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European Journal of Echocardiography Advance Access published online on May 13, 2008
European Journal of Echocardiography, doi:10.1093/ejechocard/jen165
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Published on behalf of the European Society of Cardiology. All rights reserved. © The Author 2008. For permissions please email: journals.permissions@oxfordjournals.org

Mechanisms of valve competency after mitral valve annuloplasty for ischaemic mitral regurgitation using the Geoform ring: insights from three-dimensional echocardiography

Todd A. Armen1, Rashmi Vandse1,*, Juan A. Crestanello2, Subha V. Raman3, Katherine M. Bickle1 and Nadia S. Nathan1

1 Department of Anesthesiology, Ohio State University Medical Center, N-416 Doan Hall, 410 W 10th Avenue, Columbus, OH 43210, USA
2 Division of Cardiothoracic Surgery, Ohio State University Medical Center, Columbus, OH 43210, USA
3 Division of Cardiovascular Medicine, Ohio State University Medical Center, Columbus, OH 43210, USA

Received 21 October 2007; accepted after revision 20 April 2008.

* Corresponding author. Tel: +1 610 996 5345/+1 614 293 7277. E-mail address: rashmi_vandse{at}yahoo.com


   Abstract
Top
 Abstract
Introduction
 Methods
 Results
 Discussion
 Limitations
 Conclusion
 References
 
Aims: Left ventricular remodelling leads to functional mitral regurgitation resulting from annular dilatation, leaflet tethering, tenting, and decreased leaflet coaptation. Mitral valve annuloplasty restores valve competency, improving the patient’s functional status and ventricular function. This study was designed to evaluate the mechanisms underlying mitral valve competency after the implantation of a Geoform® annuloplasty ring using three-dimensional (3D) echocardiography.

Methods and results: Seven patients (mean age of 65 years) with ischaemic mitral regurgitation underwent mitral valve annuloplasty with the Geoform ring and coronary artery bypass surgery. Pre- and post-operative 3D echocardiograms were performed. Following mitral annuloplasty, mitral regurgitation decreased from 3.4 ± 0.2 to 0.9 ± 0.3 (P-value < 0.0001), mitral valve tenting volume from 13 ± 1.7 to 3.2 ± 0.3 mL (P-value < 0.001), annulus area from 12.6 ± 1.0 to 3.3 ± 0.2 cm2 (P-value < 0.0001), valve circumference from 13 ± 0.5 to 7.3 ± 0.3 cm (P-value < 0.0001), septolateral distance from 2.1 ± 0.1 to 1.4 ± 0.06 cm (P-value < 0.01) and intercommissural distance from 3.4 ± 0.1 to 2.7 ± 0.03 cm (P-value < 0.03). There was significant decrease in the septolateral distance at the level of A2–P2 with respect to other regions. These geometric changes were associated with the improvement in the NYHA class from 3.1 ± 0.3 to 1.3 ± 0.3 (P-value < 0.002).

Conclusion: The mitral valve annuloplasty with the Geoform® ring restores leaflet coaptation and eliminates mitral regurgitation by effectively modifying the mitral annular geometry.

Keywords: Annuloplasty; Ischaemic mitral regurgitation; Mitral valve; Mitral valve tenting; Three-dimensional echocardiography


   Introduction
Top
 Abstract
 Introduction
Methods
 Results
 Discussion
 Limitations
 Conclusion
 References
 
Ischaemic mitral regurgitation (IMR) often complicates coronary artery disease and has a negative impact on patient’s survival and quality of life.1–4 It is not an intrinsic disease of the mitral valve but several changes on the left ventricular (LV) anatomy and pathophysiology play a role in the genesis of IMR.5–15

Myocardial ischaemia leads to remodelling of the LV resulting in a series of changes including increased sphericity index,5–6 mitral annular dilatation,7–8 outward displacement of the papillary muscles with the subsequent tethering and tenting of the mitral leaflets into the LV.9–12 In the setting of LV systolic dysfunction, there is also reduction in the force available to close the leaflets in opposition to the increased tethering which further complicates the mitral regurgitation (MR).13–15 Mitral regurgitation in turn leads to LV volume overload, with further progression of annular dilation, LV remodelling, increase in the severity of mitral regurgitation and more severe symptoms of congestive heart failure.

One of the accepted therapeutic approaches for IMR is mitral valve annuloplasty using various commercially available annuloplasty rings.16–27 The Geoform® ring (Edwards Lifesciences, Irvine, CA, USA) is a recently introduced mitral valve annuloplasty ring. It is designed to reduce the antero-posterior diameter of the mitral annulus. It has an accentuated posterior hump which elevates the P2 to pull the posterior leaflet and lateral ventricular wall upward and inward (towards A2), to enhance A2–P2 coaptation (Figures 1 and 2). The mechanism by which the ring eliminates mitral regurgitation and its effect on the three-dimensional (3D) anatomy and function of the mitral valve are not clearly demonstrated in clinical studies. The goal of this study was to analyse the changes in mitral valve anatomy following the implantation of the Geoform® annuloplasty ring and to evaluate which of them is responsible for valve competency.


Figure 1
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  		Figure 1 Oblique view of the Geoform mitral annuloplasty ring. Note the accentuated posterior hump, which elevates the P2 and raises the mitral valve apparatus to counteract the downward pull of the enlarged left ventricle. Reproduced with permission from Edwards Lifesciences, Irvine, California.

 


Figure 2
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  		Figure 2 Superior view of the Geoform mitral annuloplasty ring. Note the reduced antero-posterior diameter, which brings the annulus inward to offset the outward pull of the enlarged left ventricle. This restores the leaflet coaptation without compromising the orifice area. Reproduced with permission from Edwards Lifesciences, Irvine, California.

 

   Methods
Top
 Abstract
 Introduction
 Methods
Results
 Discussion
 Limitations
 Conclusion
 References
 
Patient selection criteria
This study included seven patients with IMR who underwent mitral valve repair with a Geoform ring® and coronary bypass surgery at The Ohio State University Medical Center from November 2005 to June 2006. Pre-operative and post-operative clinical case histories, operative notes, anaesthesia records and laboratory investigation were reviewed. Follow-up data were collected from clinical records and from patients visit records.

Pre-operative and intraoperative patient’s characteristics are displayed in Table 1.


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  		Table 1 Pre-operative and intraoperative patient characteristics

 
All patients underwent pre- and post-operative echocardiographic evaluation.

Informed consent was taken from all patients included in this study and the study was approved by the Office of Responsible Research Practices of The Ohio State University.

Echocardiographic analysis
Transthoracic followed by transoesophageal echocardiography (TEE) was performed both pre- and post-operatively by an experienced echocardiographer by multiplane TEE probe using Sonos® 7500 (Philips Medical Systems, N.A, Bothel, WA, USA). The 3D processing was performed with 4D Cardio-view®1.3 (TomTec Imaging Systems, Munich, Germany). The 3D LV model was generated. It produced a shell reconstruction of the LV allowing calculation of total and segmental LV volumes during the cardiac cycle. The end-systole frame was determined as frame with a closed aortic valve just prior to the opening of the mitral valve. This time point was used to make all valve measurements. Frame by frame analysis yielded the valvular area, circumference, commissure-to-commissure diameter (c–c diameter) and anterior–posterior diameter (a–p diameter) (Figures 3 and 4). From this, the tenting volume (TnV) (defined as the volume in mL, from the plane of the mitral valve annulus to the leaflet coaptation line) was reconstructed in 3D and TnV calculated from the 2D labelling (Figures 5 and 6).


Figure 3
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  		Figure 3 Pre-operative three-dimensional reconstruction showing mitral valve area, mitral valve circumference, mitral valve septolateral dimension (a–p diameter) and commissure-to-commissure (c–c) dimension.

 


Figure 4
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  		Figure 4 Post-operative three-dimensional reconstruction of the same patient showing mitral valve area, mitral valve circumference, mitral valve septolateral dimension (a–p diameter) and commissure-to-commissure (c–c) dimension. Note the obvious decrement in all dimensions compared with pre-operative.

 


Figure 5
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  		Figure 5 Pre-operative three-dimensional reconstruction showing mitral valve tenting volume.

 


Figure 6
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  		Figure 6 Post-operative three-dimensional reconstruction of the same patient showing mitral valve tenting volume. Note the obvious decrement in all dimensions compared with pre-operative.

 
LV end-diastolic and end-systolic volumes were measured by the biplane Simpson’s method. Ejection fraction (percent) was calculated by the equation: 100 x (end-diastolic volume–end-systolic volume)/end-diastolic volume. MR was evaluated by colour Doppler echocardiography and graded as follows: Mild (1+), Moderate (2+), Moderately severe (3+), and Severe (4+).

Statistics
All continuous data were presented as mean ± SEM. Statistical analysis was performed using SPSS version 16.0 (SPSS, Inc., Chicago, IL, USA). The comparison between the pre- and post-operative data were made by paired, two-tailed Student’s t-test. A P-value < 0.05 was considered statistically significant.


   Results
Top
 Abstract
 Introduction
 Methods
 Results
Discussion
 Limitations
 Conclusion
 References
 
Clinical characteristics
There was no post-operative mortality. Median length of hospital stay was 13 ± 6 days (range 6–25 days). Follow-up was complete in all patients. At a mean follow-up of 45.29 days the mean NYHA functional class was significantly reduced to 1.29 ± 0.18 (P < 0.002) compared with pre-operative value. Five patients were in class I and two patients were in class II.

Quantitative echocardiography and changes in three-dimensional mitral valve geometry
Changes in LV function, mitral valvular and LV dimensions, and severity of mitral regurgitation associated with the implantation of the Geoform mitral annuloplasty ring are displayed in Tables 2 and 3.


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  		Table 2 Pre- and post-operative echocardiographic characteristics and three-dimensional mitral valve assessment following annuloplasty

 


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  		Table 3 Three-dimensional assessment of the septolateral distances (cm) of the mitral valve annulus at level of A3–P3, A2–P2, and A1–P1 before and after the annuloplasty

 
Mitral annuloplasty improved LV function, decreased LV volume and significantly diminished mitral regurgitation, which was associated with the decrease in mitral valve TnV, annulus area, and circumference. The intercommissural distance decreased by 20% whereas the septolateral distance decreased by 38% following annuloplasty. The maximum reduction in the diameter occurred at the level of A2–P2 with respect to A1–P1 and A3–P3. The tethering of the mitral leaflets into the LV also disappeared after annuloplasty.


   Discussion
Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
Limitations
 Conclusion
 References
 
This study shows that Geoform® annuloplasty abolishes IMR by improving the mitral leaflet coaptation which results from decrease in the mitral valve TnV, annulus area, and a more selective reduction in the septolateral distance compared with intercommissural distance.

IMR continues to be a complex surgical problem for which a reproducible and reliable surgical correction is yet to be found. There is a wide variation in the clinical spectrum of IMR due to varying location and chronicity of ischaemia and anomalies in annular and ventricular remodelling.28,29 As a result, there is a lack of consensus in treating these patients. Bolling and co-workers16,17 have initially demonstrated the feasibility of restrictive mitral valve annuloplasty in patients with end-stage ischaemic and non-ischaemic dilated cardiomyopathy. It increased the coaptating surface of the leaflets, thus abolished mitral regurgitation in patients with end-stage heart failure improving the patient’s functional status and LV function.18–24 However, recent studies have demonstrated that MR often persists or recurs even after ring annuloplasty. This could be due to the fact that annuloplasty does not sufficiently address the tethering of the leaflets by the remodelled ventricle.30–34 This has led to the development of new strategies for the treatment of IMR.35 Even different types of annuloplasty rings have been devised aiming at more physiologic repair.20,25–27

The Geoform® ring (Edwards Lifesciences, Irvine, CA, USA) is a recently introduced functional mitral regurgitation (FMR)-specific prosthesis (Figures 1 and 2). The finite element study, comparing the Geoform® ring with the conventional physio-annuloplasty ring has shown Geoform® ring to be more efficacious in restoring the valve competency in the presence of considerable degrees of leaflet tethering. Both the rings had the comparable intercommissural dimension but the anterior–posterior dimension of the Geoform® ring was 41% less when compared with the same-sized Physio-annuloplasty ring. Thus achieving the leaflet coaptation with the same effective orifice area and avoiding the need for aggressive undersizing.36

During the past decade, both laboratory and clinical studies using several different imaging modalities have linked various geometric deformations to the severity of IMR6–15 and have discovered various indexes of annular and subvalvular remodelling.37–41

Song et al.40 dealing with this subject of IMR compared the patients with IMR and normal mitral valves and they concluded that TnV derived from the real time 3D echocardiography to be a superior index of mitral valve tethering in functional MR compared with tenting area (TnA) that is dependent on the location of 2D planes.

Watanabe and co-workers41–44 using real time 3D echocardiography compared transthoracic volumetric images of 12 patients with IMR and 10 controls. In IMR, the annulus was flattened with apparent tenting of the leaflets. Maximum and mean tenting length was longer and TnV was larger in IMR compared with control subjects. Even though the maximum tenting site was located in the anterior leaflet in all patients the exact location was not the same in all patients with IMR, highlighting the significance of 3D evaluation of mitral valve tenting. There was also significant geometric heterogeneity of mitral leaflet tenting, the mitral valve leaflets in inferior infarction showed localized tenting, in contrast with anterior infarction showing wide tethering and bulging towards LV. Same group analysed the geometric change in the mitral leaflets and annulus following reconstructive surgery for IMR in three of their patients by 3D echocardiography. MR disappeared in all three patients following surgery and there was significant reduction in the LV volume, mitral leaflet TnV and mitral annulus size.

Encouraged by the results of these previous studies emphasizing the importance of mitral valve tethering in IMR, we undertook this study to assess the geometric impact of Geoform ring annuloplasty by 3D echocardiography. Our results are in accordance with Watanabe and co-workers.44 The severity of MR decreased from 3.4 ± 0.2 to 0.9 ± 0.3 following annuloplasty along with the significant improvement in the patient’s functional status. In terms of mitral valvular geometry, there was significant reduction in the mitral valve TnV, valve area, valve circumference, septolateral and intercommissural distances. The intercommissural distance decreased by 20% whereas the septolateral distance decreased by 38% following annuloplasty which emphasizes the unique feature of the Geoform ring®. Comparison of the pre- and post-operative septolateral distances at three different segments, showed significant reduction in the diameter at the level of A2–P2 with respect to other regions thus illustrating the effect of a shaped ring. Although, not reaching statistical significance, there was also some increase in the LVEF (LV ejection fraction) and reduction in the LVESVI (LV end-systolic volume index) post-operatively.

The 2D echocardiography has been used for assessing the various geometric deformations associated with IMR and in quantifying the indexes of leaflet tethering such as mitral valve TnA and mitral valve tenting height.37–39 However, the validity of single plane based 2D measurement of leaflet tenting is shown to be potentially inaccurate and inconsistent because of asymmetric leaflet tethering whose magnitude and pattern varies with the infarct territory.40–41 The precise and comprehensive assessment of the 3D geometry of the mitral valve and ventricle will enhance our knowledge of the anatomical and functional aspects of IMR and would provide a more rational basis in designing the optimal annuloplasty ring aiming at a more physiological repair. Previous studies have shown that annuloplasty alone does not always guarantee successful and durable elimination of IMR.30–34 Therefore, it is important to ensure whether this favourable modification in the LV and mitral valvular geometry by the surgical annuloplasty will have long lasting effects. These 3D changes in the geometry can be used as an index for the long-term follow-up of patients following annuloplasty and may be used to detect the efficacy of annuloplasty (Geoform) rings in maintaining the mitral valve competence.


   Limitations
Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 Limitations
Conclusion
 References
 
There was a small study population and limited period of follow-up. Hence, these data have to be considered as preliminary results and need to be confirmed by long-term follow-up of greater number of patients.


   Conclusion
Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 Limitations
 Conclusion
References
 
This study provides a novel insight into the alteration in the mitral annular geometry following the implantation of Geoform® annuloplasty ring in patients with IMR with the aid of 3D echocardiography. The Geoform® ring by virtue of its unique 3D shape, improves leaflet coaptation and significantly decreases IMR in the presence of considerable leaflet tethering. Our results emphasize the importance of relieving the mitral valve tethering in decreasing the IMR as shown by significant reduction in the post-operative mitral valve TnV. The more selective reduction in the septolateral distance when compared with intercommissural distance achieves effective leaflet coaptation without compromising the transmitral flow which confirms the fact that Geoform ring is not undersized on implantation.

Conflict of interest: none declared.


   References
Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 Limitations
 Conclusion
 References
 

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