Mitral Valve Tenting Index for Assessment of Subvalvular Remodeling

doi:10.1016/j.athoracsur.2007.05.005

The Annals of Thoracic Surgery

Volume 84, Issue 4, October 2007, Pages 1243-1249

https://doi.org/10.1016/j.athoracsur.2007.05.005 Get rights and content

Background

Ischemic mitral regurgitation results from a variable combination of annular dilatation and remodeling of the subvalvular apparatus. Current surgical techniques effectively treat annular dilatation, but methods for addressing subvalvular remodeling have not been standardized. An effective technique for determining the extent of subvalvular remodeling could improve surgical results by identifying patients who are unlikely to benefit from annuloplasty alone.

Methods

A well-characterized ovine model of ischemic mitral regurgitation was used. Real-time three-dimensional echocardiography was performed on each animal at baseline and at 1 hour and 8 weeks after infarction. Multiple valvular geometric measurements were calculated at each time point.

Results

Immediate and long-term changes in mitral valvular geometry were observed. Annular height–to–commissural width ratio decreased from 20.0% ± 1.6% to 11.2% ± 0.9% 1 hour after infarction (p < 0.001) and to 9.4% ± 0.4% 8 weeks after infarction (p < 0.001), whereas mitral annular area increased from 8.1 ± 0.3 cm² to 9.2 ± 0.4 cm² (p < 0.05) and then to 10.5 ± 0.6 cm² (p < 0.05). Maximum mitral valve tenting area increased from 49.7 ± 5.1 mm² to 58.6 ± 4.2 mm² (p < 0.05) and then to 106.4 ± 3.9 mm² (p < 0.001), whereas mitral valve tenting volume increased from 679.0 ± 75.5 mm³ to 828.6 ± 102.4 mm³ (p = 0.050) and then to 1530.5 ± 97.8 mm³ (p < 0.001). The mitral valve tenting index increased from 0.83 ± 0.08 mm to 0.88 ± 0.08 mm (p > 0.05) and then to 1.46 ± 0.08 mm (p < 0.001).

Conclusions

We have described a technique that uses real-time three-dimensional echocardiography to perform a comprehensive assessment of leaflet tethering on the entire mitral valve. Our methodology is not influenced by viewing plane selection, regional tenting asymmetry, or annular dilatation and therefore represents a potentially useful, clinically relevant, and consistent measure of subvalvular remodeling.

Section snippets

Surgical Protocol

The study protocol was reviewed and approved by the University of Pennsylvania School of Medicine Institutional Animal Care and Use Committee (IACUC) and was in compliance with guidelines for humane care (National Institutes of Health Publication No. 85-23, revised 1996).

Ten sheep were pretreated with buprenorphine (2 μg/kg) and then induced with intravenous (IV) sodium thiopental (10 to 15 mg/kg), intubated, and anesthetized with isoflurane (1.5% to 2.0%) and oxygen (Narkomed, North American

Results

To ensure that mitral leaflet loading conditions, which influence annular geometry [17], were similar at each data acquisition point, statistical comparisons were performed for all hemodynamic indicators at each data acquisition point and are summarized in Table 1. No statistically significant differences were found between time points for any indicator; therefore, leaflet loading conditions were likely similar at all data acquisition points. None of the animals had significant MR at baseline.

Comment

More than 5 million Americans have heart failure, up to 40% of these patients exhibit some degree of MR, and in 300,000 the MR is severe [18]. The negative impact of IMR on survival has been well documented, and a graded relationship between the severity of MR and mortality has been repeatedly demonstrated [18, 19].

During the past decade, an increasingly aggressive surgical approach to IMR has developed. Mitral ring annuloplasty, with or without coronary revascularization, has become the

Acknowledgment

This research was supported by National Institutes of Health grants HL63954 (RCG), HL73021 and HL76560 (JHG) and by American Heart Association Post-Doctoral Fellowship 0625455U (LPR).

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Citation Excerpt :
2) Leaflet size was measured by ML(area) as exposed total mitral leaflet (ML) area, AML(area) as total AML area including coapting leaflet area, PML(area) as total PML area, PML/AML(area) as the ratio of PML(area) to AML(area), PML/ML(area) as the ratio of PML(area) to ML(area), and AML/ML(area) as the ratio of AML(area) to ML(area). ( 3) Degree of tenting was determined by tenting(vol) as ML tenting volume, tenting index as the ratio of total ML area (ML(area)) to mitral annular area (annulus(area))—this index being similarly used in earlier studies27—and angle(APML) as the anterior to posterior ML angle. ( 4) Degree of prolapse was measured by prolapse(vol) as the volume of ML prolapse.
MitraClip implantation has become the standard transcatheter mitral valve repair (TMVR) technique for severe mitral regurgitation (MR). However, approximately one third of patients have poor outcomes, with MR recurrence at follow-up. The aim of this study was to investigate whether quantitative analysis of mitral valve (MV) geometry on three-dimensional (3D) echocardiography can identify geometric parameters associated with the recurrence of severe functional MR (FMR) versus organic MR (OMR) at 6-month follow-up after TMVR using the MitraClip.
Sixty-one patients with severe FMR (n = 45) or OMR (n = 16) who underwent transesophageal 3D echocardiography before and 6 months after TMVR were retrospectively analyzed. MV geometry was quantified using 3D echocardiography software. Vena contracta area (VCA) at 6-month follow-up was used to define two outcome groups: patients with good results with VCA < 0.6 cm² (MR < 0.6) and those with MR recurrence with VCA ≥ 0.6 cm² (MR ≥ 0.6).
MR recurrence was found in 34% of all study patients (21 of 61). In patients with FMR, significant differences between MR < 0.6 and MR ≥ 0.6 were found at baseline for tenting index (1.13 vs 1.23, P = .004), tenting volume (2.8 vs 4.0 ml, P = .04), indexed left ventricular (LV) end-diastolic volume (68.0 vs 99.9 ml/m², P = .001), and VCA (0.71 vs 1.00 cm², P = .003); no significant parameters of MR recurrence were found in patients with OMR. Multivariate analysis identified indexed LV end-diastolic volume as the strongest independent determinant of MR recurrence. Receiver operating characteristic analysis identified a tenting index of 1.185 (area under the curve 0.79) and indexed LV end-diastolic volume of 88 ml/m² (area under the curve 0.76) to best discriminate between MR < 0.6 and MR ≥ 0.6.
MR recurrence after TMVR in patients with FMR is associated with advanced LV dilation and MV tenting before TMVR, which provides clinical implications for a point of no return beyond which progressive LV dilation with MV geometry dilation and tethering cannot be effectively prevented by TMVR. In contrast, no significant determinants of MR recurrence and progressive MV annular dilation could be identified in patients with OMR.
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In contrast, the majority of patients with MFS had billow, and many had significant amounts of billow exceeding the total tenting volume of the valve. Valve tenting orients the leaflets to better handle the systemic load imposed by ventricular contraction, and in prior work tenting metrics have been identified as important in prediction of adult MR.30-33 Tenting height, area, and volume were all lower in our patients with MFS compared with normal control subjects. We sought to establish a relationship between 3D structural characteristics and valve function in this patient cohort.
Mitral valve (MV) prolapse is common in children with Marfan syndrome (MFS) and is associated with varying degrees of mitral regurgitation (MR). However, the three-dimensional (3D) morphology of the MV in children with MFS and its relation to the degree of MR are not known. The goals of this study were to describe the 3D morphology of the MV in children with MFS and to compare it to that in normal children.
Three-dimensional transthoracic echocardiography was performed in 27 patients (3–21 years of age) meeting the revised Ghent criteria for MFS and 27 normal children matched by age (±1 year). The 3D geometry of the MV apparatus in midsystole was measured, and its association with clinical and two-dimensional echocardiographic parameters was examined.
Compared with age-matched control subjects, children with MFS had larger 3D annular areas (P < .02), smaller annular height/commissural width ratios (P < .001), greater billow volumes (P < .001), and smaller tenting heights, areas, and volumes (P < .001 for all). In multivariate modeling, larger leaflet billow volume in MFS was strongly associated with moderate or greater MR (P < .01). Intra- and interuser variability of 3D metrics was acceptable.
Children with MFS have flatter and more dilated MV annuli, greater billow volumes, and smaller tenting heights compared with normal control subjects. Larger billow volume is associated with MR. Three-dimensional MV quantification may contribute to the identification of patients with MFS and other connective tissue disorders. Further study of 3D MV geometry and its relation to the clinical progression of MV disease is warranted in this vulnerable population.
Semi-automated Segmentation and Quantification of Mitral Annulus and Leaflets from Transesophageal 3-D Echocardiographic Images
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In the DCM patient, as expected, the MV was deformed as a result of LV dilation, thus increasing MA and ML dimensions compared with normal valves (Table 4, third column). The reported tenting distribution as well as the increased leaflet thickness (Fig. 11) are consistent with previous studies (Chaput et al. 2008; Watanabe et al. 2005; Ryan et al. 2007), thus suggesting active adaptation process at cellular matrix level resulting in thicker anterior and posterior leaflets. In the MVR patient, the MA segmentation correctly delineated the annulus, even in presence of the implanted ring (Fig. 11).
Quantification of three-dimensional (3-D) morphology of the mitral valve (MV) using real-time 3-D transesophageal echocardiography (RT3-D TEE) has proved to be a valuable tool for the assessment of MV pathologies, but of limited use in clinical practice because it relies on user-intensive approaches. This study presents a new algorithm for the segmentation and morphologic quantification of the mitral annulus (MA) and mitral leaflets (ML) in closed valve configuration from RT3-D TEE volumes. Following initialization, the MA and the ML and the coaptation line (CL) are automatically obtained in 3-D. Validation with manual tracings was performed on 33 patients, resulting in segmentation errors in the order of 0.7 mm and 0.6 mm for the MA and ML segmentation, in addition to good intra- and inter-observer reproducibility (coefficients of variation below 12% and 15%, respectively). The ability of the algorithm to assess different MV pathologies as well as repaired valves with implanted annular rings was also explored. The reported performance of the proposed fast, semi-automated MA and ML quantification makes it promising for future applications in clinical settings such as the operating room, where obtaining results in short time is important.
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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.
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.
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.
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Original articleCardiovascularMitral Valve Tenting Index for Assessment of Subvalvular Remodeling

Background

Methods

Results

Conclusions

Section snippets

Surgical Protocol

Results

Comment

Acknowledgment

Am J Cardiol

Ann Thorac Surg

Ann Thorac Surg

J Am Coll Cardiol

Ann Thorac Surg

J Am Soc Echo

J Am Coll Cardiol

J Am Coll Cardiol

Ann Thorac Surg

Am J Cardiol

Ann Thorac Surg

Semin Thorac Cardiovasc Surg

J Thorac Cardiovasc Surg

Semin Thorac Cardiovasc Surg

Ann Thorac Surg

Original article
Cardiovascular
Mitral Valve Tenting Index for Assessment of Subvalvular Remodeling