV apparatus. The transesophageal echocardiographic characteristics of this abnormality have not been previously described. In patients undergoing MV repair for myxomatous MV degeneration and evaluated using a standardized transesophageal echocardiographic protocol, annular disjunction (mean value 10 +/- 3 mm) was seen at the base of the posterior leaflet in 98% of patients with advanced, and in 9% of patients with mild/moderate MV degeneration. There was a significant correlation between the magnitude of disjunction and the number of segments with prolapse/flail (r = 0.397, P = .001). We found annular disjunction to be a common component of MV apparatus in advanced MV degeneration. Its recognition on transesophageal echocardiography is important to facilitate optimal MV repair. The modification of the repair technique allows surgical correction of the annular disjunction, which seems to optimize long-term results in these challenging cases.

Assessment of the tricuspid valve morphology by transthoracic real-time-3D-echocardiography

AIM

To demonstrate the feasibility of transthoracic three-dimensional real-time echocardiography (3D-TTE) supplemental to routine assessments of the tricuspid valve and to analyze interrater agreement.

METHODS

Twenty healthy subjects and 74 patients with right ventricular failure were examined with conventional 2D and additionally 3D-TTE (SONOS 7500, Philips, Netherlands). The 3D exams were performed and recorded by one of two raters. The recordings were evaluated offline and independently by both raters for visualization of morphological and functional features of the tricuspid valve according to a subjective 3-point scale. Statistical analyses were performed for interrater agreement and for comparison of imaging quality between the two study groups. In addition, we present an illustrative case report.

RESULTS

Visualization of the spatial relationship between the tricuspid valve and vicinal structures, of the commissures, the orifice, and entirety of valve depiction were better in the ventricular failure group as compared to the control group. Annular dimensions were equally assessable in both groups, leaflet thickness and mobility were not significantly different. Interrater agreement on assessability was slight for leaflet thickness, fair for leaflet mobility and orifice area, and good for the remaining features. The 3D-TTE exam including offline evaluation took 6.5 minutes on average and maximally 14 minutes.

CONCLUSION

3D-TTE of the tricuspid valve can be performed in addition to routine 2D echocardiography within a reasonable time and with high assessability of important features in patients with right ventricular failure. Interrater agreement was fair to good overall. Thus, its feasibility may encourage prospective studies on its potential for more detailed noninvasive diagnosis and preoperative planning.

Mitral valve prolapse

Mitral valve prolapse is a common valvular abnormality that is the most common cause of severe non-ischaemic mitral regurgitation in the USA. The overall prognosis of patients with mitral valve prolapse is excellent, but a small subset will develop serious complications, including infective endocarditis, sudden cardiac death, and severe mitral regurgitation. We present a comprehensive review of mitral valve prolapse, examining normal mitral anatomy, the clinical and echocardiographic features of mitral valve prolapse, and the pathophysiology and genetics of the disorder. We discuss the contemporary management of both asymptomatic and symptomatic prolapse, with particular attention to the timing and technique of surgical repair. We conclude that echocardiography is the method of choice for diagnosing mitral valve prolapse, that clinical and echocardiographic features can predict which patients with prolapse are at highest risk for complications, and that mitral valve repair is the treatment of choice for symptomatic prolapse.

The Dynamic Anterior Mitral Annulus

BACKGROUND

The anterior mitral annulus is considered a fixed structure. Recent data suggest otherwise. This study tested the hypothesis that the size of the anterior annulus varies with hemodynamic loading and ventricular contractility.

METHODS

Sonomicrometry array localization measured annular area, total annular circumference, anterior circumference, and posterior circumference in 6 sheep before and after neosynephrine increased systolic blood pressure by at least 150% during atrial pacing at 120 beats/min. In 6 additional animals the same dimensions were measured during atrial pacing (at 120 and 150 beats/min) and during isoproteronol infusions to increase heart rate to 120 and 150 beats/min.

RESULTS

Neosynephrine increased systolic total annular circumference from 99.7 +/- 5.5 mm to 106.9 +/- 9.6 mm. Anterior circumference increased from 40.8 +/- 4.0 mm to 45.3 +/- 5.7 mm whereas posterior circumference only increased from 59.0 +/- 5.5 mm to 61.6 +/- 7.0 mm. Low isoproteronol infusion decreased systolic total annular circumference from 107.5 +/- 8.3 mm to 101.9 +/- 10.6 mm. Most of this change occurred in the posterior circumference. Higher infusions of isoproteronol decreased total annular circumference from 106.8 +/- 8.3 mm to 98.3 +/- 9.7 mm. At this higher inotropic state the decrease in annular size was similar in the anterior and posterior annulus.

CONCLUSIONS

In sheep, the anterior annulus is a dynamic structure that varies in size in response to changes in hemodynamic loading and ventricular contractility.

Specific cardiac disorders in 402 consecutive patients with ischaemic cardioembolic stroke

BACKGROUND

To determine the cardiological substrate in acute stroke patients presenting with a cardioembolic stroke subtype.

METHODS

Data of 402 consecutive patients with cardioembolic stroke (cerebral infarction, n=347; transient ischaemic attack, n=55) were collected from a prospective hospital-based stroke registry in which data on 2000 stroke patients over a 10-year period were included. In all patients, specific cardiac disorders were identified by physical examination and results of electrocardiography and transthoracic echocardiography. Holter monitoring and more sensitive techniques of cardiac imaging were used in selected cases.

RESULTS

Cardioembolic cerebral ischaemia accounted for 20% of all acute strokes (25% of ischaemic cerebrovascular events). Cardiac sources of embolism included the following: (a) structural cardiac disorders associated with arrhythmia (n=232), the most frequent being left ventricular hypertrophic hypertensive disease (n=120) and rheumatic mitral valve disease (n=49); (b) structural cardiac disease with sustained sinus rhythm (n=81), the most frequent being systolic left ventricular dysfunction of both ischaemic (n=35) or non-ischaemic (n=24) aetiology; and (c) isolated atrial dysrhythmia (atrial fibrillation, n=88 and atrial flutter, n=1).

CONCLUSIONS

Hypertrophic hypertensive cardiac disease complicated with atrial fibrillation was the most frequent cardiac source of emboli in cardioembolic stroke. Other important cardiac sources were isolated atrial fibrillation, rheumatic mitral valve disease, and systolic left ventricular dysfunction of ischaemic and non-ischaemic cause. The incidence of traditional emboligenous-prone cardiac disorders, such as mitral valve prolapse and mitral annular calcification was low.

Fluid Mechanics of Heart Valves

Valvular heart disease is a life-threatening disease that afflicts millions of people worldwide and leads to approximately 250,000 valve repairs and/or replacements each year. Malfunction of a native valve impairs its efficient fluid mechanic/hemodynamic performance. Artificial heart valves have been used since 1960 to replace diseased native valves and have saved millions of lives. Unfortunately, despite four decades of use, these devices are less than ideal and lead to many complications. Many of these complications/problems are directly related to the fluid mechanics associated with the various mechanical and bioprosthetic valve designs. This review focuses on the state-of-the-art experimental and computational fluid mechanics of native and prosthetic heart valves in current clinical use. The fluid dynamic performance characteristics of caged-ball, tilting-disc, bileaflet mechanical valves and porcine and pericardial stented and nonstented bioprostheic valves are reviewed. Other issues related to heart valve performance, such as biomaterials, solid mechanics, tissue mechanics, and durability, are not addressed in this review.

Three-dimensional echocardiography for planning of mitral valve surgery: Current applicability?

BACKGROUND

Two-dimensional transesophageal echocardiographic (2D TEE) assessment of the mitral valve requires mental integration of a limited number of 2D imaging planes. Structural display in three dimensions from any perspective may be of advantage to the surgeon for better judgment and planning.

METHODS

Feasibility, accuracy, and limitations of preoperative three-dimensional transesophageal echocardiography (3D TEE) was assessed in 51 patients with mitral valve disease. The width of the anterior mitral valve was measured with either method and compared with the operative finding. Three-dimensional dynamic sequences of the reconstructed mitral valve were shown preoperatively to the surgeon and later compared with the intraoperative finding.

RESULTS

The quality of the 3D reconstruction was graded as good in 25 patients (49.0%), fair in 16 patients (31.4%), and poor in 10 patients (19.6%) where atrial fibrillation did not allow ECG gating. Thirty-nine patients had successful mitral valve repair and twelve patients required valve replacement. Based on intraoperative findings, sensitivity for the diagnosis of mitral valve prolapse using 2D TEE and 3D TEE was 97.7% and 92.9% (p = ns) respectively and specificity was 100% by both methods. Sensitivity for the diagnosis of rupture of chordae tendineae using 2D TEE and 3D TEE was 92.3% and 30.8% respectively (p < 0.05) and specificity was 100% by both methods.

CONCLUSIONS

Dynamic 3D echocardiography is feasible and can provide good insight into valvular motion and allows adequate preoperative planning when reconstruction is being considered. However dynamic 3D reconstruction is currently limited by the quality of the original 2D echo cross sectional images which can be adversely affected by minimal patient movements, breathing, or cardiac arrhythmia, thus limiting accuracy of the 3D TEE significantly compared with 2D TEE.

The effect of regional ischemia on mitral valve annular saddle shape

BACKGROUND

The mitral valve annulus has a distinctive saddle shape. Recent finite element analysis indicates this shape may contribute to normal valve function by increasing leaflet curvature and reducing leaflet stress. This study tests the hypothesis that acute ischemic mitral regurgitation (AIMR) is associated with loss of annular saddle shape.

METHODS

Sonomicrometry array localization (SAL) measured the three-dimensional geometry of the mitral annulus in 6 sheep before and after 30 min of posterior ischemia that produced severe AIMR. Using this SAL data the annular height to commissural width ratio (AHCWR), a measure of annular saddle shape, was calculated throughout the cardiac cycle and reported as a percentage.

RESULTS

The normal mitral annulus accentuated its saddle shape rapidly during isovolemic contraction: AHCWR increased from 11.6% +/- 1.1%-13.9% +/- 1.6% (p < 0.001). During ejection AHCWR remained relatively constant ranging from a minimum of 14.1% +/- 1.5% to a maximum of 14.9% +/- 1.3%. During ischemia AHCWR was found to be significantly smaller (p < 0.05) during isovolemic contraction, ejection, and isovolemic relaxation, but not during diastolic filling. Whereas ischemia did not affect AHCWR at end diastole (11.6% +/- 2.8%), the isovolemic accentuation of the saddle shape was lost.

CONCLUSIONS

The normal mitral annulus accentuates its saddle shape during systole. This accentuation is eliminated during ischemia that causes AIMR. These data suggest an association between annular saddle shape and valve competency.